Endogenous Losses Of Ca Research Articles

Microbial phytase reduces basal endogenous loss of calcium in pigs fed diets containing phytate phosphorus at commercial levels.

The objective of this experiment was to test the hypothesis that increasing dietary phytase reduces basal endogenous loss of Ca and increases P balance in pigs. Seventy barrows (initial body weight: 17.66 ± 1.69 kg) were allotted to seven Ca-free diets using a randomized complete block design with two blocks and five pigs per diet in each block. All diets were based on corn, potato protein concentrate, and full-fat rice bran. A positive control (PC) diet was formulated to contain P at the requirement for standardized total tract digestible (STTD) P by 11 to 25 kg pigs. Six negative control (NC) diets were formulated by reducing the provision of digestible P by 0.15% and adding 0, 250, 500, 1,000, 2,000, or 4,000 phytase units/kg diet. Pigs were housed individually in metabolism crates that allowed for total, but separate, collection of urine and feces. Daily feed allowance was 3.0 times the maintenance requirement for metabolizable energy and was divided into two equal meals. Diets were fed for 12 d with the first 5 d considered the adaptation period. Urine collections started on day 6 in the morning and ceased on day 10 in the morning. Fecal markers were also included in the morning meals on day 6 and day 10 and feces were collected according to the marker-to-marker procedure. Results indicated that the apparent total tract digestibility of dry matter was not affected by dietary P or phytase levels. The basal endogenous loss of Ca was not affected by dietary P, but exponentially decreased (P = 0.030) as phytase level increased in the diets. Phosphorus retention (g/d) and standardized total tract digestibility of phosphorus were greater (P < 0.05) in pigs fed the PC diet compared with pigs fed the NC diet with no phytase. The STTD of P exponentially (P < 0.001) increased as phytase level increased in the diets, but because of the lack of Ca, retention of P (% of absorbed) linearly decreased (P = 0.006) as phytase increased. In conclusion, basal endogenous loss of Ca decreased as dietary phytase increased demonstrating that endogenous Ca can be bound to phytate in the intestinal tract of pigs. However, STTD of P increased as phytase level in the diets increased.

PSVI-8 Effects of Phosphorus Level and Increasing Phytase Dose on Basal Endogenous Loss of Calcium and Balance of Phosphorus in Pigs Fed Diets Containing Phytate P at Commercial Levels

Abstract The objective was to test the hypothesis that dietary P concentration and level of phytase influences basal endogenous loss of Ca in pigs. Seventy barrows (body weight: 17.66 kg) were housed in metabolism crates and allotted to 7 Ca-free diets containing corn, potato protein concentrate, and full-fat rice bran (0.27% phytate P). A positive control (PC) diet contained P at the requirement for digestible P for 11 to 25 kg pigs. Negative control (NC) diets were formulated by reducing concentration of digestible P by 0.15% and adding a novel consensus bacterial 6-phytase variant at 0, 250, 500, 1,000, 2,000, or 4,000 phytase units/kg diet. Feces and urine samples were collected separately for 4 d after 5 d of adaptation. Dried and ground fecal samples were analyzed for dry matter, Ca, and P and urine was analyzed for P. Data were analyzed using a model that included diet as fixed effect. Positive control and NC were compared using a contrast statement and linear and exponential effects of dietary phytase were tested. Results indicated that apparent total tract digestibility of dry matter was not affected by dietary P or phytase (Table 1). The basal endogenous loss of Ca was not affected by dietary P, but exponentially (P = 0.030) decreased as dietary phytase increased. Phosphorus retention (g/d) was greater (P &amp;lt; 0.001) in pigs fed PC compared with NC without phytase. The standardized total tract digestibility (STTD) of P exponentially (P &amp;lt; 0.001) increased as phytase increased; however, retention of P as % of absorbed P decreased (linear, P = 0.006) as phytase increased because the extra P absorbed as a result of phytase could not be retained due to the lack of Ca. In conclusion, increasing the phytase dose decreased basal endogenous loss of Ca and increased STTD of P.

Comparative digestibility and retention of calcium and phosphorus in normal- and high-phytate diets fed to gestating sows and growing pigs

