Effect Of Weaning Date On Performance Of Beef Cows & Their Progeny In A Fall Calving

Data from 158 predominantly Angus fall-calving beef cows were used in four consecutive years to determine the effects of weaning date and cow age class on cow and calf performance. Treatments were arranged in a 2 x 2 factorial with 2 weaning dates and 2 age classes (young cows = 3 yr and mature cows = 4 yr). Weaning dates were 1) normal weaning in mid-April at 210 d of age (NW) and 2) late weaning in mid-July at 300 d of age (LW).

* Mature cows were heavier than young cows throughout the trial, although body condition scores were similar among cow age classes.

* Cow body weight and body condition scores were similar among weaning treatments at normal weaning; however, at the beginning of the calving season, normal-weaning cows were heavier (1,290 lb vs. 1,239 lb) and had greater body condition scores (6.6 vs. 6.0) than late-weaning cows.

* Postpartum body weight and body condition score losses were greater for normal-weaning cows, resulting in similar body weight and body condition scores at the beginning of the breeding season and until April.

* Progeny of normal-weaning cows were 5 lb heavier at birth and grew faster before the April weaning date, resulting in increased body weight (18 lb) at the time of normal weaning. This increase in body weight gain may be partially explained by the increased milk production of normal-weaning cows.

* Although normal-weaning calves had increased body weight in April, late-weaning calves were heavier in July because of increased average daily gain during the weaning interval (2.49 lb vs. 1.76 lb).

* A cow age class x weaning date interaction was detected for pregnancy rate. Pregnancy rates were greater for late-weaning mature cows (96.7%) and normal-weaning young cows (98.4%) than for late-weaning young cows (89.3%).

* However, pregnancy rate of normal-weaning mature cows (90.2%) did not differ from that of late-weaning mature or late-weaning young cows, but was less than that of normal-weaning young cows.

These findings indicate that producers may benefit from matching weaning date to cow age class. It appears more advantageous to delay weaning of calves born to dams 4 years or older while maintaining normal weaning for dams 3 years or younger at the time of calving. Late weaning had no detrimental effects on the performance of mature cows.

Source: Hudson et al., 2010, Oklahoma State University

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