Just a short one here today. Not too much interesting going on in a study that supports the null, but the methods are great.
This study looked at the affect that one or two rectal palpations to determine pregnancy had on embryo viability. I can see why there would be a question, it seems like a highly invasive procedure when you’re shoulder deep in cow rectum and feeling for an amnion several layers of membranes away. But we tend to anthropomorphize, and many dairy cattle require minimal restraint for the procedure. Nonetheless, it does seem likely that there could be a negative effect on the embryo, especially when rupturing or crushing the amnion via rectal palpation has been a historical method of terminating an unwanted pregnancy in cows (before we started using PGF2α) (Romano, 2011).
The study did a great job of identifying factors that have created conflicting results in the past. Whether that was sampling bias, uncontrolled treatments (multiple people and techniques for palpation), or a lack of a true control. They took the time to show how each one of those shortcomings was corrected in this study, and I think they did a great job designing the experiment.
In the end it was surprising to see that there was no difference between the cows subjected to rectal palpation once or twice compared to the control. I didn’t expect to see a significant difference, but potentially a small one. The authors did warn that because this experiment was so controlled, the results may not be similar to every situation. Inexperienced personnel or different techniques could change the pregnancy rates in practice (the study employed a single veterinarian with >25 years experience). One difference they took time to note was the much lower pregnancy rate in dairy cows as opposed to primiparous heifers. The exact etiology of this is unknown, but is commonly found in dairy. The authors mention it as it played a role in their analysis of the two farms involved (other factors affecting rates between the farms were geographic area, rate of twinning, and breed of cattle).
Not especially exciting, but it’s always great seeing researchers identify a conflicted area and tackle it with strict methods/controls and a large sample size.
Romano JE, Thompson JA, Kraemer DC, Westhusin ME, Tomaszweski MA, & Forrest DW (2011). Effects of early pregnancy diagnosis by palpation per rectum on pregnancy loss in dairy cattle. Journal of the American Veterinary Medical Association, 239 (5), 668-73 PMID: 21879969