Four studies consisting of 6 experiments were conducted to investigate the likely mechanisms of actions of feed additives used in the place of antibiotics to improve performance and enteric health in broilers. In the first study, the relationship between digesta pH, body weight and nutrient utilisation in broilers of the same breed but with different propensity for weight gain at different ages were investigated. It was noted that birds in group H (heavy) consumed more feed (P < 0.001) than those in group L (light) during the starter (day 10 to 14) and grower (day 15 to 28) phases. Birds in group H had lower (P < 0.05) caecal pH in the starter and grower phases and lower (P < 0.05) proventriculus pH in grower and finisher (day 29 to 42) phases. In the grower phase, caecal pH was correlated (r = 0.553) with total tract retention of DM and energy utilisation at both the ileal and total tract levels, whereas during the finisher phase, crop pH was correlated with ileal nutrient utilisation, and jejunum pH was correlated with total tract energy utilisation. The data showed that differences in body weight are also reflected in differences in gut pH which is likely indicative of differences in intestinal condition between birds with heavier or lighter body weight. The differences in the gut pH explained about half of the variations in total tract nutrient and energy utilisation. Lower gut pH is advantageous for beneficial bacteria colonization but disadvantageous for pathogenic ones colonization and hence it is likely that birds with the same genetic potential may have differences in growth performance based on the type of bacteria colonizing their gut. In the second study, the response of broiler chickens to the supplementation of benzoic acid (BA) was investigated using growth performance, nutrient and energy utilization, intestinal acidity and histomorphology of the intestine as response criteria, using 945 Ross 308 male broilers in 3 treatments with 7 replicates each for 42 days. In the grower (day 11 to 21) phase, BA supplementation at 0.53 g/kg (BA1) increased (P < 0.001) body weight gain and reduced (P < 0.01) FCR, whereas supplementation at 3.20 g/kg (BA2) reduced (P < 0.005) the feed intake without affecting the body weight gain, resulting in a better FCR. Compared with the control, BA supplementations increased (P < 0.001) the protein and energy efficiency ratios in starter and grower phases and tended (P < 0.10) to increase the energy efficiency ratio in finisher phase (day 22 to 42) or the overall experimental period (day 0 – 42). BA supplementations at both rates reduced the caecal pH. Supplementation of 3.20 g/kg BA stimulated the proliferation of the absorptive cells in the jejunum, as shown in the improvement of the villus and crypt dimensions. The data from this study indicated that dietary supplementation of BA beneficially modified intestinal milieu and improved the growth performance of broiler chicks at 42 d of age. In third study, two experiments were conducted to investigate the benefit of using BA and turmeric meal (TM) individually or in combination using growth performance, nutrient utilization, and intestinal health as response criteria. A total of 300 male one-day old broilers (Ross 308) were assigned in 5 treatments in randomized complete block design with 2x2 + 1 factorial arrangement, with 6 replicate pens and 10 birds each pen. Combination of 1 g/kg BA and 5 g/kg TM improved (P < 0.05) body weight gain relative to the control. Supplementation of 2 g/kg BA reduced the pH in the crop (P < 0.001) and jejunum (P < 0.01), whereas combination of BA and TM at 2 and 10 g/kg respectively reduced digesta pH in the crop (P < 0.001), jejunum (P < 0.01), and caeca (P < 0.05). All of the dietary treatments increased (P < 0.005) villus height, crypt depth and width relative to the control. All dietary treatments increased (P < 0.001) AME and AMEn relative to the control diet, whilst supplementation of 10 g/kg TM only increased energy digestibility (P < 0.05) and ileal digestible energy (P < 0.01). Orthogonal contrasts showed that BA and TM were additive in their effects on the growth performance, digesta pH in the proventriculus, jejunum, and ileum, and energy utilization, but associative on the energy digestibility, as well as the crop and caecal pH. None of the treatment altered the relative weight and length of the digestive tract of 21 days old broiler. These studies pointed out that BA and TM can be used in the diet individually or in combination to improve the enteric health, nutrient and energy utilization, and growth performance of broiler chickens. In the fourth study, two experiments were designed to investigate the efficacy of TM and garlic meal (GM) using growth performance, intestinal pH, and energy and nutrient utilisation as response criteria. Three hundreds male one-day old broilers (Ross 308) were assigned in 5 treatments in randomized complete block design with 2x2 + 1 factorial arrangement, with 6 replicate pens and 10 birds each pen. Results showed that combination of GM and TM at 10 g/kg each increased (P < 0.05) the body weight gain, final body weight, and gain to feed ratio relative to the control and the diet with GM supplementation alone. The crop and caecal pH were reduced (P < 0.05) when the diets were supplemented with TM alone at 10 g/kg. The proventriculus pH also dropped (P < 0.05) following GM and TM mixture supplementation at 10 g/kg each relative to the control. Supplementation of 10 g/kg TM alone or in combination with GM at 5 g/kg each increased (P < 0.05) the apparent ileal energy digestibility and ileal digestible energy. All of the dietary treatments increased (P < 0.001) both AME and AMEn compared with the control. Orthogonal contrasts showed that GM and TM were additive for feed intake, nutrient and energy utilization at both the ileal and total tract levels, but associative in their effects on body weight gain and gain to feed ratio. These studies indicated that GM and TM can be used alone or in combination to support intestinal health, improve energy and nutrient utilization, and stimulate growth performance of broiler chickens. Combination of GM and TM at the rate of 5 g/kg each was optimum for enhancing nutrient and energy utilization and promoting growth performance of broiler chickens. Taken together, these studies showed that benzoic acid and herbal products (garlic and turmeric meal) can be supplemented in the diet alone or in combination to improve the enteric health, nutrient and energy utilization, and growth performance of broiler chickens. Improvements on the growth performance might be attributed to the reduction of the entero-pathogens in the gut, enhancement of intestinal health, alteration of the absorptive cells in the intestinal wall, and improvement in the nutrient and energy utilization.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:567951 |
| Date | January 2012 |
| Creators | Dono, Nanung Danar |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/4025/ |
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