Abstract The post-weaning period, as lambs transition to an all solid diet, is critical for their subsequent growth and well-being. Two experiments were conducted that evaluated the use of soy hull (SH) and corn gluten feed (CG) for diets of weaned lambs transitioning in a dry lot prior to return to pasture for grow-out. Lambs were born on pasture, weaned at approximately 9 weeks of age, and placed in semi-covered pens with outdoor access. In experiment I, at weaning, 32 mixed-sex (ewe lambs and wethers), December-born St. Croix and Barbados Blackbelly lambs were placed in 8 pens balanced by breed, sex and weaning weight. Lambs were fed a weaning ration of corn/soybean meal with coccidiostat (1.5% BW), SH and CG (pre-weaning diet, 1% BW), and alfalfa pellets (0.5% BW) during a 2-week transition period where corn/soybean meal and alfalfa pellets were removed from the diet. Lambs had ad lib access to medium-quality hay. For the trial proper, lambs either received a SH/CG mix (50/50) at either 2.5% or 3.5% BW (4 pens per ration) during a 56-d feeding trial. Lambs were weighed at 2-wk intervals to adjust feed supplements, and hay intake was recorded for 6 d at the beginning and end of the trial. Experiment II followed the same protocol, but used 48 April-born lambs and compared SH and SH/CG (50/50) supplements both fed at 3.5% BW. Growth data was analyzed with animal as the experimental unit in a model with supplement level/type, breed, sex, and birth type as the main effects, whereas intake was analyzed with pen as the experimental unit and supplement level and time as the main effects. In Experiment I lambs fed at 3.5% had a higher ADG than at 2.5% SH/CG (125 vs. 92 g/d; 0.001). Hay intake (%BW) was higher at 2.5% compared to 3.5% supplementation (1.91% vs. 1.29% BW; P 0.001), but total intake was lower (4.41% vs. 4.79; P 0.05). Total intake declined (P 0.05) at 3.5% supplementation but not 2.5% from the beginning to the end of the trial. In Experiment II ADG during the first 4 wk of the trial was higher in SH compared to SH/CG lambs (93 vs. 63 g/d; P 0.05), but similar during the second half of the trial (113 vs. 112 g/d). Supplement type affected intake and increased hay intake in SH/CG lambs but not SH lambs by the end of trial (1.19 vs. 1.60% BW; P 0.05). In this study, higher levels of agro-byproduct supplementation increased growth rate even with increased hay intake at lower rates of supplementation. Integrating CG feed into lamb rations may require an extended period of adaptation, but can enhance hay consumption.
Wildeus et al. (Wed,) studied this question.