A nested case-control study of uterine prolapse

Graduate Student Literature Review: What do we know about the effects of clinical and subclinical hypocalcemia on health and performance of dairy cows?

This narrative literature review summarizes findings regarding the associations of clinical and subclinical hypocalcemia with postpartum health, reproduction, and milk production. To better understand the effects of hypocalcemia, we reviewed clinical and subclinical presentations of the condition and the dynamics of blood Ca concentration in the early postpartum period. We summarize and discuss the associations between hypocalcemia and performance of dairy cows. Up to 50% of dairy cows suffer from at least one disease event in the transition period. The important roles of calcium in muscle contraction and immune function make it a key component of metabolism, inflammation, and defense against infection. Although the effect of clinical hypocalcemia (milk fever) on health and performance is clear, the definition of subclinical hypocalcemia (SCH) and its consequences for health and performance are still ambiguous. Differences in study designs, sampling protocols, Ca concentration thresholds, and sample sizes that may be underpowered for health and reproduction outcomes lead to inconsistent conclusions on the effects of SCH. On current evidence, classification of SCH should be based on at least 2 measurements of blood calcium, using cutpoints supported with relevant data, which may vary depending on the outcome of interest. Arbitrary or poorly supported interpretative thresholds for blood Ca concentrations should be abandoned. Transient SCH appears to be associated with greater milk yield, whereas SCH that is present several days after calving is associated with lesser production and greater disease risk. However, when blood calcium is measured days after calving, primary effects of calcium metabolism may be confounded by feed intake, inflammation, or disease, which might either contribute to or be a consequence of hypocalcemia. Additional research is needed to refine sampling schemes to classify SCH, and to better inform the goals and means of prevention of SCH.

Abnormalities of the tubular genital organs

Abnormalities of the tubular reproductive tract are responsible for decreased fertility in the cow. Typically, these are related to congenital defects such as segmental aplasia or to acquired conditions resulting from infections or trauma caused during breeding or parturition. Infection of the tubular tract may result in vaginitis, cervicitis, metritis, endometritis, pyometra, or salpingitis. Trauma to the tract may result in urovagina, pneumovagina, or prolapse of the vagina or uterus. Retained placenta may result in metritis. Potentially, all of these conditions, unless properly treated, may result in reduced fertility or, in the extreme, sterility. Judicial and properly timed use of antibiotics and ecbolic agents should return the tract to proper function with little or no reduction in fertility. Some conditions, such as prolapse, retained placenta, and pneumovagina, may call for manual or surgical intervention for successful resolution.