Calcium tolerance of growing chickens: effect of ratio of dietary calcium to available phosphorus

Impacts of phytase and coccidial vaccine on growth performance, nutrient digestibility, bone development, and intestinal gene expression of broilers fed a nutrient reduced diet

An experiment was conducted to evaluate effects of phytase and coccidial vaccine on growth performance, bone ash, bone 3-D microstructure, nutrient digestibility, and gene expression of intestinal biomarkers in broilers fed a regular or nutrient-reduced diet. The experiment was conducted in a 2 × 4 factorial arrangement with 6 replicates per treatment and 10 birds per replicate. Two main factors were coccidial vaccine and dietary treatments. The dietary treatments included: 1) a positive control (PC; normal nutrient levels); 2) a negative control (NC; with a reduction of 0.15% of Ca and avP and 5% of essential amino acid (EAA) and crude protein relative to PC); 3) NC + 500 FTU/kg of phytase; and 4) NC + 1,500 FTU/kg of phytase. No interaction effect of phytase and coccidial vaccine on growth performance, bone ash, and apparent ileal digestibility (AID) was observed. For the main effect, birds fed the NC diet showed lower (P = 0.007) BWG during d 0 to 21 compared to PC birds, whereas supplementing 500 or 1,500 FTU/kg phytase increased BWG to the similar level to the PC. During d 0 to 21, vaccinated birds had a lower (P < 0.001) FI and better (P = 0.045) FCR compared to unvaccinated birds. Birds fed the NC diet resulted a decrease in tibia fat-free dry bone weight (P = 0.012), ash weight (P = 0.005), ash percentage (P < 0.001), and ash concentration (P = 0.019) compared to the PC group at d 21, whereas supplementing phytase at 500 or 1,500 FTU/kg in NC diet was able to improve these bone parameters to the similar level to the PC; however, vaccination did not have any effect on bone ash. Similarly, birds fed with the NC diet showed had significant lower bone microstructure levels including bone volume, bone mineral density, and bone mineral content (P < 0.001), and supplementing phytase at 1,500 FTU/kg improved these parameters. Vaccination improved AID of nitrogen (P < 0.001). Birds from the NC and both phytase supplementation groups had a higher (P = 0.001) AID of Ca compared to the PC. Supplementing phytase at 500 FTU/kg or 1,500 FTU/kg improved (P < 0.001) AID of P compared to the NC. Additionally, the NC had a lower AID of DM than the PC, whereas supplementing phytase at 500 FTU/kg or 1,500 FTU/kg improved DM digestibility (P = 0.0299). In conclusion, supplementation of phytase at 500 or 1,500 FTU/kg improved growth performance, bone mineralization, and nutrient digestibility regardless of vaccination, with a more pronounced effect when supplementing phytase at 1,500 FTU/kg.

Determination of the standardized ileal digestible calcium requirement of male Arbor Acres Plus broilers from day 25 to 42 post-hatch

An experiment was conducted to determine the standardized ileal digestible (SID) Ca requirement of Arbor Acres Plus male broilers from d 25 to 42 post-hatch. Broilers were obtained at hatch, placed in floor pens, and fed a nutrient adequate diet until d 24 post-hatch. On d 25, twelve hundred birds were weighed and allocated to one of 4 treatments. There were 25 birds per pen and 12 pens per diet. The diets were formulated to contain 0.46, 0.35, 0.24, or 0.13% SID Ca. Available P (avP) was 0.39% in all diets, including 0.16% avP expected from 2,500 FYT/kg of phytase. The SID Ca requirement was estimated using nonlinear models, including quadratic, straight broken-line, and quadratic broken-line. There was no effect of SID Ca on feed intake, body weight gain, feed conversion ratio, or livability. Tibia ash percent was greatest in birds fed 0.35% SID Ca and lowest in birds fed 0.13% SID Ca (quadratic, P = 0.063). Apparent ileal digestibility (AID) of Ca was highest in birds fed the diets containing 0.13% SID Ca and decreased (quadratic, P = 0.014) as dietary SID Ca increased to 0.46%. Apparent digested Ca was highest in birds fed 0.35% SID Ca and lowest in birds fed 0.13% SID Ca (quadratic, P = 0.005). Decreasing the concentration of SID Ca in the diet from 0.46 to 0.13% (P < 0.0001) increased the AID of P and apparent digested P. Litter N or P were lowest in birds fed 0.35% SID Ca and increased (quadratic, P ≤ 0.05) as dietary SID Ca decreased to 0.13%. Non-linear equations, developed using tibia ash percent, digested Ca, or litter P, estimate the SID Ca requirement of Arbor Acres Plus broilers from d 25 to 42 was 0.37, 0.35, or 0.35%, respectively. This corresponds to an SID Ca to available P ratio of 0.95 to 0.90.

