|Pan, Deng -|
|Lee, C -|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 2011
Publication Date: July 10, 2011
Citation: Pan, D., Lee, C.N., Rostagno, M.H., Eicher, S.D. 2011. Dam heat load affects neonatal calves’ bacterial prevalence and innate immunity. Journal of Dairy Science. 94 (E-Suppl. 1):744. Technical Abstract: Heat stress is known to suppress animal’s immunity, making them more susceptible to bacterial infections. In Indiana, field observations showed that calves have greater morbidity and mortality when they are born after a heat event. Objectives of this study were to determine whether heat load increases bacterial prevalence in the calving environment or alters calf innate immunity. The study was undertaken in March and August, 2010 on 2 commercial dairies (dairy 1 and dairy 2) located in Hawaii. Fifty-three neonatal Holstein calves were used, 27 born in spring (SP) and 26 born in summer (SU). Hide and udder swabs from the dams on dairy 1 were taken shortly after calving. Rectal and nasal swabs from calves on the same farm (n = 15 and 15 for SP and SU, respectively) were taken 1, 2, and 3 wk after birth. Colony forming units of aerobes and coliforms on those swab samples were determined. Jugular blood samples from calves on dairy 2 (n = 12 and 11 for SP and SU, respectively) were collected wk 1, 2, 3, and 4 after birth to determine blood leukocyte RNA expression of toll-like receptor 4 (TLR4) and tumor necrosis factor-alpha (TNF-alpha). All data were transformed and analyzed using the MIXED procedure of SAS with season and time as fixed effects. Hide and udder coliform counts did not differ between SP and SU cows. Compared to the SP cows, SU cows had greater hide (P = 0.0003) and udder (P = 0.0002) aerobe counts. Rectal coliform counts in SP calves were greater (P < 0.0001) than in SU calves throughout the 3-wk study. SP calves also had greater (P < 0.0001) nasal coliform counts at wk 2. No difference was found in rectal aerobe counts between SP and SU calves. SU calves had greater (P < 0.0001) nasal aerobe counts than SP calves at wk 1 and 3. No difference in TLR4 expression was detected between SP and SU calves. However, TNF-alpha expression in SU calves was less (P < 0.01) at wk 2 compared to SP calves. Our results showed that heat load increased the total aerobes in the calving environment and decreased TNF-alpha expression of neonatal calves, and thus may increase calf morbidity and mortality. This research shows the need to determine additional intervention strategies for calves born under these environmental conditions.