New Zealand Journal of Agricultural Research abstracts

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Effects of age at slaughter and sire genotype on fatness, muscularity, and the quality of meat from ram lambs born to Romney ewes

R. W. Purchas

Institute of Food, Nutrition and Human Health
Massey University
Private Bag 11 222
Palmerston North, New Zealand

A. G. Silva Sobrinho

Departmento de Zootecnia
Universidade Estadual Paulista
Jaboticabal, SP, Brazil

D. J. Garrick

Institute of Veterinary, Animal and Biomedical
Science
Massey University
Private Bag 11 222
Palmerston North, New Zealand

K. I. Lowe

Ag/Hort Systems Management
Massey University
Private Bag 11 222
Palmerston North, New Zealand

Abstract  Ram lambs (n = 356) born to Romney ewes and sired by a range of straightbred or cross-bred sires were evaluated for carcass composition and, for a subsample (n = 236), some meat quality characteristics over a period of 4 years. Within each year, 2 to 4 sire genotypes, including Romney controls, were evaluated at 2 slaughter ages (5–9 months and 10–11 months). Weight-adjusted carcass length was greater for lambs with some East Friesian or Finn genes, but no differences were found in dressing-out percent. At a constant carcass weight, carcass fatness (fat depths and leg dissectible fat) was lower in lambs with East Friesian, Texel, or Finn genes. Meat yield at a constant weight tended to be greatest in sire groups that were least fat, and M:B ratio in the femur region was highest in lambs with Texel genes and, to a lesser extent, those with Poll Dorset genes. Leg muscularity in the femur region generally paralleled differences in M:B, except in a comparison of East Friesian-cross and Romney lambs where the former had lower muscularity but slightly better M:B. Lambs slaughtered at the older age for each year had longer and leaner carcasses at the same weight, possibly because they had been taken part way through a winter or because of slower growth rates leading up to slaughter. Meat quality characteristics differed little between the genotype groups, but for 2 of 3 years, meat from the semimembranosus muscle of lambs in the older slaughter lot was significantly tougher.

Keywords  lamb fatness; carcass muscularity; meat tenderness; sheep breeds

Received 10 September 2001; accepted 25 January 2002
New Zealand Journal of Agricultural Research, 2002, Vol. 45: 77–86
0028–8233/02/4502–0077 $7.00/0 © The Royal Society of New Zealand 2002

PDF file of entire paper: Print-quality (122K)

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