The objective of this research was to test the hypothesis that calculated values for standardized total tract digestibility (STTD) and retention of Ca and P are not different between gestating sows and growing pigs. A total of 32 gestating sows (day of gestation = 40) and 32 castrates (body weight = 19.8 kg) were placed in metabolism crates. Two diets were formulated to contain 9.8 or 29.4 g/kg phytate. Diets were formulated based on corn, soybean meal, Ca carbonate, and dicalcium phosphate and the high-phytate diet also contained 400 g/kg full-fat rice bran. A Ca-free diet and a P-free diet were used to determine basal endogenous losses of Ca and P. Feces and urine were collected for 4 days after 4 days of adaptation. Results indicated that basal endogenous losses of Ca and P from gestating sows were greater (P < 0.05) than from growing pigs. The digestibility of dry matter was not affected by the physiological state of the animals, but was greater (P < 0.001) in the normal-phytate diet than in the high-phytate diet. Phytate level did not affect the STTD of Ca or Ca retention by gestating sows, but the STTD of Ca and Ca retention were greater if growing pigs were fed the normal-phytate diet than if they were fed the high-phytate diet (physiological state × phytate level interaction; P < 0.001). The STTD of P was greater for the normal-phytate diet than for the high-phytate diet, but the difference was greater for growing pigs than for gestating sows (physiological state × phytate level interaction; P = 0.002). Phosphorus retention by growing pigs fed the normal-phytate diet was greater than if they were fed the high-phytate diet, but P retention by gestating sows was not affected by phytate level (physiological state × phytate level interaction; P < 0.001). Regardless of phytate level, gestating sows had reduced (P < 0.001) STTD of Ca and P and reduced retention of Ca and P compared with growing pigs. In conclusion, gestating sows have reduced digestibility and retention of Ca and P, but increased basal endogenous losses of Ca and P, compared with growing pigs. Response to dietary phytate is different for STTD and retention of Ca and P between gestating sows and growing pigs. It may, therefore, not always be accurate to formulate diets for gestating sows using digestibility values for Ca and P that were obtained in growing pigs.

True ileal calcium digestibility in soybean meal and canola meal, and true ileal phosphorous digestibility in maize-soybean meal and maize-canola meal diets, without and with microbial phytase, for broiler growers and finishers

ABSTRACT 1. Published data on the ileal Ca digestibility in soybean meal (SBM) and canola meal (CM), and the effect of microbial phytase on the Ca digestibility of these ingredients are limited. Therefore, two experiments were conducted, with the primary objective of determining the true ileal digestibility of calcium (Ca) in SBM and CM, without and with microbial phytase, during broiler grower (Experiment 1) and finisher (Experiment 2) periods. A secondary objective was to investigate the influence of microbial phytase on the true ileal digestibility of phosphorus (P), apparent digestibility of nitrogen (N) and minerals, and phytate disappearance in maize-SBM and maize-CM diets. Six experimental diets based on SBM and CM, with three phytase doses (0, 500 and 2000 FTU/kg), were fed to broilers from day 18 to 21 (Experiment 1) or 39 to 42 (Experiment 2) post-hatch. A Ca- and P-free diet, with no added phytase, was also developed to determine the endogenous Ca and P losses. Titanium dioxide was incorporated in all diets as an indigestible indicator. Each experimental diet was randomly allocated to six replicate cages (eight birds per cage). Apparent ileal digestibility was calculated using the indicator method and the true ileal digestibility was calculated by correcting for endogenous losses. Apparent total tract retention (ATTR) of Ca and P was also measured. 2. Ileal endogenous losses of Ca and P were determined to be 236 and 310 mg/kg of dry matter intake (DMI), respectively, in broiler growers and 29 and 130 mg/kg of DMI, respectively, in broiler finishers. True ileal Ca digestibility coefficients of SBM and CM, without added phytase, were determined to be 0.51 and 0.53, respectively, in broiler growers and 0.33 and 0.22, respectively, in broiler finishers. Increasing phytase doses increased (P < 0.05) the true ileal Ca digestibility of CM in both broiler growers and finishers, but Ca digestibility of SBM increased (P < 0.05) only at the superdose (2000 FTU/kg) in broiler finishers. The ATTR of Ca (P < 0.001) in growers was higher in CM than in SBM and was increased in both ingredients by increasing phytase doses. In finishers, the ATTR of Ca was increased (P < 0.001) by both phytase doses in CM, but only by the superdose in SBM, resulting in an ingredient × phytase interaction (P < 0.001). 3. True ileal P digestibility coefficients of maize-SBM and maize-CM diets, without added phytase, were determined to be 0.89 and 0.66, respectively, in broiler growers and 0.82 and 0.57, respectively, in broiler finishers. Supplemental phytase increased (P < 0.05) the true ileal P digestibility of the maize-CM diet in both broiler growers and finishers. However, the P digestibility of the maize-SBM diet was increased (P < 0.05) in broiler finishers only at the superdose (2000 FTU/kg). The ATTR of P was higher (P < 0.001) in the maize-SBM diet during both periods. 4. The apparent ileal digestibility of N, Mg, K and Mn was higher (P < 0.001) in the maize-SBM diet for broiler growers and finishers. Phytase addition had no effect (P > 0.05) on the apparent digestibility of N and minerals in growers and finishers. 5. Increasing phytase doses increased IP6 disappearance in the maize-CM diet, but not in the maize-SBM diet, resulting in an ingredient × phytase interaction (P < 0.001) for growers and finishers. 6. In conclusion, true ileal Ca digestibility coefficients of SBM and CM for broilers were determined in this study. The findings confirmed the influence of broiler age of Ca digestibility. Superdosing of phytase increased the digestibility and ATTR of Ca in CM and SBM by two-fold compared to the normal phytase dose.

