Effect of formaldehyde treatment on the rumen digestion of barley and wheat grain and its influence on hay intake and digestion by sheep

Abstract

In Experiment 1, the effect of two additives containing formaldehyde on the degradability in the rumen of nitrogen (N) and protein-free dry matter (PFDM) in barley and wheat grain was measured using the nylon bag technique in three rumen fistulated sheep. One additive (FGA) was a commercially available product (Farmline Grain Additive) while the other was a mixture of formaldehyde and sulphuric acid (FAC) of similar formaldehyde concentration and titratable acid strength to the FGA. The grain was treated either milled, rolled or whole with amounts of either additive calculated to provide 3.2 g formaldehyde per 100 g grain crude protein. Both additives reduced the in sacco rate of digestion of N and PFDM to a similar extent. Differences between the additives were small and depended on the identity and the physical form of the grain. The effect of additive treatment was least for whole grain, but there was little difference between rolled or milled grain. In Experiment 2, the effects of treating rolled barley with a commercially available silage additive (Sylade 2) on hay ad libitum intake and diet digestibility were measured using eight mature wether sheep. The additive provided formaldehyde and sulphuric acid at similar rates to FAC (Experiment 1). In a changeover experiment with two 3-week periods, the sheep (average live weight 60 kg) received 600 g day −1 of either untreated or Sylade-treated barley, 90 g day −1 of soya bean meal and 10 g day −1 of a mineral supplement. The concentrates were offered in two equal meals at 0900 and 1700 h and there were no refusals. In addition, hay and water were made continuously available. Sylade treatment of the barley increased hay dry matter intake from 1084 to 1241 g day −1 ( P<0.05), but diet dry matter digestibility measured over the last 3 days of each period was unaffected. In a parallel study, in which two rumen fistulated wether sheep received the same rations, hay digestion rates measured in sacco were increased by Sylade treatment of the barley. This effect was associated with higher rumen liquor pH values and reduced total concentrations of volatile fatty acids (VFA) although VFA proportions were unaffected.