OBT DIET CHANGED in 1998-99 - Francis Fluharty, OSU Research Scientist, OARDC, Wooster
The diet fed to the bulls was changed because corn cobs were no longer a viable feed ingredient. Over the past few years, corn cobs have become increasingly expensive due to their use as an industrial polisher. The diet was changed to eliminate corn cobs, reduce the amount of oats and soybean meal, and add alfalfa meal, beet pulp, and soybean hulls as sources of dietary fiber. The use of more alfalfa meal allowed for less soybean meal. As a result, the diet cost was lowered without decreasing performance potential.
Bull Test Diet Comparison
| Ingredient | 1997-98, % of DM basis | 1998-99, % on DM basis |
| Corn (whole) | 38 | 38 |
| Oats | 25 (rolled) | 10 (whole) |
| Corn Cobs | 10 | 0 |
| Alfalfa Meal (17%) | 10 | 20.9 |
| Wheat Middlings | 5 | 13.7 |
| Beet Pulp | 0 | 3.7 |
| Soybean Hulls | 0 | 6.4 |
| Soybean Meal (44%) | 10 | 5 |
| Dicalcium Phosphate | .5 | .36 |
| Limestone | .7 | .6 |
| T.M. Salt | .5 | .5 |
| Selenium | (.3 ppm) | (.3 ppm) |
| Sodium Bentonite | .3 | .3 |
| Nutrient Composition of concentrate portion | ||
| TDN,% | 68.5 | 70.7 |
| Protein,% | 13.7 | 13.5 |
Note: Both diets contained additional Vitamin A, D, and E, and Rumensin. Also, bulls received
approximately 2-4 pounds of mixed hay per bull per day.
Comparison of Fat Thickness of Angus Bulls
| Fat Thickness, inches | 1998, % of Angus bulls | 1999, % of Angus bulls |
| less than .20 | 7.9 | 6.9 |
| .21 to .25 | 10.8 | 8.6 |
| .26 to .30 | 19.6 | 15.5 |
| .31 to .35 | 14.7 | 24.1 |
| .36 to .40 | 18.6 | 17.2 |
| .41 to .45 | 13.7 | 8.6 |
| .41 to .45 | 13.7 | 8.6 |
| .46 to .50 | 9.8 | 8.6 |
| .51 to .55 | 2.9 | 6.9 |
| .56 to .60 | 0.0 | 3.4 |
| .61 to .65 | 1.0 | 0.0 |
| .66 to .70 | 1.0 | 0.0 |
A comparison of the distribution of backfat thicknesses of the Angus bulls ultrasounded in 1998 and 1999 shows that the diet change did not negatively affect the bulls by increasing the overall fat thickness. Angus bulls were chosen, because they had the largest number of individual animals within a breed group and would, therefore, give the most accurate assessment. However, caution must be used in assessing these differences, since the genetics and number of animals differ from year-to-year as does the environmental weather conditions.
It is important not to have bulls carrying excess fat when they enter the breeding season, because
excess body fat results in excess fat in the scrotum, which decreases the amount of heat that can
be radiated from the testes. If the temperature of the testes becomes too high, the percentage of
morphologically normal sperm is reduced, as is sperm motility (Coulter et al., 1997). Both of
these factors reduce reproductive capability.
Coulter, G. H., R. B. Cook, and J. P. Kastelic. 1997. Effects of dietary energy on scrotal surface temperature, seminal quality, and sperm production in young beef bulls. Journal of Animal Science. 57:1048-1052.