Impacts of Heifer Post-Weaning Intake Classification on Performance Measurements of Lactating and Non-Lactating Two-, Five-, and Eight-Year-Old Angus Beef Females

Abstract

Heifer post-weaning intake classification was utilized to evaluate subsequent intake and performance measurements of 2-, 5-, and 8year-old lactating and non-lactating Angus females. For both studies, heifers were categorized based on voluntary feed intake (expressed as g/kg BW) as either low (<−0.50 SD from the mean), average (± 0.50 SD from the mean), or high (>0.50 SD from the mean) within one year. Intake and production data of pregnant, non-lactating (n = 59; Study 1) and lactating, non-pregnant (n = 54; Study 2) females were evaluated. Heifer post-weaning voluntary feed intake was calculated over 80 test days post-weaning using GrowSafe feed intake units. Cow body-weight (BW) for non-lactating cows showed a tendency for age × intake interaction (p = 0.10), with older cows weighing more than younger cows. Milk production expressed as kilograms and g/kg BW of the cow had an age × intake (p < 0.001) effect. Two-year-old cows with low- and average-intake classifications had greater milk production (p < 0.001) and milk produced expressed as g/kg BW (p < 0.001) than 2-year-old cows with high-intake classifications. Additionally, 5-year-old cows with average and high-intake classifications had greater milk production (p < 0.001) and g/kg BW (p < 0.001) compared to 5-year-old cows classified as low-intake. In summary, heifer post-weaning intake classification had minor impacts on performance measurements in the three age classes of beef females at two different production levels.

Impacts of Rumen Degradable or Undegradable Protein Supplementation on Supplement Intake and Performance of Yearling Heifers and Cows Grazing Dryland Pastures

“…Additionally, Sowell et al [ 13 ] noted that herd structure and dynamics may also play a role in supplemental feeding, with older, dominant cattle over consuming supplement compared to younger, less dominant cattle. Moreover, Wellnitz et al [ 14 ] observed similar results with 5- and 8-year-old cows consuming more total feed than 2-year-old cows, regardless of pregnancy or lactation status. However, this was attributed to overall rumen capacity, which also may have played a role in the current study.…”