Small Ruminant Research

ELSEVIER Small Ruminant Research 15 (1995) 257-263

Effects of protein source and level on performance of lactating Damascus goats in negative energy balance

M. Hadjipanayiotou*, A. Photiou Agricultural Research Institute, Nicosia. Cyprus

Accepted 20 April 1994

Abstract

Effect of protein source (untreated soybean meal vs. formaldehyde-treated soybean meal) at three levels (13, 15 and 18% CP in the concentrate mixture, DM basis) on milk yield, milk composition, body weight (BW) change and rumen metabolites of 48 lactating Damascus goats was studied. Animals were fed to meet maintenance energy requirements and 60% of milk production energy requirements. Animals were housed and fed concentrates in groups of two animals, whereas roughage was offered to a single group per treatment. Goats consumed 0.175 kg barley hay and 0.269 kg barley straw/d. There were no significant effects of protein concentration or source on milk yield, milk composition, BW change and rumen metabolites. Protein source did not affect rumen NH3-N and total VFA concentration, but dietary protein level had a significant effect (P < 0.00 1) on rumen NH,-N concentration. When all animals were changed to a higher feeding level at the end of the 42-d trial, milk yield was increased slightly; most of the extra feed allowance was directed towards weight gain. Formaldehyde (HCHO) treatment of soybean meal reduced degradability of DM (21 percentage units) and CP (19.2 percentage units) in the rumen. It was concluded that reduction in energy supply below requirements will result in considerably reduced milk yield, and that supply of a protein supplement of low degradability will not alleviate reduction in milk yield through greater mobilization of body reserves and subsequent use for milk production.

Keywords: Damascus goat; Protein source; Protein level; Milk yield; Milk composition; Rumen metabolite

1. Introduction

Energy requirements of dairy animals of high pro- duction potential cannot be fully met in early lactation, and animals compensate for the resulting energy deficit by mobilizing body tissue primarily from body fat (Morand-Fehr, 1981; Chestnutt, 1987). On the other hand, very limited amounts of body protein reserves can be drawn upon when dietary protein supply is inad- equate (Orskov et al., 1981).

*Corresponding author.

0921~4488/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved

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Efficient use of mobiIised fat for milk production is likely to depend on the availability of adequate supplies of essential amino acids to the mammary gland. Orskov et al. (1977) reported that cows in early lactation responded by increasing their milk yield when cows

were given protein supplements which escaped rumen degradation. Ewes have also responded in the same way (Gonzalez et al., 1982) when animals were in negative energy balance. Orskov and Hovel1 ( i986) postulated that the greatest application of protected protein sources in periods of limited feed resources availability was the greater use of fat reserves for milk production. Dual purpose breeds (milk and meat) of small ruminants

258 M. Hadjipanayiotou, A. Photiou /Small Ruminant Research 15 (1995) 257-263

produce considerable quantities of milk during the postweaning period and they may also rely on body reserves mobilization in periods of limited feed resources availability.

An increase in CP intake increased BW loss and milk yield in lactating ewes (Robinson et al., 1974) and the increases in milk yield were shown to be associated with increases in the amount of non-ammonia N reach-

ing the abomasum (Robinson et al,, 1979). Contrary, in studies of Cowan et al. (1981) there was no effect of level of protein intake on the rate of loss of body fat.

The present studies were undertaken to study the effects of protein source (unprotected vs. protected soybean meal) at three levels each on BW change, milk yield, milk composition and rumen metabolites in

Damascus goats offered 60% of their energy require- ments for milk production.

2. Materials and methods

Production study

A trial with 48 lactating Damascus goats (9lk3.6 d in milk, range 83 to 98) was conducted to study the effect of protein source (untreated soybean meal vs. formaldehyde-treated soybean meal) and level ( 13, 15 or 18% CP in the concentrate mixture, DM basis) on lactation performance and rumen metabolites of goats in negative energy balance. Animals were loosing weight ( -3.75f4.791 kg/head) from kidding to weaning of kids (49 d in milk), but they were gaining weight (3.5 + 12.58 kg/head) from weaning to the commencement of the experiment (9 1 + 3.6 d in milk). Goats were divided into six uniform groups based on their fat-corrected milk yield. Groups were allocated to treatments at random. The experiment was laid out in a completely random design with a 2 X3 factorial arrangement of the treatments. The two types of protein source (untreated, formaldehyde-treated soybean meal) comprised the two levels of one factor and the three levels of protein ( 13, 15 and 18% in the concen- trate mixture) the three levels of the other factor. Per- centage composition of the concentrate mixtures is in Table 1. The solution of formaldehyde (3 1 of 40% formaldehyde diluted in 77 1 of water/t of soybean meal) was sprayed onto soybean meal, while it was fed into a vertical mixer. After further mixing for approx. 10 min, the sprayed soybean meal was packed into

