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| The common tradition for weaning spring-born calves is to wait
until late October and even early November. Most mature cows that
have been feeding on adequate summer forages will be in very good body
condition, despite the pressure of nursing a rapidly growing calf.
These cows will still be in a body condition score of about 6 at weaning
time each fall. However, very often two-year-old cows and even some
three-year-old cows will be in marginal body condition at the end of summer.
They have a nutrient requirement for continued growth and in the case of
the two-year-old, they are replacing baby teeth with adult teeth and are
not good forage harvesters. Therefore many of these young cows go
into the fall season in a body condition score of 5 or less.
If the rancher chooses to wait until late October to wean the calves from these marginal young cows, there is very little time between weaning and the first killing frost. This is a time when a young cow could recover consider body condition, if she has access to a plentiful supply of late summer, warm season grass. Without the nutrient drain of producing and delivering milk, she can use this pre-frost period to great advantage and replenish her own body stores. South Dakota State examined this scenario (albeit using mature cows) by comparing the effect of weaning date on performance of the beef cows. They weaned half of the cows at the time of the first real cool spell (September 14). The other half of the cows had their calves weaned at a traditional time (October 23). The scientists then monitored body condition and rebreeding performance of the cows. We should note that this study included two different nutritional levels: A low group to mimic an early winter or a dry summer; A moderate group to mimic more ideal summer and early winter seasons. Only the data for those cows exposed to the low nutritional group are presented here. They more nearly reflect what may happen for 2 and 3 year olds than will the moderately fed mature cows. Weaning time September 14 October 23 December body condition +.5 ----- % cycling 1st 21 days of breeding 83 74 % pregnant to 21 day AI 70 35 Average conception date June 26 July 3 This data indicates that the 40 days earlier weaning allow the cows to regain 1/2 of a body condition score going into winter. More of the early weaned cows were cycling at the start of the breeding season, conceived early in the breeding season and should wean heavier older calves they following year. In addition a small amount of high protein supplement (i.e. cottonseed meal or soybean meal) will enhance the cow's ability to utilize the declining quality of the late summer forage. Therefore adding more body condition to the young cows before frost arrives. This combination of management techniques should be a cost effective way to increase re-breeding rates of young spring calving cows.
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