Neutrophil function and energy status in Holstein cows with uterine health disorders

Abstract

The objectives of this study were to investigate the associations between peripheral blood neutrophil (PMN) function, energy status, and uterine health in periparturient dairy cows. Data were collected from 83 multiparous Holstein cows. Blood samples for PMN function determination were collected weekly from 1 week prior to calving (week −1) through 4 weeks after calving and again at 8 weeks after calving. Energy metabolites were measured and dry matter intake (DMI) was determined from weeks −2 to 5 to evaluate energy status of cows during the periparturient period. All cows were examined for uterine health disorders. Blood PMN killing ability was evaluated by determining myeloperoxidase activity and cytochrome c reduction activity in isolated blood PMN's. For cows that were diagnosed with puerperal metritis and subclinical (SC) endometritis and puerperal metritis, blood PMN functions were significantly (P < 0.05) impaired during the periparturient period, compared to cows with normal uterine health. Cows with subclinical endometritis and puerperal metritis or SC endometritis also had significantly (P < 0.01) higher NEFA and significantly (P < 0.001) lower DMI during the periparturient period, and significantly (P < 0.05) higher BHBA during early lactation, compared to cows with normal uterine health. Neutrophil function was also significantly (P < 0.01) impaired in cows with peripartum negative energy balance, which was characterized by elevated blood levels of NEFA and decreased DMI. Decreased PMN function and energy balance were associated with uterine health disorders and the decreases in PMN function and energy balance occurred prior to parturition and prior to the detection of these uterine disorders.

Introduction

Maximizing reproductive efficiency is the goal of reproductive management programs in dairy herds. Infection and subsequent inflammation of the bovine uterus compromise uterine health and contribute to decreased reproductive efficiency in dairy cows (Coleman et al., 1985, Fourichon et al., 2000). Metritis and endometritis (LeBlanc et al., 2002) are prevalent in dairy herds and contribute to increased days to first breeding, decreased conception rate and pregnancy rate, and increased culling. Subclinical endometritis, based on uterine cytological examination, is also prevalent in dairy cows and has a profound negative impact on reproductive performance. Gilbert et al. (2005) and Hammon et al. (2001) reported that cows with subclinical (SC) endometritis had lower conception rates and higher reproductive failure rates, compared to cows without SC endometritis. More recently, Kasimanickam et al. (2004) showed that cows with SC endometritis, based on endometrial cytology examination at 34–47 DMI, had significantly lower first service and all service conception rates compared to cows without endometritis.

Peripheral blood neutrophil (PMN) function of periparturient dairy cows is impaired relative to non-parturient cattle (Kehrli et al., 1989, Cai et al., 1994). Blood PMN function begins to decline prior to parturition, reaches a nadir shortly after parturition, and slowly returns to prepartum levels by about 4 weeks postpartum (Kehrli et al., 1989). Studies have shown a relationship between periparturient PMN function suppression during the periparturient period and retained placenta (RP) (Gunnink, 1984, Kimura et al., 2002) and metritis (Cai et al., 1994) in dairy cows. Neutrophils from cows with RP have decreased migration ability (Gunnink, 1984) and decreased myeloperoxidase activity (Kimura et al., 2002). Blood neutrophil functions in periparturient dairy cows with SC endometritis have not been reported.

Decreased DMI prior to parturition is well documented and is associated with mobilization of lipids, which are released as NEFA from adipose tissue (Grummer et al., 2004). Decreased DMI and increased NEFA levels are temporally associated with periparturient immune function suppression and may contribute to impairment of the immune system in dairy cows (Rukkwamsuk et al., 1999). Furthermore, elevated levels of β-hydroxybutyric acid (BHBA) and other ketones have been shown to impair important functions of immune cells with possible implications for systemic infections postpartum (Klucinski et al., 1988). Kremer et al. (1993) reported that cows in negative energy balance (with elevated BHBA) prior to experimental infection of the mammary gland experienced more severe mastitis compared to cows with low blood BHBA concentrations, indicating that negative energy balance may predispose cows to severe infections. Hoeben et al. (1997) reported that exposure of PMN's to elevated levels of BHBA reduced PMN respiratory burst and they concluded that BHBA may, in part, be responsible for the higher susceptibility to local and systemic infections during the postpartum period. There is also evidence of an association between elevated levels of milk ketones (acetone) and endometritis in dairy cows (Reist et al., 2003). However, interrelationships between peripartum energy status, PMN function, and uterine health are not well understood.

We hypothesize that impaired PMN function and negative energy balance are associated with and occur prior to the onset of uterine health disorders in dairy cows. The objectives of this study were to evaluate the interrelationship between uterine health disorders, energy status, and PMN function in periparturient dairy cows.