SYMPOSIUM: MANAGING REPRODUCTION IN DAIRY HERDS
Influence of Estrus Detedion on Days Open in Dairy Herds H. L. BARR Department of Dairy Science The Ohio State University Columbus 43210
Abstract
Data from 10 herds on a herd reproductive status program supported estimates of lost reproduct;ve days per cow per year due to conception failure and missed heat as 23 and 10 days. The corresponding estimates from Ohio Dairy Herd Improvement were 14,7 and 40.3 days. The correlation within the 10 herds between days lost due to failure to conceive and total days open was .38 and between days lost due to missed heats and total days open .92. Introduction
It is a privilege to initiate this discussion on reproductive management. The situation that directed my interest arose from our inability to change substantially herd conception rates even when the full resources of the Department of Dairy Science and College of Veterinary Medicine were focused on certain Ohio herds. The North Carolina Herd Reproduction Status (HRS) (2) program was modified and used in several herds to monitor the situation and to obtain average performance as a guide for Extension teaching. The herds enrolled were on a veterinary herd health program, and the dairymen were asked to report the reproductive status of the cows following each routine veterinary visit. Initially 30 herds were enrolled. Many of the herdsmen became delinquent in their reporting, but 10 herds completed a year's information. Summary Data
While not a large sample, the summary of these 10 herds emphasized some important items. Table 1 presents herd conception rates in two ways. One is the ratio of total services to conceptions in 12 me, and the second is services required to impregnate the cows that settle in 12 me. Some services involved in the latter measure would have preceded the year of conception. Over an extended period the Received July 22, 1974.
total services per conception will be the greater figure, but for a single herd in 1 yr the services to cows conceiving may be greater. In the 10 Ohio herds the conception rates for all cows and. fertile cows were 2,3 and 2.1. Pelissier (3) had previously reported 2.55 and 2.02 services per conception for all cows and fertile cows in large California dairy herds. An early inspection of the HRS data revealed that days open for fertile cows were much more variable than could be attributed to variation in services per conception. Services per conception ranged from 1.7 to 2.8 and could account for no more than 23 days of lost time in reproduction, The range in total days open in these herds was from 84 to 136 days. This represents a range of 52 days. The computer was programmed to partition days open. The events counting for lost days were voluntary waiting by the herdsman, o n e half of a 21-day cycle as an average time lost after intended breeding, time for a new cycle following failure of conception, and missed heats. Days lost due to conception failure w a s calculated by determining services required beyond one and multiplying that number by the 21 days normally required for a cycle. All time not accounted for by the first three events was assigned to missed heats, whether missed by an anestrus cow or an unattentive herdsman. The formula for computing days lost due to missed heat periods was: Missed heats, days lost = Total days open -- Voluntary waiting -- One-half cycle -- [(Services/Conceptions --1) X 21]. Days lost due to missed heat periods include human error, anestrus, and embryonic loss. The partitioning of days lost in reproduction is in Table 2, The correlation between days lost due to failure to conceive and total days open was .38, and the correlation between days lost due to missed heats and total days open was .92. A recent report by Larson (1) indicated no difference in services per conception between cows with long and short ealving intervals. In Ohio D H I herds, which involved 76,610 cows, the recently reported services per conception were 1.7, and the average for days 246
247
SYMPOSIUM
TABLE 1. Conception rates and days open in ten Ohio herds. Herd no.
All services divided by conceptions
No. of conceptions
1 2 3 4 5 6 7 8 9 1O Total
39 30 50 38 263 36 112 22 74 12 683
1.8 1.6 2.8 2.0 2.2 1.7 2.8 2.6 2.9 4.0 Avg 2.3
open was 126. Allowing for 60 days voluntary waiting and partitioning the remainder of the time, it appears that Ohio dairymen are losing 14,7 days due to failure to conceive and 40.3 days due to missed heat periods. This compares with 23 and 10 days for herds on HRS. Expressed in another manner, dairymen on D H I are observing and using 1.7 heats per cow per year and missing 1.9 heats per cow. Approximately 53% of heats are being missed. Conclusion
As a result of the experience with HRS, the following points are emphasized with Ohio dairymen: 1) Herd conception rates are not extremely variable and our ability to influence substantially these rates is limited. 2) Dairymen appear to be losing twice as many days due to missed heat periods as due to failures to conceive.
