Proper Brood Cow Nutrition
By the Kent Nutrition Department
Nutritional management plays a key role in maintaining optimum performance and profitability in brood cow operations. Cow nutrition is dependent upon adequate protein, energy, vitamins, and minerals in a balanced diet. However, proper supplementation in a ruminant animal means meeting the animal’s needs as well as keeping the rumen microbes healthy.
Rumen microbes can be simplistically classified as either fiber digesters or starch digesters. Cattle on a high-forage diet, typically on pasture, will have a rumen pH in the neutral range. The microbes that break down fiber and make those nutrients available to the animal function well at a pH of 7. On the other hand, cattle in the feedlot consume diets high in starch. The rumen pH of cattle on a high-starch diet will typically be in the mid 5 range. The microbes that utilize starch, function well in a rumen pH of 5.5. If either population is exposed to an acid or alkaline surge, respectively, they tend to be less functional.
A very popular supplementation program in the Midwest is feeding corn to cows on pasture. Given the previous explanation of rumen microbe function, this is a poor method of supplementing energy to cows consuming a high-forage diet.
Oklahoma State University (OSU) conducted a trial in which four groups of cattle were fed free-choice hay with 0, 2, 4, and 6 pounds of corn respectively. As corn intake increased above 2 pounds/head/day, hay intake declined significantly.
In the same OSU study, as corn intake increased above 2 pounds/head/day, the total digestible dry matter decreased significantly. Actually, the total digestible dry matter delivered with 6 pounds of corn and 11 pounds of hay was approximately the same as 2 pounds of corn and 18 pounds of hay. This is what is referred to as a negative associative effect. The more corn that is fed, the less able the rumen is to utilize the forage. The OSU study showed that although corn is high in energy and highly digestible, it affects forage digestion negatively.
Corn is also low in crude protein, and when fed in combination with forages low in protein, results in an ammonia deficiency for microbial protein synthesis.
Feeding more than 2 pounds of corn in a single feeding creates a significant drop in rumen pH and an inadequate amount of ammonia produced in the rumen, thereby reducing the digestibility of forages. This in turn reduces the passage rate of the forages in the gut, reducing the cow’s ability to consume forages. So, not only does this type of supplementation reduce the digestibility of forages, but also reduces her ability to consume forages.
Kent Feeds, Inc. manufactures a long list of products designed to supplement cattle on pasture including cubes, liquids, and blocks. They were all designed to meet the protein, energy, vitamin, and mineral requirements of brood cows without reducing the utilization of forages.