Fermentation, stability and degradability of whole-crop oat silage ensiled with a commercial inoculant

Pienaar, Johanni (Stellenbosch : Stellenbosch University, 2010-03)

Abstract

ENGLISH ABSTRACT: South Africa is well-known for periodic dry periods and uncertain rainfall. Ensiling of crops is a method of preserving forage and ensures feed availability during periods when the supply of good quality forage is low. Cereal-based silages, especially in the Western Cape, South Africa, represent a significant proportion of feed consumed by ruminant animals, particularly high-producyion dairy cattle. However, farmers are still concerned about the technical challenges of ensiling cereal crops. Previous research done on lactic acid bacteria (LAB) inoculants used on cereal based silage has indicated a potential for improving silage fermentation, stability and degradability, thus enhancing feed conversion and production by ruminants. Two experiments were conducted to determine the effects of inoculating whole-crop oat silage with Lalsil® Cereal Lactobacilli (Lactobacillus buchneri (NCIMB 40788) and Pediococcus acidilactici (CNCM MA 18/5M)) LAB on (1) silage fermentation, (2) aerobic stability and (3) nutritional value of silage ensiled under a. micro-silos conditions and b. in a bunker under outdoor conditions of a Mediterranean summer. Oats (Avena sativa, cv SSH 405) were planted on 60 ha under dryland conditions at Elsenburg in the Western Cape province, South Africa. Whole-crop oats were harvested at the soft dough stage and length of the chopped material was 9 mm (Day of ensiling – Day 0). Chopped whole-crop oats were sampled, mixed thoroughly and divided into two portions. The Inoculant (Lalsil® Cereal) was applied to one portion to provide 5.79 x 109 colony forming units (CFU) of LAB per gram of fresh material. In the first experiment twenty - four glass silos (1.5 L glass jars) (WECK, GmbH u.Co., Wehr-Ofligen, W. Germany) were filled for each of the control and inoculant treatments. The glass silos were stored in a dark room in the laboratory at ambient temperature. Three glass silos were opened for each treatment on days 1, 2, 4, 8, 15, 30, 60 and 102 post-ensiling to determine fermentation dynamics. A parallel study was done with the same chopped whole-crop oats using the buried bag technique in a bunker silo. Whole-crop oats were ensiled in six net bags per treatment buried in a bunker filled with the same untreated whole crop oats. Bags, attached with nylon lines (3 m lengths) for easy retrieval were buried at 1m and 2 m depths in the same bunker. The net bags in the bunker were retrieved after 186 days of ensiling. Dry matter (DM), organic matter (OM), neutral detergent fibre (NDF), crude protein (CP), lactic acid levels, pH, water soluble carbohydrates (WSC) and in vitro organic matter degradability (IVOMD) for both studies were determined. Silage of both experiments was exposed to aerobic conditions for ten days to determine aerobic stability. It is concluded that the inoculant Lalsil® Cereal had the effect of reducing the rate of consumption of WSC during the anaerobic phase and aerobic exposure for both experiments. Silage spoilage due to yeasts and moulds was however more evident with the inoculated silage due the presence of sugars in the micro-silos experiment.

AFRIKAANSE OPSOMMING: Suid-Afrika is bekend vir droë periodes en wisselvallige reënval. Die inkuiling van gewasse is ‘n goeie manier om ruvoer te voorsien in tye van droogtes of tekorte. Kleingraan kuilvoer is veral bekend in die Wes-Kaap, Suid-Afrika en maak ‘n groot deel uit van die melkkoei se rantsoen. Landbouers is nog steeds bekommerd oor die tegniese aspekte wanneer dit kom by die inkuil van gewasse. Vorige navorsing het getoon dat die gebruik van ‘n melksuurbakteriese inokulant saam met die inkuiling van gewasse moontlik die potensiaal het om fermentasie, stabiliteit en degradering te verbeter en sodoende voeromset te verbeter. Twee eksperimente is uitgevoer om die effek van die inkuiling van hawerkuilvoer met Lalsil® Cereal Lactobacilli (Lactobacillus buchneri (NCIMB 40788) en Pediococcus acidilactici (CNCM MA 18/5M)) LAB te bepaal op (1) kuilvoer fermentasie, (2) aërobiese stabiliteit en (3) nutriëntwaarde van die kuilvoer ingekuil in a. mikrosilo’s en b. in ‘n bunker in die buitelug. Hawer (Avena sativa, cv SSH 405) is op 60 ha droë land geplant op Elsenburg in die Wes-Kaap, Suid-Afrika. Die hawer is ingekuil tydens die sagte deeg stadium en die gekapte materiaal was ongeveer 9 mm lank. Gekapte material was deeglik gemeng en in twee gedeel. Die inokulant (Lalsil® Cereal) is op die een gedeelte gesproei om 5.79 x 109 kolonie-vormende eenhede (KVE) melksuurbakterieë per gram vars materiaal te voorsien. Tydens die eerste eksperiment is 24 mikrosilo’s (1.5 L glas silo) (WECK, GmbH u.Co., Wehr-Ofligen, W. Duitsland) vir elke behandeling vol kuilvoer gemaak. Hierdie mikrosilo’s is gestoor in ‘n donker kamer teen kamertemperatuur. Drie mikrosilo’s is per behandeling oopgemaak op dag 1, 4, 8, 15, 30, 60 en 102 na inkuiling om die fermentasie-dinamika te bepaal. ‘n Parallelle studie is gedoen met dieselfde materiaal ingekuil in netsakke binne die bunker. Die materiaal was ingekuil in ses netsakke vir elke behandeling. Nylon toue (3 m) is aan die sakke vasgemaak om die uithaal daarvan op latere stadium te vergemaklik. Hierdie sakke is ingekuil op verskillende dieptes, 1 m en 2 m in dieselfde bunker. Die sakke is na 186 dae weer uitgehaal. Droë materiaal (DM), organiese materiaal (OM), neutraal bestande vesel (NBV), ruproteïen (RP), melksuurvlakke, pH, water oplosbare koolhidrate (WOK) en in vitro organiese materiaal verteerbaarheid (IVOMV) vir beide studies is bepaal. Kuilvoer van beide eksperimente is ook blootgestel aan aërobiese toestande vir 10 dae aan aërobiese toestande blootgestel om aërobiese stabiliteit te bepaal. Daar is bepaal dat die inokulant Lalsil® Cereal het die tempo van WOK verbruik verminder gedurende die anaërobies fase sowel as die aërobiese fase vir beide eksperimente. Kuilvoer wat bederf het as gevolg van giste en swamme was meer sigbaar by die inokulant behandelde kuilvoer as gevolg van die teenwoordigheid van suikers in die mikrosilo’s. (Sleutelwoorde: hawerkuilvoer, inokulant, mikrosilo’s, water oplosbare koolhidrate (WOK), in vitro organiese materiaal verteerbaarheid (IVOMV))

Thesis (MScAgric (Animal Sciences))--Stellenbosch University, 2010.

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