Gestating sows with a restricted feed allowance require a longer adaptation period before collecting feces compared with lactating sows in total tract digestibility assessments using index method.

The objective of the present experiment was to determine the minimum adaptation period for total tract digestibility experiments in gestating and lactating sows using the indigestible index method. Five gestating and 5 lactating sows at parities 3 to 5 were used. An indigestible index of 0.5% chromic oxide was supplemented to a diet based on corn and soybean meal. The daily feed allowance for gestating sows was 2 kg and 2 equal meals were provided to the sows. Lactating sows were fed 6 kg of feed per day in 3 equal meals. After feeding a diet without supplemental chromic oxide for 5 d, index-supplemented diets were provided to the gestating and lactating sows. Feces were collected at 24-h intervals for 9 and 7 d from gestating and lactating sows, respectively. Fecal Cr concentrations increased linearly (P < 0.001) and quadratically (P < 0.001) with collection time in both gestating and lactating sows. Minimum adaptation periods were estimated by one-slope broken-line model. The break point of Cr concentrations in feces was day 7.2 (SE = 0.3) in the gestating sows and day 4.2 (SE = 0.2) in the lactating sows, respectively. Apparent total tract digestibility of dry matter, organic matter, and energy on day 4 was less (P < 0.001) than that on days 8 to 9 in gestating sows fed the experimental diet with a 2-kg feed allowance. In lactating sows fed the experimental diets with a 6-kg feed allowance, the apparent total tract digestibility of dry matter, organic matter, and energy on day 3 was less (P < 0.05) than that on days 5 to 7. In conclusion, at least 8 d of adaptation period are required for gestating sows to determine total tract digestibility using Cr as the indigestible index method whereas 5 d of adaptation period are required for lactating sows. An insufficient adaptation period results in lower digestibility values.