The aim of this study was to investigate the impact of weight gain of calves within the first 3 weeks of life on health status and subsequent performance. Holstein bull calves were reared either intensively (IR; individual hutches and ad libitum milk feeding for the first 3 weeks of life; n = 24), or according to the established protocol [ER; 4 l milk/day in hutches during week 1 and 720 g/day milk replacer (MR) from day 8 to 21 in a group pen; n = 24]. Water, hay and concentrates were freely available to all calves. From week 4, calves of both groups were housed together in a group pen and fed 720 g MR/day; step-down weaning was performed between week 5 and 10. Key metabolic blood parameters were analysed on day 2, 12, 21 and 70 of life. After weaning, all animals were fed concentrates and corn silage until slaughter at an age of 8 months. Within the first 3 weeks, average daily weight gain was threefold higher in IR calves in relation to ER calves (1.28 vs. 0.38 kg/day, p < 0.001). Neither incidence nor duration of scouring differed significantly between groups. Starter intake (week 4-10) was higher in IR calves in relation to ER calves (49.7 vs. 38.0 kg/calf, p = 0.006). Serum glucose, urea, albumin and insulin were higher at an age of 21 days in IR calves in relation to ER calves; no differences were obvious at an age of 70 days. Plasma GH and IGF-I concentrations revealed an uncoupling of the somatotropic axis in ER calves within the first 3 weeks of life. At slaughter, body weight of IR calves tended to be higher than that of the ER calves (320 vs. 309 kg, p = 0.07). In conclusion, intensive feeding and individual housing during the first 3 weeks of life had positive long-term effects on subsequent performance.

Permanent effects of early postnatal nutrition on the development and function of tissues and organs have been previously demonstrated primarily in humans and rodents. The objective of this study in calves was to analyze the impact of rearing conditions during the first 3 wk of life on morphology of insulin-producing pancreatic β-cells. Forty-two male Holstein calves were raised during the first 3 wk of life either intensively (intensively reared [INT]; ad libitum milk feeding and individual hutches; = 21) or according to an established restrictive rearing protocol (4 L milk/d) during wk 1 in hutches and 720 g/d milk replacer (MR) from d 8 to 21 in group pens (restrictively reared [CON]; = 21). Thereafter, all calves were housed and fed under comparable conditions. Birth weight and weekly BW up to wk 10 were recorded. Plasma glucose, insulin, IGF-1, and GH levels were assessed in wk 1, 2, 3, and 10 of life. Slaughtering took place after 8 mo and pancreatic tissue from the medium body (corpus pancreatic) was removed. The number of islets of Langerhans and the insulin stained area were examined histologically. Total milk intake of INT calves was nearly double the intake in CON calves in the first 3 wk of life ( < 0.01). Daily starter intake during wk 4 to 10 of life did not differ between groups ( = 0.24). During the first 3 wk, the ADG were up to 9 times higher in INT calves compared to CON calves ( < 0.01), yet BW at time of slaughter did not differ ( = 0.18). Intensive rearing led to increased plasma glucose, insulin, and IGF-1 concentrations after 3 wk of life compared with rearing to the established standard protocol (all < 0.05), whereas GH was lower in INT calves during the second week of life. At time of slaughter, the mean number of islets of Langerhans was higher in INT calves compared to CON calves (9.1 ± 0.3 vs. 7.8 ± 0.3; < 0.01). Also, the total insulin stained area per photograph was higher in INT calves compared to CON calves (107,180 ± 4,987 vs. 84,249 ± 4,962 μm; < 0.01). Number of islets of Langerhans was negatively associated with birth weight but positively correlated with insulin and in trend with IGF-1 plasma levels during the second week of life. Insulin stained area tended to be linked with IGF-1 concentration during the third week of life. In conclusion, differences in the morphology of pancreatic islets of Langerhans indicate that calves can be programmed metabolically by an altered postnatal rearing intensity.