Summary
Ruminants adapt to periodic fluctuation in feed resources by accumulating fat stores during favourable periods. Thus, genetic variations, among ruminant genotypes, in the capacity to deposit fat could be exploited through breeding to improve animal productivity in traditional tropical production systems. Based on this premise, breed differences among weights of principal adipose depots and total body fat were estimated in Menz (n = 303) and Horro (n = 151) sheep of Ethiopia. Animals were kept on supplemental feeding, for about 3.5 months, until slaughter at about 17 months of age and pre‐slaughter live weight of 25 kg. Except the combined weight of tail and rump fat (TRF) which was similar (p > 0.05) in the two breeds, weights of subcutaneous and intermuscular fat (SIF), internal fat (IF) as well as total dissected body fat (TotDF), total ether‐extracted body fat (TotEE) and TotFAT (TotDF plus ‘residual’ fat, fat recovered by ether‐extraction from non‐adipose tissues) were significantly (p < 0.01) higher in the Menz. TotDF, TotEE and TotFAT were 1.91 ± 0.04, 2.05 ± 0.06 and 2.64 ± 0.06 kg, respectively, in the Menz and 1.50 ± 0.05, 1.44 ± 0.06 and 2.02 ± 0.07 kg, respectively, in the Horro. Implications of breed differences in fat distribution among depots, and possible consequences of genetic improvement of some of the depots on adaptation to climatic and nutritional stresses as well as some production objectives are discussed.
On-station characterisation of indigenous Menz (n = 1 639) and Horro (n = 1 135) sheep of Ethiopia in the central highlands of the country was undertaken between 1992 and 1997 at the Debre Berhan Research Station of the International Livestock Research Institute (ILRI) to study the phenotypic characteristics of the breeds. Body weights, linear body measurements, and testicular parameters were studied. The traits studied were live body weights (LWT), body length (BL), heart girth (HG), height at withers (WH), pelvic width (PW), chest depth (CD), distance between last rib and tuber coxae (DLP-ATR), scrotal circumference (SC), testicular diameter (TD), testicular length (TL), and epididymal tail diameter (ED). All except LWT (which was also measured at birth) were measured at 3, 12 and 24 months age. Fixed effects included in the analyses were breed, sex, birth type, birth season, birth year, and significant first-order interactions.The Horro sheep had significantly (P<0.05) larger LWT at all ages than the Menz by as much as 6 to 18%. In both breeds, lambs born single were significantly (P<0.05) heavier than those born as twins or triplets. In all age categories and both breeds, males were consistently heavier and larger in size than females. Except for lambs of una medida testicular mayor (P<0,05) respecto a la raza Menz.
Compared with conventional indoor rations, consumption of grazed grass by cattle improved the fatty acid profile of beef, by increasing the polyunsaturated fatty acid (PUFA) and conjugated linoleic acid (CLA) concentrations and decreasing the n-6:n-3 PUFA ratio (French et al., 2000). Supplementation of grazing cattle with sunflower oil (S), increased the concentration of CLA in muscle but also increased the n-6: n-3 PUFA ratio (Noci et al., 2006). Supplementation with fishoil (F), a source of long-chain n-3 PUFA might decrease this ratio while enhancing CLA synthesis. However, increasing the concentration of PUFA, particularly the long-chain PUFA, may predispose muscle lipids and pigments to oxidation, with consequent impairment of lipid and colour stability. The objectives were to determine the effect of supplementation of grazing cattle with S and F on (i) tissue n-3 PUFA and CLA concentrations and (ii) the colour and lipid stability of beef.
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