Effects of Nitrogen and Micro-Element Fertilization on Quality of Pasture and on the Health, Nutritional Status and Reproductive Performance of Sheep2

The data obtained in this study indicate that, in general, nitrogen fertilized orchardgrass in the form of pasture or hay provided an adequate source of most nutrients for a breeding flock of ewes over an extended period of time. A requirement for supplemental P was evident across all treatments after 1 year, although P levels in the forage were adequate by N.R.C. standards. Nitrogen and available energy concentrations in the herbage and hay were apparently adequate, with the exception of 1 year in which the feeding of a poor quality, late-cut hay during the latter part of pregnancy resulted in impaired reproductive performance in ewes and adverse effects on the health and growth of lambs on the low- and medium-N fertilization treatments.Increasing increments of N fertilizer, and the incorporation of micro-elements at a high level of N, had certain specific effects on metabolism and performance of sheep. In the first year, a higher incidence of thyroid abnormalities was noted in lambs born from ewes on the high N treatments. Although ewes on the high N and high N + micro-element treatments maintained higher body weights during pregnancy, birth weight of lambs born from ewes on these treatments tended to be lower. High levels of N fertilization depressed the intake of herbage in spring, but little effect was noted on body weight of the ewes during the spring to autumn grazing season.