Abstract
The objective of this study was to evaluate the effects of replacing dry ground corn with crude glycerol on intake, apparent digestibility, performance, and carcass characteristics of finishing beef bulls. A completely randomized block design experiment with 25 d for adaptation and 100 d for data collection was conducted, in which 3,640 Nellore bulls (367 ± 36.8 kg; 18 ± 3 mo) were blocked by body weight and assigned to 20 pens. Bulls were randomly assigned to one of four treatments: 0, 5, 10, and 15% (dry matter basis) of crude glycerol in the diet. Initially, 20 bulls were slaughtered to serve as a reference to estimate initial empty body weight, which allowed for carcass gain calculation. Bulls were weighed at the beginning, at two-thirds, and at the end of the experiment for performance calculations. Carcass measurements were obtained by ultrasound. Fecal output was estimated using indigestible neutral detergent fiber as an internal marker. Data were analyzed using the mixed procedures in SAS 9.2 (SAS Institute Inc., Cary, NC). Intake of dry matter, organic matter, and neutral detergent fiber decreased linearly (P < 0.05) with crude glycerol inclusion. However, crude glycerol levels did not affect (P > 0.05) intakes of crude protein, non-fiber carbohydrates, and total digestible nutrients. Digestibility of dry matter, organic matter, neutral detergent fiber, and total digestible nutrients increased quadratically (P < 0.05) with the inclusion of crude glycerol in the diet. Crude glycerol inclusion did not change the intake of digestible dry matter, average daily gain, final body weight, carcass gain, carcass dressing, gain-to-feed ratio, Longissimus thoracis muscle area, and back and rump fat thicknesses (P > 0.05). These results suggest that crude glycerol may be included in finishing beef diets at levels up to 15% without impairing performance and carcass characteristics.
Highlights
Corn is typically the main feed ingredient used for finishing cattle in feedlots [1]
We hypothesized that crude glycerol (CG) may partially replace dry ground corn (DGC) as dietary energy source in the diet of finishing cattle diets and may be included at concentrations up to 15% [dry matter (DM) basis] without compromising intake, apparent digestibility, performance, and carcass characteristics
The digestibility of DM, organic matter (OM), and Total digestible nutrients (TDN) decreased when 5% CG was included in the diet compared with the control diet and increased when 10 and 15% CG was included in the diet (Fig 2)
Summary
Corn is typically the main feed ingredient used for finishing cattle in feedlots [1]. The growth of the biodiesel industry worldwide has increased the availability of low cost crude glycerol (CG), in Brazil alone, it has been estimated that in 2014 the country produced 3.42 billion liters of biodiesel, yielding 341 million liters of CG [2]. This may position CG as a viable alternative feed source for finishing cattle. The glycerol that escapes rumen fermentation may be converted to glucose in the liver [7] From both economic and energy perspectives, CG has the potential to partially replace corn as an alternative energy source for beef cattle finishing diets
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