Aroma Profile, Microbial and Chemical Quality of Ensiled Green Forages Mixtures of Winter Cereals and Italian Ryegrass

Abstract

The objective of this study was to evaluate the aroma profile, microbial and chemical quality of winter cereals (triticale, oats, barley and wheat) and Italian ryegrass (Lolium multiflorum Lam., IRG) plus winter cereal mixture silages detected with an electronic nose. Four commercial mixtures (mixture A (40% of two cultivars of winter triticale + 30% of two cultivars of winter oats + 20% of winter barley + 10% of winter wheat), mixture B (50% of two cultivars of winter triticale + 40% of winter barley + 10% of winter wheat), mixture C (55% of three types of Italian ryegrass + 45% of two cultivars of winter oat), mixture D (40% of three types of Italian ryegrass + 30% of two cultivars of winter oat + 15% of two cultivars of winter triticale + 10% of winter barley + 5% of winter wheat)) were harvested, wilted and ensiled in laboratory-scale silos (n = 80) without additives. Both the principal component analysis (PCA) score plot for aroma profile and linear discriminant analysis (LDA) classification revealed that mixture D had different aroma profile than other mixture silages. The difference was caused by the presence of high ethanol and LA in mixture D. Ethyl esters such as ethyl 3-methyl pentanoate, 2-methylpropanal, ethyl acetate, isoamyl acetate and ethyl-3-methylthiopropanoate were found at different retention indices in mixture D silage. The low LA and higher mold and yeast count in mixture C silage caused off odour due to the presence of 3-methylbutanoic acid, a simple alcohol with unpleasant camphor-like odor. At the end of 90 days fermentation winter cereal mixture silages (mixture A and B) had similar aroma pattern, and mixture C was also similar to winter cereal silages. However, mixture D had different aromatic pattern than other ensiled mixtures. Mixture C had higher (p < 0.05) mold and yeast (Log10 CFU (colony forming unit)/g) counts compared to mixture B. Mixture B and C had higher acetic acid (AA) content than mixture A and D. The lactic acid (LA) content was higher for mixture B than mixture C. In general, the electronic nose (EN) results revealed that the Italian ryegrass and winter cereal mixtures (mixture D) had better aroma profile as compared to winter cereal mixtures (mixture A and B). However, the cereal mixtures (mixture A and B) had better aroma quality than mixture C silage. Otherwise, the EN technology is suitable in finding off odor compounds of ensiled forages.

Near‐infrared spectroscopy for rapid evaluation of winter cereals and Italian ryegrass forage mixtures

“…This can be related to the stage of maturity and chemical composition of the plants at this phase of growth. The third cut in Mixtures A and B was closer to a less mature stage, while in Mixtures C and D, the third cut was closer to a more mature stage as observed by Worku, Tóth, et al (2021) in an earlier study involving the nutritional composition of these forage mixtures at different phenological phases (Table 1). Cut 3 represented the stage where the samples containing Italian ryegrass separated the most from those containing winter cereals only as also demonstrated by Figure 2b showing the same PCA scores colored by the four different mixtures.…”

“…From the loading plots (b,d), it could be observed that sugar content (CH bonds, at 2350 nm) (Workman & Weyer, 2012) was the most prominent component causing the difference between the two clusters, not including and including Italian ryegrass (Mixtures A and B and Mixtures C and D, respectively). As confirmed by the chemical analysis, Mixture B had significantly lower CF and NDF content on Day 90, compared with Mixtures A, C, and D (Worku, Tóth, et al, 2021).…”

“…Again, at Day 90, a high CF content that was associated with high pH and low lactic acid concentration 4.08 (%DM) was recorded (Worku, Tóthi, Orosz, Fébel, Kacsala, Vermeire, & Tóth, 2021), probably caused by restricted fermentation which mostly result in low acidification (Kung, 2018). In a related study by Worku, Tóth, et al (2021) that evaluated the aroma profile of the same ensiled forages by means of electronic nose, Mixture D was similarly found to have different aroma profile when compared with the other mixtures at the end of the 90‐day fermentation. The winter cereal mixture silages (Mixtures A and B) had similar aroma profile, as Mixture C was closer to that of Mixtures A and B, based on the PCA score plot and linear discriminant analysis.…”

“…The samples used in this study have also been applied in different studies (Worku, Tóth, et al, 2021; Worku, Tóthi, Orosz, Fébel, Kacsala, Vermeire, & Tóth, 2021) which evaluated the nutritive value of the silage mixtures and aroma profiling using electronic nose.…”

“…In the past years, forage mixtures have been found to provide significant nutritive value compared with whole‐crop silages when used in animal feed formulation (Emile et al, 2005). Again, the poor establishment of corn in areas where climate change have impacted hugely has made it imperative to explore more about the potential of forage mixtures in those areas, in order to advance dairy nutrition (Worku, Tóth, et al, 2021; Worku, Tóthi, Orosz, Fébel, Kacsala, Húth, et al, 2021; Worku, Tóthi, Orosz, Fébel, Kacsala, Vermeire, & Tóth, 2021). Worku, Tóthi, Orosz, Fébel, Kacsala, Vermeire, and Tóth (2021) established that both Italian ryegrass and winter cereal mixtures were well fermented without the use of additives and therefore contributed to eliminating the cost of additives for dairy farmers.…”