Soybean oil and linseed oil supplementation affect profiles of ruminal microorganisms in dairy cows

Abstract

The objective of this study was to evaluate changes in ruminal microorganisms and fermentation parameters due to dietary supplementation of soybean and linseed oil alone or in combination. Four dietary treatments were tested in a Latin square designed experiment using four primiparous rumen-cannulated dairy cows. Treatments were control (C, 60 : 40 forage to concentrate) or C with 4% soybean oil (S), 4% linseed oil (L) or 2% soybean oil plus 2% linseed oil (SL) in a 4 × 4 Latin square with four periods of 21 days. Forage and concentrate mixtures were fed at 0800 and 2000 h daily. Ruminal fluid was collected every 2 h over a 12-h period on day 19 of each experimental period and pH was measured immediately. Samples were prepared for analyses of concentrations of volatile fatty acids (VFA) by GLC and ammonia. Counts of total and individual bacterial groups (cellulolytic, proteolytic, amylolytic bacteria and total viable bacteria) were performed using the roll-tube technique, and protozoa counts were measured via microscopy in ruminal fluid collected at 0, 4 and 8 h after the morning feeding. Content of ruminal digesta was obtained via the rumen cannula before the morning feeding and used immediately for DNA extraction and quantity of specific bacterial species was obtained using real- time PCR. Ruminal pH did not differ but total VFA (110v. 105 mmol/l) were lower (P< 0.05) with oil supplementation compared with C. Concentration of ruminal NH3-N (4.4v. 5.6 mmol/l) was greater (P< 0.05) due to oil compared with C. Compared with C, oil supplementation resulted in lower (P< 0.05) cellulolytic bacteria (3.25 × 108v. 4.66 × 108colony-forming units (CFU)/ml) and protozoa (9.04 × 104v. 12.92 × 104cell/ml) colony counts. Proteolytic bacteria (7.01 × 108v. 6.08 × 108CFU/ml) counts, however, were greater in response to oil compared with C (P< 0.05). Among oil treatments, the amount ofButyrivibrio fibrisolvens,Fibrobacter succinogenesandRuminococcus flavefaciensin ruminal fluid was substantially lower (P< 0.05) when L was included. Compared to C, the amount ofRuminococcus albusdecreased by an average of 40% regardless of oil level or type. Overall, the results indicate that some ruminal microorganisms, except proteolytic bacteria, are highly susceptible to dietary unsaturated fatty acids supplementation, particularly when linolenic acid rich oils were fed. Dietary oil effects on ruminal fermentation parameters seemed associated with the profile of ruminal microorganisms.

Quantitative analysis of ruminal bacterial populations involved in lipid metabolism in dairy cows fed different vegetable oils

“…In this study, ruminal pH and NH 3 -N were not affected by dietary treatments, this partly agrees with the studies by Yang et al (2009) who did not report ruminal pH changes when cows were fed SO and linseed oil, but did observe increases in ruminal NH 3 -N concentration. Benchaar et al (2012) reported no effect on pH, VFA and NH 3 -N when dairy cows were supplemented with linseed oil at 2%, 3% and 4% DM.…”

“…Dietary treatments (Table 1) were a basal diet (Control) containing 56% forage and 44% concentrate ratio with no fat supplement, and fat-supplemented diets containing SO (170 g/day per cow = 2.7% DM) and HPO (170 g/day per cow = 2.7% DM). The amounts of oil used were similar to those reported to alter rumen FA in previous studies (Yang et al, 2009;Vargas-Bello-Perez et al, 2015a). The most important FA in dietary oils were as follows: SO contained (g/100 g) 25 of C18:1 cis-9 and 51 of C18:2 cis n-6, whereas HPO contained 47 of C16:0 and 43 of C18:0.…”

“…In the present study, lack of difference in ruminal fermentation parameters may be due to the amount (almost 3% of DM) of oil incorporated into the basal diet. Differences from other studies such as Yang et al (2009), on the effect dietary oils on ruminal fermentation parameters in dairy cows may be explained by the amount of dietary oil and the Means in the same row with different superscripts are different (P < 0.05). Based on ribosomal operon copy number.…”

“…This is explained by factors such as disruption of microbial cell membranes and cell function caused by PUFA and lipid coating of feed particles (especially fibrous components) and bacteria (Yang et al, 2009). The antimicrobial effect of lipids in the rumen is related to the cytotoxic effects of FA on membrane function of eukaryotic cells (Maia et al, 2010).…”

“…Also, SO has been shown to reduce cellulolytic bacteria, protozoal populations and total concentration of volatile fatty acids (VFA) (Yang et al, 2009). On the other hand, hydrogenated vegetable oils have been used to increase the energy content of dairy cow diets in housed (Kargar et al, 2012) and pasture systems (Schroeder et al, 2002) without effect on milk composition (Vargas-Bello-Perez et al, 2015b).…”