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Effect of feed supplements on weight gain and carcass characteristics of intact male Mubende goats fed elephant grass (Pennisetum purpureum) ad libitum in Uganda

K.L. Okello,1 C. Ebong2 and J. Opuda-Asibo3

1 Department of Veterinary Physiological Sciences, Makerere University
P.O. Box 7062, Kampala, Uganda
2 National Agricultural Research Organisation, Namulonge
3 Department of Veterinary Public Health and Preventive Medicine
Makerere University, P. O. Box 7062, Kampala, Uganda

Abstract
Introduction
Materials and methods
Results and discussion
Conclusion
References

Abstract

Twenty intact male Mubende goats were randomly divided into five groups of four goats each. Each group was randomly assigned one of the treatments resulting into a complete randomised design. All the animals were individually fed elephant grass (E), used as basal diet, ad libitum. Treatments were isonitrogenous amount (10 g N/d) of banana peels (BP), maize bran (MB), cottonseed cake (CSC) and fresh Leucaena leaves (LL) offered as supplements. Water and mineral blocks were offered ad libitum. At the end of the feeding trials (186 days), the goats were sacrificed for carcass analysis and the various body parts and organs were measured. Final live weights did not differ significantly between treatment groups (P>0.05) although goats fed on CSC were heavier than the rest. Empty body and dressed carcass weights differed significantly (P<0.05) in goats fed on different diets. Dressing percentage in goats fed LL, MB, and CSC were similar and significantly higher (P<0.01) than in goats fed on BP and E alone. The pH of the carcass was similar across all treatments. Weights of the head, full gut, empty gut, blood, kidney, and omentum fats did not differ significantly (P>0.01); however, weights of skin, pluck and feet differed significantly (P<0.01). Various carcass components were highly correlated with live weight across all diets suggesting that all the diets did not severely alter the allometry of growth.

Introduction

The economic importance of goats in the provision of animal proteins in developing countries has been extensively reviewed elsewhere (Devendra 1981). Meat from small ruminants accounts for almost 30% of the meat consumed in Africa (Reed et al 1988). In Uganda, goats provide about 23% of the total red meat produced and goat meat ranks second only to beef in sales. However, in terms of palatability and delicacy, it is preferred to beef. It is possible that goats could play a leading role in the provision of animal proteins to supplement other sources such as from beef chicken, pork and fish.

Goats are produced in Uganda using traditional practices where goats are either tethered or left to roam, browsing and grazing on whatever they can find (Okello and Obwolo 1984). The main feed resources for goats are natural pastures consisting of legumes and browse tree species. During the dry season, grazing land is scarce and pastures are deficient in energy, proteins and minerals. This is aggravated by lack of alternative feed during this critical period (Okello and Obwolo 1984).

In Uganda banana peels (BP), crop residues, cottonseed cake (CSC) and maize bran (MB) (agro-industrial by-products) can supply readily fermentable carbohydrate and energy needed for increasing growth rate in goats. Due to their low fibre contents they can be consumed in adequate quantities to also meet the nitrogen requirement for the growing goat without need for additional supplementation.

A study was initiated to evaluate BP, MB, CSC and Leucaena (LL) as supplements to elephant grass (E) in goat production. The evaluation included chemical analysis of feeds and carcass study.

Materials and methods

Twenty young intact male Mubende goats (4-6 months of age) purchased from a market in Kampala were used. Each goat was identified with a numbered ear tag and individually confined in a metabolic cage with a slatted floor. All animals were given prophylactic treatments for endo- and ectoparasites. They were given 14 days for adaptation to respective diets before the beginning of data collection. The goats were randomly divided into five groups of four goats each. Each group was randomly assigned one of the five dietary treatments resulting into a complete randomised design. Treatments were isonitrogenous amount (10 g N/d) of BP, MB, CSC and LL offered as supplements to E which was the basal diet fed ad libitum to all animals. The control group had no supplement. Water was available ad libitum and each animal had access to a mineral block.

Proximate analysis

Samples of feeds were dried at 60°C for 48 hours in an oven. The dry samples were ground to pass through a 2 mm screen. A 0.5 g portion of each sample in duplicate was analysed according to AOAC (1980). Neutral-detergent fibre (NDF) and ash were determined according to Goering and Van Soest (1970).

