{"id":16783,"date":"2026-08-20T02:43:20","date_gmt":"2026-08-20T00:43:20","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/lennard-pisa\/"},"modified":"2026-08-20T02:43:28","modified_gmt":"2026-08-20T00:43:28","slug":"lennard-pisa","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/lennard-pisa\/","title":{"rendered":"Lennard Pisa"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":8,"featured_media":16784,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-16783","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"main_text":"","naam_van_het_proefschift":"Starch-driven optimisation of manure bioconversion by housefly larvae","samenvatting":"Huisvliegenlarven hebben een groot potentieel voor de bioconversie van verse dierlijke mest, waarbij nutri\u00ebnten worden hergebruikt en wordt bijgedragen aan het beheer van mestoverschotten. Verse dierlijke mest heeft een relatief hoog eiwitgehalte maar bevat weinig tot geen verteerbare koolhydraten. Hoewel huisvliegenlarven zich volledig kunnen ontwikkelen op pure verse mest, suggereert hun facultatieve vermogen om zetmeel te verteren dat zetmeelsuppletie een haalbare optie is om de larvale opbrengst en de bioconversie van mest te verhogen. In pure mest gebruiken larven eiwit als energiebron; het verschuiven van de eiwit-energiebalans van hun dieet door toevoeging van energie (zetmeel) zou de larvale competitie om eiwit kunnen verminderen, wat leidt tot een hogere overleving van grotere larven, een effici\u00ebnter gebruik van eiwit (hogere eiwitafzetting) en een afname van stikstofhoudend afval door larvale eiwitkatabolisme dat verloren zou gaan door afbraak tot en vervluchtiging van ammoniak.\n\nEchter, verse mest heeft een hoge microbi\u00eble belasting en toevoeging van gemakkelijk verteerbare koolhydraten zoals zetmeel zou kunnen leiden tot veranderingen in microbi\u00eble diversiteit en abundantie die de larvale overleving en groei negatief be\u00efnvloeden. In hoofdstuk 2 werd de hypothese getest dat larven concurreren met mestmicro-organismen om verteerbare koolhydraten die zijn toegevoegd aan verse kippenmest. Gesteriliseerde mest met zetmeel leverde de hoogste individuele (13,2 mg) en totale larvale biomassa (9,7 g) en de hoogste stikstofbioconversie (9,9%) op, waarbij onsteriliseerde pure mest als tweede beste naar voren kwam.\n\nHoofdstuk 3 bepaalde de dosis-responsrelatie tussen zetmeelconcentratie en larvale groei. Een zetmeelgehalte van 10-20% leverde de hoogste totale biomassa op. Hoofdstuk 4 toonde aan dat zetmeel beter wordt benut door oudere larven dan door jongere larven. De timing van koolhydraattoevoeging was cruciaal, aangezien zowel glucose als zetmeel toegevoegd na 72 uur de larvale overleving en groei verbeterde vergeleken met toevoeging bij de start. Hoofdstuk 5 onderzocht het effect van larvale dichtheid; hogere dichtheden verbeterden de overleving van jonge larven, maar versnelden de uitdroging van het substraat, wat de groei in latere stadia beperkte.\n\nDe belangrijkste conclusies van dit proefschrift zijn dat de groei van huisvliegenlarven op kippenmest wordt beperkt door de lage beschikbaarheid van verteerbare energie. Matige suppletie met zetmeel verhoogt de biomassa en stikstofbioconversie aanzienlijk. De voordelen worden echter beperkt door competitie met micro-organismen in de mest. Het gebruik van zetmeel door larven lijkt fysiologisch gereguleerd, waarbij oudere larven het meeste baat hebben bij suppletie.","summary":"Housefly larvae have a high potential for the bioconversion of fresh animal manures, upcycling nutrients and contributing to (surplus) manure management. Fresh animal manures have a relatively high protein content but contain little to no digestible carbohydrates. Although housefly larvae can fully develop on pure fresh manure, their facultative ability to digest starch suggests that starch supplementation is a viable option to increase larval yield and manure bioconversion. In pure manures larvae use protein as an energy source and shifting the protein-energy balance of their diet by addition of energy (starch) might decrease larval competition for protein, leading to higher survival of bigger larvae, increase more efficient use of protein (higher protein deposition) and decreasing nitrogenous waste from larval protein catabolism that would be lost by degradation to and volatilization of ammonia. However, fresh manure has a high microbial load and addition of easily digestible carbohydrates such as starch could lead to changes in microbial diversity and abundance that negatively affect larval survival and growth. In Chapter 1, a synthesis was made of available information, combining information on larval nutritional needs, digestive physiology, housefly phylogeny and larval ecology to identify knowledge gaps and testable hypotheses\/strategies for suppletion of fresh manure with starch. In Chapter 2, the hypothesis was tested that larvae compete with manure microorganisms for digestible carbohydrates added to fresh chicken excreta. This was done by adding gelatinized corn starch (digestible carbohydrate) or fructo-oligosaccharides (non-digestible carbohydrate) to unsterilized (active microbiota) and heat sterilized (inactive microbiota) excreta at 18% of substrate dry matter (DM), followed by inoculation with housefly eggs. Sterilized excreta with starch yielded the highest individual (13.2 mg) and total larval biomass (9.7 g) and highest nitrogen bioconversion (9.9%), with unsterilized pure excreta being second best (8.1 mg, 7.2 g and 9.3%, respectively). Starch supplemented unsterilized excreta and fructo-oligosaccharides supplemented excreta (sterilized and unsterilized) showed much lower larval biomass compared to pure unsterilized excreta. The experiment also showed that, though larval biomass increased, larval survival was