A prospective study of calf factors affecting age, body size, and body condition score at first calving of holstein dairy heifers.

Data were collected prospectively on parameters related to first calving on 18 farms located in Northeastern Pennsylvania. This project was designed to study possible residual effects of calf management practices and events occurring during the first 16 wk of life on age, BW, skeletal growth, and body condition score at first calving. Multiple imputation method for handling missing data was incorporated in these analyses. This method has the advantage over ad hoc single imputations because the appropriate error structure is maintained. Much similarity was found between the multiple imputation method and a traditional mixed model analysis, except that some estimates from the multiple imputation method seemed more logical in their effects on the parameter measured. Factors related to increased age at first calving were increased difficulty of delivery, antibiotic treatment of sick calves, increased amount of milk or milk replacer fed before weaning, reduced quality of forage fed to weaned calves, maximum humidity, mean daily temperature, and maximum ammonia levels in calf housing areas. Body weight at calving tended to increase with parity of the dam, increased amount of grain fed to calves, increased ammonia levels, and increased mean temperature of the calf housing area. Body condition score at calving tended to be positively influenced by delivery score at first calving, dam parity, and milk or milk replacer dry matter intake. Withers height at calving was positively affected by treatment of animals with antibiotics and increased mean temperature in the calf area. This study demonstrated that nutrition, housing, and management factors that affect health and growth of calves have long-term effects on the animal at least through first calving.

The effects of disease, management, and nutrition on average daily gain of dairy heifers from birth to four months.

The effects of disease, management, and nutrition on the average daily gain of dairy heifers were studied from birth to 4 mo of age for 795 Holstein calves from 21 commercial dairy farms in Pennsylvania during 1991 and 1992. Biweekly visits to the farms yielded information on body weight, nutrient intake, environment, and management practices for each calf. Average daily gain varied throughout the 4-mo period because of many factors, including housing location after separation from the dam, dry matter intake, season, and farm. Dry matter intake was 4.0 kg/kg of body weight gain throughout the period from birth to 4 mo of age. Calves born in winter tended toward higher average daily gain than did calves born in other seasons. Calves born in summer showed a tendency for decreased average daily gain. The practices of tying calves with cows and housing groups of calves in pens were detrimental to average daily gain, but the use of hutches and the practice of tying calves away from cows yielded higher average daily gains. Other variables with significant effects included calving location, parity of the dam, and delivery score at calving.