Intake and growth

Feeding commenced at 0800 h and collection of feed refusals was done 24 h later. Feed offered and refusals from each animal were weighed. Samples of each diet were taken for subsequent dry matter determination and chemical analysis. Intake was calculated as the difference between feed offered and refused corrected for dry-matter content.

Each goat was weighed at the beginning of the experiment and every successive seven days thereafter. Average daily gains (g/d) were calculated as differences between final and initial body weights divided by number of days of feeding.

Carcass analysis

At the end of the feeding trials (186 days), the goats were sacrificed. Before slaughter, live weight and skin thickness were measured; body condition score was assessed according to Pettit et al (1988). The animals were decapitated and blood was drained into a bucket and the weight of blood was measured.

The decapitated animals were flayed by gentle tearing of skin from the carcass to ensure that fat and muscle tissues did not adhere on to the skin. The legs were cut at the fetlock joints. Weights of skin, head and legs were measured and carcass value was assessed on the scale 0-3 as follows: 0 = emaciated carcass, 1 = lean carcass, 2 = moderate fatty carcass and 3 = full fatty carcass. The carcasses were eviscerated and the gut and pluck were removed and weighed. Omentum was carefully removed and weighed. The gut content was removed by flushing the gut with running water. The empty gut and dressed carcass were weighed separately. Kidney fat with capsule was removed and weighed. Thickness of brisket fat and longismus dorsi muscle and pH of the carcass were measured.

Table 1. Chemical composition of feed ingredients offered to intact male Mubende goats fed elephant grass ad libitum as basal diet.


Feed

Dry matter (g/kg)

Dry matter (g/kg)

Nitrogen

NDE*

Ether extract

Ash

Elephant grass (E)

288.0

15.6

551.1

35.0

90

Banana/peels (BP)

133.2

11.0

449.1

42.5

69

Maize bran (MB)

856.7

15.6

393.0

45.0

44

Cottonseed cake (CSC)

885.5

34.4

462.1

78.0

140

Leucaena leaves (LL)

314.0

30.4

479.3

29.0

76

* NDF = neutral-detergent fibre.

Statistical analysis

The difference in feed intake, average daily gain and carcass components were examined by analysis of variance for a complete randomised design using the STATGRAPHICS statistical package. Differences between means were compared using Duncan's multiple range test. Body and carcass cutting relationship with live weight were examined by simple linear regression analysis of variance.

Results and discussion

The chemical composition of the feeds in Table 1 indicate that high moisture and low protein contents rank banana peels as the least favourable diet for ruminants. Low dietary protein content inhibits rumen microbial activity with resultant low intake of roughage and sub-optimal supply of protein to the animal. In this respect elephant grass and maize bran are marginally below the critical level (1.6 g N/100 g) of dry feed nitrogen required for proper rumen function (Elliot and Topps 1963).

Intake

Table 2 summarises the voluntary feed intakes of animals in the different treatment groups. Dry-matter intake is an important factor in the utilisation of roughage by ruminant livestock and is a critical determinant of energy intake and performance in small ruminants (Devendra and Burns 1983). Further more it is important that feed supplements should not adversely affect intake of basal roughage diet. Goats fed the control diet consumed the highest amounts of the basal diet. The lack of significant differences in total dry-matter intake indicates strong substitution of the basal diet by the supplements.

Growth

Low growth rate is acknowledged to be the major limiting factor in goat production and the plane of nutrition can markedly improve weight gain; the degree of response varies with breed or type (Devendra and Burns 1983). In this experiment goats fed on leucaena leaves supplement and elephant grass alone lost weight with negative growth rates of -3.8 g/d and -3.2 g/d, respectively (Table 4). Digestible organic matter intake indicates that energy was limiting on the growth of these animals (Table 2). The negative growth rates recorded by goats fed on elephant grass alone was attributed to the insufficient amount of energy and protein in the grass. Meanwhile goats fed on maize bran supplement virtually maintained weight indicating that they received only adequate nutrient for maintenance. The best growth rate of 30.1 g/d was recorded in goats fed the cottonseed cake supplement. This feed supplement provided energy and protein which are critical for the growth of goats. The growth rate, however, is lower than values obtained (91 g/day) in Uganda by Wilson (1958) but it is similar to values obtained in West African Dwarf goats (Zemmelink et al 1985; Reynolds 1989). Ademosun et al (1985) also recorded growth rates that were higher than values obtained in this experiment.

