Influence of dietary carnitine in growing sheep fed diets containing non-protein nitrogen.

Abstract The influence of supplemental l -carnitine was investigated in growing sheep fed rations containing non-protein nitrogen (NPN). The experiment was conducted as a randomized block design with a 2×2 factorial arrangement of treatments. Lambs (77.4 kg BW, n =24) were fed a total mixed ration (12.1–13.6% CP) with two levels of l -carnitine (0 or 250 ppm) and two levels of NPN (urea contributing 0 or 50% of total dietary N) for a 50-day period. Jugular blood samples were collected at 0, 1, and 3 h post-feeding, and ruminal fluid samples were collected at 1 h post-feeding, during days 1, 8, 29, and 50 of the experiment. Average daily gain (121 versus 214 g) was lower ( P P P 4 ) concentrations (65.8 versus 78.4 ng/ml; P 4 :triiodothyronine (T 3 ) ratio (37.9 versus 43.9; P P l -carnitine (3.83 versus 3.70 mmol/l). Two oral urea load tests (OULT 1 and OULT 2) were conducted during the 50-day trial. Urea solutions (0.835 g/kg 0.75 BW) were administered as oral drenches. During the OULT 1 (day 10), plasma ammonia N and glucose concentrations were highest ( P l -carnitine compared with lambs fed control, l -carnitine, and NPN diets. During the OULT 2 (day 50), plasma ammonia N was highest ( P l -carnitine groups compared with the control and l -carnitine groups. Plasma glucose was lowest ( P l -carnitine group compared with the NPN and l -carnitine groups, but did not differ ( P >0.10) from the control group. Plasma urea N levels in both OULT 1 and OULT 2 were lower ( P l -carnitine groups compared with the control and l -carnitine groups. In the present experiment, production and plasma criteria were affected by NPN incorporation in the diets. Production criteria were not affected by inclusion of l -carnitine in the diet, however, l -carnitine reduced experimentally induced hyperammonemia by day 50 of the trial.