Factors affecting the aerobic stability of corn silage-based total mixed rations
Date
2023
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Publisher
University of Delaware
Abstract
Corn silage based total mixed ration is widely used on farms but is susceptible to aerobic deterioration. The objective of this dissertation was to evaluate factors that could affect the aerobic stability of TMR and possible solutions that can be used to extend the TMR stability in feed bunk. Several experiments were conducted to achieve this objective. The effects of TMR ingredients from different farms, chemical additives, and their interact effect were evaluated (Experiment 1, Chapter 3). The chemical additives (a mixture of sodium benzoate, potassium sorbate, and sodium nitrite added at corn silage ensiling or potassium sorbate added after corn silage fermentation) improved the aerobic stability of corn silage even if their effects on yeasts were different. However, this beneficial effect on aerobic stability did not show in the consequential TMR. This observation was probably because of the relatively high pH of all TMRs (4.7-5.0), which decreased the undissociated acids with antifungal properties. The TMR mixed with feeds from Farm 1 had slightly better aerobic stability, which might be due to the less complex TMR formulation. We also observed a negative correlation between pH and aerobic stability of TMR. Controlling TMR pH might help to control TMR aerobic stability. The effect of rate of spoiled silage inclusion, a chemical additive, and their interact effect were evaluated (Experiment 2, Chapter 4). Corn silage is prone to spoil in silo because of inadequate management, high ambient temperature, or air leakage during ensiling. Molds show on the surface of “heavily spoiled” silage and help farmers recognize and discard. However, “slightly spoiled” silage is hard to be noticed and easy to be mixed into the TMR. Hence, we conducted a preliminary study to decide the degree of spoilage of the corn silage, which had 2.7 log10 cfu/g (wet basis) more yeasts and ~8°C of temperature increase. Substituting fresh corn silage with even 10% (as-fed basis) of spoiled corn silage increased yeasts counts, the heating rate, the heat produced after aerobic exposure (showed by AUC) and decreased the aerobic stability of TMR. The effect was more significant when 30% (as-fed basis) of fresh corn silage was replaced by spoiled silage. Yeasts might be the reason of these observations because a negative correlation between yeasts and aerobic stability and a positive correlation between yeasts and AUC were documented. Treating the corn silage with a chemical additive at ensiling increased the aerobic stability by 4 h (29 vs. 33 h) and decreased AUC (7827 vs. 7668). However, it is doubtable if this improvement makes a difference in the practical world. The dose effect of TMR-saver (TMR-S) on TMR sampled from multiple farms (Experiment 3, Chapter 5) and the interact effect of TMR- S and temperature (Experiment 4, Chapter 5) were evaluated. Applying the TMR-S caused linear decreased in number of aerobic bacteria, yeasts, and improvements in aerobic stability compared to untreated TMR. Only treatment with TS35 resulted aerobic stability of the TMR higher than 24 h. Numbers of yeasts were greater in TMR sampled in warm vs. cool weather, and a trend of more aerobic bacteria showed as well. TMR was stable for 27 h when sampled under cool weather, but it spoiled after 17 h when sampled under warm weather.
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Keywords
Aerobic stability, Chemical additives, Corn silage, TMR-saver, Total mixed rations