Figure 5From: Milk yield responses to changes in milking frequency during early lactation are associated with coordinated and persistent changes in mammary gene expressionTemporal pattern of differential gene expression is associated with changes in milk yield. Cows were assigned to unilateral frequent milking (UFM; twice daily milking (2×) of the left udder half, four times daily milking (4×) of the right udder half) during d 1 to 21 of lactation. Mammary biopsies were obtained from both udder halves on d 21, 23, and 40 of lactation. Gene expression was detected using Affymetrix GeneChip® Bovine Genome Arrays. Genes of which differential expression changed over time were grouped into 4 clusters based on the temporal pattern of differential expression. Cluster 1 (panel A; 61genes) included genes whose expression in 4× vs 2× udder halves was lower on day 21, higher on day 23 (after cessation of 4× milking), and subsequently lower on day 40 of lactation. Cluster 2 (panel B; 3 genes) included genes whose expression in 4× vs. 2× udder halves was lower on day 21, higher on day 23, and remained higher on day 40 of lactation. Cluster 3 (panel C; 8 genes) included genes whose expression in 4× vs. 2× udder halves was higher on day 21, lower on day 23, and higher on day 40. Finally, cluster 4 (panel D; 3 genes) included genes whose expression in 4× vs. 2× udder halves was higher on day 21, lower on day 23, and remained lower on day 40. Differential milk yield is plotted on the left Y-axis and differential expression of genes in each cluster is plotted on the right Y-axis. Gene expression data are presented as signed fold change (4× minus 2×) for each gene. Solid vertical line represents cessation of UFM and return of all 4 glands to 2× milking on day 21 of lactation.Back to article page