Effect of substitution of distillers grains and glycerin for steam-flaked corn in finishing cattle diets on growth performance and carcass characteristics.

An experiment was conducted to determine the effect of substituting modified corn distillers grains with solubles (DGS) or crude soy glycerin (CG) for steam-flaked corn (SFC) in finishing diets on growth performance and carcass characteristics. Treatments were arranged as a 2 × 2 factorial with DGS (0% or 40%) and CG (0% or 10%) replacing dietary SFC in a basal diet. Growth performance and carcass traits were measured on 48 individually fed crossbred yearling cattle (21 steers and 27 heifers; 380 ± 37 kg). Cattle were randomly allotted to 48 Calan gate bunks. After the first 28 days, nine animals were removed from the study for health reasons or observed confirmation of consumption of feed from unassigned Calan gate bunk (n = 39). After the feeding period, cattle were harvested in two groups on day-124 and day-173. No DGS × CG interactions were observed (P > 0.10) for any dependent growth performance or carcass characteristic variable tested. Cattle-fed DGS as 40% of diet dry matter (DM) had greater (P< 0.01) dry matter intake (DMI), while CG inclusion at 10% of diet DM did not affect DMI (P = 0.16). Carcass-adjusted average daily gain (ADG) was not affected by DGS (P = 0.73) or CG (P = 0.28). Decreased (P = 0.03) carcass-adjusted gain-to-feed (G:F) was observed as the main effect of DGS. Greater DMI resulting from feeding DGS as 40% of diet DM appears to have driven the tendency for reduced G:F. Hot carcass weight, longissimus muscle area, 12th rib fat depth, yield grade, and marbling score were not (P> 0.10) influenced by DGS or CG. However, kidney, pelvic, fat (KPH) was increased (P = 0.01) when cattle were fed DGS as 40% of diet DM. Based on the findings presented, it is concluded that CG can substitute up to 10% of SFC in the diet without negatively affecting cattle growth performance or carcass characteristics, regardless of DGS inclusion as 40% of the diet DM.

Livestock producers have an opportunity to improve sustainably through the utilization of co-products of the bio-fuel industry through cattle feeding. Crude glycerin, although less commonly fed compared to distillers grains, provides an opportunity for cattle feeders to increase the versatility of feed ingredient sources without compromising performance. The present study examined the effect of substituting modified corn distillers grains and crude soy glycerin for steam­flaked corn in beef cattle finishing diets on cattle growth performance and carcass characteristics. Growth performance was not influenced by treatment suggesting that crude glycerin and modified corn distillers grains in finishing diets were effective substitutions for steam­flaked corn when market price permits.

Effect of inclusion of distillers grains with solubles and crude glycerin in beef cattle finishing diets on ruminal fermentation and fatty acid biohydrogenation.

An experiment was conducted to evaluate the impact of feeding bio-fuel co-products on ruminal fermentation characteristics and composition of omasal digesta flow. Four ruminally cannulated Holstein steers (371 ± 5 kg) were used in a 4 × 4 Latin Square design. Omasal sample collection and triple marker technique was used to quantify fatty acid omasal flow. Treatments were applied as a 2 × 2 factorial where a steam flaked corn (SFC) basal diet (DGS-N CG-N) was replaced with 40% of diet DM as corn distillers grains (DGS; DGS-Y CG-N) or 10% of diet DM as crude glycerin (DGS-N CG-Y) or 40% of diet DM distillers grains and 10% of diet DM as crude glycerin (DGS-Y CG-Y). No effects were observed for the interaction of DGS and glycerin on measured rumen characteristics. Dietary inclusion of glycerin decreased (P = 0.05) ruminal content 4-h post feeding on a DM basis but did not influence DMI (P = 0.64). Feeding DGS had no effect (P = 0.34) on particulate passage to the omasum (kg/d) in spite of greater (P = 0.04) DMI. Feeding DGS reduced flow rate (% of rumen volume/h) (P = 0.05) but did not affect total VFA concentration (P = 0.46) or average ruminal pH (P = 0.72). No differences (P > 0.05) were observed in ruminal parameters when feeding glycerin, besides ruminal particulate content (kg) on DM basis (P = 0.05). An interaction of DGS and glycerin affected intake of stearic (P < 0.01), linoleic (P < 0.01), and linolenic acid (P < 0.01). An interaction of DGS and glycerin did not affect individual fatty acid flow with respect to intake for stearic (P = 0.17), linoleic (P = 0.18), or linolenic acid (P = 0.66). Dietary inclusion of glycerin had no impact on g of linolenic (P = 0.16) or linoleic (P = 0.32) acid transformed. A trend was identified for cattle fed diets with glycerin to have increased (P = 0.07) grams of conjugated linoleic acid (CLA; C18:2 cis-9, trans-11) per gram of linoleic acid intake, with no impact on the percent of saturated fat (P = 0.44) or unsaturated fat (P = 0.43) in omasal flow. For cattle fed diets with DGS, fewer grams of linoleic (P < 0.01) and linolenic (P < 0.01) were present in digesta flow per gram of intake. Inclusion of DGS in the treatment diets also increased (P < 0.01) stearic acid flow (g) and CLA flow (g) per gram of stearic and linoleic acid intake, respectively. Observed differences in CLA proportion post fermentation may indicate interrupted biohydrogenation when glycerin is fed.

Inclusion of corn grain in cattle diets increases the dietary concentration of unsaturated fatty acids like linoleic acid. Ethanol co-products are most often made from corn grain in the United States and contain concentrated amounts of unsaturated fatty acids. Concerns with feeding ethanol co-products could arise for cattle producers because the increased unsaturated fat concentration of meat products can lead to shorter meat shelf life. Co-products from bio-diesel production, such as crude glycerin, can be used to replace grain and reduce total unsaturated fat without affecting dietary energy. This study evaluated the effect of ruminal microbes to transform unsaturated fatty acids to saturated fatty acids in diets where steam-flaked corn was replaced by co-products such as distillers grains and crude glycerin. When steam-flaked corn is replaced with distillers grains in beef cattle diets, the fat composition was shifted to a higher proportion of saturated fatty acids due to increased biohydrogenation by ruminal microbes. However, feeding crude glycerin in place of steam-flaked corn increased conjugated linoleic acid, an intermediate product of the fatty acid transformation pathway. Increased conjugated linoleic acid indicates glycerin may impact the ability of microbes to transform linoleic acid to a saturated form.