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Effect of age of regrowth of kikuyu grass (Pennisetum clandestinum) on production, milk quality and balance of nitrogen in Holstein cows

Abstract:

To evaluate the effect of the age of regrowth on intake, milk production and milk quality and the efficiency of the use of kikuyo grass (Pennisetum clansdestinum), an experiment was performed with six Holstein multiparous cows in the second third of lactation (156+39.5 days). The cows were assigned to one of two treatments in a crossover design with 14 experimental days in each period and 25 days between experimental periods. Treatments consisted of the offer of 3.0 kg/100 kg of live weight of 45.5 (young) or 79.5 days of regrowth kikuyu grass (mature). During the three days before each period, milk production was measured, the animals were weighted and body condition score was determined. Samples of milk were analyzed for crude protein and fat and fecal samples were taken to analyze for basal chromium. Each cow was allocated to an individual plot in a kikuyu grass pasture. Cows were restrained to their plot by a cord tied to an iron stake. Cows were supplemented twice daily during milking. Total supplement per cow was assigned at a ratio of 1 kg of supplement per each 3.6+0.11Kg of milk produced above 8 L (average milk production for kikuyu grass). Dry matter intake was determined using markers at each experimental period. Individual milk samples were collected to determine crude protein, fat and total solids; samples were also taken from the pasture of both young and mature kikuyu and analyzed for crude protein, crude protein insoluble in neutral detergent, lignin, ash, ether extract and the content of non-structural carbohydrates and net energy of lactation. In the last experimental day, live weight and body condition score of each cow were determined. Dry matter intake of the forage and total dry matter intake and the efficiency of forage use were calculated. Age of regrowth affected the concentration of crude protein and ash content of the grass. The young grass presented a lower final height and less production of green forage. Age of regrowth did not affect total dry matter intake, production or composition of milk. It can be concluded that under the experimental conditions of this study, the age of regrowth affected partially the nutritional composition and the yield of kikuyu grass without affecting intake, milk production or milk quality.