studies on the response of lactating damascus goats to dietary protein

The response of lactating Damascus goats on dietaty protein 41

BELLO, J.; CENARRUZABEITA, M. N.; LARALDE, J., 1972: Rev. Amin. Nutr. 10, 232-235. DAHLQUIST, A,, 1968: Methods in Enzymatic Analysis, 2nd edition. New York: Bergmeyer, editor. DROR, Y.; GENTLER, A,, 1969: J. Nutr. 93, 401-410. EVANS, R. J.; PUTZTI, W. B.; WATT, E. B.; BAUER, D. M., 1973: Biochem. Biophys. Acta 303, 175-185. FINLEY, J. N.; FELLER, 0. A,, 1973: Gereal Chem. 50, 210-214. HODGE, J. F.; HOFREITER, B. T., 1962: Methods in Carbohydrate Chemistry, Vol. I, Edited by Whistle, R. L.

& Miller, J. N. Academic Press, London & New York. HONAVAR, P. M.; SHIH, C. V.; LIENER, I. E., 1962: J. Nutr. 77, 113-115. HUGGET, 0. R.; NIXON, A. C., 1957: Arch. Venez. Nutr. 10, 183-185. HUPRIKA, S. V.; SOHONIE, K., 1965: Enzymologia 28, 333-340. JAFFE, W. G.; CAMEJO, G., 1961: Acta Cient Venezotara 12, 59-63. JAFFE, W. G.; VEGA, C. L., 1968: J. Nutr. 94, 203-206. JOHNSON, G.; JOHNSON, D. K.; LAMBERT, C.; SUNDERWITH, S., 1964: J. Agric. Fd. Chem. 12, 216-223. KABAT, E. A.; MAYER, M. M., 1961: Exptl. Immunochem. 3, 3-10. KORTE, R., 1973: Ecology, Fd. Nutr. 1, 303-306. LIENER, I. E., 1962: Am. J. Clin. Nutr. 11, 281-298. LIENER, I. E., 1980: Advances In Legume Science. Edited by Summerifield R. J. & Bunting, A. H., Academic

SNTIDRIAN, S., 1981: J. Anim. Sci. 53, 414-419. SIDDONS, R. C., 1969: Biochem. J. 112, 51-59. SIDDONS, R. C., 1972: Br. J. Nutr. 27, 343-352.

Press, New York, London.

Author’s address: Present Address: Department of Animal Production & Health, Federal University of Technology, PMB 704, Akure, Nigeria.

Agricultural Research Institute, Nicosia, Cyprus

Studies on the response of lactating Damascus goats to dietary protein

M. HADJIPANAYIOTOU

Receipt ofMs. 7. 3. 1986

Introduction

The progressive increase in the milk production of dairy cows has stimulated reevaluation of protein requirements for lactation (VERITE, JOURNET and JARRIGE 1979; ARC 1980). It is now widely accepted that digestible crude protein (DCP) is an inadequate measure of the protein value of feeds (ARC 1980). The DCP system is superseded by systems that account for the degradation of protein in the rumen, the efficiency of microbial protein synthesis and the supply of dietary protein to the small intestine.

U.S. Copyright Clearance Center Code Statement: J. Anim. Physiol. a. Anim. Nutr. 57 (1987), 41-52 0 1987 Verlag Paul Parey, Hamburg und Berlin ISSN 0044-3565

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42 M. Hudjijunuyiotou

Provision of protein supplements immediately after parturition has been used to enhance milk vield in dairy cows (FOLDAGER and HUBER 1979) and ewes (COWAN et al. 1981).

Considerable amount of data concerning goats comes from studies with inadequate nutrition, consistent with a low level of production were prevailing and their extrapolation to inten- sively fed highly producing animals is rather dangerous. Information about the effect of protein intake on the performance of dairy goats is very scarce. CISZUK (1980) reported somewhat higher nitrogen requirements for milk production in goats than cows. The present studies were undertaken to study the effects of different levels of dietary nitrogen intake on the performance of lactating Damascus goats at different stages of production.

