The effect on digestion in the rumen of a gradual increase in the content of fatty acids in the diet of sheep

Abstract

1. Two sheep were given cubed rations in which the fatty acid content was increased by about 12 g/day at the end of each week, until the daily intake became 74 g. 2. The apparent digestibility of the crude lipid increased with the increased intake, but there was no tendency for the digestibility of the fatty acids to increase or decrease regularly. 3. Comparison of faecal losses during the final periods, when a maximum amount of lipid was given, with the losses during the initial control periods showed that the excretion of dry matter, crude lipid and cellulose increased. The excretion of crude protein was unchanged and that of lipid- and cellulose-free dry matter decreased. There was a reduction in the production of methane of 17 kcal/100 kcal of additional fatty acids in the diet. 4. The concentration of the C 18 unsaturated acids in the rumen liquor reached a maximum during the 1st week on the diet containing the maximum amount of added fatty acids. The shape of the curves was consistent with rapid hydrogenation of linolenic acid. The concentration of stearic acid in the rumen liquor reached a maximum when the dietary acids increased to only 50% of their maximum value.