Amino acid and calcium digestibility in hatchery byproducts fed to nursery pigs

The objective of this study was to determine amino acid (AA) and calcium (Ca) digestibility of hatchery byproducts in nursery pigs. In experiment 1, the coefficients of standardized ileal digestibility (CSID) of AA in hatchery byproducts were measured using 10 barrows surgically fitted with T-cannulas at the distal ileum (initial body weight = 11.3 ± 1.3 kg). Four diets were prepared to contain 30 % of infertile eggs, unhatched eggs, culled chicks, and a mixture (20 % dried infertile eggs + 20 % dried unhatched eggs + 60 % dried culled chicks) as the sole source of nitrogen and a nitrogen-free diet was additionally prepared to measure basal endogenous losses of AA. In experiment 2, ten nursery barrows (initial body weight = 10.2 ± 0.7 kg) were used to measure the coefficient of standardized total tract digestibility (CSTTD) of Ca in hatchery byproducts. Four experimental diets contained 10, 10, 25, and 15 % of infertile eggs, unhatched eggs, culled chicks, and the mixture (20 % dried infertile eggs + 20 % dried unhatched eggs + 60 % dried culled chicks) as the sole source of Ca, respectively and a Ca-free diet was additionally prepared to measure basal endogenous losses of Ca. The index method and the marker-to-marker method were employed in experiment 1 and in experiment 2, respectively. A replicated 5 × 4 Latin square design was an experimental design in both experiments. Infertile eggs had greater (P < 0.05) CSID of indispensable AA except for lysine and methionine compared with culled chicks. The CSID of indispensable AA did not differ between infertile eggs and unhatched eggs. The CSID of some AA in infertile eggs was greater (P < 0.05) than that in the mixture. The CSID of indispensable AA except for tryptophan was not different between culled chicks and the mixture. Culled chicks had the greatest (P < 0.05) CSTTD of Ca among test ingredients followed by the mixture, infertile eggs, and unhatched eggs. In conclusion, ileal digestibility of most indispensable AA in infertile eggs was greater than that in culled chicks and culled chicks had the greatest Ca digestibility among hatchery byproducts.

Influence of methodology on the measurement of ileal endogenous calcium losses in broiler chickens

ABSTRACT An experiment was conducted to determine the ileal endogenous calcium (Ca) losses in four-week old male Ross 308 broiler chickens (mean body weight ± SD, 1.66 ± 0.12 kg) using three assay methodologies. Three experimental diets were used: a Ca and phosphorus (P)-free diet and two other diets by substituting (w/w) 200 g/kg dextrose (w/w) with maize gluten meal or dried egg albumen as Ca-free protein sources. Each of the three experimental diets was randomly allocated and fed for three days to six replicate cages (six birds/cage), and ileal digesta were collected to measure the ileal endogenous Ca losses. The feed intake of birds fed diets containing the two protein sources was higher (P < 0.05) than the Ca and P-free diet. Body weight loss was observed in birds on the Ca and P-free diet and maize gluten meal-based diets. Ileal endogenous Ca losses were influenced (P < 0.05) by the assay methodology. Ileal endogenous Ca losses were determined to be 125, 77 and 46 mg/kg dry matter intake in birds fed the Ca and P-free diet, maize gluten meal diet and dried egg albumen diet, respectively. Ileal endogenous P losses were determined in birds fed Ca and P-free and dried egg albumen based diets. There was no effect (P > 0.05) of methodology on ileal endogenous P losses.

PSIV-14 Calcium digestibility in hatchery byproducts fed to nursery pigs

Abstract The objective was to determine standardized total tract digestibility (STTD) of calcium (Ca) in hatchery byproducts fed to nursery pigs. Ten barrows with mean body weight of 10.2 ± 0.7 kg were individually housed in metabolism crates. Four corn-based diets were formulated to contain 10% of infertile eggs (40% CP, 11.6% Ca, and 4,630 kcal/kg GE as-is), 10% of unhatched eggs (40% CP, 12.7% Ca, and 4,296 kcal/kg GE as-is), 25% of culled chicks (66% CP, 1.8% Ca, and 5,897 kcal/kg GE as-is), and 15% of a mixture of 3 ingredients aforementioned (56% CP, 6.2% Ca, and 5,342 kcal/kg GE as-is), respectively. A calcium-free diet was also prepared to measure basal endogenous losses of Ca. Ten animals were assigned to a replicated 5 × 4 Latin square design with 5 diets, and 4 periods. Each period consisted of a 5-d adaptation period and 5-d collection period. The marker to marker method was employed for total feces collection. The STTD of Ca in culled chicks (75.6%) was greater than that in the mixture (64.5%; P &amp;lt; 0.05). The ATTD and STTD of Ca in unhatched eggs (38.3 and 43.4%, respectively) were less than those in infertile eggs (48.5 and 53.3%, respectively; P &amp;lt; 0.05). Basal endogenous losses of Ca were determined at 659 mg/kg of dry matter intake. In conclusion, culled chicks had the greatest standardized total tract digestibility of calcium among test ingredients and standardized total tract digestible calcium in infertile eggs, unhatched eggs, culled chicks, and the mixture were 6.2, 5.5, 1.4, and 4.0%, respectively.

