Winter Cow Nutrition Impacts Reproduction
Feb 22, 2010
Dr. Dan Larson, Ruminant Nutritionist
Managing a dry cow during the winter is often overlooked. Yet, it is a critical period for calf production and to get the cow in condition for a successful breeding season. The goal of a cow management strategy is to limit cost without sacrificing calf production or rebreeding.
Often the second trimester is considered the best time to save dollars invested in feed. This is a period of minimal fetal development; however, the growing calf still has a requirement for protein and energy. Between 4 and 5 months before calving, the gestating cow requires 1.7 to 2.0 lb of protein per day. This would mean that a cow grazing dormant grass or cornstalks or consuming low quality hay with an average of 7.0% protein would still require 0.3% protein. Providing about 1 lb per day of dried distiller’s grain or 2-3 lb of good quality hay would meet her protein requirements. Provided there is adequate forage, a cow whose protein needs are met will consume enough dry matter to meet her second trimester energy requirements.
That nutrition 101 lesson is a lead-in to a beef cow reproduction 400 discussion. While the afore mentioned level of protein is necessary to maintain cow weight and body condition, it is also imperative to calf development. As I mentioned, the calf, while not growing appreciably, is developing. During the second trimester of pregnancy, the organ systems are developing and acquiring functionality needed later in life. It is tempting to save money by restricting nutrient intake of the cow if she is in good body condition, especially by limiting expensive protein feeds. While this strategy may not cause any appreciable weight loss by the cow, substantial protein restriction may have long-term effects on the calf. Any effect on the calf will likely be magnified in the young cow, who in addition to providing for a calf, is still growing herself. Work with your nutritionist to formulate supplement that will meet the needs of the growing cow and maintain condition on the mature cow.
The most obvious period of increased nutrient requirements is during the third trimester. Nearly 75% of fetal growth occurs during the last 60 days of gestation. It is obvious that a cow’s nutrient requirements are going to increase concurrently. A cow’s protein needs jumps to 2.5 lb per day during the third trimester. Not only is this increase necessary to maintain cow weight and condition, but added protein during the last 100 days of gestation might alter calf development. Steer calves from dams provided added protein during late gestation may be heavier at weaning, healthier in the feedlot and have higher quality grades. Heifers from protein supplemented dams may also have enhanced reproduction later in life. More noticeably, calves from cows that are adequately nourished are healthier at birth, likely due to improved colostrum quality. Clearly, nutrition plays a huge role in reproduction.
Beyond calf production, proper cow nutrition is also essential for rebreeding. This is most evident in the growing female, the bred heifer. Body condition scoring is an integral tool for cow management. As a rule of thumb, target an average condition score of at least 5.5 for mature cows and a score of 6 for heifers entering the calving season. A cow calving at a body condition score of 4 will start cycling up to 40 days later than the same cow that calves at a condition score of 5.5. In order to maintain a 365 day calving season, the post-partum interval has to be less than 85 days, which a cow in a condition score of 5.5 can achieve. However, the condition 4 cow will require 135 days to rebreed and eventually fall out of the herd. The transition from a late gestation diet to an early lactation diet is also extremely important for rebreeding. A cow’s protein and energy requirements increase by approximately 25% following calving as she enters early lactation. The 25% increase is necessary to maintain body condition. It is more efficient to maintain a cow at a condition of 5.5 pre-calving than to play catch up after calving.
The take home message is to create a nutritional plan that makes use of cheap feed sources when cow requirements are lowest. Save the higher quality feedstuffs for the late gestation and post-calving periods. In addition to rebreeding, nutrition of the cow affects the calf and can alter lifelong productive ability. In addition to protein and energy, a diet that meets trace mineral and vitamin needs will improve newborn calf health and viability. Contact your nutritionist to develop a cow management plan to minimize cost and maximize production.
-Dr. Dan Larson is a ruminant nutritionist at Great Plains Livestock Consulting, Inc. The consulting service was founded in 1998 by Dr. Ki Fanning with the goal of becoming the premier animal agricultural consulting company for feed manufacturers, producers, and entities engaged in the areas of livestock production, with the reputation of the highest integrity and quality of service.