ARS | Publication request: Monitoring Goat and Sheep Milk Somatic Cell Counts

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2006
Publication Date: March 1, 2007
Citation: Paape, M.J., Wiggans, G.R., Bannerman, D.D., Thomas, D.L., Sanders, A.H., Contreras, A., Moroni, P., Miller, R.H. 2007. Monitoring goat and sheep milk somatic cell counts. Small Ruminant Research. 68(1-2):114-125.

Interpretive Summary: Intramammary infection is the major cause for elevated SCC in milk of dairy ruminants. The innate immune system calls into play a host of cytokines critical in the early recruitment of PMN to the mammary gland in response to invading mastitis pathogens. The increase in MSCC due to stage of lactation and parity for cows and sheep are mainly the result of intramammary infections. While intramammary infection increases MSCC for goats, other non-infectious factors such as estrus, season and milk yield will also increase counts in goat milk. For non-infected goat halves, a progressive increase in MSCC is also observed with parity and advanced lactation. North American goat dairymen have difficulties in maintaining bulk tank MSCC below the threshold of 1,000,000/ml. There is currently no legal limit for goat milk in the EU. Non-infectious factors that contribute to elevations in MSCC for goats need to be considered when establishing legal cell count limits.

Technical Abstract: The milk somatic cell count (MSCC) forms the basis of abnormal milk control programs world wide for goats, cows and sheep. To better understand factors that contribute to elevations in MSCC, the effects of stage of lactation, parity, breed and state/area in the United States (US) on MSCC were examined. Least squares means were calculated on composite milk somatic cell scores from 26,607 goats, 5,944,614 cows and 2,197 sheep and the results converted back to MSCC. For goats and cows, MSCC increased with stage of lactation and parity. Counts for cows were lower than counts for goats. By the fifth parity, counts for goats increased to 1,150,000/ml, exceeding the 1,000,000/ml legal limit for goat milk in the US, whereas maximum counts for cows averaged only 300,000/ml, less than the 750,000/ml legal limit in the US and 400,000 in the European Union (EU). Currently, there is no legal limit for goat milk in the EU. For sheep, MSCC for first parity were higher than for later parities. For later parities, MSCC decreased with advanced lactation. Cell counts for sheep milk were similar to counts for cow milk. Breed and state/area contributed to variation in cell count for goats and cows. Data were not available for sheep. Studies in the US and EU examined non-infectious factors contributing to elevations in cell counts. Non-infectious factors such as parity and stage of lactation had minimal effects on MSCC for cows and sheep, but had a major impact on counts for goats, and need to be considered when establishing legal limits for goat milk.