Cull cow welfare is important to the dairy industry's reputation
Herd longevity is determined by overall culling rate in a dairy herd. Cull cow welfare is important to the dairy industry, especially when cows show up to sale barns and abattoirs unfit for sale or slaughter. CanWest DHI Ontario Progress Report dating back to 2006 offers a bird's eye view of culling trends and reasons for culling a cow.
What the trends show
From 2006 to 2014, the trends remain relatively the same in terms of reasons for disposal compared with the trend of culling from month to month. Total cows culled from herds in 2014 were a little more than 55,000 cows, which have not changed much from 2010. Of those cows that were culled from dairy herds in 2014:
These rounded out the top five reasons for disposal as shown in Figure 1 (DHI Ontario Progress Report, 2014). More cows are culled in the late fall and early winter months as shown in Figure 2. The graph shows this trend has not changed much throughout the years. However, these trends mean more cows are at the sale barns and abattoirs throughout these months, increasing the likelihood of compromised animals.
Figure 1. Disposal Reasons for 2014 as recorded through CanWest DHI and reported in DHI Ontario Progress Report.
Figure 2. The number of cattle disposed of from the herd from January 2006 to December 2014.
Recent advances in genetic indexes focused on these traits could contribute to longer lasting cows in your herd and herd profitability. Knowing the risk periods when cows are most likely to be culled is one way to assess your farm's risk. This assessment may help you adopt practices to minimize the number of cows that need to be culled and potentially increase your herd's longevity.
A recent paper by Heise, et al., 2015 looked at the genetic structure of longevity and how this structure changes over the lactation and life of a cow. It's not surprising to observe the late dry period and early lactation pose the greatest risk for cows to be culled as shown in Figure 3. There are many challenges through this period that can contribute to an increase risk for culling, including disease, poor production and mastitis. The risk of a cow being culled for these reasons declines after 150 days in milk.
Figure 3. Probability of survival and risk of culling for German Holstein as reported by Heise et al., 2015 for 1st, 2nd and 3rd lactation.
A cow's risk of being culled from the herd increases with number of parities. Primiparous cows have different reasons for being culled compared with multiparious cows. Also, primiparous cows are more likely to be culled due to poor milk production, milk temperament, and feet and leg problems. However, multiparious cows are more likely to be culled due to mastitis and high SCC, metabolic diseases, and feet and leg problems. The risk is the same for both multiparious cows and primiparous cows to be culled late in lactation for infertility, which rapidly increases the risk for culling after 200 days in milk.
Although the reason given for culling a cow is due to reproductive issues, there are many underlying causes that can contribute to infertility, including lameness and other diseases. Even though cows are listed as being culled due to reproductive issues, there may be other risk factors contributing to this problem.
This information shows the complexity behind developing a longevity trait for selection. Examining your records and determining the main reasons why cows are leaving your herd may help you develop a longevity plan for your herd. Reducing risks at the appropriate time can lead to vast improvements in your herd's lifetime profitability.
Marlene Paibomesai is a dairy specialist with the Ontario Ministry of Agriculture, Food, and Rural Affairs. Works Cited: Heise et al., 2015. J Dairy Science. 99:1253-1265.
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