91 Growth performance of landrace hair sheep lambs under different forage environments

Abstract

Abstract Lambs for the project were produced under semi-continuous lambing using accelerated mating in a dual flock system of landrace hair sheep (Barbados Blackbelly and St. Croix). Lamb cohorts were born every 4 mo. At 4 mo of age, lambs were rotationally stocked on pastures consisting of either tall fescue, summer and winter annual forage mixtures, or were provided bermudagrass hay in sacrifice pastures. Lambs were rotated based on forage availability, and forage was sampled for nutrient analysis at each rotation. Soyhull pellets were provided at 1–3% BW. Lambs were removed as they reached 36 kg. Weights were recorded (n = 1945) from 7 cohorts between December 2017 and September 2019 as lambs moved between forage environments (6 to 40 d). The grazing lamb flock was made up of two cohorts (initial size: 25–53 lambs) at any given time. The effect of breed, sex, cohort class (4–7 mo, and 8–11 mo), and forage environment (classified as cool and warm season annual, perennial pasture, and hay) on ADG was determined. Mean ADG was higher in St. Croix than Barbados Blackbelly (105 vs. 93 g/d; P< 0.05), and ram than ewe lambs (115 vs. 84 g/d; P < 0.001). Older cohorts in each grazing period had higher ADG than younger cohorts (105 vs. 94 g/d; P < 0.05). There was a wide range in ADG for individual weigh periods (16 to 310 g/d), but warm and cool season annuals and hay feeding forage environments produced similar ADG (110–117 g/d); while summer perennial forage grazing was lower (56 g/d; P < 0.001). Supplementing forage with soyhull may have masked differences in lamb growth between forage environments despite higher crude protein and TDN in the annual forages (11 to 20%; and 55 to 85%) than in hay and perennial summer grazing (8 to 10%; and 50 to 55%).