Studies on the measurement of ileal calcium digestibility of calcium sources in broiler chickens

Results from 3 experiments relating to the measurement of ileal calcium (Ca) digestibility in 4 different Ca sources for broiler chickens are presented herein. The first experiment was conducted to determine the effect of basal diet composition on the true Ca digestibility of limestone, meat and bone meal (MBM), monocalcium phosphate (MCP), and dicalcium phosphate (DCP). Eight experimental diets were developed based on 2 basal diets (corn-based or corn starch-based) with each of the 4 Ca sources. Two Ca-free diets representing both basal diets were used to determine the endogenous Ca losses. Each diet was randomly allotted to 6 replicate cages (6 birds per cage) and fed from 21 to 24 D post-hatch. Calcium digestibility of corn-based diet was higher (P < 0.05) than the corn starch-based purified diet. The average true Ca digestibility coefficients of limestone, MBM, MCP, and DCP were determined to be 0.51, 0.41, 0.43, and 0.32, respectively. The second experiment was conducted to examine the effect of indicator type on the apparent Ca digestibility of limestone. Two experimental diets with either titanium dioxide or acid insoluble ash (Celite) were developed. Each diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from 21 to 24 D post-hatch. Total tract Ca retention was also measured using the indicator ratios. Indicator type had no influence (P > 0.05) on the digestibility measurements. Ca retention determined using acid insoluble ash was higher (P < 0.05) compared to that determined using titanium dioxide. The third experiment was conducted to determine the effect of dietary adaptation length on apparent Ca digestibility of limestone. The experimental diet was offered from day 21 to 6 replicates (6 birds per cage) each for 24, 72, 120, or 168h and the ileal digesta were collected. Calcium digestibility at 24h was higher (P < 0.05), and increasing the adaptation length from 72 to 120h had no effect (P > 0.05) on the digestibility.

PSIV-13 Basal endogenous loss, standardized total tract digestibility, and retention of Ca in sows change throughout gestation, but microbial phytase reduces basal endogenous loss of Ca by gestating sows

Abstract The objective was to test the hypothesis that standardized total tract digestibility (STTD) of Ca and Ca and P retention and the response to microbial phytase in diets fed to sows are constant throughout gestation. Thirty-six sows (parity = 3.3) were allotted to 4 diets on d 7 post-breeding. Two corn-based diets in which calcium carbonate was the sole source of Ca and 2 Ca-free diets were formulated without or with phytase (500 units per kg). Sows were housed individually in metabolism crates during early-gestation, mid-gestation, and late-gestation, and feces and urine were quantitatively collected. Data were analyzed by repeated measures using a model that included phytase, period of gestation, and the interaction between phytase and period as fixed effects, and block and replicate as random effects. Interactions between period and phytase were not observed. The basal endogenous loss (BEL) of Ca was greater (P &lt; 0.05) in early-gestation than in mid- and late-gestation, but phytase reduced (P = 0.002) BEL of Ca and tended (P = 0.099) to increase apparent total tract digestibility (ATTD) of P in the Ca-free diet. Phytase did not affect ATTD of DM, STTD of Ca, ATTD of P, or Ca and P retention in sows fed the diet containing calcium carbonate (Table 1). The ATTD of DM was not affected by period, but Ca retention and ATTD of Ca and P were least (P &lt; 0.05) in mid-gestation, followed by early- and late-gestation, and the STTD of Ca in mid-gestation was also reduced (P &lt; 0.05) compared with early- or late-gestation. Phosphorus retention was greater (P &lt; 0.05) in late-gestation than in the earlier periods. In conclusion, BEL of Ca, STTD of Ca, ATTD of P, and Ca and P retention in sows change throughout gestation regardless of use of phytase. http://www.conferenceharvester.com/

178 A systematic review and meta-analysis of Ca digestibility and utilisation in growing and finishing pigs

Abstract The development of dietary recommendations based on digestible Ca values is an essential step to optimize pig performance and feed conversion because the present guidelines, expressed on total dietary Ca, are inadequate, as they ignore endogenous losses and the digestion process. A systematic review and meta-analysis of digestibility trials were performed to quantify factors affecting Ca absorption and retention, and to estimate endogenous Ca losses. Forty studies, corresponding to 201 dietary treatments performed on 1,204 growing pigs, were selected. Data analysis was performed in R using weighted linear mixed effects regression. The results indicated that while Ca absorption and retention (g/kg of BW/day) increased with increasing Ca (P &lt; 0.001), with non-phytate-P (P &lt; 0.001) and with exogenous phytase intakes (P &lt; 0.001), these responses decreased with increasing phytate-P intake (P &lt; 0.05). Interactions were detected between exogenous phytase and Ca intake (P &lt; 0.001), indicating reduced efficacy of this enzyme, and between phytate-P intake and exogenous phytase (P &lt; 0.05), indicating reversing of the direct negative effect of phytate-P on Ca absorption and retention. Based on the recommended Ca and P intake for a 25 kg pig, an exogenous phytase supplementation of 1,000 FTU/day could potentially improve Ca digestibility by 20–25%. There were no effects of animal characteristics (e.g. ‘genotype’) on Ca absorption and retention. The large amount of variance explained in Ca absorption (90%) and retention (91%) supported our a priori choice of independent variables. Estimated endogenous Ca losses were 239 mg/kg of DM (95% CI 114, 364). When scaled by bodyweight, the endogenous Ca excretion on Ca-and-P-free diets was 20.5 mg/kg of BW/day (95% CI 5.46, 36.5). These outcomes should contribute to a reassessment of Ca requirements, which should lead to a more accurate formulation of pig diets.

