Between and within-Breed Variations in feed intake and fat deposition, and Genetic Associations of these with some production traits in Menz and Horro Sheep

A total of four hundred and fifty seven Menz (n=305) and Horro (n=152) male lambs born over eight consecutive dry- and wet-seasons from October 1992 to July 1996, at ILRI's Debre Berhan Research station were used to: i) determine between-breed differences and within-breed variations in feed intake and fat deposition, and the genetic associations of these with average daily weight gain (ADG), efficiency of feed utilisation (EFU), carcass weight, lean yield and dressing percent and, ii) establish and evaluate equations for predicting total body fat from live animal body measurements. The lambs were fed ad-libitum for about three-and-half months, during which concentrate supplement and hay intake, ADG, EFU and the various live animal measurements were recorded. Lambs were slaughtered at average age of 510 days, where the weights of hot and cold carcass, dissected lean, reticulo-rumen (RRW), individual principal fat depots and total body fat were determined. Dissected fat depots and non-adipose tissues were subjected to ether-extraction to obtain the weights of ether-extracted individual principal adipose tissues and total ether-extracted body fats. Average daily intake of the concentrate supplement did not significantly (P>0.05) differ between the two breeds. However, the Horro exhibited significantly (P0.05) in the two breeds. Live weight during ad-libitum feeding was not different (P>0.05) between the two breeds, but the Horro was significantly (P0.05) differ between the two breeds. Dissected carcass lean weight was also similar (P>0.05) in the two breeds; but carcass dissected fat weight was significantly (P0.05) biased by breed, birth type, dam parity and lamb season of birth, heritabilities of, and genetic correlation involving predicted total body fat were non-significant due to large standard errors caused by the small data set