Desempenho de vacas leiteiras em pastagem de capim elefante (Pennisetum purpureum Schum.) suplementado com diferentes fontes de carboidratos

Abstract

Twelve (12) Holstein dairy cows were used in this study. Eight of those cows were multiparous, (with 73,14 ± 22,75 days in milk) and four were primiparous, (with 76,25 ± 30,35 days in milk). Cows were assigned to one of four treatments in a 4 x 4 triple simultaneous Latin square design. Cows grazed Elephant grass and they were supplemented with different kinds of concentrates which differed in the carbohydrate source as follows: ground dry corn (MG), citrus pulp plus ground dry corn (MP), citrus pulp (PC) and high moisture corn (MU). Cows that consumed high moisture corn showed higher forage intake (9,75 kg of DM), followed bay cows that consumed citrus pulp plus ground dry corn (8,8 kg of DM), citrus pulp (8,59 kg of DM) and ground dry corn (7,21 kg of DM). There was no difference between treatments neither in total milk production corrected for 3,5% or in milk production corrected for solids. Cows fed with ground dry corn and high moisture corn showed higher levels of milk protein and milk total solids (p<0,05) and cows fed citrus pulp showed higher levels of milk fat (p<0,01). Cows fed high moisture corn showed higher concentrations of propionate (p<0,01) and a lower relation acetate: propionate (p<0,05) in ruminal fluid. Cows that consumed high moisture corn showed lower levels of milk urea nitrogen (p<0,05). The lack of positive statistical response in cows consuming high moisture corn could be caused by the limited production potential of grazing systems as well as the genetic merit of the animals involved in this study or by heat stress suffered. In systems where milk payment does not have a defined economical value any of the carbohydrates sources tested could be used.