Effects of agro-industrial by-products on health and growth performance of livestock: Studies on white grape marc extract in broilers and three different fibrous by-products in weaned piglets

This thesis investigates the use of plant-derived bioactive compounds and fibrous agro-industrial by-products as sustainable dietary strategies to support gastrointestinal health and function in monogastric animals. Two complementary studies were conducted in broiler chickens and weaned piglets to assess whether such ingredients can modulate digestive physiology, nutrient utilization, or microbial ecology without compromising growth performance. In the first study, broiler chickens were fed a basal diet or diets supplemented with increasing concentrations of a white GME (200, 750, and 1,500 mg polyphenols/kg). GME supplementation did not markedly affect growth performance or apparent ileal digestibility of most nutrients, although FCR showed a tendency to increase at higher doses. Intestinal morphology was largely unchanged, but GC numbers increased in the medium and high GME groups, indicating potential modulation of mucosal protective mechanisms. No alterations were observed in jejunal expression of inflammatory markers, mucins, or tight junction proteins, nor in breast muscle antioxidant capacity. Ussing chamber analysis revealed reduced jejunal tissue conductance after glucose addition in the medium and high GME groups, suggesting subtle effects on epithelial transport. Overall, GME exerted no adverse effects at any tested inclusion level. The second study evaluated the nutritional and physiological impact of including three fibrous by-products (carrot pomace, brewers’ spent grain, and carob pods) at 8 % of the diet in weaned piglets. Growth performance, feed efficiency, and ileal digestibility of protein and AA remained unaffected. Intestinal morphology displayed minor, non-significant improvements in villus architecture with by-product inclusion. While total SCFA acid concentrations in the colon were unchanged, shifts in fermentation patterns were observed, with increased acetate production in piglets fed carrot pomace or carob pods at the expense of propionate. Microbiota profiling revealed moderate but distinct changes, including higher Bifidobacterium spp. abundance in the carrot pomace group, reduced Ruminococcaceae UCG 005 across all by-product diets, and greater microbial richness with carob pods. Collectively, the findings show that polyphenol-rich GME in broilers and fibrous by-products in piglets can be safely included in monogastric diets without compromising performance, while modestly influencing gut morphology, epithelial function, or microbial ecology. Although neither study produced strong physiological or performance responses under high-health experimental conditions, they provide important insights into the functionality and context dependency of plant-based feed ingredients. The work highlights key research needs, such as challenge models, early-life longitudinal designs, multi-omics profiling, dose-response validation, and mechanistic links between microbial metabolism and host function, and establishes a foundation for future studies better tailored to the expected modes of action.

Author dc:creator

• Ouyang, Huilin

• piglets
• broilers
• animal health
• grape marc
• dietary fibre
• digestibility
• intestinal microorganisms
• short-chainfatty acids

Licence dc:rights.uri

• https://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language

ger, eng

Identifier URI

http://dx.doi.org/10.17169/refubium-51421

OAI record oai:identifier

https://refubium.fu-berlin.de/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Arefubium.fu-berlin.de%3Afub188%2F51692