Corn Silage InoculantsReview Gbola Adesogan Department of Animal Sciences IFAS, University of Florida Outline Silage fermentation process Chemical additives – Organic acid additives – Ammonia (urea) Inoculants – Definition – Roles – Types – Effectiveness Take home messages Chemical changes during fermentation 1. Anaerobic bacteria ferment sugars to volatile acids • e.g. lactic, acetic & butyric acids 2. Acids pickle the forage and inhibit undesirable microbes 3. Protein is partially degraded into ammonia 4. These processes can cause DM losses (effluent / seepage) Sugars Chemical changes during fermentation Pickling / fermentation of the forage Days 21 CP Lactate Ammonia Acetic acid Butyric acid 20 15 10 5 Scale (%) 1 pH CROP SILAGE Fermentation pathways Product Nutrient Losses Substrate (Microbe) Fermentation 2 x Lactic acid (Low pH) Low Glucose (L. plantarum) Homo- fermentative 1 x Lactic & acetic acids, ethanol & CO 2 (Moderate pH) Moderate Glucose (L. buchneri) Hetero- fermentative V. high Ethanol, CO 2 Glucose, lactic acid (Yeasts & molds) Aerobic spoilage Butyric acid + CO 2 (High pH) High Lactic acid (Clostridia) Secondary fermentation Organic acids Role – Rapidly reduce pH; hence inhibit undesirable microbes – Antifungal – hence enhance aerobic stability Types – Pure acids e.g. formic, propionic, acetic & benzoic acids. • Effective but caustic & hazardous – Buffered organic acids – Ca & Na salts of pure acids • Less caustic & safer to handle Ammonia (urea) Role – Alkaline and antifungal in nature – Improves aerobic stability – Contributes CP Concerns – Narrow harvest window • If < 60% moisture – volatilization • If >70% moisture – N loss in effluent – May hinder fermentation & increase DM losses – V. caustic, protective clothing required – Ammonia poisoning Inoculants Definition Additives containing bacteria selected to grow quickly and dominate the bacterial population in the silage Types 1. Traditional (homofermentative) inoculants • e.g. Lactobacillus plantarum • lactic acid & pH, acetic & butyric acids • losses of DM (1-3%), sugar and protein • May increase fiber digestion & animal performance (3-5%) 2. Newer inoculants (heterofermentative) – Aerobic stability enhancers – e.g. L. buchneri Effectiveness of inoculants 0 20 40 60 (Muck & Kung, 1997) n = 221 233 148 34 39 82 35 Effectiveness of inoculants in different silages Fermentation 60% Intake 28% Gain 53% Milk production 47% (Muck, 2002) Effectiveness of inoculants in different silages % t r i a l s w i t h l o w e r p H 0 20 40 60 Alfalfa Grass Corn Sm. Grain (Muck and Kung, 1997) Epiphytic bacteria on Standing Crops 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 C o r n P . R y e g r a s s R y e g r a s s H . R y e g r a s s A l f a l f a Homoferm. Heteroferm. Entero (Andrieu & Gouet, 1990) Contrasting views on inoculants “Results from over 200 laboratory-scale silo studies, indicated bacterial inoculants were beneficial in over 90% of the trials. A good-quality, effective inoculant should be applied to every load of forage ensiled!” (Bolsen, 1997) Reviewed corn silage inoculants articles for 5 years “We don’t see enough benefits to recommend inoculants for corn silage” (Muck, 2001) Forage factors affecting inoculant action Forage epiphytic microbial population Forage sugar content Forage buffering capacity Forage maturity stage Forage hybrid / variety Inoculant factors affecting inoculant action Bacteria strain and composition Bacteria viability Inoculant application rate – > 100,000 live bacteria (cfu)/g or > 90 billion bacteria / ton Inoculant form – Liquid inoculants act faster & more evenly distributed – Must use within 24h & inactivated by chlorinated water All inoculants are not created equal Fermentation enhancement when epiphytic bacteria are compromised - – Immediately after frost – Dry crop – Immature crop Use traditional homofermentative inoculants Aerobic stability enhancement – Homofermentative inoculants reduce acetate and propionate, hence are less effective Use L. buchneri (heterofermentative) Inoculants are most effective for corn silage for: QUESTION: Does anyone know if I can re-bag corn silage? We need more pavement and the bag is in the way. Would it work better to put it in a bunker silo? ANSWERS 1. “No problemo re-bagging. Would very much recommend it”. 