Climatic effects on occurrence of clinical mastitis.
Clinical mastitis records for 6.5 yr from a large north Florida dairy and corresponding daily weather data were analyzed. Monthly incidence of clinical mastitis was expressed as percent of cow-days in milk and graphed against monthly average daily maximum temperature humidity index values and monthly total rainfall. No trends were evident with rainfall. In 3 of 6 yr, monthly incidence of clinical mastitis increased more than 50% above annual incidence, and this followed high monthly temperature-humidity values. Least squares was used to estimate regression coefficients of temperature-humidity index categories based on 999,969 Holstein records. A temperature humidity index category represented the number of days used to calculate average daily maximum temperature-humidity index value. Sources of variation in observed occurrence of clinical mastitis were cow, parity, month, year, interaction of parity by month, and continuous effects of temperature-humidity index categories 2, 6, 15, 30, 60, each to third order and 60 by parity interaction. In all temperature-humidity index categories as the temperature-humidity index value increased, occurrence of clinical mastitis increased. When values rose from 55 to 80, twice as many for 2 d cows showed signs of clinical mastitis.
Morse
D
D
Dairy Science Department, University of Florida, Gainesville 32611.
DeLorenzo
M A
MA
Wilcox
C J
CJ
Collier
R J
RJ
Natzke
R P
RP
Bray
D R
DR
D000818:Animals; D002417:Cattle; D002980:Climate; D005260:Female; D005431:Florida; D006813:Humidity; D008414:Mastitis, Bovine / Q000209:etiology*; D011891:Rain; D013696:Temperature; D014887:Weather