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 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 been long 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 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 while 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% to 70% of the herd when referring to multiparous cows and 30% to 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 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.
The research in this area is suggesting that there are not only cow features associated with higher chances of underperforming, but also, there are times during the transition period and before that would determine the risk level for each group of animals. There are three main periods we are researching in the lab based on applicability and alignment with farm management and logistics, which are the time of dry-off, the time to move cows from the far-off to the close-up pen and the time around calving. Let’s start from the beginning and describe the Target Cow at dry-off. There is not much research on this area regarding cow physiology. One study reported that cows producing more than 30 pounds of milk at dry-off had higher inflammation and lower immunity several weeks after dry-off. A more recent study reported that cows with high somatic cell counts at dry-off had lower colostrum quality, and calves born to these cows had lower immune passive transfer.
In an ongoing trial, we have identified a few Target Cow features at this time. Body condition scoring is becoming a popular practice in dairy farms as new technologies such as automatic body condition scoring cameras are becoming available. In addition, a large percentage of cows are usually overconditioned by the beginning of the dry period. In our dataset, not surprisingly, overconditioned cows at dry-off had higher metabolic stress markers right after drying off and during the transition period. However, what was most interesting from our results was that overconditioned cows at dry-off produced 5 pounds per day less milk for the first 112 days after calving and had 10% more recorded health events in the first 60 days in the subsequent lactation compared to optimally conditioned cows. Another cow record that nowadays is commonly recorded on a daily basis in dairies is milk yield. We looked at milk yield the day before dry-off (to have a complete day of milk yield) and found that cows with low milk yield (i.e., less than 50.5 pounds per day) at this time were at higher risk of underperforming. This group of cows had higher NEFA concentrations the first 5 days after dry-off and produced 11.5 pounds per day less milk for the first 16 weeks of lactation than their counterparts. Remarkably, when we looked at postpartum health, dry-off low-milk-producing cows had 21% more recorded health events compared to dry-off high-milk-producing cows. Similarly, somatic cell count (SCC) is another cow record frequently recorded in dairy farms. Our preliminary results suggest that high-SCC cows at dry-off had higher metabolic stress the first week after dry-off and the week before calving and produced 9 pounds per day less milk during the first 16 weeks (1,000 pounds of milk per cow) in the subsequent lactation compared to low-SCC cows at dry-off.
After dry-off, the next period we are interested in is the time of moving cows to the close-up pens (21 to 14 days before expected calving date). The main parameters we have found to be associated with higher inflammation at this time are overconditioning and stillbirth. Unfortunately, it’s hard to know at this time which cow will have a stillborn calf to do any preventative intervention; however, monitoring and preventative interventions should be considered for overconditioned cows, especially primiparous overconditioned cows. This claim is supported by a study we published last year, where we reported that anti-inflammatory strategies at this time benefit health and milk yield on primiparous and overconditioned cows. Finally, during time around calving, research has shown that cows that are in their third lactation or greater, had a twin pregnancy, had a stillborn calf or had dystocia are still the main groups of animals to focus on preventative interventions. There are a number of studies that have found that these groups of animals have higher inflammation, higher metabolic stress and are at a higher risk of becoming sick, have low milk yield and fail to get pregnant in a timely manner.
So as a summary, our Target Cow groups so far are: 1) at dry-off: overconditioned (3.75 points of BCS or greater), low milk yield (less than 50 pounds) and high somatic cell count (greater than 200,000 cells per milliliter) cows; 2) at the time to move cows to the close-up pen: primiparous overconditioned cows; and 3) at calving: third-lactation-plus, twin pregnancy, stillbirth and dystocia cows.
The next question would be what management could be recommended for these cows. To answer this question, we first need to understand what is causing cows to underperform in each Target Cow group at each of the times described above. Is it metabolic stress? Is it inflammation? Is it something else? Or is it all of the above? We are doing trials focused on addressing inflammation, mineral disbalances and metabolic stress, individually and in combination – and although this is a lengthy process, at the end of these research efforts, we will be able to identify best preventative management practices for Target Cow groups at these strategic times, and avoid underperforming of these susceptible groups of animals, maximizing farm profitability and animal welfare.
