cow with genetic twins

Lancaster Project 2013

  • Previous research work at the University of Wisconsin-Madison has identified a single gene with large effect on ovulation rate in cattle (an increase from the typical single egg to 2-3 eggs ovulated per cycle).  This gene for high ovulation rate will be used as a tool to examine genetic variation in uterine function and reproductive success in cattle by creating a genetically diverse herd with one exception; all cows in the experimental herd would have one copy of the high ovulation rate allele.  These females would be evaluated for multiple reproductive and productive traits and genotyped for purposes of mapping genes contributing to these traits.

Objective

Twin birth holds the potential for dramatic improvement of efficiency of beef cattle production.  However, a number of drawbacks come along with twin births that are a cause for concern.  Among these are problems with a cow’s failure to carry multiple births to term in some cases and dystocia. 

The primary objective of the Lancaster project is to identify genetic contributions to variation between cows in their ability to successfully carry twin births to full-term and deliver live calves at birth.

Experimental Design

  1. Initially, the allele for high ovulation rate will be bred into two disparate breed types, specifically Angus and Jersey.  This is to facilitate the eventual production of males that are homozygous for the allele and essentially Angus x Jersey F1s with regard to breed composition.  A the same time, a herd of Angus x Jersey F1s that are homozygous for the normal allele (typical ovulation rate of one ova per cycle) will be created by mating Angus cows at the Lancaster Research Station to Jersey bulls using sexed semen.  The respective male and female F1s will be mated to produce an F2 generation where all females are heterozygotes with respect to the allele for high ovulation rate. These F2 females will be evaluated for multiple traits both as calves and as cows including growth (weight at birth, weaning, yearling and maturity) and reproduction (age at puberty, ovulation rate, fetal survival, maintenance of pregnancy, unassisted vs assisted calving, weight to height ratio at maturity, stillbirth, dystocia, birth and weaning weight of offspring, interval from parturition to first estrus). Offspring from F2 dams will be tested for leukochimerism (a mixed population of white blood cells derived from a twin and its co-twin) which is an indicator for fusion of placental blood vessels which is related to development of freemartin females and may be related to variation in maintenance of pregnancy.

Frequently Asked Questions

Q: Hasn’t twinning been studied already by USDA?

A: Yes, the USDA Meat Animal Research Center in Clay Center, NE recently terminated a genetic selection study initiated in 1981 in which a herd of cattle was assembled that initially had a twinning rate of ~12%.  Over the ensuing 25+ years of selection for ovulation rate and twinning rate the twinning rate in the herd was increased to >50%.  In addition to the genetic aspects of the project, data from the herd was used to study some of the physiological aspects of twinning.  While this was a very successful research project, the aspect of genetic variation between animals in reproductive success when carrying multiple births was not examined.  The Lancaster project addresses that gap in knowledge.

Q: I am a beef cow-calf producer but have no interest in twinning.  Why should I care?

A: The Lancaster project will generate basic information about genetic variation between cows in their ability to maintain pregnancy.  This information will likely have relevance to single as well as twin birth.  Pregnancy rate has a very significant impact on profitability of beef cow herds.

Q: Why are Angus and Jersey breeds chosen for the cross?

A: Angus are the most popular beef breed in the US currently and are widely used in the maternal side of crosses so their inclusion requires little explanation. The Jersey breed is well documented to have exceptional maternal calving ease (http://www.ars.usda.gov/SP2UserFiles/Place/54380000/GPE/GPE01.pdf), and it is of great interest to see if this will contribute to more successful outcomes in the context of twin births.  The Jersey also provides a contrast with the Angus in terms of age at puberty, lactation and mature size which all have relevance to beef cattle production.

Q: Won’t the use of Jersey in the cross compromise the commercial value of the resulting calves?

A: F1 Angus x Jersey steers would likely be penalized in the feeder cattle market, thus the use of sexed semen in producing both F1 and F2 females to maximize production of females and minimize production of F1 and F2 males.  In subsequent years the mature F2 females will be bred to terminal sire breeds and the resulting calves will be ¼ Jersey, ¼ Angus and half terminal sire breed.  The exceptional maternal calving ease of the Jersey-cross cow will enable them to deliver these calves with few problems (and likely most will be twin births, lessening birth weight).  Like the Angus breed, Jersey will also contribute excellent marbling to the cross with the result that calves will be expected to have carcasses fitting the typical grid very well.  Regarding growth and final market weight, the ¼ contribution of Jersey to the terminal-cross calf will be offset by the terminal sire breed contribution, ensuring acceptable growth weight and final market weight.