Calving Management

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Pre-Calving Nutrition

The first and most important thing when it comes to pre-calving nutrition is knowing not only what you are feeding but what you are feeding it to. The best dollar-for-dollar return on investment for the cow herd is a nutrient analysis of all feedstuffs fed to the cows. Without that, the supplementation strategy becomes guess-and-check. If you are over-feeding, you are wasting money; if you are underfeeding, you are wasting potential production.

Table 1 Beef cattle nutrition workbook

Nutrient requirements

Along those same lines, knowing what your cows really weigh is just as important. For example, balancing a ration for a 1200-pound cow that in reality weighs 1350 likely will result in significant losses in body condition leading into the calving season. For ration balancing assistance, please visit the Beef Ration and Nutrition Decisions Software (BRaNDS) webpage. Furthermore, many producers still believe they have the prototypical 1200-pound cow. However, according to the U.S. Meat Animal Research Center (USMARC), the average mature Angus cow likely weighs in excess of 1400 pounds. Data suggests that commercial cow weights have increased by 200-300 pounds since the mid-1990’s. If scales are not easily accessible, using your cull cow weights from the sale barn will get you closer than guessing. The table here outlines the minimum nutrient requirements of mature beef cows in the third trimester, but does not apply to pregnant heifers or 2-year-old cows.

Body condition and energy balance are imperative as calving season approaches. Energy and protein requirements increase rapidly in the third trimester compared to the second trimester of pregnancy, as the majority of fetal growth is occurring during this time period. Because of this, improvement of BCS can be costly. Therefore maintaining/improving BCS during the second trimester is often the most effective. Once the cow is in her third trimester, make sure to begin providing adequate amounts of CP and TDN to assist the cow in providing enough energy and protein to the growing fetus to ensure proper fetal development, cow colostrum development, energy to calve, and subsequent calf health. The size of the fetus also may impact the cow’s ability to consume enough lower quality forages to need these requirements, so consider saving your better quality forages and readily digestible supplemental feedstuffs for the third trimester.

Meeting not only energy and crude protein requirements, but also mineral and vitamin requirements during this period are critical. Most vitamins are synthesized in the rumen, with the exceptions being Vitamin A and E which can be derived from consuming green forages. Thus, in years where grazing periods are extended or high quality hay can be sourced, vitamin deficiencies are rarely of concern. However, keep in mind that mature first-cutting, rained-on or CRP hay, cornstalks, and even hay that has been stored for extended periods, will most likely be deficient in vitamins A & E and require supplementation.

Insufficient vitamin supplementation when feeding or grazing low quality forages will result in cows rapidly depleting their liver stores of vitamins A and E. Many times, dams may not show signs of dietary imbalance as Vitamin A and E deficiency often does not result in loss of body condition score; however, the problem can easily manifest itself in the newborn calf with clinical signs of deficiency including stillbirths, blindness, and white muscle disease. All of these problems have been prevalent in the Midwest over the past few years, with likely culprits including a combination of drought and increased utilization of cornstalks in many operations.

In addition to conscientious supplementation of vitamins A and E when other dietary vitamin sources may be low, determining vitamin status of cattle in mid gestation may be of benefit if it is in question. This timing is crucial because if a correction in the diet needs to be made, there is enough time to do so before the dam reaches late gestation. This is imperative as it is difficult to make a change in the diet during late gestation that ensures the cow will be in adequate vitamin status at calving.
 
Many questions about supplementation arise from producers who do not want to supplement cows during third trimester because of fear that it will make birth weights increase. While there is some data that would support this, there also are many studies that have shown no differences in birth weight resulting from plane of nutrition as well as studies that show no difference in dystocia rate associated with additional supplementation. But in the end, the real concern is dystocia, not necessarily birth weight. Thus, many breed associations are starting to place less pressure on the birth weight EPD and focus more on calving ease direct (CED) and calving ease maternal (CEM) EPDs. Calving ease EPDs focus on dystocia, not solely birthweight.

One way to minimize dystocia is to have cows in a moderate body condition at calving. Obviously, over-conditioned cows are prone to dystocia due to excess fat along the birth canal. However, under-conditioned cows are just as prone, if not more so, to dystocia. It takes energy to make energy, and one of the most energetic things a cow has to do all year is calve. If she doesn’t have the proper muscle tone and energy reserves, she will wear out sooner and increase the need for assistance. Multiple studies have reported an increase in rate of dystocia for cows that were underfed during the third trimester when compared to cows on an adequate plane of nutrition. Therefore, supplementation for cows under moderate body condition is critical during the third trimester.

Perhaps just as importantly, the extended benefits of moderate body condition at calving are improved calf vigor, colostrum quality, and calf health during the pre-weaning period. Studies have shown that calves born to a cow with a BCS of 5 take a third less time to stand when compared to a cow with a BCS of 4. Furthermore, cows with a BCS of 5 or 6 have significantly more colostrum production and increased immunoglobulin concentrations when compared to thinner cows.

Even before fetal programming was known as such, research from the 1970’s showed the importance of gestational nutrition on neonatal health. This research compared cows on a continuously low plane of energy during the last trimester of gestation and compared those females with cows fed a low plane of energy for 70 days, followed by a high plane of energy the last 30 days before calving. Even though birth weight was increased in the group fed a high plane of energy for the last 30 days, the cows lost less weight, had 30% less neonatal death loss and 37% less neonatal scours, and calf weaning weights that were 9% heavier, highlighting the monetary returns of a proper gestational nutrition program.

Contributors
Grant Dewell Renée Dewell Katy Lippolis

Associate Professor
Vet Diagnostic & Production Animal Med
gdewell@iastate.edu
515-294-2822

Veterinary Specialist
Center for Food Security/Public Health
rdewell@iastate.edu
970-231-9654