title: Effect of subclinical intramammary infection on somatic cell counts and chemical composition of goats' milk.
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 x 10(3) 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.
authors.affiliation: E. Kika de la Garza Institute for Goat Research, Langston University, Langston, OK 73050, USA.
authors.forename: Byeng R
authors.initials: BR
authors.lastname: Min
authors.forename: Grant
authors.initials: G
authors.lastname: Tomita
authors.forename: Steve P
authors.initials: SP
authors.lastname: Hart
mesh_terms: D000818:Animals; D002452:Cell Count; D005260:Female; D006041:Goats; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry* / Q000166:cytology* / Q000382:microbiology; D011549:Pseudomonas / Q000302:isolation & purification; D012705:Serratia / Q000302:isolation & purification; D013210:Staphylococcus / Q000302:isolation & purification