Published on Thu, 12/26/2019 - 9:07am
By Jonathan Statham
Dystocia is expected to occur in ~10%–15% of first-calf heifers and in 3%–5% of mature cattle. Although dystocia cannot be eliminated from a herd, the incidence can be greatly reduced by management decisions made before the breeding season and during gestation.
Heifers and cows should maintain body condition before calving, but over conditioning causes excess fat deposition in the udder and results in lower milk production. Excessive fat deposition in the pelvis also may result in dystocia. Good body condition aids in calving ease, early return to cyclicity in beef cows, and also milk production. There is a balance to achieve between avoiding excessive condition, which leads to dystocia, and insufficient condition, which leads to post-calving sub estrus/anestrus.
Dedicated calving facilities may be needed in many herds. They should be in good repair and functional before the calving season starts. Weather conditions, geographic differences, and local experience usually dictate how much attention and individual care calves will need immediately after birth. The calving environment (e.g., calving sheds, small pastures) must be clean, dry, and protected from the weather. A clean area to handle dystocia problems is also needed. Calving, in a clean area, separated from the rest of the herd, helps to reduce calf hood diseases, particularly diarrhea (scours) and Johne’s disease. In large herds, several small calving pastures that allow regular rotation may help to reduce buildup of disease-causing organisms. When calving stalls are used during inclement weather, they should be cleaned and disinfected between calving’s.
Close observation of labor is necessary to determine when or whether a delivery should be assisted. Labor is divided into three stages. Stage 1 begins with uterine contractions and dilation of the cervix and ends with passage of the amnion and part of the fetus into the vagina. Stage 1 may last 1–24 hr., with 1–4 hr. being normal. Stage 2 is characterized by abdominal contractions due to the fetus in the vaginal canal and ends with expulsion of the fetus through the vulva. Birth should be expected within 1–4 hr. for heifers. A mature cow should calve in <3 hr if the presentation of the calf is normal; if no progress is seen within 1 hr, assistance may be required. Disruption of labor may occur with inappropriate intervention or social group stresses. “Just in time” calving strategies are based around the need to minimize social group changes at the point of calving, because these social changes are associated with challenges to dry-matter feed intake. Stage 3 is expulsion of the fetal membranes and initiation of uterine involution. Expulsion of the fetal membranes normally occurs within 12 hr. after parturition.
Feeding pre-parturient cows in the late morning (11 am–noon) and again at night (9:30–10 pm) encourages cows to calve during the day (7 am–7 pm), when a problem is more likely to be identified and assistance more likely to be available.
Parturition is often difficult for both fetus and dam. Many factors influence the degree of difficulty, including breed, age, nutrition, and pelvic area of the dam; breed and genotype of the sire; gestation length; and sex, size, position, and presentation of the fetus. Some, though not all, of these factors are directly influenced by management.
When dystocia develops, survival of both dam and calf depends on proper assistance. This requires identification of the problem, proper facilities, and adequate help. A delay in assisting may mean the loss of the calf or injury and even death of the cow. However, it is important to allow sufficient time for the dam to dilate before applying traction. Before assisting the delivery, the position of the fetus must be determined accurately, and any abnormal presentation corrected. If the calf is simply too large to pass through the birth canal without danger to the cow or calf, a cesarean section or other surgical assistance may be necessary.
Management after Calving
Muddy lots, crowding, filth, chilling, and inclement weather make the calf more vulnerable to disease organisms and may result in sickness and possibly death for both dam and calf. Provision of adequate trough space, ie, 1 m per fresh cow, and lying space in bedded yards, ie, 1.25 m2/1,000 kg milk yield, are key factors for freshly calved dairy cows to maximize feed intake and minimize risk of poor hygiene on udder health.
Calves receive immunity passively from the dam through ingestion of colostrum. The calf’s immune system is immature at birth and depends on acquisition of passive immunity for disease protection in early life. Immunoglobulins (IgG and IgM) and lymphocytes are absorbed directly across the gut into the calf’s circulation to provide immunity. The ability of the gut to absorb these large molecules and cells is a transient phenomenon; gut closure is complete by 24 hr, and absorption has decreased significantly by 6–8 hr of age. Ingestion of adequate amounts of quality colostrum as early as possible after birth is important for calf survival and growth. Calves with failure of passive transfer (FPT) are 3–9 times more likely to become sick before weaning, and 5 times more likely to die before weaning than calves with adequate passive transfer.
Minimizing the incidence of FPT should emphasize dystocia management, proper nutrition, and intervention for calves at high risk of FPT. Cows that have dystocia should be milked out immediately, and the calf actively fed colostrum to ensure ingestion. Calves should consume 3-4 L as soon as possible after calving by nasogastric tube as necessary. Cows with poor udder conformation or mastitis should be milked, and the colostrum fed to the calf to ensure timely intake. Colostrum supplements may not prove adequate, as shown in controlled clinical trials, to increase serum IgG levels. Vaccination of the cow with pathogens causing enteric disease in calves before calving may be a useful adjunct to good overall management in reducing morbidity. Hygienic management of colostrum is vital to effective absorption, and either careful pasteurization or cooling of lidded containers should be considered.
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