Evaluation of Yeast Product Additives in Cattle Feedlot Diets

Conducted for:
Western Yeast Company
305 W. Ash Street P.O. Box 257 Chillicothe, IL 61523-0257

Apr. 26, 2001 - Aug. 2, 2001
Yeast Product Additives in Cattle Feedlot Diets

Dr. John Carlson, Principal Investigator
Agriculture Department 310 Knoblauch
Western Illinois University
Macomb, IL 61455
309/298-1611

Trial Procedure

Seventy-two crossbred steers were purchased from a commercial feedlot cattle supplier and delivered to the Western Illinois University farm on April 13. Upon arrival they were sorted into 6 pens of 12 head each and all were fed a commercial feedlot ration based on shelled corn, pelleted soybean hulls and hay for their acclimation period. On April 26, all steers were weighed and assigned to one of six pens so that the average weight of each pen was within 1% of the overall mean. The mean weight on April 26 was 881.8 pounds, and the mean pen weights, with their assigned treatment are as follows:

Pen 1	– control	873.4
Pen 2	– control	884.2
Pen 3	– 15 pounds/ton of 2X-2-2-5(Y15)	887.0
Pen 4	– 25 pounds/ton of 2X-2-2-5(Y25)	887.0
Pen 5	– 10 pounds per ton of 2X-2-2-5PLUS(Y+10)	873.7
Pen 6	– 15 pounds per ton of 2X-2-2-5PLUS(Y+15)	885.3

The control ration was the same ration which was fed during the acclimation period, and the treatment rations were the control ration adjusted for the particular yeast product addition. Individual daily feed consumption was recorded with a Pinpointer unit. All animals were weighed again on June 25 for a 60-day period evaluation, and the test was concluded on August 2 with another weighing of all animals.

Results

All data was analyzed using the SPSS statistical package. Printouts from all analyses are included with this report. All 72 steers were included in the initial weight and 60-day weight analyses. However, for the analyses of overall performance and for the last 38 days of the trial, records on only 70 animals were used. Two animals were excluded from the data as their performance was statistically evaluated to be outside the normal range of performance. For the 60-day period, 38-day period, and overall testing period, the traits analyzed were average daily feed consumption, average daily gain, and feed efficiency, measured as pounds of feed required per pound of gain. The model used consisted of the mean, treatment group, plus the residual error. Individual mean comparisons were conducted among the treatment means using the Least Significant Difference procedure.

            a) control vs. yeast groups
               b) Y15 and Y25 vs. Y+10 and Y+15
            c) Y15 vs. Y25
               d) Y+10 vs. Y+15

Initial Weight

Initial weight of the animals was analyzed to verify that there was no difference between groups for initial weight. As expected, differences between pens for initial weight was not significant.

60-day results

Feed consumption was not significant during the first 60 days of the trial. The means (pounds of feed consumed per head per day) for each of the five groups are:

Control	27.74
Y+10	29.13
Y+15	26.87
Y15	29.57
Y25	29.72

Average daily gain was significantly different between the treatment groups for the first 60 days. The means (pounds of weight gain per day) are shown below.

Control	3.784
Y+10	4.417
Y+15	3.603
Y15	4.083
Y25	4.133

Steers on the Y+10 ration gained significantly faster than did the control steers(P=.017). However, the other yeast-based groups did not have significantly faster gains than did the controls. The Y+10 group mean was also significantly (P=.008) higher than was the Y+15 group mean. The Y25 group also gained significantly faster than did the Y+15 group(p=.08).

Feed efficiency was not significantly different between the groups for the first 60 days. The group means are:

Control	7.583
Y+10	6.712
Y+15	7.586
Y15	7.420
Y25	7.228

38-day results

Feed consumption, average daily gain and feed efficiency were not significant for the final 38 days of the trial. The means for each of the treatment groups are:

Group	Feed Cons.	Avg. Daily Gain	Feed Effic.
Control	27.446	2.443	12.638
Y+10	26.954	2.763	10.179
Y+15	25.553	2.456	10.726
Y15	27.515	2.193	14.318
Y25	27.932	2.737	13.698

Overall results

Over the entire trial, feed consumption was not significantly different between any of the groups. The means for each group overall are:

Control	27.626
Y+10	28.285
Y+15	26.359
Y15	28.772
Y25	28.914

Average daily gain, however, was significantly different (P=.02) between groups. The means are listed below:

Control	3.246
Y+10	3.776
Y+15	3.158
Y15	3.350
Y25	3.565

The Y+10 animals grew significantly faster than did the controls and faster than did the Y+15 group and the Y15 group. Animals fed the Y25 ration grew significantly faster than did animals fed the Y+15 ration.

Feed efficiency was also significantly different between groups,
as shown in the means below:

Control	8.586
Y+10	7.566
Y+15	8.424
Y15	8.621
Y25	8.256

The Y+10 animals were significantly more efficient than all groups except the Y25 group.

Summary

Based on the results of this trial, the Y+10 supplement appears to be the far superior additive, as evidenced by its ability to increase daily growth rate for the first 60 days of the trial, plus over the entire trial period, as well as promoting better feed efficiency over the entire trial period. The Y25 additive appears to be the second-best additive, as it was superior in several instances to the Y+15 product.

Several questions are raised through this trial's results, however. The most obvious question is why the Y+15 product did not give better performance when the Y+10 product promoted faster growth and better feed efficiency. It would seem that if the Y+10 was good, than the Y+15 should be better. However, this did not occur. It would be interesting to conduct another trial comparing the Y+ 10 with the Y+15 feed, with either a control ration or Y25 ration included, and two pens of each treatment.