Differences in hair coat shedding, and effects on calf weaning weight and BCS among Angus dams

Abstract

The objective of the study was to assess variation in hair coat shedding of Angus cows, and its effect on adjusted weaning weight (d205wt) and BCS. Data were available from 532 Angus cows over 3years of age. Beginning in March and for 5months at 30-d intervals, trained technicians scored cows on a scale from 1 to 5, with 1 representing slick coats and 5 winter coats. For each cow, the first month with a score of 3 or less (MFS, 5 levels) was considered the beginning of winter coat shedding and used in the analyses. Association between MFS and d205WT or BCS, was investigated using the mixed procedure of SAS. Data were further analyzed by dividing cows into two groups, group one (Group 1) were cows with a shedding score of 3 or less by June 1st and group two (Group 2) consisted of cows with a shedding score of 4 or 5 on June 1st (AS, 2 levels). Calves from Group1 dams were 11.1±2.8kg heavier at weaning (P<0.01) than calves from Group 2 dams. No significant differences were found between shedding score and BCS. Variance components were estimated using THRGIBBS1F90 and heritability of AS was calculated (h2=0.35) with a moderate genetic correlation with d205WT (rg=−0.58). Hair coat shedding is a heritable trait and could be altered by selection. Producers within the Southeastern or Southern United States who are concerned about heat stress may want to select for cattle that shed their winter hair coat earlier in the season. In conclusion, cows who shed their winter coat by June 1st will wean heavier calves on average.