Beef Reproduction^^
AS-405 Feb. 1973
Reducing Calving Difficulty in Beef Cattle
W. L. Singleton and L.
Calf deaths at or near birth represent a major economic loss for farmers. Six to 10% of all calves die at or soon after birth. About half of these losses are due to "dystocia" or difficult birth. Dystocia is three times as costly to the cattleman as abortions and is second only to losses from cows failing to conceive.
In recent years, increased attention has been given to calving difficulty. One reason is the mating of larger breeds of bulls to British breeds of cows (Angus, Hereford and Shorthorn). Another reason is the increased calving problems experienced within purebred herds when genetically large bulls, selected for large mature weights, have been mated to small or average-sized cows.
Because of its economic importance, cattle producers need to understand the causes of calving difficulty and take steps to reduce or eliminate them.
DYSTOCIA AND CALF LOSSES
About 80% of all calves lost at birth are anatomically normal. Most of them die because of injuries resulting from difficult or delayed parturition (calving). Factors contributing to dystocia fall into three main categories: calf effects, dam effects and fetal position.
Calf Effects
Birth weight accounts for most of the problems related to the calf and is influenced by the following:
A. Nelson, Animal Sciences Department
Breed of sire. Large bulls with extremely massive shoulders and heavy muscling sire heavier calves with larger shoulders and thick muscling, thus causing calving problems. Mating these bulls to heifers and small cows is not recommended. Some breeds of bulls sire heavier calves than others. Select a breed with average or below average birth weights for breeding to heifers.
Bull within a breed. Heavier calves result from some lines within breeds. If possible, don’t select a bull for heifers from these lines.
Sex of calf. More calving problems and death losses are associated with bull calves because they average 3-5 pounds heavier than heifers at birth.
Age of dam. Calves from cows 5 or more years of age are generally heavier at birth than calves from younger cows.
Length of gestation. Much of the fetal growth occurs during the last month of pregnancy; therefore, the longer the gestation period, the heavier the calf. Bull calves are carried about 1-1/2 to 2 days longer than heifers. Other factors, such as breed, nutrition and weather, also influence gestation length.
Nutrition of dam. Cows receiving more than the recommended 9 pounds of total digestible nutrients (TDN) daily prior to calving will have heavier calves than cows fed the recommended level. But equally important, don’t underfeed heifers and cows. Adequate nutrition is essential to insure that calves will be vigorous at birth and that cows will
Cooperative Extension Service, PURDUE UNIVERSITY, West Lafayette, Indiana