Nitrate Toxicity in Dairy Heifers. I. Effects on Reproduction, Growth, Lactation, and Vitamin A Nutrition

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Abstract
Forty-five dairy heifers were fed NO3 at levels of 0, 440 and 660 mg/kg body weight daily beginning 3 estrous cycles before breeding, or at 40, 150 or 240 days of pregnancy, continuing until they were killed at 30 days after parturition. Conception rate was lower in heifers fed 660 mg NO3. One abortion occurred in those fed the lower level of NO3 and 2 abortions and 2 deaths occurred in those fed the higher level. Growth, length of estrous cycles, length of gestation, birth weight and performance of calves, vitamin A and carotene nutrition, and milk production were similar in all groups. NO3 feeding increased the NO3 content of milk and meat but the contamination was so small that it did not appear to constitute a hazard to human health.