Effect of copper source in enhancing resistance to coliform mastitis

The role of dietary Cu from two Cu sources (organic and inorganic) on Cu repletion, in vitro immune function, mastitis, and enhancing resistance to Escherichia coli mastitis was investigated in first lactation heifers. Twenty-eight primigravid Holstein heifers were individually fed a basal (7.1 mg Cu/kg; CON) diet or diets supplemented (10 mg/kg) with Cu sulfate (CUS) or Cu proteinate (CUP) beginning 60 d prepartum though 49 d of lactation. All heifers were marginally Cu deficient at the onset of supplementation (liver Cu 60 mug/g). Overall mean liver Cu concentration was about three-fold higher in CUS and CUP heifers and there were no differences between the two Cu sources. Overall plasma Cu concentration tended to be greater in CUS and CUP with no differences with Cu source. Plasma ceruloplasmin activity tended to be greater at calving for CUS heifers compared to CON heifers. In vitro neutrophil phagocytosis and killing were not effected by Cu supplementation. At d 34 of lactation, one pathogen-free quarter per animal was infused with 29 colony-forming units of Escherichia coli strain 727. Copper supplementation did not lower peak responses after intramammary challenge though there were variable benefits for Cu supplementation. Supplementation with CUP altered the response of some parameters compared with CON and CUS. Milk bacterial count (log10 cfu/ml) was lower at 24 h and 72 h for CUP heifers compared to CUS and CON heifers, at 48 h milk bacterial count was lower in the group compared to CON, and at 96 h the CUP group had a lower bacterial count than CUS group. White blood cell count (log10 cells/ml) was greater at 36 h for CUP heifers compared with other groups. Plasma Fe concentration was higher at 24 h for both CUP and CUS heifers compared with controls. Milk production following challenge tended to be greater for CUP heifers than CUS heifers. Rectal temperature was lower at 24 h for CUS and CON animals compared with CUP animals. Somatic cell count, dry matter intake, plasma Cu and Zn, and plasma ceruloplasmin did not differ among treatments. Copper supplementation did not alter peak responses after intramammary challenge though there were variable benefits. Supplementation with CUP resulted in apparent improvements in clinical status for some parameters compared to CON and CUS.