Feeding regimen may significantly affect milk fatty acid compo- sition, by modulating both rumen and mammary lipid metabo- lism. Hence, the aim of the present study was to evaluate milk fatty acid (FA) composition as a marker of the feeding regimen in dairy cow. Individual milk samples of 319 cows were collected from 24 commercial dairy herds (13±4 cows per farm). The ani- mals were selected so as to have individuals homogeneously dis- tributed along the entire period of lactation. Using a standard questionnaire, management and nutritional parameters were recorded. On the basis of questionnaire results, farms were grouped into 4 different feeding regimens: group1 (low level of forage and fat integration), group2 (medium level of forage and fat integration), group3 (high level of forage and fat integra- tion), group4 (high level of forage and no fat integration). Methyl esters of FA were prepared by a direct extraction and alka- li catalyzed transmethylation procedure, followed by gas-chro- matographic analysis. A reference standard butter was used to estimate correction factors for short-chain FA. Data were ana- lyzed by principal component analysis (PCA) to determine how the feeding regimen of the dairy cows and the composition of the milk were differentiated from each other. Data were analyzed by the GLM, with farm, days in milking, season of calving and diet group as main effects. Significance was declared at P<0.05. The mean value for the different variables was an average of all milk samples and was used directly in the PCA plot. In the present study, production data collected from 24 farms showed a large variation in feed intake between and within the 4 feeding regi- mens. The first (PC1) and second (PC2) principal component explained 28% and 12% of variation, respectively. The results showed that the different feeding regimens adopted by farmers, were significantly discriminated according to milk FA composi- tion. In particular, the low level of forage is associated with a higher content of n-6 fatty acids and a high level of n-6/n-3 ratio. Fat integration is related to increasing amount of vaccenic acid and CLA (+25%).
Principal component analysis of milk fatty acid: effect of the different feeding regimens
CONTE, GIUSEPPE;CAPPUCCI, ALICE;
2013-01-01
Abstract
Feeding regimen may significantly affect milk fatty acid compo- sition, by modulating both rumen and mammary lipid metabo- lism. Hence, the aim of the present study was to evaluate milk fatty acid (FA) composition as a marker of the feeding regimen in dairy cow. Individual milk samples of 319 cows were collected from 24 commercial dairy herds (13±4 cows per farm). The ani- mals were selected so as to have individuals homogeneously dis- tributed along the entire period of lactation. Using a standard questionnaire, management and nutritional parameters were recorded. On the basis of questionnaire results, farms were grouped into 4 different feeding regimens: group1 (low level of forage and fat integration), group2 (medium level of forage and fat integration), group3 (high level of forage and fat integra- tion), group4 (high level of forage and no fat integration). Methyl esters of FA were prepared by a direct extraction and alka- li catalyzed transmethylation procedure, followed by gas-chro- matographic analysis. A reference standard butter was used to estimate correction factors for short-chain FA. Data were ana- lyzed by principal component analysis (PCA) to determine how the feeding regimen of the dairy cows and the composition of the milk were differentiated from each other. Data were analyzed by the GLM, with farm, days in milking, season of calving and diet group as main effects. Significance was declared at P<0.05. The mean value for the different variables was an average of all milk samples and was used directly in the PCA plot. In the present study, production data collected from 24 farms showed a large variation in feed intake between and within the 4 feeding regi- mens. The first (PC1) and second (PC2) principal component explained 28% and 12% of variation, respectively. The results showed that the different feeding regimens adopted by farmers, were significantly discriminated according to milk FA composi- tion. In particular, the low level of forage is associated with a higher content of n-6 fatty acids and a high level of n-6/n-3 ratio. Fat integration is related to increasing amount of vaccenic acid and CLA (+25%).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
