Discipline: silage inoculants; Keywords: corn silage, heterolactic bacteria, Lactobacillus buchneri, Lactobacillus hilgardii
Silage is an integral component of most dairy cow diets and research has primarily focused on improvement of silage quality and minimizing nutrient losses during ensiling. Silage inoculants have been the most commonly used additive for improving quality. Previous research results have shown that inoculation with homolactic and facultative heterolactic lactic acid bacteria (LAB) improved the fermentation of grass and legume silages and the performance of dairy cows but did not affect the fermentation of whole-plant maize, whole-plant sorghum, and sugarcane silages or aerobic stability of the silages. This research only focused on inoculants for improving silage fermentation; hence, it intentionally excluded obligate heterolactic LAB that are added to improve aerobic stability. To avoid or reduce DM losses and to enhance fermentation simultaneously, several inoculants now contain a mixture of homolactic or facultative heterolactic bacteria with obligate heterolactic bacteria. By combining homolactic bacteria with LB improved aerobic stability without affecting DM losses.
Concerns have been expressed that inoculating forages with LB and the associated increase in acetate concentration may reduce feed intake in dairy cows. However, this has not been consistently supported. Several studies reported that LB did not affect intake or milk yield, whereas others reported an increase in milk yield. The objective therefore of the study by Dr K.G. Arriola and co-workers was to examine the effects of inoculation with LB-based bacteria (LBB), including LB alone or LB with homolactic or obligate heterolactic LAB, on silage fermentation, aerobic stability, and animal performance. They hypothesized that LBB inoculants would improve silage quality, aerobic stability, and milk yield but no effects would be observed on DMI. The results were published in the Journal of Dairy Science, Volume 104 of 2021, page 7653 to 7670, the title being: Meta-analysis of effects of inoculation with Lactobacillus buchneri, with or without other bacteria, on silage fermentation, aerobic stability, and performance of dairy cows.
A meta-analysis of 158 peer-reviewed articles was conducted to examine the effects of inoculation with Lactobacillus buchneri (LB)-based inoculants (LBB) that did or did not include homolactic or obligate heterolactic bacteria on silage fermentation and aerobic stability. A complementary meta-analysis of 12 articles examined LBB inoculation effects on dairy cow performance. The mean differences between inoculant and control treatment were compared with variance analysis. Meta-regression and sub-grouping analysis were used to identify effects of forage type, application rate (less or equal to 104, 105, 106, or more than 107 cfu per g as fed), bacteria type (LB vs. LB plus other bacteria), enzyme inclusion, ensiling duration, and silo type (laboratory or farm scale).
Inoculation with LBB increased acetate (62%), 1, 2 propanediol (364%) and propionate (30%) concentration and aerobic stability (73.8%), and reduced lactate concentration (7.2%), yeast counts (7-fold) and mold counts (3-fold). Feeding inoculated silage did not affect milk yield, dry matter intake, and feed efficiency in lactating dairy cows. However, forage type, inoculants composition, and dose effects on silage quality measures were evident. Inoculation with LBB increased aerobic stability of all silages except tropical grasses. Adding obligate homolactic or facultative heterolactic bacteria to LB prevented the small increase in DM losses caused by LB alone. The 105 and 106 cfu per g rates were most effective at minimizing DM losses where aerobic stability was only increased with the 105,106, and more than 107 cfu per g rates.
In summary the results showed that silage inoculation with LBB increased aerobic stability due to greater acetate concentration and lower yeast counts for all inoculant combinations, rates of inoculation, and forage types except tropical forages. Aerobic stability was improved by LBB inoculation at all ensiling durations examined but was greater with more than 90 days of ensiling. The DM losses with LBB inoculation were generally small and were forage, inoculants composition, and dose specific. Adding other bacteria to LB prevented the small loss in DM caused by LB alone. The best application rates for preventing DM losses, increasing acetate concentrations, reducing yeast counts and increasing aerobic stability were 105 and 106 cfu per g fresh forage. Feeding LBB-inoculated silage had no effects on DMI, DM digestibility, and feed efficiency in cows.