UC Davis

Chicken is the preferred animal protein (meat) source worldwide, surpassing pork in production in 2021 and projected to continue in 2022. However, greenhouse gas (GHG) emissions have increased 11% from 2018 to 2019, with 55% coming from agriculture production. Another increasing environmental contaminant is ammonia, produced by birds due to the overconsumption of protein containing nitrogen. Changing the microbiota of birds could help to reduce the production of ammonia. The microbiota is influenced by many factors including age, disease, antibiotic usage, and diet; with the largest impact via the diet. Alterations to the microbiota can be achieved by a variety of feed additives, including prebiotics, organic acids, phytogenics, enzymes, bacteriophages, and probiotics while simultaneously improving performance and digestibility. Despite being commonplace as an animal feed additive, there is limited data showing how long layers and broilers need to be given probiotics to become established in the bird’s gut microbiota. Therefore, the goal of this study was to determine if a yeast strain (Saccharomyces cerevisiae) improved the effects of a probiotic mixture (Lactobacillus plantarum and L. rhamnosus) through an increase in production, a reduction of ammonia/nitrogen levels in the blood and manure, and an increase in digestibility. Additionally, results may highlight the week in which improvements were observed. Findings could help determine the minimum length of time for which a probiotic should be provided. One-day-old Cobb 500 broiler chicks (600) were fed one of the following diets: no alterations to the basal diet as a control (CON); probiotic S. cerevisiae, inclusion rate at 4.26 × 106 CFU/kg of feed (SCY); probiotics L. plantarum and L. rhamnosus, inclusion rate at 4.35 × 108 CFU/kg of feed for each (LPR); and a combination of L. plantarum and L. rhamnosus at 4.35 × 108 CFU/kg of feed for each, and S. cerevisiae at an inclusion rate of 4.26 × 106 CFU/kg of feed (SWL). The experimental design was completely randomized with pens as the experimental unit. There were four treatments, with five replicates, each with 30 broilers per pen (replicate). Performance was measured weekly as feed consumption, weight gain, body weight (BW), and feed conversion ratio (FCR) over six weeks. Accompanying biochemical analyses included lipase activity of the pancreas, liver weight, and uric acid (UA) concentration in liver on days 15, 29, and 43. In addition, albumin, total protein, UA, ammonia, and blood urea nitrogen (BUN) were measured in serum. The ammonium ion from manure and apparent ileal digestibility from digesta were also measured. Significance was determined at P < 0.05. Probiotics supplements produced no significant differences in biochemical analyses; however, there were significant temporal changes in performance. Feed consumption increased over time for all treatments (P = 2.00 × 10- 16). CON had lower weight gain in week 2 (P = 0.013). CON had the lowest BW in week 5 (P = 0.0008) and week 6 (P = 0.0124) compared to SWL. Future research into specific probiotic strains, with well-defined inclusion rates, and surrounding environmental analyses of present microbes are needed to ascertain effects of probiotics. Ultimately, work on confirmation of probiotics present in the digesta/ceca, how the probiotics alter the microbiota within the GI tract, and how probiotics alter the serum heterophil:lymphocyte ratio to further examine potential immune response to probiotics is needed.