In fat-tailed sheep, variation of energy intake affected growth performances, carcass muscle and tail fat, without modifying carcass fat: A meta-analysis

Abstract

The study aimed to evaluate, using meta-analysis, average daily gain (ADG), carcass tissue composition (carcass muscle and carcass adipose tissue (CAT)), internal fat (kidney and mesenteric fats) and tail fat responses to metabolizable energy intake (MEI) for fat-tailed lambs. Data from 31 international publications representing 78 treatments were analyzed. Breeds were characterized according to their precocity (Early and Moderate-Early) and maturity stage (Young, Intermediate and Adult). The results showed that each MEI increase by 1 MJ/d/kg LW was accompanied by 12.02 g/d/kg LW ADG and 0.14 kg/kg LW carcass muscle. For fats, only tail fat varied with MEI. For an increase of 1.00 MJ/d/kg LW MEI, fat tail increased by 0.16 kg/kg LW and the response of tail fat to MEI was higher for Early than for Moderate-Early lambs and for adult lambs than for young ones. The variation of carcass tissue composition to ADG changes was also established. Carcass muscle increase by 0.01 kg/kg LW and CAT increase by 0.014 kg/kg LW for each 1.00 g/d/kg LW increment of ADG. According to ADG change, carcass muscle was higher for young lambs whereas CAT was higher for adult lambs. For fats, only tail fat increase with CAT and each 1.00 kg/kg LW increase of CAT was accompanied by 0.33 kg/kg LW tail fat. The slope was higher (P = 0.002 ) for adult lambs (0.83 kg/kg LW) than for young lambs (0.28 kg/kg LW). Tail fat seemed to be an indicator of precocity in sheep and its higher response to energy increment confirm his role as an energy reserve for fat tailed sheep reared in harsh conditions. It is also very interesting to note that for sheep up 62 % of adult weight, the MEI increment increased ADG, carcass muscle, tail fat, without affecting carcass fat.