Vitamin A status of ewes and lambs grazing nitrogen fertilized orchardgrass pastures.

Experiments described were conducted to define the vitamin A status of ewes and lambs grazing orchardgrass fertilized at various levels of N or N plus micro-elements. Four fertilizer treatments (56 kg N/ha; 168 kg N/ha; 504 kg N/ha; 504 kg N/ha + Co, Cu, Mo, Zn and S) were applied to replicated hay and pasture plots of Potomac orchardgrass on a Gilpin silt loam soil. Ewe lambs were allocated randomly to fertilizer t reatment groups and maintained on pasture and hay from 1967 to 1971. Forage nitrate and carotene levels increased with increasing levels of N fertilizer, but fertilizer level did not affect ewe blood carotene, blood vitamin A or liver vitamin A levels. Overall average values were .06% NO3-N and 127 mg carotene per kilogram of forage DM, 12.3 meg carotene and 26.7 meg vitamin A per 100 ml of blood, and 92.5 meg vitamin A per gram of fresh liver. Correlation analysis of animal data (blood carotene, blood vitamin A, and liver vitamin A) with forage components (nitrate and carotene) indicated that while some co-efficients were significant (P<.05), there was little association of animal and plant factors. Blood and liver vitamin A tended to be higher in animals grazing pastures treated with high levels of N. No measurable vitamin A was present in livers of newborn lambs, but large liver concen-