Material and methods

Trial 1: Response of lactating Damascus goats to changes of protein

Twenty four Damascus goats were used. Following weaning of kids (56 day postpartum) all goats were offered 2.2 kg concentrate (180 g CP/kg DM) and 0.7 kg barley hay (75 g CP/kg DM) for a period of 10 days. Based on their 10 day postweaning milk yield, animals were divided into 12 pairs. The 12 pairs were then divided into high (HY), medium (MY) and low yielding (LY) groups. The animals within each pair were randomly assigned to two treatments at 66 days postpartum one with 140 g CP/kg DM (HP) and the other with 100 g CP/kg D M (LP). Half the animals received the HP diet during period I (PI) and the LP diet during period I1 (Pll); the others received the treatment (diets) in the reverse order. Each period lasted 16 days. Groups were fed to maintenance (0.401 MJ/kg" j 3 ) plus the appropriate milk production [Dietary ME (MJ) requirements per kg milk, equal to the energy in milk Y = 1.64 + 0.42X, divided by 0.62, where X = fat percentage]. Concentrate and roughage were fed from separate containers. Feed offered and refused were recorded daily. The three groups were offered different quantities of concentrates [2.15 (HY), 1.8 (MY) or 1.6 (LY) kg/goat/day] and of barley hay (64 g CP/kg DM) [0.90 (HY), 0.75 (MY) or 0.68 (LY) kg/goat/day]. The two levels of dietary CP concentration were made by feeding concentrates of varying CP content (Table 1). Goats were housed in individual pens with concrete floors bedded with wood shavings. Milk yield was recorded 5 days a week (Monday to Friday) and representative samples from morning and afternoon milking were bulked and analysed for fat, protein, ash and total solids as outlined by MAFF (1973). Goats were weighed before the morning feeding at the commencement and at the end of each experimental period. Blood samples were collected at the end of the second experimental period in a centrifuge tube, via jugular puncture. Blood samples were taken immediately before morning feeding and 3 h later. Blood serum was separated by the method of ARCHER (1965) and analysed for urea concentration colorimetrically (Urea kit-Bio Merieux, Charbonnieres-les-Bains, France). Rumen liquor samples were also taken 3 h following the morning feeding at the end of the 2nd experimental period by means of a tube passed into the reticulorumen via the oesophagus and suction created by a vacuum pump. Large quantities of rumen liquor (approx. 1 1) were obtained from each animal to eliminate contamination from saliva. Rumen liquor samples were strained immediately after collection through two layers of fine muslin and the pH was measured immediately. For rumen ammonia nitrogen, to 5 ml of the strained rumen liquor 5 ml of 0.2 N-HC1 were added. After mixing, the contents were centrifuged at 2,000 r.p.m for 10 min. Two ml of the supernatant were distillated in a buchi distillation apparatus after the addition of 4 ml of sodium tetraborate followed by a little

The response of lactating Damascus goats to dietay protein 43

distilled water. The distillate was collected in a 50 ml conical flask with 5 ml of 1% boric acid and 3 drops of mixed indicator and was then titrated with 0.01 N-HCI. Microbial protein in rumen fluid was measured using tungstic acid as protein precipitating agent and the differ- ential centrifugation technique (SHULTZ and SHULTZ 1970).

The experimental design was a two-period change-over design ( S E E G E R 1980) and data on milk yield and milk composition were analysed accordingly. Data for rumen NH,-N, pH and tungstic acid precipitable protein were analysed by two-way analysis of variance (treatments and groups) whereas data for serum urea by three-way analysis (STEEL and TORRIE 1960).

