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

Abstract

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.

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 basal endogenous loss of Ca in sows during midgestation if no phytase was used (1,196 mg/ kg DMI) was close to the value (1,580 mg/kg DMI) reported by Lee et al (2018). However, the basal endogenous loss of Ca from growing pigs fed a cornbased Ca-free diet was between 329 (Merriman and Stein, 2016) and 550 mg/kg DMI (González-Vega et al, 2015b;Merriman, 2016;Blavi et al, 2017), and the present result along with the data by Lee et al (2018) confirms that gestating sows have much greater basal endogenous loss of Ca than growing pigs if measured as mg per kg DMI.…”

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

“…Values for the ATTD of P in the Ca-free diets that were formulated based on corn and monosodium phosphate without and with phytase were in agreement with expected values (NRC, 2012;González-Vega et al, 2015a;Blavi et al, 2017). However, the ATTD of P in the Ca carbonatecontaining diets was less than the ATTD of P in the Ca-free diets.…”

Effect of Zinc Source and Exogenous Enzymes Supplementation on Zinc Status in Dogs Fed High Phytate Diets

“…The results of the present study showed that the digestibility of P was enhanced with Zn proteinate supplementation. Two studies reported that over-supplementation with Zn-oxide decreased P digestibility in pigs [37,38], suggesting that P uptake was decreased by inorganic Zn, a phenomenon that was already described in plants [38], or that precipitation in the intestinal lumen of P and Zn might have occurred. However, in the present study, this is not supported by the zinc biomarkers evaluated and is unlikely to have occurred with the lower level of Zn supplied compared to the earlier studies.…”