Digestibility of calcium and phosphorus and effects of microbial phytase in diets fed to growing pigs or gestating sows

calcium;phosphorus;microbial phytase;phytate;pig;sows

Lee, Su A

关键词: calcium;    phosphorus;    microbial phytase;    phytate;    pig;    sows;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/107852/LEE-DISSERTATION-2020.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Five experiments were conducted to determine Ca digestibility in feed ingredients and to demonstrate the interactions among Ca, P, and phytase in diets fed to gestation sows or growing pigs. In Exp. 1, 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 calcium carbonate and that the STTD of Ca is constant among different sources of dicalcium phosphate (DCP) when fed to growing pigs. Results indicated that there were no interactions between phytase and source of calcium carbonate. Values for STTD of Ca in calcium carbonate were greater (P < 0.001) for diets containing microbial phytase compared with diets without exogenous phytase, but values for STTD of Ca differed (P = 0.006) among the 4 sources of calcium carbonate. Values for STTD of Ca in DCP appears to be constant regardless of origin. In Exp. 2, the objective was to determine correlations between individual bones in the body and total bone ash to identify the bone that is most representative of total body bone ash in growing pigs. Pigs were fed diets containing 60 or 100% of the requirement for STTD Ca and STTD P. Results indicated that growth performance of pigs and bone ash were negatively affected by dietary Ca and P below the requirement. Metacarpals, metatarsals, and tibia were more representative of total body bone ash compared with femur, fibula, and ribs. Experiment 3 was conducted to test the hypothesis that there are no differences between gestating sows and growing pigs for STTD and retention of Ca and P. Two diets containing normal- or high-phytate were fed to growing pigs and gestating sows. Phytate level did not affect the STTD of Ca or Ca retention by gestating sows whereas the STTD of Ca and Ca and P retentions 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). Regardless of phytate level, gestating sows had reduced digestibility and retention of Ca and P compared with growing pigs. Experiment 4 was conducted to test the hypothesis that the STTD of Ca and the response to microbial phytase on STTD of Ca, apparent total tract digestibility (ATTD), and retention of Ca and P does not change during gestation. Throughout gestation, sows were fed 4 diets that were Ca-free diet or a corn-based diet in which Ca carbonate was the sole source of Ca without or with microbial phytase. Results indicated that there were no interactions between period of gestation and dietary phytase. Supplementation of microbial phytase did not affect STTD of Ca, Ca retention, ATTD of P, or P retention in sows fed the calcium carbonate-containing diet. The ATTD of Ca, the ATTD of P, and the retention of Ca were least (P < 0.05) in mid-gestation, followed by early- and late-gestation, respectively, and the STTD of Ca in mid-gestation 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 Exp. 5, the objective was to test the hypothesis that the Ca level in diets fed to late gestating sows affect the ATTD and retention of Ca and P, blood Ca and P, serum concentrations of hormones, and blood biomarker for bone synthesis and resorption. Sows in late-gestation were fed one of 4 experimental diets containing 25, 50, 75, or 100% of the requirement for Ca with a constant level of P. Results indicated that values for the ATTD of Ca increased quadratically (P = 0.039) as Ca in diets increased. Calcium retention increased quadratically (P < 0.05) as Ca intake increased. The ATTD of P linearly decreased (P < 0.001), but P retention increased as dietary Ca increased. Serum concentrations of Ca and P and estrogen, calcitonin, and parathyroid hormone were not affected by Ca concentrations in diets. The ratio between serum osteocalcin and carboxyterminal cross-linked telopeptide of type I collagen tended to increase (P = 0.055) as dietary Ca increased, which indicated that there was more bone formation than resorption in sows as dietary Ca increased. In conclusion, the STTD of Ca in calcium carbonate differed among different suppliers, but the STTD of Ca in DCP did not vary depending on different suppliers. Tibia, metacarpals, and metatarsals were the best indicators to predict total body bone ash. Gestating sows had much lower values for STTD of Ca and P than growing pigs and effects of microbial phytase on digestibility of Ca and P were much less predictable in gestating sows than in growing pigs. A wide Ca:P ratio decreased ATTD of P, but increased ATTD of Ca and retention of Ca and P in sows in late-gestation. Additional research is needed to determine the STTD of Ca and P in feed ingredients fed to sows and to elucidate interactions among dietary Ca and P, phytase, phytate, and biomarkers in both sows and growing pigs.