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Digestibility, retention of Ca and P in sows changes during gestation

Response to microbial phytase on digestibility and retention of Ca and P in Ca- and P-adequate-corn-based diets fed to gestating sows is less predictable than in diets fed to growing pigs.

By Su A Lee and Hans H. Stein, University of Illinois
Digestibility of calcium and phosphorous has been determined for most Ca and P containing ingredients fed to growing pigs, but the digestibility of Ca and P in sows in mid-gestation are less than in growing pigs (Lee et al., 2018). As a consequence, if diets for gestating sows are formulated using digestibility values determined in growing pigs, provisions of digestible Ca may be less than anticipated.

The efficacy of phytase to release Ca and P is believed to be influenced by the physiological state of pigs with phytase fed to sows in mid-gestation releasing less Ca and P compared with growing pigs or sows in late-gestation. However, it is not known if values for digestibility of Ca and P that are measured in one period of gestation are representative for the entire gestation period. Therefore, an experiment was conducted to test the hypothesis that the digestibility and retention of Ca and P and the response to microbial phytase on digestibility and retention of Ca and P in corn and limestone-based diets fed to gestating sows are constant throughout the gestating period for sows.

Experimental diets included a corn-based diet in which limestone was the sole source of Ca and a Ca-free diet. Each diet was prepared with no microbial phytase and also with addition of 500 units of phytase, a product from AB Vista. Daily feed allowance was 1.5 times the maintenance energy requirement for gestating sows based on the body weight of sows. Daily feed allotments were provided in two equal meals. Water was available at all times.

Sows were housed individually in gestation stalls throughout gestation with the exception that from Day 7 to 20 (early-gestation), Day 49 to 62 (mid-gestation) and again from Day 91 to 104 (late-gestation), sows were housed individually in metabolism crates, where they were fed one of the four experimental diets. Feces and urine were quantitatively collected to calculate digestibility and retention of Ca and P.

Supplementation of microbial phytase decreased the basal endogenous loss of Ca (Table 1). The basal endogenous loss of Ca was greatest by sows in early-gestation, followed by sows in mid- and late-gestation periods, respectively.

Table 1: Basal endogenous loss of Ca from early-, mid- and late-gestating  sows fed Ca-free diet

Phytase effects on the basal endogenous loss of Ca, digestibility of dry matter, Ca and P and retention of Ca and P did not change during gestation, and no interactions between phytase and gestation period were observed.

Supplementation of microbial phytase did not affect the digestibility of DM, Ca and P or retention of Ca and P (Table 2). The digestibility of DM was not affected by the period of gestation. However, the digestibility of Ca for sows in mid-gestation was lower than for sows in early- or late-gestation. The digestibility of P and retention of Ca were least in mid-gestation, followed by early- and late-gestation, respectively. Phosphorus retention was greater in late-gestation than in the earlier periods. Thus, these data indicate that digestibility and retention of Ca and P changes during gestation.

Table 2: Digestibility and retention of Ca and P in experimental diets fed to gestating sows

In conclusion, to accurately predict Ca and P absorption in gestating sows, it appears that it is necessary to assume different digestibility and retention values for Ca and P in late-gestation compared with early- or mid-gestation. The response to microbial phytase on digestibility and retention of Ca and P in Ca- and P-adequate-corn-based diets fed to gestating sows is less predictable than in diets fed to growing pigs.

Sources: Su A Lee and Hans H. Stein with the University of Illinois, who are solely responsible for the information provided, and wholly own the information. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

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