Growth Performance, Nutrient Digestibility and Nitrogen Metabolism of Ram-Lambs Fed Single Feed Protein

The experiment was conducted to determine the effect of single feed proteins. Twenty native lambs were divided into five groups in individual metabolic cages and fed five different single protein sources including urea as control (Con), barley (Bar), cotton seed meal (CSM), corn gluten (CG) and canola meal (CM) for 75 days. During the last four days of the trial, faeces and urine were collected to determine nutrient digestibility and N balance. Blood samples were taken 3–4 h after feeding at the end of the trial. Results showed that average daily gain (ADG) followed approximately the same pattern as the dry matter (DM) intake. The ADG was higher in lambs fed with the CSM compared to other groups (P<0.05). Higher DM and N intake was recorded for CSM being significantly different from the Con, Bar and CG (P<0.05). Nutrient digestibility (DM, OM, CP, NDF, ADF, NFC and TDN) showed significant difference among groups (P<0.05). Plasma urea nitrogen was higher in lambs fed CSM compared with Con (P<0.05). Urine and digestible N were different between CSM and CM (P<0.05). Faecal N was significantly different among the treatments except Con (P<0.05) that was intermediate between CG and Bar. Purine derivatives, absorbed purine and daily microbial N were higher in Con group (P<0.05). The results showed that single feed proteins, by influencing nitrogen metabolism, can impact on feed intake, nutrient digestibility, microbial protein synthesis, purine derivatives and consequently lamb performance.