Mean retention time of particulate matter through gastrointestinal tract of growing goat
The objective of this study was to evaluate mean retention time (MRT) of particulate matter through gastrointestinal tract (GIT) of growing goat of different sex and body weight. A total of 58 Saanen goats (20 intact males, 20 castrated males and 18 females) were housed in individual pens with free access to water. Then, the goats of each sex were randomized in 3 different slaughter BW (around 15, 22, 30 kg). They were fed ad libitum with the same diet (45.4 % corn plant hay and 54.6 % concentrate comprised), and diet was offered twice daily at 0700 and 1600 h. The animals were slaughter when reached 16.5 ± 0.9; 22.8 ± 1.3; 31.6 ± 1.5 kg of BW. Then, GIT was removed and separated into reticulorumen, omasum, abomasum, small intestine, cecum and colon. The content of each GIT compartment was sampled. To determine the passage rate, we used the ruminal emptying technique of slaughtered animals. The indigestible NDF (iNDF) was used as internal marker. The concentration of iNDF was determined by incubating the samples in rumen-fistulated cattle per 288 h, using Ankom® bags (F57). The experiment was analyzed as split plot designed (3 sex and 3 slaughter BW) using PROC MIXED of SAS. The effect of slaughter BW was decomposed into 2 orthogonal polynomial contrasts (linear and quadratic) and the effect of sex was compared by Tukey test. The significance was declared at P ≤ 0.05. Sex did not influence the MRT for all compartments (P > 0.05). On average the reticulorumen retention time was 35.8 h (67 % of retention in GIT) and it was similar between sex and BW. As BW increased the MRT in the omasum increased linearly and the MRT in the abomasum decreased linearly (P ≤ 0.05). It was observed a significant interaction between sex and BW for MRT of omasum and colon (P< 0.01). Whereas, females with 22 kg of BW presented lower MRT compared to males (intact and castrated) in the same BW. In conclusion, the increase of BW mainly influenced MRT in the omasum and abomasum compartment. Females present different pattern of MRT for omasum and colon than males.
Keywords: body weight, iNDF, sex