Determination of Adequate Adaptation Period in Total Tract Digestibility Studies Using Index Method in Lactating and Gestating Sows

Index methods are often employed in determining nutrient digestibility of sows due to the difficulties of quantitative fecal collection. A sufficient amount of time for reaching a constant index concentration in feces is critical in digestibility experiments. However, information on the adequate adaptation period for reaching the plateau of fecal index concentrations is lacking, particularly in sows. Therefore, the objective was to determine the minimum adaptation period in total tract digestibility experiment using index method of sows. Five lactating and 5 gestating sows with over 3-parities were housed in a commercial farm and used to determine the day for index-recovery. Indigestible indexes of 0.5% chromic oxide and 0.5% titanium dioxide were included to a diet based on corn and soybean meal. The daily feed allowance of lactating sow was at 6 kg and 3 equal meals were provided. Gestating sows were fed with 2 kg of feed per day with 2 equal meals. Following a 5-d period of feeding an index-free diet, feces were collected with 24-h intervals for 7 and 9 d for lactating and gestating sows, respectively. As collection days passed, the fecal index concentration increased quadratically (P < 0.01) in both lactating and gestating sows. Minimum adaptation periods were estimated by one-slope broken-line model, quadratic model, and quadratic broken-line model. Based on the R², the best-fitting model to determine the minimum adaptation period in lactating and gestating sows was the quadratic broken-line model and the one-slope broken-line model, respectively. The breakpoints of Cr and Ti concentration in feces were d 5.08 (SE = 0.48) and 4.67 (SE = 0.83) in lactating sows, respectively, and d 7.28 (SE = 0.31) and 6.16 (SE = 0.42) in the gestating sows, respectively. Based on the results of the present study, the recommended minimum adaptation period for reaching plateau of Cr and Ti concentration in feces was d 6 and 5 in lactating sows, respectively. For gestating sows, the minimum adaptation period for reaching plateau of Cr and Ti concentration in feces was d 8 and 7, respectively. Taken together, the minimum adaptation period in total tract digestibility study using index method in gestating sows was longer than in lactating sows.