Two-hundred-and-four Friesian dairy cows (4-9 years old) were allocated to 1 of 9 groups at calving (n=22-23) in August-September 1995. All cows grazed ryegrass pastures at a stocking rate of 3.1 cows/ha and received some maize silage and barley for the first weeks after calving. In addition, they received one of three experimental supplements in early lactation (weeks 2-11) or mid lactation (weeks 12-22) or late lactation (weeks 23-33). Experimental supplements were 1 kg/d barley only (BAR), 1 kg/d barley with 17 g/d protected methionine/lysine (BML) or 1 kg/d protected protein meal (PPM). Individual pasture intake was estimated twice (5 days) during each lactation stage with sub-groups of cows (n=8) using the alkane technique. Preliminary results for cows in the early and late lactation groups are presented. In cows supplemented in early lactation, supplement intake was lower than anticipated (BAR, BML and PPM: 0.73, 0.67 and 0.41 kg/d respectively). Mean pasture intake (17.4 kg dry matter [DM]/d), milk solid production (2.07 kg/d) or changes in live weight (+23 kg) and body condition (+0.02) did not differ between groups. Gross milk composition and milk protein composition were also unaffected. In cows supplemented during late lactation, supplement intake was 0.83, 0.84 and 0.68 kg/d for groups BAR, BML and PPM respectively. Mean pasture intake (14.3 kg DM/d), milk solid production (1.49 kg/d) and change in live weight (+11 kg) during the period of supplementation did not differ between groups. Although further work with higher levels of supplementation with protein or amino acids is required, these results suggest that neither MP supply nor methionine/lysine supply were limiting milk production in dairy cows grazing ryegrass-based pastures during early or late lactation.

, Rusdi, and MFJ Van Houtert

Proceedings of the New Zealand Society of Animal Production, Volume 57, , 120-125, 1997
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