Bacterial Cell Counts in Goat Milk and Their Correlations with Somatic Cell Counts, Percent Fat, and Protein

Abstract

Representative milk samples at morning and afternoon milking were collected periodically for 5 mo from 32 does in a Prairie View A&M University milking herd to test the concentrations of total bacterial, coliform, and staphylococcus counts and to determine the correlations among the bacterial cell counts, somatic cell counts, percent fat, and percent protein. Bacterial cell counts were assayed by microbiogical methods using different nutrient media for the three cell types. Somatic cell counts were determined by an automated fluorescent microscopic somatic cell counter. Percent fat and protein were analyzed by an automated dual beam infrared absorption analyzer. Mean counts for total bacterial, coliform, staphylococcus, and somatic cell were 2.54 × 104, .966 × 103, 3.32 × 103, and 9.08 × 105 cells/ml, respectively. The Nubian goats had higher counts in all three bacterial cell types than the Alpines, and the difference in staphylococcus counts between breeds was significant (P<.05). However, Alpine milk contained slightly higher somatic cell counts than the Nubians. None of the correlation coefficients (r) between somatic cell and bacterial cell counts was significant for the pooled data from the two breeds, but r between staphylococcus and somatic cell counts for Alpine breed was significant (P<.05). The r between somatic cell counts and percent fat or protein were significant (P<.01) for combined or separated breed data. Bacterial cell counts could not explain high somatic cell counts in the goat milk with the present testing standards of cow milk.