Effect of dietary energy level on growth and carcass characteristics of female goats in Sudan

Y M Yagoub and S A Babiker*

Faculty of Agricultural Technology and Fish Sciences, Al-Neelain University Khartoum, Sudan
Yagoub_12232501@hotmail.com
*Department of Meat Production, Faculty of Animal Production, University of Khartoum, Shambat, Sudan

Abstract

Sixty Nubian female goat kids were divided into four groups of equal number to study the effect of dietary energy level on female goat meat production characteristics. The study was conducted at Kassala University farm, Sudan. Four iso-nitrogenous diets containing graded levels of metabolizable energy (11.5, 10.5, 9.5 and 8.5 MJ/kg DM) were randomly assigned to the goat groups. Feeding was on ad-libitum base for 105 days.

Decrease of dietary energy level induced a significant (p<0.001) reduction in growth rate, feed conversion efficiency and slaughter weight. In attempt to meet their energy requirements female goat kids were found to increase their dry matter intake as dietary energy level dropped from 11.5 to 9.5 MJ. At 8.5 MJ dietary energy concentration dry matter intake was reduced and gut fill increased significantly. Carcass weight and dressing percentage were also reduced significantly (p<0.01) with the decrease of dietary energy level and here again the diet with 8.5 MJ/kg DM energy concentration induced maximum reduction in both traits. Carcass bone was increased and fat was decreased, but muscles were not affected as dietary energy deteriorated.   Body components as head, skin, four feet and liver were significantly (p<0.01) increased and that of fat depots were significantly (p<0.01) with the decrease of dietary energy level.

Keywords: metabolizable energy, Nubian, protein

Introduction

According to FAO (2002) statistics world goat population represents 64% that of sheep, yet their meat accounts to 49% of mutton and lamb. This low productivity may be due to the fact that 96% of the world goats are in the developing countries where goat improvements programmes are scarce. Compared with sheep the growth rate and feed conversion efficiency of goats are low ( El Khidir et al 1998) and within the same species females are even more inferior in growth rate and efficiency of gain and produce fatter carcasses on intensive feeding than males ( El Moula et al 1999).

These production disadvantages limit investment in goats for meat production. On the other hand, goats dress higher than sheep and produce meat with superior processing properties and low in fat that make it a healthy commodity (Babiker et al 1990). To utilize goats, particularly females, for meat production low energy cheap diets that do not favors fat deposition are recommended.

The objective of this research is to study the effect of the dietary energy level on growth and carcass characteristics of female goats.

Methodology 

Sixty Nubian female goat kids with an average live weight of 16.5+ 0.31kg and age range 9-12 month were used in this study. Goats were kept for an adaptation period of two weeks during which they were sprayed with an acricide and drenched for endoparasites. A mixture containing equal proportions of experimental diets was fed to the goats. At the end of the adaptation period goat kids were individually weighed and divided into four groups of equal number and weight. Each group was separately kept in a pen provided with watering and feeding facilities. Four iso-nitrogenous diets, contains graded levels of energy (11.5, 10.5, 9.5 and 8.5Mj/KgDM) were formulated, Table (1).

The diets were randomly assigned to the goat groups and offered Adlibitum in one morning meal throughout the feeding period. Green fodder (Medicago Sativa) was also offered at a rate of 1kg/ head/week as a source of vitamin A. Clean water and salt lick were available throughout the feeding period which lasted for 105 days. Feed intake, live weight and carcass data were determined as described by (El Moula et al 1999).

Data were statistically analyzed according to the analysis of variance applicable to complete randomized design as described by (Snedecor and Cochran 1980) and Duncan multiple range tests were used to detect difference between means (Gomez and Gomez 1984).

Results 

Performance characteristics of female goat kids Table (2) revealed that as the level of the dietary energy decreased final live weight significantly (P<0.001) decreased.

