This article was downloaded by: [Adelphi University]On: 11 November 2014, At: 08:20Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office:Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

New Zealand Journal of AgriculturalResearchPublication details, including instructions for authors and subscriptioninformation:http://www.tandfonline.com/loi/tnza20

Silage and dairy cow productionG. L. Rogers a b , A. M. Bryant a , K. E. Jury a & J. B. Hutton aa Ministry of Agriculture and Fisheries , Ruakura Agricultural ResearchCentre , P.B., Hamilton, New Zealandb Dairy Research Institute (Ellin-bank) , Warragul, Victoria, AustraliaPhone: 3820Published online: 21 Dec 2011.

To cite this article: G. L. Rogers , A. M. Bryant , K. E. Jury & J. B. Hutton (1979) Silage anddairy cow production, New Zealand Journal of Agricultural Research, 22:4, 511-522, DOI:10.1080/00288233.1979.10417818

To link to this article: http://dx.doi.org/10.1080/00288233.1979.10417818

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis, ouragents, and our licensors make no representations or warranties whatsoever as to theaccuracy, completeness, or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, and are not the viewsof or endorsed by Taylor & Francis. The accuracy of the Content should not be relied uponand should be independently verified with primary sources of information. Taylor and Francisshall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses,damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly inconnection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantialor systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, ordistribution in any form to anyone is expressly forbidden. Terms & Conditions of access anduse can be found at http://www.tandfonline.com/page/terms-and-conditions

N.Z. Journal of Agricultural Research 22 (1979): 511-22

Silage and dairy cow production I. Digestible energy intake and yield and composition of milk of

cows fed pasture and pasture silages

G. L. ROGERS", A. M. BRYA~IT, K E. JURY, AND J. B. HUTTON

Ruakura Agricultural Research Centre, Ministry of Agriculture and Fisheries, P.B., Hamilton, New Zealand

In two experiments with Tersey cross-bred dairy cows, pasture and unwilted silage, and unwilted, wilted, and forma~dehyde-treated silages, fed as sale rations, ''v'ere compared. In both experiments level of feeding and diet significantly affected milk production and composition. In the first experiment voluntary intake of silage was 32% lower than that of pasture, and silage feeding lowered milk yields and fat and protein contents of milk. Regression analyses of data obtained when different levels of feeding were applied indicated that differences in milk yield and composition persisted when the diets were compared at the same digestible energy intake. Also, pasture-fed cows lost more body weight than those fed silage. In the second experiment, by comparison with unwilted silage, formaldehyde-treated silage increased milk fat content and yields of milk and fat. Wilting also produced relative increases in yields of milk and its components. Differences between diets in the pattern of rumen fermentation were small and not considered to influence milk yield and composition. However, lower levels of soluble carbohydrate and higher levels of soluble non-protein N, each affecting the efficiency of rumen microbial synthesis and consequently the amount of available dietary protein,. could have been responsible. The possible mechanisms account-ing for different responses between silages are also discussed.

511

INTRODUCTION

By contrast with mixed concentrate-roughage rations, there is limited information on the separate effects of diet and level of feeding on yield and composition of milk when roughage is the sole feedstuff. This deficiency is becoming increasingly significant as changes in the relative economic value of individual milk constituents alter quite appreciably financial returns on unit volume of milk. Reducing the level of pasture offered to cows by increasing grazing intensities has been shown to lower milk yields and milk protein contents, and to increase milk fat contents (Hutton 1973, 1975). The lowered yields of milk and fat, and reduced contents of solids-not-fat from cows fed pasture silage compared with pasture have been attributed generally to lowered voluntary intake (Wallace & Parker 1966; Hutton et al. 1971; Lancaster et al. 1974). How-ever, when Fisher et al. (975) restricted intake

of a 1: 1 silage and pasture ration to 50% of appetite, cows produced milk of unchanged com-position, though in much smaller amounts. Further, Hutton (975) found that when the pro-portion of silage fed with pasture to groups of cows was increased from 1f3 to 2;3 of the ration, both milk yield and milk protein content decreased, even though average dry matter intakes were similar.

" Present address: Dairy Research Institute (Ellin-bank), Warragu1, Victoria, 3820. Australia.

Received 19 April 1979

The chemical characteristics of silage can be altered by wilting (Castle & Watson 1970; Jackson & Forbes 1970; Donaldson & Edwards 1976; Hinks et al. 1976) and by the addition of formalin (Barry & Fennessy 1972; Brown & Valentine 1972; Valentine & Brown 1973; Valentine & Radcliffe 1975). However, it is not lmown whether milk yield and composition can be influenced by these changes, as previous studies (Brown 1960; Murdoch 1962; Kormos 1967; Castle & Watson 1970; Fisher et al. 1971; Valentine & Radcliffe 1975) have included con-founding effects due to different levels of feeding, and the supplementation of silages with concen-trates.

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

512 N.z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

In the two experiments reported in this paper, these problems have been avoided. The first compared the yield and composition of milk from cows fed either silage or pasture as sole rations. It examined whether specific dietary factors rather than intake, can explain effects of silage feeding. The second compared unwilted, wilted. and formaldehyde-treated silages. Effects of each feedstuff on apparent digestibilities of dry matter, nitrogen, and gross energy and on plasma and rumen fluid characteristics were observed.

MATERIALS AND METHODS

Exper~ment 1: Comparison of pasture and silage

Twenty-four cows in early lactation were individually fed in stalls for 10 days on a mixture comprising equal amounts on a dry matter (DM) basis of pasture and silage (Period I ). The pasture silage was made with a flail harvester in the spring of 1974. Pasture herbage was harvested from the same crop with a rotary mower, quick frozen at -33°e, and stored at - 20 0 e . (Hutton et al. 1975). The silage was removed from the bunker 2 months after ensiling, and frozen in a manner similar to the pasture.

