Plane of nutrition affects growth rate, organ size and skeletal muscle satellite cell activity in newborn calves

Plane of nutrition effects on body, tissue and cellular growth in the neonatal calf are poorly understood. The hypothesis that a low plane of nutrition (LPN) would limit skeletal muscle size by reducing fibre growth and muscle progenitor cell activity was tested. At birth, calves were randomly assigned to either a LPN (20% CP, 20% fat; GE=1.9 Mcal/days) or a high plane of nutrition (HPN; 27% CP, 10% fat, GE = 3.8 Mcal/days) in a 2x3 factorial design to test the impact of diet on neonatal calf growth, organ weight and skeletal muscle morphometry with time. Groups of calves (n=4 or 5) were euthanised at 2, 4 and 8week of age and organ and empty carcass weights were recorded. Body composition was measured by DXA. Longissimus muscle (LM) fibre cross-sectional area (CSA), fibre/mm(2) and Pax7 were measured by immunohistology. Satellite cells were isolated at each time point and proliferation rates were measured by EdU incorporation. Calves fed a HPN had greater (p<0.05) BW, ADG and hip height than those fed a LPN for 2, 4 or 8weeks. HPN calves contained a greater (p<0.05) percentage of fat tissue than LPN calves. Liver, spleen and thymus weights were less (p<0.05) in LPN calves than HPN animals. Calves fed HPN had larger (p<0.05) LM CSA at 8weeks than LPN fed animals with no differences between the groups in numbers of satellite cells per fibre. Proliferation rates of satellite cells isolated from HPN fed calves were greater (p<0.05) at 2weeks than LPN fed animals, which exhibited greater (p<0.05) proliferation rates at 4weeks than HPN fed calves. We conclude a LPN diet reduces body growth and organ size and metabolically reprograms satellite cell activity.