Effects of human visitation on calf growth and performance of calves fed different milk replacer feeding levels

Twenty-eight newborn Holstein heifer calves from the university herd and 8 newborn Holstein heifer calves from a commercial herd were blocked by birth and herd into 1 of 4 treatments: conventional [20% crude protein (CP), 20% fat] milk replacer (MR; treatment C) with (1) or without (0) human visitation, or a higher plane of MR nutrition (28% CP, 20% fat) regimen (treatment A) with (1) or (0) without human visitation. Calves on C MR treatments received 454 g of MR from d 2 to 41. Calves on A MR received 916 g of MR from d 2 to 8 and 1134 g of MR from d 9 to 41. Visitation with calves occurred at 1030 and 1430 h daily from d 1 to 56 and comprised verbal stimulation and stirring of starter grain. An opaque curtain divided the calf nursery, with calves in the front half assigned to visitation treatments and those in the rear half not assigned to visitation treatments. Calves were fed their MR treatment until d 43 (preweaning), after which all calves received half of their allotment of MR until d 49 (weaning). Calves were tracked for the next week until d 56 (postweaning). Starter grain and MR intakes were measured daily along with weekly body weight and skeletal measurements. One half of the calves on each treatment had blood samples taken via jugular venipuncture on d 41 (preweaning), 43, 45, 47, 49, and 51 (postweaning) to evaluate blood glucose, urea, nonesterified fatty acids, and cortisol concentrations. During the preweaning and weaning phases, calves on A0 and A1 treatments consumed more MR, less starter, and weighed more than the C0 and C1 calves. Calves on A0 and A1 had greater average daily gain (ADG), hip and withers gain, were taller at the hip, and had larger girths during the preweaning phase. Overall, body weight, withers and hip heights, and heart girths were greater in A0 andA1 calves during the weaning week. Efficiency of utilization of estimated metabolizable energy (ME) intake (ADG/ME) were similar. Glucose and nonesterified fatty acids concentrations were greater in visited calves preweaning. An interaction for glucose was observed during weaning, with A1 calves having the highest concentration and A0 calves having the lowest concentrations during weaning. Cortisol tended to be higher in visited calves during weaning. Postweaning, calves formerly fed A0 and A1 treatments had lower blood glucose and tended to have higher urea and cortisol concentrations than C0 and C1 treatments. The higher plane of nutrition fed calves tended to have higher cortisol concentrations indicating that they experienced more stress due to the removal of MR more than calves fed conventionally. Calves fed the higher plane of MR nutrition consumed more dry matter, ME, and water weighed more, had a greater ADG, and were taller than calves fed the conventional MR. These calves were more efficient (ADG/dry matter intake) when expressed on a dry matter basis, but had similar efficiency when expressed on an ME basis (ADG/ME). Visiting calves did little to reduce the stress of weaning when calves are fed the higher plane of nutrition MR feeding regimen.