A Comprehensive Study of the Microbiome, Resistome, and Physical and Chemical Characteristics of Chicken Waste from Intensive Farms

The application of chicken waste to farmland could be detrimental to public health. It may contribute to the dissemination of antibiotic-resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) from feces and their subsequent entry into the food chain. The present study analyzes the metagenome and resistome of chicken manure and litter obtained from a commercial chicken farm in Poland. ARB were isolated, identified, and screened for antibiogram fingerprints using standard microbiological and molecular methods. The physicochemical properties of the chicken waste were also determined. ARGs, integrons, and mobile genetic elements (MGE) in chicken waste were analyzed using high-throughput SmartChip qPCR. The results confirm the presence of many ARGs, probably located in MGE, which can be transferred to other bacteria. Potentially pathogenic or opportunistic microorganisms and phytopathogens were isolated. More than 50% of the isolated strains were classified as being multi-drug resistant, and the remainder were resistant to at least one antibiotic class; these pose a real risk of entering the groundwater and contaminating the surrounding environment. Our results indicate that while chicken manure can be sufficient sources of the nutrients essential for plant growth, its microbiological aspects make this material highly dangerous to the environment.

Dietary calcium requirements of broilers fed a conventional corn-soybean meal diet from 1 to 21 days of age

Background

The current calcium (Ca) recommendation for broilers is primarily based on studies conducted more than 30 years ago with birds of markedly different productive potentials from those which exist today. And the response indicators in these studies are mainly growth performance and bone ash percentage. Therefore, the present study was carried out to investigate the effect of dietary Ca level on growth performance, serum parameters, bone characteristics and Ca metabolism-related gene expressions, so as to estimate dietary Ca requirements of broilers fed a conventional corn-soybean meal diet from 1 to 21 days of age.

Methods

A total of 420 1-day-old Arbor Acres male broilers were randomly assigned to 1 of 7 treatments with 6 replicates (10 birds per cage) and fed the corn-soybean meal diets containing 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 1.10% or 1.20% Ca for 21 days. Each diet contained the constant non-phytate phosphorus content of about 0.39%.

Results

The average daily gain decreased linearly (P < 0.001) as dietary Ca level increased. The serum and tibia alkaline phosphatase (ALP) activities, tibia bone mineral density (BMD), middle toe BMD, tibia ash percentage, tibia breaking strength, and tibia ALP protein expression level were affected (P < 0.05) by dietary Ca level, and showed significant quadratic responses (P < 0.02) to dietary Ca levels. The estimates of dietary Ca requirements were 0.80 to 1.00% based on the best fitted broken-line or quadratic models (P < 0.03) of the above serum and bone parameters, respectively.

Conclusions

The results from the present study indicate that the Ca requirements would be about 0.60% to obtain the best growth rate, and 1.00% to meet all of the Ca metabolisms and bone development of broilers fed a conventional corn-soybean meal diet from 1 to 21 days of age.

The effects of dietary calcium and phosphorus level, and feed form during rearing on growth performance, bone traits and egg production in brown egg-type pullets from 0 to 32 weeks of age

