Researchers at Ohio State University wanted to know when you should assist cows giving birth, so they conducted a study to find out. Their goals were to assess the time from the appearance of the amniotic sac (AS) or feet outside the vulva to birth in Holstein cows (first-lactation animals and cows in their second lactation and higher) with (dystocia) or without assistance (eutocia) at calving. And to estimate reference times to be used as guidelines for obstetric intervention in Holstein cows that need assistance during difficult births
Not surprisingly, they found that cows with assisted births (dystocia) had a longer period from the AS or feet appearance to birth and increased incidence of stillbirths compared with cows with unassisted calving. Although not significant, the researchers say it is important to note that the time spent in labor varied for first-lactation animals and cows with multiple lactations.
This study suggested that calving personnel should start assisting cows 70 minutes after AS appearance (or 65 minutes after feet appearance) outside the vulva (based on births without assistance). Under field conditions, the observation of AS or feet appearance outside the vulva as well as calving progress are clear and concrete landmarks that calving personnel can easily identify. Early intervention has the potential to prevent stillbirths, but also has the potential for dam injury due to lack of proper dilation of soft tissues.
When a malposition is evident (like the appearance of one foot outside the vulva) immediately after AS appearance, or for uterine torsions (where the AS or feet do not appear outside the vulva), obstetric intervention is rendered. The time spent in labor (straining) combined with the time from the AS or feet appearance to birth and the assessment of calving progress (as described for non-assisted births) should be used as guidelines to determine the appropriate time for intervention during difficult births under field conditions. Keep in mind, these reference times should be interpreted in combination with adequate obstetrical knowledge and examination. The research was published in the November 2011 Journal of Dairy Science.