Standardized total tract digestibility of calcium varies among sources of calcium carbonate, but not among sources of dicalcium phosphate, but microbial phytase increases calcium digestibility in calcium carbonate1.

Two experiments were conducted to test the hypothesis that standardized total tract digestibility (STTD) of Ca and the response to microbial phytase is constant among different sources of Ca carbonate and that the STTD of Ca is constant among different sources of dicalcium phosphate (DCP) when fed to growing pigs. In Exp. 1, 80 pigs (initial BW: 19.0 ± 1.9 kg) were randomly allotted to 10 diets and 2 blocks with 4 pigs per diet in each block. Four sources of Ca carbonate were used, and each source was included in a diet without microbial phytase and a diet with microbial phytase (500 units/kg diet). Two Ca-free diets without or with microbial phytase were also formulated. Feed allowance was 2.7 times the maintenance energy requirement for ME and daily feed allotments were divided into 2 equal meals. The initial 4 d of each period were considered the adaptation period to the diets followed by 4 d of fecal collection using the marker-to-marker procedure. Pigs fed diets containing exogenous phytase had lower (P < 0.05) basal endogenous loss of Ca compared with pigs fed diets containing no phytase. There were no interactions between phytase and source of Ca carbonate. Values for STTD of Ca were greater (P < 0.05) for diets containing microbial phytase (77.3% to 85.4%) compared with diets without exogenous phytase (70.6% to 75.2%), and values for STTD of Ca differed (P < 0.05) among the 4 sources of Ca carbonate. In Exp. 2, 40 pigs (initial BW: 14.9 ± 1.3 kg) were allotted to a completely randomized design with 5 diets and 8 replicate pigs per diet. A basal diet in which all Ca was supplied by Ca carbonate was formulated. Three diets were formulated by adding 3 sources of DCP to the basal diet and a Ca-free diet was also used. Feeding and collection methods were as described for Exp. 1. Results indicated that values for STTD of Ca and ATTD of P were not different among diets, indicating that under the conditions of this experiment, the digestibility of Ca and P in DCP appears to be constant regardless of origin of DCP. In conclusion, use of microbial phytase reduces the basal endogenous loss of Ca and increases Ca digestibility in Ca carbonate. The STTD of Ca varies among sources of Ca carbonate, regardless of phytase inclusion, but that appears not to be the case for the STTD of Ca in different sources of DCP.

Basal endogenous loss, standardized total tract digestibility of calcium in calcium carbonate, and retention of calcium in gestating sows change during gestation, but microbial phytase reduces basal endogenous loss of calcium1.

The objective was to test the hypothesis that the standardized total tract digestibility (STTD) of Ca and the response to microbial phytase on STTD of Ca and apparent total tract digestibility (ATTD) of P in diets fed to gestating sows are constant throughout gestation. The second objective was to test the hypothesis that retention of Ca and P does not change during gestation. Thirty-six gestating sows (parity = 3.3 ± 1.5; d of gestation = 7 d) were allotted to 4 diets. Two diets containing 0 or 500 units of microbial phytase per kilogram were based on corn, potato protein concentrate, and calcium carbonate. Two Ca-free diets were also formulated without or with microbial phytase to estimate basal endogenous loss of Ca. Daily feed allowance was 1.5 times the maintenance energy requirement. Sows were housed individually in gestation stalls and fed a common gestation diet, but they were moved to metabolism crates from days 7 to 20 (early gestation), days 49 to 62 (midgestation), and again from days 91 to 104 (late gestation). When sows were in metabolism crates, they were fed experimental diets and feces and urine were quantitatively collected for 4 d after 4 d of adaptation. Results indicated that outcomes were not influenced by the interaction between period of gestation and dietary phytase. The basal endogenous loss of Ca was greater (P < 0.05) by sows in early gestation than by sows in mid- or late-gestation, but supplementation of microbial phytase to the Ca-free diet decreased (P < 0.01) the basal endogenous loss of Ca and tended (P = 0.099) to increase ATTD of P. Supplementation of microbial phytase did not affect ATTD of DM, STTD of Ca, Ca retention, ATTD of P, or P retention in sows fed the calcium carbonate-containing diet. The ATTD of DM was not affected by period of gestation, but the ATTD of Ca, the ATTD of P, and the retention of Ca were least (P < 0.05) in midgestation, followed by early and late gestation, respectively, and the STTD of Ca in midgestation was also reduced (P < 0.05) compared with sows in early or late gestation. Phosphorus retention was greater (P < 0.05) in late gestation than in the earlier periods. In conclusion, Ca retention was less negative and ATTD of P tended to increase with supplementation of microbial phytase to the Ca-free diet regardless of gestation period. The basal endogenous loss, STTD of Ca, ATTD of P, and retention of Ca and P in gestating sows change during gestation with the greatest digestibility values observed in late gestation.

