Delaying postpartum separation by 3, 5, or 7 days compared with immediate separation: A pilot study on production and...

Our objectives were to describe the effects of full cow-calf contact for 3, 5, or 7 d after calving compared with immediate separation on milk yield and components, cow metabolic indicators, milking characteristics, and IMI status, as well as on calf outcomes transfer of passive immunity (TPI), milk intake, and health scores. Holstein cows with a singleton calf were eligible for enrollment, and 23 Holstein cows (8 primiparous, 15 multiparous) and their calves were included in a randomized block design. Cows were housed in identical box stalls regardless of treatment assignment and milked twice daily from parturition to d 8. In pairs assigned to the 0D group, calves were separated immediately after birth, whereas in the 3D, 5D, and 7D treatment groups, calves were separated 3, 5, or 7 d after birth, respectively. All calves were fed colostrum at 8.5% of birth body weight (BBW). Contact calves had access to the cow's box stall except during milking, when they were confined to a connected calf creep area. Separated calves were fed whole milk twice daily, up to a total of 25% of BBW per day, and housed in identical pens in a different section of the same barn. Milk yield was measured at each milking, and milk components were determined on d 0, 1, 3, 5, and 7. Quarter-level milk was taken for microbial cultures on d 0 and 8. Vacuum dynamics were measured daily using a portable vacuum recorder to detect bimodal milk flow curves. Serum samples of cows and calves were analyzed for metabolic markers and IgG concentration, respectively. Calf health was scored daily, and hip and withers heights were measured. The most common reason for exclusion was low colostrum production of the dam. Milk production was lower during the respective contact periods in the 3D, 5D, and 7D groups, but rebounded to the level of the 0D group after separation, respectively. Lactose concentration was lower in the 5D group compared with 0D. Bimodality was only found in milking observations of the contact groups but not in the 0D group. Quarter-level new IMI or risk of cure, as well as metabolic indicators did not differ between groups. Successful TPI was shown in all groups, and calf health and growth indicators did not differ between groups. Median milk intake in the separated calves ranged from 9 to 9.8 kg on d 7. In summary, Holstein cows with delayed separation of their calves showed a transient reduction in milk yield, occurrence of bimodality, and lower milk lactose concentration, whereas metabolic indicators and IMI risk did not differ. Calves showed no difference in health scores or growth, and separated calves voluntarily consumed a median daily amount of milk equal to 18% to 20% of BBW. Delayed separation of calves from their dams was associated with differences in milk production, bimodality and milk components, whereas under controlled colostrum feeding conditions, calves showed no difference in TPI, health outcomes, or injury risk. Long-term effects on milk production, bimodality, calf growth, and health merit further investigation.