The Cow-Calf Manager
Livestock Update, September 2004
John B. Hall, Extension Animal Scientist, Beef, Virginia Tech
Calves are looking good around Virginia and the Mid-Atlantic, and the grass held up well during August. With high calf prices, beef producers should be able to make a reasonable profit this year. In cow/calf operations, profitability is directly linked to percentage of calves weaned per cow exposed. Management emphasis should focus on practices that increased the number of pregnant cows and calves born alive. In the average cow/calf outfit, most improvement can be made in the percentage of cows that become pregnant especially young (2 & 3 year old) cows. This month begins a series on reproductive management.
Weaning time - a chance for analysis of herd reproduction
Weaning is an excellent time to collect and analyze some important information for assessing herd reproductive efficiency. Important pieces of information are:
These pieces of information are easy to obtain, but they need to be examined and used to review. The only thing producers can't collect by themselves is the pregnancy data on cows. Producers should not skip hiring a veterinarian to pregnancy check cows. Knowing which cows became pregnant and when they are due to calve is important to making management decisions. In addition, preg check time is a good opportunity to visit with the veterinarian about your herd health management plan, changes in vaccines and other health products, cows with chronic conditions, and cow culling.
Number and percentage of calves weaned gives producers an indicator of the herds past reproductive performance and indicates places for improvement or monitoring. To calculate the percentage of calves weaned, the number of calves weaned should be divided by the number of cows in the herd at the beginning of the breeding season about 18 months ago. Percentage of calves weaned will give producers information on overall reproductive status of the herd. Good herds will average a weaning percentage of 83-89% of all cows that were present at the time of breeding. Better herds will average 90-95%. Remember this is a percentage of all cows present 18 months before.
Herds with a low percentage of calves weaned (< 83%) indicate problems in one of three areas. First (and most often), it may be a function of too many open cows. This would indicate a general fertility problem with either the bull or cows. The cause of infertility may be nutritional, physiological, genetic, or disease based. Second, it could be the result of too many calves dying within 24 hours of birth. High calf losses at calving time are usually caused by dystocia (calving difficulty), weather conditions, or lack of assistance at birth. Finally, high calf losses between birth and weaning indicate a non-reproductive problem. Usually, these losses result from disease problems such as scours or pneumonia. Occasionally, they are a result of predation.
Average age at weaning and distribution at weaning is an indicator of the "tightness" of the calving season. Tighter calving seasons increase calf uniformity and calf weight. Calves should average 7 to 8 months at weaning for spring calvers and about 9.5 months at weaning for fall calvers. Ideally, all calves should be born in a 75 to 90 day period for commercial herds. The ideal calving distribution is illustrated in Figure 1. For every 21 days later a calf is born in the calving season (21 days younger at weaning), it will be 35 to 40 lbs lighter at weaning.
Figure 1. Normal and ideal calving distributions for commercial beef herds.
A long calving season or poor distribution of calves is an indicator of too few cows cycling at the beginning of the breeding season. Most often lack of cyclicity is caused by low body condition at calving and/or poor nutrition after calving.
Average and range of weaning weights of calves are an indicator of cow milking ability and genetic ability for growth. The range in weaning weight is an indicator of uniformity of performance of the cowherd as well as a function of calving distribution. Although not technically reproductive measures, weaning weights combined with body condition scores of cows at weaning can be used to assess if the forage/nutrition program and cow milking ability is matched. Thin cows with large calves would indicate the needs of high milking cows were not being met. Conversely, fat cows with small calves indicate that feed supplies are in excess of cow milking ability.
Percentage of pregnant cows at pregnancy exam is an indicator of current reproductive efficiency. Good herds should average 88 to 90 % pregnancy rates with extremely good herds averaging 92 to 95 %. Remember this is based on the number of cows that started the breeding season. From pregnancy exam until calving, about ®– to 2 % of the pregnancies end in spontaneous abortion. So one or two cows not calving that were diagnosed pregnant is not unusual. Open cows are primarily a result of nutritional problems, but bull failure and disease can account for open cows as well. Too many open cows are cause for concern and the source of the problems should be identified and corrected before next breeding season.
There are management advantages to pregnancy diagnosis. First, veterinarians can fetal age calves so cows can be grouped by calving date near calving time. This allows for better care and observation of pregnant cows and newborn calves. Secondly, open cows can be identified and eliminated from the herd. Timely marketing of open cows can greatly impact an operation's profitability. Open cows should be managed to be sold as fleshy cows during peak cull cow market times of December, January, or July.
Body condition scoring cows at weaning allows producers to sort cows into management groups for feeding. Cows need to be in BCS 5 to 6 by calving time. Thin cows (< BCS 4) and young cows should be sorted into a separate group from mature cows in good condition. The "thin/young" group should be fed to gain weight by calving time while cows in good condition should be managed to maintain condition.
Immediately after weaning is the best time to put body condition on cows. The cow's nutrient requirements are low and weather is favorable for putting on weight. Fall calving herds can graze hay fields or use rotational grazing to improve forage availability for cows. Spring calving herds should be using stockpiled fescue to put weight on dry pregnant cows.
Reproductive management is the key to a successful cow/calf operation. Analysis of where an operations program is at weaning gives producers enough time to make changes or improvements before the next calving and breeding seasons.