Table 2. Intake (g/d) in male intact Mubende goats fed on ad libitum elephant grass (Pennisetum purpureum) with or without supplements of Leucaena luecocephala leaves, maize bran, banana peels and cottonseed cake.

Diets

Parameters

Leucaena leaves

Maize bran

Banana peels

Cottonseed cake

Elephant grass

SEM

Significance

Elephant grass

335±21.0bc

311±17.5c

356±11.0b

336±12.5bc

404±160a

7.1

**

Supplement intake (DM)

119±14.5b

222±44.9a

127±41.8b

175±25.9ab


13.6

***

Total dry-matter intake

454±33.8

533±57.7

483±50.0

511±270

404±16.0

17.6

ns

Total organic-matter intake

353±31.4

43944.6

445±46.5

470±25.0

370±14.8

15.3

ns

ns = P>0.05;
* = P<0.05;
** = P<0.01;
*** = P<0.001.
Values with the same superscript in a row do not differ significantly.

Table 3. Regression coefficients (y= a+bx) of body part and carcass components in intact male Mubende goats.


Body part

Regression coefficients

a

b

r2

Significance level

Empty body weight

-2.02

0.86

0.905

***

Head weight

0.4

0.04

0.586

***

Skin thickness

0.2

0.00125

0.066

ns

Feet weight

0.2

0.02

0.638

***

Pluck weight

-9.5

0.04

0.716

***

Dressed carcass

2.2

0.55

0.891

***

Full gut weight

2.0

0.18

0.283

**

Empty gut weight

-0.02

0.18

0.282

**

Longismus dorsi thickness

0.7

0.04

0.209

*

Testicular circumference

12.25

0.05

0.475

**

Gut content

2.03

0.17

0.283

*

ns = P>0.05;
* = P<0.05;
** P<0.01;
*** P<0.001.

Carcass characteristics

Body condition score and carcass value were subjective assessment. Condition score reflects subcutaneous fat deposits which is lower in goats than in sheep (Naude and Hofmeyr 1981). It also reflects muscular development and coverage of the ribs. Similarly carcass value was assessed according to visible subcutaneous fat coverage and leanness of the meat. Body condition score and carcass value were better in goats fed on maize bran and cotton seed cake. These findings were reflected in the objective measurements of fat deposits in the omentum, kidney and brisket as well as in the thickness of the longismus dorsi muscle.

Empty body weight and dressed carcass weight are functions of live weight (Fehr et al 1976). Table 3 shows that various carcass components and body parts (except skin thickness) were highly correlated with live weight across all diets, suggesting that all the diets did not severely alter the allometry of growth. Goats fed on cottonseed cake and maize bran produced dressed carcasses which were significantly heavier (P<0.01) than carcasses from goats fed on the other three diets (Table 4). These differences were associated with differences in fat deposits in the omentum, kidney and brisket.

Table 5 shows that gut contents in goats fed on elephant grass with Leucaena leaves were higher than those of goats fed the other diets. The least gut contents were those of goats fed maize bran.

Goats fed maize bran and cottonseed cake were heavier than the rest and they also had the heaviest legs and skin, suggesting that the two components were functions of final body weight. It was observed that goats fed on cottonseed cake and maize bran had more omentum and kidney fats.

Table 4. Body weight, carcass characteristics and meat pH of intact male Mubende goats fed elephant grass with or without supplements.


