Effect of dose of Streptococcus uberis infused into the mammary gland of lactating cows on clinical signs, bacterial count, somatic cell count and milk production

S. McDOUGALL, K. PARKER, S. SWIFT, S. HARCOURT AND G. SUTHERLAND

Animal Health Centre, PO Box 21, Morrinsville, New Zealand

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NZSAP 2004 Abstract No. 35 Proceedings of the New Zealand Society of Animal Production 64: 143-146

To develop a better understanding of the most common clinical mastitis pathogen in New Zealand dairy cows, Streptococcus uberis (SU), a challenge model is being developed. Four cows were infused with 88 and 888 colony forming units (CFU) of SU in 2 glands in each cow (i.e. all 4 glands in each cow were infused). In another 2 cows, 2 glands were infused with vehicle (Vehicle; n = 4 glands, n = 2 cows) with the other 2 glands not infused (Control; n = 4 glands, n = 2 cows). The rapid mastitis test score was elevated within 24 h post infusion (P=0.02). Streptococcus uberis was isolated from all infused glands, 24 h after infusion and clinical mastitis was detected within 2 to 2.5 d of infusion. The log₁₀ bacterial count at 24 h post-infusion did not differ between the two doses of SU infused (P>0.2). The log₁₀ somatic cell count was higher in the glands infused with 888 CFU of SU compared 88 CFU SU infused glands (3.29 ± 0.17 vs. 2.23 ± 0.17 mean ± SE log₁₀ SCC; P = 0.05). Milk production was depressed following infusion (P = 0.05). It was concluded that clinical mastitis could be induced by a single intramammary infusion of either 88 or 888 CFU of SU.

Keywords: NZSAPAB; Streptococcus uberis; clinical mastitis; SCC

Last Updated 8/07/2004