Effects of a high-protein, low-energy diet in finishing lambs: 2. Weight change, organ mass, body composition, carcass traits, fatty acid composition of lean and adipose tissue, and taste panel evaluation

An experiment was conducted to evaluate the effects of a high protein – low energy diet on body composition of feedlot lambs The objective was to assess the capability of such a diet to reduce body fat while preserving lean body mass. Three dietary regimens were compared: a typical feedlot diet (CON), barley straw at libitum (STR), and barley straw supplemented with fish meal (SFM). The latter two diets caused an energy deficit in the experimental animals. Significant treatment effects on mass of metabolic organs, body composition, and carcass data were observed. Conventional analysis of sensory data and fatty acid profiles of adipose and muscle tissue identified few significant dietary effects, yet discriminant analysis clearly separated all treatment groups. It was concluded that protein supplementation of ruminants in the catabolic state does not conserve protein mass. Given the high cost of protein supplementation, the post hoc modification of body composition of feedlot lambs is not a viable option. It is suggested that the production of feedlot lambs with a desirable degree of fatness should employ a feeding strategy dynamically adapted to the changes in protein – energy balance required by the growing ruminant.