title: Peripartum infection with Streptococcus uberis but not coagulase-negative staphylococci reduced milk production in primiparous cows.
abstract: The effect of an intramammary infection (IMI) at calving on the milk yield of heifers during their first 200 d in milk (DIM) was estimated by comparing monozygotic twins, where one member had a naturally occurring IMI detected at the first milking after calving and the other twin did not. Data collected weekly over a full lactation for 29 twin pairs were used to estimate the effects of a peri-calving Streptococcus uberis IMI on milk yield and composition. Data for 19 twin pairs were used to estimate the effects of pericalving coagulase-negative staphylococci (CNS) IMI. A heifer with a Strep. uberis IMI produced 200 kg (7%) less milk during the first 200 d of lactation compared with her uninfected twin, with significant differences evident throughout the 200-d period. Similar milk losses were recorded for heifers that developed CM or remained subclinical. An elevated milk SCC for infected heifers was only apparent for the first month (d 2-30), although SCC tended to remain high during the second (d 31-60) and third (d 61-90) months. Milk protein concentrations were greater in the Strep. uberis-infected twin over the 200-d period, whereas fat and lactose concentrations showed little change. An IMI caused by Strep. uberis was associated with a lower milk yield, whereas an IMI by CNS was not, despite CNS-infected twins having a higher SCC than their uninfected twin for the first 30 d of lactation.
authors.affiliation: DairyNZ Ltd., Private Bag 3221, Hamilton 3240, New Zealand.
authors.forename: L J
authors.initials: LJ
authors.lastname: Pearson
authors.forename: J H
authors.initials: JH
authors.lastname: Williamson
authors.forename: S-A
authors.initials: SA
authors.lastname: Turner
authors.forename: S J
authors.initials: SJ
authors.lastname: Lacy-Hulbert
authors.forename: J E
authors.initials: JE
authors.lastname: Hillerton
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology* / Q000503:physiopathology; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000378:metabolism; D010298:Parity / Q000502:physiology; D058725:Peripartum Period / Q000502:physiology; D011247:Pregnancy; D013290:Streptococcal Infections / Q000382:microbiology / Q000503:physiopathology / Q000662:veterinary*; D013291:Streptococcus