Growth of heifers grazing on dry season and limited access to Leucaena leucocephala, molasses / urea and / or concentrate

Abstract

During 5 periods of 35 days of progressive drought, 24 heifers (278 kg of average LW, in four equal groups, grazed with weekly rotation in three paddocks (6.59 ha in total) of heterogeneous unfertilized grasses (G). In periods 1 and 2, four treatments (factorial 2 x 2) were based on the factors (a) access during 3 h / d rotational grazing in three paddocks (2.57 ha) of leucaena in association with grasses (GL) and (b) 2.5 kg / cab / d of cane molasses with 3% urea (MU). In 70 days, GDP was 0.18 kg in control (I); MU (II), .30; GL (III} .35 and of MU and GL (IV) .38 kg, respectively. In period 3, it was modified by adding 2 kg / cab / d of concentrated feed, control (I) -.02 kg / d; in II -.34 kg / d, in III +.32 and in IV +.66 kg / d, the latter exceeding (P <.10) T-1 and T-2. In periods 4 and 5, the addition of 4 and 2 kg daily of concentrates in I and II resulted in gains of .78 and .63 kg, while in III and IV, the daily rate was reduced to 0.26 and 0.30 kg. For 175 days, III and IV (GL without concentrates) resulted in daily gains of 0.31 and 0.40 kg versus 0.38 and 0.30 kg for I and II (G with concentrates}. Between the periods, the crude protein content in G and GL ranged from 8.9 to 12.3% and from 14.9 to 18.0%; and in vitro digestibility from 73.8 to 78.3% and 72.7 to 77.4%, respectively. Limited supply of Forage G, rather than deficient nutrient composition, was the main factor limiting animal performance; GL corrected this storage more efficiently than MU.