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Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows
Thesis (MScAgric)--Stellenbosch University, 2026.
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| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1869484296955232256 |
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| access_status_str | Open Access |
| author | Grobbelaar, Theunis Johannes |
| author2 | Van Zyl, J. H. C. |
| author_browse | Grobbelaar, Theunis Johannes Van Zyl, J. H. C. |
| author_facet | Van Zyl, J. H. C. Grobbelaar, Theunis Johannes |
| author_sort | Grobbelaar, Theunis Johannes |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136046 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-07-01T04:12:38.931Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/136046 Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows Grobbelaar, Theunis Johannes Van Zyl, J. H. C. Cruywagen, C. W. Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science. Dairy cattle -- Feeding and feeds Corn as feed Starch Enzymes in animal nutrition Rumen fermentation Lactation UCTD Thesis (MScAgric)--Stellenbosch University, 2026. Grobbelaar, T. J. 2026. Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/f1a8078c-8b91-4484-90ca-e8721a8d3f90 ENGLISH ABSTRACT: This thesis investigates whether supplementing dairy cow diets with exogenous α-amylase can offset the performance risks associated with reduced-starch feeding strategies. Rising feed costs and maize price volatility have driven interest in lower-specification diets incorporating fibrous by-products, but these often compromise milk yield and composition. The study combines an in vitro gas production trial with an in vivo lactation experiment to evaluate the enzyme’s efficacy. The literature review highlights maize as the primary energy source in dairy rations, contributing up to 30% dietary starch. While starch is essential for sustaining milk yield, excessive reliance on maize increases costs and can predispose cows to ruminal acidosis. Exogenous α-amylase, such as Ronozyme® RumiStar™, hydrolyses starch into fermentable sugars, potentially improving ruminal fermentation, microbial protein synthesis, and energy availability. Previous research shows inconsistent responses, suggesting enzyme effectiveness depends on starch level and lactation stage. The in vitro trial used a 2 × 2 factorial design comparing high- and low-starch concentrates with or without α-amylase. Results demonstrated that enzyme supplementation significantly increased fermentation rate and reduced lag time in high-starch diets, indicating faster microbial access to starch. However, potential gas production remained unchanged, and low-starch diets showed minimal response. These findings confirm that α-amylase influences fermentation kinetics rather than total substrate degradation, with benefits contingent on starch availability. The in vivo trial, conducted on a commercial Jersey herd, compared a high-spec concentrate with a lower-spec concentrate formulated with α-amylase. Over ten weeks, milk yield and energy-corrected milk were maintained across treatments, despite the lower nutrient density of the enzyme-supplemented diet. Notably, early-lactation cows exhibited a significant ECM increase during the first measurement, suggesting improved energy efficiency during peak metabolic demand. Butterfat concentration and yield improved in early lactation but declined slightly in mid-lactation, while protein and lactose remained largely unaffected. Body weight and condition scores were stable, and milk urea nitrogen showed no differences, indicating adequate nitrogen utilization. Somatic cell count varied inconsistently, likely due to health factors rather than diet. Overall, α-amylase supplementation allowed lower specification diets to sustain performance comparable to high-specification diets, offering a practical strategy to lower feed costs without compromising productivity. The enzyme’s benefits were most evident in early lactation and high-starch contexts, while responses in low-starch diets were limited. Future research should include dry matter intake measurements, rumen health indicators, and economic analyses to refine recommendations and quantify cost-effectiveness. The conclusion is that exogenous α-amylase is a promising tool for improving starch utilization and maintaining milk production under lower-specification feeding systems, particularly during periods of high energy demand and volatile maize markets. AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die potensiaal van eksterne α‑amilase-aanvulling om die prestasierisiko’s wat met verminderde styselvoedingstrategieë