The Cow-Calf Manager

Livestock Update, December 2001

John B. Hall, Extension Animal Scientist, Beef, VA Tech

Ensuring Future Success of Pregnant Replacement Heifers

Proper pregnant heifer management is essential for the successful transition to a productive cow. By the time a pregnant heifer will calve, a typical beef producer will have between $900 to $1500 dollars invested in her. Pregnant replacement heifers are the highest expense - lowest return animal on the beef farm, as they have generated no income for the operation to this point. Careful systematic management of the pregnant replacement heifer will reap large benefits. Key management areas are:

• Prepartum (precalving) nutrition
• Calving management
• Calving assistance
• Neonatal calf management
• Postpartum nutrition
• Rebreeding

Pre-partum nutrition. Management of the pregnant replacement heifer actually starts at pregnancy examination when heifers should be given a booster vaccination for leptospirosis (Lepto). As soon as they leave the preg. check chute, pregnant heifers need to be treated as a separate group. In smaller operations, the most reasonable option may be to group pregnant heifers with virgin replacement heifers or with young cows pregnant with their second calf.

The objective is to have pregnant heifers reach 90% of their mature weight by calving with a body condition score of 6 or 7. The average heifer in Virginia (1200# mature weight) should weigh 1080 to 1100 lbs. at calving. Heifers need to gain 1.25 to 1.75 lbs. per day between pregnancy diagnosis and 60 days before calving. Most or all of this gain can be achieved with high quality forage including stockpiled fescue, alfalfa-grass hay, silage or high quality pasture. Supplementation in the form of corn, corn gluten, soy hulls or barley may be needed at the rate of 3 to 5 lbs. per heifer per day. A balanced complete high selenium mineral should be fed free choice.

During the last 60 days before calving, heifers will need to gain 2.5 lbs. per day. About 60% of this gain is continued growth and development of the heifer while the remaining 40% of the gain is the rapid growth of the calf and supporting structures (uterus, placenta and fluid). Restricting nutrition during the last 60 days before calving will not reduce calving problems and may increase calf losses (Table 1). In addition to high quality forages, heifers will need to be fed 6 to 10 lbs. or about 1% of their body weight in grain each day. The amount and type of grain will depend on the forage test. Recent research indicates that there may be an advantage to substituting 3 to 4 lbs. of whole cottonseed or whole soybeans for part of the grain. The added fat in these two oilseeds increases calf vigor and reduces the time heifers need to breed back.

Table 1. Impacts of feed restriction in late gestation on first-calf heifers and their calves.

	Nutrition level during last 60 days before calving
Production trait	Restricted	Normal to high
Heifer body weight at calving	< 85 % of mature weight	90% + of mature weight
Heifer body condition score at calving	4 or 5	6 or 7
Days from calving to heifers first cycle	120 +	75 - 110
Calf birth weight	5 - 8 lbs. lower than normal	Up to 5 lbs. heavier
Calving difficulty	Increased	No effect
Calf vigor	Decreased	Increased
Incidence of diarrhea and respiratory infection	Increased	Normal
% live calves at 24 hours	80 %	90 % +
% calves alive at weaning	70 %	85 % +
Pounds of calf weaned per cow calving	Reduced by 50 to 75 lbs.	Normal for herd

Adapted from Corah et al, 1975;

Calving management. Heifers should be bred to calve two to four weeks ahead of the cowherd. The earlier calving date will give heifers more time to recover from calving and begin estrous cycles by the start of the breeding season. An added advantage of calving ahead of the cowherd is more attention can be given to the heifer and her calf. Heifers should calve in a clean, well-drained area that can easily be observed 4 to 6 times a day. A southeast-facing slope that can be seen from the house or road is ideal. Clean pastures are not only free of mud and manure, but they should be areas where cows have not grazed for several months.

