Feeding the pregnant cow for calf health and resistance to BRD

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The bovine respiratory disease complex (BRD), sometimes called shipping fever or pneumonia, is an economically-important disease and a leading cause of death loss in beef cattle in North America. Survey data from the National Animal Health Monitoring Service in 2011 suggests that respiratory disease accounts for 29.1% of all calf death losses in the United States. BRD is manifested as a complex of several types of infection with specific causative organisms, clinical signs and related economic impacts. Organisms known to cause BRD include infectious bovine rhinotracheitis (IBR) virus, bovine viral diarrhea (BVD) virus, bovine respiratory syncytial virus (BRSV) and parainfluenza type 3 (PI3) virus. Bacterial agents such as Mannheimia haemolytica, Pasteurella multocida, Haemophillus somnus and mycoplasma are also contributing factors.

Amount of exposure, pathogen virulence and host immune factors all influence risks associated with BRD. The incidence of BRD in calves can be affected by passive immunity received from colostrum and environmental factors such as weather, temperature and humidity. Age, gender, nutritional status, genetics and other factors also affect the incidence of BRD. Vaccination programs, antibiotics and management are key factors in protecting herds and keeping them healthy.

Beef Cow Nutrition and Calf Health
Feeding beef cows to gain maximum profitability can be a challenge. Feed costs are typically the highest input costs in a cow/calf operation. There is a tendency to try to achieve maximum profitability through the use of the cheapest feeds available. This can be a route to quick profits; however, it is rarely a long-term solution. Restriction of certain nutrients through the use of poor-quality feeds can decrease weight gains, reproductive performance and even calf health. Studies have mainly focused on protein, energy, macro- and micro-nutrients and their effects on production and health. Ensuring the requirements for energy, protein, macro- and micro-nutrients are being met is crucial in maintaining reproductive performance of cows and producing healthy calves. Inadequate cow nutrition is related to calf morbidity and mortality. There are critical times in fetal development in which nutritional conditions can affect neonatal health and growth of the calf as well as susceptibility to disease later in life.

Nutrition and Immunity
Nutrition of the pregnant cow can affect the amount of innate immunity passed to the calf through the dam’s colostrum (first milk). Proteins consist of amino acids, which are the foundation for enzymes, antibodies and other functional proteins of the immune system. Antibodies passively transferred to the calf immediately after birth are crucially important in protecting baby calves from disease challenges. Very few studies have looked at the effect of restricted protein diets fed to pregnant cows on immune function of calves.

Protein Nutrition
Feeding poor quality hay, pasture or crop residue commonly provides protein levels below recommendations set by the National Research Council (NRC) for pregnant or lactating cattle. In diets with these low-quality forages, protein is considered the first limiting nutrient. This means that when protein is not present in sufficient quantities in a feed, optimal beef cattle performance cannot occur, even if all of the other essential nutrients are present in adequate amounts. Studies at the University of Nebraska revealed winter diets that provide inadequate protein when fed to pregnant cows in late gestation resulted in lower weaning weights and reduced calf survival. Those studies also showed that meeting cows’ protein requirements resulted in a greater proportion of calves weaned. In addition, the proportion of calves treated for respiratory disease from weaning to slaughter was lower for cows supplemented with protein.

Mineral Nutrition
Metabolism and other life-sustaining activities in beef cattle rely on adequate amounts of macro- and micro-minerals. These nutrients are important components of bones, hormones, enzymes, amino acids, vitamins and antioxidants and have essential roles in water balance and glucose tolerance. At least 17 minerals are known to be required by beef cattle (NRC, 2000).

The micro-mineral status of cows before calving is important for subsequent calf health. Essential micro-nutrients include zinc, chromium, selenium, iron, and manganese. Micro-minerals are transferred from the cow to calf via the placenta to ensure fetal growth. Minerals play a role in colostrum production and therefore are important in passive immunity transfer to the calf.

Meeting mineral requirements involves both accounting for the minerals supplied by the forage and determining if a deficiency exists, and then providing mineral supplements to correct for dietary imbalances. Provision of supplemental minerals is a common practice on beef cattle operations.

Conclusions
Beef cow nutrition not only affects the health and performance of cows, it also has long-term implications for calves from birth to weaning and beyond. The BRD complex is a multi-factorial disease with both short- and long-term implications for beef cattle operations. A variety of stressors are implicated in the occurrence of BRD; management strategies need to address predisposing factors.

Providing nutrients to pregnant cows has been shown to influence calf viability, mortality and immunity. Overfeeding protein and energy is not economical, but care must be taken to ensure nutrient requirements are being met. Cost savings in feeding programs must be weighed against long-term implications of providing inadequate nutrition during pregnancy at critical times in fetal development, which can affect calf health and resistance to BRD long after birth.

 Source: Don Llewellyn, Ph.D., Regional Livestock Specialist, WSU/Benton County Extension and Andy Allen, DVM, Ph.D., WSU Veterinary Medicine Extension.


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