Interactive effect of 2 dietary calcium and phytase levels on broilers challenged with subclinical necrotic enteritis: part 1—broiler performance, gut lesions and pH, bacterial counts, and apparent ileal digestibility

Abstract

This study investigated the hypothesis that high dietary calcium ( Ca ) would stimulate necrotic enteritis ( NE ) and reduce performance, gut health, and nutrient digestibility, and if increased, phytase would reduce NE. Ross 308 male broilers (n = 768) were randomly distributed to 8 treatments in a factorial arrangement. Factors were NE challenge (no or yes), phytase level (500 or 1,500 FTU/kg using 500 FTU/kg matrix values), and Ca level (0.6 or 1.0% starter, 0.5 or 0.9% grower, 0.4 or 0.8% finisher) with the same level of available P (0.40 S, 0.35 G, and 0.35 F). There were 48 pens, 16 birds per pen and 6 replications. Half of the birds were challenged with Eimeria spp on day 9 and 10 8 CFU per mL of Clostridium perfringens strain EHE-NE18 on day 14 and 15. Gain was higher in birds fed high phytase on day 14 ( P < 0.01), day 21 ( P < 0.01), day 28 ( P < 0.01), and day 35 ( P < 0.01). Birds fed high phytase had greater livability on day 21 ( P < 0.01). Ca was more digestible in high-Ca diets on day 16, and an NE × Ca interaction ( P < 0.05) showed this effect to be more pronounced in unchallenged than in challenged birds. A challenge × Ca interaction for apparent ileal digestibility ( AID ) of crude protein ( CP ) ( P < 0.05) indicated lower AID of CP in challenged birds fed high Ca. The challenge decreased AID of Ca ( P < 0.01). Ca level had no impact on C. perfringens count, but it decreased Lactobacillus ( P < 0.05) and Bifidobacteria ( P < 0.05) populations in the ceca. High dietary Ca decreased feed conversion ratio. Overall (42 D), the highest WG was observed in unchallenged birds fed high Ca and high phytase with the lowest WG observed in NE-challenged birds fed low Ca and low phytase. The results suggest that full matrix values for high doses of phytase may be appropriate during NE challenge.

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: 3. Serum calcium and phosphorus, and bone mineralization

“…A reduction in serum Ca and P in birds during disease has been previously reported ( Fernandez et al., 1994 , Yarru et al., 2009 , Zhao et al., 2010 , Yunus and Böhm, 2013 , Igwe et al., 2018 ). The current observation might be due to the low feed intake and poor P digestibility as a result of poor gut integrity and increased endogenous losses that characterize NE incidence and was the case in the present study ( Zanu et al., 2019 ). On the other hand, the high Ca diet depressed serum P and increased serum Ca only under the unchallenged condition, suggesting again that the serum was reflecting the imbalanced Ca:P absorption taking place from the intestine.…”

“…Diets were based on wheat, soybean meal, cold-pressed expeller canola meal and formulated to contain 3,000 kcal/kg MEn and 1.24% standard ileal digestible lysine in starter and 3,100 kcal/kg MEn and 1.14% and 0.99% standardized ileal digestible lysine in grower and finisher, respectively. Further details of diet composition are give in the study by Zanu et al., 2020 . Four diets were formulated for each phase (starter, grower, finisher) in accordance with Ross 308 nutrient specifications ( Aviagen, 2014 ).…”

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 1. Performance, intestinal lesions and pH, bacterial counts and apparent ileal digestibility

“…However, an increase in the count of Bacteroides in the challenged birds appeared to confirm a positive correlation between C. perfringens and Bacteroides spp. counts in previous studies ( Zanu et al., 2019b ). Bacteroides are normal intestinal flora but can evolve into a pathogenic form, and the amounts could increase when the gut is pathologically changed or impaired ( Phong et al., 2010 ).…”

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: part 2. Gut permeability, phytate ester concentrations, jejunal gene expression, and intestinal morphology

“…The current study indicates that high phytase with low Ca is recommended, as the combination was able to decrease the higher phytate esters. In addition, a higher level of Ca appeared to increase the concentration of IP5 and IP6 in the ileum (regardless of NE challenge), suggesting that the higher ileal pH observed in this study at day 29 ( Zanu et al., 2020a ) as a result of high dietary Ca might have caused precipitation of these esters. The reason is that the phytase used produces IP1 and not inositol may be erroneously stated in other reports.…”

“…This Ca-phytate formation is influenced by the pH coupled and Ca:phytate molar ratios. Thus, the higher pH recorded in the ileum relative to higher dietary Ca at day 29 in the present study ( Zanu et al., 2020a ) might have contributed to the reduction in the degradation of phytate. Several experiments generally support the observation that higher pH is pivotal to Ca-phytate complex formation ( Tamim et al., 2004 ; Li et al., 2017 ).…”