Trial 2: The effect of dietary protein concentration on milk yield and milk composition of Damascus goats and the performance of their kids

Forty-nine Damascus goats with their kids were randomly assigned to two diets three days postpartum. The two diets differed in their CP content (100 or 140 g/kg DM) and composed of a concentrate mixture (Table 1) and barley hay (80 g CP/kg DM). Concentrate allowance was increased gradually until it reached 2.2 kg per goat daily. Animals were also given 0.7 kg of barley hay. Goats were housed by treatment in adjacent pens of 9 to 12 goats per pen and fed

Table I

Individual feed ingredients (kg/tone) and chemical analyses (g/kg DM) of concentrates

Trial 1 Trial 2 Trial 3 ~ _ _ _

Ingredient HP LP HP LP C , S , , S , , SU,, SU,,

Barley grain 384 448 450 540 380 400 368 433 455.5 Sorghum grain 386 450 322 372 300 290 256 300 288 Corn grain

162 34 160 20 - 100 230 22 92 Soybean meal Carob-pod meal Urea + Wheat bran Dicalcium phosphate 5 5 5 5 3 3 3 3 3

Sodium chloride 3 3 Vitamin-trace element mix. * * Crude protein 168 127 168 120 118 173 208 172 226

+ One part (by weight) of Na,SO, was added19 parts urea *

230 129 95 165 95

69 60 30 49 30

50 50 50 50 - - - - -

, Limestone 10 10 10 10 15 15 15 15 15

- - - - - - - -

- 10 18.5 - - - - - -

3 3 3 3 3 3 3 * * * * * * *

Ash 45 48 69 53 42 48 54 52 48

A mineral-vitamin mixture (Vita 6, Vita-Trace Nutrition, Cyprus) was added to supply 6,000 I.U. vit. A, 1000 I.U. vit. D,, 8.5 I.U. vit. E, 25 mg Mn, 1.75 mg 1, 45 mg Zn, 30 mg Fe, 2 mg Co and 60 mg Mg per kg of concentrate mixture

on concentrates (5 mm cubes) and barley hay from separate containers. Feed residues were collected at least 3 times a week. Kids were allowed to suckle their dams continually from birth to 38 days of age, but only 8 h daily from 39 days to weaning (55 f 2 days). When kids were separated from their dams (16.00 to 08.00 h the following day) they had free access to concentrates (180 g CP/kg DM) and lucerne hay. Individual milk yields were recorded on 2 or 3 occas- sions between 12 and 38 days port partum and twice from 39 days to weaning (end of trial). The following milk recording procedure was followed in the continual suckling period: O n the day preceeding milk recording (recording day one) the kids were separated from their dams at

44 M. Hadjipanaytotou

15.00 h and all goats were milked by hand to standardize conditions in the udder. At 07.00 h the following morning all kids were weighed and allowed to suck for 15-20 min and then weighed again. The weight difference was recorded as milk consumption. They were then separated from their dams and allowed to suck at 15.00 h for 15-20 min and milk consumption was recorded. Following suckling, at 07.00 h and 15.00 h, goats were milked by hand and surplus milk was also recorded. Within one day from recording day one, surplus milk per goat was also measured o n one day (recording day two) without separating the,kids as follows: At 15.00 h goats were hand milked and kids were allowed to suck at will. O n the next morning (recording day two) the kids were separated for a short period (20-30 min) at 07.00 h and 15.00 h when goats were milked by hand and surplus milk was recorded. During the restricted suckling period (39-55 f 2 days), at 15.00 h o n the day preceeding the recording day one, all goats were milked by hand (kids had already been separated). At 07.00 h the following morning the goats were hand milked and milk yield was recorded. After milking, the kids were allowed to suck for 15-20 min and the weight difference was recorded as milk sucked. The kids were then separated and allowed to suck at 15.00 h for 15-20 min and milk consumption was again recorded. After suckling, any extra milk was removed by hand and recorded. In a regular daily routine all goats were milked by hand twice daily (07.00 h and 15.00 h) to remove any surplus milk not sucked by kids. Total daily milk was obtained by adding the surplus milk to the milk consumed by kids o n recording day one. Daily commercial milk yield per goat was obtained from the measurements of surplus milk o n recording day two without separation of kids. Milk consumption of kids was estimated as the difference of surplus milk from the total milk yield o f the goat o n recording day two. For twin kids, the proportion of milk sucked by kids o n recording day one was used for calculating the milk consumed by each kid on recording day two. Defaecation and urination between pre-and post-suckling weighings occured in some cases. Excretions were not measured however, and the amounts of milk sucked and total milk yields might be underestimated and possibly to a greater extent in the twin than single suckling goats. Using the test-day record as the central day, each period between recordings was divided into two equal parts, which were multiplied by the preceeding and following test-day record in estimating subtotals. Total performance was then the sum of these subtotals. The first recording was used to estimate milk performance from day 3 post-partum to the middle o f the first and second recording. Goats and kids were weighed at the beginning and at the end of the trial. Kids were aIso weighed on milk recording days. Samples from surplus milk were analysed for fat, protein and total solids as in trial 1. Kid performance data were analysed by least squares procedures (HARVEY 1975). Data o n goat performance were analysed by two-way analysis of variance (diets, number of kids suckling) (STEEL and TORRIE 1960).