Sufficient amounts of the rations were removed from the freezer each afternoon and allowed to thaw overnight. To permit ad libitum feed-ing, during the uniformity period (I), cows were offered 15% more than their previous day's intake, with subsequent additions where neces-sary. According to individual DM intakes and milk production during Period J, 8 balanced blocks each of 3 cows were formed. Cows in 4 of these were offered pasture and cows in the other 4 silage to appetite for a further lO-day period (Period II). During the succeeding 21 days (Period III) the same diet was fed to each cow as in Period II, but within diets, between groups of 3 cows, 4 contrasting levels of intake were applied: (a) silage to appetite based on the DM intake

measured over the last 7 days of Period II, and 90%, 80%, and 70% of (a) respec-tively, and

(b) pasture to appetite as measured over the last 7 days of Period II, and 80%, 60%, or 50% of (b) respectively.

After Period III, 2 cows from each treatment were transferred to metabolism stalls for 10 days to enable measurement of apparent digestibilities of dietary nitrogen and energy at each level of feeding (Period IV).

Blood samples were collected from each cow on the last days of Periods I and III immediately before and again 3 h after feeding. Rumen liquor was sampled 3 h after feeding, starting on the last day of Period III.

Experiment 2: Comparison of silages Three silages were made in late spring 1974,

from a pasture approaching ear emergence. UnwiIted pasture silage (US) was cut with a single-chop flail harvester. A second silage (FS) was similarly harvested except that formalin (35% w/v HCHO) was added (5 1/t wet weight) from an applicator attached to the harvester. Pasture for wilted silage (WS) was mown with a rotary mower, wilted for 24 h, and then fine chopped with a New Holland 717 harvester. Two months later the silages were removed from the bunkers, frozen, and stored at -20°c.

Twenty-seven cows in mid lactation were individually fed on non-exerimental high moisture silage for 10 days (Period I). On each of the following 21 days (Period II), sufficient of the 3 experimental silages was thawed overnight and each was offered to 9 cows, at one of each of three levels of intake. The levels were 100, 75 and 50% of the DM intakes during Period I. For 10 days after Period II, oows at the 75% level of feeding were confined in metabolism stalls for nitrogen and energy digestion trials (Period III).

Samples of blood and rumen fluid were obtained from cows at the 100% and 50% feeding levels: blood immediately before feeding and ,3 h later on the last day of Periods I and II, and rumen fluid 3 and 12 h after feeding on the last day of Period II.

General Pasture silages: The pasture silages fed in each

experiment were made from predominantly rye-grass (Lalium perenne)-white clover (Trifolium repens) pasture. Herbage was ensiled in con-crete bunkers and, after consolidation, covered with polythene film. [eeding-milking: Experimental animals were spring-calving Jersey cross-bred cows, aged 2-8 years. Each day feeding was from 0800 to 1300 h, and from 1600 to 2100 h. Each experi-ment started with a uniformity period (Period I) of 10 days and data obtained during the last 7 days of this were used as a basis for allocating cows to subsequent treatments.

Cows were milked twice daily at 0700 and 1600 h. Individual milk yield was measured at each milking and aliquot samples were bulked

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

ROGERS et at.: PASTURE SILAGE AND MILK COMPOSITION I 513

over 2 successive periods of 3 and 4 days in each week and preserved (Lactabs: Thompson and Capper Ltd .. Liverpool). Fat, protein (N X 6.38), and lactose contents of milk were deter-mined, respectively, by the Gerber techniques (BS.695,2), the standard Kjeldahl nitrogen diges-tion followed by steam distillation (AOAC 1965). and by the ferricyanide method using the Tech-nicon Autoanalyser (Technicon methodology N, 2a). Additional milk samples were collected over the last 7 days of digestibility trials for determina-tion of gross energy content. They were pre-served with 1 ml formalin, freeze dried, and analysed by adiabatic bomb calorimetry. Cows were weighed each morning after milking except during digestibility periods when they were weighed after completion of excreta collection.

Digestibility trials: Total faecal and urine coll-ections were made with equipment similar to that described by Hughes (1963). Proportionate samples of each were collected daily and bulked within cows over 7 days. DM in the faeces and urine was measured by oven drying at lOO°c and freeze drying for 24 h, respectively. The heats of combustion of dried samples were determined by adiabatic bomb calorimetry. Crude protein (N X 6.25) was determined on fresh samples of faeces and urine by standard Kjeldahl diges-tion and steam distillation procedures (AOAC 1965) .

Feed analysis: Percentage DM in samples representative of feed offered and refused during each 7 days was estimated by oven drying pasture each day at 100 0 e for 24 h and by toluene distilla-

tion of silage bulked over this period (Minson & Lancaster 1963) . Dried feed samples were analysed for concentrations of ,energy and fresh samples for N in the manner indicated for faecal samples. The loss of energy from the silage dur-ing drying was assumed to equal the calorific value of its VF A content as indicated by gas liquid chromatography (GLC). VFAs in feed samples (40 g) were determined by adding 6N H2S01 (60 g), extracting the mixture for 24 h, then distilling 4 ml of the extract in a Markham still. After making the distillate alkaline with N NaOH and drying, 0.5 ml phenol solution (2 gil) was added. acidified with H3PO! (85% w/w) , and samples (2 ,ttl) were injected into the GLC glass column (1 m X 3mm 1.0.), packed with Chromosorb 101 (fohns-Manville, USA lOO-120 mesh), and operated at 190 0 e with carrier gas (N~) flow of 35 ml/min. Concentrations of VFA were calculated by comparing peak areas with those of phenol, the internal standard.

Water-soluble N was measured by Kjeldahl analysis of 25 ml aliquots of supernatant obtained after 80 g pasture or silage in 400 ml water were homogenised for 2 min and centrifuged at '5000 g for lO min. Further aliquots (50 ml) of the supernatant were treated with an equal volume of 10% TCA for determining the soluble protein fraction .. Non-protein nitrogen (NPN) was calculated by difference. Water-soluble carbohydrate in the supernatant was determined by an anthrone procedure (Bailey 19511). Modified acid detergent (MAD) fibre was deter-mined by the method of Clancy & Wilson (1966).

