Pregnancy Data

Phenotype

Pregnancy is defined as the time period in which the female carries one or more live offspring from conceptus to birth. Pregnancy status (not pregnant or open vs. pregnant) should be recorded on each breeding female that was exposed to a bull. Therefore, a cow exposure inventory is important to increase efficiency of pregnancy diagnosis. It is similar to heifer exposure inventory. Diagnosing pregnancy accurately and in a timely manner is of key economic importance to producers. Methods, which should be conducted by trained personnel, include:

Clinical method	Time period	Accuracy	Precautions	Source
Rectal palpation	After 35 days post breeding	Moderate to highly accurate, depends on technician training	Does not provide information on viability of fetus	Roberts (1985); Purohit (2010)
Ultrasonography	Rectal: After 27 days post breeding (amniotic fluid is visible by day 18) Flank: 72 to 190 days post breeding	High accuracy at day 28 or later for rectal ultrasonography	Flank is too late in pregnancy for increasing reproductive efficiency	Goddard (1995); Purohit (2010)
Abdominal ballottement	After 7 months	High accuracy	Too late in pregnancy for increasing reproductive efficiency	Purohit (2010)
Blood tests	As early as 30 days after insemination	High accuracy	Only provides yes/no outcome. Accuracy in open cows is slightly lower (95%) compared to pregnant cows (99%).	Green et al. (2009); Lucy et al. (2011)

The choice of method for pregnancy diagnosis is dependent on cost and information needed by the producer. The cheapest method would be rectal palpation, but experience is needed for early pregnancy detection.

Cow Reproductive Efficiency

There is no adjusted value made to pregnancy status. Herd reproductive efficiency can be characterized using pregnancy status of each cow in the herd, which is important for early indications of reproductive efficiency (or inefficiency) that will impact profit margins. Measures to calculate include:

1. Number of cows exposed. This is the number of cows exposed to either A.I. or natural service breeding, either in the present year’s breeding season or in the past year’s breeding season. This figure should be calculated on a bull-mating group basis.

2. Percent diagnosed pregnant. This is a measure of the success of the breeding season. It can be calculated for all animals in the herd or within bull-mating groups. It is calculated as:

Percent Diagnosed = (No. of cows diagnosed pregnant ÷ No. of cows exposed) X 100

3. Live calving percent. This is a measure of success of the breeding and calving seasons calculated as:

Live calving percent = (No. of live calves ÷ (No. of cows exposed – No. of cows sold or died Percent + No. of pregnant cows purchased)) X 100

4. Weaning percent. Also called “percent calf crop weaned”, weaning percent is a measure of overall reproductive efficiency for that calving season across the herd or within bull-mating groups. It is calculated as:

Weaning percent = ((No. of calves weaned + No. calves sold pre-weaning) ÷ (No. cows exposed – No. cows sold or died + No. of pregnant cows purchased)) X 100

Genetic Evaluation

Traditional prediction methods to estimate breeding values for reproductive traits have not been widely employed. Many such traits are lowly heritable (e.g., Cammack et al., 2009). Also, records necessary to compute the estimates have not been available from non-inventory-based breed association improvement programs. New statistical estimation procedures (using threshold models to analyze calving success vs failure, for example) and inventory-based performance recording make it likely that EPDs for reproductive traits will become more readily available in the future. Stayability EPD are one such attempt at incorporating reproductive performance into selection programs.

Usage

Pregnancy is an economically relevant trait. Cows should be pregnancy tested by trained personnel prior to determining a breeding herd inventory for the coming year. As a cow-calf producer’s income depends on weaning percent and the weaning weight of those calves sold, determining potential calf numbers based on pregnancy status can be economically advantageous to the producer. This can increase reproductive efficiency and growth efficiency (i.e., more calves growing). Pregnancy diagnosis can help the producer cull open cows so that resources are focused on consistent breeders. Furthermore, detailed pregnancy diagnosis, such as using rectal ultrasonography, can provide information on expected calving dates so that the producer can plan resources appropriately.

References:

Cammack, K.M., M.G. Thomas, and R.M. Enns. 2009. Review: Reproductive traits and their heritabilities in beef cattle. Prof. Anim. Scientist 25(5):517-528. [1]

Goddard, P.J. 1995. Veterinary Ultrasonography. CAB International. Wallingford, UK. [2]

Green, J.C., D.H. Volkmann, S.E. Poock, M.F. McGrath, M. Ehrhardt, A.E. Moseley, and M.C. Lucy. 2009. Technical note: A rapid enzyme linked immunosorbent assay blood test for pregnancy in dairy and beef cattle. J. Dairy Sci. 92: 3819-3824. [3]

Lucy, M., J. Green, and S. Poock. 2011. Pregnancy determination in cattle: a review of available alternatives. Proc. Applied Reproductive Strategies in Cattle. Joplin, MO. Available at [4]

Purohit, G. 2010. Methods of pregnancy diagnosis in domestic animals: The current status. Reproduction 1(12): WMC001305. [5]