Trial 3: Performance of goats given increasing levels of protein from soya or soya plus urea

Forty-five mature Damascus goats at the declining stage of lactation (90-120 days in milk) were divided into five groups o n the basis of their milk yield. The five groups were allocated at random onto five concentrate mixtures (Table 1). The five treatments were: one with no protein supplement (80 g CP/kg DM) and another two nitrogen levels (120 and 160 g CP/kg DM) supplied either by soybean meal (S) or soybean meal plus urea (SU). The concentrate mixtures which were offered along with 0.4 kg barley straw and 0.4 kg barley hay contained increasing nitrogen levels provided by soya o r soya plus urea. Goats were fed to maintenance plus the appropriate milk energy requirements (see Materials and methods, trial 1) . Animals were housed in 5 adjacent pens. Feed residues were recorded at least 3 times a week. Goats were

The response of lactating Damascus goats to dietary protein 45

weighed on two consecutive days prior to morning feeding at the beginning and at the end of the trial and the mean of the two consecutive days was used to calculate initial and final weight. Milk yield was recorded once a week and milk samples were analysed (MAFF 1973) for fat, protein and total solids once every fortnight. The trial lasted 42 days. Data collected were analysed by one-way analysis of variance (STEEL and TORRIE 1960).

Results

Trial I: The level of dietary protein had a significant effect (P < 0.05) on milk yield of goats (Table 2). Goats on the HP diet produced more fat corrected milk than those on the LP diet. Furthermore, in the second period, goats on the HP diet suffered a lower reduction in milk

Table 2

Production and rumen and blood characteristics of Damascus goats offered two levels of dietary protein (trial 1)

Treatment

HP LP SE Significance

Feed intake (g/day) Concentrate Barley hay

Fat corrected (4%) milk yield (kglday)

Milk composition (g/kg) Fat Protein

Serum urea (g/l)

Rumen PH NH, -N (mg/100 ml) TAP-protein (g/lOO ml)

Initial weight (kg) Final weight (kg)

NS Not significant * P <0.05 ** P<O.O1

1842 623

2.40

36.5 42.2

0.503

5.71 9.6 3.37

61.0 61.0

1844 636

2.29

36.5 41.1

0.375

5.90 4.6 2.44

60.5 60.9

4.6 8.0 0.033

1.08 0.48 0.023

0.08 1.22 0.07

0.42 0.30

- - *

NS * **

NS ** it

NS NS

(Fig. 1) than those on the LP diet (HP, -0.234 vs LP, -0.435 kg milk/day). Period had a significant effect on milk (P < 0.01) yield (P12.55; Pl,2.15 kg/day) and milk fat content (P < 0.05). Goats produced more milk of slightly higher fat content in (P138.0; P,,35.4 g/kg) the first period. In the first period, all groups (HY, MY and LY group) on high protein diet produced more milk than those on the low protein diet (Fig. 2). In the second period however, only goats on HY group and offered the HP diet produced more milk than those on the LP diet (Fig. 2). In the MY group there were no differences in milk yield between the two levels of protein (Fig. 2), whereas in the LY group, goats on the LP diet produced more milk than those on the H P diet (Fig. 2). Feeding a high protein did not affect the fat or total solids content of milk, but significantly increased (P < 0.05) the milk protein content and yield. Treatment did not affect liveweight changes (Table 2).