TABLE 1 - Chemical composition of diets

Experiment 2 Silages

Character Silage Pasture Unwilted Formaldehyde Wilted (S) (P) (US) (FS) (WS)

n 6 6 6 6 6 DM% 13.7 15.7 21.8 22.9 56.7

Composition/IOO g DM MAD fibre (g) 35.3 29.7 40.0 38.3 35.7 GE (MJ) 1.79 1.81 1.78 1.75 1.82 Total N (g) 2.5 2.8 2.5 2.5 2.5 Soluble prot. N (g) 0.0 0.49 0.01 om 0.02 NH3-N (g) 0.25 0.03 0.23 0.11 0.12 Sol. carbohydrate (g) 1.4 5.8 0.4 2.0 4.5 Lactic acid (g) 8.6 0.4 5.7 3.1 6.8 Olher acids (g) 1.8 0.4 5.9 1.6 0.1 pH 3.9 5.4 4.3 4.3 5.0

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

514 N.z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

TABLE 2 - Mean apparent digestibility coefficients of diets

Experiment Diet means Character S P SD sig.

n 8 8 DM 68.8 75.8 1.4 *** GE 69.7 74.3 1.2 *** N 68.3 65.1 2.0 *. Experiment 2 Diet means Character US FS WS SD sig.

n 3 3 3 DM 60.0 53.6 60.8 4.2 t GE 62.1 52.7 58.8 4.2 * N 60.5 44.8 55.4 4.6 ***

Note: In this and subsequent tables abbreviations used are: Diet· = as in text RSD = Residual standard deviation SD = within diet standard deviation SED = standard error of difference n = no. of cows t P < 0.10, *P < 0.05, **P < 0.01, ***P < 0.001

Blood analysis: Blood (15 ml) was collected from the jugular vein in heparinised vacutainer tubes (Becton-Dickinson, Rutherford, New Jersey). Immediately after withdrawal, packed cetl volumes (PCV) were determined with a micro-haematocrit centrifuge, and plasma for analysis was separated using a refrigerated centri-fuge (4°c, 2000 r.p.m. for 15 min). Fresh plasma

was analysed for amino N by the ninhydrin method of Rosen (1957) and blood urea by micro-diffusion (Conway 1957).

Rumen analysis: Rumen liquor (l00 ml) was withdrawn by stomach tube. Saturated mercuric chloride solution was immediately added to the sample which was stored at - 20°c after filtering through cheesecloth. Liquor samples (2 ml) were made alkaline with N NaOH, dried, and analysed for individual concentrations of VFA by GLC as described above.

Statistical methods: The objective of analysis of data from the periods of differential feeding was to estimate milk production and milk com-position from cows fed different rations, at the same digestible energy intake. Since variation between cows in production and composition of milk depends on the inherent productivity of the animal and food intake, a multiple regression analysis was used to relate milk yield and com-position in the experimental and uniformity periods, to digestible energy intake/kg Lwo.75/ day (DEI). Pseudo variables (Gujarati 1970) were used to allow models to be fitted in which regression coefficients and/or intercepts varied with diet. In each analysis a single coefficient for uniformity was adequate, and the data are summarised in tables by presenting intercepts and partial regression coefficients on DEI for equa-tions chosen by standard significance testing of the goodness of fit of alternative models.

RESULTS

Table 1 summarises the data on diet composi-tion of the rations fed in the two experiments, and Table 2 the digestibility data for each.

TABLE 3-Experiment 1: Mean values of milk character, and relationships with intake, DEI/Lwo.n (Mf/kg LWo.75 /day) during Period III

Diet means Regression coefficients Intercept Character S p SD S P S P RSD

n 12 12 DEI/LWo· 75 1.50 2.21 0.11 Milk (kg/day) 8.6 11.0 3.3 2.4 * ± 0.9 3.6 ** ± 0.8 -5.3 0.9 Fat (g/day) 346 511 152 18 ± 47 121 ** ± 39 -165 4;9 Protein (g/day) 231 332 101 106 *** ± 27 155 *** ± 21 -211 27 Lactose (g/day) 414 557 176 61 ± 64 144 * ± 51 -207 63 Fat % 4.04 4.66 0.58 -0.48* ± 0.18 0.88 1.62 0.23 Protein % 2.70 3.01 0.21 0.34* ± 0.14 0.48*** ± 0.11 0.36 0.14 Lactose % 4.77 5.06 0.50 -0.31 ± 0.29 -2.51 -2.14 0.40

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

ROGERS et al.: PASTURE SILAGE AND MILK COMPOSITION I 515

TABLE 4 - Experiment 1: Effect of diet on partition of nitrogen and energy

Difference Character Diet means (P-S) ± SED

S P

n 8 8 % of N intake

Faeces 31.6 34.8 3.2** ± 1.2 Urine 42.4 48.7 6.3 ± 2.6 Milk 17.8 24.1 6.3** ± 1.6 Retention 8.2 -7,6 -15.8** ± 2.0

% of N digested Urine 62.1 74.8 12.7' ± 2.5 Milk 26.0 36.9 10.9** ± 2.4 Retention 11.9 -11.8 -23.7** ± 2.3

% of GE intake Faeces 30.3 25.6 -4.7*** ± 0.7 Urine 4.8 4.3 -0.5 ± 0.3 Methane 8.4 8.7 0.3*** ± 0.03 Milk 18.6 21.3 2.7 ± 2.0 Retention 37.9 40.1 2.2 ± 1.8

% of GE digested Urine 6.9 5.8 -1.1t ± 0.5 Milk 26.6 28.5 1.9 ± 2.8 Retention 54.4 53.9 -0.5 ± 2.7

Dietary ME 10.0 11.3 1.3** ± 0.5 (MJ/kg DM)

Experiment 1 Pasture had a higher DM content than silage

(Table 1). Per unit DM, there were higher con-centrations of N and soluble carbohydrates in pasture compared with silage, lower levels of MAD fibre, and only small amounts of lactic, acetic, and butyric acids. The forms of N in the herbage were considerably altered by ensiling, as shown by changes in levels of NHa and soluble protein N.

