Carcass, composition

NaturaHy occurring and synthetic estrogens and androgens have been extensively and safely used to improve efficiency and carcass composition ia growing beef catde in the United States since the early 1950s. Several anaboHc steroid implants have been approved for use in beef catde in the United States, but only one, zeranol [55331-29-8] is approved for use in lambs. Anabolic steroids are not used for growth regulation in swine or poultry (see Steroids). 

Lambs received saline, oST at 40 )-lg/kg BW, or the indicated dose of hGRF per kg BW four times per day for 42 or 56 days. Half of the lambs were withdrawn from treatment after 42 days. Carcass data shown are for lambs treated 56 days. Carcass composition data were analy2ed by analysis of variance using carcass weight as the covariate. Data are summarized in Ref. 85. 

The more variable responses with growing catde appear to result from lower doses, nutritional constraints, or lesser responsiveness of younger animals, ie, veal calves. A dose-dependent reduction in feed intake in finishing cattle, which also reduced average daily gain, has been observed (84). However, carcass composition was improved in a dose-dependent manner. 

Table 4. Effects of p-Agonists on Growth and Carcass Composition of Growing Lambs...

Data for carcass composition corresponding to protein and lipid are percent-dissected skeletal muscle and adipose, respectively. 

Enfalt A-C, Lundstrom K, Hansson I, Johansen S and Nystrom P E (1997), Comparison of non-carriers and heterozygous carriers of the RN allele for carcass composition, muscle distribution and technological meat quality in Hampshire-sired pigs , Livest Prod Sci, 47, 221-22. 

Martel J, Minvielle F and Poste L M (1988), Effects of crossbreeding and sex on carcass composition, cooking properties and sensory characteristics of pork , J Anim Sci, 66, 41 16. 

Sather A P, Jones S D, Schaefer A L, Colyn J and Robertson W M (1997), Feedlot performance, carcass composition and meat quahty of free-range reared pigs , Can J Anim Sci, 77, 225-232. 

The decreased level of androgens in castrated male cattle as a result of testicular removal leads to production of a carcass that is intermediate between that of an intact male and a female. Since the increased proportion of fat in such a carcass makes it less valuable for the health-conscious consumer, extensive research has been directed towards replacing the loss of carcass quality resulting from castration, by administration to the animals of various natural and synthetic hormonal substances, collectively called anabolic hormonal-type growth promoters. These compounds can substantially increase growth rate and improve feed efficiency and carcass composition in a process that may be highly profitable for the animal feeders. 

Treatment and dose, ppm Treatment period, d ADG,a g/d Feed gainb Carcass composition, % Protein Lipid Reference... 

Jones, H.E., Lewis, R.M., Young, M.J., and Simm, G. 2004. Genetic parameters for carcass composition and muscularity in sheep measured by X-ray computer tomography, ultrasound and dissection. Livestock Prod. Sci. 90, 167-179. 

Lewis, P.D., Perry, G.C., Farmer, L.J. and Patterson, R.L.S. (1997) Responses of two genotypes of chicken to the diets and stocking densities typical of UK and Label Rouge production systems I. Performance, behaviour and carcass composition. Meat Science 45, 501-516. 

Lyman, R. L., and Wilcox, S. S., Effect of acute amino acid deficiencies on carcass composition and pancreatic function in the force-fed rat. I. Efficiencies of valine, lysine, tryptophan, leucine, and isoleucine, /. Nutr., 79, 37, 1963. 

Feedlot performance, carcass composition, and muscle and fat, CLA concentrations of lambs fed diets supplemented with safflower seeds. Small Ruminant Research, 49, 11-17. 

Wachira, A. M., Sinclair, L. A., Wilkinson, R. G., Enser, M., Wood, J. D., Fisher, A. V. (2002). Effects of dietary fat sonrce and breed on the carcass composition, n-3 polyunsaturated fatty acid and conjugated hnoleic acid content of sheep meat and adipose tissue. British Journal of Nutrition, 88, 697-709. 

Thiel-Cooper, R.L., Parrish, F.C., Sparks, J.C., Wiegand, B.R., and Ewan, R.C. (2001) Conjugated Linoleic Acid Changes Swine Performance and Carcass Composition, J. Anim. Sci. 79, 1821-1828. 

In some circumstances it is possible to express protein requirements in terms of total protein alone, for example if animals are fed on a limited range of foods of known amino acid composition. This is the case for growing pigs in the USA that are fed mainly on maize and soya bean meal. Such a simplified approach cannot be sustained when a wider range of foods and by-products are used, and when diets must be formulated not only to maximise growth but also to optimise carcass composition. Feed compoimders therefore formulate pig diets to meet the requirements for at least three amino acids (lysine, methionine -I- cystine and threonine).They will also take into accoimt the availability of certain amino acids, assessed from digestibility at the terminal Ueiun (as explained in Chapter 10). 

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