Well I'm not one of those one post wonders you all talk about, you are stuck with me now.
I found this link a while back and all though it refers to dairy cattle, I thought it may be of some use to someone here.
The Pennsylvania State University, Veterinary Science Extension
115 W.L. Henning Building, University Park, PA 16802, TEL: (814) 863-2160 / FAX: (814) 863-6140
This article was printed in the February 2000 edition of Veterinary News
Measures of Reproductive Efficiency When Using Natural Service Programs
For dairy herds that use bulls, either partly or exclusively, in their reproductive program, DHIA records may be useful for evaluating herd reproductive performance. However, this record system is not designed to express efficiency and performance information specifically for natural service programs. In an effort to aid producers and veterinarians, the reproduction committee of the American Association of Bovine Practitioners has published a set of formulas and recommended indices for use in evaluating herd reproductive performance among herds that routinely employ natural service.
Cow to Bull Ratio Formula:
Number of open cows exposed to a bull but
not confirmed pregnant
-divided by-
Number of bulls with access to open cows
The recommended ratio is between 20 and 30 open cows per bull. This calculation can be useful for ruling out insufficient bull power as a cause of herd infertility.
Percentage of Pregnant Cows Resulting
from Natural Service Formula:
Natural service pregnancies X 100
---------------------------
Total pregnancies
This calculation is useful for estimating the contribution of natural service breedings in herds using both natural service and artificial insemination (AI). This parameter requires that conception dates be estimated via palpation so that pregnancies resulting from natural service and AI can be differentiated. High values may signal a problem with some component of the AI program, i.e. semen handling, estrous detection, etc.
Average Days Open with a Bull Formula:
Sum of days between 'date turned with bull'
and 'estimated conception date'
-divided by-
Total number of cows confirmed to a bull breeding
The recommended value is between 40 and 50 days. Elevated values signal an infertility problem within the natural service program but cannot differentiate between a bull or cow specific problem.
Bull Services per Pregnancy Formula:
For all cows confirmed pregnant to a bull during a specified period ...
Average of:
(conception date – [turned with bull date + 10])
-----------------------------------------
21
An estimate of conception rates to the bull can be derived by computing the reciprocal of this figure. This number can then be used to compare conception rates between AI breedings and natural service within a given herd. The 'specified period' is typically a per-month or per year period.
For additional information on these and other reproductive indices described by the reproduction committee of the AABP, the following reference is recommended. Fetrow J, et al. 1990. Calculating selected reproductive indices: Recommendations of the American Association of Bovine Practitioners. J Dairy Sci. 73:78.
Douglas W. Shaw, Ohio Extension Veterinarian, Ohio Vet Newsletter, Fall 1999.
I found this link a while back and all though it refers to dairy cattle, I thought it may be of some use to someone here.
The Pennsylvania State University, Veterinary Science Extension
115 W.L. Henning Building, University Park, PA 16802, TEL: (814) 863-2160 / FAX: (814) 863-6140
This article was printed in the February 2000 edition of Veterinary News
Measures of Reproductive Efficiency When Using Natural Service Programs
For dairy herds that use bulls, either partly or exclusively, in their reproductive program, DHIA records may be useful for evaluating herd reproductive performance. However, this record system is not designed to express efficiency and performance information specifically for natural service programs. In an effort to aid producers and veterinarians, the reproduction committee of the American Association of Bovine Practitioners has published a set of formulas and recommended indices for use in evaluating herd reproductive performance among herds that routinely employ natural service.
Cow to Bull Ratio Formula:
Number of open cows exposed to a bull but
not confirmed pregnant
-divided by-
Number of bulls with access to open cows
The recommended ratio is between 20 and 30 open cows per bull. This calculation can be useful for ruling out insufficient bull power as a cause of herd infertility.
Percentage of Pregnant Cows Resulting
from Natural Service Formula:
Natural service pregnancies X 100
---------------------------
Total pregnancies
This calculation is useful for estimating the contribution of natural service breedings in herds using both natural service and artificial insemination (AI). This parameter requires that conception dates be estimated via palpation so that pregnancies resulting from natural service and AI can be differentiated. High values may signal a problem with some component of the AI program, i.e. semen handling, estrous detection, etc.
Average Days Open with a Bull Formula:
Sum of days between 'date turned with bull'
and 'estimated conception date'
-divided by-
Total number of cows confirmed to a bull breeding
The recommended value is between 40 and 50 days. Elevated values signal an infertility problem within the natural service program but cannot differentiate between a bull or cow specific problem.
Bull Services per Pregnancy Formula:
For all cows confirmed pregnant to a bull during a specified period ...
Average of:
(conception date – [turned with bull date + 10])
-----------------------------------------
21
An estimate of conception rates to the bull can be derived by computing the reciprocal of this figure. This number can then be used to compare conception rates between AI breedings and natural service within a given herd. The 'specified period' is typically a per-month or per year period.
For additional information on these and other reproductive indices described by the reproduction committee of the AABP, the following reference is recommended. Fetrow J, et al. 1990. Calculating selected reproductive indices: Recommendations of the American Association of Bovine Practitioners. J Dairy Sci. 73:78.
Douglas W. Shaw, Ohio Extension Veterinarian, Ohio Vet Newsletter, Fall 1999.
