The perinatal period is the most critical time for neonatal calves because it has the highest risk of morbidity and mortality. In the U.S., the prevalence of perinatal mortality (PM), the death prior to, during, or within 48 hours of birth after a normal gestation, was 8.1% (USDA, 2010). It was about 2 to 5 times higher in first-calf heifers than cows. No doubt, dystocia is the No. 1 cause of this. In a study recording nearly 7,400 calvings, the incidences of PM for unassisted, mild dystocia (one person with hand pull), and severe dystocia (requiring ≥2 persons’ assistance) were 3.2, 8.4, and 37.2%, respectively. Not only genetic factors, but also non-genetic factors, especially inappropriate calving management, can result in or exacerbate dystocia. Earlier research reported about 75% of PM happened within 1 hour of calving. Recently a German research group found the prolonged stage II of labor (interval from water sac appearance to complete expulsion of calf) and abnormal fetal presentation were the highest risk factors for PM. These two factors are associated with management an hour or two before calving. This article will summarize some recent research results regarding three aspects of calving management concerning the hour around parturition.
1. Time to move. The majority (~96%) of dairy farms use maternity pens (group or individual calving pens). Pen moving always creates social and environment stress, but improper moving decisions for calving are much more detrimental. When and how to move are the key questions. Research from the University of Minnesota found the incidence of PM was 2.5 times higher when cows were moved at stage I of labor (mucus discharge) vs. moving when water sac or feet were expelled (stage II). Cows moved during late stage I (bloody mucus) spent more time standing 1 hour before calving and experienced prolonged stage II of labor in comparison with moving 2-3 days before labor or during early stage I of labor (udder swelling, relaxed pelvic ligand or raised tail), So far, late stage I seems to be the worst time for moving, primarily due to the interruption of labor progress. The behavior indicators that can be used to identify late stage I include frequent position change, continuous sniffing ground (more in a bedded pack), social isolation in a corner, frequent standing/lying and turning around in the same place, and start of abdominal contraction.
Currently there is no research available comparing moving at different stages with remaining in the close-up bedded pack for calving. Either an early move or only at stage II depends on the specific situation of each farm (labor, type of close-up pen and calving pen). Early moving requires more labor for calving pen cleaning and maternity units for large farms, whereas late moving needs more frequent calving checks, especially during the night shift. If you have a group-calving pen and want to move earlier, it’s always better to move a few cows than a single cow to reduce the social stress.
2. Time to give a hand. During stage II of labor, the fetal calf has been expelled to the birth canal. The straining of labor will reduce the fetal oxygen supply, particularly with dystocia, due to compression of umbilical blood flow, and result in hypoxia of the calf. If hypoxia extends, respiratory and secondary metabolic acidosis ensues, which is life-threatening, or even anoxia. Hence, the determination of a “golden window” for providing calving assistance during stage II is critical. The earlier recommendation of “two-feet-two hours” means that staff should intervene when calf is not expulsed after two hours of feet presence. However, more recently the Ohio State research group recommends assisting calving 65 minutes after feet appearance or 70 minutes after water sac presence. This much shorter reference time was based on continuous monitoring of the labor processes by 5 cows and 5 first-calf heifers.
3. Calf resuscitation: ASAP. Since most dystocia calvings were managed by farm staff, an SOP should be setup including how to identify endangered calves before or immediately after calving, procedures to perform resuscitation, and simple instructions for first-aid equipment, if available. During difficult calvings calf viability should be checked when the calf is still in the birth canal. Loss of the interdigital reflex to pinch, extruding swollen tongues and cyanosed gums are the most common indications of hypoxia. Resuscitation should be performed immediately after calving for endangered calves by cleaning the airway and stimulation of respiration. Although 66% of farms hang calves upside down for draining lung fluid, this not recommended due to two concerns: 1) Abomasum fluid was drained rather than lung fluid. 2) It increases chest pressure and makes it harder for calf to breathe (USDA, 2010). Several simple methods to stimulate breathing have been widely used including straw stimulation in nostril, cold water stimulus on ear, and putting the calf in the sternal recumbence position. Respiratory stimulating drugs were only used by < 3% of herds, primarily due to the lack of convincing beneficial evidence, however, recent research from Switzerland found that 1-2 mg/kg by body weight of doxapram (IV administration) can sharply increase respiratory rates and minute volume, arterial O2 pressure and alleviate acidosis within 1 minute and lasting up to 90 minutes after administration. Several other drugs (theophylline, prethcamide and lobeline) failed to give such quick and equivalent improvements.