In silage, the digestibility of N was higher, but that of DM and GE lower, than in pasture (Table 2). Effects of diet on performance

In Period II, when cows were fed ad libitum, the mean DEI for cows fed pasture was 2.22 MJ /kg L WO. 75/ day and for those fed silage 1.50, a decrease of 32%. Associated with this differ· ence were highly significant (P < 0.001) differences in milk yield (1.9 ± 0.04 kg), and in concentrations of fat (0.31 ± 0.07%) and protein, (0.19 ± 0.05%), but not lactose (0.02 ± 0.07%). Partly as a consequence of the differences in voluntary intake and digestibility, when different feeding levels were imposed in Period III, there was a smaller range in DEI

between groups offered silage (1.41-1.16 MJ/kg LWo.7 ;J/day) than in those fed pasture (2.06-1.11 MJ/kg LW°7r,/day).

Table 3 summarises for Period III the partial regression coefficients of milk, fat, protein, and lactose on DEI. The model with different coeffi-cients but a common intercept described the pro-duction-intake relationships. The partial regres· sion coefficients were greater for pasture than silage, implying greater productions at the same DEI. Fat percentage decreased with increase in DEI, and protein percentage increased. . The t<:bulated regression for protein percent from silage fed cows is statistically significant, but this arose frow a lower standard error associated with constraining the intercept, and the individual silage regression was non·significant. At the same DEI, milk yield and concentrations of fat and protein were higher on pasture than on silage. Thus, at a DEI of 1.5 MJ/kg LWO.75/day, the regressions estimate for pasture, advantages of 1.8 kg milk/cow/day and 0.74% and 0.21 % for fat and protein con,centrations respectively. The relationship between live-weight change (Y) and DEI was

Y = 0.6 DEI - 2.1 (pasture) -·1.2 (silage)

showing that at the same intake, pasture-fed animals lost more weight. Utilisation of dietary N and energy

Proportionately more ingested N was excreted in faeces, urine, and milk by cows fed pasture than silage (Table 4). As a consequence N reten-tion was lower for pasture-fed cows, all of which were in negative N balance.

TABLE 'i - Experiment 1: Mean concentrations and percentages of VFAs in rumen liquor

Diet Means Difference Character S P (P-S) ± SED

n 12 12 VF A (me.! t 00 m\)

HAc 5.52 4.89 -0.63** ± 0.21 HPr 202 1.53 -0.49*** ± 0.08 HBu 0.86 1.35 0.49*** ± 0.07 Total 8.40 7.78 -0.62t ± 0.35

% total VFA HAc 65.7 63.0 -2.7 *** ± 0.7 HPr 23.9 19.6 -4.3 *** ± 0.5 HBlI 10.3 17.4 7.1 *** ± 0.4 HAc/HPr 2.7 3.2 0.6 ** ± 0.2

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

516 N.Z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

TABLE 6 -' Experiment 1: Mean concentrations of plasma characteristics

Diet means Difference Character Silage Pasture (P-S) ± SED

n 12 12 PCV %

o h 30.8 32.8 2.0 ± 1.2 3 h 33,7 31.5 -2.2 ± 1.2

Urea (mg/100 m!) o h 11.9 13.0 1.1±1.1 3 h 15.7 15.7 0.0 ± 1.1

Amino N (mg/I) o h 23.9 29.0 2.0 ± 1.9 3 h 25.9 31.7 2.7 ± 1.9

Proportionately less dietary energy from pasture than from silage was excreted in the fa,eces, but more was secreted in milk and retained as body tissue. Irrespective of diet, the level of feeding was without significant effect on the partitioning of ingested energy. Composition of rumen liquor and blood

Levels of feeding had no detectable effect on VFA's in rumen liquor. Thus only diet means are given in Table 5. Molar percentages of acetic and propionic acids were higher, and butyric acid lower in cows fed silage than in those fed pasture. The molar ratio of acetate to pro-pionate was less for- silage than pasture.

Whereas the PCV of cows on a sole ration of silage increased during the first 3 h of feeding by 2.9 ± 1.0% (P < 0.01) (Table 6), for those fed pasture there was a· slight decrease. There was no statistically significant effect of level of feeding or of diet on PCV at either time. The

levels of urea and amino N in blood plasma increased after feeding either silage or pasture, but the average difference between diets was non-significant.

Experiment 2 The chemical composition of each silage is

presented in Table 1. Wilting and formalin treatments had little effect on N content, but both reduced the amount of free ammonia and of acids in the silage. Soluble carbohydrate content increased in WS; FS was intermediat,e between WS and US. Trends in MAD fibre content were the reverse of this.

The apparent digestibiIities of the DM, GE. and N from WS were significantly lower than those from US (Table 2). Effects of diet on performance

The regression coefficients on DEI of the yield of milk and its constituents were similar for all silages, and the effects of diet, free from level of feeding, are shown as adjusted means in Table 7. Compared with US at the same energy intake, wilting increased production of all milk con-stituents (P < 0.05), and formalin treatment raised both fat and protein yields (P < 0.05). With increasing intake, fat percentage decreased, but there were no marked changes for protein or lactose percentages.

In this trial cows fed US gained 0.9 kg/live weight/day less than those fed FS or WS, when calculated at the same DEI.

Utilisation of dietary N and energy Data on N and gross energy (GE) partitioned

at the 75% level of intake are given in Table 8. Formalin . reduced Nand GE digestibility but it also reduced urinary losses. There was no signi-ficant effect of diet on retention of Nand GE.

