Growth and carcass characteristics of crossbred progeny from lean-tailed and fat-tailed sheep breeds

Abstract

The performance of two fat-tailed sheep breeds, Chaal and Zandi, and their F1 and R1 crossbred lambs
from a lean-tailed breed, Zel, was compared. The weaned lambs from the Chaal and Zandi groups were
finished over periods of 105 and 90 days, respectively, and body weight gain and feed consumption were
recorded. Forty six male and female lambs from the six finishing groups were slaughtered. The weights of
blood, internal organs, intestines before and after removal of digesta, head, feet, pelt and carcasses were
recorded. The left sides of the carcasses were cut into six pieces. Individual joints were dissected into lean
meat, bone, subcutaneous fat (SCF), intramuscular fat (IMF) and trimmings, and weighed separately. The fat
surrounding the intestine and kidney was weighed and considered as internal fat. All the soft tissue (lean
meat and fat) of the left sides of the carcasses was ground and representative samples were taken for
chemical analyses. The differences of eye muscle ( Longissimis dorsi ) area (cm²), and protein and bone
percentages were not significant between both breeds and their crosses. In the R1 the fat-tail percentage was
less than in the F1 and pure lambs of both breeds. In contrast, the SCF and IMF percentages were higher in
all crossbred combinations. The internal fat percentages in crossbreds were higher, and in the Chaal group
differed significantly from that of the pure lambs. The SCF/IMF ratio in the R1 lambs was lower than in the
pure breds. This difference for Chaal crossbreds was significant. The lower ratio of SCF/IMF and the higher
internal fat of crossbred lambs compared to pure breds showed that carcass quality of the crossbred was
inferior compared to the pure bred lambs in terms of fat distribution in the body.

Keywords: Sheep, fat-tail, backcross, Chaal, Zandi, Zel

South African Journal of Animal Science Vol. 37 (1) 2007: pp. 51-56