Associate Professor of Animal Science West Texas A&M University Canyon, Texas, United States
Abstract: The objective of this study was to determine sire effects on calf gestation length (GL), birthweight (BW), weaning weight (WW), and intermediate feedlot weight (IFW) in beef cattle. In this study, five sires (four Braunvieh and one Simmental) were used to artificially inseminate (AI) commercial cows in Northwest Arkansas resulting in crossbred calves (n = 76) being born in the Fall 2021. Dates for AI were recorded at time of service in December 2020. At parturition, the calf date of birth (DOB) and a hoof-tape BW were recorded. Calf performance data collection included WW and IFW. Calves were categorized into sire groups (n = 5) and GL groups (n = 3). Sire groups included Braunvieh sire A through D and Simmental sire E. Gestation length groups included Short GL of 264-278d (SGL), Average GL of 279-290d (AGL) and Long GL of 291-305d (LGL). Preliminary data was analyzed using Excel. Through ANOVA, GL groups were determined to be statistically significant (P < 0.05) with means of 276.3±1.8d for SGL (n = 24), 283.2±2.5d for AGL (n = 24), and 300.5±10.3d for LGL (n = 16). When comparing sire groups, no significant differences were found for GL (P=0.39), BW (P=0.71), WW (P=0.64) or IFW (P=0.84) between sires. Descriptive statistics for GL, BW, WW and IFW were 282.0±7.2d, 36.6±6.4kg, 262.3±17.4kg and 544.2±43.0kg for Sire A, 281.7±9.3d, 36.7±15.8kg, 247.8±25.8kg and 532.0±26.4kg for Sire B, 285.6±9.8d, 35.2±14.1kg, 259.8±26.1kg and 528.4±34.4kg for Sire C, 284.5±2.1d, 40.4±0.0kg, 249.5±32.1kg and 532.1±0.0kg for Sire D and 288.5±14.4d, 35.4±10.3kg, 261.7±34.2kg and 542.9±36.8kg for Sire E. Gestation length was found to have no significant differences between bull and heifer calves (P=0.37), with bull calves averaging a higher numerical value of 2.6d when compared to heifer calves. A significant difference was found between bull and heifer BW (P < 0.05). Means BW for bull calves were 11.7lbs heavier than heifer calves. This data suggests GL and BW trends follow previous publications when using GL as a breeding selection tool for commercial beef production.
