An experiment was conducted to determine the digestible calcium (Ca) and digestible phosphorous (P) requirements of 25 to 35-day-old broiler chickens. Fifteen corn-soybean meal-based diets containing 2.0, 2.5, 3.0, 3.5, and 4.0 g/kg standardized ileal digestible (SID) Ca and 2.5, 3.5, and 4.5 g/kg SID P were fed to broilers from d 25 to 35 post-hatch. Each experimental diet was randomly allocated to 6 replicate cages (8 birds per cage). Body weight and feed intake were recorded, and the feed conversion ratio was calculated. On d 35, birds were euthanized to collect the ileal digesta, tibia, and carcass for the determination of ileal Ca, and P digestibility, concentrations of ash, Ca, and P in tibia and the retention of Ca and P in the carcass. Titanium dioxide (5.0 g/kg) was included in all diets as an indigestible indicator for the ileal digestibility measurement. Feed intake and total excreta output were measured during the last 4 d of the experimental period for the measurement of apparent total tract retention of Ca and P. Fixed effects of the experiment were dietary concentrations of SID Ca and SID P and their interaction. If the interaction or main effects were significant (P < 0.05), the parameter estimates for second-order response surface model (RSM) were determined using General Linear Model procedure of SAS. The maximum response was not predicted for most of the parameters (including growth performance and tibia) as the Ca effect was linear which indicated that the highest level of Ca employed in the study may have not been high enough. The requirement of dietary SID Ca for maximization of these parameters, therefore, depends on the dietary SID P concentration when the dietary SID Ca is within 2.0 to 4.0 g/kg. However, based on the factorial analysis, the highest weight gain was observed at 3.5 g/kg SID P and 3.5 g/kg SID Ca concentrations. Tibia ash was higher in birds fed 4.5 g/kg SID P and was unaffected by dietary SID Ca concentrations. However, based on overall findings, a combination of 3.5 g/kg SID P and 3.0-3.5 g/kg SID Ca may be recommended for the optimum tibia ash. The recommended SID Ca requirements (at 3.5 g/kg SID P) for weight gain (3.5 g/kg or 6.4 g/kg total Ca) and tibia ash (3.0-3.5 g/kg or 5.5-6.4 g/kg total Ca) are lower than the current Ca recommendations (7.8 g/kg total Ca equivalent to 4.25 g/kg SID Ca; Ross, 2019) for broiler finishers, suggesting possible excess of Ca in diets formulated based on the current recommendation.
Calcium is chelated by phytic acid and forms phytate-mineral complexes reducing Ca availability and the ability of phytase to hydrolyze phytate. An increased Ca concentration in the gut favors the activity of Clostridium perfringens (C. perfringens). Therefore, it was hypothesized that high dietary calcium with high dietary phytase would decrease serum Ca and P and bone mineralization during necrotic enteritis occurrence. A total of 768 one-day-old Ross 308 male chicks were randomly allocated to 8 treatments with 6 replicate pens, each housing 16 birds. A 2 × 2 × 2 factorial arrangement of treatments was applied: dietary Ca (0.6 or 1.0%), phytase (500 or 1,500 FTU/kg), and challenge (no or yes). Half of the birds (384) were challenged with Eimeria spp. on day 9 and C. perfringens strain EHE-NE18 on day 14 and 15. Blood was collected from 2 birds per pen to determine Ca, P, and parathyroid hormone in the serum. The middle toe, tibia, and femur were excised from 2 birds per pen on day 16 and 29 for determination of ash, breaking strength (BS), and mineral concentration. The challenge decreased (P < 0.05) serum Ca
AbstractAs the simultaneous use of carbohydrases and phytases gains momentum it is imperative that formulators understand the magnitude of additivity of effect to allow for appropriate modification to diet nutrient balance. Though carbohydrases and phytases are often thought of as pronutrients with energy, calcium and phosphorus value, within the scientific literature there are dozens of papers on the effect of these enzymes on ileal amino acid digestibility coefficients. The effect of enzymes on ileal amino acid digestibility is instructive as patterns of response allow speculation as to mode of action and likely additivity of admixtures. A review of the scientific literature has revealed that whilst xylanases and phytases may be considered to be broadly additive in effect, on an individual amino acid basis this effect ranges from sub-additive (e.g. threonine) to synergistic (e.g. arginine). Importantly, the mean response to both xylanase and phytase for ileal amino acid digestibility can be predicted (R2=0.65 and 0.56 respectively) by polynomial equations based only on the nutritional value of the control diet. The fact that control diets with an inherently high digestibility respond poorly to enzymes explains why the use of a second enzyme will likely yield a lesser response when used on top of another, since the former has already improved digestibility characteristics. The implications of these responses, as well as suggested mechanisms of action, are discussed within practical diet formulation constraints.Keywords:: phytatecarbohydraseendogenous lossesamino acidsenergypoultry
