Effect of treatment with formaldehyde and intraperitoneal supplementation with D-L methionine on the digestion and utilisation of a hay diet by sheep

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Abstract
Ryegrass-clover herbage was sprayed with dilute solutions of formaldehyde (HCHO) while being made into hay by field curing. Application rates were 0, 3.7, 7.5, 15.0, and 30.0% (w/w) HCHO of the forage crude protein treated. The digestion of nitrogen (N) in vitro in the 3.7 and 7.5% HCHO-treated hays was similar to that of untreated hay. The two higher rates of HCHO application markedly decreased the amount of N digested by rumen micro-organisms and markedly increased the amount of N subsequently digested in acid-pepsin conditions. Untreated hay and hay treated with 15.0 and 30.0% HCHO was fed to Romney wethers at the maintenance level of energy intake, with and without intraperitoneal injections of D-L methionine. Formaldehyde treatment decreased the concentration of ammonia and volatile fatty acids (VFA) in rumen fluid, caused a very small increase in the digestibility of energy, but decreased the digestibility of N by approximately 4.5 percentage units. Methionine supplementation increased the digestibility of energy and N by 1.5-2.0 percentage units. It was concluded that treatment of the hay with the two higher rates of HCHO would increase the amount of crude protein digested in the post-ruminal region of the digestive system. This was achieved at the expense of some reduction in the overall digestibility of N but not of energy.