“It is estimated that about 2% of beef cattle pregnancies result in twins,” said veterinarian Bob Larson. He explained that twins are the result of either a double ovulation by the cow or an embryo that splits very early in development.
When a heifer twin shares the uterus with a bull fetus, they also share the placental membranes connecting the fetuses with the dam.” A joining of the placental membranes occurs at about day 40 of pregnancy; thereafter, the fluids of the two fetuses are mixed.
These identical twins, whether they be two males or two females, should breed quite normally. In the great majority of cases, the cow sheds only one egg at each heat period.
Twin birth is a complex condition observed in most livestock animals, when the female gives birth to two or more offspring, generally out of the same mating. In cattle, it is a rare condition (3 to 5%) and depends on the genetic background and environmental factors.
Many producers have herds of 50 or fewer cows and only two bulls. Dominance is just as much an issue for smaller herds as for larger ones.
With spring bull sales in full swing, cow-calf operators are assessing their bull batteries and making needed purchases; however, in most cases, producers should not place young bulls in the same breeding pasture as older, larger bulls.
Mating of beef cattle that are close relatives (brother-sister, sire-daughter, son-dam) produces high levels of inbreeding. Inbreeding generally is detrimental to long-term reproductive performance and growth. Highly inbred cattle are also more susceptible to environmental stress and health problems.
Usually a bull will mate with a cow once, but it's not uncommon if it's done several times, especially if she has garnered the attention of more than one.
Most twins occur when the cow ovulates two eggs, which are then fertilized, producing fraternal twins. When one egg is fertilized and splits, we see identical twins. Multiple ovulation is a slightly heritable trait, so the genetics for twinning is most likely in your cow herd.
Although the male twin in this case is only affected by reduced fertility, in over ninety percent of the cases, the female twin is completely infertile.
Producers can identify freemartins by examining the external genitalia. A prominent clitoris and loosely attached or feathery vulval lips are a dead give away. The genital opening may be located down between the back legs toward where the prepuce would be on a bull.
Estimates of the percentage of beef cattle births that produce twins vary. One estimate (Gilmore) puts the percentage at about 0.5% or 1 in every 200 births. Approximately one-half of the sets of twins should contain both a bull and a heifer calf.
You can have father-daughter matings in beef cattle, but it is not recommended. This type of breeding practice is called inbreeding or close breeding. Again, this breeding practice is rarely practiced today, although it was common in the foundation animals of most breeds.
An ultrasound between 45-and-90-days of gestation is the best time for indicating two embryos. Beyond that, he says the producer probably won't know if there is more than one calf until the cow gives birth.
3. What is a 'Freemartin”? When a set of twins is born and one is a bull calf and the other is a heifer calf, more than 90% of the time the female is infertile. The infertile female twin is called a freemartin.
An inbred individual is more likely to be homozygous for any gene, so the animal is more likely to express undesirable genes, and hence, undesirable traits. Inbreeding does not create undesirable recessive genes, but it does tend to bring to light these unfavorable genetics.
August 16, 2021 Sara Beth 2 comments
When it comes to calving season, twins are an unusual occurrence, but not necessarily rare. It's estimated that anywhere between 1-2% of beef cattle pregnancies will result in a twin birth. That number tends to be slightly higher in dairy cattle.
Firstly, what determines if a calf is a bull or a heifer? A cow will pass on one X chromosome to the calf and a bull will pass on either one X chromosome or one Y chromosome to the calf. This means that the calf will either have XX (two X chromosomes) or XY (one X and one Y chromosome).
Only one animal consistently gives birth to identical twins, Durrant says, and that's the nine-banded armadillo.
But, if you mate a bull to its mother, 75% of the genetic make-up will be the same and the chance of the fault occurring simultaneously in both chains is very high. This is called in-breeding and must be avoided wherever and whenever possible.
“It is estimated that about 2% of beef cattle pregnancies result in twins,” said veterinarian Bob Larson. He explained that twins are the result of either a double ovulation by the cow or an embryo that splits very early in development.
The risk of twin pregnancy is much more common in older cows [8,9] and so is the associated risk of abortion [7,10]. Twin pregnancies may account for 25% of all pregnancies on Day 90 of gestation in cows in their third lactation or more [11].
The good news is: It is possible to leave bulls with the cows year-round and still maintain a calving season of three months or less.
Bulls 18 months old, 20 to 25 cows. Mature bulls (24 months and older), 25 to 30 cows. the amount of normal (i.e. quantity and quality) semen a bull is able to produce within a set period of time ▪ and is significantly affected by the bull's libido and mating dexterity.
Health. When there are bulls turned loose in the herd, your cows stand a higher chance of being injured during mating or during attacks from other cattle, or suffering from health problems as the result of calving.