Heat stress (HS) is one of the most challenging stressors to poultry production sustainability. The adverse effects of HS range from feed intake and growth depression to alteration of meat quality and safety. As phytase supplementation is known to improve nutrient utilization and consequently growth, we undertook the present study to evaluate the effects of dietary phytase on growth and meat quality in heat-stressed broilers. A total of 720 day-old hatch Cobb 500 chicks were assigned to 24 pens within controlled environmental chambers and fed three diets: Negative Control (NC), Positive Control (PC), and NC diet supplemented with 2000 phytase units (FTU)/kg) of quantum blue (QB). On day 29, birds were exposed to two environmental conditions: thermoneutral (TN, 25 °C) or cyclic heat stress (HS, 35 °C, 8 h/d from 9 a.m. to 5 p.m.) in a 3 × 2 factorial design. Feed intake (FI), water consumption (WI), body weight (BW), and mortality were recorded. On day 42, birds were processed, carcass parts were weighed, and meat quality was assessed. Breast tissues were collected for determining the expression of target genes by real-time quantitative PCR using the 2-ΔΔCt method. HS significantly increased core body temperature, reduced feed intake and BW, increased water intake (WI), elevated blood parameters (pH, SO2, and iCa), and decreased blood pCO2. HS reduced the incidence of woody breast (WB) and white striping (WS), significantly decreased drip loss, and increased both 4- and 24-h postmortem pH. Instrumental L* and b* values were reduced (p < 0.05) by the environmental temperature at both 4- and 24-h postmortem. QB supplementation reduced birds' core body temperature induced by HS and improved the FCR and water conversion ratio (WCR) by 1- and 0.5-point, respectively, compared to PC under HS. QB increased blood SO2 and reduced the severity of WB and WS under TN conditions, but it increased it under an HS environment. The abovementioned effects were probably mediated through the modulation of monocarboxylate transporter 1, heat shock protein 70, mitogen-activated protein kinase, and/or glutathione peroxidase 1 gene expression, however, further mechanistic studies are warranted. In summary, QB supplementation improved growth performance and reduced muscle myopathy incidence under TN conditions. Under HS conditions, however, QB improved growth performance but increased the incidence of muscle myopathies. Therefore, further QB titration studies are needed.
Abstract The objective of this experiment was to test the hypothesis that the concentration of Ca in diets fed to late gestating sows affects the apparent total tract digestibility (ATTD) and retention of Ca and P, serum concentrations of Ca and P, hormones, and blood biomarkers for bone formation and resorption. Thirty-six sows (average parity = 2.8) were housed in metabolism crates from day 91 to day 104 of gestation and fed 1 of 4 experimental diets containing 25, 50, 75, or 100% of the requirement for Ca. All diets met the requirement for P. The initial 5 d of each period were the adaptation period, which was followed by 4 d of quantitative collection of feces and urine. At the end of the collection period, a blood sample was collected from all sows. Results indicated that feed intake, weights of dried fecal and urine samples, and the ATTD of DM were not affected by dietary Ca, but ATTD of Ca increased (quadratic, P < 0.05) as Ca in diets increased. Urine Ca output was not affected by dietary Ca, but Ca retention increased (quadratic, P < 0.05) as Ca intake increased. Fecal P output increased (linear, P < 0.001) as dietary Ca increased, which resulted in a linear decrease (P < 0.001) in the ATTD of P. Urine P output also decreased (linear, P < 0.001) as dietary Ca increased, but P retention increased (linear, P < 0.05). Regressing the apparent total tract digestible Ca against dietary Ca intake resulted in a regression line with a slope of 0.33, indicating that true total tract digestibility of Ca in calcium carbonate was 33%. Serum concentrations of Ca and P and estrogen, calcitonin, and parathyroid hormone were not affected by dietary Ca. Serum concentration of carboxyterminal cross-linked telopeptide of type I collagen (CTX-I) decreased (linear, P < 0.05) as dietary Ca increased, which is a result of reduced bone resorption as dietary Ca increased. Serum bone-specific alkaline phosphatase tended to decrease (linear, P < 0.10) as Ca in diets increased, but the concentration of osteocalcin (OC) in serum was not affected by dietary Ca. The ratio between OC and CTX-I tended to increase (P < 0.10) as dietary Ca increased, which indicated that there was more bone formation than resorption in sows as dietary Ca increased. In conclusion, P digestibility in late gestating sows decreased, but retention of P increased, as dietary Ca increased from inadequate to adequate levels and blood biomarkers for bone resorption changed as Ca and P retention increased.
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