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.