Andrea Cupp – Attainment and Maintenance of Pubertal Cyclicity May Predict High A4 cows with Reduced Fertility.
By: Dr. Emily Taylor
Dr. Cupp began her discussion by briefly describing the overall goals of a cow-calf producer – heifer development and rebreeding of cows at a low cost. However, one challenge that producers have in meeting these goals, is cattle that are anovulatory. This means that for some reason, heifers and cows are not ovulating oocytes, causing a decrease in overall conception rates and subsequent calving rates. It has been observed that a large population of cows are secreting large amounts of androstenedione (A4). These cattle are having irregular cycles, often are anovulatory and less fertile, similar to women with Polycystic Ovary Syndrome. Although these females have lower calving rates, they also are weaning heavier calves. Unfortunately, it seems that we are selecting for these high A4 females, due to the larger calves at weaning.
Data was presented showing that heifers, identified as high A4 females, reached puberty 45d earlier than cows identified as normal A4 females. Therefore, it was hypothesized that heifers reaching puberty earlier were predisposed to become high A4 cows. Dr. Cupp suggests that we try and identify these females earlier, and then they can be culled from the herd. She specifically discussed a study where heifers were grouped by pre-pubertal characteristics. Heifers, who began to cycle and stopped or were considered non-cycling had greater secretions of A4, irregular cycles and a reduction of calving in the first 21 days. Therefore, it was suggested that these females may be predisposed to becoming high A4 cows with decreased fertility.