PASTURE PRODUCTION, DIET SELECTION AND LIVEWEIGHT GAINS OF CATTLE GRAZING BRACHIARIA-BRIZANTHA WITH OR WITHOUT ARACHIS-PINTOI AT 2 STOCKINGRATES IN THE ATLANTIC ZONE OF COSTA-RICA

Pastures of Brachiaria brizantha (Bb) alone or with Arachis pintoi (Bb + Ap) were rotationally grazed by 3 (LSR) and 6 (HSR) hd/ha. Mean 4-w eekly forage DM on offer ranged from 3.5 t/ha at the HSR for Bb to 6 t /ha at the LSR for both pasture types. Mean dry weight proportion of A p was 6% at the LSR and 34% at the HSR. The amount of Ap in the diet o f steers was about 50% at the HSR and 10% at the LSR. During two 7-day grazing cycles, the mean crude protein concentration of the diet at b oth stocking rates in Bb and at the LSR in Bb + Ap ranged from 7-9.5%, but at the HSR in Bb + Ap, it ranged from 15-18%. In vitro dry matter digestibility of the diet ranged from 61-66% in all treatments, excep t for Bb at the HSR in which it fell to 54.1% on the last day of grazi ng. Average daily gain was lowest for Bb at the HSR (291-377 g) and hi ghest for Bb + Ap at the LSR (452-551 g). The mean annual liveweight g ain (LWG) per animal ranged from 119 kg for Bb at HSR to 178 kg for Bb + Ap at the LSR. LWG/ha/yr ranged from 478 kg for Bb at the LSR to 93 7 kg for Bb + Ap at the HSR. Including Ap increased LWG/ha by 30% at t he HSR and 11% at the LSR. It was concluded that Ap is the best herbac eous legume presently available for the humid tropics of Costa Rica.