A few years back, it was discovered that in-feed coniferous resin acids support gut integrity and luminal homeostasis in the intestinal mucosa of broiler chickens by reducing inflammation-associated degradation of collagen. This very positive, direct effect on intestinal tissue manifests as improved bird performance and reduced abundance of inflammatory T-cells in gut mucosa. Such a mechanism-of-action has not been discovered for any other feed ingredient or natural feed additive.
The One Health -concept states that the health of humans, animals and the environment are interconnected. For ensuring human healthcare, restrictions on antibiotic treatments to farm animals are necessary, and antibiotic growth promoters (AGPs) should be avoided. However, in many parts of the world, AGPs are still routinely used in farm animal feeds. For example, in Pakistan, the background pathogen pressure is considered too high for AGP-free production of broiler chickens.
Hankkija Finnish Feed Innovations conducted a 35-day broiler study in Pakistan, in order to compare the effects of Progres®, the tall oil fatty acid (TOFA) -based feed ingredient with resin acids, and Lincomycin, an AGP commonly used for improving the performance of meat poultry. Results of the experiment were presented at the 73rd Annual meeting of The European Federation of Animal Science, EAAP2022, in the International Congress Center of Alfândega do Porto, Portugal. The presentation, titled “Effects of dietary tall oil fatty acids on broiler performance and intestinal immunology”, was given by Dr. Hannele Kettunen from Hankkija FFI.
Material and methods
For the experiment, 357 male Ross 308 hatchlings were housed in pens of 17 birds. The pens were randomly allocated into the following dietary treatments, with 7 pens/treatment:
T1) Positive control, Lincomycin 4.4% at 150g/ton
T2) Progres® at 0.5 kg/ton, no AGPs
T3) Progres® at 1.0 kg/ton, no AGPs
Negative control without amendments was not included due to background pathogen challenge in the environment.
Bird weight and feed intake were recorded every week, and feed conversion ratio (FCR) was calculated. On day 21, two birds/pen were sampled for duodenal and ileal tissue for measuring villus length and crypt depth by routine histology, and the density of CD3+ T-cells by immunohistochemistry. The CD3+ T-cells are lymphocytes which take part in inflammatory reactions of gut tissue. An increased abundance of these cells thus indicates the presence of inflammation. On day 34, litter quality of each pen was evaluated, and every bird was scored for foot pad dermatitis (FPD). Statistical analysis was conducted by ANOVA and Duncan’s test.
Results and Discussion
Performance: Bird weight gain, feed consumption and FCR were similar for days 1-35 in all treatments for (Figure 1 A-C). Mortality was approximately 3.8% in all dietary treatments. Equal performance and mortality of all diet groups indicates that Progres® at 0.5 – 1.0 kg/ton gave the same performance effects to the birds as the Lincomycin treatment.
Figure 1. Effect of Progres® (TOFA) at 0.5 kg/ton or 1.0 kg/ton on bird weight on day 35 (A), feed intake per bird for days 1–35 (B) and feed conversion ratio for days 1-35 (C), in comparison to the Lincomycin treatment (Positive control). The performance was statistically equal in all treatments.
Litter quality and FPD scores: Litter quality was improved by Progres®, with a significant difference between the Lincomycin and Progres 1.0 kg/ton (Figure 2A). A dose-dependent but nonsignificant improvement in FPD scores by Progres® was reported (Figure 2B). Improved litter quality by dietary Progres®, in comparison to negative control, has been observed several times in previous experiments, sometimes accompanied by significantly improved FPD scores. This observation indicates better gut homeostasis and less diarrhoea in Progres® -treatments. For the present experiment, it is worth keeping in mind that Progres® gave better results than the AGP Lincomycin.
Figure 2. Effect of Progres® (TOFA) at 0.5 kg/ton or 1.0 kg/ton on litter quality (A) and foot pad dermatitis score (B), in comparison to the Lincomycin-treatment (Positive control). Different letter (a, b), denotes for statistical difference between the treatments (p < 0.05). All treatments had statistically similar FPD-scores.
Gut histology: Progres®-fed birds showed deeper ileal crypts, but other significant effects on histomorphology were not observed (data not shown). This was the first study to compare the intestinal histology of Progres®-treated broiler chickens, against an AGP-treatment. Previous studies have shown increased length of small-intestinal villi by in-feed resin acids, compared against a negative control group.
Immunohistochemistry: Density of the CD3+ T-cells in duodenum and ileum was significantly lower for the Progres® 1.0 kg/ton group than for the Lincomycin-treated group, indicating lower inflammatory activity in the gut wall of Progres® -fed birds (Figure 3). In ileum, even the 0.5 kg/ton dose of Progres® was sufficient to significantly lower the inflammatory activity in gut wall, in comparison to the Lincomycin group. Effect of a similar magnitude has previously been seen in broiler chickens fed with purified resin acids, when compared against a negative control group.
Figure 3. Effect of Progres® (TOFA) at 0.5 kg/ton or 1.0 kg/ton on the abundance of CD3+ cells in duodenal and jejunal villi, in comparison to the Lincomycin-treatment (Positive control). Different letter (a, b), denotes for statistical difference between the treatments (p < 0.05). The result indicates less inflammatory activity in the gut wall of Progres®-fed than Lincomycin-treated broiler chickens.
The results suggest that dietary Progres® amendment at 0.5-1.0 kg/tn is equally effective as the antibiotic growth promoter Lincomycin in ensuring the good performance of broiler chickens. Litter quality improvement and reduction of intestinal inflammatory activity by Progres® indicates positive effects of Progres® on intestinal homeostasis. The study indicates that even in areas with high background pathogen pressure, it is possible to improve the intestinal condition of broiler chickens by amending their feeds with Progres®, rather than by AGPs.