The validation of infrared thermography as a non-invasive tool to assess welfare in the horse (Equus caballus)

IntroductionThe relatively high saturated fatty acid (SFA) content in milk fat has raised criticism in the past since it is assumed to be associated with negative effects on human health, especially due to the presence of C12:0, C14:0 and C16:0.On the other hand, monounsaturated fatty acids (MUFA), such as c9 C18:1 (oleic; OA) and t11 C18:1 (vaccenic; VA) and polyunsaturated fatty acids (PUFA), such as n-3 and n-6 groups and c9t11 conjugated linoleic acid (CLA9) found in milk, have been linked to beneficial effects on human health (Haug et al. 2007).c9c12c15 C18:3 (ALN) and c9c12 C18:2 (LA) are the main n-3 and n-6 FA in milk respectively.Differences in milk fatty acid composition between different dairy management systems in UK, such as conventional, organic and low input, have been reported in other studies (Butler et al. 2008; Ellis et al. 2006).Grazing intake, silage and sward composition, forage:concentrate ratio and oilseed supplementation, all factors that widely vary between management systems, can be responsible for milk fat compositional differences (Dewhurst et al. 2006).In a previous study, a stronger effect on milk fatty acid composition was found when the differences on grazing intake between management systems were more extreme.The comparison between low input and conventional milk showed higher differences in milk fatty acid composition than when conventional milk was compared with organic (Butler et al. 2008).The aim of this study was to investigate and explain possible differences in milk fatty acid composition between farms under different management practices in the North East of England. Material and methodsMilk from the bulk tank of 20 farms in the North East of England, representing 4 different management systems, was collected every 8 weeks for 10 month period.Conventional systems are characterized by an average of 41% of their diet as concentrates, with conserved forage fed while animals are fully housed during winter but access to ryegrass pasture when conditions allowed in summer.In organic systems, cows graze in ryegrass/clover swards, usually between April and October, and are housed in winter, with an average 22% concentrate supplementation.On intensive farms, cows are milked 3 times per day, nutrition is consistent throughout the year and is based on silage, which in that case may also contain maize silage, and 49% concentrates.Farms that apply robotic milking were selected to have the same feeding practices as conventional farms in order to investigate the effect of milking procedure.Analysis of FA methyl esters was performed with a Gas Chromatography system (Shimadzu, GC-2014, Japan) using a Varian CP-SIL 88 fused silica capillary column (100m x 0.25mmID x 0.2µm film thickness).Peaks were identified using a 39 FAME and CLA isomer standards.Analysis of variance (ANOVA) using linear mixed effects model (LME) was used to analyze results in R statistical environment using "Management system" (conventional, organic, intensive, robotic) and "sampling month" (7 sampling months over one year) as fixed factors and farm number as random factor. ResultsCompared to conventional milk, organic milk showed significantly higher concentrations of C14:0, ALN, n-3 and n-3:n-6 ratio while milk from intensive farms showed higher milk n-6 concentrations.When organic milk was compared to milk from intensive farms, significantly higher concentrations of C14:0, VA, CLA9, ALN, n-3, higher n-3:n-6 ratio and significantly lower concentrations of LA were found.Robotic milking farms showed significantly higher milk concentrations of C12:0 and C14:0 and lower concentrations of CLA9 than conventional farms.Table 1 Relative proportions (%) of individual fatty acids and fatty acid groups in milk from organic, intensive and robotic farms compared with milk from conventional farms C12:0 C14:0 C16:0 Oleic VA CLA9 ALN LA SFA MUFA PUFA n-3 n-6 n-3:n-6 Organic +9.7 ab +8.4 a -6.5 -3.6 +15.2 a +6.7 a +76.3 a -12.0 b +0.8 -3.1 +7.0 a +69.4 a -11.0 b +84.0 a Intensive -0.9 b -0.8 b +2.2 -3.6 -21.6 b -21.6 b -18.8 b +28.7 a +1.4 -4.9 +9.8 a -18.2 b +28.2 a -35.1 c Robotic +16.8 a +8.1 a -1.1 -4.9 -20.0 b -25.2 b -1.7 b -14.2 b +2.7 -5.4 -13.2 b -2.9 b -12.3 b -16.9 b P-values

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