8:30 am - 9:30 am
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Mohsen Hashemiranjbar Sharifabad. This seminar is open to the general public to attend.
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Meeting ID: 679 837 2640
Thesis Topic: Elucidating biological aspects of feed efficiency in dairy cows using metabolomics
MSc with Dr. Graham Plastow.
Seminar Abstract: Feed represents more than half of the costs of livestock production. Residual feed intake (RFI) is a phenotypic measure that has been proposed as the best approach for genetic improvement of feed efficiency in dairy cows. The high cost of recording individual feed intake and production traits such as milk yield, body weight and milk composition traits has been the main reason for a slow rate of application. The overall objectives of this study were: 1) identification of differences in metabolism of high and low RFI cows at early, mid, and late lactation stages and 2) assessment of the potential of metabolites as biomarkers for prediction of feed efficiency in lactating cows.
For RFI estimation feed intake and milk yield data were recorded on 75 lactating cows on a daily basis, the concentrations of milk fat, protein and lactose were measured weekly and animals were weighed monthly. Random regression and multiple linear regression were used to adjust actual energy intake for maintenance and production requirements. Average values of RFI were obtained for each individual for day 3-240 of lactation and cows were grouped as high RFI (or least efficient, > +0.5 SD) and low RFI (or most efficient, < -0.5 SD).
Nuclear magnetic resonance (NMR) was used to quantify serum samples collected from high (n = 20) and low RFI (n = 20) cows at 50, 150 and 240 days in milk (DIM). The univariate analysis showed that the serum concentration of 4 (glycerol, urea, creatinine, dimethyl sulfone), 4 (creatinine, glycerol, L-ornithine, L-lysine ) and 8 (glycerol, acetone, citric acid, 3-hydroxy butyric acid, choline, creatinine, glycine, formate) metabolites were significantly different (P<0.05) between high and low RFI groups. The concentration of glycerol and creatinine were consistently increased in low RFI cows at all the three time points during the lactation period. The multivariate analyses (principal component analysis, partial least squares discriminant analysis, receiver operating characteristic (ROC) curve and variable importance in the projection) were used to identify metabolites with the most discriminatory power between high and low RFI groups. A set of metabolites differentiated low and high RFI cows at each of the three time points. The area under the ROC curve with values of 0.936, 0.866, and 0.997 for 50, 150, and 240 DIM respectively, indicated that those metabolites have a very high sensitivity and specificity to be used as biomarkers of RFI. Multiple linear regression analysis showed that individual RFI values can be predicted from serum metabolite profiles with adjusted R-squared of 0.62, 0.65, and 0.83 at early, mid, and late lactation stages, respectively. This study provided evidence to support the potential use of serum metabolites as biomarkers of RFI for both classifications into high or low RFI groups and prediction of the efficiency of individual cows, however, further investigation is warranted for validation of the results.