Do not neglect calcium: a systematic review and meta-analysis (meta-regression) of its digestibility and utilisation in growing and finishing pigs.

Ca digestibility and utilisation in growing pigs are not well understood, and are usually neglected in diet formulation. This has implications not only for the accurate determination of its requirements but also for its interactions with other nutrients. A systematic review and meta-analysis (meta-regression) of published trials was carried out to quantify factors affecting Ca absorption and utilisation, and to derive an estimate of Ca endogenous excretion. The analysis was carried out on the data from forty studies, corresponding to 201 treatments performed on 1204 pigs. The results indicated that although Ca absorption and retention (g/kg of body weight per d) increased with increasing Ca intake (P<0·001), non-phytate-P intake (P<0·001) and exogenous phytase supplementation (P<0·001), these values decreased with increasing phytate-P intake (P<0·05). Interactions between exogenous phytase and Ca intake, indicating reduced efficacy of this enzyme (P<0·001), and between phytate-P intake and exogenous phytase, counteracting the direct negative effect of phytate-P (P<0·05) on Ca absorption and retention, were also detected. There were no effects of animal-related characteristics, such as pig genotype in Ca absorption and retention. The large amount of variance explained in Ca absorption (90 %) and retention (91 %) supported our choice of independent variables. Endogenous Ca losses obtained via linear regression were 239 mg/kg of DM intake (95 % CI 114, 364). These outcomes advance the current understanding of Ca digestibility and utilisation, and should contribute towards establishing requirements for digestible Ca. Consequently, pig diets will be more correctly formulated if digestible Ca values are used in estimating requirements for Ca.

Measurement of the true ileal calcium digestibility of some feed ingredients for broiler chickens

Results from three experiments relating to the measurement of ileal calcium (Ca) digestibility in feed ingredients for broiler chickens are presented herein. The first experiment was conducted to determine the true ileal Ca digestibility of dicalcium phosphate (DCP), monocalcium phosphate (MCP), poultry by-product meal (PBPM), fish meal (FM) and canola meal (CM). Five semi-purified diets containing DCP, MCP, PBPM and FM with a dietary Ca concentration of 9 g/kg, and CM with a dietary Ca concentration of 5.71 g/kg were generated. A Ca- and phosphorus (P)-free diet was used to determine the basal ileal endogenous Ca losses. Titanium dioxide was incorporated in all diets as an indigestible marker. Each diet was randomly allotted to six replicate cages (eight birds per cage) and fed from 21 to 24 days post-hatch. True Ca digestibility coefficients of DCP, MCP, PBPM, FM and CM were determined to be 0.28, 0.33, 0.29, 0.24 and 0.31, respectively. These lower digestibility coefficients were unexpected and it was speculated that this finding may be due to the length of adaptation to assay diets and/or assay methodology. To investigate these possibilities, two more experiments were conducted. In the second experiment, the influence of dietary adaptation length was examined with DCP and MCP. The assay diets with DCP and MCP, and the Ca- and P-free diet were similar to those used in Experiment 1. Each diet was randomly allocated to four replicate cages (15 birds per cage) and fed from 21 to 24 days post-hatch. Digesta samples of five birds from each replicate were collected after 24, 48 and 72 h of feeding. Dietary adaptation length had no influence (P > 0.05) on the true Ca digestibility of MCP, but increased that of DCP at 24 h. True ileal Ca digestibility of DCP and MCP after 24, 48 and 72 h of adaptation were 0.45, 0.36, and 0.35, and 0.30, 0.32 and 0.34, respectively. The third experiment was conducted to determine the effect of assay methodology (direct, regression and difference methods) and Ca:non-phytate P ratio (2:1 and 1.16:1) on the Ca digestibility of DCP. The true Ca digestibility coefficients of DCP determined by the direct, difference and regression methods with Ca:non-phytate P ratio of 1.16:1 were 0.34, 0.21 and 0.13, respectively. The true Ca digestibility of DCP determined by the direct method was higher (P < 0.05) than those determined by difference and regression methods The true Ca digestibility coefficient of DCP with Ca:non-phytate P ratios of 2:1 and 1.16:1 were 0.25 and 0.21, respectively, and was not influenced (P > 0.05) by the Ca to non-phytate P ratio.

Effects of zinc oxide and microbial phytase on digestibility of calcium and phosphorus in maize-based diets fed to growing pigs.

