Cows grazing a restricted pasture allowance of 25 kg DM/cow/day during November (75 days in milk) were offered five supplementary feeds in a factorial experiment. The supplements were isoenergenic supplying an additional 68 MJME/cow/day but varied in whether the energy source was lipid or carbhydrate (rapeseed vs maize), crushed or whole rapeseed (cruide protein (CP), 20.6%), or with and without ruminally protected protein (formaldehyde treated sunflower meal, 37.8% CP). The CP contents of the pasture and the maize supplement were 14.7% and 9% respectively giving an average CP of the feed consumed of 13%. Cows on the control treatment supplemented with maize grain produced means of 10.5 l/d of milk, 0.61 kg/d fat, 0.43 kg/d of protein and 1.03 kg/d of milksolids. Partial replacement of maize with 20 MJME/cow/day of rapeseed (CP of supplement, 11.8%) increased daily milk (9.3%), fat (8.6%), protein (4.4%) and milksolids (6.9%) yields. Crushed rapeseed resulted in twice the yield increase as whole rapeseed. Additional replacement of maize with 13 MJME/cow/day of ruminally protected protein (CPO of supplement 18%) resulted in further increases of 15.9%, 16%, 17.4% and 16.8% for milk, fat, protein and milksolids respectively. The response to ruminally protected protein was greater when incorporated with maize/crushed rapeseed than maize/whole rapeseed. Crushed rapeseed depressed fat and protein content in milk. Other supplements had no effect on fat, protein or lactose contents. Replacement of maize with crushed rapeseed and ruminally protected protein increased yields of milk (36.1%), fat (32.9%), protein (23.5%) and milksolids (31.8%) compared to maize alone. For cows 75 days in milk the results demonstrated that a dairy ration comprising 13-14% CP provided insufficient protein to sustain full milk production.
Proceedings of the New Zealand Society of Animal Production, Volume 59, , 184-187, 1999
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