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

Optimization of Split Feeding Strategy for Laying Hens Through a Response Surface Model

Laying hens' metabolism goes through a cyclic process to produce eggs, which requires higher dietary protein and energy in the morning (AM) and higher calcium (Ca) in the afternoon/evening (PM) than the rest of the day. Therefore, poultry scientists are trying to adopt a new feeding strategy called AM/PM or split feeding to precisely meet hen's requirements more effectively than conventional methods. A 10-week cage layer trial was carried out via a Box-Behnken response surface design to identify the optimal amount of protein, energy, and calcium of the AM/PM diets. There were 13 test treatments with three levels of crude protein (19.6%/18.4%, 20.3%/17.7%, 21%/17%), calcium (3.3%/4.9%, 2.5%/5.7%, 1.6%/6.6%), and apparent metabolizable energy (AME) (12 MJ/kg/11.2 MJ/kg, 12.4 MJ/kg/10.8 MJ/kg, 12.8 MJ/kg/10.4 MJ/kg) for AM/PM diets respectively and a control treatment with industry baseline (CP-19%, Ca-4.1% and ME 11.6 MJ/kg). These are the calculated values of nutrients on a dry matter basis. A total of 364 hens were randomly distributed into 2 dietary treatments where each treatment had 13 replicates (2 hens per replicate cage, 26 hens per treatment). AM and PM diets were swapped out at approximately 8 am and 4 pm each day. Egg production and hen performance were measured daily and weekly, respectively, with egg quality, serum Ca, and nutrient digestibility measured at week 10. AM:PM intake and feed cost were calculated for each treatment. The optimal FCR, feed cost, and AM:PM intake were used to determine Ca, CP, and AME levels. The result showed that 6 out of 13 of our test treatments gave improved FCR compared to the control treatment (p = 0.017). Dietary treatments did not affect overall hen weight and serum Ca and egg quality at week 10, except for the lower yolk color score in the control treatment (p = 0.002). Hens in the experimental treatment, with calcium levels of 1.6% and 6.6%, crude protein (CP) levels of 19.6% and 18.4%, and AME content of 12.4 MJ/kg and 10.8 MJ/kg in the AM and PM diet, respectively, showed the highest apparent protein digestibility (56.6%) compared to the control group (p < 0.05). Similarly, hens receiving a treatment containing calcium at 3.3% and 4.9%, CP at 21% and 17%, and AME at 12.4 MJ/kg and 10.8 MJ/kg in the AM and PM diet, respectively, achieved the highest calcium digestibility (62.13%), while the control treatment yielded the lowest calcium digestibility (p < 0.05). After analyzing the data using the Box-Behnken response surface methodology, we found that (21/17)% CP, (3.3/4.9)% Ca, and (12/11.12) MJ/kg energy in the AM/PM diet gave the optimum performance in terms of lower feed cost and better feed efficiency. The data of AM:PM intake demonstrate that selective feeding occurs in between treatments (p < 0.001) and the degree of selection depends on the difference between the level of nutrients in AM and PM diet. This study revealed that when optimized, AM/PM feeding improves feed efficiency and egg quality of laying hens.

Effects of dietary calcium and microbial phytase on the bioavailability of two sources of zinc in broilers

1. The objective of this study was to test the effect of microbial phytase and calcium (Ca) levels on the Zn bioavailability depending on the Zn source.2. A total of 144, one-day-old broilers received a diet containing 40 mg Zn/kg for 1 week. They were then assigned to one of the eight experimental treatments during 2 weeks. Diets contained 27 mg native Zn and were formulated according to a 2 × 2 × 2 factorial design with two added Zn sources (23 mg Zn/kg), sulphate (ZnSO4) or oxide (ZnO); two dietary Ca levels of either 6 (low) or 10 g/kg (moderate); and two microbial phytase levels, of either 0 or 750 phytase unit/kg.3. Moderate Ca plus phytase improved body weight gain (BWG) and low Ca level without microbial phytase decreased tibia weight (Ca × Phy; p = 0.049). Zinc oxide resulted in a higher tibia development (i.e. tibia weight and length; p < 0.05) and BWG (p = 0.009) and lower FCR (p < 0.001) compared to ZnSO4.4. Phytase improved tibia Zn concentration especially in birds given ZnSO4 compared to ZnO (Zn × Phy; p = 0.049). Moderate Ca diets improved tibial characteristics and Zn deposition compared to low Ca diets (p < 0.05).5. Soluble Zn in the gizzard increased in the presence of phytase (p = 0.011), while higher dietary Ca reduced this in birds receiving ZnO (p = 0.004). In the jejunum, Zn solubility was higher with phytase (p = 0.008).6. Under the conditions of this study, dietary levels of Ca and microbial phytase affect Zn availability in broilers more than the Zn source.

