Effects of genotype and concentrate supplementation on milk composition and selected milk processability parameters in late-lactation spring-calving grazing dairy cows

A 2 × 2 factorial design experiment was conducted to investigate effects of cow genotype and concentrate supplementation (CS) on milk composition and processability. Four treatment groups (n = 12) were: (i) lower milk genotype (LM) offered no CS; (ii) LM + 2.7 kg dry matter (DM) CS; (iii) higher milk genotype (HM) offered no CS; and (iv) HM + 2.7 kg DM CS. Cows were +208 d in milk, grazed full time, and were offered 17 kg DM pasture cow-1 d-1. Increased milk yield resulted from HM cows and offering CS. The HM cows had decreased fat, protein and casein concentrations, while offering CS also decreased fat, protein and casein concentrations. Milk from cows offered CS had increased ethanol stability compared with cows offered pasture-only. In conclusion, HM cows and offering CS increased milk yield at the expense of components, but offering CS increased milk colloidal stability.