Masters Theses

Date of Award

12-1981

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

K. M. Barth

Committee Members

J. B. McLaren, C. C. Chamberlain

Abstract

The effects of corn silage fermentation aids on dry matter recovery of silage, performance, and subsequent carcass data of beef heifers fed the silages and nutrient digestibility of the silages by wethers were determined in this study. Corn green chop in the late dough to early dent stage was harvested during August of 1979 and 1980. For each year, two silos were assigned to one of four silage treatments with or without fermentation aids added. The four experimental corn silage treatments were: (1) an untreated control silage; (2) treated with Silabac, a live lactobacillus preparation; (3) treated with Culbac, a dead lactobacillus preparation; and (4) treated with Crop Cure, sodium diacetate. Samples of the ensiled materials were taken for later determination of dry matter recovery. The ensiled materials were allowed to ferment for approximately 140 to 150 days before the first silo of each treatment was opened. Fresh silage samples were taken during both years when the silos were opened and at 28-day intervals thereafter. In addition, a sample of spoiled silage was taken from one silo of each treatment in 1980. These samples were taken in order to determine the dry matter recovery and nutrient composition of each treatment. In the fall of 1979 and 1980, Angus beef heifer calves were purchased during the Tennessee fall feeder calf sales. In mid-December of each year heifers were allotted, using several parameters, to eight groups of five animals each, two groups per treatment, with the effort being made to have maximum equality of all parameters. Two feedlot trials, designated as the 1979-80 trial and the 1980-81 trial, were then begun. These trials were partitioned into two phases-- the silage-feeding phase and the full-feeding phase. At approximately 28-day intervals throughout each phase and at the end of each phase body weights were taken. Utilizing these weights and the feed intakes of the heifers during these intervals, the gains and feed efficiencies of the heifers of each treatment were calculated. Backfat thicknesses of the heifers were measured using a somoscope prior to the beginning of the silage-feeding phase and at the end of the silage-feeding phase. Backfat was also measured during the full-feeding phase, initially at four-week intervals and later at two-week intervals as heifers approached 12 mm backfat thickness, which was predetermined as the criterion to send each heifer to slaughter. Backfat thickness data were also studied to determine if there were any treatment effects. After chilling the carcasses of the slaughtered heifers for 48 hours, several carcass parameters were either measured or calculated and the data compared to determine possible treatment effects. A total collection digestion trial was conducted concurrently with the 1979-80 feedlot trial. Some silage from one of the silos of each treatment was removed, stored, and then fed to mature wethers averaging 74.5 kg in body weight. Nutrient digestibility of the corn silage treatments by the wethers were determined and compared. Two-year means of the dry matter recoveries of each treatment were not significantly different (P>.G6); however, the statistical analyses were considered to be inconclusive due to a low number of replicates. The dry matter recovery after ensiling losses, after spoilage losses, and total dry matter recovery for each corn silage treatment, respectively, were 88.3, 94.7, and 83.1% for the control; 89.3, 95.4, and 84.7% for Silabac; 94.9, 96.3, and 91.2% for Culbac; and 91.9, 93.3, and 85.2% for Crop Cure. It appears that, except for the Culbac-treated corn silage, addition of fermentation aids had little effect on improvement of dry matter recovery. The nutrient composition of the corn silage treatments of the 1979-80 trial was similar among treatments for all constituents. In the 1980-81 trial, silages with additives were lower (P<.01) in dry matter as compared to the control. All other constituents, except lignin, were not different (P>.05) among treatments. The Silabac-treated silage was higher (P<.05) and the Crop Cure-treated silage was lower (P<.05) in lignin content than the control, the reason for which is not understood. Fermentation aids added to the corn silages during ensiling did not significantly affect (P>.05) intake, gain, or feed efficiencies of the slaughter beef heifers as compared to the control during the silage-feeding phase. Also, there were no significant (P>.05) treatment effects in intake, gain, or feed efficiencies during the full-feeding phase. There were no significant differences (P>.05) among treatments for two-year means of any of the backfat thicknesses, which were measured at various times, or for any of the carcass parameters, except for fat thickness and yield grades. Silabac and Culbac treatment backfat thicknesses and yield grades were found to be significantly lower (P<.05) than the control and Crop Cure treatments. Differences in fat thicknesses may have been due to changes in acetate levels in the silages due to the addition of fermentation aids and subsequent change in the rumen acetate levels of the heifers. Yield grade differences were probably a function of the fat thickness differences. In the total collection digestion trial, wethers fed the fermentation aid-treated silages consumed significantly less (P<.05) dry matter than wethers fed the control. No significant differences (P>.05) were found among rations in apparent nutrient digestion coefficients for any of the nutrient constituents except for those of crude protein and ether extract. Differences in ether extract digestibilities were considered inconclusive due to low ether extract contents in the rations. Crude protein digestibilities by wethers were depressed significantly (P<.05) in the Culbac- and Crop Cure-treated rations as compared to the control and Silabac-treated rations. Wethers offered the Crop Cure-treated ration had lower crude protein digestibility which was attributed to a low crude protein percentage in the ration and an increased acid-detergent fiber nitrogen percentage as compared to the other rations. compared to the other rations. Depression of crude protein digestibility by Culbac addition could not be explained.

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