Parameters

Diets

E

LL + E

MB + E

BP + E

CSC + E

SEM

Significance level

Body-weight gain (kg)

-0.6±0.9b

-0.7±0.7b

1.2±1.7b

2.2±1.8b

5.62±1.5a

0.6

*

Body condition score

1.3±0.3b

1.0±0.0b

1.5±0.3b

1.3±0.7b

2.5±0.3a

0.14

*

Carcass value

1.0±0.0b

1.0±0.0b

1.5±0.3b

1.3±0.7b

2.5±0.3a

0.13

*

Empty body weight (kg)

10.4±0.7b

11.6±0.4b

14.3±1.3a

11.5±0.9b

16.8±1.9a

0.53

*

Dressed carcass weight (kg)

5.6±0.4b

6.6±0.3b

8.4±0.9a

6.1±0.6b

9.5±1.1a

0.33

**

Dressing percentage

53.5±1.2b

56.7±0.6a

58.5±1.4a

53.0±0.2b

57.0±0.7a

0.53

**

Carcass pH

6.0±0.2

6.6±0.2

6.0±0.4

6.4+0.1

5.90.3

0.11

ns

ns - P>0.05;
* = P<0.05;
** = P<0.01.
Values with the same superscript in a row are not significantly different (P>0.05).
E = elephant grass;
LL = Leucaena leaves;
MB = maize bran;
BP = banana peels;
CSE = cottonseed cake;
SEM = standard error of means.

Table 5. Weights of organs, body parts, omentum and kidney fat, gut content and blood of intact male Mubende goats fed on elephant grass with or without supplements.


Parameters

Diets

E

LL + E

MB + E

BP + E

CSC + E

SEM

Significance

Head weight (kg)

1.01±0.04

1.20±0.04

1.24±0.09

1.0±0.05

1.33±0.15

0.04

ns

Skin weight (kg)

0.94±0.07c

0.93±0.03c

1.25±0.12b

0.92±0.09c

1.51±0.13a

0.04

**

Feet weight (kg)

0.48±0.03bc

0.53±0.03b

0.63±0.01a

0.45±0.03c

0.60±0.05a

0.01

**

Pluck weight (kg)

0.55±0.06c

0.58±0.03c

0.74±0.06b

0.60±0.03c

0.88±0.08a

0.03

**

Full gut weight (kg)

5.01±0.24

6.04±0.46

4.33±0.55

5.05±0.10

4.84±0.91

0.25

ns

Empty gut weight (kg)

1.24±0.11

1.23±0.04

1.54±0.15

1.58±0.12

1.79±0.27

0.07

ns

Gut content weight (kg)

3.78+2.00b

4.81±0.43a

2.79±0.42c

3.47±0.07bc

3.05±0.66bc

0.19

*

Blood weight (kg) (kg)

0.60±0.9

0.64±0.02

0.75±0.05

0.65±0.03

0.86±0.13

0.04

ns

Kidney fat weight (g)

21.4±7.8

23.8±7.5

167.5±44.4

90.3±30.5

237.5±123.3

28.3

ns

Omentumfat weight (g)

36.1±17.2

37.0±7.0

342.8±103.5

146.3±65.2

405.0±196.2

48.3

ns

ns = P>0.05;
* = P<0.05;
** = P<0.01.
Values with the same superscripts in a row do not differ significantly.
E = elephant grass;
LL = Leucaena leaves;
MB = maize bran;
BP = banana peels;
CSE = cottonseed cake;
SEM = standard error of the means.

Table 6. Skin, brisket fat and longismus dorsi muscle thickness (cm) and testicular circumference (cm) of intact male Mubende goats fed on elephant grass with or without supplements.


Parameters

Diets

E

LL+E

MB +E

BP+E

CSC+E

SEM

Significance

Skin

0.22±0.01

0.22±0.01

0.23±0.01

0.23±0.01

0.21±0.01

0.00

ns

Brisket fat

0.71±0.22bc

1.39±0.29a

1.20±0.10ab

1.64±0.21a

0.66±0.04c

0.10

*

Long.dorsi muscle

1.23±0.16b

1.44±0.09ab

1.33±0.18b

1.64±0.04a

0.99±0.01c

0.05

**

Testicular Circumference

19.25±0.75bc

20.50±0.79b

19.67±1.20bc

23.88±0.43a

18.38±0.38c

0.32

***

ns = P>0.05;
* = P<0.05;
** = P<0.01;
*** = P<0.001.
Values with the same superscripts in a row do not differ significantly.
E = elephant grass;
LL = Leucaena leaves;
MB = maize bran;
BP = banana peels;
CSE = cottonseed cake;
SEM = standard error of means.

pH normally indicates the keeping quality of the meat. Lack of significant differences between treatment groups suggests that keeping quality was not affected by the different feeds.