negatively affected by adding starch to sterilized excreta. In Chapter 3, the dose-response relation between starch concentration and larval growth, survival and substrate bioconversion was determined for sterilized and unsterilized excreta. A starch content of 15-20% of DM yielded the highest overall mean total larval biomass (39 g) in unsterilized excreta, whereas 10% starch content led to a higher total larval biomass in unsterilized excreta (43 g). After their maxima at these concentrations in both types of excreta, total larval biomass decreased, much more gradually in sterilized excreta. Larval survival was highest in pure unsterilized excreta (80%) and decreased more or less linearly with increasing starch content to 14% at 50% starch, showing a similar decrease in sterilized excreta. The optimal starch contents increased nitrogen bioconversion with 40% (unsterilized, from 10.7 to 15%) and 100% (sterilized, from 7.5 to 15%) compared to pure unsterilized excreta. Around 20 to 25% starch content, uric acid and ammonia contents, pH, and C\/N of substrate residues decreased rapidly, indicating a tipping point that occurred later in sterilized excreta. In Chapter 4, the theory developed in Chapter 1, that utilization of starch by larvae depends on larval stage (age) dependent amylases was tested. Starch and fresh excreta were added at 10% DM to unsterilized excreta, either at the start (0 h) or at 72 h during the larval growth period of 120 h, using the extremely easily digestible glucose as a positive control (time effect starch specific) and indigestible cellulose as negative control (effect of stirring). Glucose and starch substantially improved larval performance compared with fresh manure and cellulose (non-digestible carbohydrate). Supplementation at 72 h, with glucose increased individual larval mass by 12%, total biomass by 33% and survival by 19% compared to 0 h. Starch at 72 h increased total biomass by 30% and survival by 24%, while effects on individual mass were small (2%). Dry matter bioconversion efficiency increased by 27% with late glucose and 20% with late starch, whereas late excreta addition caused an 18% decrease. Nitrogen bioconversion rose by 36% with late glucose and 37% with late starch compared to 0 h. The results supported the hypothesis that starch is better utilized by older larvae than by younger larvae. The mechanism underlying the differences in larval biomass is that larval survival is higher when starch is added later, with the increase in total larval biomass driven by improved survival and not individual larva mass. In Chapter 5, a second theory described in Chapter 1 was tested, addressing the hypothesized positive effect of higher larval densities on larval survival and early growth in starch-supplemented unsterilized excreta. Starch tends to lower larval survival and higher larval densities might mitigate this through more efficient digestion by increasing temperature and substrate mixing. Unsterilized excreta substrates, unsupplemented or containing glucose or starch at 10% of DM were inoculated with four egg densities (8-12-16-20 eggs\/g substrate), with different replicates harvested at two harvest times (58 and 120 h). Higher densities improved survival of the early-stage larvae, particularly in supplemented substrates, but accelerated substrate drying reduced late-stage larval growth and bioconversion. Starch lowered residue ammonia and pH, suggesting better nitrogen retention. Statistical analysis showed that biomass yielded by early-stage growth was more associated with substrate, whereas late-stage biomass was more associated with density. Harvesting the larger biomass of early growth showed the nitrogen bioconversion, with gains of 13 to 22%. In Chapter 6, the results of the experimental chapters are evaluated, indicating challenges and potential improvement of experimental procedures, as well as implications of the thesis results for housefly mass-rearing and suggestions for future research. The Appendices describe developmental work on housefly rearing, egg collection and larvae harvesting. The main conclusions of this thesis are that housefly larval growth on and bioconversion of chicken excreta is limited by low availability of digestible energy. Moderate supplementation with easily digestible carbohydrates, particularly starch, substantially increases larval biomass and nitrogen bioconversion. However, starch supplementation reduces survival and its benefits are strongly constrained by competition with manure microorganisms, making microbial activity a key determinant of larval access to energy. Larval utilization of starch appears to be developmentally regulated, with older larvae benefiting most from supplementation. Higher larval densities modify growth and bioconversion outcomes by enhancing early survival but constrain late-stage growth by increased dehydration of substrates.","auteur":"Lennard Pisa","auteur_slug":"lennard-pisa","publicatiedatum":"25 augustus 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/lennardpisa?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/d067c14c-a730-4563-a703-2738be9eee2e\/highres","url_epub":"","ordernummer":"19459","isbn":"","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":16785,"video_url":"","podcast_url":"","naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16783","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=16783"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16783\/revisions"}],"predecessor-version":[{"id":16786,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16783\/revisions\/16786"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/16784"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=16783"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=16783"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}