Effect of Intramammary Infusion of Tumour Necrosis Factor-α on Milk Protein Composition and Induction of Acute-Phase Protein in the Lactating Cow.

Summary The present study was designed to evaluate the effects of tumour necrosis factor-α (TNF-α) on lactating bovine mammary functions such as milk protein secretion and the integrity of the milk-blood barrier. The effect on the induction of the systemic inflammatory response was also examined using concentrations of serum haptoglobin (Hp), a major inflammatory acute-phase protein, as an index. One hundred micrograms per mammary gland of recombinant bovine (rBo) TNF-α or placebo saline was individually infused into a rear mammary gland of each of four lactating cows, and milk and blood samples were collected before and 4, 8, 24, 32, 48, 96 and 168 h after infusion. In the rBoTNF-α-infused gland, increases of somatic cell counts were observed at 4–48 h. Although concentrations of total milk protein were not changed, compositions of milk proteins varied following rBoTNF-α infusion. Concentrations of caseins, α-lactalbumin and β-lactoglobulin were significantly decreased at 4 and 8 h. Lactoferrin concentrations were significantly increased at 4 h. Significant infiltrations of serum albumin, immunoglobulin G1 (IgG1) and IgG2 were observed at 4 and 8 h. Elevations of the serum concentration of Hp were detected at 8-32 h, but were very small in comparison with those reported in inflammatory diseases. Changes in rectal temperature and white blood cell counts were not significant. These results show that single rBoTNF-α infusion into the lactating mammary gland suppresses the lactogenic function of the gland and influences the function of the milk-blood barrier, with little effect on the generalized inflammatory response. [ABSTRACT FROM AUTHOR]