This study aimed to evaluate the effects of four levels of crude glycerin (0, 50, 100, or 150 g/kg on a dry matter basis) on intake, digestibility, production performance, and ruminal parameters for finishing Boer crossbred goats. Thirty-two crossbred, castrated Boer × undefined breed goat kids, with an initial average weight of 17.8 ± 2.2 kg and approximately four months old, were distributed in a completely randomized design, with four treatments and eight repetitions. The dry matter and neutral detergent fiber intakes, both in g/day and percent of body weight, linearly decreased (p ≤ 0.05) with increased inclusion levels of crude glycerin in the diet. The dietary crude glycerin levels linearly decreased (p ≤ 0.01) the digestibility coefficients of ether extract and quadratically increased (p = 0.04) digestibility coefficients of neutral detergent fiber. The final weight, total weight gain, and average daily gain for the animals showed a linear decrease (p ≤ 0.02) as dietary crude glycerin levels increased. The addition of crude glycerin caused a linear increase in ruminal pH (p ≤ 0.01), which ranged from 6.27 to 6.49 for diets with 0 and 150 g/kg crude glycerin, respectively. The concentration of ruminal NH3-N exhibited a linear decrease as the crude glycerin inclusion levels increased (p ≤ 0.01). Total short-chain fatty acid (SCFA) concentration, individual molar ratio, and the acetate: Propionate ratio in the ruminal fluid of the animals were not influenced (p ≥ 0.07) by the dietary crude glycerin levels. These data indicate that crude glycerin should not be used to replace ground corn in the diets of growing goats that are finished in a feedlot because the substitution reduces the intake and digestibility of several nutrients and decreases performance.
Keywords: alternative feed; biodiesel; feedlot; glycerol; weight gain.