by: Christine B. Navarre, DYM, MS, DACVIM
Extension Veterinarian, LSU AgCenter, Professor, School of Animal Sciences

We are approaching the time of year when forage quality is at its worse. In some parts of the state we are already there due to lack of rain. There is quite a bit of research about the impact of nutrition on cow reproduction. More recently, research is clearly showing that the nutrition of a cow while she is incubating a calf, from conception to birth, has a major influence on the calf's future health and productivity. While body condition score does not tell the entire story, it is the most important metric to measure cow nutrition. Here are some of the problems that can be encountered if cow nutrition is lacking during gestation of the calf.

Problems in This Year's Calf Crop

Increased Calving Problems
Weak, under conditioned cows have more weak calves and stillbirths, mostly due to prolonged labor. Weak calves are more likely to get sick and die, and they have decreased performance.

Weak Calves
Birth weights of calves will decrease, as will brown fat storage (important for generating warmth). Both are important for calf vigor and survivability in the short term and reducing sickness and death rates.

Sick Calves
Early in gestation, lack of proper nutrition impacts the proper development the organ systems of the calf. The impact specifically to the lungs leads to more calf pneumonia.

Later in gestation decrease in calf birth weight and vigor increases the chances of calves not getting colostrum in time. To compound this, cows that are nutritionally deprived cannot produce good colostrum. Both of these problems lead to failure of passive transfer (FPT) in calves. Calves with FPT are more likely to get sick and die. Even if calves survive an illness, they do not grow as well as healthy calves.

Vaccine Responses
Cows can only respond to a vaccine if they have proper energy, protein and mineral levels in the diet. If a cow isn't taking in enough protein to maintain her body condition, she can't make antibodies, which are protein, and put them in her colostrums for her calf. Therefore, vaccinating cows to protect calves through colostrum will only work with proper cow nutrition. Calf vaccine response is also poor in calves that don't get adequate colostrum.

Nutritional compromise during early gestation also decreases the number of muscle and fat cells that develop. This leads to problems with growth and marbling. Tenderness and feed efficiency are also negatively impacted. Genetic selection for growth and carcass traits is important, but we won't realize those improvements if we don't "feed the genes."

Problems In Subsequent Years

We've known for years that females in poor body condition don't breed back readily. Letting cows drop to body condition score of 4 instead of maintaining them at 5 can drop conception rates by 15 percent. As mentioned earlier, calving difficulties also increase in thin cows, which further decreases conception rates and delayed conceptions.

Replacement Heifers
Calves that don't get adequate colostrum, whether or not they get sick, do not grow as well as calves that get good levels of immunity from colostrum. This difference in growth carries through the feeding period in feeder calves. This translates to increased time to breeding and time to mature weight in replacement heifers.

Lack of proper protein supplementation during pregnancy has been shown to lead to lower average daily gains, delayed onset of puberty and lower conception rates in female offspring. For herds that are retaining replacement heifers, cow nutrition this year can have long-term effects on the reproductive health of your herd. Improper supplementation of heifers has a direct effect on their own future performance, not just that of their calves. It leads to decreased pelvic size, which can affect their dystocia rate for life.

Bottom line

This all adds up to weaning fewer and lighter calves (less pounds weaned per cow exposed) and poor meat quality in the upcoming calf crop as well as future calf crops. So what do we do?

Develop a Sound Nutrition Program
Much of the grass hay produced here is not adequate to sustain a late pregnant cow, and maybe not even enough to sustain an open or early pregnant cow. So we need a supplementation plan for this fall and winter. To avoid overspending or underspending, we need to develop a supplementation plan based on hay analysis and estimates of how much hay actually needs to be fed. Underfeeding hay is not an uncommon problem.

Measure Success
Some years are worse than others from a weather standpoint (cold, wet, mud, and drought), so we have to continuously monitor body condition to make sure we are supplementing enough. But the one time to measure body condition that predicts future productivity and profitability is at calving. Cows that calve in a body condition of 5 or 6 and heifers that calve in a body condition of 6 are more productive than cows that calve in a body condition of 4 or less. The goal is to keep cows in that middle of the road body condition-not too fat and not too thin. We have to keep them there cost effectively, but if we don't we will suffer major losses, many of which are only noticeable with good records, but they are there nonetheless.

Feeding costs are a major expense so developing a winter feeding program that is cost-efficient is imperative while at the same time making sure nutrient requirements are met. In the words of my colleague Dr. Bob Sager, "Feed smart, not cheap." An investment now will pay dividends for years to come.

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