By Dr. Connie Swenson, Research Nutritionist, and

Dr. Bruce Johnson, Director, Research & Nutritional Services

Zinpro Corporation, Eden Prairie, Minn.

Reproduction in the beef herd is an important factor in attaining profitability. Good management practices and providing balanced nutrients are critical for maintaining cow and bull fertility. In addition to protein and energy, adequate trace mineral intake and absorption is required for reproduction. Reproductive performance may be compromised if zinc, copper, manganese or selenium levels are marginal to deficient.

Common copper deficiency symptoms in cows include delayed estrus, decreased conception rates, infertility and early embryo death resulting in more open cows in the fall. Inadequate zinc levels are associated with decreased fertility and increased dystocia and retained placentas. In bulls, zinc deficiency causes lower fertility due to poor sperm quality and reduced scrotal circumference. Manganese deficiency in cows results in lower conception rates, presence of silent heats and abortion. Male reproductive performance is affected by low manganese status that inhibits libido and lowers spermatozoa numbers. Another consideration for bull fertility is bone soundness and the ability to travel. Zinc, copper and manganese are needed for skeletal development and maintenance as well as hoof integrity. A bull suffering from lameness or joint problems will breed fewer cows.

In areas that have selenium deficiencies, a producer may see an increase in retained placentas, more open cows in the spring because of embryonic degeneration followed by fetal resorption, and higher early calf mortality due to decreased fetal development. Selenium deficiency in bulls decreases spermatogenesis, the development and maturation process for sperm.

Feeding beef cattle complexed copper, zinc, manganese and cobalt has been shown to enhance reproductive performance early in the breeding season. Research results indicate that cows supplemented with complexed trace minerals have confirmed pregnancies 10 days earlier. Getting cows bred earlier after calving can help to shorten the breeding period and allow for a heavier calf the following year at weaning. Breeding females fed complexed minerals have shown a 35% improvement in AI conception rates compared to those fed inorganic forms. In another study, heifers fed complexed zinc and copper produced more eggs during ovulation. Increasing ovulation rate adds insurance for the success of all breeding programs.

As producers look at their mineral programs, there are two important considerations. First, the best approach to supplementation is to include a balance of all minerals that impact production. Increasing the level of a single mineral due to identified deficiencies can create an imbalance, an antagonistic effect, on another mineral. For example, zinc and copper become antagonistic if either mineral is supplemented at extremely high levels. Optimum copper: zinc ratios are 1:3 to 1:5. Secondly, the strategic period for use of complexed trace mineral to improve reproduction is 60-80 days precalving through 60-80 days after calving. This target period applies to a majority of the herds; however, the period may need to be lengthened if trace mineral problems are more severe.

Bottom Line: Reproductive performance in beef cattle relies on balanced nutrition of which trace minerals are an important component; feeding complexed forms of copper, zinc and manganese can make a difference.

For more information on complexed trace minerals, you can visit the website for Zinpro trace minerals at www.zinpro.com .

For Farmland Land O'Lakes minerals containing complexed trace minerals, visit your local cooperative and ask for the Techni Breeder line of minerals.