Genetic considerations for organic dairy herds
by Hannah Majewski
For any dairy farmer, genetics are always a consideration when trying to improve herd health, productivity and longevity. In an organic dairy herd, genetics become an even larger priority when taking into account the rules of organic farming. Dr. Glenda Periera, University of Maine professor of food and agriculture and Extension dairy specialist, homed in on this topic in a recent webinar. The session was part of a series hosted by New England land grant universities and their researchers.
A criterion for all organic producers is that their herd has access to pasture for the majority of the year (the exact timeframe depends on the growing season of the area). This leads producers to select traits in their herd for what Periera refers to as the “ideal grazing cow.” The number one most important trait is fertility, which also applies to conventional herds. If a cow is unable to reproduce and continue lactation cycles, then she becomes valueless to a farmer. Additionally, in organic herds, producers are not allowed to use synthetic hormones to manipulate ovulation cycles – therefore natural cycles are all the more important.
Other traits in the ideal grazing cow include high butterfat and protein components in their milk and low somatic cell counts. Once again, organic dairy farmers have an additional hurdle of not being able to treat infections with antibiotics, so having a cow maintain low SCC reduces the risk of infection and the need to treat a disease. Lastly, in a grazing cow, a smaller framed and functional cow is more desirable so that it can keep up with the lifestyle of living outside and continue its ability to convert grass to milk as opposed to using concentrates as the main feedstuff.
Artificial insemination was a popular topic throughout this webinar. Farmers and producers of this era are fortunate to be able to use this as a breeding tool. Most commonly, AI is thought to be a safer and more cost-effective breeding tool on the farm because caring for a herd bull is no longer necessary. Periera focused on the genetic advantages a farmer can have by utilizing AI. A farmer can select a bull for specific traits to focus on improving a certain part of their herd. Registered bulls all have statistics associated with them for their predicted transmitting abilities (PTA). For example, if an organic dairy farmer is struggling with their cows having functional feet and legs to walk out to pasture, a bull can be selected for its PTA of leg structure. These PTAs can then be applied to a merit index to show a farmer the value in selecting a bull with these improved traits in their herd. More specifically, there is even a grazing merit index, which attributes values to all the “ideal grazing cow” components.
While thinking about modern dairy cows, it’s interesting to compare the genetic progress. This can be most easily observed in the Holstein breed because of their popularity. It is clearly seen that farmers have selected Holsteins for higher milk production and stature. In the 1970s, one Holstein cow on average made about 9,751 pounds of milk in one lactation. Today, Holsteins make upwards of 23,777 pounds of milk. Researchers attribute this to the net merit increases in feed efficiency and heifer viability. One can argue whether or not these have been the best genetic selections for the cow and the dairy industry in general, but it proves how powerful a tool AI has become for any farmer.
Besides using tools like AI, there are other methods to introduce genetic diversity into a herd, including crossbreeding. This is not especially common in the dairy world as many producers like to register their cattle as full bred (there are no opportunities to register crossbred dairy cattle). Crossbreeding includes several benefits, the largest being the ability to maximize genetic advantages from multiple breeds of cattle. To receive the most benefits from doing this, a farmer should select bulls that have been proven in AI companies that specifically can improve their herd.
Periera’s presentation noted that a combination of three breeds is optimal. Two breeds would limit the benefits of heterosis (or crossbreeding), and four breeds would limit the influence of each individual breed on the offspring. An example would be crossbreeding a Holstein, a Jersey and a Brown Swiss. The Holstein has an advantage in production volume; the Jersey, an advantage in butterfat components; and the Brown Swiss could then be selected to improve an additional aspect such as feed and leg structure. This process would be done through generations of breeding. Some of the benefits besides production include increased fertility, health and survival by up to 10%, according to Periera.
The world of genetics is constantly evolving and there are several areas that are still developing. One sector still being researched in dairy cattle is the genetics of fly resistance. Once again, organic farmers have more stringent parameters around how they can combat fly pressure. Organic farmers need to rely on their manure management, fly traps and natural repellents to control fly populations. Student researchers at the University of Maine found that horn flies prefer black to red cattle when given the option, showing there could be a genetic solution to combat fly pressure. Currently, there are genetic indications for fly control in beef cattle, but this is a new area of research for dairy farmers.
The biggest takeaways that Periera noted were that a farmer needs to consider their local market to make the best breeding decisions for their herd and make progress specific to the herd goals. Tools like AI and the genetic index can help make these decisions clearer. This is a constantly evolving field and producers should be excited about new potentials in genetic advancements.
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