In a 3 × 2 factorial arrangement, effects of feed form (crumbles (CWS), mash (MWS), both with inclusion of 3% finely ground wheat straw, or crumbles with inclusion of 3% oat hulls (COH)), and dietary Ca and P (high and low Ca-P) from 0 to 16 wk of age were studied on growth performance, bone characteristics, and gizzard development of egg-type pullets. The cross-over effect of feeding strategy during rearing on laying performance and egg shell quality was studied from 19 to 32 wk of age. From 0 to 16 wk, ADG, ADFI, and feed conversion ratio (FCR) were improved with CWS and COH compared to MWS, but ADG and FCR were improved with MWS compared to CWS and COH from 11 to 16 wk. Uniformity of BW till 11 wk, and tibia breaking strength at 6 and 16 wk were higher with CWS and COH compared to MWS. Tibia ash content at 11 wk and relative empty proventriculus + gizzard weight (EPG) were lower with CWS and COH compared to MWS, also relative EPG at 11 and 16 wk was higher with COH compared to CWS. At 25 wk BW was lower with MWS compared to CWS and COH, but BW was equal for all treatments at 32 wk. The FCR for egg production was improved with COH compared to MWS. Egg shell parameters were not affected by feed form during rearing. Low Ca-P decreased BW uniformity at 6 wk, relative keel bone weight and ash content at 11 wk, tibia ash content at 11 and 16 wk, increased relative EPG at 6 wk, and improved egg shell quality at 32 wk of age. It was concluded that feeding CWS and COH compared to MWS increased growth performance, but had no clear cross-over effect on egg production. Low dietary Ca-P led to a lower bone mineralization during rearing, nevertheless improved egg shell quality at 32 wk.

The effect of reducing dietary calcium in prestarter diets (0-4 D) on growth performance of broiler chickens, tibia characteristics, and calcium and phosphorus concentration in blood

During the incubation period, the Ca-to-P weight (mg/mg) ratio in the yolk increases from 0.26 on day 0 to 0.92 on day 17.5 and to 2.9 at hatch. Moreover, the absolute Ca content in the yolk increases by 41%, whereas P content decreases by 87%, from day 0 to the day of hatching. Thus, at hatch and during the first days after hatching, there are high reserves of Ca relative to P in the residual egg yolk, risking hypercalcemia and hypophosphatemia. A growth performance study was conducted to explore the effects of reducing dietary Ca content in the prestarter phase (0–4 D) on BW and bone mineral deposition during the first days after hatch and at market weight (day 37). Four prestarter (0–4 D) diets were formulated to have 0.4, 0.6, 0.8, and 1.0% Ca content. After the prestarter phase, all birds were fed with the same commercial diets based on a 3-phase feeding program (starter, grower, and finisher). Growth performance (BW, ADG, ADFI, and feed conversion ratio [FCR]) was monitored throughout the study, and blood and tibia bone samples were collected on specific days. On day 4, BW and ADG decreased with dietary Ca contents higher than 0.6% (P < 0.05), but there were no differences in BW on day 14 onward (P > 0.10). For the overall study (0–37 D), there were no differences in ADG and ADFI, but the FCR decreased with lower Ca contents (P < 0.05). On day 4, there were no differences in blood plasma Ca concentration, but P concentration increased in the group treated with diet containing 0.4% Ca compared with the groups treated with diets containing 0.6 and 0.8% Ca (P < 0.05). Tibia ash content decreased in the group treated with diet containing 0.4% Ca (P < 0.05) compared with all other treatments at the end of the prestarter phase. Tibia ash content and tibia breaking strength, on day 37, were not different among the treatments (P > 0.10). In conclusion, during the prestarter phase, BW increased with dietary Ca contents lower than 0.6%, most likely improving Ca–P balance; bone mineral deposition was reduced in this period. On feeding with a diet containing higher Ca content, bone mineral content was rapidly recovered.

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

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+ in birds regardless of dietary Ca level (day 16). There was a challenge × Ca interaction (P < 0.05) for tibial BS (day 16), with challenge being more severe in birds fed high Ca than low Ca diets. A challenge × phytase interaction (P < 0.05) was present for femur ash (day 16), with high phytase only increasing ash in challenged birds. The challenge decreased (P < 0.05) the BS of femur and tibia at each time point. Birds fed high dietary Ca had lower tibial Mg (P < 0.001), Fe (P < 0.001), Na (P < 0.001), and Zn (P < 0.05) concentrations (day 29). Altogether, high dietary Ca and phytase improved bone mineralization showing that attention to Ca and P nutrition and phytase matrix values is warranted when high levels of phytase are used.