TABLE 7 - Experiment 2: Mean values of milk characters and relationships with intake, DEI/LWo. 7:i (MJ/kg LWo.T3/day)

Diet means Regression Adiusted means Character US FS WS SO sig. coefficien t US FS WS RSD sig.

n 9 9 9 DEI/LWo.75 1.38 1.05 1.16 0.31 Milk (kg/day) 6.2 5.7 6.3 2.0 * 2.7*** ± 0.4 5.7 6.1 6.4 0.6 t Fat (g/day) 293 293 309 87 11S 105*** ± 20 274 308 313 30 * Protein (g/day) 188 181 200 57 t 81*** ± 12 173 192 202 17 ** Lactose (g/day) 297 268 294 95 t 132*** ± 19 272 287 299 29 ns Fat % 4.79 5.17 5.03 0.59 * -0.41* ± 0.15 4.88 5.10 5.01 0.23 ns Protein % 3.05 3.19 3.20 0.26 ns -0.03 ± 0.10 3.06 3.18 3.20 0.15 ns Lactose % 4.75 4.69 4.68 0.19 ns 0.07 ± 0.05 4.74 4.70 4.68 0.08 ns

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

ROGERS et al.: PASTURE SILAGE AND MILK COMPOSITION I 517

TABLE 8 - Experiment 2:. Effect of diet on partition of nitrogen and energy

Character US FS

n 3 3 % of N intake

Faeces 39.4 55.2 Urine 45.3 30.9 Milk 13.5 12.1 Retention 1.8 1.8

% of N digested Urine 74.9 69.2 Milk 22.3 27.1 Retention 2.8 3.4

% of GE intake Faeces 37.9 46.8 Urine 5.1 3.5 Methane 7.8 7.5 Milk 12.7 12.3 Retention 36.4 29.9

% of G E digested Urine 8.2 6.6 Milk 20.8 23.1 Retention 58.3 56.2

Dietarv ME 8.8 7.4 (MJ/kg DM)

Concentrations of total and individual VF As except butyric acid measured 3 h after feeding were lower for cows fed FS than for cows fed the other rations (Table 9). Differences had dis-appeared by 12 h. By this time cows on the highest level of feeding had highest concentra-tions of VF A in rumen fluid, representing increased molar proportions of propionate and valerate and decreased acetate. Molar percen-tages of propionate and valerate were higher and butyrate lower for cows fed US compared with the other two rations.

Blooel composition The diets did not differ in their effects on PCV

or concentration of amino N (Table 10). Blood urea was highest for US at both sampling times. As level of feeding decreased, pev decreased, but concentrations of urea and amino N were unaffected.

DISCUSSION

The first experiment showed that cows offered unwilted pasture silage to appetite produced less milk, protein. fat, and lactose than those offered pasture. Fat and protein content of milk was also reduced. These effects were associated

Diet means WS SD sig.

3

43.6 3.0 *** 41.7 0.7 *** 14.0 1.9 ns 0.5 2.4 ns

13.8 2.3 t 25.3 3.5 ns

0.9 2.l t

41.4 3.0 * 3.8 0.2

_. 7.8 0.2 ns

12.5 2.l ns 34.5 4.8 ns

6.5 0.6 * 21.3 4.1 ns 58.7 52 ns

8.8 0.5 t

with a decrease of 32% in the intake of DE and are similar to' those observed by other workers (Wallace & Parker 1966; Hutton ef'aT. 1971; Lancaster et aT. 1974). The specific effects on milk yield and on the concentrations of protein and fat in milk were clearly demonstrated in Period III, indicating that factors other than the amount of DE consumed may also affect milk synthesis of cows feeding solely on forage diets.

The second experiment demonstrated that different silages can have differenteff,ects on milk production. At the same intake of DE, cows fed wilted silage produced more milk, fat, protein, and lactose and had a higher protein concentra-tion than did cows on unwilted silage; the addition of formalin produced similar quantities of milk, but higher yields of fat and protein, and a higher milk fat concentration. Whether the effects observed with wilted silage were due to wilting or to precision chopping is not important in the present instance.

Intra-ruminal infusions of acetate solutions have been shown to increase milk yield and milk fat percentage, and infusions of propionate solu-tions have increased milk protein percentage (Rook & Balch 1961; Rook et aT. 1965; Wilson

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

518 N.Z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

TABLE 9 - Experiment 2: Mean concentrations and molar percentages of VFAs in rumen liquor

Diet means Level effect Character US FS WS SO sig. 100%-50%

n 6 6 6 VFA (me./100 ml)

HAc 3 h 3.21 2.86 3.44 0.36 0.16 ± 0.17 12 h 3.09 3.22 3.46 0.38 ns 0.37t ± 0.18

HPr 3 h 1.29 1.02 1.30 0.15 ** 0.01 ±0.D7 12 h 1.05 1.01 1.10 0.15 ns 0.28** ±0.D7

HBu 3 h 0.90 0.90 1.16 0.13 * 0.09 ± 0.06 12 h 0.74 0.86 0.88 0.15 ns 0.21 ** ± 0.07

HVa 3 h 0.38 0.22 0.30 0.04 ** -0.02 ± 0.02 12 h 0.16 0.11 0.13 0.02 ns 0.08*** ± 0.01

Total 3 h 5.78 5.01 6.18 0.66 * 0.18 ± 0.31 12 h 5.01 5.19 5.55 0.64 ns 0.99*- ± 0.30

% total VFA HAc 3 h 55.6 57.2 55.7 1.7 ns 0.1 ± 0.8

12 h 61.9 62.0 62.6 1.5 ns -4.7*** ± 0.7 HPr 3 h 22.4 20.4 20.6 0.8 ** -0.1 ± 0.4

12 h 20.7 19.4 19.7 0.8 * 1.8*** ± 0.4 HBu 3 h 15.4 17.8 18.7 1.3 -* -0.5 ± 0.6

12 h 14.6 16.4 15.5 1.4 * 1.5 ± 0.7 HVa 3 h 6.5 4.4 4.8 0.8 ** -0.6 ± 0.4

12 h 3.1 2.1 2.2 0.4 ** 1.1 *** ± 0.2 HAc/HPr 3 h 2.5 2.8 2.7 0.2 ns 0.1 ± 0.1

12 h 3.0. 3.2 3.2 0.2 ns -0.5 ± 0.1

T ~BLE 10 - Experiment 2: Mean concentrations of plasma characteristics

Diet means Level effect Character US FS WS SO sig. 100%-50%

n 6 6 6

PCV %

o h 32.S 33.4 32.0 2.7 ns -2.1 ±1.3

3 h 33.4 32.9 32.0 2.0 ns -4.2** ± 1.0

Urea (mg/100 ml)

o h 12.5 10.8 10.4 1.4 * -2.4 ± 0.7

3 h 17.3 14.1 15.8 1.7 * 0.3 ± 0.8

Amino N (mg/!)