Services per conception for fertile cows
Days open for fertile cows
1.8 2.2 2.2 2.3 1.9 1.7 2.8 2.0 2.2 1.7 2.1
100 101 131 136 91 98 103 124 112 84 103
3) Because the missed heat category contains days lost due to embryonic loss and anestrus, it is not expected that all anticipated heat periods will be observed. 4) It does appear reasonable, based on HRS herds, to reduce the current days lost of 40.3 (approximately two heats per cow per year) to less than 21 days. References
(1) Larson, L. L. 1974. High cost of low reproduction. Nebraska Dairy Report EC 74220:10. (2) Nicolai, J. H., Jr., and L. C. Ulberg. 1967, North Carolina's system of herd reproductive status. Paper presented at the 20th Annu. Convention Nat. Ass. Anita. Breeders, September 7. Hershey, PA. (3) Pelissier, C. L. 1970. Factors contributing to low breeding e~ciency in dairy herds. Mimeograph with paper E2 presented at tho Sixty-fifth ADSA Annual Meeting, Gainesville, FL.
TABLE 2. Accounting for lost reproductive days.
Herd 1 2 3 4 5 6 7 8 9 10
Voluntary waiting days 60 60 60 60 60 60 60 60 60 60
Avg days to first estrus 11 11 11 11 11 11 11 11 1I 11
Days lost failure to conceive 15.9 25.1 25.2 26.3 18.3 15.6 38.3 21.0 26.1 13.8 23.0 Avg
Days lost missed heat
Avg days open
13.2 5.6 35.7 38.8 1.8 12.0 5.6 32.3 15.8 .3 10.0
100 101 131 136 91 98 103 124 112 84 103
JOURNAL OF DAIRY SCIENCE VOL. 58, NO. 2
Influence of Estrus Detedion on Days Open in Dairy Herds H. L. BARR Department of Dairy Science The Ohio State University Columbus 43210
Abstract
Data from 10 herds on a herd reproductive status program supported estimates of lost reproduct;ve days per cow per year due to conception failure and missed heat as 23 and 10 days. The corresponding estimates from Ohio Dairy Herd Improvement were 14,7 and 40.3 days. The correlation within the 10 herds between days lost due to failure to conceive and total days open was .38 and between days lost due to missed heats and total days open .92. Introduction
It is a privilege to initiate this discussion on reproductive management. The situation that directed my interest arose from our inability to change substantially herd conception rates even when the full resources of the Department of Dairy Science and College of Veterinary Medicine were focused on certain Ohio herds. The North Carolina Herd Reproduction Status (HRS) (2) program was modified and used in several herds to monitor the situation and to obtain average performance as a guide for Extension teaching. The herds enrolled were on a veterinary herd health program, and the dairymen were asked to report the reproductive status of the cows following each routine veterinary visit. Initially 30 herds were enrolled. Many of the herdsmen became delinquent in their reporting, but 10 herds completed a year's information. Summary Data
While not a large sample, the summary of these 10 herds emphasized some important items. Table 1 presents herd conception rates in two ways. One is the ratio of total services to conceptions in 12 me, and the second is services required to impregnate the cows that settle in 12 me. Some services involved in the latter measure would have preceded the year of conception. Over an extended period the Received July 22, 1974.
