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

• Published in: Animal feed science and technology Vol. 261; p. 114411
• Main Authors: Passetti, Rodrigo A.C., Passetti, Ludmila C.G., Gruninger, Rob J., Ribeiro, Gabriel O., Marami Milani, Mohammed R., Prado, Ivanor N., McAllister, Tim A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2020
• Subjects: Acetamide; AFEX; Lamb; Microbiome; Rice straw; Rumen; A; RS; aNDF; ARS; B; Kp; AFEX; Rice straw; Rumen; ARSW; Acetamide; Lamb; A+B; Kd; ALF; ED; Microbiome
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/j.anifeedsci.2020.114411

•Ammonia fibre expansion (AFEX) improved the digestibility of rice straw fibre.•Microbial profile of initial biofilms on AFEX rice straw resembled alfalfa.•AFEX straw lowered dry matter intake and feed efficiency compared to alfalfa.•Withdraw of AFEX straw for 3 days reduced acetamide in blood, but not muscle.
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1) ALF = 250 g/kg of alfalfa; 2) RS = 250 g/kg of rice straw; 3) ARS = 250 g/kg of AFEX rice straw; 4) ARSW = ARS withdrawn from the diet 7 d before slaughter.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 < 0.05), whereas ARS had higher (P < 0.05) B and A + B fractions. Alfalfa DM and NDF degradability was greater at 12 h, but lower than ARS thereafter. Effective ruminal degradability (Ed) at 0.02, 0.04 and 0.06/h was greater (P < 0.05) for ARS than other forages. Digestion of ALF and ARS plateaued after 48 h, while RS continued to be degraded. Compared to other forages, alpha and beta microbial diversity of ARS was reduced (P < 0.05). The phylogenetic profile of initial colonizers of ARS was more similar to ALF than RS and was dominated by Bacteroidetes. Lambs fed RS exhibited similar growth to those fed ALF, while the DMI of ARS lambs was similar, but ADG and feed efficiency were reduced (P < 0.05). ALF exhibited greater (P < 0.05) DM, OM, CP, NDF, ADF and starch digestibility than ARS. ARS exhibited lower CP, but higher NDF and ADF digestibility than RS. A strong correlation (R² = 0.81) was observed between blood and muscle acetamide levels in lambs fed ARS. Withdrawal of ARSW reduced (P < 0.05) blood acetamide levels after 3 d, but levels in the diaphragm remained similar to ARS lambs at slaughter. Although AFEX improved the NDF and DM digestibility of RS and altered the phylogenetic profile of primary colonizers, it did not improve the growth of ewe lambs, likely as a result of reduced intake.