The effect of inoculants on silage fermentation properties and on animal production

[摘要] ENGLISH ABSTRACT: Maize, forage sorghum, lucerne, oats, barley and triticale are the most common silage crops inSouth Africa, while tropical grasses like Eragrostis curvula and Digitaria eriantha are ensiledto a lesser extent. The aim of this study was to determine the effect of adding a lactic acidbacterial inoculant to E. curvula, D. eriantha, lucerne, forage sorghum, maize and oat silage.The effect of the addition of a lactic acid bacterial inoculant when ensiling E. curvula on thefermentation dynamics during ensiling and the aerobic stability of the silage was determined. Theaddition of the lactic acid bacterial inoculant to E. curvula at ensiling resulted in a more rapidlowering in pH and improved preservation. Inoculated silage had a higher lactic acid content, lessprotein breakdown and a lower butyric acid content compared to that of the control silage. Bothsilages were stable when exposed to air for five days.Digitaria eriantha was ensiled, with or without the addition of a lactic acid bacterial inoculantcontaining Lactobacillus plantarum. Streptococcus faecium and Pediococcus acidilacticitogether with the enzymes, cellulase, hemicellulase and amylase. The addition of the inoculantresulted in a more rapid drop in pH, a higher level of lactic acid, an increase in the number oflactic acid bacteria, less protein breakdown and lower numbers of enterobacteria, clostridialspores, yeast and mould compared to the control silage. Digitaria eriantha hay, control andinoculated silage diets were fed to 24 Merino rams (n = 8 per treatment) to determine intake anddigestibility. The intake of diets consisting of 90.9% D. eriantha hay, control silage or inoculatedsilage, differed significantly (p<0.05) at 1395, 1540 and 1848 g DM/day, respectively. The in vivo organic matter digestibility (glkg) of D. eriantha hay, untreated silage and inoculated silagediets was 561, 546, 574, respectively. The addition of the bacterial inoculant when ensiling D.eriantha resulted in better preservation, improved aerobic stability, as well as a higher in vivoorganic matter digestibility and intake of D. eriantha silage.The addition of an inoculant or molasses to lucerne (Medicago sativa), ensiled in laboratory siloswas investigated. The addition of the additives resulted in an increased preservation rate asindicated by a more rapid lowering of pH, a faster rate of lactic acid production and less proteinbreakdown compared to control silage. The inoculant was more effective than the molasses inimproving the rate of preservation. The aerobic stability of lucerne silage was not affected byinoculation or the addition of molasses. The addition of an inoculant to wilted big bale lucernesilage was studied. The inoculant improved silage quality as indicated by a lower pH, higherlactic acid content, lower ammonia nitrogen content and lower level of butyric acid in inoculatedsilage compared to the control lucerne silage. The composition of big round bale lucerne silagediffered markedly from that of lucerne ensiled in laboratory silos as the former had a higher pH,ammonia nitrogen, butyric acid and acetic acid content and a lower lactic content.Whole crop forage sorghum cultivar FS2 was harvested at the late bloom (20.7% DM) and softdough (28.9% DM) stages of maturity and ensiled in laboratory silos with the additionof commercial silage inoculants. At both stages of maturity the inoculants caused a more rapid rateof pH decline and a higher amount of lactic acid production. All the silages were well preserved.Silages of the sorghum ensiled at the late bloom stage with all treatments were stable after 5 daysof aerobic exposure, whereas sorghum ensiled at the soft dough stage with the addition of theinoculants deteriorated upon aerobic exposure. It is concluded that addition of lactic acidbacterial inoculants to mature sorghum at ensiling might impair the aerobic stability of the silage.The yield, nutritional value and production potential of silage made from twenty one maizehybrids was compared. It was concluded that maize hybrids did differ in metabolizable energycontent, rate of digestion, predicted intake and predicted milk production potential. The contentof NDF and ADF did not differ between the maize hybrids used in this study and could thereforenot be used to predict nutritional value or production potential.Maize was harvested at the hard dough stage and ensiled with or without the addition of a lacticacid bacterial inoculant in laboratory silos and in 210 litre drums. The adding of the inoculantto maize at ensiling did not result in a more rapid drop in pH and higher levels of lactic acid. Theintake and growth of South African Mutton Merino lambs fed inoculated and untreated maizesilage diets was determined. The average daily gain of lambs fed a diet consisting of either 60%control or inoculated maize silage over a growth period of 60 days was 239 ± 26 and 255 ± 44g/day, respectively. Although the laboratory study showed very little effect of adding a lactic acid bacterial inoculant to maize at ensiling, lambs tended to consume more of the inoculated silage.In the second study the effect of the addition of a lactic acid bacterial inoculant with an enzymeto maize at ensiling on the fermentation dynamics during ensiling, aerobic stability of the silage,the intake, milk production and milk composition of Jersey cows fed maize silage diets wasdetermined. The inoculant did not result in a more rapid lowering of the pH or a more rapidlactic acid production compared to untreated maize silage made in laboratory silos. Both thecontrol and inoculated maize silages were well preserved. The addition of the inoculant to maizeat ensiling improved the palatability, intake and the aerobic stability of maize silage comparedto the untreated control maize silage. Milk production, milk composition, live weight andcondition score of Jersey cows was not significantly affected by the addition of the inoculant tomaize silage.The effect of the addition of an enzyme containing lactic acid bacterial inoculant to big baleoat (Avena sativa, cv Cederberg) silage on silage composition, silage intake, milk production andmilk composition of Jersey cows was determined. The crop was cut at the bloom stage, wiltedand ensiled in big round bales. The inoculant, Sil-All, was applied during the baling process onhalf of the bales. Silages were fed to Jersey cows in an intake and milk production study. Boththe control and inoculated oat silages were well preserved. The inoculated oat silage had a lowerlevel of butyric acid than the control oat silage. Cows fed the inoculated oat silage producedmore (P=O.05) milk (17.7 kg/day) than cows fed the control oat silage (16.7 kg/day). Theaddition of a lactic acid bacterial inoculant to big bale oat silage improved silage compositionand animal performance.This study clearly showed that the composition of silages made in bunker silos undercommercial farm conditions differ largely from that of silages made in small scale laboratorysilos. When the effect of silage additives on aerobic stability of silage is determined theevaluation should include studies on large scale bunker silages. Evaluation of silage additivesshould include intake and animal production studies.

[发布机构] Stellenbosch University