Similarly empty body weight significantly (P<0.01) decreased with the decrease of dietary energy level. Here changes in the level of natural nitrogen sources could also be implicated. Both daily and weekly rates of gain as well as total live weight gain were also significantly (P<0.001) decreased, here the diet with 8.5 MJ energy concentration induced maximum reduction in growth characteristics. Total dry matter intake increased with the decrease of dietary energy up to 9.5 MJ/kg and then decreased with the decrease of energy level to 8.5MJ/kg.Gut fill significantly (p<0.05) increased with the decrease of dietary energy level while feed conversion efficiency deteriorated significantly (P<0.01) particularly in goat kids fed the diet contained 8.5 MJ/kg energy.

Reduction of dietary energy level and changes in sources of dietary protein were associated with a significant (P<0.01) reduction in slaughter weight particularly at 9.5 and 8.5 MJ/kg Table (3).Hot and cold carcass weights showed the same pattern of changes as slaughter weight.

Chiller shrinkage increased but not significantly with the decrease of dietary energy level. The dressing percentage decreased significantly (P<0.01) with the decrease of dietary energy level and it was least in the goat kids group fed the diet that contained 8.5MJ/kg metabolizable energy level. Carcass dissection Table (3) indicated that dietary energy level had no significant effect in carcass muscle percentage but carcass bone percentage was significantly (P<0.01) increased and that of fat significantly (P<0.01) decreased with the decrease of the dietary energy level.

Body components of female goat kids given in Table (4) revealed significant ( P<0.01) increase in the weight of head, skin, four feet and liver with the decrease of the dietary energy level, while diaphragm and trachea, empty intestine and rumen increased in weight and the increase was significant ( P<0.05) at 8.5 MJ/kg energy level.

Omental, mesenteric and kidney knob and channel fat decreased with the decrease of the dietary energy level and the decrease was significant (P<0.01) for the omental and the kidney knob and channel fat at the energy levels of 9.5 and 8.5 MJ/kg respectively.

Discussion 

Performance study indicated that in female goat kids the rate of live weight gain decreased with the decrease of the dietary energy level and changes of source of protein, these changes in live weight might be due to the latter change, and that induced a significant reduction in the final live weight attained. The diet that contained 8.5 MJ/kg energy just maintained female goats live weight. Sanjava et al (1990), Shahjelal et al (1992) and Ibrahim (1996) reported increased rate of gain in male goat kids with increase of dietary energy level. In an attempt to meet their energy requirements female goat kids were found to increase their dry matter intake as the dietary energy level dropped from 11.5 to 9.5 MJ/kg. At a low dietary energy 8.5MJ/kg dry matter intake was reduced significantly possibly due to slow passage of ingesta as indicated by the significant (P< 0.05) increase in gut fill, Table (2).

Feed conversion efficiency deteriorated with the decrease of the dietary energy level and changes in protein source, here the decrease in growth rate and live weight attained could be the reason. Sanjava et al (1990), Shahjelal et al (1992) and Ibrahim (1996) also reported deterioration in feed conversion efficiency in goats which were associated with reduction in growth rate when dietary energy was reduced.

Carcass weight decreased with the decrease of dietary energy level and that reflected the decrease in slaughter weight. The dressing percentage was significantly lower in the female goat group fed the diet that contained 8.5Mj/kg metabolizable energy. The reduction in the dressing percentage resulted from the reduction in the carcass weight (Table3) and body fat and increase in gut fill.

Dressing percentage increase with the increase of fatness (Preston and Willis 1975) and this is associated with feeding of high dietary energy. Fattening was reported to increase the dressing percentage in goats from 45 to 54% (Gaili et al 1972). Ibrahim (1996) reported a significant reduction in dressing percentage of male goats when dietary energy decreased from 12.0 to 8.0 MJ/kg in addition to the increase in the proportion of body components as head, skin, feet, liver, heart, rumen and intestines. The diet with the least energy level (8.5MJ/kg) resulted in a significant increase in carcass bone and a decrease in carcass fat. The decrease in carcass fat could be attributed to the decrease in feed intake in the animals fed this diet. Ash and Norton (1987) reported increased carcass fat in Australian feral goats fed adlibitum compared with those on restricted diet.