An experiment was conducted to test the hypothesis that inclusion of Zn at a pharmacological level in diets fed to pigs affects apparent total tract digestibility (ATTD) of Ca and P and standardized total tract digestibility (STTD) of Ca. The second hypothesis was that inclusion of microbial phytase increases the ATTD of Ca and P and the STTD of Ca regardless of the concentration of Zn in the diet. Fifty-six growing barrows (15.4 ± 1.9 kg average BW) were allotted to a randomized complete block design with 7 dietary treatments and 8 pigs per treatment. A maize-based basal diet was formulated with either 0 or 2,400 mg/kg Zn from ZnO and 0, 1,000, or 3,000 units of phytase (FTU) per kilogram. A Ca-free diet was used to determine basal endogenous losses of Ca. Experimental diets were fed for 13 d, and feces were collected from the feed provided from d 6 to 11 using the marker-to-marker approach; urine was also collected from d 6 to 11. Retention of Ca, ATTD of Ca, and STTD of Ca increased ( < 0.01) as the concentration of phytase in the diet increased and were less ( < 0.01) if ZnO was used than if no ZnO was added to the diet. Retention of P and the ATTD of P increased ( < 0.0001) as the concentration of phytase increased in the diet, but the increase was greater if ZnO was not added than if ZnO was added to the diet (interaction, < 0.05). In conclusion, pharmacological levels of Zn reduced Ca and P digestibility and retention, but this effect was partly ameliorated by the inclusion of phytase in the diets. Inclusion of microbial phytase increased the ATTD and STTD of Ca in diets and also the ATTD of P.

Effect of calcium source and particle size on the true ileal digestibility and total tract retention of calcium in broiler chickens

The influence of calcium (Ca) source and particle size on true ileal digestibility coefficient (TIDC) of Ca and apparent total tract retention coefficient (ATTRC) of Ca in broilers was assessed. Four experimental diets containing limestone and oyster shell, each as fine (<0.5mm) and coarse (1–2mm) particles, were fed to broiler chickens from 21 to 24days of age. A Ca- and phosphorus-free diet was used to determine the ileal endogenous Ca losses. Limestone and oyster shell were obtained from commercial sources and ground to pass through a set of sieves to obtain the fine and coarse particles. Titanium dioxide was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage). Apparent ileal digestibility coefficient and ATTRC of Ca were calculated using the indicator method and the TIDC values were calculated by correcting for endogenous Ca losses. Ileal endogenous Ca losses were determined to be 115mg/kg of dry matter intake. The main effect of Ca source and the interaction between Ca source and particle size were not significant (P>0.05) for the TIDC and ATTRC of Ca. Both TIDC and ATTRC of Ca were influenced (P<0.05) by particle size, with coarser particles increasing the digestibility and retention values. Increased particle size increased the TIDC of Ca in limestone from 0.38 to 0.62 and that of oyster shell from 0.33 to 0.56. The corresponding increases in ATTRC of Ca were from 0.44 to 0.66 in limestone and from 0.40 to 0.60 in oyster shell. Calcium concentration in the gizzard contents of birds was higher (P<0.05) for limestone as compared to oyster shell and increased with increase in particle size. Calcium concentration in the gizzard contents was strongly correlated with the TIDC (r=0.81; P<0.01) and ATTRC (r=0.82; P<0.01) of Ca. A strong correlation (r=0.80, P<0.01) was also observed between TIDC and ATTRC of Ca.

Effect of limestone particle size and calcium to non-phytate phosphorus ratio on true ileal calcium digestibility of limestone for broiler chickens

The purpose of this study was to determine the effect of limestone particle size and calcium (Ca) to non-phytate phosphorus (P) ratio on the true ileal Ca digestibility of limestone for broiler chickens. A limestone sample was passed through a set of sieves and separated into fine (<0.5 mm) and coarse (1–2 mm) particles. The analysed Ca concentration of both particle sizes was similar (420 g/kg).Six experimental diets were developed using each particle size with Ca:non-phytate P ratios of 1.5:1, 2.0:1 and 2.5:1, with ratios being adjusted by manipulating the dietary Ca concentrations. A Ca-free diet was also developed to determine the basal ileal endogenous Ca losses. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker.Each experimental diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from d 21 to 24 post hatch. Apparent ileal digestibility of Ca was calculated using the indicator method and corrected for basal endogenous losses to determine the true Ca digestibility.The basal ileal endogenous Ca losses were determined to be 127 mg/kg of dry matter intake.Increasing Ca:non-phytate P ratios reduced the true Ca digestibility of limestone. The true Ca digestibility coefficients of limestone with Ca:non-phytate P ratios of 1.5, 2.0 and 2.5 were 0.65, 0.57 and 0.49, respectively.Particle size of limestone had a marked effect on the Ca digestibility, with the digestibility being higher in coarse particles (0.71 vs. 0.43).

Particle size of calcium carbonate does not affect apparent and standardized total tract digestibility of calcium, retention of calcium, or growth performance of growing pigs.

