Responses in Pregnant Ewes Fed Forages Containing Various Levels of Nitrate

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Abstract
In 1961-62, 25 pregnant ewes, divided into groups of 5, were individually fed pelleted alfalfa-timothy hay + 1.5% nitrate, or corn, oats, pigweed (Amaranthus-retroflexus) or lambsquarters (Chenopodium-album) forages containing 0.4 to 1.5% nitrate. Hemoglobin, methemo-globin, body weight and plasma vitamin A were not significantly affected by nitrate level. Liver vitamin A levels reflected carotene intake. No pathological changes could be attributed to nitrate. In 1962-63, 40 pregnant ewes divided among 6 groups were individually fed alfalfa-timothy hay with and without 3.4% added nitrate, or corn, oats, pigweed or lambsquarters containg 0.4, 2.6, 2.6, and 2.4% nitrate, respectively. The hay + 3.4% nitrate ration was unpalatable. Methemoglobinemia increased as feed consumption increased. Ewes fed oats, pigweed and lambsquarters developed higher hemoglobin and methemoglobin levels and higher blood volumes than ewes fed corn or hay. Two abortions associated with toxoplasmosis occurred in ewes fed hay. Three ewes fed hay + 3.4% nitrate aborted; nitrate was probably the cause, but E. coli was isolated in 2 instances. Two abortions associated with Pseudomonas aeruginosa and 2 stillbirths due to dystocia occurred from ewes fed oats. A ewe fed oats and one fed pigweed died. Birth weight of lambs was not significantly different among groups. Liver and plasma vitamin A levels reflected the level of dietary carotene.