The evaluation of formaldehyde-treated sunflower seed-casein supplement as a source of linoleic acid for ruminant lipids

Abstract

Studies have been made of the digestion and utilization by sheep of a sunflower seed-casein supplement protected by formaldehyde treatment against ruminal degradation. Digestion studies suggested that about 40% of the linoleic acid (18:2) in the supplement was protected against hydrogenation, and that the 18:2 that passed from the stomach was almost completely absorbed from the small intestine. Four groups of lambs were offered diets designed to provide the same amounts of amino acids and net energy but varying amounts of volatile fatty acids, 18:2 and other long-chain fatty acids. The supplemented lambs grew at similar rates and the carcasses contained the same amounts of fat. It was estimated that 53–60% of the 18:2 absorbed from the small intestine was incorporated into carcass lipids. The incorporation was not affected by the relative proportions of metabolites derived from the diets. When the supplement was offered at two levels to lambs fed on lucerne hay, the intake of dry matter remained constant. Hence a reduction in the intake of lucerne hay occurred but the total intake of nutrients was substantially increased.