Growth Rates of Hip Height, Scrotal Circumference and Weight for Purebred Hereford and Angus Bulls

Story in Brief Seasonal differences and growth rates were studied on 60 Hereford and Angus bulls born in the spring and fall calving seasons at Oklahoma State University. Hip height, scrotal circumference and weight measurements were taken over the two IO-month experiments. Season of birth had no influence on scrotal circumference for either Hereford or Angus bulls. Season of birth in Angus bulls did not show a difference in hip height, scrotal circumference, or weight between spring and fall-born bulls. Hip height and scrotal circumference growth rate, along with average daily gain, showed a linear decline from 6 to 17 months of age in both Hereford and Angus bulls. Hip height growth rate from 180 to 365 days of age averaged .0325 and .0321 in./day for Hereford and Angus bulls, respectively. In addition, hip height growth rate from 365 to 510 days of age averaged .0222 and .0207 in./day for Hereford and Angus bulls, respectively. Scrotal circumference growth rate from 180 to 510 days of age ranged from .0790 to .0000 ern/day for Herefords and .0843 to .0040 cm/day for Angus. Adjustment factors for scrotal circumference at 6 and 12 months of age were .08 and .04 cm/ day, respectively. Average daily gain was faster for Angus bulls at the start of the test than for Herefords, but declined much faster later in the test period. Average dailv gain of Angus bulls from 180 to 510 days of age averaged 2.51 Ib/d av. Hereford bulls averaged 2.42 Ib/day.