Effect of Type of Supplemental Nutrient on Grass Silage Utilization by Sheep

Abstract

ABSTRACT In order to determine whether energy, ruminally degradable intake protein, ruminally undegradable intake protein, or quality of undegradable intake protein limit utilization of nutrients in young ruminants consuming grass silage (12% crude protein, CP; 56% neutral detergent fiber), two nitrogen balance experiments were conducted as replicated 4 × 4 Latin squares with 16 ewe lambs (average body weight 37 ± 2 kg). In Experiment 1, lambs were supplemented with either: control, minerals only (C); 264 g of dry matter (DM) as barley (B); 70 g of DM as soybean meal (S); or 70 g of DM as heated soybean meal (H). In Experiment 2, lambs were supplemented with either C; H; 67 g of DM as H with 15% Menhaden fish meal (H15); or 64 g of DM as H with 30% Menhaden fish meal (H30). All supplements (except C) were offered in isonitrogenous amounts. In Experiment 1, daily intakes of total DM and digestible DM were greatest for B (1,859 and 1,289 g) and lowest for C (1,612 and 1,091 g). In both experiments, percentage of CP digested and retained were lowest for C (55 and 24%, respectively). Retention of CP was greatest for B (30%) in Experiment 1 and greatest for H30 in Experiment 2 (32%). In Experiment 2, retention of CP increased linearly, whereas urinary loss of CP decreased linearly with addition of fish meal to H (among H, H15, H30). Results of Experiment I indicate supplementation of B can most efficiently improve energy intake plus be effective at improving utilization of CP. Results from Experiment 2 suggest that as the quality of undegraded intake protein increases, the efficiency of its use increases.