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Effect of castration and diet on performance and feed utilisation in Saanen goats

V.R.M. Muhikambele,1 LA. Mtenga,1 E. Owen,2 G.C. Kifaro,1
D.S.C. Sendalo,1 N.F. Massawe,1 S.M. Kiango1 and D.R. Nkungu1

1 Department of Animal Science and Production, Sokoine University of Agriculture
P.O. Box 3004, Morogoro, Tanzania
2 University of Reading, Department of Agriculture, Earley Gate
P.O. Box 236, Reading, Berkshire, RG6 2AT, UK

Abstract
Introduction
Materials and methods
Results
Discussion
References

Abstract

Growth performance, digestibility and water intake studies were conducted on growing Saanen male and castrate goats. The goats were either fed ad libitum a barley-based concentrate diet or lucerne pellets. There were little castration and diet effects from arrival to weaning. Males grew faster (222 vs 183 g/day), had a lower conversion ratio (3.13 vs 4.11 g DM/g gain) and higher dry-matter intake (751 vs 744 g/day) than castrates. However, in the 24.5 to 36.5 kg liveweight period, castrates were superior to male goats in most parameters studied. Digestibility coefficients were higher in the barley-based diet. Dry-matter intake as a percentage of live weight ranged from 2.51 to 3.86. Nitrogen was better retained in goats on barley concentrate. Goats consumed water at 8 to 12% of their live weight, higher values being for goats fed lucerne.

Introduction

There is scarce information on the effect of castration on growth rate and feed utilisation in goats. Differences in the rate of gain between castrates and intact males are unclear. In cattle and sheep, it has been conclusively shown that entire male animals grow faster and utilise feed better than castrated animals (Bradfield 1968; Hedrick 1968; Turton 1969; Field 1971; Price and Yeates 1971). In contrast with this view, Mackenzie (1970), working with British Toggenburg goats, concluded that castration makes full use of the meat potential of surplus goats as castrated goats grow faster and are heavier than entire male goats. In corroboration with this view Kyomo (1978) found that castrated Small East African goats were heavier than entire males from weaning to 72 weeks of age. However, Nitter (1975) found that male German Fawn breeds of goats grew faster than castrates, a conclusion also reached by Louca et al (1977) with Damascus goats. The potential for growth and feed utilisation in Saanen entire male and castrate goats based on concentrate and grass diets has not been documented. The aim of the present study was therefore to investigate the effects of castration and diet on performance of Saanen goats.

Materials and methods

Sixty male (entire) and six castrated British Saanen goats were used in an experiment to test the effect of castration (entire males vs castrates) and the diet (barley-based concentrate vs lucerne pellets) on growth performance and feed utilisation in a 2x2 factorial experiment. Animals were purchased from farmers at 2-3 days of age and were randomly allocated to the four treatments. Arrival weight was obtained by weighing the kids on the day of collection from the farms around Reading University (UK) where the experiment was conducted. Castration took place at 11+1 days of age using rubber rings. Besides the treatments, all kids were fed artificial milk (Denkavit Lamb 211) ad libitum from arrival to weaning at 35 days of age.

The barley-based concentrate and lucerne pellets were fed ad libitum. The barley diet consisted of milled barley, soybean meal, fish meal, molassine meal, ground limestone, salt and Isaac Spence minerals at 800, 100, 50, 30, 15, 4 and 1 g/kg dry matter, respectively. Each 1000 g of Isaac Spence minerals consisted of 105.5 g Ca, 34.7 g P, 97.9 g Na, 150.8 g Cl, 137.5 g Mg, 9.7g Fe, 0.8 g Mn, 0.13 g Co, 0.21 g I and 110,000 IU Vitamin D (manufacturer's specification). The barley diet was not pelleted. Lucerne was dehydrated, milled and pelleted at the Reading University Farm and measured 30 mm long and 10 mm thick. Animals were individually penned and water was available all the time. Animals were weighed weekly and dry matter intake was recorded.

Six entire male and six castrate goats from weaning to 24.5 kg live weight were randomly allocated to the two diets for digestibility, nitrogen utilisation and water intake studies. There was an 8-day collection period, during which daily intake of feed and water were measured. Faecal and urine outputs were also recorded. Faecal and urine samples were preserved according to Schneider and Flatt (1975). AOAC (1975) methods were used in analysing the chemical components of samples.