Hydrolysis of phytate to its lower esters can influence the growth performance and nutrient utilization of broilers with regular or super doses of phytase

The aim of the study was to observe the effects of dietary available phosphorus (aP) and calcium (Ca), with regular or super doses of phytase, on phytate hydrolysis and subsequent influences on broiler growth performance and nutrient utilization. In a 2 × 3 factorial design, 384 Ross-308 broilers were allocated to one of 6 dietary treatments with 8 replicates in a randomized complete block design for 21 days. Diets were nutritionally adequate (positive control, PC) or marginally deficient in aP and Ca (negative control, NC), with 0, 500 or 1,500 FTU/kg phytase. Bird and feed weights were recorded on d 0 and 21, excreta were collected on d 19 and 20, and gizzard and ileal contents were collected on d 21. Body weight gain (P < 0.01) increased linearly with phytase in the PC and quadratically in the NC. There was an interactive effect on ileal DM, N, and P utilization, increasing quadratically with phytase supplementation in the NC, but there was no phytase influence in the PC (P < 0.05). Phytase linearly increased copper (P < 0.001) and linearly decreased Ca (P < 0.05) utilization in the ileum. Phytase decreased ileal (IPx, inositol x-phosphate) IP6 and IP5 and increased inositol (quadratic, P < 0.001) but had no effect on IP4 or IP3. The influence of the dietary aP was more apparent on the hydrolysis of phytate and phytate esters after the ileum, with increasing (linear and quadratic, P < 0.05) IP4 and IP3 content in the excreta of birds fed the NC or PC when phytase was added. Phytate hydrolysis improves the growth potential of birds fed NC diets, allowing them to match the growth performance of birds fed PC diets and improve nutrient utilization. These results indicate that dietary Ca and aP concentrations can be reduced when phytase is supplemented. It also may be beneficial to apply the enzyme nutrient matrix to other nutrients in the diet to maintain an optimal balance of nutrients in the digesta.

Methodology affects measures of phosphorus availability in growing broilers: Effects of calcium feeding strategy and dietary adaptation period length on true ileal phosphorus digestibility and predicted endogenous phosphorus losses1

An experiment was conducted to determine the effects of Ca feeding strategy and dietary adaptation period length (DAPL) on the apparent ileal P digestibility (AIPD) and apparent ileal myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (IP6) hydrolysis (AIIP6H) of corn titration diets. Nine hundred sixty Ross × Ross 708 male broiler chicks were placed into 80 battery cages. Broilers received a common starter diet until 18 d of age and then were fed one of 10 experimental treatments from 19 to 21 d of age. Nine diets were formulated to evaluate 5 corn inclusion concentrations (15, 30, 45, 60, or 75%) and 2 Ca feeding strategies (fixed at 0.35% or 1.4:1 Ca:P) after 3 DAPL (zero, 24, and 48 h). As a control for DAPL, one treatment group received the common starter diet for the duration of the experiment. Broilers consuming the control diet had higher (P < 0.001) BW gain and feed intake than broilers fed the corn titration diets. Apparent ileal P digestibility of the control diet was affected (P = 0.038) by DAPL. For diets formulated with a 1.4:1 Ca:P ratio, negative linear effects (P < 0.05) on AIPD and AIIP6H were observed with increasing corn. Conversely, for diets formulated with 0.35% Ca, positive linear effects (P < 0.05) were measured for AIPD after a 48 DAPL while no linear or quadratic effects (P > 0.05) were measured for AIPD or AIIP6H for other DAPL. Broilers fed diets formulated with 1.4:1 Ca:P had variable (P < 0.05) true ileal P digestibility (TIPD; 32.2, 15.1, and 35.4%) and negative endogenous P losses (EPL; -190, -499, and -262 mg/kg DM intake) for zero, 24, and 48 h DAPL, respectively. Conversely, TIPD values (41.2, 39.1, and 47.3%) were similar (P > 0.05) and EPL were positive (102, 197, and 154 mg/kg DM intake), regardless of DAPL, for broilers fed diets formulated with 0.35% Ca. These data demonstrated that formulating diets with a 1.4:1 Ca:P ratio affected AIPD of the titration diets, shifting the regression line and predicted negative EPL and an underestimation of TIPD.

Calcium and phosphorus metabolism and nutrition of poultry: are current diets formulated in excess?