Especially clean areas for calving heifers are critical because heifers have lower levels of immunity than mature cows. As a result, they have lower antibody levels in their colostrum. Heifers also produce fewer pounds of colostrum than cows. Therefore, calves from heifers have less disease resistance than calves from cows. Calving heifers ahead of cows decreases the exposure of these calves to disease organisms that cause scours and respiratory disease.

Calving assistance. Approximately 20% to 25% of the beef heifers in the US will require some assistance in delivering their first calf. With proper development and service sire selection, the assistance rate can be reduced to about 10%. In comparison, only 2 to 5 % of mature cows will require assistance. Producers must be prepared to assist heifers with calving.

Producers need to know the signs of labor in cattle. Several good publications and videos are available for a refresher on stages of labor and when to assist. Heifers should be assisted at the first sign of trouble. Research indicates that heifers that are allowed to struggle during delivery have calves that are less vigorous and more susceptible to disease. In addition, heifers that experience dystocia have a 10 to 15% lower rebreeding rate. That's why checking heifers frequently is important.

If heifers are in hard (second stage) labor, they should be checked for problems after 30 minutes to 1 hour without any progress towards delivery. As long as the cervix is well dilated and no malpresentations exist, delivery of the calf can be assisted. Producers should understand how to solve common, simple malpresentations such as a leg back or head turned. A veterinarian should correct more difficult malpresentations. A veterinarian should be called if producers have made no progress towards delivery after assisting heifers for 1/2 hour.

Neonatal calf management. In addition to assisting heifers with delivery, producers may have to help calves during their first hours or day of life. Normal healthy calves should be standing about 1 hour after birth and nursing within 2 hours. Any calf that has not nursed within 4 hours of birth should be assisted with nursing or tube fed warm (101°F) colostrum. Research indicates that the longer after birth a calf takes to nurse the more likely it is to acquire a calfhood illness or die of exposure.

Nursing assistance will require restraint of the heifer in a headgate. A facility with a drop panel to allow positioning of the calf beside the cow is invaluable. Many good commercial calving assistance stalls are available for $1500 to $2500. Only a few calves have to be saved to pay for this piece of equipment.

Some heifers are a little slow to catch on to the idea of motherhood. Placing these heifers and their calf in a clean, well lit maternity stall for 48 to 72 hours will often help the cow and calf "mother-up". By no means should every pair be placed in a maternity stall. This only leads to higher incidence of scours.

Newborn calves need to be monitored for signs of hypothermia. Because of their lower birth weight and decreased colostrum consumption, calves born to first-calf heifers are more susceptible to hypothermia. Signs of hypothermia include lethargy, decreased suckling reflex, and cool limbs and mouth. Calves that are chilled need to be brought inside and warmed slowly in a warm room or calf-warmer. Tube feeding warm colostrum will help in re-warming the calf.

Postpartum nutrition. Although body condition score at calving has a dramatic effect on the percentage of first-calf heifers that rebreed, nutrition after calving will also effect pregnancy rates. First-calf heifers need special nutritional treatment. Remember these heifers are still growing as well as lactating and resuming estrous cycles. After calving, the energy requirement for a lactating first-calf heifer increases by 30% and protein requirement by 40% compared to late gestation. First-calf heifers should be fed separately from the mature cowherd. These "new moms" should get the highest quality forage available. Under most conditions, first-calf heifers will require supplemental feeding of 8 to 12 pounds of a high-energy, moderate-protein supplement. Supplements such as 50% corn-50% corn gluten or 80% corn -20% soybean meal will meet the requirements. A high magnesium complete mineral should be fed free choice as well. Contact your Animal Science Extension Agent or nutritionist for assistance with planning a feeding program.

Rebreeding. If first-calf heifers were in BCS 6 or 7 at calving and have been feed a balanced diet after calving, she should not experience rebreeding problems. However, synchronizing these heifers for breeding, even natural service, will "kick start" a few heifers and reduce the interval from calving to rebreeding. Including a progestin such as MGA or a CIDR as part of the synchronization program will increase rebreeding success. Also, first-calf heifers can benefit from 48-hour calf removal at the beginning of the breeding season.

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