Two strategies to increase nutrient supply to early lactation dairy cows were compared and the cumulative effects on pasture quality and milk production were investigated. In a farmlet experiment the effect of feeding pasture only, or pasture plus concentrate (4kg/cow/day) at low (3.5 cm) or high (5.0 cm) post-grazing pasture residual (PGPR) was determined using a 2 x 2 factorial combination. Milk production for four groups of eight Friesian x Jersey dairy cows was measured within three consecutive grazing rotations during the first 12 weeks of lactation. PGPR for the low and high treatments remained constant throughout the 12 week period at 3.7 and 4.5 cm respectively. Mean milk solids production in the first, second and third rotation were 1.99 ± 0.12, 2.14 ± 0.10 and 2.01 ± 0.09 kg MS/cow/day respectively. Increasing PGPR from 3.7 to 4.5 cm did not affect pasture quality, milk production or milk composition. Concentrate feeding increased milk solids yield by 0.30 kg (P < 0.05) in the third rotation. Concentrate feeding also increased milk protein yield by 68 g (P <0.05), 104 g (P <0.05) and 167 g (P <0.001) in the first, second and third rotation respectively. When pasture quality is not altered by PGPR, feeding a concentrate is more effective at increasing nutrient supply than raising grazing height.
Proceedings of the New Zealand Society of Animal Production, Volume 73, Hamilton, 205-210, 2013
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