The transition period, the most challenging time for dairy cows and heifers, has been historically defined as the three weeks before to the three weeks after calving. However, new discoveries in cow physiology are suggesting that this period should be extended to include the time from dry-off and on. Regardless of what definition is used, during this time, cows and heifers experience a number of physiological adaptations that predispose them to become sick and underperform. Nevertheless, not all the animals become sick or underperform, so what is the difference between these groups? And can we identify these animals without doing expensive, delayed laboratory testing?
There are a number of cow parameters that are recorded daily on the farm at different times during the transition period and even before, such as milk yield and body condition score. These records are used to assess farm profits and as benchmarks to ensure that management is optimal, but what if we could get more out of them? Some cow parameters, such as lactation number, are always recorded at the farm and have long been known to be associated with common performance metrics such as milk yield and reproductive performance. Parity, the dichotomization of lactation number in primiparous (first calf cows) and multiparous cows (second or greater lactation), is perhaps the cow feature that has the most data supporting associations with disease risk, production, and fertility.
There are a number of research studies that have shown that primiparous cows are physiologically different than multiparous cows, but interesting that at times primiparous cows may be high-risk animals, at other times multiparous cows may be the ones we need to focus on. For instance, in a study we published in 2020, we reported that primiparous cows had higher markers of inflammation, stress, and pain in the first week after calving. In contrast, when looking during early prepartum period and at dry-off, research suggests that multiparous cows had higher inflammation and metabolic stress. However, these are very broad groups of animals accounting for around 60-70% of the herd when referring to multiparous cows and 30-40% in the case of primiparous cows. Therefore, the focus should be on identifying the subgroups of animals within these larger groups that are more susceptible to succumbing to the transition period challenges. In order to do this, we created the Target Cow concept.
This concept is being developed to manage high-risk animals selectively and proactively at times of stress and step away from blanket therapies that were once recommended, where the whole herd needed to be treated or supplemented with a specific product. By differentiating cows that will perform from cows that will underperform early on through cow parameters commonly recorded on the farm, practitioners can selectively manage these cows to avoid future losses. This strategy will not only decrease costs associated with poor health and low productivity in this group of animals, but it will also decrease costs related to unnecessary herd-level interventions, such as feed supplementation.
Source : psu.edu