Objective 2. Can pedometers predict estrus in tie-stall dairy cows?
The following figures depict progesterone concentrations (P4) and cow activity (steps, lying bouts, and lying times). Estrus was induced by prostaglandin F2 (PGF) on day 0, an increase in steps and lying bouts and a decrease in lying time was expected 72 hours after treatment (days 2-4). To determine differences paired t-tests were preformed using before treatment and after treatment for P4, steps, lying time, and lying bouts.
Figure 1.
Figure 1 displays average progesterone (P4) concentrations over the 3 day blood sampling period. This graph displays that cows responded to PGF, which is displayed by a significant decline in P4 from the first sample (right before PGF) to the last. This allows us to predict an expected period of increased activity (estrus) between days 2-4. A paired t-test was preformed to determine if there was a significant difference from day 0 (before injection) to after day 0 (P < 0.0001).
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Figure 2.
Figure 2. Is the average absolute and relative steps before and after PGF treatment. There was a decrease in the absolute steps after treatment. This does not support the second hypothesis, which states that steps would increase after treatment of PGF; however, the differences were not statistically significant (P = 0.61). Relative steps had a small increase with a smaller standard error compared to the absolute values, therefore suggesting that certain cows, relative to the before, steps slightly increased.
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Figure 3.
Figure 3. Average absolute and relative lying times before and after PGF treatment. There was a small numerical increase in lying times after PGF treatment, however differences were not significant (P = 0.86). A decrease in lying time was expected after PGF treatment because cows are normally more active during estrus, therefore they would lay less per day.
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Figure 4.
Figure 4. Average absolute and relative lying bouts before and after PGF treatment. There was an significant increase (P = 0.001) in lying bouts after treatment. This supports one part of the second hypothesis, which states that lying bouts would increase after treatment of PGF. This therefore concludes that cows have increased lying bout activity during the predicted estrus period.
Figure 5.
Figure 5 displays the average steps per day. Day 0 was the day of PGF treatment. An increase in stepping was expected throughout days 2-4, however this graph depicts a decline in stepping activity. Before and after paired t-tests were preformed and found no significant differences (P = 0.61).
Figure 6.
Figure 6 displays the average lying times per day. PGF was given on day 0; a decrease in lying time was expected throughout days 2-4, however this graph show an increase in lying time. No significant differences were found comparing before and after data in a paired t-test (P = 0.86).
Figure 7.
Figure 7 displays average lying bouts per day. PGF was given on day 0; an increase in lying bouts was expected throughout days 2-4. This graph shows a significant increase in lying bouts throughout the expected estrus period. A paired t-test was used to determine differences of before and after PGF (P = 0.0006). There was a significant increase in lying bouts, however the difference was only 1-2 bouts higher, which is not a large enough increase to conclude that the cows were more active.
Progesterone concentration and activity changes throughout the 9 day sampling period
Figure 8, graph 1 displays the concentration decline in P4 after the PGF injection (day 0). This therefore allows a predicted time for expected increases in activity (steps and lying bouts) and a predicted decrease in lying time between days 2-4 (estrus). However, steps (graph 2) and lying times (graph 3) did not significantly change throughout the sampling period. Lying bouts (graph 4) did significantly increase after the PGF injection, which supports one part of the second hypothesis; however, the difference was only 1-2 lying bouts greater during estrus.
Conclusion
Pedometers were validated against video records to determine the accuracy of activity monitoring in tie-stalls. The study found that the pedometers can accurately monitor cow activity (lying time + lying bouts) in a tie-stall barn. Cows were monitored 24 hours per day for 9 days; activity (steps, lying times, and lying bouts) before treatment was compared to activity after treatment (expected estrus period). Cows had insignificant changes in stepping and lying time activity throughout the trial. Cows had a significant increase in lying bout activity during the expected estrus period, however the increase was only 1-2 lying bouts higher. The increase in lying bout activity is not large enough to conclude that cows were more active during estrus. Therefore, because overall cow activity during estrus did not significantly increase, pedometers are not useful in the detection of estrus in cows housed in tie-stalls 24 hours per day.
Due to facility restrictions, the current project could not follow commercial farming practices. On a commercial tie-stall dairy farm cows are placed outside for approximately 2 hours per day. Research is required to determine if pedometers could detect estrus in cows housed in tie-stalls for 22 hours per day.
Due to facility restrictions, the current project could not follow commercial farming practices. On a commercial tie-stall dairy farm cows are placed outside for approximately 2 hours per day. Research is required to determine if pedometers could detect estrus in cows housed in tie-stalls for 22 hours per day.