The Cow-Calf Manager:
Last Chance to Get Cows in Condition for Breeding
Livestock Update, March 2000
John B. Hall, Extension Animal Scientist, Beef, Virginia Tech
The time between calving and the start of the breeding season is a very crucial time, especially this year. With all the stress of calving time, it is often easy to overlook the nutrition program and for cows to accidentally lose condition and get in to nutritional trouble. Those 80 to 90 days between the first calf and the start of the breeding season often pass by very quickly.
Hopefully, most cows are in good body condition (BCS 5 or better) going into calving. However, weight changes between calving and breeding can have dramatic effects on re-breeding success. If the cow's nutritional requirements are not met between calving and breeding, she can lose weight in a hurry. The weight loss can be especially severe in 1st calf heifers and heavy milking cows. In a study I did in Georgia, first calf heifers that received 82% of the energy they needed (hay without any grain supplement) lost over 1.3 lbs. per day. These heifers had lost 1.5 body condition scores by the start of the breeding season. So you can see even when animals are fed all they can eat in hay, they can still lose weight quite rapidly.
Figure 1. Effect of Body Condition at Calving and Weight Change after Calving on Cyclicity.
Several research projects have looked at the effects of weight change after calving on the number of cows cycling at the start of the breeding season and pregnancy rates at the end of the breeding season. Wiltbank and others (1983) found that cows in good body condition that lose weight after calving have about a 20 - 30 % lower chance of being ready to breed at the start of the breeding season (Figure 1). They also found that thin cows that gained weight after calving (about 80-100 lbs. from calving until breeding) responded very well with most of the cows cycling by the start of the breeding season.
However, just because cows are cycling doesn't mean they will always breed. Considerable research indicates that cows need to have 2 to 3 cycles after calving before they achieve maximum fertility. There is a 10-20% increase in first service conception rates between the first and third estrus after calving. Another research project demonstrated that feeding thin cows to gain weight after calving increases pregnancy rates by 30% but they still lag behind cows that calved in good body condition (Figure 2; main = cows that maintain weight, gain = cows that gained weight).
Figure 2. Effect of Body Condition at Calving and Pre-breeding Weight Change on Pregnancy Rates in First Calf Heifers.
Feeding Strategies Between Calving and Breeding
The primary nutrient that needs supplementation during this period is energy. Protein may also need to be supplemented, but it should be secondary to energy. The first thing you need to do is test your feeds especially hays and silage for nutrient content. Then compare these tests to the nutritional needs of your cows. Your animal science extension agent or nutritionist can help you with comparing the test results to the needs of your animal.
The source of energy can also be important. Grains such as corn or barley are good sources of energy, but they cause cattle to eat less forage due to a shift in the rumen microbes. If your hay is in short supply this decrease in forage consumption can be a good thing. However, you need to remember that once you supply more than 1/2% of body weight in grain, forage consumption decreases so you need to compensate by feeding a little more grain. Try not to feed more than 1 % of body weight in grain.
Highly digestible fiber feeds like soy hulls or corn gluten will increase the energy level of the diet without decreasing forage intake. This is an advantage because then feed intake is maximized which is important in getting weight on thin cows. These feeds usually have about 85 to 90 % as much energy as corn, so you will need to feed more pounds. Remember energy supplements need to be fed daily.
You should decide from the feed tests if you need to supplement protein. DO NOT over supplement protein. When an animal is fed too much protein it must rid its body of excess protein in the form of ammonia. Excreting ammonia is a process that takes energy. This is why the high protein diets cause you to lose weight if you don't eat a lot of carbohydrates (energy) while on the diet. So if you over feed protein, you will cause cows to lose weight or use the energy you are feeding them to get rid of ammonia rather than gain weight.
The best protein supplements are soy bean or cottonseed meal, corn gluten, poultry litter and others. A reasonably priced mixed feed from the local feed mill is also good. Lick tanks and tubs are expensive sources of proteins, but they are an even more expensive source of energy. Generally, you should avoid lick tanks unless you are feeding corn silage or grazing corn stalks. Protein supplements can be fed every other or every third day. Just double or triple the amount of protein supplement you would normally feed. Remember this only works if you would only be feeding a small amount of protein supplement daily.
If your cows are thin or your feed supply is short, get with your county agent or nutritionist right away to plan your feeding program. Open cows are a costly way to learn a lesson in nutrition.