Effects of L-carnitine on nitrogen retention and blood metabolites of growing steers and performance of finishing steers.

Abstract

Two experiments were conducted to evaluate L-carnitine supplementation to cattle fed grain-based diets. In Exp. 1, seven Angus-cross steers (216 kg) were used in a 7 x 4 incomplete Latin square experiment to evaluate the effects of supplemental L-carnitine on N balance and blood metabolites. Steers were fed a corn-based diet (17.5% CP) at 2.5% of BW. Treatments were 0, 0.25, 0.5, 1.0, 1.5, 2.0, and 3.0 g/d of supplemental carnitine. The 18-d periods included 13 d for adaptation and 5 d for collection of feces and urine. Blood was collected before feeding and 3 and 6 h after feeding on d 18 of each period. Dry matter intakes tended to be highest when 1.5 g/d of carnitine was supplied, but N retention was not affected by carnitine and averaged 29.3 g/d. Plasma carnitine concentrations and urinary excretion increased with increasing carnitine supply, indicating that at least some of the carnitine escaped ruminal degradation and was absorbed by the steers. Plasma concentrations of NEFA demonstrated a treatment x time interaction; they decreased linearly in response to carnitine before feeding but increased linearly in response to carnitine at 6 h after feeding. Serum insulin and plasma glucagon, IGF-I, cholesterol, triglyceride, and amino acids were not affected by carnitine. Plasma concentrations of glucose, glycerol, urea, and beta-hydroxybutyrate all were increased by some of the levels of carnitine supplementation, but results for these measurements did not follow easily described patterns and seemed to be related to differences in DMI. In Exp. 2, 95 crossbred steers (357 kg initial BW) were fed finishing diets (14.5% CP) for 129 d. Diets were based on steam-flaked corn and contained 6% alfalfa and 4% tallow. Feed intakes, gains, and feed efficiencies were not affected by supplementation with 2 g/d L-carnitine. However, steers receiving L-carnitine tended to have fatter carcasses, as indicated by tendencies (P < 0.2) for thicker backfat, higher marbling scores, and higher yield grades. In conclusion, carnitine supplementation did not alter lean deposition in growing steers but it did alter plasma NEFA concentrations of growing steers fed a corn-based diet and also seemed to increase fat deposition in finishing cattle.

Effects of dietary ruminally protected l‐carnitine on plasma metabolites in sheep following a sub‐lethal ammonia challenge

“…Given the fact that dietary RPLC above 0.25 g/day did not increase plasma LC concentrations and that plasma concentrations from both experiments resulted in similar plasma LC concentrations even when significantly different amounts of LC were consumed, three possibilities exist: either the RPLC was not absorbed from the intestine, the RPLC was absorbed but was rapidly excreted, or was rapidly metabolised upon absorption. Greenwood et al. (2001) reported that, in calves, urinary excretion of LC was elevated as the treatment increased from 0.25 to 3.00 g/day.…”

Influence of Canola and Sunflower Diet Amendments on Cattle Feedlot Manure

“…Additionally, fecal N for all diet treatments is assumed to be 50% of total N discharge in the control diet (which had adequate N supply) although values of 26 to 66% have been reported in the literature (Bierman et al, 1999; Cole et al, 2003; Hoffman et al, 2001; Kohn et al, 2005). All diets supplied adequate protein for cattle growth, so any excess N intake above the control diet is known to be excreted in the urine (Archibeque et al, 2002; Bolan et al, 2004; Greenwood et al, 2001; Wessels and Titgemeyer, 1997).…”

Numbers of Antral Follicles During Follicular Waves in Cattle: Evidence for High Variation Among Animals, Very High Repeatability in Individuals, and an Inverse Association with Serum Follicle-Stimulating Hormone Concentrations1

“…Concentration of IGF-I in serum samples was determined with use of a commercial two-site immunoradiometric assay (Diagnostic Systems Laboratories, Inc., Webster, TX) previously validated for bovine serum [23]. Serum samples (50 l) were acid-ethanol extracted per the manufacturer's instructions and run in duplicate in a single assay.…”