|Current Sheep Research
There has been an increased interest in using Dorper sheep in crossbreeding programs with local sheep breeds in the USVI. The Dorper breed was chosen for its heavy muscling in an attempt to increase the growth rate and size of lambs produced for the local market.
Because of local interest in the use of Dorper sheep in crossbreeding programs we conducted a project, funded by the USDA-NIFA TSTAR Program. The results of that project showed that Dorper x St. Croix White lambs grow faster and yield heavier carcasses than St. Croix White lambs when they are raised on either a concentrate or forage ration after weaning (See Relevant Publications below).
The Dorper was developed for an arid environment and is not known for prolificacy, unlike the indigenous hair sheep in the Caribbean that have been selected for a humid environment and are prolific. There is little information on how Dorper x St. Croix White crossbred ewes will perform under tropical conditions found in the USVI and the greater Caribbean. A crossbred flock has been established to compare the production traits of Dorper X St. Croix White ewes to St. Croix White ewes under tropical conditions. Ewes are being managed in an extensive system, with rotational grazing and an accelerated lambing cycle.
In the accelerated lambing system currently being used, lambs are weaned at 63 days of age to allow the ewes a brief rest between lactation and rebreeding. Because the Dorper x St. Croix White lambs don’t have the same level of parasite tolerance as the St. Croix White lambs there has been a relatively high mortality rate post weaning. A long-term project has just been initiated in 2008 to evaluate the impact of later weaning (90 or 120 days of age) on lamb and ewe production traits. Lamb growth and survival will be evaluated in lambs weaned at either 63, 90 or 120 days of age. Ewe productivity will also be evaluated, and will include weight change, fertility, cyclicity, milk production and ability to breed back.
Heat stress is a common problem in ruminant production throughout the tropics. Genetic selection has been used to develop breeds that are adapted to the tropical environment. On the island of St. Croix there are two breeds of adapted livestock, Senepol cattle and St Croix White hair sheep. Both of these breeds play a role in the agriculture industry of the US Virgin Islands and the wider Caribbean and Central and South America. Previously funded TSTAR research in our laboratory using thermal imaging to measure body temperature in St Croix White and Dorper X St Croix White hair sheep found no differences indicating that the crossbred sheep maintain the adaptation to the environment evident in the local breed of hair sheep.