By Sandy Johnson, Extension Beef Specialist, Colby
The timing and length of the breeding season are typically set and not reviewed on an annual basis. However, things can change over time and the range of weather conditions we have experienced in the past several months give us other reasons to re-visit those plans.
For operations calving during the extreme cold spell in February, the ability to manage was challenged even with the best of resources. A full discussion on the best time of year to start the calving or breeding season is beyond the scope of this article but a few points warrant discussion this year. Extreme weather events occur from time to time but there is some indication we should expect more variability and extremes going forward. This year reminds us to ask if the timing we have been using is still optimal for the assets available. Calving can be very physically demanding work and more so in harsh weather. What worked 20 years ago may not be the best plan today. It is OK to consider change.
In terms of this breeding season, given your grazing resources and the condition of cows this year, is the planned starting time still in order or would a short delay be advantageous?
Grazing resources – In parts of Kansas, grass growth has been slowed by cool temperatures and dry conditions. The start of the grazing season should be determined by plant growth so that there is sufficient plant leaf area to replenish carbohydrate stores lost over the winter and needed during green-up. Turning out too early can stress plants, allow weed encroachment, and reduce total production. It can also mean that cattle may not be able to find enough forage to meet nutrient requirements and grazing more hours of the day further increases energy requirements. A drop in nutrient intake from a calving diet (e.g. drylot ration meeting peak lactation requirements) to a marginal amount of grass could delay the resumption of normal estrous cycles. In yearling heifers, it could stop cyclicity until nutrient intake improves.
Cow condition. Several factors influence how soon cows resume normal estrous cycles after calving including body condition, age, and calving difficulty. Mature cows in adequate body condition should resume normal estrous cycles 45-60 days after calving. As cows are shedding winter hair coats, cows coming in heat may be obvious by a bald tail head. Depending on the past calving distribution it would be reasonable to see 2-3% of the group in heat per day the week before the planned start of the breeding season. If no sign of estrous behavior is evident and or cows are in poor body condition, few cows are likely to conceive early.
If only a small proportion of the herd calved in the first weeks of the calving season and grass and cow condition are marginal, delaying bull turnout will help tighten the next calving season.
The length of the breeding season may also be reconsidered if several conditions align to reduce numbers of cows conceiving early. Factors could be marginal cow condition, extended poor forage growth, or flash droughts. While a relatively short, front loaded calving season is optimal, if conditions result in poor early conception, leaving bulls in longer may increase final pregnancy rate. And even if late bred cows no longer fit your production system, a bred cow is worth more than an open cow. Monitor bull activity during the breeding season and expect it to start high and decline. Knowing when cows become pregnant during the breeding season can be valuable information for management decisions (drought destocking, routine culling). Discuss options and precision for staging pregnancies with your veterinarian and use the information to your advantage.
The start of the grazing season and breeding season should factor in current conditions. Growing conditions in some parts of the state have increased the situations where adjustments deserve consideration this year.