Calcium (Ca) and phosphorus (P) are important nutrients in poultry diet formulations. In the present review, we discuss recent advances in our understanding of the metabolism of Ca and P in poultry. Recent data are provided in support of the proposition that current poultry diets are formulated in excess for Ca and P. The quantities of Ca and P available for metabolism reflect rates of intestinal absorption, bone accretion and resorption, glomerular filtration, renal tubular reabsorption, and intestinal endogenous losses. Ca and P homeostasis is largely under endocrine control. Parathyroid hormone and the hormonal form of vitamin D3 are the two hormones credited with this role. However, a novel hormonal axis involving Fibroblast Growth Factor 23 and Klotho has been recently delineated, which, in conjunction with parathyroid hormone and vitamin D3, tightly regulates Ca and P homeostasis. Recent studies have suggested that current commercial diets for both broilers and layers contain excess Ca and P, the content of which could be reduced without affecting production or bird welfare. The challenge in reducing Ca and P concentrations in poultry diets is the uncertainty about what concentrations of Ca and P can be fed without compromising bird welfare. This is because there are limited data on the available P and Ca concentrations in poultry feedstuffs determined biologically. This is further complicated by the need for agreement on evaluation systems for evaluation of Ca and P bioavailability. We conclude that direct ileal or pre-caecal digestible Ca and P values are preferred.

Phosphorus utilization in finishing broiler chickens: effects of dietary calcium and microbial phytase

A decrease in dietary P, especially in finishing broilers (21 to 38 d old), is a crucial issue in poultry production from an environmental and economic point of view. Nevertheless, P must be considered together with other dietary components such as Ca and microbial phytase. Different corn and soybean meal-based diets varying in Ca [low (LCa) 0.37, medium (MCa) 0.57, and high (HCa) 0.77%], and nonphytate P [nPP; low (LnPP) 0.18 and high (HnPP) 0.32%] content were tested with and without microbial phytase [0 or 500 phytase units (FTU)/kg]. Feed intake, BW gain, bone mineralization, and mineral retention were examined in 144 Ross PM3 broilers (22 to 38 d old) reared in individual cages. Growth performance was not significantly affected by the treatments. Nevertheless, a numerical decrease of ADG and ADFI was observed in HCa-LnPP and LCa-HnPP associated with an increase of feed conversion ratio. Decreased dietary Ca reduced tibia ash content (Ca, linear: P < 0.001; quadratic: P = 0.034) and tibia ash weight for the highest level of nPP (Ca × nPP; P = 0.035). In parallel, increasing dietary Ca reduced the flow of retained P (P = 0.022) but also tibia ash weight in LnPP diets (Ca × nPP; P = 0.035). The responses of the animals in terms of tibia ash content and P retention were improved by the addition of microbial phytase especially for the lowest P diets (nPP × phytase, P = 0.021 and P = 0.009; respectively). Phytase increased dry tibia weight, bone breaking strength, and tibia diameter in broilers fed the highest Ca diets (Ca × phytase; P < 0.05). We conclude that is possible to decrease P levels in finishing broilers, if the Ca content is appropriate. Nevertheless, decreasing the dietary P and Ca cannot allow a maximization of bone mineralization, but the optimal threshold remains to be determined.

Effects of microbial phytase supplementation on mineral utilization and serum enzyme activities in broiler chicks fed different levels of phosphorus

