Growth Performance of St. Croix White Lambs Grazed on Low Quality Native Pasture Improved with No-till Sunn Hemp (Crotalaria juncea L.) in the U.S. Virgin Islands.

The objective of this study was to evaluate live animal performance of Dorper X St. Croix White lambs managed by two different post-weaning grazing systems. The control grazing system represented conventional grazing on low quality native pasture (NP), and the second grazing system consisted of similar low quality NP, but improved with the tropical legume Crotalaria juncea L. cv tropic sunn (Improved Pasture; IP) which is widely used as a cover crop.  After weaning and background grazing on native pasture for six months, lambs were stratified by weight and sex into either the NP or IP treatment. Both treatment grazing systems consisted of hurricane grass (Boithrocloa pertusa L.) and guinea grass (Panicum maximum L.). Hurricane grass is a low quality invasive forage that displaces higher quality guinea grass. The control of hurricane grass is labor intensive, costly, and requires conventional tillage and herbicides for removal prior to the reestablishment of the desired forage.  The IP treatment was improved with sunn hemp which was directly seeded into the hurricane grass sod using a Great Plains No-Till Drill at a seeding rate of 45 kg/ha. Lambs were rotationally grazed on both the NP and sunn hemp IP for 100 days. Compared to NP lambs, IP lambs were heavier at slaughter with a mean weight of 34.7 kg compared to NP lambs at 28.2 kg. During the grazing trial IP lambs had greater total weight gain than NP lambs (7.9 vs. 3.7 kg, respectively) and higher ADG than NP lambs (74 vs. 34.5 g/d, respectively. Results of this study indicate that the tropic sun cultivar of sunn hemp can be no-till drilled into low quality hurricane grass pasture, achieve a stand capable of increasing lamb performance, and can improve pasture quality through the inclusion of a palatable leguminous forage that withstands grazing pressure for over 100 days.