Abstract:
Eight Friesian cows in early lactation and eight in late lactation were used in crossover experiments to measure the effects of allowing drinking water for 24 hours a day or for 20 minutes before each milking. Experiments were done during summer in the tropical upland environment of the Atherton Tablelands, Queensland. Free water intakes averaged 78 and 60 kg cow-1 day-1, and milk yields 13.8 and 8.9 kg cow-1 day-1 for cows in early and late lactation respectively. Cows with restricted access to water drank 84 per cent of the water intake of cows with unrestricted access to water. Maximum water intake at one drink averaged 67 kg cow-1 for cows with restricted access to water. Water intake was positively related to maximum air temperature and hours of sunshine a day (P < 0.05), and negatively related to rainfall and relative humidity (P < 0.05). Milk yield, composition and freezing point were unaffected by system of water supply. Grazing time from morning to afternoon milking was similar for cows on both treatments, though the pattern of grazing was changed. There was some evidence that milk yield of cows was depressed during the two days immediately after removal of paddock water. In two investigations there was no loss in milk production when drinking water was removed from the paddock for the one inter-milking interval, morning to afternoon milking.