Effect of linoleic and linolenic acid sources supplementation on in vitro rumen fermentation characteristics and microbial diversity

Abstract Text: An in vitro experiment was conducted to estimate the effects of oil sources on rumen fermentation characteristics and microbial diversity. Oil sources were corn oil (CO), linseed oil (LSO) and Ca-salts of linoleic acid (CaSalt). Rumen fluid was collected from 2 canulated Hanwoo steers fed rice straw and concentrate mixture in 2:8 ratio. Incubation was performed in 50 ml glass serum bottles containing 150 mg of synthetic diet (411 g cellulose, 411 g starch, and 178 g casein/kg DM), 7 mg (µl) of either oil sources, and 15 ml of incubation medium (rumen fluid + Van Soest medium = 1:2) at 37 ^oC for 0, 3, 6, 12 and 24 h with 5 replications and 5 blanks for each time period. After 24 h of incubation, total gas volume and the concentrations of ammonia-N and total VFA were unaffected (P>0.05). The pH was higher (P=0.024) in CaSalt with a concomitant lower in lactate concentration (P=0.001). Acetate concentration was significantly higher in CaSalt (P=0.013), but propionate concentration was higher in CO than that in others (P=0.007). Concomitantly, acetate to propionate ratio was higher in CaSalt than in CO (P=0.016). The real time PCR analysis was conducted for relative quantification of microbial DNA. At 12 and 24 h of incubation, F. succinogens, R. flavefaciens, and R. albus were significantly higher (P<0.05) in CaSalt than those in CO and LSO. However, S. boviswas observed higher in LSO at both of those time periods (P<0.05). On the other hand, after 24 h, Methanogenic archaea and ciliate protozoa was highest in LSO and CO, respectively (P<0.005). It is concluded that CaSalt showed lowered rumen methanogenic archaea and ciliate protozoa, while less toxic effects on fibrolytic bacteria compared to other oil sources, as also evidenced from higher acetate production in this treatment.

Keywords: Corn oil, Linseed oil, Ca-salts of linoleic acid, Rumen fermentation, Rumen microbes.