Table I Composition (g/kg) of concentratesa

C13 C1s C18

Barley grain 728 648 568 Barley spike awns 100 100 100 Corn grain 70 70 70 Untreated soya 40 120 200 Wheat bran 50 50 50 Limestone 7 7 7 Sodium chloride 3 3 3 Vitamin-trace elements 2 2 2

a In this and subsequent tables and figures: C and F represent con-

centrate mixtures with untreated or formaldehyde-treated soybean

meal, respectively; subscripts denote 13, 15 and 18% CP in the

concentrate mixture. In the F mixtures the untreated soya was com-

pletely replaced by formaldehyde-treated soya ( 1: 1 ratio).

sealed polyethylene bags. Bags were opened after 48 h and the soybean meal was poured onto a plastic sheet to a depth of 3-5 cm and allowed to air equilibrate for 72 h. Formaldehyde-treated soybean meal was then processed in the concentrate mixture like the untreated protein soybean meal at the rate of 1: 1. A vitamin-trace element mixture (Vita 6, Vita-Trace Nutrition, Cyprus) added in all mixtures supplied 6000 IU vita- min A, 1000 ILJ vitamin D,, 8.5 IU vitamin E, 23 mg

Mn, 1.75 mg I, 45 mg Zn, 30 mg Fe, 2 mg Co and 60 mg Mg per kg concentrate mixture (as fed basis). Con- centrate mixtures (9-mm cubes) were given along with roughage (approx. 0.7 : 0.3 ratio) from separate feed containers. Roughage was barley hay, harvested at the milk stage of rain maturity, and barley straw (0.2 : 0.1) .

Animals were housed and fed concentrates in groups of two animals each. Pens were of 2.7 X 1.5 m with concrete floor bedded with wood shavings. Roughage was offered to a single group per treatment. Animals had access to concentrates 2 h daily (one in the morning and one in the afternoon) and to roughage during the rest of the day. Goats were fed to meet their total main- tenance (0.4 MJ, ME X kg weight0.73) and 60% of their milk production energy requirements. Feed allowance was adjusted weekly based on fat-corrected milk yield and BW in the previous week. The dietary energy requi- rements (MJ ME) for production were estimated according to Economides (1986) from the energy value in milk ( Y= 1.64+0.42X) divided by 0.62 (where X= fat percentage and 0.62 is the efficiency of utilization of dietary ME for milk production). Animals

M. Hadjipanayiotou, A. Photiou /Small Ruminant Research 15 (1995) 257-263 259

Table 2

Chemical composition (% DM) of hay, straw and concentrates fed

to goats

DM CP Ash ADF NDF ADL”

Barley hay 87.2 9.9 9.9 33.5 63.5 3.8

Barley straw 88.0 4.5 7.0 46.4 76.1 5.0

C,? 89.4 13.0 4.7 1.9 19.5 0.9

C,, 89.2 15.0 5.3 9.3 21.8 0.9

C,X 88.3 18.1 5.1 9.1 19.6 0.9

F II 89.3 12.6 4.9 8.9 19.9 1.0

F 15 89.0 14.8 6.6 8.1 19.9 1.0

F IR 88.7 18.3 5.0 8.9 20.3 1.2

’ ADL. acid detergent lignin.

were weighed prior to the morning feeding at the begin- ning, end and once a week during the course of the 42- d trial. Milk yield was recorded twice a week. Animals were milked by machine twice daily (07 : 00 and 14 : 00 h) on non-milk recording days, and by hand, due to lack of measuring cylinders, on milk recording days. Representative samples from morning and afternoon milking were taken on one recording day and analyzed for protein, fat, ash and total solids (MAFF, 1973). It is assumed that changes in milk yield or milk compo- sition associated with method of milking are similar for all six treatments.

