Personne : Chouinard, Yvan
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Université Laval. Institut des nutraceutiques et des aliments fonctionnels
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- PublicationRestreintEffects of abomasal infusion of conjugated linoleic acids, Sterculia foetida oil, and fish oil on production performance and the extent of fatty acid Δ9-desaturation in dairy cows(American Dairy Science Association, 2014-07-23) Taga, Hajer; Chouinard, Yvan; Corl, Benjamin; Richard, François J.; Lebeuf, Yolaine; Dallaire, Marie-PierreThe purpose of this study was to determine the effects of conjugated linoleic acid (CLA), Sterculia foetida oil (STO), and fish oil (FO) on milk yield and composition, milk FA profile, Δ(9)-desaturation activity, and mammary expression of 2 isoforms of stearoyl-coenzyme A desaturase (SCD-1 and SCD-5) in lactating dairy cows. Eight multiparous Holstein cows (69 ± 13 d postpartum) were used in a double 4 × 4 Latin square design with 28-d periods. For the first 14 d of each period, cows received an abomasal infusion of (1) 406 g of a saturated fatty acid (SFA) supplement (112 g of 16:0 + 230 g of 18:0) used as a control (CTL), (2) 36 g of a CLA supplement (13.9 g of trans-10,cis-12 18:2) + 370 g of SFA, (3) 7 g of STO (3.1g of 19:1 cyclo) + 399 g of SFA, or (4) 406 g of FO (55.2 g of cis-5,-8,-11,-14,-17 20:5 + 59.3 g of cis-4,-7,-10,-13,-16,-19 22:6). Infusions were followed by a 14-d washout interval. Compared with CTL, STO decreased milk yield from 38.0 to 33.0 kg/d, and increased milk fat concentration from 3.79 to 4.45%. Milk fat concentration was also decreased by CLA (2.23%) and FO (3.34%). Milk fat yield was not affected by STO (1,475 g/d) compared with CTL (1,431 g/d), but was decreased by CLA (774 g/d) and FO (1,186 g/d). Desaturase indices for 10:0, 12:0, and 20:0 were decreased, whereas the extent of desaturation of 14:0, 16:0, 17:0, and 18:0 was not affected by CLA treatment compared with CTL. Infusion of STO significantly decreased all calculated desaturase indices compared with CTL; the 14:0 index was reduced by 80.7%. Infusion of FO decreased the desaturase indices for 10:0, 14:0, 20:0, trans-11 18:1, and 18:0. The effect of FO on the 14:0 index indicates a decrease in apparent Δ(9)-desaturase activity of 30.2%. Compared with CTL, mammary mRNA abundance of SCD-1 was increased by STO (+30%) and decreased by CLA (-24%), whereas FO had no effect. No effect was observed on mRNA abundance of SCD-5. In conclusion, abomasal infusion of CLA, STO, and FO were shown to exhibit varying and distinct effects on desaturase indices, an indicator of apparent SCD activity, and mammary mRNA abundance of SCD-1.
- PublicationAccès libreEffect of two thermoresistant non-starter lactic acid bacteria strains on volatilome profile during Cheddar ripening simulation(Elsevier, 2021-09-03) Roy, Denis; Gagnon, Mérilie; Goulet, Charles; LaPointe, Gisèle; Chouinard, YvanDairy farm management practices can modify milk microbiota and therefore modulate non-starter lactic acid bacteria (NSLAB) found in cheese. These NSLAB can cause organoleptic defects. This study aimed to investigate the impact of two potential NSLAB in Cheddar cheesemaking: Lactiplantibacillus plantarum RKG 2-212 a strain isolated both in corn silage and raw milk, and Lactobacillus delbrueckii RKG R10, a strain isolated after pas-teurisation of milk from a farm using grass and legume silage, and corn silage. The whole genome of these two lactobacilli was first sequenced. Then, the thermoresistance was evaluated after treatment at 60 ◦C for 5 min and compared to reference strains. Both lactobacilli were highly thermoresistant compared to other three lactic acid bacteria which are Lactococcus lactis subsp. cremoris ATCC 19257 and SK11, and L. plantarum ATCC 14917 (P <0.0001). They lost less than 1 log cfu/mL (Δlog) and their genome contained a great number of copy number of genes coding for heat shock protein. During a Pearce test activity simulating Cheddar cheesemaking, the two lactobacilli did not show interaction with the starter Lcc. lactis subsp. cremoris SK11, and their population remained stable. During a ripening simulation, L. delbrueckii RKG R10 had a slight loss in viability in cheese slurry samples incubated at 30 ◦C for 12 d. However, L. plantarum RKG 2–212 had considerable growth, from 6.51 to 8.3 log cfu/g. This growth was associated with the acidification of the slurries (P <0.0001). The presence of the lactobacilli modified the profile of volatile compounds evaluated by gas chromatography–mass spec-trometry, accounting for 10.7% of the variation. The strain L. plantarum RKG 2-212 produced volatile compounds in greater quantity that could be associated with organoleptic defects such as acetic acid and 2-methylbutyral-dehyde. Therefore, silage can be a vector of thermoresistant lactic acid bacteria for milk which can lead to flavor defects in cheese
- PublicationAccès librePrevalence and abundance of lactic acid bacteria in raw milk associated with forage types in dairy cow feeding(Elsevier Inc., 2020-04-29) Roy, Denis; Groleau, Gisèle.; Gagnon, Mérilie; Chouinard, Yvan; Ouamba, Alexandre J. K.Lactic acid bacteria (LAB) found in milk can be responsible for organoleptic defects in cheese. In order to identify the source of LAB thatcouldpotentiallydevelop during cheesemaking, we evaluated theirprevalence and abundanceinmilk according to thetype of forage usedin dairy cow feeding. Foragesand bulk tank milk were sampled three times on 24farms using either hay alone (control), or grass or legume silagesupplemented or not with corn silage. Both types of silageswere either noninoculated, orinoculated with commercial preparations containing at least a Lactobacillus buchneristrainalong with Lactobacillus casei, Lactobacillus plantarum, Enterococcus faecium,or Pediococcus pentosaceus. Our resultsindicate that LAB viable counts in milksamples (2.56log cfu/mL) did not differaccording to the type of forage used. A total of 1239 LAB were isolated and identified by partial 16S rRNA gene sequencing. Although inoculation increased lactobacilli abundance in grass silage by 35%, we did not observe an effect on the LAB profile of milk. Indeed, there was no significant difference in milk LAB prevalence and abundanceaccording tothe type of forage(P >0.05). Moreover, isolates belonging to the L.buchnerigroup wererarely found in bulk tank milk (3/481isolates). Random amplified polymorphic DNA typing of 406LAB isolates revealed theplausibletransfer of some strains from silage to milk (~6%). Thus, forage is only a minor contributor to LAB contamination of milk.