TNFα altered inflammatory responses, impaired health and productivity, but did not affect glucose or lipid metabolism in early-lactation dairy cows

Abstract

Inflammation may be a major contributing factor to peripartum metabolic disorders in dairy cattle. We tested whether administering an inflammatory cytokine, recombinant bovine tumor necrosis factor-α (rbTNFα), affects milk production, metabolism, and health during this period. Thirty-three Holstein cows (9 primiparous and 24 multiparous) were randomly assigned to 1 of 3 treatments at parturition. Treatments were 0 (Control), 1.5, or 3.0 µg/kg body weight rbTNFα, which were administered once daily by subcutaneous injection for the first 7 days of lactation. Statistical contrasts were used to evaluate the treatment and dose effects of rbTNFα administration. Plasma TNFα concentrations at 16 h post-administration tended to be increased (P<0.10) by rbTNFα administration, but no dose effect (P>0.10) was detected; rbTNFα treatments increased (P<0.01) concentrations of plasma haptoglobin. Most plasma eicosanoids were not affected (P>0.10) by rbTNFα administration, but 6 out of 16 measured eicosanoids changed (P<0.05) over the first week of lactation, reflecting elevated inflammatory mediators in the days immediately following parturition. Dry matter and water intake, milk yield, and milk fat and protein yields were all decreased (P<0.05) by rbTNFα treatments by 15 to 18%. Concentrations of plasma glucose, insulin, β-hydroxybutyrate, non-esterified fatty acids, triglyceride, 3-methylhistidine, and liver triglyceride were unaffected (P>0.10) by rbTNFα treatment. Glucose turnover rate was unaffected (P=0.18) by rbTNFα administration. The higher dose of rbTNFα tended to increase the risk of cows developing one or more health disorders (P=0.08). Taken together, these results indicate that administration of rbTNFα daily for the first 7 days of lactation altered inflammatory responses, impaired milk production and health, but did not significantly affect liver triglyceride accumulation or nutrient metabolism in dairy cows.

Figure 1. Plasma concentrations of TNFα and haptoglobin during 7 days of rbTNFα or Control administration.

(A) Plasma TNFα tended to be increased by rbTNFα treatments (P = 0.09), but no difference was detected between 1.5 and 3.0 µg/kg rbTNFα treatments (P = 0.19). (B) Haptoglobin differed between rbTNFα treatments and Control (P = 0.01), but not between 1.5 and 3.0 µg/kg rbTNFα treatments (P = 0.68). Values are least squares means ± SEM, n = 10–11.

Figure 2. Composite plasma concentration of anti-inflammatory eicosanoids during the first 5 days of rbTNFα or Control administration.

The total anti-inflammatory eicosanoid concentration represents the sum of resolvin D₁ and D₂, protectin, lipoxin A₄, 7-maresin 1, 9-oxoODE, and 13-oxoODE concentrations . The 3.0 µg/kg dose tended to differ from the 1.5 µg/kg rbTNFα dose (P = 0.08), but no overall rbTNFα was detected (P = 0.22). A tendency for a dose by time interaction was also observed (P = 0.06), with a significant dose contrast on day 5 (P<0.01). Values are least squares means ± SEM, n = 10–11.

Figure 3. Hepatic mRNA abundance of TNFα and protein abundance of key mediators involved in inflammatory pathways.

Liver samples were collected after 7 days of rbTNFα or Control administration. (A) Hepatic TNFα transcript abundance was increased by 3.0 vs. 1.5 µg/kg rbTNFα treatments (P = 0.02), but did not differ between rbTNFα treatments and Control (P = 0.73). (B) Western blot images are shown for 6 cows along with densitometry data from analysis of all samples for hepatic IκBα (37 kDa), TNFα (17 kDa), and total and phosphorylated c-Jun (39 kDa). There was a tendency for treatment by parity interaction (P = 0.07) for IκBα, reflecting increased (P = 0.04) IκBα abundance by rbTNFα treatment in primiparous cows (data not shown). No treatment effects (P>0.10) were observed for hepatic TNFα, c-Jun, or relative c-Jun phosphorylation. (C): Parity significantly affected hepatic IκBα (P = 0.02), TNFα (P = 0.04), and relative c-Jun phosphorylation (P = 0.04). Values are means ± SEM, n = 10–11 (A and B) or 9–24 (C).

Figure 4. Hepatic abundance of transcripts involved in lipid metabolism (A) and gluconeogenesis (B).

Liver samples were collected after 7 days of rbTNFα or Control administration. Differences were observed between rbTNFα treatments and Control (P<0.01), and between 1.5 and 3.0 µg/kg rbTNFα treatments (P = 0.04) for CPT1a. No treatment effects (P>0.10) were detected for ApoB, AGPAT1, PCK1, or PC. AGPAT1: 1-acylglycerol-3-phosphate O-acyltransferase 1; ApoB: apolipoprotein B; CPT1a: mitochondrial carnitine palmitoyltransferase 1A; PC: pyruvate carboxylase; PCK1: phosphoenolpyruvate carboxykinase 1. Values are means ± SEM, n = 10–11.