Ken Olson: Managing calving to coincide with forage availability
Choosing the calving season is a complex and highly-individual decision for each beef cattle producer. This leads to a wide-range of calving seasons across the Northern Plains. This became evident recently as we attempted to schedule Extension meetings with 30 producers from across South Dakota. We wanted to have a meeting in February before calving started and another after calving in May. It turned out we could do neither because some participants are already calving in late January and some won’t start calving until the beginning of May.
A primary consideration in pasture-based cow-calf operations is choosing a calving season to match forage-supply to forage-demand. In general, forage production and quality is high in the spring with the peak occurring in early summer, and then supply and quality decline through the remainder of the year as forage matures. The question becomes: Do we match this peak in nutrient supply to the peak in demand by the cows or by the calves?
Matching nutrient supply from forage with nutrient requirements of the calf points to late-winter to early-spring calving. This is because calves that are older and more functional ruminants will be more capable than younger calves at using grazed forage at its peak nutrient quality in early summer. The intent is that calves will be older and heavier at weaning. However, there are disadvantages as well.
The major disadvantage in this scenario is that it is difficult to manage cow body condition score (BCS) during late-pregnancy and early-lactation when calving occurs months before green grass will be available. If cows lose body condition during this period, reproductive performance will be reduced. Extensive use of harvested feeds will likely be required to maintain cow body condition, which will increase annual cow costs. Another disadvantage is increased morbidity and mortality of newborn calves due to cold, wintry weather. Cows in lower body condition produce poorer colostrum and calves are cold-stressed, both of which increase potential for scours.
Matching nutrient supply from forage with nutrient requirements of the cow tends toward late-spring calving. The advantage is that this matches peak nutrient demand of the lactating female with peak nutrient quality of grazed forage. The major disadvantage is that calves are younger and possibly lighter at weaning.
USDA ARS scientists at the Ft. Keogh Research Station near Miles City, MT conducted a study to compare cattle performance and economic response to February, April, and June calving seasons. February- and April-born calves had similar birth weights, while June-born calves were heavier at birth. This suggests better cow nutrition during late gestation for summer-born calves. These birth weights in June were in the normal range and did not cause an increase in dystocia. Weaning weights were reduced as calving season was delayed from February to June, but the difference between February- and April-born calves was minimal (484-, 471-, and 438-lbs. for February, April and June, respectively).
Another important response was that death rate – for February calves it was 3.5 percent, but it was only 1.5 percent for April- and June-born calves. The cows were fed to maintain similar BCS, with the response of interest being the amount of feed required to meet this goal. As expected, the amount of feed required was greater for earlier calving. Despite feeding these higher levels, cows that calved in February and April still lost body condition in late pregnancy, while June-calving cows did not lose body condition. Pregnancy rate did not differ among calving season groups.
If one applies current feed prices to the amount of feed required to maintain a dry, pregnant cow in March and April (i.e. May calving) or a lactating cow in the same period (i.e. March calving), the savings in feed cost because of later calving is about $15 per cow for that period of time. Additionally, the difference in gross income from calf sales based on the differences in weaning weights and calf crop percentage from the Miles City data indicates that April- or May-born calves actually average $3 more per cow than February- or March-born calves. This is due primarily to higher death loss in the winter-born calves. The net effect is $18 more profit from late-spring calves than winter-born calves.
The obvious conclusion that I want to draw is that late-spring calving has advantages over winter- or early-spring calving. First, the perceived improvement in pounds of weaned calves from earlier calving is not likely to materialize. Second, late-winter feed costs for lactating cows are dramatically higher than for dry, pregnant cows, increasing feed costs to support the cow herd. In recent years, escalating feed prices has been a challenge for beef cattle producers, suggesting management alternatives that reduce feed inputs will be important to economic viability. Adjusting the calving season is one of many alternatives to manage nutritional requirements and feed demand by a cow herd.
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