All concentrate mixtures were prepared from the same batch of basic ingredients. Soybean meal was bought from the market and its previous processing, if any, was unknown. Proximate constituents and other analyses were made on bulk, ground (1 mm) samples of feed as outlined by Harris ( 1970).

Large quantities (0.4-0.6 l/goat, to reduce contam- ination from saliva) of rumen liquor samples were taken from all goats 3 h after the morning feeding at the end of the experiment. Rumen liquor samples were obtained by means of a tube passed into the reticulo- rumen via the oesophagus and suction created by a vacuum pump. Samples were strained immediately after collection through two layers of fine muslin; the pH was measured immediately, and the samples then processed and analyzed for rumen ammonia nitrogen (NH,-N) and volatile fatty acid (VFA) concentration as outlined by Hadjipanayiotou et al. (1988b).

The mean concentrate intake of each pair per treat- ment was used as a single observation in statistical analyses. Data were analyzed using a General Linear Model procedure (SAS, 1989) that accounted for pro-

tein source (untreated soybean meal, formaldehyde- treated soybean meal), level of protein ( 13, 15 and 18% CP in the concentrate mixture, DM basis) and their interaction. Mean separation/comparison was performed using Duncan’s multiple range test.

On completion of the 42-d experimental period, dur-

ing which goats were on negative energy balance, they

changed over gradually (5 d) to a high level of energy

intake. Animals were daily on 1610 g concentrate, 580

g barley hay, 170 g straw and 450 g fresh berseem (Trifolium alexandrinum) . Goats were weighed at the beginning and at the end of the 28-d post-experimental

period.

Rumen degradation study

Three mature Damascus goats fitted with a perrna-

nent rumen cannulae, weighing on average 67 kg, were used to measure rumen degradability of dry matter and

CP of untreated and formaldehyde-treated soybean meal. Animals were kept in individual pens with con-

crete floors bedded with wood shavings. Goats were fed on 500 g concentrate (14% CP) and 500 g barley hay. The two samples were incubated (5, 8 and 24 h) in nylon bags (three bags/incubation interval) in the rumen of the animals as outlined by Hadjipanayiotou

et al. ( 1988a) for determination of their degradability.

Samples were analyzed for DM and CP before and after incubation. The mean of the three bags per incubation

interval was used for calculations. Processing of sam-

ples after withdrawal of bags from the rumen was as

outlined by Hadjipanayiotou et al. ( 1988a). Data on rumen degradability were analyzed using a

General Linear Model procedure (SAS, 1989) that

accounted for protein source (2), incubation interval (3) and their interaction,

Table 3

DM and CP degradability values of untreated and formaldehyde-

treated soybean meal incubated in the rumen of Damascus goats

Degradability ( W)

DM CP

Incubation interval (h) 5 8 24 5 8 24

Untreated soybean meal 54.5 67.5 89.4 30.0 40.0 57.8

Treated soybean meal 34.0 43.0 71.4 12.8 16.5 40.9 SD 6.14 4.73

260 M. Hadjipanayiotou, A. Photiou /Small Ruminant Research 15 (1995) 257-263

Table 4

Performance of Damascus goats on different levels ( 13, 15, 18% CP mix.) and sources (untreated, formaldehyde treated soybean meal) of dietary protein

C13 C,, C18 F 13 F1S F 18 SD

No. of animals 8 8 Milk yield (kg/d) 1.31 1.35

FCM (4%) (kg/d) 1.60 1.54 Milk composition

(%) Fat 5.5 5.0 CP (Nx6.38) 4.2 4.1

Ash 0.9 0.9

Total solids 14.4 13.8

Concentrate 979 1007

intake (g/d)a

Initial weight (kg) 66.9 71.2

Final weight (kg) 59.3 63.8

Weight loss (g/d) 183 177

a Four individual observations per treatment.

8 8 8 8 _

1 s2 1.28 1.31 1.52 0.39

1.81 1.56 1.68 1 .I6 0.41

5.2 5.4 5.5 5.2 0.65 4.2 4.3 4.1 4.0 0.36

0.9 0.9 0.9 0.9 0.04

14.0 14.4 14.3 13.8 0.88

1067 916 984 1048 57

68.2 68.4 66.9 69.2 3.43

61.6 60.9 58.4 62.1 3.25

156 177 202 168 22.3

..\ , , , ( , , , , , r

0 1 2 3 4 5 6 7 B 9 10

Wdt

Fig. 1. Fat-corrected milk yield (kg/h/d) of goats on two sources

of protein (- untreated, - --- formaldehyde-treated soybean

meal) at three levels each (0 I3%, X 15%. * 18% CP in the concentrate mixture). Last 4 weeks, post-experimental period, all

animals on a similar diet.

