We found that: a) lactation stage must be defined biochemically (such as Na: K ratio), not by day of lactation, b) lactation stage influences RNA quality, quantity, and potential
immune cell contamination, c) immediate processing and hard, fast centrifugation
yield better quality RNA, and d) additional washing of the milk fat layer is not necessary for the analysis of mature milk samples and does not decrease
immune cell contamination in colostrum samples.