Calf birth weight and its association with calf and cow survivability, disease incidence, reproductive performance, and milk production

It is known that heavier calves tend to be more prone to stillbirths, dystocia and lower calf survivability than lighter, smaller calves, but it is not known whether calf birth weight is also associated with other factors affecting the economic efficiency of the dairy herd. A number of such factors were included in the study of T.C. Linden and co-workers reported here; the title being: Calf birth weight and its association with calf and cow survivability, disease incidence, reproductive performance, and milk production. The paper was published in the Journal of Dairy Science, Volume 92 of 2009, page 2580 to 2588.

Previous studies have indicated that high calf birth weight was associated with increased calf mortality before birth and with dystocia. Stillbirths themselves have been shown to be a large economic loss as the loss does not only include the value of the calf, but also result in decreased milk production, reproductive performance and survivability. In other studies it was shown that some 7% of calves in the US die within 48 hours because of dystocia. In addition, increased calf birth weight was found to reduce calf weight and height gains between birth and six months of age, thus further contributing to lower economic efficiency in herds.

The question posed by Linden and colleagues was whether calf birth weight also has an effect on overall calf and cow survivability, disease incidence, reproductive performance and milk production. They extended the question to a calf-cow size index, since it was found in previous studies that the relative size of the calf in relation to the dam can play an important role on the detrimental effect of calf size on the subsequent milk production of the dam. The calf-cow index was calculated by dividing the birth weight of the calf by the height of the dam at calving. The study was conducted in a herd with 2800 cows in milk. In addition to cow and calf weights, pregnancy incidence, days to calving, milk production etc., cow disease and lameness events were also recorded. Diseases recorded included displaced abomasums, mastitis, retained placenta and metritis.

The results show that assistance during birth was associated with higher birth weights and a higher calf-cow index. Both factors were also associated with a higher incidence of lameness in the following lactation of the dam, with the calf-cow index the more important factor in this context. Both factors furthermore affected milk production negatively and they were   associated with a higher incidence of metritis and mastitis. They, however, in this study were not associated with stillbirth incidence, calf mortality after 12 hours of life, cow reproduction and cow survival. Nevertheless, farmers should be aware that high calf birth weight and especially high birth weight in relation to the size of the cow may have both direct negative economical effects through obstetrical assistance, stillbirths and dystocia, and negative downstream effects through a higher incidence of lameness and other diseases, as well as lower milk production.