RELATIONSHIPS BETWEEN SUBCLINICAL KETOSIS, MILK-PRODUCTION AND FERTILITY IN FINNISH DAIRY-CATTLE

The relationships between milk production, subclinical ketosis and fertility were studied in 101 dairy cows in central Finland. For determination of milk components, individual milk samples were obtained in three successive, monthly milk recordings. The metabolic balance of the cows was determined by acetone and urea assays of milk. In addition, at dry-off a milk sample was obtained and the body condition score was determined. At 3-4 weeks postpartum (p.p.), low acetone concentrations in milk were associated with high milk yield and with high yield of milk protein at 3-4 and 7-8 weeks, whereas there was only a slight negative correlation between yield of milk fat and acetone concentration. At 7-8 weeks p.p., high levels of acetone were correlated with a high percentage of milk fat and with a low percentage of milk protein in the third milk recording. At 3-4 weeks p.p. a high percentage of milk fat and a low protein: fat ratio were correlated with high acetone at 7-8 weeks. High acetone level at Test 2 was correlated with high milk yield at Test 3. At dry-off, high levels of urea were associated with a low percentage of milk protein at the first and second milk recording of the next lactation. Cows with fat body condition had a high percentage of milk fat and a low protein: fat ratio. The yield of milk protein and of milk at 3-4 weeks p.p. affected the interval from calving to conception (r=0.31). The time from calving to conception also was associated with high protein yield, high milk yield and high fat yield at 7-8 weeks p.p. (r=0.41, r=0.40 and r=0.35, respectively). At the third milk recording, a low percentage of milk protein was associated with a long interval from calving to first insemination and to conception (r=0.22 and r=0.26, respectively). We conclude that subclinical bovine ketosis in early lactation reduces milk production. Subclinically ketotic cows might not achieve the maximum potential milk yield. In an individual cow, high milk production as a result of the low energy balance in puerperium curtails reproductive performance. At dry-off, overfeeding is associated with a low protein: fat ratio early in the next lactation.