Oh 31.3 33.9 34.6 4.2 ns -1.1 ± 2.0

3 h 36.9 37.2 40.0 3.1 ns 1.6 ± 1.5

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

ROGERS et al.: PASTURE SILAGE AND MILK COMPOSITION I 519

et ai. 1967). In Experiment 1, silage resulted in higher concentrations and molar proportions of acetate and propionate in rumen fluid than did pasture, yet milk yield and the concentrations of fat and protein in the milk were less. Similarly. the lower fat and protein contents of the milk from cows offered unwilted silage in Experiment 2 were also associated with higher concentrations and molar proportions of acetate and propionate. Thus, these rumen acids may not be important determinants of differences in milk yield and milk fat and milk protein contents of cows fed silage.

Armstrong & Prescott (1971) concluded that the molar ratio of acetate and propionate in rumen fluid influences milk fat percentage. In both experiments reported here the lower milk fat percentage of cows eating unwilted silage was associated with a decrease in the molar ratio of acetate to propionate. However, this change was relatively small and this factor was unlikely to have been of major importance. The lower milk fat synthesis by cows fed unwiIted silage was also associated with a large reduction in the molar percentage of rumen butyrate. Since butyrate is metabolised to ~-hydroxybutyrate, a major precursor for milk fat synthesis (Smith et ai. 1974), this reduction possibly contributed to the reduction in milk fat percentage.

Diets inducing a decrease in milk fat per-centage have also increased molar proportions of propionate in rumen fluid (McCullough 1966; Armstrong & Prescott 1971; Annison et ai. 1974) and have reduced levels of milk fat precursors in plasma (Annison et ai. 1974), presumably because of increased synthesis of tissue fat (Annison 1976). Since cows fed silage in Experi-ment 1 tended to have higher molar proportions of rumen propionate and lost less body weight than cows fed pasture, the lower milk fat synthesis of the former may have, in part, been caused by a lower supply of endogenous pre· cursors. Such an explanation does not, however, account for the observation that in Experiment 2, weight gain was lowest with unwilted silage.

In Experiment 1, diet type, had a pronounced effect on the partitioning of dietary N. Pasture-fed cows produced milk containing more N relative to N intake than those fed silage. They also excreted more N in urine and faeces and in consequence were in negative N balance. The association of the higher live-weight loss and negative N retention for the pasture-fed animals indicates that they were mobilising tissue protein. The resulting increased supply of endogenous amino acids may account for the increased quantities of N in the milk, although the use of

this source of amino acids for milk protein synthesis is uncertain (Van Es & Boekholt 1976). Alternatively, the improved efficiency of utilisa-tion of digested pasture N for milk synthesis may have been due to between-diet differences in rumen N metabolism. The higher N solubility and non-protein N content of silage than of pasture would tend to increase rumen ammonia concentrations (Sniffen 1973; Donaldson & Edwards 1976), and the lower soluble carbo-hydrate in silage would impair assimilation of ammonia into microbial protein (Smith 1969). This would promote increased ammonia absorp-tion from the rumen (Armstrong 1974), reduc-ing the amount of dietary protein entering the duodenum (Hogan & Weston 1969; Macrae et al. 1972). However, these possibilities cannot be sub-5tantiated from the data obtained in Experiment 1, and no differences were observed between rat-ions in plasma levels of urea or amino N.

Evidence was obtained in Experiment 2 that strongly suggests that differences in utilisation of dietary N account for some of the differences in milk composition. Compared with formalin-treated silage. unwilted silage increased urinary loss of both energy and N, explicable in terms of increased loss of N from the rumen. The higher solubility of N in the unwilted silage. and the higher levels of blood urea and valerate in rumen liquor of these animals, also suggest a more extensive rumen degradation of the protein from this diet (el-Shazly 1952). Further, since microbial use of ammonia is limited by the availability of energy (Smith 1969), the higher soluble carbohydrate content of formalin and wilted silages would enhance microbial protein synthesis and thereby reduce the loss of dietary N as ammonia absorbed from the rumen (Arm-strong 1974).

The formalin treatment clearly reduced the digestibility of dietary N and markedly decreased ammonia content, indicating reduced proteolysis during ensiling, and a fall in the solubility of the N. Formaldehyde bonds with dietary protein, inhibiting proteolysis both during ensiling and in the rumen (Barry 1976; Wilkinson et al. 1976). Further, Beever et al. (1974) indicated that when silage is treated with formalin. much dietary protein escapes rumen degradation, thereby increasing the amount of protein entering the duodenum. Both of these factors probably account for the increased yields of milk protein

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

520 N.z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

of cows fed formalin-treated silage compared with unwilted silage.

Wilting had less effect on N digestibility than did formalin treatment. Wilting did not alter the solubility of N but reduced the ammonia level of the silage, indicating that although proteolysis may have been as extensive as in unwilted silage, deamination was less. The reduced plasma urea levels of cows fed wilted silage compared with those fed unwilted silage support this possibility.

