Selective Culling and Early Weaning in Drought

From the Cow Sense Chronicle by Rachel Endecott – Beef Cattle Specialist

While forage and pasture conditions are in good shape on the western side of our state, the eastern half is suffering from a worsening drought. Reducing forage demand is an important part of a drought plan and selective culling and early weaning are two strategies that can achieve that goal.

The first level of selective culling is to remove cows with obvious production issues, such as age, bad teeth, feet, or udders, as well as open cows or cows with poor quality calves. The second level of culling is where things get more difficult. There are a couple of approaches to consider, and I suspect most producers would use a combination of them. The first approach is to identify cattle with the most value per unit of forage consumed. These may be young cows and heifers that are products of the most advanced gene cs in your herd. Retaining the young nucleus of the cowherd is important for future gene c improvement, so marketing older cows, some of whom may still be productive, may be the best option to retain a future genetic base.

On the other hand, young cows and heifers have higher nutrient requirements compared to mature cows and are more likely to not breed back. Additionally, young cows and heifers often command a higher premium, so a second approach may be to identify and retain cows who are done growing and will tend to breed back easier in tougher conditions while raising heavier calves.

Early weaning can reduce forage demand in a couple of ways. Lactating cows experience dramatically increased nutrient requirements compared to dry cows. Energy requirements decrease over 20% and protein requirements decrease over 30% as cows move from late lactation to mid-gestation. This decreases the forage intake of the cow, as well as removing the forage demand the calf had been placing on the pasture. One rule of thumb indicates that for every day calves are early weaned compared to normal, about 0.6 grazing days worth of forage are saved. This rule was calculated using a 1300-lb cow who weans a 600-lb calf at 7 months of age. Positive impacts from early weaning are generally observed for cow body condition and reproduction as well. Because of the decrease in nutrient requirements for lactation, more nutrients are available for the cow to partition to body weight gain. Reproductive responses and their timing depend on the timing of early weaning. If the breeding season is already over, cow condition improvements may have an impact on breed back the following year if cows go into winter and calving in better body condition. If early weaning happens before the breeding season (calves around 80 days of age), reproductive performance can be positively impacted for the current year.