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Effect of subclinical intramammary infection on somatic cell counts and chemical composition of goats' milk

Published online by Cambridge University Press:  17 January 2007

Byeng R Min
Affiliation:
E. Kika de la Garza Institute for Goat Research, Langston University, Langston OK 73050, USA Current address: PO Box 1658, Texas A & M Agricultural Research and Extension Center, Vernon TX 76385, USA
Grant Tomita
Affiliation:
E. Kika de la Garza Institute for Goat Research, Langston University, Langston OK 73050, USA Current address: Faculty of Veterinary Medicine, University of Montreal, Saint Hyacinthe, Quebec, J2S 7C6, Canada
Steve P Hart
Affiliation:
E. Kika de la Garza Institute for Goat Research, Langston University, Langston OK 73050, USA

Abstract

We investigated effects of subclinical intramammary infection (IMI) on milk somatic cell count (SCC) and milk composition in udder halves of dairy goats. A total of 35 mixed-age Alpine does (70 udder halves; approximately 55 kg body weight) were rotationally grazed on a mixture of vegetative forages (wheat/berseem clover, sudan grass and cowpeas). Milk samples for bacterial analysis and SCC were collected monthly from both halves from April to September, 2001. Across stages of lactation, 19–31% of udder halves became infected. The prevalence of IMI exhibited quadratic patterns through multi-peaked responses within each stage of lactation. Higher rates of IMI were observed during the early stage of lactation (19% in May) and in the late stage of lactation (31% in September). Coagulase negative Staphylococcus (CNS, 43·7%), Staph. aureus (35·4%), and Pseudomonas aeruginosa (12·4%) were the most prevalent pathogens. Within single-strain IMI, log SCC (6·24) was lower (P<0·01) for CNS than those derived from IMI by Staph. aureus (6·49), Ps. aeruginosa (6·53) or Serratia spp. (6·90). Infected udder halves had a higher average SCC (4761 v. 2259×103 cells/ml; P<0·01) than uninfected halves, but uninfected halves often had similar levels of SCC to infected halves. Daily average milk production was not significantly different between infected and non-infected goats and the relationship between IMI and SCC was not always correlated. Effective mastitis screening requires bacteriological culture since SCC was not highly correlated.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 2007

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