Beef cow nutrition and its impact on herd productivity has long intrigued me. Initially, like many, my primary focus was on protein, energy, and ensuring mineral availability.
While we knew cow nutrition influenced calf performance and health, the main priority was getting cows bred back.
However, groundbreaking work in fetal programming by researchers such as Ford, Funston, Mulliniks, Vonnahme, Cooke, and others since the early 2000s has shifted this perspective.
Research has shown that protein supplementation for cows grazing low quality forage during late pregnancy significantly affects the feed yard and reproductive performance of the in-utero calf.
Equally important is the impact of micronutrient supplementation (trace minerals and fat-soluble vitamins) during late pregnancy on the immune system function from birth to harvest.
Gestational nutrition influences muscle and fat cell development, placental development, and organ development, including the heart.
This means fetal programming affects the lifetime health and performance of the in-utero calf and is often referred to as the developmental origins of health and disease.
Consider a case involving a 400-cow commercial and seedstock herd with a 5-year history of scours at 10-12 days of age, affecting about 50% of the calves.
Numerous pathogens had been incriminated and despite various treatment and prevention strategies, the issue persisted, along with a 4% death loss each year due to summer respiratory disease.
As we begin to try to understand this problem the first question is, “Why is this occurring?”
Given the number of different pathogens that had been incriminated, the first possibility is that there is immunodysfunction in these young calves.
The next question is “Why is immunodysfunction occurring?”
Because of its immunosuppressive effects, the first possibility would be bovine viral diarrhea virus. Another possibility would be a micronutrient deficiency occurring in late gestation.
Key trace minerals such as copper, manganese, selenium, and zinc, along with vitamins A and E, play critical roles in neonatal physiological processes, including immune system function. Here is a closer look at their roles:
Copper is vital for enzyme systems associated with energy metabolism, immune function, and reproduction and is involved in antioxidant defense.
Deficiencies can reduce antibody formation, alter immune cell function, and decrease cytokine formation.
The reproductive effects of copper deficiency are observed as decreased conception rate, infertility, anestrus, and fetal resorption. Molybdenum, sulfur, iron, and selenium act as antagonists to the absorption of copper
Manganese is essential for enzyme systems impacting growth, bone development, and reproduction as well as playing a role as an antioxidant.
Deficiencies can cause skeletal abnormalities, contracted tendons, and poor growth.
Reproductive issues include cystic ovaries, silent heats, low conception rates, and testicular atrophy.
Selenium is crucial for immune function, reproduction, and antioxidant enzyme support.
Deficiencies can lead to white muscle disease; reduced growth rates, feed efficiency, and immune function; and reproductive performance issues.
Areas of excessive selenium exist in the Great Plains, particularly in the Dakotas and northwest Kansas in addition to a few areas in the Flint Hills.
This excess affects the immune system, musculoskeletal system, and reproductive system. It also acts as an antagonist to the absorption of copper and zinc.
Zinc is involved in over 300 enzymes related to metabolism, growth, reproduction, and immune function in addition to epithelial health.
Deficiencies can lead to reduced cellular and humoral immunity as well as impaired growth.
Zinc, in conjunction with vitamin A, plays a role in the integrity of tight junctions in epithelial surfaces throughout the body including the respiratory tract, intestinal tract, testicle, uterus, and mammary gland.
Zinc dependent enzyme systems are involved in the conversion of beta-carotene and retinyl to vitamin A in the intestinal mucosa.
Vitamin A is a fat-soluble vitamin that serves as an antioxidant in addition to being involved in the immune system and reproduction.
Deficiency is observed as reduced growth, humoral immunity, cellular immunity and reproductive performance. It is also associated with a high incidence of
neonatal diarrhea.
In synergy with zinc, it plays a role in tight junctions of essentially every epithelial surface in the body.
Reproductively, vitamin A is necessary for placental, testicular, and ovarian function. Abortion has been associated with this deficiency.
Vitamin E is also a fat-soluble vitamin that has antioxidant activity. Deficiency of this vitamin will result in white muscle disease in addition to impaired immune response, weak calves, poor growth rates, and sudden death.
Deficiencies of vitamin A and vitamin E can increase the expression of selenium deficiency because of the antioxidant activity of these vitamins.
In the case herd, a vitamin A deficiency was confirmed in a calf that was born blind. This served as an additional indicator of the possible cause of the issues in this herd.
A herd plan was developed to evaluate trace mineral and vitamin A status in the cows when they came off of summer grass.
Liver biopsies and serum analyses revealed that the cows were copper deficient and essentially devoid of vitamin A.
A custom mineral supplement was developed and provided to the cows beginning in early fall, with the results being transformative. The next calving season saw only one calf treated for scours.
Appearance, of both the cows and calves was significantly improved. There was no summer respiratory disease, and the calves were 75 pounds heavier at weaning.
Financially, this resulted in an estimated additional gross income of $71,820, with additional mineral costs of $8,000, resulting in a net income increase of $63,820.
The primary source of trace minerals for the fetus is the transfer of trace minerals from the dam to the fetus that occurs during the third trimester of gestation.
This transfer provides the necessary trace minerals for optimal immune function the first 50-60 days of life and demonstrates the importance of adequate mineral supplementation during late gestation.
While very small amounts of the fat-soluble vitamins A and E cross the placenta, the primary source of these vitamins for the neonate is colostrum, illustrating the need for supplemental vitamin A and E during late pregnancy.
Since these vitamins are fat-soluble, it is necessary to ensure adequate body condition during this time so there is adequate body fat to transport the vitamins.
Recent work at the University of Nebraska demonstrated that vitamin A must be provided with 3-5 times the daily requirement in order to replete liver levels in cows that are devoid of the vitamin.
Points made by Dr. Jeffery Hall, former toxicologist at Utah State University, when discussing summer respiratory disease in cow-calf operations include:
Nutrition has been discussed as a risk factor in the occurrence of summer respiratory disease in cow-calf operations.
Nutrition consists of big rocks, protein and energy, and little rocks, minerals and vitamins.
Many times we concentrate on the big rocks and as long as a mineral supplement is provided, we assume that the little rocks are adequately addressed.
This case study underscores the profound impact of proper micronutrient supplementation on beef cow herd health and productivity.
By understanding and addressing micronutrient deficiencies, ranchers can enhance immune system functions, improve calf health, and achieve greater economic sustainability.
It is about doing the ordinary things extraordinarily well. This approach not only supports better stewardship but also creates substantial value in a ranching operation.
Stewardship: The careful and responsible management of resources that God has entrusted to one’s care.
A native of southwest Kansas, Dr. David Rethorst attended Kansas State University where he received his DVM in 1978. He spent 35 years in primarily beef cattle practice in south central Nebraska and northwest Kansas before accepting a position as the Director of Outreach for the Beef Cattle Institute at Kansas State University in 2013. Returning to private practice in 2017, he is currently mentoring young veterinarians in three practices in addition to serving a clientele of beef producers. His preventative approach focuses on basic animal husbandry, especially nutrition in the cow herd, rather than more vaccine and more antibiotic.
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