By contrast, the possibility that cows fed wilted and formalin-treated silages absorbed more amino acids than cows fed unwilted silage was not substantiated by the plasma and amino N concentrations. PCV percentage was also not affected by the silage rations, showing that dietary changes in milk composition and PCV percentage were unrelated. In both experiments increasing feeding level decreased milk fat per-centage even though milk fat yield increased. Reasons for this are not apparent. The fact that milk lactose percentage was independent of feeding level ,is consistent with the hypothesis that lactose is the major determinant of isoton-icity. between milk and blood (Rook & Wood 1959) .

The lack of a relationship between milk protein percentage and silage intake in Experiment 2 agrees with the inferences of Hutton et aT. (1971) and Lancaster et aT. (1974) and is in marked contrast to the response with pasture in Experiment 1. The increase in milk protein yield with pasture intake was associated with an increase in milk yield and milk protein percen-tDge, implying a disproportionate increase in precursors for milk protein synthesis relative to silage.

This study shows that milk yield and composi-tion can be altered by varying the amount and quality of forages offered to dairy cows. This is of major practical importance to the dairy farmer, since payment incentives are likely to increase for milk solids other than fat, parti-cularly protein. The deleterious effect of unwilted silage on the protein content of milk is therefore important. The effect can, however, be amelio-rated either by adding formalin to the forage during harvesting, or by wilting. In the present trials these techniques increased milk protein synthesis by 19 g/ cow/day and 29 g/ cow/day and raised the percentage in milk protein by 0.12 and 0.14 units, respectively. In practice, when these rations are fed as sole diets to milking cows larger responses may be expected, since both wilting and formalin treatment generally increase the voluntary intake of silage, compared

with direct harvesting (Wilkinson et aT. 1976). To enhance the practical value of the results presented, further studies are required to define optima for treating silages to increase milk yield and composition both for circumstances in which these feedstuffs are used as sole rations and when fed in limited amounts as supplements of pasture.

Acknowledgments

We are greatly indebted to Mr R. Newth and staff of the Nutrition Centre, Ruakura, for their assistance with chemical analyses and management of animals; to N.Z.M.A.F. for provision of facilities and to the Australian Dairy Research Committee and the W. B. McLaughlin Trust for financial assistance.

REFERENCES

Annison. E. F.; Bickerstaff, R.; LinzelI, J. L. 1974: Glucose and fatty acid metabolism in cows pro-ducing milk of low fat content. Journal 0/ Agricultural Science, Cambridge 82: 87-95.

Annison, E. F. 1976: Energy metabolism in the body. In "Principles of Cattle Production" pp. 169-99, Ed. H. Swan and W. H. Broster. Butterworths, London.

Armstrong, D. E.; Prescott, J. H. D. 1971: Amount, physical form and composition of feed and milk secretion in the dairy cow. In "Lactation" pp. 349-77, Ed. J. R. Falconer. Butterworths London.

Armstrong, D. G. 1974: Factors affecting the protein value of fresh and conserved foods. Proceedings of 5th General Meeting, European Grassland Federation, Uppsala: 114-22.

Association of Official Agricultural Chemists (AOAC) 1965: "Official Methods of Analysis", 10th ed. AOAC, Washington, D.C.

Bailey, R. W. 1958: The reaction of pentoses with anthrone, Biochemcial Journal 58: 669-70.

Barry, T. N. 1976: The effectiveness of formaldehyde treatment in protecting dietary protein from microbial degradation. Proceedings of the Nutrz-tion Society 35: 221-29.

Barry, T. N.; Fennessy, P. F. 1972: The effect of formaldehyde treatment on the chemical com· position and nutritive values of silage. 1. Chemical composition. N.Z. Journal of Agricultural Research 15: 712-22.

Beever, D. E.; Thompson, D. T.; Harrison, D. E. 1974: Energy and protein transformations in the rumen and the absorption of nutrients by sheep fed forage diets. Proceedings of the XIIth Inter-national Grassland Congress 3: 56-62.

Brown, S. M. 1960: Silage feeding of the dairy cow and its effect on milk yield and composition. III. A comparison of the ad libitum feeding of high dry matter. lacerated, and low dry matter, unlacer<lted. grass silages. The Research and Experimental Record of. the Ministry of Agri-culture, Northern Ireland 10: 9-19.

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

ROGERS et al.: PASTURE SILAGE AND MILK COMPOSITION I 521

Brown, D. C.; Valentine, S. C. 1972: Formaldehyde as a silage additive. I. The chemical composi· tion and nutritive value of frozen lucerne silage and formaldehyde trea,ted lucerne silage. Aus· tralian Journal of Agricultural Research 23.: 1093-100.

Castle, M. E.; Watson, J. N. 1970: Silage and milk production, a comparison between wilted and unwilted grass silages made with and without formic acid. Journal of the British Grassland Society 25: 278-84.

Clancy, M. J.; Wilson, R. K. 1966: Development and application of a new chemical method for pre· dicting the digestibility and intake or herbage samples. Proceedings of Xth International Grassland Congress 445-53.

Conway, E. J. 1957: "Micro Diffusion Analysis and Volumetric Error", 4th ed. Crosby Lockwood, London.

Donaldson, E.; Edwards, R. A. 1976: Feeding value of silage: silages made from freshly cut grass, wilted grass and formic acid treated wilted grass. Journal of the Science of Food and Agriculture 27: 536-44.

el·Shazly, K. 1952: Degradation of protein in the rumen of the sheep. I. Some volatile fatty acids, including branched·chain isomers found in vivo. Biochemical Journal 51: 640-7.

Fisher, L. J.; Donnelly, P. E.; Hutton, J. B.; Duganzich, D. M. 1975: Relationships between levels of feeding and certain blood metabolites in dairy cows in mid lactation. Journal of Agri· cultural Science, Cambridge 84: 29-38.

Fisher, L. J.; Lessard, J. R.; Lodge, G. A. 1971: Utilization of formic acid treated sorghum·sudan silage by dairy cows. Canadian Journal of Animal Science 51: 371-6.

