Crude glycerin in steam-flaked corn-based diets for beef cattle

Plant oils contain large amounts of triglycerides that will react to a catalyst, such as methanol. The transesterification reaction between the oil and alcohol will produce approximately 10% crude glycerin and 90% biodiesel. Crude glycerin is distilled for use in human products such as soaps, cosmetics, and moisturizers, but the usefulness of glycerin as a feed source for livestock is unclear. Rapid expansion of the biodiesel industry has created excess supplies of crude glycerin. It is thought that glycerin can be used in ruminant diets to decrease feed costs, but crude glycerin from biodiesel production can contain various levels of methanol, which can be toxic to livestock at increased levels. The purpose of this experiment was to determine the effects of feeding crude glycerin derived from soybean oil in steamflaked corn finishing diets fed to beef cattle.


Introduction
Plant oils contain large amounts of triglycerides that will react to a catalyst, such as methanol.The transesterification reaction between the oil and alcohol will produce approximately 10% crude glycerin and 90% biodiesel.Crude glycerin is distilled for use in human products such as soaps, cosmetics, and moisturizers, but the usefulness of glycerin as a feed source for livestock is unclear.Rapid expansion of the biodiesel industry has created excess supplies of crude glycerin.It is thought that glycerin can be used in ruminant diets to decrease feed costs, but crude glycerin from biodiesel production can contain various levels of methanol, which can be toxic to livestock at increased levels.The purpose of this experiment was to determine the effects of feeding crude glycerin derived from soybean oil in steam-flaked corn finishing diets fed to beef cattle.

Experimental Procedures
In March 2007, 375 crossbred yearling heifers (929.5 ± 63 lbs) were used in a finishing trial.Upon arrival, all cattle were offered ad libitum access to alfalfa hay and water before processing.Within 24 hours of arrival, cattle received injections of Bovishield1 4 and Ultrabac 1 7 vaccines and were treated with internal and external parasiticide.Cattle were implanted with Revalor2 -200 and gradually adapted to a 94% concentrate diet with 6% alfalfa hay (Table 1).Dietary treatments consisted of 0, 2, 4, 8, 12, or 16% crude glycerin (dry matter basis).Cattle were transitioned from the control diet to diets containing increasing proportions of glycerin over a 10-day period.Cattle were blocked by initial weight and randomly assigned within block to each of the six treatments.Three weight blocks were used with six to seven animals per pen and nine pens per treatment.Cattle were housed in 54 concrete-surfaced pens (392.9 ft 2 ) with roofs covering feed bunks and half the pen.Cattle were fed free choice once daily.
On day 85, pens were weighed using a platform scale and shipped to a commercial abattoir in Emporia, KS.At slaughter, hot carcass weight and incidence and severity of liver abscesses were measured.After a 24-hour chill period, USDA yield grade; USDA quality; marbling score; 12th-rib fat thickness; kidney, pelvic, and heart fat; and ribeye area were measured.

Results and Discussion
Glycerin increased average daily gain when added at levels less than 8% of the dry matter diet.Reductions in dry matter intake were observed when glycerin levels increased above 8%.Feeding glycerin at 2, 4, 8, and 12 % of the diet increased feed efficiency by 10.8, 10.0, 7.2, and 3.1%, respectively.Final body weights increased by 28.0, 17.8, and 11.7 pounds when glycerin was added at 2, 4, and 8% of the diet, respectively, but reductions in final body weight occurred when glycerin was fed at the 12 and 16% levels.
Hot carcass weights increased by 17.8, 11.3, and 7.3 pounds when glycerin was fed at 2, 4, and 8% levels, respectively, but were reduced at levels 12% and greater.Longissimus muscle area decreased when glycerin was added to the diet.Feeding glycerin caused reduced subcutaneous fat over the 12th-rib and lower marbling scores.
Lower marbling scores resulted in a 1.3 to 16.4% reduction in the percentage of glycerin-fed cattle grading UDSA Choice.The percentage of glycerin-fed cattle grading USDA Select increased between 0 and 14.8%.Treatment had no effect on percentage of kidney, pelvic, and heart fat or the percentage of liver abscesses.

Implications
Adding glycerin at 2 to 8% of the steamflaked, corn-based finishing diet improved weight gains and efficiency, but higher levels appear detrimental.Alfalfa hay 5.9 5.9 5.9 5.9 5.9 5.9