Photoperiodic Effects on Diurnal Rhythms in Cell Numbers of Peripheral Leukocytes in Domestic Pigs

Abstract

The photoperiod is known to modulate immune cell number and function and is regarded essential for seasonal disease susceptibility. In addition, diurnal variations in the immune system are regarded important for immune competence. Whereas few studies investigated the influence of season, none investigated the specific effect of the photoperiod on these diurnal immune rhythms until now. Therefore, the present study compared diurnal rhythms in cell numbers of peripheral leukocyte types in domestic pigs held either under long day conditions (LD) or short day conditions (SD). Cosinor analyses of cell numbers of various peripheral leukocyte subtypes investigated over periods of 50 h revealed distinct photoperiodic differences in diurnal immune rhythms. Relative amplitudes of cell numbers of total leukocytes, NK cells, T cells, and monocytes in blood were higher under SD than LD. In addition, cell counts of total leukocytes, NK cells, T cells including various T cell subtypes, and eosinophils peaked earlier relative to the time of lights-on under SD than LD. In contrast, diurnal rhythms of neutrophil counts did not show photoperiodic differences. Mesor values did not differ in any leukocyte type. Generalized linear mixed model analyses revealed associations of leukocyte counts with plasma cortisol concentration and activity behavior in most investigated cell types. Moreover, the present study demonstrated photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior, which is in agreement with human and primate studies. The results of the present study imply stronger rhythmicity in leukocyte counts in general under SD. Common intrinsic mechanisms seem to regulate photoperiodic effects on diurnal rhythms in leukocyte counts, except for neutrophils, in domestic pigs. Our results reveal considerable insights into the regulation of immune rhythms in diurnally active species.

Intravenous Infusion of Cortisol, Adrenaline, or Noradrenaline Alters Porcine Immune Cell Numbers and Promotes Innate over Adaptive Immune Functionality

“…During the CTRL period, the investigated leukocyte subsets were similar to previous studies regarding numbers and diurnal pattern (11,32,33). In the stress hormone phase, all of the applied hormones caused changes in the number of distinct leukocyte subsets, as illustrated in Fig.…”

On-Farm Welfare Assessment Protocol for Suckling Piglets: A Pilot Study

“…Despite this, there is still a traditional belief that keeping pigs in semi-dark conditions will reduce aggressiveness, even though this belief has no scientific confirmation and has been confirmed as a baseless practice [ 66 ]. Low illumination levels have been shown to impair pigs vision of object or conspecifics [ 67 ] and to increase cortisol levels [ 68 ]. Some studies have shown that providing more illumination has a positive effect on reducing competitive behaviour in finishing pigs [ 69 ] and feed activity in suckling piglets [ 16 ], although no studies have investigated the effect of light on tail and ear biting in suckling piglets.…”

“…Reduced illumination has been found to reduce feed intake in pigs [ 70 ]. The reduced light exposition has shown also to influence leukocyte counts and plasma cortisol, leading possibly to a major susceptibility to diseases in finishing pigs [ 68 ]. Therefore, the present results recommend investigating the effect of illumination on piglet health and welfare.…”

Efficacy comparison of oseltamivir alone and oseltamivir-antibiotic combination for early resolution of symptoms of severe influenza-A and influenza-B hospitalized patients

“… 3 One of the characteristics of influenza infection is the elevated levels of pro-inflammatory cytokines. 9 Besides having antibacterial abilities, many antibiotics inhibits the production of pro-inflammatory cytokines specially macrolides and fluoroquinolones, which helps in reduction of cytokines level resulting in early resolution of some of the Influenza associated symptoms. 10 …”