Responses to protected amino acids or protected protein in dairy
cows grazing ryegrass pastures in early lactation.
Rusdi and M.F.J. van Houtert
Animal and Veterinary Sciences Group, PO Box 84, Lincoln
University.
Proceedings of the New Zealand Society of Animal Production. 1997,
57: 120-125
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.
Keywords: NZSAPAB;
dairy cows; pasture; amino acids; metabolisable protein; milk
production.
Last Updated 12-09-1998