46 M. Hadjipanayioiou

change over

6 12 18 2 4 30 0

D a y s o n t r i a l

Figure 1. Daily milk yield of Damascus goats offered high (0-0) or low protein (0-0) diets.

Figure 2. Response to dietary protein (0-0) high protein; 0-0 low protein) of Damascus goats producing different amounts of milk.


Means for rumen pH and NH, and tungstic acid precipitable (TAP) protein concentrations are shown in Table 2. Increasing dietary protein concentration resulted in a significant increase of rumen NH, (P < 0.01), serum urea (P < 0.01) and TAP protein (P < 0.05) concentrations. Rumen pH values were similar in the two treatments. Serum urea was lower (P < 0.01) in the second compared to the first sampling (0.386 vs 0.522 g/l).

There was a low (r = 0.25) and non-significant correlation between TAP protein (g/100 ml) and rumen NH,-N (mg/100 ml) concentration (Y = 2.5628 + 0.03808X). TAP protein was correlated (r = 0.56, P < 0.05) with serum urea (g/l) (Y - 0.5061 + 1.1998X). Inclusion and of rumen NH,-N in the equation resulted in a higher correlation (r = 0.63, P<O.O5) (Y - O.O165X, 4- 1.0866X.J. Trial 2: Increasing level of protein intake improved significantly milk yield (P < 0.05) and milk protein (P < 0.01) content but did not affect fat or total solids content of milk (Table 3). Twin suckling goats produced more milk than single suckling (P < 0.001). Furthermore, twin suckling goats on the high protein diet produced more milk than those on the low protein diet (difference 0.54 kg/goat/day). The difference between dietary protein levels in daily milk yield between single suckling goats was only 0.27 kg. The level of protein concentration fed to goats did not affect significantly the growth rate of their kids. Type of rearing (single vs twin) had a significant effect (P < 0.05) on growth. Unlike males, single females were heavier than twin females at weaning and they grew faster during the period birth to weaning (Table 4). Trial 3: The actual C P content (g/kg DM) of the experimental diets was 101, 139, 162, 135, 183. Although milk yield of goats on the lowest C P diet was lower by about 0.2 kg/goat/day, differences were not statistically significant (Table 5) . Level of dietary protein did not affect milk composition or liveweight changes. Feed intake of goats was similar for all five diets.

Discussion

The actual CP (g/kg DM) of the finished rations (concentrate plus barley hay) calculated from the C P content of the concentrate mixtures (Table 1) and the C P of the barley hay was close to the proposed values (trial 1, HP 145.8, LP 115 g CP/kg DM; trial 2, HP 147.5, LP 110.6 g CP/ kg DM; trial 3, C 107.5, S , , 146.1, S,, 170, SU,, 145.9, SU,, 185 g CP/kg DM). The protein adequacy of a ration is a function of the content, quality, and solubility of its protein, as well as total ration consumption, milk yield and stage of lactation. The estimated dietary C P concentrations required, at optimum degradability (ARC 1980), to meet the nitrogen requirements were 118, 129 and 104 g/kg DM for trials 1, 2 and 3, respectively. Indeed, the C P content of the low C P diets could not supply sufficient amino acids for potential yield in trials 1 and 2, but it was adequate for trial 3. This could explain the non significant effect of added protein in trial 3 and the response to added protein in trials 1 and 2.

In the studies of ROBINSON et al. (1979) with lactating ewes, a fast response in milk yield was observed following a withdrawal, and subsequent re-introduction of the protein supplement in the diet. In the present studies (trial l), the milk yield of goats on both diets, decreased with time, but this could be partly attributable to the natural decline in milk yield. This decline in milk yield was, however, greater in the low compared to the high protein diet. In line with ROBINSON et al. (1979) a very short time was taken for the milk yield to respond to changes of dietary protein levels.

During early lactation, goats producing more milk exerted greater response to dietary crude protein than those producing less milk (trial 3). Similar findings have been reported for dairy cattle (BROSTER and BROSTER 1984) and lactating ewes (PAPAS 1977).

