Beef Cattle Calving Coping with Calving Difficulties Causes of calving difficulty (dystocia) may be separated into two categories. 1 ) Contributing causes can be identified before the process of giving birth (parturition) begins. 2) Immediate causes are those that can only be recognized after a cow is in labor. At that point dystocia cannot be prevented; only the severity can be minimized. However, the incidence of dystocia can be reduced by management decisions based on understanding the contributing causes. Contributing Causes The younger a heifer is when she calves, the more difficulty she will have. Regardless of age at calving, the highest incidence of dystocia is in first-calf heifers. Second-calf cows have more dystocias than mature cows. Birth size and shape are heritable. Sires can be chosen to reduce calving difficulty. Using a sire breed larger than dam breed in a cross-breeding program tends to increase calving difficulty. However, within each breed are bulls that contribute less difficulty than others. Ease-of-calving data has been tabulated on some bulls used widely in artificial insemination programs. ~ Level of nutrition plays an important role in determing age and weight at puberty and parturition. Most heifers reach puberty before they are large enough to be bred and calve without experiencing difficulty. Malnutrition may result in an undersized or misshapen skeleton, including the pelvis. Over-feeding heifers during late pregnancy to compensate for small size at breeding may favor growth of the fetus, upsetting the balance between fetal size and pelvic diameter. Excessive energy intake may result in deposition of fat in the pelvic cavity, favoring dystocia. An increased incidence of calves presented backward in feedlot heifers has been observed. One possible explanation is that abdominal fat prevents repositioning of the fetus after some critical time during gestation. Diseases that cause late-term abortion or fetal death often result in dystocia. The dead fetus may be presented abnormally or may be distended with fluid or gas. Maternal effects of abortion or fetal death include uterine inertia, failure of the birth canal to dilate, and retained after-birth (placenta). Previous injuries may result in a misshapen birth canal or may produce pain during labor that interferes with delivery. Immediate Causes A large fetus relative to the diameter of the birth canal is the greatest cause of dystocia in heifers calving for the first time. This also accounts for many calving difficulties in second-calf cows and small cows bred to bulls of a larger breed. The other major cause of calving difficulty, mal-position of the fetus as it approaches or enters the birth canal, may occur in any cow regardless of age or size. In animals that ordinarily have one offspring, there is only one normal position of the fetus during birth: right side up, front end first, feet and head extended. Relatively infrequent causes of calving difficulty include abnormalities of fetus or birth canal, failure of birth canel to dilate, or failure of uterus or abdominal muscles to contract effectively. These less frequent situations usually require professional assistance. Normal Parturition Normal parturition is arbitrarily described in three stages. First stage begins with uterine contractions, includes dilatation of the cervix, and ends with entry of the fetus into the birth canal. Restlessness and isolation from the herd may be the only observable signs during this stage. Heifers are generally more restless than older cows. They may appear colicy, lying down and getting up frequently or kicking at their abdomen. The first waterbag may appear toward the end of the first stage. Stage one continues for two to six hours, or sometimes longer in heifers. Second stage comprises passage of the fetus through the birth canal. During this phase the cow actively participates in delivery. Fetal membranes appear and rupture ahead of the fetus, providing lubrication for its passage. Point pressure exerted in the cow's pelvis successively by the head, shoulders, and hips of the fetus intensify abdominal contractions. Mature cows are normally in second stage parturition less than two hours. Heifers may normally require three or four hours. Once feet are showing, they should progressively advance and not appear and disappear with each abdominal contraction. If feet are protruding through the vulva with soles down, they are usually front feet. If soles are up, they are usually hind feet. In a normal forward delivery the front feet are side by side with jaws resting on forelimbs and muzzle at about the fetlocks. The calf passes through the birth canal in an arc. As it enters the pelvic inlet, direction of travel is toward the tailhead of the cow, then parallel to the cow's back, then ever more ventrally. As the calf's hips enter the pelvis, direction of travel is toward the cow's rear feet. This arc keeps the calf high in the pelvic inlet and takes advantage of the widest horizontal diameter of the pelvic opening. Third stage includes passing fetal membranes and closure of the cervix. The placenta is usually expelled within eight hours, after which the cervix secretes a thick mucus that helps prevent infection from entering the uterus. Within 24 to 36 hours a person's hand will not pass through the cervix; by four days only two fingers can be introduced.

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