44 Evaluation of the Relationship Between Hair Coat Shedding Ability and Apparent Digestibility in Angus Cattle

Abstract

Abstract The objective of this study was to evaluate winter hair coat shedding ability in conjunction with apparent forage digestibility. Data were collected on fall calving purebred Angus females with calves from March until July in 2019 (n = 10) and 2020 (n = 31). 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 complete shed and 5 indicating no shed. Month of first shed (MFS) was determined when a female reached an average hair shedding score of 3.5 for any given month. Fecal samples were collected during the grazing months of March, May, and July for 5 consecutive days and were then analyzed via proximate analysis to calculate apparent digestibility of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), ash, and dry matter percentage (DM) of forage. Data were analyzed using repeated measures of the MIXED procedure of SAS with a significance declared at P ≤ 0.05. The model included MFS, month, and MFS by month interaction with year and ambient temperature as a covariate with cow ID nested within MFS Interactions of MFS by month were observed for CP, ADF, NDF, ash, and DM. Females with a MFS in May or June showed decreased CP apparent digestibility during the month of May when compared with cows reaching a MFS in April or July (P = 0.04). For DM in July, females with an MFS in June and July were similar but decreased when compared to females with an MFS in April and May (P = 0.015). Interpretation of these results show no clear trend of an association between hair shedding ability and apparent digestibility. Further research into this area is important in understanding changes in overall cow performance due to adaptability.