June 18, 2024

As calving season progresses, many of us look forward to green spring pastures and summer turnout for the cow herd. However, our cows still have several challenges ahead: colostrum production, initiation of lactation, and returning to estrus prior to the start of breeding season. Closer nutritional management during these periods may help to set your herd up early for a successful breeding season.

Colostrum production begins as early as five weeks prior to calving, and peaks just before birth. The amount and quality of colostrum produced is largely influenced by late gestation nutrition. Near calving it can be difficult to achieve adequate nutrient intake due to the physical constraints that the growing fetus imposes on the rumen, reducing capacity for feed intake. Increasing energy and protein density of the diet will support maintenance functions and fetal growth and colostrum production. Failure to meet nutrient requirements may be at the expense of the cows’ body condition. Cows in good body condition (2.5 to 3.5 on a 5-point scale) that receive a balanced diet produce higher quality colostrum than those who are thin or are fed poor quality diets.

After calving, milk production peaks around 60 days of lactation, this is when a cow’s energy requirements are greatest. While protein is important, typically the most limiting nutrient during peak lactation is energy. Total digestible nutrient and protein requirements on a dry matter basis for a mature cow from mid-gestation to early lactation are outlined in Table 1. Due to the increasing nutrient requirements during calving and lactation, it becomes very difficult and costly to improve body condition of thin cows during calving. Additionally, cows fed nutrient deficient diets will be forced to use body reserves to produce enough high-quality milk for her calf. This could result in reduced milk production and calf performance, and a loss of body condition as the breeding season approaches.

Table 1. Nutrient requirements for mature cows by production stage on a dry matter basis.

Production Stage                 Total Digestible Nutrients                      Protein

                                                 (% Dry Matter)                              (% Dry Matter)

Mid Gestation                                     55                                                    8

Late Gestation                                    60                                                   10

Early Lactation                                   65                                                    12

To achieve the ideal scenario where a cow produces one calf every year, an average gestation length of 283 days allows a cow only 82 days after calving to return to estrus and rebreed. This period between calving and conception is referred to as the postpartum interval. As discussed previously, a cow’s body condition at calving and lactation has a large impact on colostrum and milk production. Perhaps more important is the impact of body condition on the duration of the postpartum interval. Cows in lower body condition take longer to reach their first heat after calving, while cows in good body condition experience higher pregnancy rates and rebreed sooner. Most cows require four to six weeks to return to a normal estrus cycle, this may be prolonged for cows in poor body condition. While adequate nutrition pre-calving is critical to maintain body condition and support colostrum and fetal development, inadequate post-calving nutrition alone can reduce conception rates. Depending on the length of your calving and breeding seasons, the result may be more open cows.

Complicating each of these factors is the influence of cow age. While mature cow requirements may be more easily met, first- or second-calf heifers need additional nutrients to meet their own growth requirements. Failure to meet their growth and gestational requirements increases the risk that these younger cattle may not rebreed, leading to higher open rates and culling of younger animals in your herd. Separating first- and second-calf heifers and thin cows in your herd may allow you to allocate feed resources to those most in need.

While it may be tempting to turn your cattle out to pasture early, set your breeding season up for success by ensuring that your cows nutrient requirements are being met during calving, lactation, and the postpartum interval. For assistance evaluating your feeding plan, contact your local livestock and feed extension specialist by calling the Agriculture Knowledge Centre at 1-866-457-2377.

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