P

co

Tabl

e 3

Perf

orm

ance

of s

uckl

ing

Dam

ascu

s go

ats

offe

red tw

o le

vels

of

diet

ary

prot

ein

(tri

al 2

)

Trea

tmen

t

HP

LP

Suck

ling

regi

me

Sing

le

Twin

Si

ngle

Tw

in

SD

Sign

ific

ance

No

of g

oats

11

13

13

11

Feed

int

ake

(kg/

day)

C

once

ntra

te

Bar

ley

hay

Tota

l milk

yie

ld (

kg/d

ay)

Milk

suc

kled

(kg

/goa

t/day

) C

omm

erci

al m

ilk y

ield

(kg

/goa

t/day

)

1.93

2 0.

587

1.83

0 0.

565

2.39

3.

46

2.12

2.

92

0.55

1.

36

2.67

1.

31

2.31

0.

42

1.03

0.

79

0.82

0.

61

0.40

Milk

com

posi

tion

(g/k

g)

Fat

37

39

38

40

Prot

ein

40

40

37

35

Ash

8.

3 8.

4 8.

5 8.

1 To

tal s

olid

s 12

5 13

1 12

9 12

8

9.7

3.1

0.4

9.5

Live

wei

ght

at k

iddi

ng (kg

) 55

.6

53.4

51

.1

55.3

10

.4

Live

wei

ght

at w

eani

ng (

end

of tr

ial)

(kg)

55

.7

52.5

51

.0

50.4

8.

1

NS

not

sign

ifica

nt

T le

vel

of p

rote

in e

ffec

t P <

0.05

TT

T le

vel

of p

rote

in e

ffec

t P <

0.00

1 SS

ty

pe o

f su

cklin

g ef

fect

P <

0.01

SS

S ty

pe o

f su

cklin

g ef

fect

P <

0.00

1

T, ss

ss

s NS

NS

TTT

NS

NS

NS

NS

The response of Iactating Damascus goats to dietary protein 49

Table 4

Performance o f kids reared on goats offered two levels o f dietary protein (trial 2)

Treatment

HP LP

Suckling regime Single Twin Single Twin

Sex M ' F' M F M F M F S.D.

- No. of kids 7 5 13 13 6 7 12 10 Birth weight (kg) 4.6 4.4 4.7 4.0 4.4 4.3 4.4 3.9 0.58 Weaning weight (kg) 13.7 14.2 14.1 12.1 13.2 13.8 13.3 11.7 2.19 Daily gain (birth toweaning)(g) 167 178 147 146 159 173 154 141 30.0

Milk sucked (kg/kid) 65 80 73 70 60 77 63 63 15.9

' M: males, F: females

Table 5

Production characteristics o f goats given increasing protein concentrations from soya (S) or soya plus urea (SU) (trial 3)

Proposed crude protein concentration (%)

8 12 16 12 16 SD Nitrogen supplement Control S S su su

- No. of animals 9 9 9 9 9 Milk yield (kg/day) 1.53 1.70 1.73 1.73 1.71 0.5 1

Milk composition (g/kg) Fat 39 40 39 36 39 5.9

Ash 8 8 8 8 8 0.3 Total solids 127 126 128 124 129 6.8

Crude protein 41 29 42 42 41 3.3

Weight gain (kg/day) 0.08 0.06 0.04 0.07 0.03 0.08

Feed intake (kg/day) - Concentrate 1.51 1.51 1.52 1.52 1.51

Roughage 0.58 0.61 0.64 0.60 0.59 -

Levels of protein that are appreciably below standards lead to a decline not only in milk yield but aIso in milk protein concentration (ARMSTRONG and PKESCOTT 1971). WHITING, SLEN and BEZEAU (1952) noted a significant effect on milk composition of ewes when the dietary C P was reduced to 7%, whereas ROBINSON et al. (1974) reported no increase in milk protein content when the dietary C P was above 103 g/kg DM. In the present studies, feeding diets with more than 100 g CP/kg feed DM resulted in higher milk protein concentration (trials 1 and 2) supporting the fact that, protein requirements in trials 1 and 2 were higher than 100 g/kg DM. O n the other hand, this amount of protein was adequate at lower level of production (trial 3).

