Effect of Exogenous Enzyme Mixture on Growth Performance, Digestibility and Some Rumen Parameters of Finishing Lambs Fed High Whole Grain Hulled Barley Diet

Abstract

Background: Whole grain hulled barley has several nutritional limitations in diets for ruminants. Its fibrous hull which is resistant to ruminal microbial degradation and this could decrease performance. Therefore, tools that optimize the use of barley hull are required. Exogenous enzyme products including fibrolytic enzymes may be an important tool to improve the digestibility of whole grain, feed and improve the efficiency of lambs. Thus, this study aimed to investigate the effects of the supplementary exogenous enzyme mixture at three different levels on growth performance, digestibility and ruminal fermentation of male finishing lambs fed diets containing whole barley grain. Methods: Twenty-one Karayaka lamb (29.36 +/- 1.32 kg initial weight) were assigned to three experimental treatments: (1) Control, diet without exogenous enzyme; (2) 5 exogenous enzyme, diet with 5 g exogenous enzyme/head/day) and (3) 10 exogenous enzyme, diet with 10 exogenous enzyme g/head/day). Forage-free finishing diets were composed of 70% whole barley and 30% protein supplement. The experimental diet was offered to the animals for 56 days. Nutrient digestibility was determined during the last 4 days of the experiment. Result: The supplementation of exogenous enzyme did not affect dry matter intake. Increasing exogenous enzyme in whole barley grain-based diets did not alter digestibility of dry matter, organic matter, crude protein and neutral detergent fibre. Regarding, mean ruminal pH, NH3-N and ruminal total volatile fatty acid, there was no difference between control and both exogenous enzyme mixture levels. The findings of the current study indicate that there was no effect of exogenous enzyme mixture on lamb performance, digestibility and ruminal fermentation fed whole grain hulled barley-based diets in Karayaka lambs. Therefore, supplementing such diets with exogenous enzyme for fatting Karayaka lambs is not recommended.