Dorper?×?Santa Ines F1 crossbred lambs under different grazing times and supplement levels in tropical regions: performance and macromineral requirements

摘要

The objective of this study was to evaluate the performance and net requirements for calcium(Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) in Dorper Santa Ines F1crossbred lambs under different grazing times and supplement levels. We used 36 uncastratedmale lambs with initial body weights (BW) of 15.5 ± 1.9 kg. Twelve animals were used as a reference group, and the remaining 24 animals were divided into three treatments according to grazing time and supplement level: 9 h 1.2% BW, 6 h 0.84% BW and 3 h 0.48% BW. There wereincreases in the final BW, average daily gain (ADG) and dry matter intake (DMI) of pasture(p .05) in lambs that grazed longer (9 h 1.2% BW). Feed efficiency (G/F ratio) was similarbetween the 9 h 1.2% BW and 6 h 0.84% BW groups and both the groups were greater thanthe 3 h 0.48% BW. However, there was a reduction in the DMI of concentrate, total DMI, andCa, P, Mg and K intake (p .05) for lambs that grazed longer. However, pasture DMI and sodiumintake increased (p .05) in animals that grazed for less time (3 h). The chemical composition ofthe empty bodies in DM, fat, ash, Ca and P showed the greatest values (p .05) in groups withanimals grazing 9 h with a supplement level of 1.2% BW. Net maintenance requirements were0.101–0.202 g Ca/day, 0.204–0.408 g P/day, 0.053–0.105 g Mg/day, 0.386–0.771 g K/day and0.105–0.211 g Na/day for crossbred lambs between 15 and 30 kg BW. For the same group, netrequirements to gain 100/200 g/day BW were 1.171/2.341–1.667/3.333 g Ca/day, 0.694/1.398–0.998/1.995 g P/day, 0.027/0.054–0.032/0.063 g Mg/day, 0.098/0.195–0.091/0.182 g K/dayand 0.315/0.629–0.311/0.621 g Na/day. Lambs grazing longer (9 h 1.2% BW) displayed increasedADG and concentrate intake and reduced forage intake, which increased intake and body retention of Ca, P, Mg and K.