Subclinical mastitis in goats is associated with upregulation of nitric oxide-derived oxidative stress that causes reduction of milk antioxidative properties and impairment of its quality.
The aim of this study was to verify the existence of a nitric oxide (NO) cycle in goat milk and to study how changes in it affect milk composition during subclinical mastitis. Fifteen lactating dairy goats in which one udder-half was free from bacterial infection and the contra-lateral one was naturally infected with various species of coagulase-negative staphylococci were used. In comparison to uninfected glands, subclinical mastitis was associated with a decrease in milk yield, lactose concentration, and curd yield and an increase in nitrite and nitrate concentrations and with measurements reflecting increased formation of NO-derived free-radical nitrogen dioxide. The occurrence of NO cycling in goat milk was largely confirmed. The increase in the NO-derived stress during subclinical infection was not associated with significant increase in oxidatively modified substances, 3-nitrotyrosine, and carbonyls on proteins, but with increased levels of peroxides on fat. However, the relatively modest nitrosative stress in subclinically infected glands was associated with significant reduction in total antioxidant capacity and vitamin C levels in milk. We concluded that subclinical mastitis in goats caused by coagulase-negative staphylococci imposes negative changes in milk yield, milk quality for cheese production, and negatively affects the nutritional value of milk as food. Thus, subclinical mastitis in goats should be considered as a serious economic burden both by farmers and by the dairy industry.
Biology of Lactation Laboratory, Institute of Animal Science, A.R.O., the Volcani Center, PO Box 6, Bet Dagan 50250, Israel. Electronic address: nsilanik@agri.huji.ac.il.
Nissim
N
Silanikove
Department of Food Quality and Safety, Postharvest and Food Sciences, A.R.O., the Volcani Center, PO Box 6, Bet Dagan 50250, Israel.
Uzi
U
Merin
Biology of Lactation Laboratory, Institute of Animal Science, A.R.O., the Volcani Center, PO Box 6, Bet Dagan 50250, Israel.
Fira
F
Shapiro
National Mastitis Center, Kimron Veterinary Institute, PO Box 12, Bet Dagan 50250, Israel.
Gabriel
G
Leitner
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001424:Bacterial Infections / Q000662:veterinary; D005260:Female; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D006041:Goats; D007774:Lactation / Q000502:physiology; D007785:Lactose / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000382:microbiology; D008413:Mastitis / Q000382:microbiology / Q000662:veterinary*; D008892:Milk / Q000737:chemistry* / Q000382:microbiology; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress; D010545:Peroxides / Q000378:metabolism; D050050:Protein Carbonylation; D013210:Staphylococcus / Q000302:isolation & purification*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000975:Antioxidants; D010545:Peroxides; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D007785:Lactose
antioxidant capacity; goat; milk; oxidative stress; subclinical mastitis