Activity Monitors to Improve Reproduction
Activity monitors offer the opportunity for medium to large-sized dairy herds to improve heat detection and, at the same time, reduce dependence upon labour. An activity monitor is a motion-detecting and recording device, one of several precision dairy management tools that are providing opportunities to save labour and improve individual cow care and management through the use of technology.
Heat detection rate is a key factor in determining pregnancy rate and reproductive success in a dairy herd. This area has the most opportunity for improvement in dairy herds. Heat detection efficiency in dairy herds is less than 50%, and failure to accurately detect estrus costs the dairy industry millions of dollars each year.
Dairy cow breeders can choose one of three management systems:
In high-producing cows, the period of mounting activity lasts an average of 5.8 hours, and some cows only stand to be mounted once to twice per heat cycle. Accurate heat detection requires observation of the herd by a trained individual three to four times a day, seven days a week. The biggest challenge to systematic heat detection is to be able to carry out observations consistently, when required, every day.
Synchronization protocols and timed AI, on the other extreme, offer excellent control and timing of breeding, as well as the opportunity to schedule workload, and address the 20% of cows that are anestrus in early lactation. The downside is cost, the need to maintain strict protocols and the reliance on hormone treatments.
Figure 1: Activity monitors may be neck or leg-mounted.
How Activity Monitors Work
Many activity monitors are mounted by a strap around a cow's lower leg to detect and record motion such as walking. These are often called pedometers. Other types of activity monitors are attached around a cow's neck (Figure 1). The data in the monitors on each cow are accessed automatically by a reader device and relayed to the computer.
Software creates reports on the activity of each cow over previous time periods. Cows show increased activity prior to the onset of standing heat by a factor of two to four times normal. Cows should be considered for breeding within 12-24 hours of being identified with increased activity by the pedometer system.
Pedometers and activity monitors provide the opportunity to identify cows coming into estrus while reducing the dependency upon labour. Studies have shown 80%-85% heat detection rates with pedometers when one animal is in heat and up to 90% when two or more are in heat.
Figure 2: Sample read-out of an activity monitor, showing spikes in activity associated with heat cycles, compared to days in milk.
Prices vary, depending upon features of the system, number of readers and number of activity tags. Initial investment in a pedometer or activity monitoring system can be significant. The cost for a system for 100 cows can run between $12,000 and $30,000.
The initial capital cost can be justified in improved heat detection and labour savings. With arm's-length farm labour costs of $13-$18/hr, an observational heat detection program costs about $6,000 per year. At 6.5% interest over 7 years, a $30,000 investment in an activity monitor system would break even in labour replacement costs alone. Investing in a $12,000 standalone monitoring system would make sense if labour on the farm is valued at $8/hr or higher.
Typically, activity monitors attain better heat detection rates than strictly observational methods, which would be further justification over savings in labour costs. Figure 2 reproduces a read-out for a normally cycling cow, showing how the cow's activity levels spike with heat cycles, compared to her days in milk. The line showing daily activity is a result of readings from the neck or leg-mounted activity monitor. In this case, the cow would be a candidate for breeding 12-18 hours later. If the cow has been bred and becomes pregnant, there are no further sharp peaks in activity. If the cow had either not been bred or had been bred and not conceived, one would expect another peak in activity to occur approximately 21 days after the last peak.
When compared to a synchronization program, strictly on a cost-per-cow basis, the activity monitor program tends to be much cheaper and also has some economies of scale, which is not the case with synchronization protocols.
Other benefits of an activity monitor system include the tracking of activity over a number of days and its integration with other production information on each cow to assist in management decisions. Sudden decreases in activity may indicate the onset of lameness or other illness. Other patterns of activity, such as increases followed by decreases, may be related to metabolic disorders.
Activity monitors provide an alternative for heat detection in freestall-housed dairy herds, especially as a replacement to labour with as good, and frequently better, heat detection rates than a traditional visual heat detection system.
Activity monitoring systems tend to be integrated with milking parlour data systems, although some are standalone systems. Activity monitoring systems have a higher capital cost but are a reasonable economic alternative to visual heat detection with its costly labour component, or a synchronization-based program with less reliance on injections and high associated costs per cow.
Activity monitoring systems and related software provide valuable management information, along with other production data, for managing the dairy herd.
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