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The effects of feeding increasing concentrations of corn oil on energy metabolism and nutrient balance in finishing beef steers

Hales, K. E., Foote, A. P., Brown-Brandl, T. M., Freetly, H. C.
J. Anim. Sci. 2017 v.95 no.2 pp. 939-948
beef cattle, corn, corn oil, dietary fat, digestibility, dry matter intake, energy, energy metabolism, feeding level, finishing, heat production, methane, methane production, nutrient balance, nutritional intervention, statistical models, steers
The use of added fat source is common in high-concentrate finishing diets. The objective of our experiment was to determine if feeding increasing concentrations of added dietary corn oil would decrease enteric methane production, increase the ME:DE ratio, and improve recovered energy (RE) in finishing beef steers. Four treatments were used in a replicated 4 × 4 Latin square (n = 8; initial BW = 397 kg ± 3.8). Data were analyzed using a Mixed model with the fixed effects of period and dietary treatment and random effects of square and steer within square. Treatments consisted of: (1) 0% added corn oil (Fat-0); (2) 2% added corn oil (Fat-2); (3) 4% added corn oil (Fat-4); (4) 6% added corn oil (Fat-6). Dry matter intake or GE intake did not differ across diets (P > 0.39). As a proportion of GE intake, fecal energy loss, DE, and urinary energy loss did not differ by treatment (P > 0.27). Additionally, methane energy respired decreased linearly as corn oil increased in the diet (P < 0.01). No differences were detected in ME loss as a proportion of GE intake (P > 0.98); however, the ME:DE ratio increased linearly as corn oil increased in the diet (P < 0.01). No differences in RE or heat production as a proportion of GE intake were noted (P > 0.59). Dry matter digestibility did not differ across diets (P > 0.36). Digestibility of NDF as a proportion of intake responded quadratically increasing from 0% corn to 4% corn oil and decreasing thereafter (P = 0.02). Furthermore, ether extract digestibility as a proportion of intake increased quadratically, increasing from 0 to 4% corn oil inclusion before reaching a plateau (P < 0.01). No differences were detected in OM digestibility across treatments (P > 0.35). From these data, we interpret that adding dietary fat decreases enteric methane production and increases the ME:DE ratio, in addition to increasing the amount of energy retained as fat and carbohydrate.