1. “We rebagged some corn silage two years ago and were left with a horrible pile of garbage. The excellent corn silage had become inedible. Right now we're using it as part of our compost program”. Bunk /Aerobic spoilage More prevalent in corn & small grain silages Can cause < 50% of losses in silage DM Spoilage of the top 1m = $500 to $2500 (Bolsen, 1997) Causes – Air entry into good silage – Air pockets in poor silage – Untidy silo faces – Slow feedout Effects – Reduce intake – Reduce nutritive value – Produce mycotoxins Effect of inoculants on aerobic stability of corn silage (Ranjit & Kung, 2000) Inoculant Application rate (cfu/g) Acronym Control 0 Control Lactobacillus buchneri 100,000 LB Mod Lactobacillus buchneri 1,000,000 LB High Lactobacillus plantarum 1 1,000,000 LP 1 Lactobacillus plantarum 2 1,000,000 LP 2 Storage-mate NA Store-mate Effect of inoculants on composition 0 2.5 5 7.5 10 Acetate Lactate WSC (sugars) % D M C o n t r o l L B x M o d L B x H i g h L P - 1 L P - 2 S t o r e - m a t e Yeasts (log 10 cfu) Effect of inoculants on aerobic stability A e r o b i c s t a b i l i t y ( h o u r s ) 27 36 >900 32.8 33 38 C o n t r o l L B x M o d L B x H i g h L P - 1 L P - 2 S t o r e - m a t e (Ranjit & Kung, 2000) L. Buchneri Summary Benefits – Enhanced aerobic stability – No adverse effects on intake (observed so far) Limitations – More nutrient losses than homofermentative inoculants Future work – Combining front (homofermentative) & back end (heterofermentative) inoculants Silage Additive Regulators Countries with pre-market screening of additives UK UKASTA Canada Ag. Canada USA None Take Home Messages Only use inoculants with – Independent research-attested track record – >90 billion live bacteria / ton – L. plantarum for fermentation enhancement – L. buchneri for bunk life enhancement – Don’t choose by cost (35 cents to $1 per ton) – Use only corn silage inoculants for corn silage – Apply at chopper, not into wagon or at bunker – Store in a cool, dry place – Once diluted, use within 24 h. “Silage producers have long recognized the positive effects of using an inoculant to insure the proper transformation of forage into a palatable and digestible feedstuff” Recent quote: Beware, inoculants are useful but they are neither: A substitute for bad management magic potions Take Home Messages Harvest promptly – (35%DM or 1/3-2/3 milk line) Sharp knives, chop length Unprocessed (1/4 –3/8 inch) Processed (3/4 inch) Take Home Messages Fill bunker promptly Pack, pack and pack again Seal immediately & properly + tires Take Home Messages Manage the silo face – Feedout quickly (6 inches/day) – The narrower the bunker, the better – Minimal disturbance – Heat loss = production volatilized Questions Effect of delayed sealing on fermentation (Uriate et al., 2001) Day Control Additive-treated Control Immediate seal Delayed (48h) seal 0h seal Delayed (48h) seal pH at opening 3.7 3.7 3.5 3.6 pH 4 days later 3.6 8.0 3.7 8.2 Lactic acid at opening (% DM) 4.5 4.9 4.1 4.5 Lactic acid 4 days later 4.4 0.3 3.9 1.5 Effect of delayed sealing on stability & yeasts (Uriate et al., 2001) Day Control Additive-treated Control Immediate seal Delayed (48h) seal 0h seal Delayed (48h) seal Lactate utilizing Yeasts at opening 4.9 5.7 5.0 5.5 Lactate utilizing Yeasts 4 days later 8.2 9.4 9.0 8.7 Aerobic stability (hours) 113 65 137 89 Ensiling losses- Source % Net Energy lost Respiration 1-2 Wilting 2-5 Heterofermentative bacteria 4 Secondary Fermentation 0-5 Effluent 5-7 Aerobic spoilage in the silo 0-10 Aerobic spoilage at feedout 0-15 (McDonalds et al., 1991) How does buchneri work Uses heterolactic fermentation – – More acetate produced – Acetate is an anti-fungal agent – Inhibits-spoilage causing yeasts & moulds Disadvantages of heterolactic fermentation – Depressed lactate production & higher nutrient losses – Depression in intake if excess acetate is produced Effect of temperature on corn silage pH 37 O C 28 O C Target pH (Weinberg et al., 2001) Effect of temperature on corn silage pH Inoc, 24 O C Control 24 O C Inoc, 41 O C (Weinberg et al., 2001) Inoculated silages may spoil more than respective control silages at high temperatures which inhibit the growth of inoculant bacteria. Special care should be taken during silage making and unloading in warm climates Florida corn silage producers must do better than average. Temperature matters! Fermentation vs. stability Traditional view – Conventional inoculants (homofermentative) enhance fermentation but often reduce bunk life • Cause = Reduced acetic & propionic acid Emerging view – L. buchneri (heterofermentative) inoculants can improve bunk life