Effects of supplementation containing rumen by-pass protein on parasitism in grazing lambs

•Protein supplementation improved gain and reduced FEC in grazing lambs•Adding fish meal to supplement increased gain and reduced FEC•Lambbody weight gain and PCV was improved when supplemeted with rumen undegradable protein Parasitic gastro-intestinal nematodes (GIN) are a serious challenge to sustainable small ruminant health and performance on pasture. Management practices including protein supplementation can help mitigate the deleterious effects of GIN and sustain livestock performance. We postulated that a combination of protein supplementation and grazing management would suppress GIN infection and contribute to marketable lamb gain in organic and conventional production systems. Objectives were to determine if performance and GIN infection of weaned lambs on pasture were influenced by 1) protein supplementation; 2) protein supplement source that included rumen undegradable protein (RUP) with the addition of a fish oil treatment to address energy concentration in the feed supplement; and 3) protein supplementation with RUP based on body mass and grazing interval duration. We found that lambs supplemented with RUP had increased BW and PCV, and reduced FEC and FAMACHA© scores. Body weight gains increased as the corn-fishmeal supplement was increased from 1 % to 2 % BW. Parasitized lambs may have increased dietary protein requirements that can be met in part by provision of RUP in the form of fish meal. Our work demonstrates the practical success of improved animal performance with protein supplementation based on body weight, and the importance of protein supplement source. The RUP supplement, such as fish meal, appears to have significant bearing on immunological responses as inferred from observed changes in FEC associated with the target GIN, H. contortus.