Nutrition is Key for Successful Reproduction

By Paul Davis, PhD

"A calf from every cow, every year" is the common goal and expectation given to beef brood cows across the farms and ranches of our great nation. Beef cattle reproduction is the foundation for profitability and failure to do so is a foremost criterion for culling. Unless calves are conceived, born and weaned, neither the commercial cattleman nor seedstock producer has a product to sell.

Unfortunately, the goals and priorities of cattleman are not the same for the cow. While the producer's focus is profitability, the cow's is merely survival. In fact to help assure her survival, a cow utilizes a process called nutrient partitioning. In other words, certain biological processes are prioritized with regard to where nutrients are first used. Those priorities are generally as follows: basic metabolism (staying alive), lactation, growth and reproduction.

Since the cow determines where and how nutrients are used, let's examine each of these in further detail from her point of view. It makes sense that survival or continuation of life is priority one. In a time of malnutrition or starvation, an animal will use nutrients to fuel basic processes such as breathing and enough locomotion to find and ingest food and water. Second, if a cow has a calf at her side, after taking care of herself, she will spend nutrients to lactate and produce milk for the liability she has in the form of the unweaned calf. Third, if a cow is not mature, she will use nutrients for growth after she has provided milk for her calf.

Last, but certainly not least in the eyes of the producer, the cow will use nutrients to fuel her estrous cycle in order to rebreed and conceive. In her world, the conception of a calf means an additional responsibility and a consumer of more nutrition.

Hormones are responsible for the "chemical signaling" that communicates adequacy or deficiency of nutrients. Receptors in the brain assess this status and determine whether or not "life is good" from a nutritional viewpoint. Simply put, if a cow is starving for calories, lacking in dietary protein or deficient in vitamins and minerals, it is unlikely that she will cycle and conceive until her nutritional status improves. Therefore, nutrition has a massive influence on accomplishing the aforementioned goal of a calf from every cow every year.

Fortunately, owners and managers of cattle operations are able to determine the level of nutrition that their brood cows receive. Evaluating the body condition or fleshiness of cows is a simple yet effective method to assess nutritional status.

The act of analyzing forages to determine their nutritional content is the first step in providing the nutrition that is necessary for a successful breeding program. Once the nutritional contribution from forages is known, producers can begin to build supplement programs to span the gap between what the cow must have to accomplish the goals set forth for her and what the forages provide.

In many grazing situations, energy is the nutrient most likely deficient. It is required in the largest amount and has a colossal effect on the chemical signaling that communicates nutritional status. Trace minerals such as copper, zinc, and selenium are known to be lacking in many forages and play key roles in processes associated with reproduction. In some instances, dietary protein may also be lacking.

Designed to overcome nutritional deficiencies, supplemental feeds are formulated to provide supplemental energy and/or protein, and come in several forms such cubes, pellets, or self-fed supplements such as blocks, tubs and liquids. Vitamin and mineral inadequacies can usually be overcome via the provision of what most producers know as "free-choice mineral".

In a word, when brood cows fail to receive adequate nutrition, certain chemical signals communicate that "times are tough". Upon receiving such signals, the cow fails to cycle and conceive, whereas not to take on another liability in a situation where her own survival is uncertain. Provision of supplemental feeds and mineral mixtures allows us to provide the cow with adequate nutrition and the indication that "times are good; there is plenty to eat". In turn, she is willing and able to accept the responsibility for another life, rebreed and conceive. (C)