title: The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials 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. Random-effects models for longitudinal data. Standardized total tract digestibility of phosphorus in copra meal, palm kernel expellers, palm kernel meal, and soybean meal fed to growing pigs. Identification of randomized controlled trials in systematic reviews: accuracy and reliability of screening records. Estimation of true phosphorus digestibility and endogenous phosphorus loss in growing pigs fed conventional and low-phytate soybean meals. Effects of microbial phytase on apparent and standardized total tract digestibility of calcium in calcium supplements fed to growing pigs. Concentration of dietary calcium supplied by calcium carbonate does not affect the apparent total tract digestibility of calcium, but decreases digestibility of phosphorus by growing pigs. Requirement for digestible calcium by 25 to 50 kg pigs at different dietary concentrations of phosphorus as indicated by growth performance, bone ash concentration, and calcium and phosphorus balances. SYRCLE’s risk of bias tool for animal studies
abstract: Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more 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 ) , st and ardized 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 % st and ardized 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 r and omized complete block design , and in Exp . 2 , 128 pigs with an initial BW of 9.61 ± 0.09 kg were r and omly 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 Models for the analysis of longitudinal data must recognize the relationship between serial observations on the same unit . Multivariate models with general covariance structure are often difficult to apply to highly unbalanced data , whereas two-stage r and om-effects models can be used easily . In two-stage models , the probability distributions for the response vectors of different individuals belong to a single family , but some r and om-effects parameters vary across individuals , with a distribution specified at the second stage . A general family of models is discussed , which includes both growth models and repeated- measures models as special cases . A unified approach to fitting these models , based on a combination of empirical Bayes and maximum likelihood estimation of model parameters and using the EM algorithm , is discussed . Two examples are taken from a current epidemiological study of the health effects of air pollution Sixty-six barrows ( initial BW : 27.4 ± 2.8 kg ) were used to determine the st and ardized total tract digestibility ( STTD ) of P in copra meal ( CM ) , palm kernel expellers from Indonesia ( PKE-IN ) , palm kernel expellers from Costa Rica ( PKE-CR ) , palm kernel meal from Costa Rica ( PKM ) , and soybean meal ( SBM ) without or with exogenous phytase . Pigs were housed individually in metabolism cages and allotted to 11 diets with 6 replicate pigs per diet in a generalized r and omized block design . Five diets were formulated by mixing cornstarch and sugar with CM , PKE-IN , PKE-CR , PKM , or SBM . Five additional diets , which were identical to the initial 5 diets but supplemented with 800 units of phytase , were also formulated . A P-free diet was used to measure basal endogenous losses of P by the pigs . Feces were collected for 5 d using the marker to marker approach after a 5-d adaptation period . Analyzed total P in CM , PKE-IN , PKE-CR , PKM , and SBM was 0.52 , 0.51 , 0.53 , 0.54 , and 0.67 % , respectively . Phytate P was 0.22 , 0.35 , 0.38 , 0.32 , and 0.44 % in CM , PKE-IN , PKE-CR , PKM , and SBM , respectively . Addition of phytase increased ( P < 0.05 ) the apparent total tract digestibility ( ATTD ) of P from 60.6 to 80.8 , 27.3 to 56.5 , 32.6 to 59.9 , 48.9 to 64.1 , and 41.1 to 72.2 % in CM , PKE-IN , PKE-CR , PKM , and SBM , respectively . The ATTD of P in CM was greater ( P < 0.05 ) than in any of the other ingredients . The ATTD of P in SBM and PKM was greater ( P < 0.05 ) than in PKE-IN , with PKE-CR being intermediate . The STTD of P increased ( P < 0.05 ) from 70.6 to 90.3 , 37.6 to 66.4 , 43.2 to 69.9 , 57.9 to 73.5 , and 49.6 to 81.1 % in CM , PKE-IN , PKE-CR , PKM , and SBM , respectively , when microbial phytase was added to the diets . When expressed as a percentage of total P , phytate P concentration in the ingredient negatively affected ( P < 0.05 ) the ATTD of P ( 107.09 - 1.0564 × % phytate P ; R(2 ) = 87.1 ) and the STTD of P ( 116.3 - 1.0487 × % phytate P ; R(2 ) = 89.4 ) . In conclusion , microbial phytase increased P digestibility of CM , PKM , PKE-CR , PKE-IN , and SBM when fed to growing pigs , and the