129. A Preliminary Evaluation of the Relationship Between Winter Hair Coat Shedding Ability on Subsequent Lamb Growth Performance of Dorper Ewes.

Abstract The objective of this study was to evaluate the relationship between winter hair coat shedding ability and its association with subsequent lamb growth performance in Dorper ewes. Data were collected on spring lambing Dorper ewes with lambs from March until July in 2025 and 2026 (n = 52). Dams were observed once monthly by two trained technicians for winter hair coat shedding and were given a visual score of 1 to 5, with 1 indicating 100% shed, 2 = 75%, 3 = 50%, 4 = 25%, and 5 indicating 0% shedding of winter hair coat. Month of first shedding (MFS) was determined once a female reached an average hair shedding score of ≤ 3.5 from March until July of 2025 and 2026. For ewe performance, subsequent lamb growth and morphometric data were collected at birth and weaning, which included birth and weaning weight, head length and circumference, crown-rump length, heart girth and abdominal girth circumference, hip height, and cannon bone length. Data were analyzed using the MIXED procedure of SAS with significance declared at P ≤ 0.05. The model included MFS, day, and the respected interaction as a fixed effect with covariates of lamb sex, birth, and rearing, while sire was considered a random effect. There was MFS no difference for AdjBW (P > 0.13), but there was a main effect of MFS for AdjWW (P < 0.01) when comparing different shedding groups. Along with that finding, similar MFS main effects were determined for subsequent lamb ADG, crown rump length, and abdominal girth circumference (P < 0.01). In each of these MFS main effects, those dams that shed by July had lambs with greater AdjWW (22.89 vs. 20.14; kgs), greater ADG (0.32 vs. 0.27; kgs), longer crown rump length (61.81 vs. 58.85; cm), and larger abdominal girth circumference (54.03 vs. 51.34; cm) than all other shedding groups respectively. Preliminary interpretation of these results indicate a possible association between hair sheep winter coat shedding ability and subsequent lamb growth morphometrics. Further research into this area may be important to understanding the impact this has on ewe performance due to adaptability in the southern U.S.