Abstract
NO_3-N and NO_2-N concentrations of green-chopped forage sorghum harvested at the various stages were determined and physiological responses of the cow fed this sorghum were investigated, and furthermore nitrate poisoning was occurred by a dose of NaNO_3. These results were summarized as follows. 1. Comparing the stem with the leaf blade, NO_3-N concentration in the stem was much higher than that in the leaf blade, and the concentrations in both the stem and the leaf blade appeared to decrease with growing. There seemed to be no difference between NO_2-N concentration in the stem and that in the leaf blade, and the concentrations were very low. For that reason, the concentrations appeared to be neglected from the standpoint of nitrate poisoning. 2. In the case of feeding 50kg/day of green-chopped forage sorghum (300mg/100g dry weight, as NO_3-N) to the cows, various responses were observed. Blood NO_3-N was observed in all cows, and then it appeared to be excreted into urine. Methemoglobin was not observed in all cases. Clinically this degree of the amount of green-chopped forage sorghum didn't remarkably affect the cows. 3. When dosed 150g of NaNO_3 to the cow (body weight 480kg) at 9.00a.m. and. 5.00p.m., nitrate poisoning occurred after second dose. This amount of NaNO_3 was equivalent to the feeding of 10kg (dry matter basis) of green-chopped forage sorghum containing 500mg/100g dry weight as NO_3-N. However, when taken account of other reports and the individual difference of cow, the amount of approximately 400mg/100g dry weight appeared to be danger.