Shahjelal et al (1992) and Ibrahim (1996) reported an increase in carcass fat and a decrease in bone in goats as the dietary energy level declined. The observed increase in carcass shrinkage in animals fed the diet with 8.5 MJ/kg could be attributed mainly to the reduction in carcass fatness. Body components other than fat depots, increased with the decrease of dietary energy level. Fat is a latter maturing tissue and has less priority for nutrients (Hammond 1932).It could be concluded that finishing of female goat kids can be performed on diets containing 9.5 MJ/kg Dm. Low dietary energy of 8.5 MJ/kg was found to reduce live weight growth, slaughter weight, carcass weight and dressing percentage. It also increased gut fill and the weight of body components as head, skin, four feet, heart, liver, rumen and intestine. The latter dietary energy just maintained the live weight of female goat kids.

Conclusions     

• It could be concluded that the dietary energy level (11.5 MJ/kg) produced the best feedlot performance, carcass characteristics and body component of femalegoat kid.

  
  

• The difference in performance and carcass characteristics between dietaryenergy 11.5 MJ/kg and 10.5 MJ/kg was generally not significant and thus female goat kids could be finished satisfactory on a dietary level of 10.5 MJ/kg.

  
  

• The lowest dietary energy level (8.5 MJ/kg) just maintained their body condition.

References 

Ash A J and Norton B W 1987 Studies with Australian Cashmere goat. I. Growth and digestion in male and female goats given pelleted diets varying in protein content and energy level. Australian Journal of Agriculture 38: 957 – 969

Babiker S A, El Khidir I A and Shafie S A 1990 Chemical composition and quality attributes of goat meat and lamb. Meat Science 28 (4): 273 – 277

El Khidir I A, Babiker SA and Shafie S A 1998 Comparative feedlot performance and carcass characteristics of Sudanese desert sheep and goat. Small Ruminant Research 30: 147-151

El Moula I H A, Babiker S A, El Khidir OA and Ibrahim S E 1999 Meat production from female goat kids compared with males. Journal of Agricultural Science (Cambridge) 133: 223 – 226

FAO 2002 Quarterly Bulletin of Statistics, Food and Agricultural Organization Rome, Italy.

Gaili E S E, Ghanem Y S and Mukhtar A M S 1972 A comparative study of some carcass characteristics of Sudan desert sheep and goats. Animal production 14: 351 – 357

Gomez R A and Gomez A A 1984 Statistical procedure in Agricultural research. John and Willy and son. New York.

Hammond J 1932 Growth and development of Mutton Qualities in Sheep. Edinburgh.

Ibrahim S E 1996 The effect of dietary energy level on fishing goats. M.Sc. Thesis. University of Khartoum.

MAFF 1976 Ministry of Agriculture, Fisheries and Food, London, U.K Energy Allowances and feeding Systems for Ruminants. Her Majesty^’s Stationary Office London, U.K.

Preston T R and Willis M B 1975 Intensive beef production.p.306-310, 417-418.Pergamon press, Oxford.

Sanjava K, Tiwari S P and Narany M P 1990 Effect of plane of nutrient utilization and growth of Goddi Kids. Indian Journal of Animal Nutrition 7(1):7 – 10

Shahjalal M D, Gallriath H and Topp J H 1992 The effect of changes in dietary protein and energy on growth, body composition and Mohair fiber characteristics of British angora goats. Journal of Animal Production 54: 405 – 412

Snedecor G W and Cochran W G 1980 Statistical Methods, Iowa State University Press. Ames, Iowa, U.S.A.

Received 15 July 2008; Accepted 9 October 2008; Published 5 December 2008

Go to top