Protein supplementation to early lactation dairy cows grazing tropical grass: Performance and ruminal metabolism |
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| Authors: | Lucas Jado Chagas Camila Delveaux Araujo Batalha Marina de Arruda Camargo Danés José Maurício Santos Neto Fernanda Lopes Macedo Rodrigo da Silva Marques Flávio Augusto Portela Santos |
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| Institution: | 1. Department of Research and Development, Roullier Animal Nutrition, Minga Guazú, Paraguay;2. Instituto de Zootecnia, Centro Avançado de Pesquisa de Bovinos de Corte, Sertaozinho, Brazil;3. Department of Animal Science, University of Lavras, Lavras, Brazil;4. Department of Animal Science, Michigan State University, East Lansing, Michigan, USA;5. Department of Animal Science, University of Sao Paulo, São Paulo, Brazil;6. Department of Animal and Range Science, Montana State University, Bozeman, Montana, USA |
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| Abstract: | This experiment was designed to evaluate the effects of different concentrate crude protein (CP) concentration on performance, metabolism and efficiency of N utilization (ENU) on early-lactation dairy cows grazing intensively managed tropical grass. Thirty cows were used in a ten replicated 3 × 3 Latin square design. The treatments consisted of three levels of concentrate CP: 7.9%, 15.4%, and 20.5% offered at a rate of 1 kg (as-fed basis)/3 kg of milk. The cows fed low and medium CP had negative balance of rumen degradable protein and metabolizable protein. Increasing CP tended to linearly increase DMI, 3.5% FCM and milk casein, and linearly increased the yields of milk fat and protein. Increasing CP linearly increased the intake of N, the concentration of rumen NH3–N, and the losses of N in milk, urine, and feces. Increasing dietary CP linearly increased the molar proportion of butyrate but had no effect on the other rumen VFAs and no effect on microbial yield. In conclusion, feeding a concentrate with 20.5% of CP to early-lactation dairy cows grazing tropical grasses, leading to a 17.8% CP diet, tended to increase DMI, increased the yield of 3.5% FCM and the milk N excretion, and decreased ENU by 32%. |
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| Keywords: | dairy cattle milk urea nitrogen nitrogen metabolism tropical grass |
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