Reproduction starts with Nutrition

 By Jaclyn Krymowski

 Reproduction and parturition are perhaps the two most demanding life processes we, or nature, can demand of an animal. While these functions are certainly hardwired, built into the very nature of living things, they are also rather delicate, able to be influenced on multiple levels. With this in mind, its no surprise one cornerstone to reproductive and calving success is as simple as proper nutrition, aligned with the unique needs of the geographic region, age, breed, and physiology.

As with many parts of beef production and management, there can be no one size fits all to nutrition. It takes a lot of skill and the right team to create the most optimal diet. Luckily, plenty of research and practical application has told us there are some fundamentals to start with.

Know the standard
TArmed with the powers of research and generations of experience, the beef industry has had the luxury of establishing some benchmark numbers to make goal setting easier. The “gold standard” accepted industry wide is breeding back by 85 days (this keeps you on track for a regular annual calving and prevents late lactation outliers), maintaining a 60-day calving  window (for optimal cohesiveness and management), and cows being at a body condition score (BCS) of 6 before and at the time of calving (this allows the cow to heal faster post-calving and with higher odds of success rebreeding). Nutrition can help keep you on track for all of these.

It is in the 60 days post-calving that a cow’s nutritional demands on her body are highest. This is due to the body repairing after the strain of calving and lactating whilst maintaining body condition. And if you’ve kept your calving window relatively tight, you will have the whole group with similar needs.
At this time, protein and energy needs are especially important. To meet these, the total digestible nutrients (TDN) density of the ration, including forages and any other supplementation, should be in the anywhere from 58-60%. Crude protein should be 10-12%.

If you go a little further back, the nutritional needs of replacements must be established well before their first calf is ever on the ground. Generally, you want a heifer to be at least 60-65% of her mature body weight around breeding. This way, by the time she calves, she will be 80% of her mature weight if she was fed properly. In fact, the energy requirements tend to be a bit higher for first-calf heifers because they need to account for individual growth whilst growing a calf. Inadequate energy is a major culprit for poor rebreeding.

It starts with your heifers(and young bulls)
Although they are young and not yet “working,” your heifers demand some of the highest quality nutrition you can provide them with. Virgin heifers are potentially the most fertile group in the herd.

Again, the 60% mature weight at breeding and 85% mature weight at calving especially holds true at breeding aged heifers. Average daily gain is a good way to keep animals on track for reaching appropriate weights at maturity. There is much variation among breeds, so you will need to customize the numbers for your herd (tables, charts and resources abound for these, especially with your appropriate breed association), but a growing replacement heifer can generally expect to gain anywhere from half a pound to two pounds a day if fed properly. Bulls tend to fall into the one to three pound a day range.

In these young and growing animals, energy requirements are higher than their more mature herdmates. Remember, you must account for maintenance, reproduction and growth all at the same time. This where you want to be investing your highest quality forages and feed components.

Vitamins and minerals matter
When you break down nutrition some of its most basic building blocks, you come to vitamins and minerals. Your region and feed components are where all the variation comes from. Remember, your animals can only perform as much as the most limiting nutrient in their diet will allow. Now this is one area where there’s quite a bit of room for further research, but we do want to pay mind to what we currently know.

According to the University of Arkansas Division of Agriculture Research and Extension, the vitamin most likely to be deficient in typical beef diets if vitamin A. They recommend 1,273 IU/lb. dry feed for pregnant beef heifers and cows; and 1,773 IU/lb. dry feed for lactating cows and breeding bulls.

Another crucial vitamin is vitamin E, but determining its requirements are difficult due to interrelationships with other components in the diet. While the exact numbers are not yet well established, it is estimated that 16 IU/lb. feed dry matter is sufficient enough for most animals.

Some of the most important minerals involved with reproduction include phosphorus, copper, iodine and manganese. The tricky part is, these are subject to change based on the needs of the cow and her unique individual physiology. The quality of forage will have a big impact on how deficient a herd may or may not be for certain minerals, such as for phosphorus and calcium.

Iodine is one mineral that is widely deficient in many regions due to soil composition, but luckily the solution can be as simple as putting out an iodized salt block. Putting out trace minerals is another good solution to address micromineral concerns like manganese and copper.