Breeding the Heifer for Spring Calving Herds
Dr. Tom Troxel
Due to the high price of cattle and the excellent growing condition, many cattle producers retained extra heifers to rebuild or to replace older cows in their herd. Raising high quality replacement heifers is an essential and major investment for the cow-calf producer. The replacement heifer becomes the genetic building block for the cow herd. With proper management a replacement heifer will become a fertile cow that produces a calf, annually, for a long time.
Many management steps and decisions must be made in the process of selecting and growing replacement heifers. Consequently, replacement heifers must pass a number of “production tests” to remain in the herd and, hopefully, become a member of the cow herd. Selection at weaning, development from weaning to first breeding, evaluation after first breeding and calving season and establishment of successful rebreeding are the “production tests” a heifer must pass. Heifers not meeting production targets should be culled at any point in the process.
Management from Breeding to Calving
For spring calving herds, this is the time of year to begin planning the breeding season for replacement heifers. Replacement heifers should be on a good health program. Contact your veterinarian to develop the right vaccination program for your replacement heifers.
Calving difficulty is of great concern with first-calf heifers, as it is the primary cause of calf losses at birth. The major causes of dystocia are an oversized calf or an undersized heifer. A large calf and/or a heifer with a small birth canal can cause calving problems. The general rule of thumb is that a female (heifer or cow) should be able to calve 8% of their body weight. Therefore, if a heifer weighs 900 lbs. at calving, she should be able to deliver a calf weighing 72 lbs. at birth. Two methods can be used to reduce the risk of calving difficulty. The first is to be sure the pregnant heifer is properly “grown-out” from breeding to calving. Pelvic area of heifers can be measured at yearling age, and those with small areas should be culled.
Another method of reducing dystocia is by reducing birth weights. Select low birth weight or high calving ease EPD bulls for breeding heifers. Birth weight information on a bull and his sire can be effective in reducing birth weights as well. Be very careful in selecting bulls if no prior calving information is known. Many yearling bulls are used on heifers satisfactorily, but the old belief that a young bull will sire smaller calves is not true. To reduce the risk of injury, however, smaller bulls should be used. Bulls should not weigh more than 170% to 180% of the heifer’s body weight. If heifers weigh 800 lbs. at the start of the breeding season, the bull selected to breed those heifers should not weigh more than 1,400 lbs.
It is recommended to breed replacement heifers 20 to 30 days before the cow herd. This permits more time and labor to be given to heifers during the calving season. Heifers can be watched more closely and assisted if necessary to reduce calf death losses. It also allows for a longer period from calving to rebreeding, which is needed by first-calf heifers to regain body condition and initiate estrous cycles.
The breeding season for replacement heifers should be approximately 45 days. Heifers should be checked for pregnancy 60 to 90 days after the end of the breeding season, and all open heifers should be culled. This increases selection pressure for high fertility and also ensures a short first-calving season.
Heifers need to gain 0.8 to 1.0 lb. per day from the time they are bred until calving. This can usually be achieved on pasture and mineral supplementation alone. At calving, heifers should weigh 85% of their expected mature body weight and be in good body condition (BCS = 6 to 7). If heifers are in thin body condition, they should be placed on a higher level of nutrition. It is difficult to improve heifer body condition as calving approaches, and it is especially difficult after calving. Improving condition will improve colostrum production and quality, will decrease post-calving anestrous period and increase the livability of their calves.
“Starving” heifers prior to calving does not reduce calving problems. Underfeeding can cause poor milk production, reduced weaning weights, lower rebreeding rates and increased calving difficulties. It also is not desirable for heifers to be over conditioned. Heifers which are over conditioned at calving have greater calf losses, excessive feed cost, depressed milk production, decreased life span and rebreeding difficulties.
Genetically speaking the replacement heifer should be the best animal on the farm and, therefore, is the genetic building block for the future. Taking extra management steps such as selecting a low birth weight bull, breeding heifers 20 to 30 days before the cow herd, managing heifers so they continue to gain 0.8 to 1.0 lb. per day until calving, and maintain good body good body condition (BCS = 6 to 7) will allow the heifer to perform at her genetic potential.