Document Type : Original Article


1 Department of Animal and Fish Production, Faculty of Agriculture, Alexandria University, Alexandria 21545, Egypt.

2 Livestock Research Department, Arid Land Research institute, city of scientific Research and Technological Applications, New Borg El-Arab, Alexandria, Egypt.


Effect of rumen-protected lysine in the form of Hydroxyl methyl lysine (HML) on average daily gain (ADG), dry matter intake (DMI), nutrient digestibility,  nitrogen balance blood metabolites, were evaluated in two experiments using growing Barki lambs. In first experiment, fifteen lambs were housed individually and assigned into three equal groups fed on basal diet (no lysine-control), free lysine (positive control, F-LYS) and protected lysine (P-LYS) equivalent to 3 g/d of lysine. The experiment lasted for 10 week to evaluate feed intake, ADG and blood metabolites. No effect (P>0.05) of treatment on ADG, DMI and feed efficiency was observed. Whereas, treatment × time interaction tendency (P=0.07) as showed an increased in ADG as lysine supplemented as P-LYS compared to F-LYS (P=0.05) and control (P<0.05) at the last 2 weeks. No effect (P>0.05) of treatment was observed on serum total protein (TP), albumin (Alb), globulin (Glob), urea, glucose (G), cholesterol (CH) and triglycerides (TG) concentrations. However, treatment × time interaction (P=0.06) tendency existed as P-LYS increased (P<0.05) TP, Alb and Glob only at wk. 2 and reduced (P<0.05) serum urea only at the last 2 weeks. Further, no treatment effect (P>0.05) was found on rumen ammonia nitrogen (NH3-N), pH and protozoa numbers. In Exp.2, (digestibility trial), twelve lambs from Exp.1 were kept in metabolic cages and received their respective treatments for 7 days as collection period. No response (P>0.05) to P-LYS supplementation was observed on nutrient digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF) compared to F-LYS and control. A tendency (P=0.09) for treatment on nitrogen balance (NB) and retained nitrogen (RN, P=0.06) was found. P-LYS increased (P=0.05) NB to 7.1±0.14 vs. 4.8±0.3g/d and RN (P<0.05) from 37.9 vs. 25.59% in the control. However, P-LYS did not improve lambs performance under the basal diet fed that might have not been deficient enough in LYS amino acid, the improved ADG and decreased plasma urea at the last two weeks along with the slight improvement in NB and RN indicates the P-LYS has a potential under specific feeding regimes.