Testicular circumference was bigger in goats that were fed on cottonseed cake and maize bran. Regression analyses of measurements of body parts on the live weight were highly correlated, suggesting that the apparent dietary effect on testicular circumference was associated with difference in live weight of the goats fed on the different diets.

Conclusion

The critical nutrients for enhancing growth of goats seem to be sufficient amounts and the right combination of energy and protein. In this respect maize bran and cottonseed cake seem to be better feed supplements in providing these nutrients. These agro-industrial by-products are abundant in Uganda and their use will greatly increase meat production from goats.

References

Ademosun A.A., Bosman H.G. and Roessen P.L. 1985. Nutritional studies with West African Dwarf goats in the humid zone of Nigeria. In: Wilson R.T. and Bourzat D. (eds), Small Ruminants in African Agriculture. Proceedings of a Conference held at ILCA, Addis Ababa, Ethiopia, 30 September-4 October 1985. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 82-92.

AOAC (Association of Official Analytical Chemists). 1980. Official Methods of Analysis. AOAC, Washington, DC, USA. 1018 pp.

Devendra C. 1981. Meat production from goats in developing countries. In: Smith A.J. and Gunn R.G. (eds), Intensive Animal Production in Developing Countries. BSAP (British Society of Animal Production) Occasional Publication 4. BSAP, Edinburgh, UK. pp. 395-406.

Devendra C. and Burns M. 1983. Feeding and nutrition. In: Goat Production in the Tropics. CAB (Commonwealth Agricultural Bureaux), Farnham Royal, Slough, UK. pp. 90-115.

Elliot K.C. and Topps J.H. 1963. Studies of protein requirements of ruminants 2. Protein requirement for maintenance of three breeds of cattle given diets adequate in energy and low in protein. British Journal of Nutrition 17:539-556.

Fehr P.M., Sauvant D., Delage J., Dumont BL. and Roy G. 1976. Effect of feeding methods and age at slaughter on growth performances and carcass characteristics of entire young male goats. Livestock Production Science 3:183-194.

Goering H. K. and Van Soest P.J. 1970. Forage Fibre Analysis. Agriculture Handbook, 379. Agricultural Research Service, USDA (United States Department of Agriculture), Washington, DC, USA. pp. 1-8.

Naude R.T. end Hofmeyr H.S. 1981. Meat production In: Gall C. (ed), Goat Production. Academic Press, London, UK. pp. 285-307.

Okello K.L. and Obwolo M.J. 1984. Uganda: Review of the potentialities of goat production. World Animal Review 53:27-32.

Pettit H., Honhold N. and Halliwell R.W. 1988. A condition scoring scheme for small East African goats in Zimbabwe. Small Ruminant Research Network Newsletter 13:1-7. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia.

Reed J., Ebong C., Tanner J., Gebru G. and Akale Work N. 1988. The nutritive value and use of feeds for fattening small ruminants in African highlands. A perspective of ILCA research. Small Ruminant Research Network Newsletter 12:10-27. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia.

Reynolds L. 1989. Effects of browse supplementation on the productivity of West African Dwarf goats. In: Wilson R.T. and Azeb Melaku (eds), African Small Ruminant Research and Development. Proceedings of a Conference held at Bamenda, Cameroon, 18-25 January 1989. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 237-250.

Wilson P.N. 1958. The effect of plane of nutrition on the growth and development of the East African dwarf goats. Part I. Effect of plane of nutrition on the live weight gains and external measurements of kids. Journal of Agricultural Science 50:198-210.

Zemmelink G., Tolkamp B.J. and Meinderts J.H. 1985. Feed intake and weight gain of West African Dwarf goats. In: Sumberg J.E. and Cassaday K. (eds), Sheep and Goats in Humid West Africa. Proceedings of the Workshop on Small Ruminant Production Systems in the Humid Zone of West Africa held in Ibadan, Nigeria, 23-26 January 1984. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 29-33.


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