摘要：The National Dairy Heifer Evaluation Project ( NDHEP ) was conducted by the National Animal Health Monitoring System (NAHMS ) from April 1991 through July 1992 with the assistance of 1,811 producers from 28 states. Producers included in the study each had herds of 30 or more milk cows, representing 78 percent of the milk cows in the U.S. The average total of cattle and calves on each operation was 169.4. The main breed on 94.9% of operations was Holstein. Slightly over 46 percent of operations stated reproductive problems as the cause of low milk production of cows culled from the herd. Newborn calves were separated from their mothers before nursing on 28.0 percent of operations and less than 12 hours after birth on 39.6 percent of operations. On 64.0 percent of operations, calves received their first feeding of colostrum via hand feeding from a bucket or bottle. Of operations using hand feeding, 94.6% fed first milk from the mother (as opposed to other colostrum or substitute) to calves. Calves received, on average, between two and four quarts of colostrum during the first 24 hours. A variety of liquid feeds were used after colostrum was fed; the two most widely utilized were milk replacer ( 59.0 percent of operations ) and milk from cows recently calved ( 51.9 percent of operations ). Calves were weaned from liquid ration at an average age of 7.9 weeks. The average age of heifers at first calving was 25.9 months. The most common illness among dairy heifer calves was scours (53.8 percent of operations ), with respiratory problems as the second most common illness (12.1 percent of operations ). Scours was estimated to cause 52.2 percent of deaths ( 4.4 percent of calves born ) among dairy heifer calves from birth to weaning; respiratory problems were estimated to cause 34.8 percent of deaths ( 0.8 percent of heifer inventory ) among heifers from weaning age to first calving. Contact for this paper: Stephen Ott