In line with TREACHER (1977), MAXWELL et al. (1979) HADJIPANAYIOTOU and ECONOMIDES (1986) with ewes and HADJIPANAYIOTOU (1986) with goats, goats suckling two kids produced more milk than single suckling goats. Twin suckling goats responded to a greater extent to high protein intake (HP, difference between twin suckling and single suckling 0.54 kg/goat/day; LP,

50 M. Had/ipanayiotou

difference 0.27 kg/goat/day). The differences in growth rate between single and twin suckling females but not in males can be ascribed to differences in milk consumption. There is no explanation however, for the higher milk intake of females compared to the males.

Serum urea nitrogen levels reflected dietary nitrogen levels in agreement with the data of HADJIPANAYIOTOU (1982) with lambs and BYERS and MOXON (1980) and THOMPSON and RILEY (1980) with cattle.

Conclusions

Based on the present studies it can be concluded that goats at the declining stage o f lactation and producing about 1.7 kg milk daily require a diet containing a maximum of 100 g CP/kg feed DM, whereas those producing 2.4 kg or more require at least 140 g CP/kg feed DM.

Summary

Three trials were conducted using lactating Damascus goats. In trial 1, 24 goats (70 days in milk) in a two-period change over design experiment, were offered diets with either 100 or 140 g CP/kg feed DM. Goats on the high protein (HP) diet produced more (P < 0.05) fat corrected milk o f higher protein content than those on the low protein (LP) diet (HP: 2.40; LP: 2.29 kg/goat/day). Feeding a H P diet did not affect the fat or total solids content of milk but had a significant effect o n rumen NH,-N (P < 0.01), serum urea (P < 0.01) and tungstic acid precipitable protein (P < 0.05) in the rumen liquor. In trial 2, 49 Damascus goats, with their kids, were randomly assigned to two diets (100 or 140 g CP/kg feed DM) 3 days postpartum. Increasing the level of dietary protein improved significantly milk (HP: 2.95 vs LP: 2.49 kg) yield (P < 0.05) and milk protein (HP: 40 vs LP: 36 g/kg) content (P < 0.01), but did not affect fat or total solids content of milk. Twin suckling goats produced more milk than single suckling (twin 3.21, single 2.25). The level of dietary protein fed to goats had no effect on the growth rate of kids. Single suckling kids grew faster (P < 0.05) than twin suckling. In trial 3,45 goats (90-120 days in milk) were allocated at random onto five treatment diets. The 5 diets were: one diet with no protein supplement (80 g CP/kg feed DM), two protein supplemented diets with soybean meal at two nitrogen levels (120 and 160 g CP/kg feed DM) and two soybean + urea supplemented diets (120 and 160 g CP/kg feed DM). The CP content of the actual ration was (101, 139, 162, 135 or 177 g CP/kg feed DM) higher, due to the fact that animals were leaving residues of feeds o f lower CP content. Although milk yield o f goats on the lowest CP diet was lower by about 0.2 kg/goat, differences were not significant. Based on the present studies, it may be concluded that goats producing around 1.7 kg milk daily require a diet containing a maximum of 100 g CP/kg feed DM, while those producing above 1.7 kg milk require a diet with more protein. Finally, judging from the greater response obtained in trial 2, it might be suggested that a diet with at least 140 g CP/kg feed DM might be necessary for goats producing above 2.4 kg milk daily.


Zusammenfassung

Untersuchung iiber den Einflufl des Rohproteingehaltes in der Ration bei laktierenden Damaskus-Ziegen

Es werden die Ergebnisse von 3 Versuchen mit laktierenden Damaskus-Ziegen berichtet. Im ersten Versuch wurden in zwei Versuchsperioden Futtermischungen rnit 100 oder 140 g

RP/kg TS an 24 Ziegen ab dem 70. Laktationstag gefuttert. Ziegen, die die Ration rnit 140 g RP (HP) erhielten, produzierten mehr fettkorrigierte Milch

(P < 0.05) mit hoherern EiweiBgehalt als Ziegen bei Rationen (LP) rnit niedrigerern RP-Gehalt (HP: 2,40; LP: 2,29 kg taglich). Die Verfutterung der HP-Ration hatte keinen EinfluR auf den Trockensubstanzgehalt der Milch, beeinflugte jedoch signifikant die N-Konzentration im Pansen (P < 0.01) den Serumharnstoffgehalt (P < 0.01) und das durch Wolframsaure fallbare Protein in der Pansenflussigkeit (P < 0.01).

