Factors associated with body weight of young surplus dairy calves on arrival to a calf rearing facility.

The objective of this study was to identify factors present on the source dairy farm and during transport, that are associated with low body weight of young dairy calves at arrival to a calf rearing facility. A total of 195 surplus dairy calves from five farms in southern Ontario, Canada were examined from October 2020 to June 2021. Calves were continuously enrolled at birth on participating source dairy farms for three weeks until the day of transport and followed until arrival at the calf rearing facility. Calf sex, breed, calving difficulty, and birth weight were recorded at enrollment and blood samples were collected between 24 and 48 h after birth to determine serum total protein. From the day of birth through arrival at the calf rearing facility, each calf received a daily health examination which included a fecal consistency score, respiratory score, and navel score. On the day of transport, calves were randomly assigned to 1 of 3 transport treatments: 6 h, 12 h, or 16 h of continuous transportation by road. Age on the day of transport was recorded, and body weight was measured immediately before and after transportation. Two mixed linear regression models were built to determine the effect of these variables on body weight at arrival. The mean (± SD) birth weight, body weight before transport and body weight at arrival were 45 kg (± 6.9), 51 kg (± 6.6), and 47 kg (± 5.9), respectively, and age on the day of transport ranged from 1 to 22 d. Breed, birth weight, age at transport, body weight immediately before transport, and transport duration were associated with body weight at arrival. Holstein calves had greater body weights at arrival compared to Holstein-beef calves. Additionally, calves with greater birth weights and greater body weights immediately before transport had greater body weights at arrival. Calves over 5 d of age at transport had greater body weights at arrival compared to calves transported at 5 d of age or less. Calves transported for 6 h had a greater body weight at arrival compared to 12 h or 16 h, and those transported for 12 h had a greater body weight at arrival compared to 16 h. Future studies should evaluate approaches and policies to increase body weight of surplus dairy calves at arrival as it is consistently associated with improved health and productivity at calf rearing facilities.

The effect of Cryptosporidiumparvum, rotavirus, and coronavirus infection on the health and performance of male dairy calves.

The objective of this prospective cohort study was to investigate the effect of bovine coronavirus (BCoV), bovine rotavirus (BRoV), and Cryptosporidiumparvum on dairy calf health and performance and to determine the prevalence of these pathogens. A total of 198 male dairy calves housed at a grain-fed veal facility were examined from June 11, 2018, to October 9, 2018. Calves were fed milk replacer twice daily and housed individually until weaning at 56 d. Once weaned, calves were moved into groups of 5 until they were moved to a finishing facility at 77 d. At the grain-fed veal facility, calves were scored for fecal consistency for the first 28 d and had fecal samples taken on arrival and at 7 and 14 d. Fecal samples were frozen and submitted to a commercial laboratory, where they were tested for BCoV, C.parvum, and 2 groups of BRoV: group A (BRoV A) and group B (BRoV B). Calves were weighed on arrival and at 14, 49, 56, and 77 d using a digital body scale. Treatments for disease and mortalities that occurred over the 77 d were also recorded. Statistical models, including Cox proportional hazards and repeated measures models, were built to determine the effect of infection with 1 of the pathogens. Over the 3 sampling points, 151 (85.8%), 178 (94.2%), 3 (1.5%), and 97 (57.4%) calves tested positive at least once for BCoV, BRoV A, BRoV B, and C.parvum, respectively. The source of the calves and the level of serum total protein measured on arrival were associated with testing positive for a pathogen. Calves that tested positive for C.parvum had an increased proportion of days with diarrhea and severe diarrhea; calves that tested positive for BCoV and BRoV A had an increased proportion of days with severe diarrhea. In addition, calves that tested positive for C.parvum had a higher hazard of being treated for respiratory disease. With respect to body weight, calves that had diarrhea or severe diarrhea had lower body weight at 49, 56, and 77 d. Specifically, calves that had an increased proportion of days with diarrhea showed a reduction in weight gain of up to 15 kg compared to calves without diarrhea. Calves that tested positive for C.parvum had a lower body weight at 49, 56, and 77 d; calves that tested positive for BCoV had a lower body weight at 56 and 77 d. This study demonstrates that the prevalence of BCoV, BRoV A, and C.parvum infection is high in this population of calves and has significant effects on the occurrence of diarrhea and body weight gain. Future studies should evaluate approaches for minimizing the effect of infection with these pathogens to improve the welfare, health, and productivity of dairy calves.