HIGH QUALITY PASTURAGE FOR DAIRY COWS: DEPRESSED MILK FAT PERCENTAGE, FORAGE INTAKE AND SUPPLEMENTATION (SODIUM-BICARBONATE, COMPOSITION

Three trials were conducted to evaluate the performance of lactating dairy cows when moved to pasturage in spring.;The first trial was to evaluate the effect of 1.9% sodium bicarbonate addition to concentrate fed at a rate of 1 kg/3 kg 4% fat corrected milk when cows grazed high quality pasture. Milk fat percentage decreased when cows fed in dry lot were moved to graze high quality pasture. There was no difference in concentrate intake, milk yield, 4% fat corrected milk, fat percentage, protein percentage, or body weight change between cows with and without sodium bicarbonate in their diets.;The second trial was to evaluate the effect of 1 kg of chopped or long hay supplementation to the diet of cows grazing the same kind of grass-legume pasture. Cows on long hay supplement produced 1 kg more milk/cow daily but with a lower fat content, than cows in the control group. There were no differences in protein percentage, fat yield, 4% fat corrected milk or body weight change among treatments.;The third trial was to evaluate the effects of moving cows from winter feeding to pasture at two stages of plant maturity and of supplementing with 4 kg long hay daily. Concentrate intake was higher for cows starting grazing on more mature pasture but was not different between cows with and without hay supplement. Hay was 2.7 kg dry matter per cow daily. Milk yield and protein percentage increased and fat percentage decreased when cows were moved to immature pasture. No differences in milk yield and milk composition were observed when cows grazing young immature pasture received 4 kg of long hay supplement per day, as compared with control animals. Milk yield was lower in cows starting grazing on more mature pasture, as compared with control animals. Long chain fatty acids in milk fat increased and short chains decreased when cows moved to pasture, but there were no differences due to treatment. Plasma concentration of triglycerides, glucose and oleic and linolenic acids in plasma lipids all increased when cows were moved to pasture, but linoleic acid decreased. Plasma stearic and linoleic acids were higher and oleic acid lower in cows with hay supplement than in control cows. Body weight gain was less in cows starting grazing on more mature pasture than in those grazing immature pasture.