Many producers recognize the importance of cow nutrition, especially during late gestation, because of the influence on the cow's postpartum reproductive performance. However, researchers are discovering cow nutrition during gestation affects fetal growth and development of her calf, which can have long-term impacts on the calf's productivity. Fetal or developmental programming is the term typically used to describe this type of research. Factors such as maternal nutrition, environment, or stressors during gestation can change nutrient supply to the fetus, which can then affect growth and development of organs, skeletal muscle, and adipose tissue. These can have long-term implications on skeletal muscle growth, fat deposition, insulin resistance, or hypertension of offspring, which can impact economically important traits such as growth rate, health, and carcass composition.
A recent study at The Ohio State University, conducted by Amy Radunz in her graduate program under direction of Steve Loerch, investigated alternative energy sources to forage in late gestation beef cow diets. When hay supplies are short, producers are faced with the decision of how to stretch their hay supply or find an alternative feed source. Previous research at OSU has evaluated limit-feeding corn as an alternative to hay in late gestation, and a few years ago this proved to be a less expensive choice. Recently, dried distiller grains (DDGS) has become a more attractive economic option for protein and energy in beef cattle diets due to greater corn prices and increased ethanol production. One of the study's objectives was to investigate three energy sources (hay, corn, and DDGS) in late gestation to determine effects on cow performance and feed costs. Corn and DDGS were fed at a limited intake compared to grass hay fed free access in round bale feeders, because corn and DDGS are more energy dense feeds. The goal was to feed the diets at similar energy intakes during late gestation. No adverse effects were observed in the cow performance during gestation or on postpartum reproductive performance from feeding different energy sources in late gestation. However, feed costs were approximately 24% less for cows fed DDGS as compared to cows fed corn or hay (Table 1).
Although cows consumed a similar amount of energy during late gestation, their offspring's birth weights indicate that these energy sources changed how nutrients were partitioned to the fetus. Calves born to cows fed hay had lighter birth weights than calves born to cows fed DDGS or corn, but differences in birth weights due to cow's dietary energy source were not associated with changes in rates of dystocia (Table 2). At weaning, calves born to cows fed corn and DDGS were 25 to 13 lbs heavier than calves from cows fed hay. No difference were observed in average daily gain, dry matter intake or feed efficiency, but calves from cows fed hay did require more days on feed to reach a similar fat thickness as calves from cows fed corn or DDGS. Hot carcass weights were 28 lbs greater for calves from cows fed corn than for calves from cows DDGS during late gestation. Furthermore, calves born to cows fed corn had the least marbling and lower percentage of carcasses grading in the upper 2/3 of USDA Choice compared to calves born to cows fed DGGS or hay. An economic analysis of the finishing phase revealed a lower net return from calves from cows fed DDGS than calves born from cows fed hay or corn due to lighter carcass weights resulting in discounts to carcass value. These results would indicate that feeding DDGS in late gestation may reduce cow feed costs, but if a producer is retaining ownership on the calves, a lower net feedlot return could result for the progeny. Additionally, these results suggest that amount of marbling in the carcass may not only be determined by genetics, postnatal nutrition, and postnatal management, but also could be determined by what the cow is fed during gestation.
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