A study was conducted to evaluate a natural carbohydrate fraction (NCF) derived from mannan 2 oligosaccharide in feed on growth performance, intestinal morphology and goblet cell number and 3 area of male broilers. Dietary treatments included: 1) control diet (antibiotic and NCF free), 2) 4 NCF at 200g/t, 3) NCF at 400g/t, and 4) NCF 800g/t. Birds were placed into 12 replicate 5 pens/treatment (5 birds/pen). Body weight and feed intake were recorded weekly to day 42. At this 6 time a 2.5cm section of jejunum and duodenum were excised post mortem for morphological 7 analysis. Birds fed 200g/t and 800g/t NCF were significantly (P<0.01) heavier from day 14 8 onwards than the control birds. Feed intake was significantly increased for birds fed 200g/t NCF 9 over the control in weeks 3 and 5 (P<0.05). Diet including 200g/t and 800g/t of NCF significantly 10 decreased the FCR over the control in the first phase (1-14 days) (P<0.01), in the second phase all 11 inclusion levels of NCF decreased FCR (P<0.05). NCF had no significant effect on villus height, 12 villus width, crypt depth or villus to crypt ratio in either duodenum or jejunum. NCF did not 13 significantly affect goblet cell area or goblet cell number in the duodenum, however in the jejunum 14 800g/t NCF significantly (P<0.05) increased goblet cell area over the control. In conclusion under 15 the conditions of this trial NCF showed a positive effect on performance in the starter and grower 16 phases, and increased goblet cell area in the jejunum, suggesting higher levels of mucin production.
17This indicated that the performance benefit of NCF could be age-dependent with younger birds 18 responding more than the older ones. In the conditions of the poultry research unit, there were no 19 additional benefits to performance when feeding NCF for a longer period (post 4 weeks), however 20 it is postulated that birds fed NCF would have greater defence to pathogenic challenge through 21 increased storage capacity of mucin.
22Key words: Yeast, feed additive, prebiotic, crypt depth, villi height, performance, goblet cell
INTRODUCTION
24Over the past few years there has been increased concern about antibiotic resistant bacteria and the 25 inclusion of antibiotics in animal diets for growth promotion. This led to the ban of a number of 26 antibiotics growth promoter (Dibner & Richards, 2005). Since the EU ban on using antibiotic as 27 growth promoters in 2006 (Huff, et al., 2006), there has been an increase in the incidence of 28 endemic diseases in poultry (Chee, 2008), in addition to reports of slower growth and higher 29 disease challenges causing significant economic losses (Thomke & Elwinger, 1998) and negative 30 welfare implications for poultry. In particular the gut health has been affected. Without a healthy 31 intestinal tract a broiler cannot reach its full performance potential. Due to this there has been a 32 drive in the market for feed supplements that will improve health and production of poultry but 33 remain safe for humans. The morphological str...
