THE EFFECT OF SUPPLEMENTATION WITH PROTEIN, LIPID AND PROPIONATE ON NUTRIENT PARTITIONING IN ROUGHAGE-FED LAMBS

Eighty castrated male lambs were allocated to either an initial slaugh ter group (no. = 16) or one of eight treatment groups (no. = 8). Ammon iated barley straw was offered ad libitum. This was supplemented with sodium (Na) propionate (0 or 20 g/day), formaldehyde-treated casein, ( protected casein, 0 or 50 g/day) and/or calcium (Ca) salts of long-cha in fatty acids (Ca soap, 0 or 30 g/day), as a factorial design. Measur ements were made of food intake, live-weight gain and wool growth, rum en fluid parameters and changes in body composition over a period of 1 55 days. Food intake (g dry matter per kg live weight) was lower in th e groups supplemented with Ca soap and Na propionate. Fleece-free live -weight gain was increased by supplementation with protected casein an d Ca soap, but was not affected by Na propionate. Supplementation with protected casein increased wool yield. Adjusted means for water, prot ein and ash content of the body (adjusted to mean fleece/digesta-free body weight at slaughter of 27.1 kg) were affected significantly by th e second-order interaction between the supplements. Adjusted body wate r and protein mass were lower when Na propionate was given alone or wi th Ca soap and protected casein. Fat mass tended to be higher under th ose conditions. Supplementation with Ca soap increased adjusted fat an d gross energy contents and decreased adjusted protein and water mass. Supplementation with protected casein decreased total body fat and in creased adjusted protein mass in the body. The partitioning of water, protein, fat, ash and energy between the carcass and non-carcass resid ues was affected to a small extent also. These results demonstrate int eractive effects of the supplements used, on nutrient partitioning in lambs offered straw-based diets.