Assessment of dry whey powder as prebiotic in the feeding of laying hens and broilers

Resumen

During the last decades, the interest to search for non-antibiotic fed alternatives to improve the performance of laying hens and broilers through gastrointestinal microbial modulations without causing antimicrobial resistance has increased considerably. From the nutritional perspective, one of the approaches is based on the dietary inclusion of prebiotics to benefit the intestinal microbial composition, and therefore animal health and performance. The main objective of the present thesis was to evaluate the prebiotic potential of the inclusion of dry whey powder (DWP), as a lactose source, in the formulation of laying hens and broilers’ feed. In this context, five studies were conducted to determine the feasibility of the use of DWP when added to corn-soybean or whey-barley based diets. Moreover, DWP effectiveness through its simultaneous supplementation with other non-antibiotic feed additives was also assessed. The first study determined the effect of supplementing corn-soybean based diets of laying hens with DWP, Pediococus acidilactici (PA), and the combination of both as synbiotic (DWP-PA) on the productive performance, egg quality traits, and cecal microbial counts. The results showed that cecal counts of Bifidobacterium spp. were increased with the addition of DWP, while an interaction between DWP and PA levels was found on egg production and on cecal counts of Clostridium perfringens, so that the addition of DWP increased egg production and reduced C. perfringens colony counts only when PA was not used. According to these results, the addition of DWP modulated the target cecal bacteria and increased egg production. The second study was carried out with the same animals used in study 1. The aim of this was to analyze the cecal microbial composition, using Illumina amplicon sequencing of the 16S rRNA gene, and the cecal microbial functional profile, using DNA sequencing through Illumina HiSeq2500 platform, of laying hens fed with DWP, PA, and DWP-PA. The results revealed that microbial communities of hens fed with control and PA were different from those fed with DWP and DWP-PA, while no differences were found between control and PA, and between DWP and DWP-PA. Feeding with DWP and DWP-PA mainly promoted the presence of Olsenella spp. Lactobacillus crispatus, and Megamonas spp. in comparison with the remaining diets. Metagenomics approach revealed that a core of main functions was shared between all metagenomes (45.5%), although DWP stimulated that microbiota encoded more unique functions (22.5%) compared with control, which showed the lowest percentage (1.6%). Major presence of genes encoding the metabolism of butanoate, propanoate, galactose, and inositol phosphate were especially stimulated by DWP. Results from this experiment indicated that each dietary supplementation influenced the cecal microbial community, but these changes did not imply a disturbance in their main biological roles. However, some specific metabolic functions encoded by the community, were present or absent depending on the source of supplementation. In the third study, apparent ileal digestibility (AID), pH of gastrointestinal content at various segments, duodenal histomorphometry, cecal microbial counts, and productive performance of broilers were studied in response to DWP and fat-coated calcium butyrate (CaB) supplementation to corn-soybean based diets. The results indicated that with the addition of DWP, the AID of dry matter, crude protein, Ca and P increased, and cecum pH decreased only when CaB was also added. Similarly, with the addition of DWP, villus height, villus height to crypt depth ratio, and villus surface area were increased only when CaB was also added, while the supplementation of WP increased Bifidobacterium spp. colony counts only when CaB was no added. In relation to performance results, it was observed that with the dietary supplementation of DWP, the average daily gain (ADG) and feed intake (FI) increased during starter-grower finisher periods, and the entire feeding period only when CaB was also added. However, with the addition of DWP, feed conversion ratio (FCR) decreased in broilers fed without CaB, but it increased in those fed with CaB during the grower-finisher and entire feeding periods. These findings suggest that the supplementation of DWP without CaB addition improve FCR of broilers. However, the joint supplementation of DWP and CaB improve duodenal development, increases nutrient AID, and the weight and feed ingestion of broilers. The fourth study was carried out to assess the influence of supplementing corn-soybean broiler diets with DWP and whey protein concentrate (WPC) on AID, productive performance and cecal microbiota composition at the end of the productive period, using Illumina amplicon sequencing of the 16S rRNA gene. The results showed that 60-DWP increased the AID of Ca, while 80-WPC improved both AID of Ca and P when compared to control diet. Feeding broilers with 60-DWP and 80-WPC increased their BW, ADG, and FI during the starter and grower-finisher periods, and during the entire feeding period. Supplementing 60-DWP and 80-WPC reduced FCR during the starter period, while 60-DWP reduced this parameter during the entire feeding period. Cecal microbial communities of broilers fed with 60-DWP and 80-WPC differed from those fed with control diet. The abundance of Bacteroides fragilis, Bacteroides spp., Escherichia coli/Shigella flexneri and Megamonas furniformis increased when 60-DWP and 80-WPC were included, while the presence of Helicobacter pullorum decreased. Lactobacillus salivarius consistently increased in chickens with better FCR, which were those fed with 60-DWP. These results indicate that growth of chickens is improved by 60-DWP and 80-WPC supplementation because of a higher mineral digestibility, increased FI, and modulation of cecal microbiota communities. The fifth study was conducted to investigate the effect of supplementing wheat-barley based diets with 60-DWP, chitosan (5-QUIT), DWP-QUIT, and Inulin (20-INU) on duodenal histomorphometry, productive performance and cecal microbiota composition at days 21 and 42 of age, using Illumina amplicon sequencing of the 16S rRNA gene. The results indicated that feeding chickens with any of the tested additives diminished their BW, ADG, and FI during the starter period. This was also observed during the entire feeding period, except for INU supplementation that showed similar values to control. At day 21, no differences in microbiota composition of control, 60-DWP, 5-CHIT and 20-INU birds were found, which ceca were highly harboured by Lactobacillus gallinarum, although only control promoted greater BW, ADG, and FI. Control and 60-DWP treatments did not differ in their ceca communities at day 42, although only control increased BW, ADG, and FI. In both cases, ceca showed higher abundance of Lactobacillus gallinarum and Bacteroides vulgatus, and lower abundance of Escherichia coli/Shigella flexneri and Bacteroides fragilis. The present findings indicate that chicken growth is reduced by supplementing wheat-barley based diets with DWP, CHIT, DWP plus CHIT, and INU, at the tested doses, as a consequence of a reduction in FI. Moreover, the results revealed that cecal microbiota composition was influenced by diet at every stage of life, although no clear association between microbiota and performance was detected.