Effects of Diet on Methane, VFA Profile, and Performance of Growing Calves

Abstract Text:

An 84-d growing study evaluated forage quality (high-quality (HQ) vs low-quality (LQ)), inclusion of modified distillers grains plus solubles (MDGS; 0 or 40% de-oiled, 20 or 40% normal), and presence (200 mg daily) or absence of monensin on methane to carbon dioxide ratio (CH₄:CO₂), ruminal acetate to propionate ratio (A:P), and performance of growing calves.  Steers (n = 120; initial BW = 300 ± 25 kg) were individually fed in Calan gates.  Steers were stratified by initial BW and assigned randomly to one of ten treatments.  Factors were compared and main or simple effects presented, based on significance of an interaction (P < 0.10). Expired breath samples were collected from cattle throughout the study at feeding using an automated gas collection system and analyzed for CH₄:CO₂.  Rumen fluid collected via esophageal tubing on d 21 and 63, prior to feeding, was analyzed for VFA profile and microbial community analysis.  A forage quality × monensin interaction existed for CH₄:CO₂ (P = 0.02), as monensin decreased CH₄:CO₂ in LQ diets (P < 0.01), but had no effect in HQ diets (P > 0.77).  Inclusion and fat content of MDGS did not impact CH₄:CO₂(P > 0.43).  For A:P, a fat content × level of MDGS interaction existed (P = 0.01) as A:P was greater for 40% compared to 20% normal MDGS (P < 0.01) but unchanged for de-oiled MDGS (P > 0.72).  Cattle fed 40% de-oiled MDGS (P < 0.01) and monensin (P = 0.06) had lower A:P in HQ diets compared to normal MDGS or no monensin.  A forage quality × monensin interaction existed for ADG (P = 0.07), with steers fed monensin having 9% greater ADG in HQ diets, but ADG decreased by 4.2% in LQ diets when monensin was fed compared to none.  MDGS level × monensin interactions existed for ADG and G:F (P < 0.05).  Feeding monensin increased ADG in diets with 40% MDGS (P = 0.02) and had no effect in diets with no MDGS (P = 0.33).  Feeding monensin decreased G:F of cattle fed diets with no MDGS but had no impact when fed diets with 40% MDGS.  Cattle fed HQ were 23% more efficient (P < 0.01) compared to LQ.  Feeding MDGS impacted performance, but not methane, while forage quality impacted both performance and methane production of growing cattle.

Keywords:

feedlot, growing cattle, methane