concentration of phytate P affects the response to microbial phytase A study was conducted to estimate the accuracy and reliability of  review ers when screening records for relevant trials for a systematic review . A sensitive search of ten electronic bibliographic data bases yielded 22 571 records of potentially relevant trials . Records were allocated to four review ers such that two review ers examined each record and so that identification of trials by each review er could be compared with those identified by each of the other review ers . Agreement between review ers was assessed using Cohen 's kappa statistic . Ascertainment intersection methods were used to estimate the likely number of trials missed by review ers . Full copies of reports were obtained and assessed independently by two research ers for eligibility for the review . Eligible reports formed the ' gold st and ard ' against which an assessment was made about the accuracy of screening by review ers . After screening , 301 of 22 571 records were identified by at least one review er as potentially relevant . Agreement was ' almost perfect ' ( kappa>0.8 ) within two pairs , ' substantial ' ( kappa>0.6 ) within three pairs and ' moderate ' ( kappa>0.4 ) within one pair . Of the 301 records selected , 273 complete reports were available . When pairs of review ers agreed on the potential relevance of records , 81 per cent were eligible ( range 69 to 91 per cent ) . If review ers disagreed , 22 per cent were eligible ( range 12 to 45 per cent ) . Single review ers missed on average 8 per cent of eligible reports ( range 0 to 24 per cent ) , whereas pairs of review ers did not miss any ( range 0 to 1 per cent ) . The use of two review ers to screen records increased the number of r and omized trials identified by an average of 9 per cent ( range 0 to 32 per cent ) . Review ers can reliably identify potentially relevant records when screening thous and s of records for eligibility . Two review ers should screen records for eligibility , whenever possible , in order to maximize ascertainment of relevant trials This study reevaluated the method of regressing of total P output against dietary P intake to simultaneously estimate true P digestibility and endogenous P loss in growing pigs fed either conventional or low-phytate soybean meal ( SBM ) . Four isocaloric diets were formulated to contain increasing concentrations of each type of SBM ( 8 diets total ) , and therefore contained increasing concentrations of dietary P. Dietary P and Ca concentrations were deficient because they were supplied solely by SBM , and Ca : total P ratios were less than 1:1 . Sixteen barrows ( initial BW 17.7 + /- 1.8 kg ) were surgically fitted with a simple T-cannula at the distal ileum , r and omly assigned to metabolism crates , and fed the experimental diets in a replicated 8 x 8 Latin square design . Feed was provided at 90 g/kg of BW(0.75 ) and fed in 2 equally sized meals at 0800 and 2000 , with diets containing Cr sesquioxide ( 3 g/kg ) as an indigestible marker . As the P concentration increased from 0.9 to 3.9 g/kg of DM , the apparent prececal P digestibility increased for conventional SBM ( P < 0.05 ) , but no relationship was observed for low-phytate SBM . The output of total P [ mg/(kg of BW(0.75).d ) ] , either prececal or total tract , exhibited a linear relationship ( P < 0.01 ) with increasing P intake . However , a quadratic response ( P = 0.02 ) was also detected for total tract P output from pigs fed low-phytate SBM . True P digestibility was not different between prececal and total tract collection sites ( P > 0.10 ) , but was greater ( P < 0.01 ) for low-phytate SBM ( 62.6 % ) compared with conventional SBM ( 44.5 % ) . Endogenous P estimates were not different between the SBM varieties and averaged 4.83 mg/(kg of BW(0.75).d ) . However , endogenous P estimates were highly variable between individual animals and , therefore , were not significantly different from zero . In this study , estimates of endogenous P loss from pigs were relatively low compared with previously reported values , and evidence of nonlinearity in P output was observed . These results suggest that the difference in true P digestibility between conventional SBM and low-phytate SBM is influenced by dietary phytate content when growing pigs are fed P-deficient diets An experiment was conducted to test the hypothesis that differences in the apparent total tract digestibility ( ATTD ) and st and ardized total tract digestibility ( STTD ) of Ca exist among Ca supplements and that inclusion of microbial phytase increases the ATTD and STTD of Ca . One hundred and four growing barrows ( average initial BW of 17.73 ± 2.53 