Results

The chemical analyses of the barley concentrate and lucerne diets are shown in Table 1. The two diets were almost isocaloric and isonitrogenous in content.

Table 1. Chemical composition of the diets (g/kg dry matter).1

Chemical composition

Barley concentrate Mean±SD

Lucerne pellets Mean±SD

Dry matter (g/kg air dry

900±4

900±12 weight)

Crude protein

199±3

199±5

Ether extract

27±1

26±1

Ash

65±5

98±1

Calcium

18±1

31±5

Phosphorus

4±0.3

2±0.8

Lignin

14±2

89±8

Energy (MJ/kg DM)

18.62±0.79

18.68±0.29

1 Mean of eight samples.

Table 2. Effect of castration and diet on performance of goats in different weight periods.1,2


Parameters

Castration

Diet

Male

Castrate

SED

Barley

Lucerne

SED

Weight from arrival to weaning


No. of animals

30

30


30

30



Weight at weaning (kg)

8.16

8.10

0.31

7.98

8.27

0.31


Daily DM intake (g)

184

182

10

183

183

10


Daily energy intake (MJME)

3.73

3.84

0.16

3.81

3.76

0.16


Growth rate (g/day)

130

125

10

124

128

10


FCR (g DM/g gain)

1.44

1.49

0.09

1.49

1.44

0.09

Weight from weaning to 24.5 kg


No. of animals

24

24


24

24



Weight at weaning (kg)

7.91

7.75

0.34

7.62

8.05

0.34


Actual weight at 24.5 (kg)

26.03

25.59

0.44

25.42

26.48

0.48


Age at 24.5 kg (days)

117

132

5.0**

118

131

5.0*


Daily DM intake (g)

751

744

30

605

830

30


Daily energy intake (MJME)

7.67

7.50

0.24

7.72

7.45

0.24


Growth rate (g/day)

222

183

9***

215

191

9*


FCR (g DM/g gain)

3.13

4.11

0.16**

3.13

4.39

0.16

Weight from 24.5 to 36.5 kg


No. of animals

12

12


12

12



Actual weight at 24.5 kg

25.29

25.02

0.32

24.94

25.37

0.32


(kg)




174

11.48

0.57


Actual weight at 36.5 kg

37.84

38.00

0.16

37.84

38.00

0.16

(kg)


Age at 36.5 kg (days)

194

184

9**

174

204

9**


Daily DM intake (g)

1094

1290

76**

1055

1334

76*


Daily energy intake (MJME)

10.99

12.69

0.59**

12.19

11.48

0.57


Growth rate (g/day)

185

234

21.7**

237

182

21.7*


FCR (g DM/g gain)

5.94

5.51

0.56

4.45

7.32

0.56

1 Animals on arrival weighed 4.0-4.45 kg
2 * = P<0.05;.* = P<0.01; *** = P<0.001.
Figures without asterisks are not significantly different P>0.05.

Castration and diet had no significant (P>0.05) effects on growth and feed utilisation from arrival at the University Farm (4±0.5 days of age) to weaning at 35 days of age (Table 2). From weaning to attaining 24.5 kg live weight, entire male goats grew (39±9 g/day) faster (P<0.001) than castrates. There was no effect (P>0.05) of castration on daily feed consumption, but because castrates took a longer time (16 days) to reach the target weight of 24.5 kg, they consumed more dry matter. Castrate goats were less (P<0.001) efficient in utilising their feed than entire male goats. Goats fed the barley concentrate diet grew (25 g/day) faster P<0.001) than those fed lucerne. Daily dry-matter intake was higher (P<0.001) in goats fed lucerne, but they utilised the feed less efficiently compared to goats on barley concentrate (P<0.001).

There was a change in male status effect on most characteristics studied in the 24.5 to 36.5 kg liveweight range. Castrate goats grew (49±21 g/day) faster (P<0.05) than the males. Castrate goats also ate more dry matter (P<0.05) and more but not significant (P>0.05) metabolisable energy. The trend in performance of goats fed barley concentrate within the 24.5-36.5 he, growth period was similar to earlier periods. Animals on barley concentrate grew faster by 55±22 g/day (P<0.05), ate less (1055 vs 1334 g) dry matter and slightly more (12.19 vs 11.48 MJ) metabolisable energy and utilised their feed more efficiently compared with those offered lucerne.

