Impacts of chronic and increasing lipopolysaccharide exposure on production and reproductive parameters in lactating Holstein dairy cows

Abstract

Lipopolysaccharide (LPS) administration causes immunoactivation, which negatively affects production and fertility, but experimental exposure via an acute bolus is unlikely to resemble natural infections. Thus, the objectives were to characterize effects of chronic endotoxemia on production parameters and follicular development in estrous-synchronized lactating cows. Eleven Holstein cows (169 ± 20 d in milk; 681 ± 16 kg of body weight) were acclimated to their environmental surroundings for 3 d and then enrolled in 2 experimental periods (P). During P1 (3 d) cows consumed feed ad libitum and baseline samples were obtained. During P2 (7 d), cows were assigned to continuous infusion of either (1) saline-infused and pair-fed (CON-PF; 40 mL/h of saline i.v.; n = 5) or (2) LPS infused and ad libitum fed (LPS-AL; Escherichia coli O55:B5; 0.017, 0.020, 0.026, 0.036, 0.055, 0.088, and 0.148 μg/kg of body weight/h i.v. on d 1 to 7, respectively; n = 6). Controls were pair-fed to the LPS-AL group to eliminate confounding effects of dissimilar nutrient intake. Infusing LPS temporally caused mild hyperthermia on d 1 to 3 (+0.49°C) relative to baseline. Dry matter intake of LPS-AL cows decreased (28%) on d 1 of P2, then progressively returned to baseline. Relative to baseline, milk yield from LPS-AL cows was decreased on d 1 of P2 (12%). No treatment differences were observed in milk yield during P2. Follicular growth, dominant follicle size, serum progesterone (P4), and follicular P4 and 17β-estradiol concentrations were similar between treatments. Serum 17β-estradiol tended to increase (115%) and serum amyloid A and LPS-binding protein were increased (118 and 40%, respectively) in LPS-AL relative to CON-PF cows. Compared with CON-PF, neutrophils in LPS-AL cows were initially increased (45%), then gradually decreased. In contrast, monocytes were initially decreased (40%) and progressively increased with time in the LPS-AL cows. Hepatic mRNA abundance of cytochrome P450 family 2 subfamily C (CYP2C) or CYP3A was not affected by LPS, nor was there a treatment effect on toll-like receptor 4 or LBP; however, acyloxyacyl hydrolase and RELA subunit of nuclear factor kappa B tended to be increased in LPS-AL cows. These data suggest lactating dairy cows become tolerant to chronic and exponentially increasing LPS infusion in terms of production and reproductive parameters.

Effects of continuous and increasing lipopolysaccharide infusion on basal and stimulated metabolism in lactating Holstein cows

“…In fact, a bolus dose of just 2.0 µg/ kg of BW can be fatal in LPS-naive lactating cows (Waldron et al, 2003). That there were little to no effects on most production variables by the end of the current experiment illustrates the profound capabilities of cows to develop tolerance to constant LPS exposure (Dickson et al, 2019).…”

“…Detailed production and immunological data are presented in the companion paper (Dickson et al, 2019); in brief, feed intake milk yield initially decreased (d 1 of infusion) and progressively increased with time. Milk yield did not differ by treatment and, by experimental design, the extent and pattern of DMI did not differ.…”

“…Surprisingly, despite obviously developing tolerance (from a production standpoint; see Dickson et al, 2019), changes in whole-body nutrient partitioning were reflective of systemic infection. During natural infection, bacteria replicate on a logistic rather than an exponential curve and the microbial population consists of multiple species and strains differing in virulence (Contois, 1959;Crutchley et al, 1967).…”

“…Production and immunological data are reported elsewhere (Dickson et al, 2019). Metabolic responses to the GTT and EC were calculated as area under the curve (AUC) by linear trapezoidal summation between successive pairs of metabolite concentrations and time coordinates after subtracting baseline values.…”

Mismatch of Glucose Allocation between Different Life Functions in the Transition Period of Dairy Cows

“…Milk production of cows challenged with intramammary infusion of 30 cfu [ 147 ], 1 × 10 4 cfu of diluted E. coli per quarter or 1000 µg LPS [ 148 ] decreased to low levels. In contrast, milk yield was unaffected by chronic and exponentially increasing intravenous infusions of LPS (0.017–0.148 μg/kg of body weight per hour from day 1 to 7) in a recently conducted study [ 149 ]. Daily subcutaneous injection of 3 µg/kg body weight of bovine tumor necrosis factor-α during the first week of lactation decreased milk yield only slightly (33.7 to 28.4 kg at highest dose) [ 149 ].…”