Whole Soybeans for Market Lambs

The use of nonprocessed soybeans as a protein supplement in market lamb diets was investigated using N balance-digestion and feedlot trials. The N balance-digestion trial was a 4 × 4 Latin-square design using four Dorset × Finn wethers (mean wt 34.5 kg). Treatments were: 0% soybean meal: 100% whole soybean; 50% soybean meal: 50% whole soybean; 75% soybean meal: 25% whole soybean; and 100% soybean meal: 0% whole soybean as protein supplements added to a diet based on orchardgrass hay, ground oats and ground corn. During each of four periods, wethers were fed at 4% of body weight for 14 d of dietary adaptation followed by 7 d of total urine and feces collection during which 90% of dry matter consumed during the adaptation was fed. Apparent digestibilities of dry matter, neutral detergent fiber, acid detergent fiber and N, and ruminal fluid ammonia concentrations were not affected by treatment, but dry matter intake was less (P\u3c.05) for the 100% whole soybean treatment. Nitrogen absorption and retention were similar (P\u3e.05) for the lambs fed diets containing varying proportions of whole soybeans; however, values tended to be lower for the 100% whole soybean diet. Serum urea N was higher (P\u3c.05) for the 50% whole soybean treatment than for the 0 and 25% whole soybean treatments. A randomized complete block design was used to evaluate the effects of whole soybeans on average daily gain using 48 crossbred ram and ewe lambs (mean initial wt 22.7 kg). Twenty-four lambs were fed diets containing soybean meal or whole soybeans as the protein supplement. Lambs were fed at 4% of mean pen weight (dry matter basis). The feedlot trial results indicated that lambs receiving soybean meal as the protein supplement had higher (P\u3c.01) average daily gains (.27 kg/d) than lambs receiving whole soybeans (.23 kg/d). Results are interpreted to indicate that whole soybeans can replace soybean meal as a protein supplement but growth rates may be less