Effects of limestone particle size and dietary Ca concentration on apparent P and Ca digestibility in the presence or absence of phytase

Abstract

The present study evaluated the effects of limestone particle size and Ca concentration on apparent ileal digestibility (AID) of P and Ca in the presence or absence of a 6-phytase derived from Buttiauxella sp., expressed in Trichoderma. Treatment diets were corn-soybean meal (SBM) based with no added inorganic Ca or P. The design consisted of a factorial arrangement of 2 particle sizes of limestone from the same source (mean particle size: pulverized, PUV < 75 μm; particulate, PAR = 402 μm); 3 Ca (0.6, 0.8, and 1.0%) and 2 phytase levels (0 and 1,000 (FTU)/kg) plus the corn-SBM basal diet with no added Ca (0.14% Ca), resulting a total of 13 treatments (Trts, n = 9, 3 birds/n). Starting at 27 d of age, broilers were fed the mash diets for 32 h, then sampled for gizzard pH and distal ileal digestibility. Gizzard pH was 1.94 in birds fed diet without added Ca and was similar to those fed diet with PAR limestone regardless of phytase. Gizzard pH was increased in birds fed PUV limestone diets irrespectively of phytase inclusion compared to birds fed 0.14% Ca (P < 0.05), except in birds fed 0.60% Ca diet. In the absence of phytase, AID P was reduced as a result of increases in limestone inclusion (P < 0.05), with a greater effect seen in PUV as compared to PAR limestone. The AID Ca in birds fed PUV limestone diets was lower than that of those fed PAR limestone diets (22.1% vs. 28.2%; P < 0.05). In the presence of phytase, the AID P was not affected by increasing Ca concentration when PAR limestone was used as the Ca source (average = 64.3%), whereas AID P decreased from 66.9% (0.6% Ca) to 51.0% (1.0% Ca) when PUV limestone was used as the Ca source (P < 0.05). In summary, impact of Ca concentration on AID Ca and P was dependent on limestone particle size and phytase inclusion.

Coarse limestone does not alleviate the negative effect of a low Ca/P ratio diet on characteristics of tibia strength and growth performance in broilers

“…It, therefore, seems possible to reduce the dietary Ca/P ratio through the use of coarse limestone while maintaining growth performance and bone development. In addition, in the presence of microbial phytase, ileal P digestibility was reduced by pulverized limestone (particle size < 75 μm), whereas it was not affected by the particulate limestone (particle size 402 μm) ( Kim et al., 2018 ). The P digestion seems to be related to the particle size of limestone, and the coarser limestone may have a less negative impact on P digestion.…”

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

“…The Ca requirement in modern broilers has been recently reported ( Applegate et al., 2003 , Li et al., 2012 , Li et al., 2015 , Li et al., 2016 , Li et al., 2016 , Abdulla et al., 2017 , Kim et al., 2018b ). The heightened interest in dietary Ca-related studies is due to its effect on phytase efficacy.…”

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

“…Differences in the digestibility of Ca are not likely a result of differences in particle size because there appears to be no influence of particle size on digestibility of Ca in Ca carbonate (Merriman and Stein, 2016) or on bioavailability of Ca in Ca carbonate (Ross et al, 1984). Solubility of Ca carbonate may affect Ca utilization in poultry (Zhang and Coon, 1997b;Kim et al, 2018), but ATTD and STTD of Ca in the 4 sources of Ca carbonate used in this experiment were not correlated with solubility (data not shown).…”