total services per conception will be the greater figure, but for a single herd in 1 yr the services to cows conceiving may be greater. In the 10 Ohio herds the conception rates for all cows and. fertile cows were 2,3 and 2.1. Pelissier (3) had previously reported 2.55 and 2.02 services per conception for all cows and fertile cows in large California dairy herds. An early inspection of the HRS data revealed that days open for fertile cows were much more variable than could be attributed to variation in services per conception. Services per conception ranged from 1.7 to 2.8 and could account for no more than 23 days of lost time in reproduction, The range in total days open in these herds was from 84 to 136 days. This represents a range of 52 days. The computer was programmed to partition days open. The events counting for lost days were voluntary waiting by the herdsman, o n e half of a 21-day cycle as an average time lost after intended breeding, time for a new cycle following failure of conception, and missed heats. Days lost due to conception failure w a s calculated by determining services required beyond one and multiplying that number by the 21 days normally required for a cycle. All time not accounted for by the first three events was assigned to missed heats, whether missed by an anestrus cow or an unattentive herdsman. The formula for computing days lost due to missed heat periods was: Missed heats, days lost = Total days open -- Voluntary waiting -- One-half cycle -- [(Services/Conceptions --1) X 21]. Days lost due to missed heat periods include human error, anestrus, and embryonic loss. The partitioning of days lost in reproduction is in Table 2, The correlation between days lost due to failure to conceive and total days open was .38, and the correlation between days lost due to missed heats and total days open was .92. A recent report by Larson (1) indicated no difference in services per conception between cows with long and short ealving intervals. In Ohio D H I herds, which involved 76,610 cows, the recently reported services per conception were 1.7, and the average for days 246
247
SYMPOSIUM
TABLE 1. Conception rates and days open in ten Ohio herds. Herd no.
All services divided by conceptions
No. of conceptions
1 2 3 4 5 6 7 8 9 1O Total
39 30 50 38 263 36 112 22 74 12 683
1.8 1.6 2.8 2.0 2.2 1.7 2.8 2.6 2.9 4.0 Avg 2.3
open was 126. Allowing for 60 days voluntary waiting and partitioning the remainder of the time, it appears that Ohio dairymen are losing 14,7 days due to failure to conceive and 40.3 days due to missed heat periods. This compares with 23 and 10 days for herds on HRS. Expressed in another manner, dairymen on D H I are observing and using 1.7 heats per cow per year and missing 1.9 heats per cow. Approximately 53% of heats are being missed. Conclusion
As a result of the experience with HRS, the following points are emphasized with Ohio dairymen: 1) Herd conception rates are not extremely variable and our ability to influence substantially these rates is limited. 2) Dairymen appear to be losing twice as many days due to missed heat periods as due to failures to conceive.
Services per conception for fertile cows
Days open for fertile cows
1.8 2.2 2.2 2.3 1.9 1.7 2.8 2.0 2.2 1.7 2.1
100 101 131 136 91 98 103 124 112 84 103
3) Because the missed heat category contains days lost due to embryonic loss and anestrus, it is not expected that all anticipated heat periods will be observed. 4) It does appear reasonable, based on HRS herds, to reduce the current days lost of 40.3 (approximately two heats per cow per year) to less than 21 days. References
(1) Larson, L. L. 1974. High cost of low reproduction. Nebraska Dairy Report EC 74220:10. (2) Nicolai, J. H., Jr., and L. C. Ulberg. 1967, North Carolina's system of herd reproductive status. Paper presented at the 20th Annu. Convention Nat. Ass. Anita. Breeders, September 7. Hershey, PA. (3) Pelissier, C. L. 1970. Factors contributing to low breeding e~ciency in dairy herds. Mimeograph with paper E2 presented at tho Sixty-fifth ADSA Annual Meeting, Gainesville, FL.
TABLE 2. Accounting for lost reproductive days.
Herd 1 2 3 4 5 6 7 8 9 10
Voluntary waiting days 60 60 60 60 60 60 60 60 60 60
Avg days to first estrus 11 11 11 11 11 11 11 11 1I 11
Days lost failure to conceive 15.9 25.1 25.2 26.3 18.3 15.6 38.3 21.0 26.1 13.8 23.0 Avg
Days lost missed heat
Avg days open
13.2 5.6 35.7 38.8 1.8 12.0 5.6 32.3 15.8 .3 10.0
100 101 131 136 91 98 103 124 112 84 103
JOURNAL OF DAIRY SCIENCE VOL. 58, NO. 2
