The more I read, the more I’m extremely grateful for the rigor that my reproduction class required. None of this would have made sense to me last year, and it’s amazing how many of the details I’ve been able to keep in my conscious memory. I’m sad that I’m missing the advanced repro course offered in the fall, but hopefully the experience I’m gaining here will be just as valuable, and I can continue applying what I’ve learned so that I don’t lose the knowledge.
I was extremely impressed with this article. It felt like a lecture rather than a textbook, and as a reader it was easy to finish, but still full of great content. The focus is on how while our dairy cows have been engineered to crank out milk, we’ve seen a dramatic drop in their reproductive success which hurts the efficiency of dairy operations.
The article explains that rather than a minimalist approach that looks at only one factor (such as inadvertent selection for poor reproductive fitness) to correct the problem, a more inclusive or holistic approach is needed. I learned a lot more about common problems such as lameness, mastitis, metritis, and poor BCS and how they relate specifically to resumption of estrus after parturition and zygote viability. I’m always amazed how farmers can actually succeed at maintaining herd numbers when conception and birth rates are so low.
There was a lot written about heat stress, and that always seems obvious when it gets over any comfortable temperature. But heat and other environmental stressors are actually a lot more dangerous to reproductive health than I was aware. According to the article, “exposure of ovarian oocytes to unfavorable physiological events during follicle development from primadorial to pre-ovulatory stage may result in the ovulation of defective oocytes up to three months after the insult (Britt, 1992; Fair, 2010).” When you have 60-90 days to breed your cattle to stay on schedule, this is extremely influential to your breeding program. This also makes the situation down in Texas more dangerous in that, with the dry weather during their normal wet season, any excess stress surrounding parturition could delay or destroy what’s left of their breeding program. Once they can’t even breed replacement heifers, its all over.
So, after looking at multiple conditions that hurt reproductive efficiency and discussing their prevention. The article sums itself up with a nice poster identifying the key areas they covered.
For the causes and preventative measures covering these you can check out the article. It finishes up by making the point that we can’t just develop a new antibiotic for metritis or mastitis, but we need to reevaluate our genetic selection and more importantly, our management strategies to ensure as many of these factors are met as possible.
Walsh SW, Williams EJ, & Evans AC (2011). A review of the causes of poor fertility in high milk producing dairy cows. Animal reproduction science, 123 (3-4), 127-38 PMID: 21255947