kg ) were allotted to a r and omized complete block design with 13 dietary treatments and 8 pigs per treatment . A basal diet containing corn , cornstarch , potato protein isolate , soybean oil , calcium carbonate , monosodium phosphate , vitamins , and minerals was formulated . Five additional diets were formulated by adding monocalcium phosphate ( MCP ) , dicalcium phosphate ( DCP ) , calcium carbonate , Lithothamnium calcareum Ca , or a high-Ca sugar beet co-product to the basal diet at the expense of cornstarch . Six additional diets that were similar to the previous 6 diets with the exception that they also contained 500 units per kilogram of microbial phytase were also formulated . A Ca-free diet was used to determine basal endogenous losses of Ca . Feces were collected using the marker-to-marker approach . Results indicated that regardless of inclusion of microbial phytase , MCP had the greatest ( P < 0.05 ) ATTD and STTD of Ca . The ATTD and STTD of Ca in DCP were greater ( P < 0.05 ) than in calcium carbonate , L. calcareumC a , or in the sugar beet co-product , but no differences were observed among the ATTD and STTD of Ca in calcium carbonate , L. calcareum Ca , or sugar beet co-product . Inclusion of microbial phytase increased ( P < 0.05 ) the ATTD and STTD of Ca in the diets , but this was not the case in the Ca supplements . Regardless of inclusion of microbial phytase , the ATTD of P was greater ( P < 0.05 ) in pigs fed basal , MCP , or DCP diets than in pigs fed calcium carbonate , L. calcareum Ca , or the sugar beet co-product , but pigs fed calcium carbonate diets had greater ( P < 0.05 ) ATTD of P than pigs fed L. calcareumCa or the sugar beet co-product . Regardless of Ca source , inclusion of microbial phytase increased ( P < 0.001 ) the ATTD of P. In conclusion , MCP has the greatest ATTD and STTD of Ca  among the calcium supplements used in this experiment , followed by DCP . Basal , MCP , and DCP diets had greater ATTD of P than the other diets , and inclusion of microbial phytase increased the ATTD and STTD of Ca and the ATTD of P in the diets A regional experiment was conducted to test the hypothesis that the concentration of dietary Ca does not affect the digestibility of Ca or P in diets fed to growing pigs .  Six diets based on corn , potato protein isolate , cornstarch , and soybean oil were formulated . All diets also contained monosodium phosphate , crystalline AA , salt , and a vitamin-micromineral premix . The only difference among the diets was that varying concentrations of calcium carbonate were used to create diets containing 0.33 , 0.46 , 0.51 , 0.67 , 0.92 , and 1.04 % Ca . All diets contained between 0.40 and 0.43 % P. Six universities participated in the experiment and each university contributed 2 replicates to the experiment for a total of 12 replicates ( initial BW : 23.1 ± 4.4 kg ) . Pigs were placed in metabolism cages that allowed total , but separate , collection of feces and urine from the pigs . Pigs within each replicate were r and omly allotted to the 6 diets and fed experimental diets for 14 d with urine and feces being collected over a 5-d period . Diets , feces , and urine sample s were analyzed for Ca and P , and the daily balance , the apparent total tract digestibility ( ATTD ) , and the retention of Ca and P were calculated . Results indicated that intake , fecal excretion , and urinary excretion of Ca increased ( linear , P<0.05 ) as dietary Ca concentration increased . The daily intake of P was not affected by the dietary concentration of Ca , but fecal excretion of P increased ( linear , P<0.05 ) as dietary Ca concentrations increased . In contrast , urinary P output was decreased ( linear , P<0.05 ) as dietary Ca increased . The retention of Ca increased ( linear , P<0.05 ) from 1.73 to 4.60 g/d , whereas the retention of P decreased ( linear , P<0.05 ) from 1.98 to 1.77 g/d as dietary Ca concentrations increased . However , if calculated as a percentage of intake , both Ca and P retention were decreased ( linear , P<0.05 ) as dietary Ca concentration increased ( from 55.4 to 46.1 % and from 48.4 to 43.5 % , respectively ) . The ATTD of Ca was not affected by the dietary concentration of Ca , but the ATTD of P was decreased ( linear , P<0.05 ) from 56.9 to 46.2 % as dietary Ca concentration increased . It is concluded that the dietary concentration of Ca does not affect the ATTD of Ca in calcium carbonate , but increased concentrations of dietary Ca may decrease the ATTD of P in diets based on corn , potato protein isolate , and monosodium phosphate Two experiments were conducted to determine the requirement for st and ardized total tract digestible ( STTD ) Ca by 25 to 50 kg pigs at different concentrations of STTD P. Twenty corn-soybean meal based diets were formulated with diets containing 4 concentrations of STTD P ( 0.15 , 0.31 , 0.39 , or 0.47 % ) and 5 concentrations of STTD Ca ( 0.13 , 0.27 , 0.42 , 0.57 , or 0.72 % ) . Diets were mixed in 1 batch and were used in both experiments . In Exp . 