Effects of dietary concentrate levels on growth performance, feed intake and carcass characteristics of fattening Chall male lambs

Fattening lambs is an important source of animal protein in Iran. The fattening enterprise is performed by rearing livestock on pasture or at feedlot or both of them. At this time, feedlot system with feeding high concentrate diets is more prevalent than other systems. This study was conducted to evaluate the effects of using different dietary forage to concentrate ratios on growth performance, feed intake, feed efficiency, and carcass characteristics of fattening Chall male lambs in Animal Science Research Institute.
Eighty Chall male lambs breed, averaging four to five months of age and body weight of 33.5±3.9 kg were randomly assigned to four treatments with four replicates of five animals per treatment. Four diets containing alfalfa hay-to-concentrate ratios (DM basis) of 70:30, 50:50, 30:70, 10:90; Metabolizable energy of 2.23, 2.43, 2.58; 2.71 Mcal/kg DM and CP contents of 151, 158, 164, and 170 g/kg were randomly assigned to four groups, respectively. The diets were prepared in pelleted form and lambs were fed three times a day at 8.00, 14.00 and 20.00 for 84 days ad libitum. At the end of the feeding period, all lambs were weighed after 16 h feed deprivation and one lamb from each replicate was slaughtered. After complete bleeding, the bodies were skinned and the internal organs such as head, feet and skin were weighed. The carcasses were eviscerated, and the internal organs or tissues and digestive tract were separated and weighed. The hot carcasses were weighed and chilled at 4ºC for 24 h. The cold carcasses were weighed and sawed into two symmetrical sides along backbone. The right side carcasses were cut into six wholesale cuts (neck, shoulder, leg, rack–loin, brisket– flank, and tail fat) and weighed separately. All cuts except tail fat were dissected into the main tissue components (lean, subcutaneous and inter-muscular fat, and bone) and the weight of each tissue was recorded.
Dry matter intake and feed conversion ratio (P In conclusion the results of this study indicated that the increase of dietary concentrate (up to 700 g/kg) improves growth rate, FCR and dressing percentage without negative effect on carcass lean-to-fat ratio of Chall lambs.