An experiment was conducted to study the effect of microbial phytase (Natuphos 500) supplementation in chicks (0 to 6 wk of age) fed different levels of nonphytate phosphorus (nPP) on performance, mineral retention, bone and plasma minerals and serum enzyme activities. Data were analyzed as a 2 x 2 factorial arrangement with two levels of nPP for age periods of 1-d-old to 3 wk (0.35 and 0.22%) and 3 to 6 wk (0.27 and 0.14%) and two levels of phytase (0 and 500 U/kg) in each period. A positive control, adequate in nPP and Ca without phytase, was used. The low-nPP diets caused a negative effect on the performance (P < 0.05) compared to the normalnPP diet. Phytase had a favorable effect on weight gain at 3 wk (P < 0.004) and 6 wk (P < 0.0475) of age and on feed consumption only at 3 wk (P < 0.0106). Feed efficiency was not affected at any stage by addition of phytase. Performances of chicks fed with 0.35 and 0.27% nPP and phytase were comparable to those obtained with the normal-nPP diets. Decreasing nPP content in the diet increased (P < 0.0001) P retention at 3 and 6 wk of age, increased Mg retention at 6 wk, and decreased (P < 0.0001) Ca and Zn retentions at 3 and 6 wk, respectively. Phytase supplementation increased (P < 0.0001) Ca, P, Mg, and Zn retention at 3 and 6 wk of age. Likewise, the decrease in nPP content in the diet caused a significant reduction of tibia ash (P < 0.0023) and Mg content (P < 0.0001) in tibia ash and reduced liver (P < 0.0240), spleen (P < 0.0176), and tibia (P < 0.0001) weights. Similarly, Ca (P < 0.0369) and Zn (P < 0.0181) contents in tibia ash were increased in response to decreasing nPP levels in the diet. Phytase supplementation increased tibia weight (P < 0.0019), tibia ash (P < 0.0021), and Mg (P < 0.0339) and Zn (P < 0.0353) concentrations and reduced (P < 0.0161) the relative liver weight. By decreasing nPP levels in the diet, plasma Ca (P < 0.0001), Mg (P < 0.0001) and Zn (P < 0.0048) concentrations, and alkaline phosphatase (ALP) activity (P < 0.0299) increased, and plasma P content (P < 0.0001), aspartate aminotransferase (AST) activity (P < 0.0001), and total protein (TP) content (P < 0.0050) were reduced. Phytase supplementation increased plasma P level (P < 0.0001) and serum AST activity (P < 0.0049), reduced plasma Ca (P < 0.0001) and Mg (P < 0.0050) contents, and reduced serum alanine aminotransferase (ALT) (P < 0.0048), ALP (P < 0.0001) and lactate dehydrogenase (LDH) (P < 0.0192) activities. Plasma Zn was not affected by phytase supplementation. These results demonstrated that microbial phytase supplementation to low-P diets improved performance; P, Ca, Mg, and Zn use; and tibia weight and relative liver weight in broiler chickens. Likewise, serum AST, ALT, ALP, and LDH activities, as well as TP concentration, were also affected by phytase supplementation.

Dietary effects on bone quality and turnover, and Ca and P metabolism in chickens

The responses of skeletal health and blood calcium (Ca) and phosphorus (P) status to different dietary calcium and available P (avP) contents were examined in 2-week-old chickens. High avP content resulted in more inorganic P (P(i)) and less ionised Ca (Ca(2+)) in the blood. Birds on low Ca and high avP diets showed a higher incidence of tibial dyschondroplasia and hypocalcaemic rickets and were therefore assumed to be hypocalcaemic. However the molar Ca:P ratio in bone was closer to the expected 1.67:1 in diets high in avP. No significant dietary mineral content effect was found on bone mineral content, or breaking strength, within the range of diets used. Results suggest that variations in molar Ca:P ratios in bone have little effect on mechanical competence, and that diets for this strain should be higher in Ca, and could be lower in avP, than current recommendations.

The effects of supplemental microbial phytase on the performance and utilization of dietary calcium, phosphorus, copper, and zinc in broiler chickens fed corn-soybean diets

A 3-wk feeding trial with 180 sexed day-old broiler chickens was conducted to study the efficacy of microbial phytase (Natuphos 1000) on growth performance, relative retention of P, Ca, Cu, and Zn, and mineral contents of plasma and bone. Treatments involved a normal P level corn-soybean diet, a low-P diet, and a low-P plus phytase (600 phytase units/kg) diet. Phytase supplementation increased (P < or = 0.05) body weight in male and female chickens by 13.2 and 5.8%, respectively, at 21 d. The improvements yielded body weights comparable to those obtained on the normal P diet. Phytase supplementation overcame (P < or = 0.05) the depression of feed intake observed on the low-P diet. Treatments had no effect on feed:gain ratio. Phytase supplementation of the low-P diet increased (P < or = 0.05) the relative retention of total P, Ca, Cu, and Zn by 12.5, 12.2, 19.3, and 62.3 percentage units, respectively, in male chickens. Microbial phytase increased the plasma P by 15.7% and reduced (P < or = 0.05) the Ca concentration by 34.1%, but had no effect on plasma concentrations of Cu or Zn. Phytase supplementation increased the percentage ash in both head and shaft portions of dry, fat-free tibia bone to a level comparable to that of the normal-P diet. Phytase supplementation had no effect on the concentration of any of the minerals measured in whole tibia ash but did increase (P < or = 0.05) the DM percentage of P and Ca min tibia head of male chickens by 0.65 and 1.4 percentage units, respectively. These results show that microbial phytase supplementation of a low-P diet increased growth and relative retention of total P, Ca, Cu, and Zn and improved bone mineralization in broiler chickens.

