DRY MATTER INTAKE ESTIMATION OF STAR GRASS (Cynodon plctostachyus K. Schum.) BY GRAZING DAIRY COWS THROUGH OF N-ALKANES, FORAGE CUTTING AND GRAZING BEHAVIOUR

Abstract

The objective of the present study was to compare three techniques, n-alkanes, herbage cutting and grazing behavior, to estimate dry matter intake (DMI) by cows grazing on swards of Star grass. Two experiments with a 4 x 4 Latin square design were used. In both experiments cows were supplemented with 6 kg of a concentrate composed of 81% ground maize, 10% canola cake, 7% molasses and 2% urea, in addition four levels of coffee pulp were feed to the experimental cows 0, 600, 900 and 1200 g cow day-1 as treatments 1, 2, 3 and 4 respectively. In experiment 1 no significant differences (P>0.05) were observed in grass DMI between the n-alkanes, 2.9 kg DM cow-1 day-1, and the herbage cutting technique, 3.3 kg DM cow-1 day-1. For the second experiment no significant differences (P>0.05) were observed between the n-alkanes, 6.7 kg DM cow-1 day-1, and the grazing behavior technique, 6.3 kg DM cow-1 day-1. A significant relationship (r2=0.80, P<0.05) was observed between the n-alkanes and the herbage cutting techniques for experiment 1. On the contrary, a small relationship (r2=0.42, P<0.05) was observed between the n-alkanes and the grazing behavior techniques.  It is concluded that the n-alkanes technique was the most precise to estimate DMI for cows grazing Star grass prairies, the grazing behavior and herbage cutting techniques were less precise than the n-alkanes technique. The inclusion of coffee pulp at levels of 15% and 20% do not affect DMI of dairy cows therefore it is recommended the use of this by-product in order to reduce feeding cost of dairy cattle.