The effect of dietary Chlorella vulgaris supplementation on micro‐organism community, enzyme activities and fatty acid profile in the rumen liquid of goats

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Microalgae, despite being more popular for biofuel production (Medipally et al., 2015), have also gained more attention as a source of biomolecules such as n‐3 polyunsaturated fatty acids (PUFA), phenols, flavonoids (Goiris et al., 2012; Lum et al., 2013; Yaakob et al., 2014). Thus, the inclusion of microalgae in ruminant's diets has been shown as an effective nutritional strategy to enrich milk with PUFA of bovine (Glover et al., 2012) and goats (Kouřimská et al., 2014). However, modifications on milk fatty acid (FA) profile, in response to dietary supplementation with microalgae, may be accompanied by alterations in ruminal biohydrogenation (BH) process. Indeed, it has been observed that alterations in the formation of specific BH intermediates (FA) in the rumen, after dietary microalgae supplementation, are associated with changes in specific population of ruminal bacteria and protozoa in cattle (Boeckaert et al., 2007, 2008). Nevertheless, no information exists so far on the effect of microalgae on the abundance of micro‐organisms involved in ruminal BH process.
Furthermore, microalgae with high‐fat content could be, also, considered as possible candidates to reduce methane (CH4) production in ruminants, although this has been investigated so far only in vitro (Fievez et al., 2007). This may happen because lipids, and especially PUFA, have antimicrobial effects on methanogens and protozoa because it can disrupt their cell membrane (Jenkins et al., 2008; Martin et al., 2010). While the in vitro results of microalgae supplementation with high‐fat content on CH4 emission appear promising, the opposite seems to occur with microalgae rich in protein and low in fat content. Besides, in a recent in vitro study, Dubois et al. (2013) observed that algae with a very high level of protein content increased gas production in the rumen. Thus, it is clear that in vivo studies are required especially using microalgae with high protein content, such as Chlorella vulgaris, to determine their impact on methanogens population in the rumen. This assumption was further supported by the fact that recently C. vulgaris has been proposed as a protein source in cows diets (Lodge‐Ivey et al., 2014). Additionally, defatted biomass of microalgae species, derived from biofuel production, has been shown feasible in replacing corn and soybean meal in cattle diets (Lopex et al., 2013).
Thus, the objectives of this study were to determine the effect of dietary C. vulgaris supplementation on (i) the abundance of micro‐organisms involved in rumen BH process (Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, Ruminococcus albus, Fibrobacter succinogenes Protozoa, Fungi), CH4 (Methanosphaera stadtmanae, Methanobrevibacter ruminantium, Methanogens) and ammonia (Clostridium sticklandii, Peptostreptococcus anaerobius) production, (ii) rumen enzyme (cellulase, protease, lipase and α‐amylase) activities and (iii) rumen FA profile of goats.
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