Calf foetal and early life nutrition on grazing conditions: metabolic and endocrine profiles and body composition during the growing phase.

The aim of this study was to determine the effect of nutrition during foetal and lactation periods on calf growth and body composition, and their association with changes in metabolic and endocrine profiles during the calf first year of life on purebred (Hereford and Angus) and cross-bred (F1) dam offspring. Forty cross-bred calves and their dams (purebred--PU: Hereford and Angus, and cross-bred--CR: F1) were used in a randomized block design with a factorial arrangement of herbage allowance of native pastures (high: Hi-HA and low: Lo-HA), 4 vs. 2.5 kg dry matter/kg body weight (BW) and dam genotype (PU vs. CR). Calf BW and blood samples were collected monthly from birth to 380±15 days of age, and body composition was estimated by the urea dilution technique at weaning (142±15 days) and 380 days. Calf birthweight did not differ among groups but from birth to 380 days, and BW was reduced (p=0.046) in Lo-PU offspring. Although Lo-CR calves achieved similar BW than Hi-PU and Hi-CR offspring, they showed an increased fat in detriment of lean tissue deposition. At birth, plasma total protein was less (p=0.04), while plasma glucose, insulin or IGF-I tended or were greater (p<0.072) in Hi-HA than Lo-HA calves. Greater (p<0.03) plasma total protein and/or glucose concentrations during the first months of lactation were observed in CR offspring associated with the greater dam milk production. Although glucose concentrations did not differ among calf groups after weaning, plasma insulin was greater (p=0.004) in Hi-PU than other groups at 380 days. Consistent with the reduced BW, Lo-PU offspring presented the lowest (p=0.026) plasma IGF-I from birth to 380 days. Herbage allowance of native grasslands during calf foetal and lactation periods interacted with maternal heterosis to affect, in the short and/or long term, calf BW or body composition, and metabolic and endocrine profiles.