Sixteen Holstein-Friesian animals, comprising 8 multiparous cows and 8 first-lactation heifers, were divided into 2 equal groups which had access to either tree shade or no shade. All animals were in the first third of lactation and were subjected to treatment for 8 weeks in summer 1985. Average maximum monthly temperatures ranged from 26.2 to 28.22� over the experimental period. The provision of shade increased (P< 0.01) milk yield; however, there was a significant (P<0.05) interaction between response to shade and cow parity. Mean daily milk yields for multiparous cows were 19.2 and 17.2 kg/cow (P< 0.01) and 16.3 and 15.9 kg/cow (P> 0.05) for heifers in the shade and no shade groups respectively. Cows without shade incurred a significant decrease (P< 0.05) in solids-not fat yield, lactose percentage and lactose yield, and a significant increase ( P < 0.05) in somatic cell count. The composition of milk from heifers without shade was no different from that from heifers with shade. Rectal temperature was higher (P < 0.01) in animals without shade (mean 40.0�C) than in animals with shade (mean 39.4�C). The highest mean maximum rectal temperature of 41.6�C was recorded in the noshade group. It was concluded that shade is essential if milk yield and milk composition are to be maximised in this environment.

A group of 40 Holstein-Fresian cows grazing tropical pastures were supplemented from 14 days after calving with a grain-based concentrate containing 15% protein. Concentrate was given at nil, 2, 4, 6, and 8 kg/cow. day fed once daily after morning milking, and 4, 6, and 8 kg/cow.day in 2 equal feeds, after morning milking and before evening milking. The experimental period was 250 days for cows fed once daily and 150 days for those fed twice daily. Over 250 days of lactation, the milk yield of cows fed once daily was significantly increased with increasing grain feeding, from 12.8 kg/day for the nil group t o 20 kg/day for the 8 kg group. Milkfat percentage was lower (P<0.05) for cows given 8 kg grain concentrate daily than for those given 2-4 kg, and total fat yield increased (P<0.1) with up to 4kg/cow.day. Protein percentages were similar across treatments, and protein yield increased (P<0.05) with grain level. Lactose percentage was increased (P<0.05) with concentrate feeding, and lactose yield increased (P<0.05) with increasing concentrate level. Fat-corrected milk (FCM) increased (P<0.05) from 3046 kg at nil concentrate to 4465 kg at 8 kg/cow. day. Over the first 150 days of lactation, milk yield increased from 19.5 kg/day for cows fed once daily to 21.7kg/day for those fed twice daily. Milkfat and protein percentages were similar. Greatest responses to twice-daily feeding occurred at 6 kg concentrate/cow.day. It was concluded that total milk yield increased linearly to 8 kg concentrate/cow.day, but FCM yield was at a maximum at 6 kg concentrate1cow.day. There were advantages in feeding 6 kg concentrate twice daily.

The phosphorus fertilizer requirements and long term productivity of nitrogen-fertilized Gatton panic (Panicum maximum cv. Gatton) pastures, grazed by lactating dairy cows, were evaluated over 7 years. Cows grazed at 2n6 cows\ha on pastures that received annually 100 or 300 kg N\ha at each of 0, 22n5 or 45 kg P\ha. Phosphorus treatments were applied as single superphosphate, balanced for calcium by applications of gypsum.The soil had an initial available soil phosphorus content of 40 mg\kg (bicarbonate extraction). At zero P fertilizer (0P), extractable soil P declined at the rate of 1n9 mg\kg each year ; at 22n5P it was maintained close to the original level while at 45P it increased at 6n6 mg\kg each year. Increased P fertilizer caused significant (P 0n01) increases in plant P concentration from year 2 onwards. In years 6 and 7 there was significantly less green pasture and leaf on offer in 300N pastures at 0P than with 22n5P and 45P. There was no influence of rate of P fertilizer at 100N on pasture quantity on offer in any year. There were clear trends at 100N of decreasing total pasture and green dry matter (DM) on offer over the 7 years, but not at 300N.Cows at 300N consumed more leaf in the diet in autumn and winter than at 100N. Leaf was 55-60 % of the diet in summer and autumn, but decreased to 21 % (100N) and 37 % (300N) in winter. Dead material in the diet was always higher at 100N. Pasture leaf percentage and leaf yield were the best individual predictors of leaf percentage in the diet. Diet P selected from pasture was reduced by the higher rate of N fertilizer in each season. Estimated P concentrations of the diet selected from pasture for summer, autumn and winter averaged 0n30, 0n38 and 0n28 % DM for 100N and 0n19, 0n24 and 0n18 % DM for 300N treatments, respectively.The response to P fertilizer was dependent on the rate of N fertilizer applied. The critical bicarbonate extractable soil P level for this soil type, below which pasture responses occurred, was 30 mg\kg at 300N. The critical level at 100N was not reached, but was 23 mg\kg P.

Dairy cows grazing a tropical grass pasture fertilized with 300 kg N\ha and with a 7-year history of phosphorus fertilizer at either 0 or 45 kg P\ha were given a P supplement in a 2i2 factorial experiment at Kairi Research Station, Queensland, Australia. Milk yield, fat-corrected milk yield, yields of milk fat, protein and lactose, and protein content of milk were increased (P 0n05) with P fertilizer. There was no response in milk yield or any component of milk to the provision of a P supplement. It is concluded that the milk response recorded in this experiment was due to P fertilizer leading to additional pasture on offer and increased pasture intake. The lack of response to additional P in the form of a supplement indicates that these pastures can supply adequate P for cows producing 20 kg\day even after 8 years without P fertilizer.

Holstein-Friesian cows in mid to late lactation grazed tropical grass-legume pastures with no supplement (C); 2.7 kg DM molasses/cow.day (M); or 2.6 kg DM molasses + 2.5 kg DM grain/cow.day (MG). Daily milk yields over the 8 week experimental period were 10.4, 11.2 and 12.9 kg/cow for C, M and MG. The MG supplementation increased solids-not-fat (SNF), protein and lactose percentages in milk, with average SNF values of 8.02, 8.10 and 8.24% (P<0.05), and lactose values 4.46,4.50 and 4.58% (P<0.057), for weeks 5-8; and average protein values for weeks 1-8 of 2.96, 3.02 and 3.10% (P<0.05) for C, M and MG, respectively. Molasses alone did not substantially increase the protein and lactose content of milk, but additional energy in the form of maize increased these values. If SNF percentages in milk were low, maize plus molasses feeding did not improve the quality to the legal minimum of 8.5% in 8 weeks.