Symposium title: Small ruminant dairy research - production

Paper title: Milk somatic cells and lactation in small ruminants

Authors: M.J. Paape, A.V. Capuco, A. Contreras, J.C. Marco 

High milk somatic cell counts is a persistent problem for dairy goat producers. The MSCC is the basis for abnormal milk control programs worldwide. The current legal MSCC limit for bulk tank milk for goats in the United States is one million cells per milliliter of milk. If dairymen exceed the legal limit their milk is rejected. The MSCC for goats free from intramammary infection range from two hundred thousand to two million cells per milliliter of milk. Cell counts for sheep are similar to cows and range from ten thousand to two hundred thousand per milliliter of milk. During the secretion of milk in goats and sheep large numbers of cytoplasmic particles, similar in size to milk somatic cells, are shed into milk from cells that secrete milk. Therefore, in order to obtain accurate MSCC, only cell counting procedures that only count cells with a nucleus should be used. Intramammary infection by bacteria and the increase in MSCC in goat milk during estrus and late lactation contribute to the problem in meeting the legal limit. Cell counts for uninfected goat halves can increase to more than one million cells/ml during the latter months of lactation. For sheep, counts are highest during the first few weeks of lactation and decrease to thirty thousand cells per milliliter of milk by the fifth week of lactation, which coincides with maximum milk production. Counts remain unchanged for the remainder of the lactation. Evaluation of 71 bulk tank milk samples from commercial goat herds indicated that 65% of the samples exceeded the legal limit. A way to reduce intramammary infection and MSCC is intramammary administration of antibiotics into goat halves at drying off and post milking teat dipping. However, to be effective both methods must be used. Without teat dipping, the effect of antibiotics at drying off is lost by the second month of lactation. A further clarification on use of MSCC in abnormal milk control programs for goat milk appears justified because of factors other than infection that can influence MSCC for goats. A mastitis control program of administration of antibiotics at drying off and post milking teat dipping is effective in reducing mastitis and MSCC for goats.