Effects of L-arginine, guanidinoacetic acid and L-citrulline supplementation in reduced-protein diets on bone morphology and mineralization of laying hens

The alterations in feed ingredients and the nutrient matrix to produce reduced-protein diets may affect bone morphology and mineralization in laying hens. This study was implemented to determine the effects of L-arginine (Arg), guanidinoacetic acid (GAA), and L-citrulline (Cit) supplementation to Arg-deficient reduced-protein diets on bone morphology, strength, and mineralization status of laying hens. Individually housed Hy-Line Brown laying hens were evenly distributed to five dietary treatments with 25 replicates per treatment from 20 to 40 wk of age. Treatments consisted of a standard protein diet (17% crude protein, SP), a reduced-protein diet deficient in Arg (13% crude protein, RP), and RP supplemented with Arg (0.35% Arg, RP-Arg), GAA (0.46% GAA equivalent to 0.35% Arg, RP-GAA), or Cit (0.35% Cit equivalent to 0.35% Arg, RP-Cit) to reach the Arg level of SP diets. Birds fed the SP diet had similar bone weight, ash, length, width, Seedor index, breaking strength, and serum mineral concentration, but higher toe B level (P < 0.001) compared to those fed the RP diet at wk 40. Birds fed the SP diet consumed more but also excreted more K and B compared to those fed the RP diet (P < 0.01). Birds fed the SP diet had lower Cu digestibility (P = 0.01) and higher B retention (P < 0.01) compared to those offered the RP diet. Supplementation of Arg, GAA, and Cit to the RP diet increased relative femur weight and length (P < 0.001). Citrulline supplementation also increased relative tibia and femur ash, and Zn digestibility (P < 0.05). Supplementation of GAA to the RP diet decreased serum Ca, P, and Mg levels, decreased tibia Fe and Mg levels and toe Mg level, but increased Al, Fe, Zn, and Mn digestibility (P < 0.05). The current findings demonstrated the capacity of laying hens to adapt to low mineral intake by increasing mineral utilization. Overall, bone morphology and breaking strength, and serum mineral level in laying hens were not influenced by dietary CP levels. Dietary Arg, GAA, or Cit supplementation were effective in improving bone morphology and mineralization in laying hens fed Arg-deficient RP diets.

Osteoimmunology: A Link between Gastrointestinal Diseases and Skeletal Health in Chickens

Bone serves as a multifunctional organ in avian species, giving structural integrity to the body, aiding locomotion and flight, regulating mineral homeostasis, and supplementing calcium for eggshell formation. Furthermore, immune cells originate and reside in the bone marrow, sharing a milieu with bone cells, indicating a potential interaction in functions. In avian species, the prevalence of gastrointestinal diseases can alter the growth and the immune response, which costs a great fortune to the poultry industry. Previous studies have shown that coccidiosis and necrotic enteritis can dramatically reduce bone quality as well. However, possible mechanisms on how bone quality is influenced by these disease conditions have not yet been completely understood, other than the reduced feed intake. On the other hand, several mediators of the immune response, such as chemokines and cytokines, play a vital role in the differentiation and activation of osteoclasts responsible for bone resorption and osteoblasts for bone formation. In the case of Eimeria spp./Clostridium perfringens coinfection, these mediators are upregulated. One possible mechanism for accelerated bone loss after gastrointestinal illnesses might be immune-mediated osteoclastogenesis via cytokines-RANKL-mediated pathways. This review article thus focuses on osteoimmunological pathways and the interaction between host immune responses and bone biology in gastrointestinal diseases like coccidiosis and necrotic enteritis affecting skeletal health.

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

Calcium has the capacity to interact with phytate-P to form Ca-phytate complexes and decrease the ability of exogenous phytase to degrade phytic acid. This study investigated the hypothesis that high dietary Ca would impair gut permeability, phytate esters (inositol x-phosphate, IPx: IP3, IP4, IP5, and IP6) degradation, jejunal gene expression, and intestinal morphology. Ross 308 day-old male broilers (n = 768) were distributed into 48-floor pens each housing 16 birds in a factorial arrangement. Factors were NE challenge-no or yes; phytase level of 500 or 1,500 FTU/kg, and Ca level 0.6 or 1.0% starter, 0.5 or 0.9% grower, 0.4 or 0.8% finisher with available P in each phase. Challenged birds were gavaged with 3 field strains of Eimeria on day 9 and 108 CFU per mL of Clostridium perfringens Strain EHE-NE18 on day 14 and day 15. A phytase × Ca interaction was observed in the ileum for IP3 (P < 0.01), IP4 (P < 0.05), and IP6 (P < 0.01). The IP3 and IP4 concentrations were similar for both doses of phytase in the presence of low Ca, but with high Ca, both increased significantly but to a greater extent when the high dose of phytase was used. While IP6 concentrations were low and similar between both doses of phytase at low Ca levels, increasing dietary Ca levels increased IP6 concentrations regardless of phytase dose, but the effect was greater in the low phytase diet. A phytase × Ca interaction was detected for vitamin D receptor (VDR) (P < 0.05) expression where bird fed low phytase and low Ca recorded the highest expression of VDR, all other treatments being equivalent. The challenge decreased crypt depth to villus height ratio (P < 0.001). Challenge birds had higher fluorescein isothiocyanate dextran (P < 0.05) in blood compared with unchallenged birds. Thus, high Ca and high phytase, while not the best for IP6 destruction, did not lead to huge reductions in indicators of gut health.