| Abstrakt: |
Simple Summary: Creatine is a metabolite that animals use to store energy within tissues. Animals, including cattle, can synthesize creatine by first generating guanidinoacetic acid from the amino acids glycine and arginine, followed by conversion of guanidinoacetic acid to creatine. In some situations, the body's production of creatine is not adequate to support maximal growth. We examined the supplementation of guanidinoacetic acid to calves fed milk replacer to determine if growth performance would be enhanced. Supplementation of guanidinoacetic acid tended to improve the growth of the calves, which may suggest that milk replacer alone was not sufficient to supply adequate amounts of creatine through the combination of diet and endogenous production in the body. Thus, dietary supplementation with guanidinoacetic acid may be a feasible means of improving growth in calves fed diets containing inadequate amounts of creatine. Guanidinoacetic acid (GAA) is the direct precursor to creatine, which serves as an energy reserve mechanism in the body. We evaluated the effects of GAA supplementation on the growth performance of calves fed milk replacer. Forty-five Holstein–Angus steer calves (40.9 kg, approximately 1 week old) were assigned to 1 of 3 treatments to assess growth performance and data from 41 calves were analyzed. Treatments were provided in the milk replacer for 42 d and included 0, 1, or 2 g GAA/d. Calves were fed 2.84 L milk replacer twice daily with ad libitum access to starter feed and water. Treatments ended on day 42 prior to a 17-day weaning period. Supplementation of GAA increased (p < 0.01) plasma concentrations of GAA (0.42, 0.51, and 0.67 mg/L for 0, 1, and 2 g GAA/d, respectively) and creatine (18.7, 22.1, and 24.4 mg/L for 0, 1, and 2 g GAA/d, respectively). Bodyweight tended to linearly increase (p = 0.09) with increasing GAA on d 59 (91.2, 98.3, and 98.6 kg for 0, 1, and 2 g GAA/d, respectively). Daily gains from day 0 to 59 tended to increase with GAA provision (p = 0.09; 0.86, 0.97, and 0.98 kg/d for 0, 1, and 2 g GAA/d, respectively). Starter feed dry matter intake tended to linearly increase (p = 0.06) with GAA supplementation (0.201, 0.278, and 0.286 kg/d for 0, 1, and 2 g GAA/d, respectively). Treatments providing 1 and 2 g GAA/d affected performance similarly. No differences among treatments were observed for health (respiratory and fecal) scores during the application of treatments or during the subsequent weaning period. The inclusion of GAA in milk replacer tended to increase the gain of calves, and this was associated with elevated starter feed intake. [ABSTRACT FROM AUTHOR] |