Im 2. Versuch wurden 49 Ziegen mit ihren Lammern am 3. Tag post partum auf zwei Fut- terrationen mit 100 bzw. 140 RP/kg TS zufallig verteilt. Die hohere EiweiBkonzentration im Futter erhohte signifikant die Menge (HP: 2,95; LP: 2,49 kg taglich; P < 0.01) und den Protein- gehalt der Milch (HP: 40; LP: 36 g/kg; P < 0.01), hatte aber keinen EinfluR auf den Gehalt an Fett und Trockensubstanz. Ziegen mit Zwillingslamrnern produzierten mehr Milch als rnit nur einem Lamm (3.21 bzw. 2.25 kg taglich). Die Wachstumsrate der Ziegenlamnier blieb von der EiweiBkonzentration im Futter ihrer Mutter unbeeinfluBt. Einlinge wuchsen jedoch schneller als Zwillinge (P < 0.01).

Im 3. Versuch wurden 45 Ziegen vom 90.-120. Laktationstag zufallig auf die folgenden 5 Behandlungen verteilt: eine Ration ohne Eiweifierganzung (80 g RP/kg TS), zwei Rationen erganzt rnit Sojaschrot auf 120 bzw. 160 g RP/kg TS und zwei Rationen erganzt rnit Sojaschrot und Harnstoff auf 120 bzw. 160 g RP/kg TS. Die Eiweisgehalte der verzehrten Rationen belief sich auf 101 bzw. 139, 162, 135 und 177 g RP/kg TS, weil die Tiere Futterreste zuriicklieBen, die einen niedrigeren EiweiBgehalt aufwiesen. Obwohl die Milchproduktion der Ziegen bei der Ration rnit dem niedrigsten RP-Gehalt urn 0.17 bis 0.20 kg taglich niedriger waren, konnten diese Differenzen nicht statistisch gesichert werden.

Auf Grundlage dieser Ergebnisse la& sich sagen, dai3 Ziegen mit einer Tagesproduktion von etwa 1.7 kg Milch maximal 100 g RP/kg TS benotigen, wahrend Ziegen rnit hoherem Produktionsniveau auch entsprechend mehr Protein brauchen. Von der Erhohung der Milch- menge im Versuch 2 konnte man ableiten, daB Ziegen, die taglich mehr als 2.4 kg Milch geben, wenigstens 140 g RP/kg TS brauchen.

Acknowledgements

The author is greatful to G. HADJIGAVRIEL, L. HADJIPARASKEVAS, G. KYPRIANOU, A. PHOTIOU, M. THEODORIDOU, N. PAROUTI and M. KARAVIA for skilled technical assistance. This work was partly supported by the International Atomic Energy Agency, Vienna.

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Aufhors’ address: Agricultural Research Institute, Ministry of Agriculture and Natural Resources, Nicosia, Cyprus.

N~t iona l lnstitwtr’ of Animal Science Department of Animal Physrolop and Biochemistry Copenhugen, Denmark

The influence of dietary concentration of amino acids on protein and energy utilization in growing rats and piglets

3. Diets o f high biological value but with different protein concentrations

By B. 0. EGGUM, A. CHWALIBOG and V. DANIELSEN

Receipt of Ms. 18. 3. 86

1 Introduction

In earlier investigations with piglets, in the same series, by EGCUM et al. (1985a) it was shown that the performance was significantly reduced when dietary protein concentration in traditi- onal diets for piglets was lowered even if diets with reduced protein content were balanced

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studies on the response of lactating damascus goats to dietary protein

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