What is the buzz around cow longevity?

Dairy cattle longevity has been a topic of increased interest in recent years.

Cow longevity is important to the economics of a dairy farm. With a longer productive cow life, a farm could be potentially more profitable and have a reduced environmental footprint.

One issue facing the dairy industry is the length of time cows remain in the herd. The current average number of lactations for a dairy cow is 2.8. This means that dairy cows are in the herd for about 60 months or a little over 5 years, assuming age at first calving is 24 months and the calving interval is 13 months.

Farms with cows that remain productive longer will need fewer replacement cows and fewer overall animals, meaning less feed and less manure and therefore creating a smaller environmental footprint. If a cow stays in the herd longer, it can be assumed that it has had fewer health issues leading to a longer productive life and better animal welfare. There is also increased general public interest in a cow’s lifespan since a short productive life can give the impression that there may be a reduction in animal welfare. The natural lifespan of a cow can be around 20 years, and with the awareness of a cow’s shorter life, the public has welfare concerns about the longevity of dairy cows.

Cows do not reach full maturity until their fifth lactation, which is when they will reach their full potential producing the most milk. Many cows leave the herd before even completing their third lactation and are not hitting genetic potential, yet dairy farmers work very hard to have good genetics in their herds. There has been a trend for the movement toward younger herds for a few reasons, including reproductive efficiency.

The improvement in reproductive management and techniques in the last years resulted in higher reproductive efficiency at the dairies, which associated to increased popularity of sexed semen, leads to a surplus of replacement heifers. However, this heifer surplus can lead to early culling of productive cows. The young animals are usually genetically superior to their older herd mates, however, if only a few cows are reaching their maturity and genetic potential, it does not matter how good heifer genetics are.

Many dairy farmers would like to know the ideal number of average lactations for a dairy cow to be in a milking herd. To answer this question, Dr. Albert De Vries created a model making assumptions and uses estimated prices that showed the ideal herd average number of lactations is five. It also showed that keeping an animal for six lactations costs the farm an extra $3 per year and keeping an animal for four lactations costs the farm an extra $20 per year. A good recommendation is to try and have an average herd lactation between four and six.

To improve herd longevity on dairy farms, producers need to understand why cows are leaving the herd. Careful cull cow records need to be maintained and reviewed often to determine why cows leave the herd. Once these reasons are identified, the appropriate changes can be made. According to 2018 USDA data, the three most common reasons cows are reported to be culled from a herd are infertility, mastitis, and lameness.

Genetics and herd inventory can improve cow longevity and health

One tool dairy farmers can use is genetic selection. Once the reasons for culling are identified, a breeding and genetic program can help dairy farmers on improve their herd longevity. There are several health traits indexes that combine direct and indirect measures of longevity that can be selected for in a breeding program aiming to improve longevity. Traits that can be selected for are better udders, metabolic health, feet, and legs. Artificial Insemination (AI) consultants can help with these choices based on reasons for culling.

A surplus of replacement heifers can increase culling rates and reduce cow longevity in the herd. It happens in herds that are not expanding and raise and incorporate all calving heifers forcing older but healthy and productive cows to leave the herd. Farms should have breeding strategies to make sure that they have only slightly more heifers than needed based on their culling rate goal. Farms tend to want to keep the heifers and cull an older cow instead of culling heifers. This is because heifers often have higher genetic merit when compared the older cows.

Herd inventory management is key to improved farm finances. According to a 2020 study by Overton and Dhuyvetter, it costs anywhere from $1,700 and $2,400 to raise a heifer. It is often the third highest cost on a farm behind labor and feed. When a farm raises too many heifers, there is a monetary loss from selling the heifer at the market price of about $1,300. In the United States, on average, it is two full lactations until a heifer has paid off her investment and is profitable. With most cows being culled in the third lactation, it leaves very little time for them to earn money for the farm. Michigan State University Extension recommends breeding for 10% surplus heifers or 10% over your culling rate, however, this number will depend on a farm’s risk tolerance. The surplus of heifers can be sold at market value. Because the higher cost of raising heifers, the younger a surplus heifer is sold, the smaller the financial loss the farm will experience.

First lactation animals produce 80-85% of the milk that a cow in her third or greater lactation can produce. A young herd will decrease overall milk production for that farm simply because of its ability to make milk. One easy way to increase herd average milk production is to decrease the percentage of first lactation animals in that herd. Today, many dairy farmers tend to have a younger herd age. Some farms even have 50% first lactation animals. If this trend in a herd continues, most of the cows will not reach peak lifetime milk production. The current industry recommendations are a herd make-up should be about 30% first lactation, 30% second, and 40% third plus lactations.

Lowering stocking density to Improve cow longevity and health

Improving overall herd health will result in heathier cows on their third and future lactations and will increase their longevity in the herd. To improve cow health, it is important to first evaluate the environment and facilities the cow is living in, such as bunk space, stalls and bed quality, heat abatement strategies, hygiene.

Overstocking can play an influential role in the decreased health of a mature cow and impact herd longevity. Overstocking impacts bunk space which will reduce the number of meals per day and the ability for every cow to get adequate nutrition. If there are not enough stalls or bunk space, cows will spend more unproductive time on their feet. This increased time standing can result in increased lameness in a herd and can decrease milk production. Also, with higher stocking densities, heat abetment is challenging, cows under heat stress will spend more time standing or perching trying to lower their body temperature, which can lead to increased lameness. Heat-stressed cows are also more vulnerable to other health issues and, therefore, a higher risk of leaving the herd. With higher stocking densities, there is also more manure accumulation leading to more environmental mastitis problems. Also, with high stocking densities, cows will choose rest over food and lay down before eating after milking, making them more vulnerable to mastitis. Overstocking barns with a surplus of heifers is tempting so both younger and mature cows can stay. However, overstocking barns can lead to a substantial impact on cow health and longevity increasing the risk of cows being culled by health issues or low milk production.

MSU Extension recommends that dairy farms work with a team of advisors to help them set herd inventory goals and reduce involuntary culling. The first step is to evaluate a dairy farm’s records and set goals for improvement.

Check out the MSU Extension Dairy Team Virtual Coffee Break Podcast for the podcast on this topic at https://anchor.fm/msu-dairy-team

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