Relationship between supplemental protein and ruminal fermentation of an orchardgrass-based herbage diet
2010
Soder, K.J. | Gregorini, P.
Forty-eight crossbred lambs (29.0 ± 4.5 kg; 24 ewes, 24 wethers; 1 ewe and 1 wether/pen; 6 pens/treatment) were blocked by BW and randomly assigned to 1 of 4 isocaloric, isonitrogenous treatments containing 0, 15, 30, or 45% crude glycerin (DM basis). Diets, which were offered ad libitum, were primarily composed of 15% chopped hay, 25% dried distillers grains with solubles, and cracked corn, which was replaced with increasing amounts of crude glycerin. Lambs were weighed in 21-d intervals and selected for slaughter when they reached approximately 55 kg of BW. Blood samples were collected on d 57 for analysis of metabolic parameters. Carcass characteristics were collected after a 48-h chill. Days on feed increased linearly (P < 0.001), ADG decreased quadratically (P = 0.02), and both DMI and G:F decreased linearly (P < 0.001) with increasing amounts of glycerin in the diet. Although HCW and LM area did not differ as a result of treatment (P > = 0.31), DP, 12th-rib fat thickness, and LM ether extract all decreased linearly with concomitant increases in glycerin (P < = 0.02). Serum glucose and insulin concentrations decreased linearly with increasing amounts of glycerin in the diet (P < = 0.02), and BHBA concentrations were greater for lambs fed glycerin than those not fed glycerin (P < 0.001). Data from the current study suggest that although feeding up to 15% crude glycerin in the diets of finishing lambs does not differ from feeding no glycerin, feeding 30% or more may have deleterious effects on feedlot performance, carcass quality, and both serum metabolite and hormone concentrations.
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