Phytase appeared to counterbalance the inimical effect on N balance of acidosis associated with displacing calcium carbonate with calcium chloride in grower pigs

Abstract

The objective of this study was to evaluate CaCl₂ as a Ca source by measuring the balance of Ca, Cl, and P, as well as its effects on plasma and urine chemistry. Six experimental diets were arranged in a 3 × 2 factorial design with 3 Ca sources (limestone, CaCl₂, or their 1:1 mixture) and 2 phytase levels (0, and 1,000 FYT/kg). Each diet was fed to 8 individually housed barrows in metabolism cages, totaling 48 pigs for the study. Fecal and urinary samples were collected quantitatively for 5 days following a 5-day adaptation period. Blood samples were collected from the vena cava at the end of the study. The results showed that plasma glucose concentration was significantly higher in pigs fed CaCl₂ than in pigs fed only limestone. Gradually replacing limestone with CaCl₂ tended to increase plasma concentrations of amylase, K, Na, and P. The supplemental phytase significantly increased plasma P concentration but reduced plasma Ca and blood urea nitrogen concentrations. Urinary pH was significantly lower in pigs fed only CaCl₂ compared to other pigs. Phytase supplementation significantly reduced urinary concentration of Ca, and tended to reduce urinary concentration of N and to increase urinary concentration of P. Increasing inclusion of CaCl₂ in place of limestone resulted in stepwise increases in the apparent total tract digestibility and retention of Ca and P. The Cl intake, output through feces and urine, and retention increased stepwise with higher levels of CaCl₂ (P < 0.05). Phytase significantly decreased Ca and P output through feces and increased their retention. There was a decrease in retention of CP in diet including only CaCl₂ compared to other diets without phytase, but an increase in the presence of phytase. In conclusion, the current study shows that CaCl₂ has higher Ca bioavailability than limestone and can reduce urinary pH, potentially reducing emission of NH₃ from slurry. However, the accumulation of Cl in pigs can disrupt the systemic acid-base balance and might cause damage to some organs such as the pancreas. Therefore, CaCl₂ can be used as a Ca source only if its Cl contribution does not endanger dietary electrolyte balance. Additionally, phytase appeared to ameliorate the inimical effect of acidosis associated with CaCl₂ supplementation on N balance.