Effect of ammonia fibre expansion (AFEX) treatment of rice straw on in situ digestibility, microbial colonization, acetamide levels and growth performance of lambs

Abstract The objective of this study was to evaluate the effect of AFEX treatment (ARS) of rice straw (RS) on the in situ degradability, microbial colonization, growth performance and acetamide levels in ewe lambs. Alfalfa, rice straw and AFEX-treated rice straw were incubated in nylon bags in the rumen for 0, 1, 3, 6, 12, 24, 36, 48, 72 and 120 h to determine DM and NDF disappearance kinetics. Sequencing of 16S rRNA was used to characterize colonizing bacterial and archaeal profiles. Lambs (N = 40; 37.1 ± 3.5 kg) were fed pelleted diets that contained: 1) ALF = 250 g/kg of alfalfa; 2) RS = 250 g/kg of rice straw; 3) ARS = 250 g/kg of AFEX rice straw; 4) ARSW = ARS withdrawn from the diet 7 d before slaughter. Blood samples were collected biweekly and after ARSW on d 1, 3, 5 and 7 and at slaughter, the diaphragm muscle was used for measurement of acetamide. Alfalfa had greater Kd and A fraction (P