gepaard gaan, te verlig. Stygende voerkoste en die wisselvalligheid van mieliepryse het die belangstelling in laer-spesifikasie diëte wat veselryke neweprodukte insluit, versterk. Sulke diëte kan egter melkproduksie en -samestelling benadeel. Die navorsing kombineer ’n in vitro gasproduksieproef met ’n in vivo laktasie-eksperiment om die ensiem se doeltreffendheid te evalueer. Die literatuuroorsig beklemtoon mielies as die primêre energiebron in melkkoeirantsoene, wat tot 30% van die dieet se stysel kan uitmaak. Alhoewel stysel noodsaaklik is vir die instandhouding van melkproduksie, verhoog oormatige afhanklikheid van mielies die koste en kan dit koeie vatbaar maak vir ruminale asidose. Eksterne α‑amilase, soos Ronozyme® RumiStar™, kataliseer die hidrolise van stysel na fermenteerbare suikers en kan sodoende ruminale fermentasie, mikrobiese proteïensintese en energie-beskikbaarheid bevorder. Vorige navorsing toon egter wisselvallige resultate, wat daarop dui dat die ensiem se effektiwiteit afhanklik is van die styselvlak en die stadium van laktasie. Die in vitro proef het ’n 2 × 2 faktoriaalontwerp gebruik waarin hoë- en lae-stysel konsentrate met of sonder α‑amilase vergelyk is. Resultate het aangedui dat ensiemaanvulling die fermentasietempo beduidend verhoog en die vertragingstyd verkort het in hoë-stysel diëte, wat dui op vinniger mikrobiese toegang tot stysel. Potensiële gasproduksie het egter onveranderd gebly, en lae-stysel diëte het minimale reaksie getoon. Hierdie bevindings bevestig dat α‑amilase hoofsaaklik fermentasiekinetika beïnvloed eerder as die totale substraatafbraak, met voordele wat afhanklik is van styselbeskikbaarheid. Die in vivo proef, uitgevoer op ’n kommersiële Jersey-kudde, het ’n hoë-spesifikasie konsentraat vergelyk met ’n laer-spesifikasie konsentraat wat met α‑amilase geformuleer is. Oor ’n periode van tien weke is melkproduksie en energie-gekorregeerde melk gehandhaaf tussen behandelings, ondanks die laer voedingsdigtheid van die ensiemaanvulde dieet. Koeie in vroeë laktasie het ’n beduidende toename in ECM tydens die eerste meting getoon, wat verbeterde energie-doeltreffendheid tydens piek metaboliese aanvraag aandui. Bottervetkonsentrasie en -produksie het verbeter in vroeë laktasie, maar effens afgeneem in middel-laktasie, terwyl proteïen- en laktosevlakke grotendeels onveranderd gebly het. Liggaamsmassa en kondisie-tellings was stabiel, en melkureumstikstof het geen verskille getoon nie, wat op voldoende stikstofbenutting dui. Somatiese seltelling het wisselvallig gewissel, waarskynlik as gevolg van gesondheidsfaktore eerder as dieet. Samevattend het α‑amilase-aanvulling laer-spesifikasie diëte in staat gestel om prestasie te handhaaf wat vergelykbaar is met hoë-spesifikasie diëte. Dit bied ’n praktiese voedingsstrategie om voerkoste te verminder sonder om produktiwiteit in te boet. Die ensiem se voordele was die duidelikste in vroeë laktasie en hoë-stysel kontekste, terwyl reaksies in lae-stysel diëte beperk was. Toekomstige navorsing behoort droëmateriaal-inname, rumingesondheid-aanwysers en ekonomiese ontledings in te sluit om aanbevelings te verfyn en kostedoeltreffendheid te kwantifiseer. Die gevolgtrekking is dat eksterne α‑amilase ’n belowende hulpmiddel is om styselbenutting te verbeter en melkproduksie te handhaaf onder laer-spesifikasie voerstelsels, veral gedurende periodes van hoë energiebehoefte en wisselvallige mieliemarkte. Masters 2026-04-21T08:55:35Z 2026-04-21T08:55:35Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/136046 en Stellenbosch University vii, 77 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Dairy cattle -- Feeding and feeds Corn as feed Starch Enzymes in animal nutrition Rumen fermentation Lactation UCTD Grobbelaar, Theunis Johannes Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title | Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title_full | Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title_fullStr | Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title_full_unstemmed | Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title_short | Effect of dietary starch and exogenous α-amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| title_sort | effect of dietary starch and exogenous α amylase on in vitro gas production kinetics and lactation performance of lactating dairy cows |
| topic | Dairy cattle -- Feeding and feeds Corn as feed Starch Enzymes in animal nutrition Rumen fermentation Lactation UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/136046 |
| work_keys_str_mv | AT grobbelaartheunisjohannes effectofdietarystarchandexogenousaamylaseoninvitrogasproductionkineticsandlactationperformanceoflactatingdairycows |