3. Results

Treatment of soybean meal with formaldehyde resulted in a significant reduction (P < 0.001) of DM and CP degradability in the rumen (Table 3). The degradability of both sources was increased with advanced incubation interval.

Performance data are in Table 4. There were no dif-

ferences between protein source or level for milk yield, fat-corrected milk yield, milk composition and BW change. In all six treatment diets animals were suffering

a decline in milk yield (Fig. 1) and BW loss (Fig. 2) throughout the 42-d experimental period.

Dietary ME (MJ/head/d) intake of goats over the last week on trial (estimated to meet the total mainte-

55

Fig. 2. Weight changes of goats on two sources of protein (-

treated, - - - - formaldehyde-treated soybean meal) at three levels

each (0 13%, X 15%. * 18% CP in the concentrate mixture). Last 4 weeks, post-experimental period, all animals on a similar diet.

M. Hadjipanayiotou, A. Photiou /Small Ruminant Research 15 (1995) 257-263 261

Table 5 Rumen metabolites in Damascus goats on different levels ( 13, 15, 18% CP mix.) and sources (untreated, formaldehyde-treated soybean meal)

of dietary protein

C,, C,, CI, F 13 F 15 F IR SD

No. of animals

Total VFA (mmol/ 100 ml)

Molar proportion of

Acetic acid

Propionic acid

Butyric acid

Valerie acid

NH,-N (mg/ 100 ml)

Rumen pH

8 8 8 8 8 8 _

8.8 7.5 8.6 1.1 8.3 8.2 1.60

57.4 61.3 62.0 60.0 61.1 62.1 3.92 28.9 26.2 24.6 28.9 25.6 25.1 4.08 11.0 10.7 12.0 9.6 11.9 11.1 2.17 2.3 2.0 1.7 1.9 1.5 1.5 0.85

38 48 67 36 52 57 18.0 5.9 5.8 6.1 6.0 6.2 6.2 0.36

nance and 60% of the production requirements) was 12.25; during this period animals were loosing weight ( 105 ? 34 g/d) and producing 1.06 +0.38 kg milk of 5.55 + 0.7% butterfat. Increasing the daily feed allow- ance to 23.85 MJ ME/d resulted in an increase of milk (1.35 kg/head/d) produced over the 4-week post- experimental period (Fig. 1) Although the daily milk energy output was increased (last week on test 4.22 vs. 4.88 MJ GE/head/d) as a result of higher feed allow- ance, most of the energy input went on BW gain (daily BW gain 206 k 85 g/head).

Effect of protein source and level on rumen metab- olites is shown in Table 5. Overall, protein source did not affect rumen NH,-N concentration, ruminal pH and molar proportion of VFA. Goats on the 13% CP mix- ture had significantly lower (P< 0.001) rumen NH,- N concentration than those on the 15 and 18% CP mixture. Differences among diets for other metabolites were not significant (Table 5).

4. Discussion

Formaldehyde treatment of soybean meal reduced degradability of DM and CP in the rumen, which is broadly in agreement with the results obtained by Rooke et al. ( 1982)) Morgan ( 1985) and Hadjipana- yiotou ( 1992a). The amount of formaldehyde and the general processing procedure applied in the present study was similar to the one used by Hadjipanayiotou (1992b) where formaldehyde treatment reduced the degradability of CP in the rumen, but not in the entire digestive tract of Chios growing lambs, implying that soybean meal was not overprotected, and could show

positive effects associated with undegradable protein as outlined by Orskov et al. (1981).