Two experiments were conducted to evaluate particle size of calcium carbonate used in diets fed to growing pigs. Experiment 1 was conducted to determine apparent total tract digestibility (ATTD), standardized total tract digestibility (STTD), and retention of Ca among diets containing calcium carbonate produced to different particle sizes, and Exp. 2 was conducted to determine if growth performance of weanling pigs is affected by particle size of calcium carbonate. In Exp. 1, 4 diets based on corn and potato protein isolate were formulated to contain 0.70% Ca and 0.33% standardized total tract digestible P, but the calcium carbonate used in the diets was ground to 4 different particle sizes (200, 500, 700, or 1,125 μm). A Ca-free diet was formulated to determine basal endogenous losses of Ca. In Exp. 2, 4 diets were based on corn and soybean meal and the only difference among diets was that each diet contained calcium carbonate ground to the 4 particle sizes used in Exp. 1. In Exp. 1, 40 barrows (15.42 ± 0.70 kg initial BW) were allotted to the 5 diets with 8 replicate pigs per diet using a randomized complete block design, and in Exp. 2, 128 pigs with an initial BW of 9.61 ± 0.09 kg were randomly allotted to 4 experimental diets. Results of Exp. 1 indicated that basal endogenous losses of Ca were 0.329 g/kg DMI. The ATTD of Ca was 70.0 ± 3.2, 74.3 ± 2.7, 70.0 ± 2.9, and 72.1 ± 2.7 and the STTD of Ca was 74.2 ± 3.2, 78.5 ± 2.7, 74.1 ± 2.9, and 76.2 ± 2.7 for calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. Retention of Ca was 67.4 ± 3.1, 70.4 ± 2.6, 63.9 ± 2.8, and 67.2 ± 2.2 for diets containing calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. There were no differences among diets for ATTD of Ca, STTD of Ca, or retention of Ca. The ATTD of P was 64.5 ± 1.7, 66.8 ± 2.6, 64.2 ± 3.0, and 63.2 ± 1.7% and retention of P was 61.4 ± 1.4, 63.8 ± 2.8, 61.9 ± 2.8, and 60.9 ± 1.5 for diets containing calcium carbonate ground to 200, 500, 700, or 1,125 μm, respectively. Neither ATTD of P nor retention of P was influenced by the particle size of calcium carbonate. Results of Exp. 2 indicated that ADG, ADFI, and G:F were not impacted by the particle size of calcium carbonate. In conclusion, particle size of calcium carbonate did not affect ATTD of Ca, STTD of Ca, or retention of Ca; ATTD of P or retention of P; or growth performance of pigs. Any particle size of calcium carbonate in the range from 200 to 1,125 μm can therefore be used in diets fed to pigs.

Digestibility of calcium in feed ingredients and requirements of digestible calcium for growing pigs

Efforts to reduce phosphorus (P) excretion from pigs have increased during the past few decades and it has been recognised that interactions among dietary P, calcium (Ca), phytate, and microbial phytase exist. However, limited research has been reported on Ca digestibility, but to optimise the use of both Ca and P, digestibility values of Ca are needed. Due to endogenous losses of Ca, values for standardised total tract digestibility (STTD) of Ca in different Ca supplements and feed ingredients have been determined, and these values may be used to formulate mixed diets. Phytate may bind intrinsic Ca in feed ingredients of plant origin as well as extrinsic Ca from ingredients of animal origin or Ca supplements, but not all forms of Ca in Ca supplements will bind to phytate. Therefore, the effect of phytase on the STTD of Ca may vary depending on the amount of Ca bound to phytate and in some cases microbial phytase will result in increased STTD of Ca from animal proteins or Ca supplements. Dietary fibre may increase the STTD of Ca, but particle size and soybean oil do not influence the STTD of Ca. Requirements for digestible Ca by growing pigs has not yet been determined, but with the availability of values for the STTD of Ca in most commonly used feed ingredients, the basis for determining such values has been prepared. In conclusion, data for the STTD of Ca and the effects of microbial phytase in many feed ingredients have been determined and future research will be directed at determining the requirements for digestible Ca by different groups of pigs.

Measurement of true ileal calcium digestibility in meat and bone meal for broiler chickens using the direct method

The objective of the study that is presented herein was to determine the true ileal calcium (Ca) digestibility in meat and bone meal (MBM) for broiler chickens using the direct method. Four MBM samples (coded as MBM-1, MBM-2, MBM-3 and MBM-4) were obtained and analyzed for nutrient composition, particle size distribution and bone to soft tissue ratio. The Ca concentrations of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 71, 118, 114 and 81 g/kg, respectively. The corresponding geometric mean particle diameters and bone to soft tissue ratios were 0.866, 0.622, 0.875 and 0.781 mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar Ca concentration (8.3 g/kg) from each MBM and a Ca and phosphorus-free diet, were developed. Meat and bone meal served as the sole source of Ca in the MBM diets. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage) and offered from d 28 to 31 post-hatch. Apparent ileal Ca digestibility was calculated by the indicator method and corrected for ileal endogenous Ca losses to determine the true ileal Ca digestibility. Ileal endogenous Ca losses were determined to be 88 mg/kg dry matter intake. True ileal Ca digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.560, 0.446, 0.517 and 0.413, respectively. True Ca digestibility of MBM-1 was higher (P < 0.05) than MBM-2 and MBM-4 but similar (P > 0.05) to that of MBM-3. True Ca digestibility of MBM-2 was similar (P > 0.05) to MBM-3 and MBM-4, while that of MBM-3 was higher (P < 0.05) than MBM-4. These results demonstrated that the direct method can be used for the determination of true Ca digestibility in feed ingredients and that Ca in MBM is not highly available as often assumed. The variability in true Ca digestibility of MBM samples could not be attributed to Ca content, percentage bones or particle size.