Dietary calcium and phosphorus effects on broiler performance and the incidence of sudden death syndrome mortality

Three experiments were conducted with broiler chickens to determine the effect of dietary Ca and P on growth, feed conversion, bone ash, and the incidence of sudden death syndrome (SDS) mortality. Trial 1 tested three rations [100% NRC (1984) Ca and P; 140% NRC Ca and P; and 140% NRC Ca and P to 3 wk and 100% NRC from 4 to 7 wk] in Ross x Ross males to 7 wk of age. Dietary Ca and P had no effect on body weight, feed conversion, bone ash, or leg problems, but SDS mortality was significantly higher in the two groups fed 140% Ca and P for 3 or 7 wk (2.83 and 3.33% SDS mortality, respectively). Trial 2 tested three diets (85% NRC Ca and P, 100% NRC Ca and P, and 140% NRC Ca and P) in mixed sex Arbor Acres x Peterson chicks to 7 wk of age. The lower level of Ca and P (85% NRC) significantly improved feed conversion (7 wk) and decreased bone ash only at 3 wk and serum Ca (7 wk). There was no effect of diet on SDS in this trial. Trial 3 tested two diets (85% NRC Ca and P or 100% NRC Ca and 85% NRC P) in Ross x Ross males to 9 wk of age. Six-week body weight was significantly reduced in the 85% NRC Ca and P diet but body weight was equal by 9 wk of age. No effects were observed for feed conversion, leg disorders, bone ash, or serum Ca. The SDS mortality was significantly increased in the chicks fed the 100% NRC Ca and 85% P diet compared to the 85% NRC Ca treatment. The results of these trials indicate that even slight deviations in dietary Ca and P beyond the NRC recommendations can create a metabolic imbalance in certain strains of broilers (Ross x Ross), which possibly increases susceptibility to SDS mortality.

Hypercalciuric response to dietary supplementation with DL-methionine and ammonium sulfate

Renal Ca and inorganic P (Pi) excretion were evaluated in Single Comb White Leghorn pullets reared on diets containing 1 or 3.5% Ca alone or supplemented with .6% DL-methionine or .53% ammonium sulfate. Plasma and urine samples were collected during a CONTROL period, and while 200 mM Ca was infused intravenously (Ca-LOADING). Excess Ca, whether supplied chronically in the feed or infused acutely into birds fed 1% Ca diets, significantly reduced glomerular filtration rates, effective renal plasma flow rates, and Pi excretion rates and significantly increased Ca excretion rates and urine pH. Birds fed diets supplemented with DL-methionine and ammonium sulfate maintained significantly lower plasma Ca concentrations during the CONTROL and Ca-LOADING periods than birds fed the respective 1 or 3.5% Ca basal diets. When compared with birds fed the respective 1 or 3.5% Ca basal diets, birds fed the 1% Ca diet supplemented with ammonium sulfate or the 3.5% Ca diet supplemented with DL-methionine had significantly higher absolute urinary Ca excretion rates during Ca-LOADING. Fractional Ca excretion during Ca-LOADING was significantly higher in birds fed 3.5% Ca supplemented with DL-methionine or ammonium sulfate than in birds fed the 3.5% Ca basal diet. These results indicate that DL-methionine and ammonium sulfate accelerated urinary Ca excretion and reduced Ca retention in the extracellular fluid. The hypercalciuric efficacies of DL-methionine and ammonium sulfate were revealed only when the filtered load of Ca was increased through intravenous Ca infusions.