Gujarati, D. 1970: Use of dummy variables in testing for equality between sets of coefficients in linear regressions: A generalization. The Ameri· can Statistician 24: 18-22.

Hinks, C. E; Edwards, I. E.; Henderson, A. R. 1976: Beef production from formic acid treated and wilted silages. Animal Production 22: 217-24.

Hogan, J. P.; Weston, R. H. 1969: The digestion of pasture plants by sheep. III. The digestion of forage oats varying in maturity and in the content of protein and soluble carbohydrate. Australian Journal of Agricultural Research 20: 347-63.

Hughes, J. W. 1963: Equipment for the separate and total collection of faeces and urine from dairy cattle. N.Z. Journal of Agricultural Research 6: 127-39.

Hutton, J. B. 1973: The effect on pasture intake and milk production of variations in the percentage utilization of total available dry matter. Annual Report of Research Division 1972-73, p. 51. Ministry of Agriculture and Fisheries, Welling· ton, N.Z.

----- 1975: Growing and using maize on the dairy farm. Proceedings of the Ruakura Farmers' Conference: 76~82.

Hutton, J. B.; Hughes, J. W.; Bryant, A. M.; Pluck; L. J.; Taylor, R. E. C. 1975: Evaluation of high moisture forages with ruminants. I. Equip· ment and techniques for harvesting, processing, and storing high·moisture forages. N.Z. Journal of Agricultural Research 18: 37.

Hutton, J. B.; Jury, K. E.; Hughes, J. W.; Parker, O. F.; Lancaster, R. J. 1971: High moisture silage from mixed pasture herbage as a feed for lactating dairy cows. Ibid. 14: 393-405.

Jackson, N.; Forbes, T. J. 1970: The voluntary intake by cattle of four silages differing in dry matter content. Animal Production 12: 591-99.

Kormos, J. 1967: A study of ensiling wilted and unwilted grass at two stages of maturity. 2. Effect on milk production. Record of Agri· cultural Research, Ministry of Agriculture, Northern Ireland 16: 57-63.

Lancaster, R. J.; Hutton, J. B.; Hughes, J. W.; Marshall, R. J. 1974: Effect on intake and pro· duction of dairy cows of feeding three high· moisture silages having different fermentation characteristics. N.Z. Journal of Experimental Agriculture 2: 389-92.

McCullough, M. E. 1966: Relationships between rumen fluid, volatile fatty acids and milk per· centage and feed intake. Journal of Dairy Science 49: 896-8.

MacRae, J. C.; Ulyatt, M. J.; Pearce, P. D.; Hendtlass J. 1972: Quantitative intestinal digestion of nitrogen in sheep given formaldehyde treated and untreated casein supplements. British Journal of Nutrition 27: 39-50.

Minson, D. J.; Lancaster, R. J. 1963: The effect of oven temperature on the error in estimating the dry matter content of silage. N.Z. Journal of Agricultural Research 6: 140-6.

Murdoch, J. C. 1962: The effect of type of concen· trate on milk production when silage is the only roughage offered to cows. Journal of the British Grassland Society 17: 268-73.

Rook, J. A. F.; Balch, C. C. 19,61: The effects of intra ruminal infusions of acetjc, propionic and butyric acids on the yield and composition of the milk of the cow. British Journal of Nutrition 15: 361-9.

Rook, J. A. F.; Balch, C. C.; Johnson" V. W. 1965: Further observations on the effects of intra· ruminal infusions of volatile fatty acids and of lactic acid on the yield and composition of the milk of the cow. Ibid. 19: 93.

Rook, J. A. F.; Wood, M. 1959: Potassium and lactose in milk in relation to the physiology bf milk secretion. Nature, London 184: 647.

Rosen, H. 1957: i} modified ninhydrin colorimetric analysis for ~mino acids. Archives of Bio· chemistry and Biophysics 67: 10-15.

Smith, R. H. 1969: Reviews of the process of Dairy Science Sections G. Nitrogen metabolism and the rumen. Journal of Dairy Research 36: 313-31.

Smith, G. H.; McCarthy, S.; Rook, J. A. F. 1974: Synthesis of milk from .a·hydroxy butyrate and acetate in lactating goats. Ibid. 41: 175-91.

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14

522 N.z. JOURNAL OF AGRICULTURAL RESEARCH, VOL. 22, 1979

Sniffen, C. J. 1973: Nitrogen utilization as related to solubility of NPN and protein in feeds. Pro-ceedings of Cornell Nutrition Conference for Feed Manufacturers: 12-18.

Valentine, S. C.; Brown, D. C. 1973: Formaldehyde as a silage additive. II. The chemical composi-tion and nutritive value of lucerne hay, lucerne silage, and formaldehyde and formic acid treated lucerne silages. Australian Journal of Agri· cultural Research 24: 939-46.

Valentine, S. C.; Radcliffe, J. C. 1975: The nutritive value for dairy cows of silage made from form-aldehyde-treated herbage. Ibid. 26: 769-75.

Van Es, A. J. H.; Boekholt, H. A. 1976: Protein requirements in relation to the lactation cycle. In "Protein Metabolism and Nutrition". EAAP

pub. 16: 441-55. Eds. D. Cole, K. Boorman, P. Buttery, R. Neale, and H. Swan. Butterworths, London.

Wallace, L. R.; Parker, O. F. 1966: Comparison of three systems .of feeding silage after calving. Proceedings of the Ruakura Farmers' Con-ference Week: 148-58.

Wilkinson, J. M.; Wilson, R. F.; Barry, T. N. 1976: Factors affecting the nutritive value of silage. Outlook on Agriculture 9: 3-8.

Wilson, G. F.; Davey, A. W. F.; Dolby, R. M.; 1967: Milk composition as affected by intra-ruminal infusion of volatile fatty acids to cows on a restricted ration. N.Z. Journal 0/ Agri-cultural Research 10: 215-25.

Dow

nloa

ded

by [

Ade

lphi

Uni

vers

ity]

at 0

8:20

11

Nov

embe

r 20

14