In general, digestibility coefficients were not affected by castration (P>0.05) although there was a tendency for castrates to exhibit lower digestibility coefficients (Table 3). However, differences in digestibility coefficients in favour of goats fed barley concentrate were significant (P<0.001). Goats on barley concentrate consumed dry matter which was equivalent to 2.51% of live weight while goats on lucerne consumed dry matter which was 3.86% of live weight.

Table 3. Digestibility as influenced by castration and diet.



Castration

Diet

Male

Castrate

SED

Barley

Lucerne

SED

No. of animals

6

6


6

6


Daily intake


Dry matter (9)

946

1056

74

775

1222

74***


DM (% live weight)

2.95

3.46

0.14*

2.51

3.86

0.14***


Gross energy (MJ)

17.62

19.59

1.38

14.43

22.78

1.38***


Crude protein (g)

185

206

14

154

236

14***

Digestibility coefficients (%)


Dry matter

68

66

0.9

77

58

0.9***


Organic matter

70

68

09

79

59

0.9***


Energy

69

67

0.9

78

58

0.9***


Protein

75

73

0.8

80

68

0.8***

* P<0.05;
*** P<0.001.

Goats fed barley concentrate were more efficient (P<0.001) in nitrogen utilisation than goats fed lucerne (Table 4). The differences between male and castrate goats were small (P>0.05). Castration had no effect on voluntary water intake (Table 4). Goats fed lucerne consumed more water (P<0.001) in absolute amount as a proportion of live weight and per kg dry matter. Lucerne fed goats consumed about one and a half times as much dry matter and about twice as much ash as consumed by goats fed the barley concentrate.

Discussion

Diets in the present study were formulated in such a way as not to be limiting in energy and protein according to nutrient requirements of growing dairy goats (Devendra and McLeroy 1982). It can be concluded that from birth to weaning, the growth rate of Saanen goats can range from 124 to 130 g/day while from weaning to 24.5 kg live weight and from 24.5 to 36.5 kg live weight, expected growth rate can range from 183 to 222 and 182 to 234 g/day, respectively. Similar growth rate values have been reported with other dairy goat breeds in Europe under intensive systems (Ladipo 1973 with a mixture of dairy goats; Nitter 1975 with German goats; Fehr et al 1976 with Alpine goats). Thus a great potential apparently exists for improving tropical breeds of goats by crossing with European breeds, provided proper consideration is given to management and feeding.

The influence of castration on pre-weaning growth rate was small and non-significant in agreement with the findings of Peters and Heaney (1974). Performance of kids was not influenced by dam milk yield as they were artificially reared. The performance characteristics in the weaning to 24.5 kg interval, in favour of males have been reported in other breeds of goats (Nitter 1975; Louca et al 1977) and in cattle and sheep (Turton 1969). This is attributed mainly to sex hormones (Turton 1969; Field 1971). The claim by Mackenzie (1970) and, more recently, by Kyomo (1978) that castrates grow faster than males is difficult to reconcile with the present findings.

An interesting and important aspect in the present study is the reduced growth rate observed for male goats in the 24.5 to 36.5 kg liveweight period which was accompanied by slight reduction in feed intake. Similar reduction in growth rate in male goats have been observed in Damascus goats (Louca et al 1977) and is attributed to breeding season effect which was in August to October in the present study. The observation that feed conversion ratio (FCR) in goats increases with increasing live weight (Fehr et al 1976; Louca et al 1977) is corroborated by the findings of this study.

The results tend to suggest that Lucerne-fed goats increased their dry matter intake in an attempt to sustain the same metabolisable energy intake as that of goats on barley concentrate, although they failed to compensate fully. During the weaning to 24.5 and 24.5 to 36.5 kg intervals daily dry matter intake was 37% and 26% more for Lucerne-fed than for barley-fed goats, respectively. The metabolisable energy concentration in barley was 33% greater than that in lucerne. However, the intake of the lucerne diet was so high that ME intakes from barley diets were only 4-6% greater than those from the lucerne diets. Digestibility coefficients of 0.75-0.82 have been quoted for barley diets, and 0.55-66 for lucerne (Ørskov et al 1974; Waiman 1977). These values are similar to those in the present study.

Voluntary food intake as percentage of live weight is a much used measure of intake capacity. The dry-matter intakes of 2.51-3.86% obtained in the present study are in agreement with those reported in other breeds of goats, as reviewed by Devendra and McLeroy (1982). The elevated proportion of nitrogen appearing in the urine and faeces of goats fed lucerne as reflected in less nitrogen retention is suggestive of a greater extent of formation of ammonium and other related non-protein nitrogenous substances in the rumen and hind gut which were absorbed and subsequently lost via the kidney and undigested protein.