1 , 240 pigs ( initial average BW : 24.70 ± 1.27 kg ) were r and omly allotted to the 20 diets in 6 blocks with 1 pen per diet in each block using a 4 × 5 factorial design . There was 1 gilt and 1 barrow in each pen . At the conclusion of the 28 d experiment , all barrows were euthanized and the right femur was collected . Results indicated that there were interactions ( < 0.001 ) between concentration of STTD Ca and concentration of STTD P in diets for ADG , G : F , and bone ash . The predicted maximum ADG at STTD P concentrations of 0.15 , 0.31 , 0.39 , and 0.47 % were 0.76 , 0.87 , 0.90 , and 0.92 kg at STTD Ca concentrations of 0.12 , 0.36 , 0.47 , and 0.59 % , respectively , which correspond to STTD Ca : STTD P ratios of 0.80:1 , 1.16:1 , 1.21:1 , and 1.26:1 . The predicted maximum G : F ratio at the 4 STTD P concentrations were 0.43 , 0.46 , 0.48 , and 0.50 kg/kg at STTD Ca concentrations of 0.09 , 0.38 , 0.52 , and 0.67 % , respectively , and these values correspond to STTD Ca : STTD P ratios of 0.60:1 , 1.23:1 , 1.33:1 , and 1.43:1 . The predicted maximum bone ash at the 4 STTD P concentrations were 14.5 , 21.0 , 23.1 , and 24.5 g at STTD Ca concentrations of 0.41 , 0.56 , 0.64 , and 0.72 % , respectively , which correspond to STTD Ca : STTD P ratios of 2.73:1 , 1.81:1 , 1.64:1 , and 1.53:1 . In Exp . 2 , 120 pigs ( initial average BW : 29.45 ± 2.15 kg ) were placed in metabolism crates and r and omly allotted to the 20 diets in 6 blocks with 1 pig per diet in each block . Fecal and urine sample s were collected . Results indicated that the predicted maximum retention of Ca in the body at STTD P concentrations of 0.15 , 0.31 , 0.39 , and 0.47 % were 4.7 , 7.1 , 8.6 , and 10.2 g/d at STTD Ca concentrations of 0.77 , 0.96 , 1.06 , and 1.15 % , respectively , which correspond to STTD Ca : STTD P ratios of 5.13:1 , 3.10:1 , 2.72:1 , and 2.45:1 . These observations indicate that if STTD P meets or exceeds the requirement , the STTD Ca : STTD P ratio needed to maximize ADG and G : F by 25 to 50 kg pigs is between 1.16:1 and 1.43:1 . However , a greater ratio may be needed to maximize bone ash or Ca retention Background Systematic Review s ( SRs ) of experimental animal studies are not yet common practice , but awareness of the merits of conducting such SRs is steadily increasing . As animal intervention studies differ from r and omized clinical trials ( RCT ) in many aspects , the methodology for SRs of clinical trials needs to be adapted and optimized for animal intervention studies . The Cochrane Collaboration developed a Risk of Bias ( RoB ) tool to establish consistency and avoid discrepancies in assessing the method ological quality of RCTs . A similar initiative is warranted in the field of animal experimentation . Methods We provide an RoB tool for animal intervention studies ( SYRCLE ’s RoB tool ) . This tool is based on the Cochrane RoB tool and has been adjusted for aspects of bias that play a specific role in animal intervention studies . To enhance transparency and applicability , we formulated signalling questions to facilitate judgment . Results The result ing RoB tool  for animal studies contains 10 entries . These entries are related to selection bias , performance bias , detection bias , attrition bias , reporting bias and other biases . Half these items are in agreement with the items in the Cochrane RoB tool . Most of the variations between the two tools are due to differences in design between RCTs and animal studies . Shortcomings in , or unfamiliarity with , specific aspects of experimental design of animal studies compared to clinical studies also play a role . Conclusions SYRCLE ’s RoB tool is an adapted version of the Cochrane RoB tool . Widespread adoption and implementation of this tool will facilitate and improve critical appraisal of evidence from animal studies . This may subsequently enhance the efficiency of translating animal research into clinical practice and increase awareness of the necessity of improving the method ological quality of animal studies
target: These outcomes advance the current underst and ing 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
background: Ca digestibility and utilisation in growing pigs are not well understood , and are usually neglected in diet formulation .
  This has implication s 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 .