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

Abstract Text: 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 retained energy in finishing beef steers.  Four treatments were used in a replicated 4 × 4 Latin square (n = 8; initial BW = 397 kg ± 3.89).  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 and DE loss did not differ by treatment (P > 0.27); however, urinary energy loss tended to decrease linearly as corn oil increased in the diet (P = 0.09).  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 retained energy 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 urinary energy loss and enteric methane production while decreasing NDF digestibility when included at more than 4% of dietary DM.  Moreover, the ME:DE ratio increases linearly as dietary fat increases.  USDA is an equal opportunity provider and employer.

Keywords: Dietary fat, energetics, finishing cattle