Water intake increases with increase in dry matter intake (Anand 1961). The present study shows that the goat is no exception. It has been recommended that at environmental temperatures of 15°C and 15-20°C, water intake for growing lambs should be 2.00 and 2.50 kg/kg dry matter consumed, respectively (Devendra and McLeroy 1982). A similar value of 2.52-2.62 kg/kg dry matter was obtained in the present study for a mean temperature of 17°C. Higher water intake for goats fed lucerne in the present study may have been simply a reflection of higher dry matter and ash intakes by the animals.

Table 4. Nitrogen retention and water utilisation as influenced by castration and diet.


Parameters

Castration

Diet

Male

Castrate

SED

Barley

Lucerne

SED

No. of animals

6

6


6

6


Dry-matter intake (g/day)

946

1051

84

775

1222

84***

Ash intake (g/day)

76

89

7

50

115

7***

Nitrogen retention


g/day

9.20

10.66

1.07

9.97

9.89

1.07***


% intake

32.78

33.56

1.93

40.29

26.05

1.93***


% digested

43.19

44.99

2.65

49.94

38.25

2.65

Daily intakes


Water (kg)

2.58

2.76

0.05

1.53

3.82

0.05***


Water (kg/kg DM)

2.72

2.62

0.48

1.97

3.12

0.48***


Water (% live weight)

8.00

9.0

1.58

4.94

12.16

1.58***

*** = P<0.001.

References

Anand B.K. 1961. Nervous control of food intake. Physiological Review 41:677-708.

AOAC (Association of Official Analytical Chemists). 1975. Official Methods of Analysis. 12th edition. AOAC, Washington, DC, USA.

Bradfield P.G.E. 1968. Sex differences in the growth of sheep. In: Lodge G.A. and Lamming G.E. (eds), Growth and Development of Mammals. Butterworths, London, UK. pp. 92-108.

Devendra C. and McLeroy G.B. 1982. Goat and Sheep Production in the Tropics. Longman Group Ltd. London, UK. 271 pp.

Fehr P.M., Sauvant D., Delage J., Dumont B.L. and Roy G. 1976. Effect of feeding methods on performance of entire young male goats. Livestock Production Science 3:183-194.

Field R.A. 1971. Effect of castration on meat quality and quantity. Journal of Animal Science 32:849-858.

Hedrick H.B. 1968. Bovine Growth and Composition. Research Bulletin Monograph 928. Agricultural Experimental Station, Washington, DC, USA. 56 pp.

Kyomo M.L. 1978. Meat from Goats in Tanzania. PhD thesis, University of Dar es Salaam, Tanzania. 272 pp.

Ladipo J.K. 1973. Body Composition of Male Goats and Characteristics of their Depot Fats. PhD thesis, Cornell University, Ithaca, New York, USA. 343 pp.

Louca A., Economides S. and Hancock J 1977. Effects of castration on growth rate, feed conversion efficiency, and carcass quality in Damascus goats. Animal Production 24:387-391.

Mackenzie D. 1970. Goat Husbandry. 1 st edition. Faber and Faber, London, UK. 584 pp.

Nitter G. 1975. Preliminary results with intensive fattening of young goats. Animal Breeding Abstract 43(12):684. Abstract no. 5878.

Ørskov E.R., Fraser C. and Mchattie I.1974. Cereal processing and food utilization by sheep. Animal Production 18:85-88.

Peters H.F. and Heaney D.P. 1974. Factors influencing the growth of lambs reared artificially or with their dams. Canadian Journal of Animal Science 54:9-18.

Price M.A. and Yeates N T M. 1971. Infertile bulls versus steers. Journal of Agricultural Science (Cambridge) 77:307-311.

Schneider B.H. and Flatt W.P. 1975. The Evaluation of Feed through Digestibility Experiments. University of Georgia Press, Athens, Georgia, USA. 423 pp.

Turton J.B. 1969. The effect of castration on meat production from cattle, sheep and pigs. In: Rhodes D.N. (ed), Meat Production from Entire Male Animals. J & A Churchill Ltd. London, UK. pp. 1-50.

Wainman F. W. 1977. Digestibility and balance in ruminants. Proceedings of the Nutrition Society 36:195-201.


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