Although the animals used in the present study were in a more advanced stage of lactation than those used by Robinson et al. (1974) and Orskov et al. (1987), this is not expected to affect the response to different sources and levels of dietary protein, since in all studies animals were in negative energy balance. Goats used in the present study were gaining BW (83 g/d) from

weaning to the commencement (50-91 d in milk) of the trial, implying that there were body reserves that could be mobilized as a result to protein supplements. Klopfenstein ( 1985) reported that responses to slowly degradable protein are more evident when they are fed with feedstuffs of low protein content. The fact that goats were on dietary protein levels below the NRC ( 198 1) recommended levels, therefore, would facili- tate the appearance of response to supplements. According to NRC ( 1981) the CP requirements of goats (minimal activity), based on their mean BW and FCM yields (Table 4), were 204, 205, 22 1, 203, 210 and 219 g CPlheadld. The actual CP intakes were below requirements by 71, 53, 34, 65, 57 and 38 gl head/d for diets C,,, C,,, Ci8, F,,, F,, and F,s, respec- tively, and increases in milk yield would be expected

as a result of increments of dietary CP intakes. Fat-corrected milk yield of animals was declining

(Fig. 1) and feed intake was decreasing with time (Fig. 3) because the animals were rationed to meet only 60% of the production requirements of the previous week. Due to the fact that animals were fed below require- ments they were loosing weight throughout the 6-week experimental period (Fig. 2). When they changed to a higher feed allowance (post-experimental period,

262

1300-

1200.

p11w-

s

i

glO-

900-

M. Hadjipanayiotou, A. Photiou /Small Ruminant Research 15 (1995) 257-263

0 12 3 4 5 6 7 6 9 10

Fig. 3. Concentrate intake by goats on two sources of protein (-

untreated, - - - - formaldehyde-treated soybean meal) at three lev-

els each (0 13%. x 15%, * 18% CP in the concentrate mixture).

week 7 to 10) milk yield was increased slightly (Fig. 1) ; the extra feed allowance was mainly directed towards weight gain, demonstrating that, when milk yield is adversely affected due to undernutrition, the later is not compensated via greater weight loss for the production of milk. Any decline in milk yield due to undernutrition can only be partially alleviated (Fig. 1) by a higher level of intake, the later directed mainly towards weight gain (Fig. 2).

The lack of effect of protein intake on the rate of loss of BW appears to conflict with the findings of Robinson et al. (1974), Sparrow et al. (1973), Orskov et al. (1977) and Orskov et al. (1987), but it is in line with those of Cowan et al. ( 198 1) and Kaim et al. ( 1987). Similarly, the results obtained from formaldehyde- treated (protected, less rumen degradable protein) soy- bean meal in the present study are in line with Sheehan and Hanrahan ( 1989), but differ from Orskov et al. (1987) where it appeared possible to increase milk yield by stimulating BW loss through giving protein supplements of low degradability to underfed cows. In line with previous studies with ewes and goats (Had- jipanayiotou, 1992a), there was no difference in milk composition of goats on untreated or formaldehyde- treated soybean meal.

In line with Kaim et al. ( 1987), protein concentra- tion and source, did not affect significantly the molar proportion of VFA. Rumen ammonia-N increased with

increasing dietary protein concentration, but there was no difference between the two sources of protein. The non-significant effect of treatment on rumen NH,-N concentration is at variance with the data of Crooker et al. ( 1983) and Folman et al. ( 1981), but in line with a previous study carried out in our Institute (Hadjipan- ayiotou, 1992a). It must be emphasized, however, that rumen NH,-N concentration is variable during the day. In the study of Crooker et al. (1983), formaldehyde- treated soybean meal resulted in less rumen NH,-N accumulation 2-3 h postfeeding than untreated soybean meal, but 6-7 h postfeeding formaldehyde treatment did not reduce NH,-N, presumably because other sources of nitrogen contributed proportionally more NH,-N to the rumen fluid ammonia pool than that con- tributed by the degradable soybean meal still in the

rumen. Regression analysis of milk yield, fat-corrected milk

yield, milk components, rumen NH,-N concentration and daily BW loss (I’) on dietary CP level (X) (within protein source) confirmed the findings of the analysis of variance. Increasing the level of dietary CP resulted in a significant increase of NH,-N in the untreated soya (b = 1.73, P < 0.007). A similar trend, although statis- tically non-significant, was observed in the untreated

soya (b=0.87, PcO.1). The findings demonstrated that any reduction in

energy supply below requirements will result in con- siderable reduction in milk yield, and that supply of a protein supplement of low degradability will not alle- viate reduction in milk yield through greater mobili- zation of body reserves and subsequent use for milk production.

Acknowledgements

The authors are grateful to M. Theodoridou, M. Karavia, Ch. Spanos and the staff of the Central Chem- istry Laboratory of the Agricultural Research Institute for skilled technical assistance. This study was sup- ported partly by FAO/IAEA, Vienna.

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