Evaluation of the relationship between milk glutathione peroxidase activity, milk composition and various parameters of subclinical mastitis under seasonal variations

The aims of this study were to evaluate the Glutathione peroxidase (GSH-Px) activity in milk, and various milk parameters [milk fat, milk protein, milk solids non-fat (SNF), somatic cell count (SCC), total bacteria count (TBC), electrical conductivity (EC)] in healthy dairy cows during lactation, and to demonstrate the significant correlations between GSH-Px activity, milk composition, SCC, TBC and EC under seasonal variations. The cows calving in January were assigned into the winter group (n = 30) while the other cows calving in August were assigned into the summer group (n = 30). Milk samples were collected weekly during lactation, and monthly average values of the parameters were determined. Although milk GSH-Px activity was variable during lactation, it was significantly higher in the winter group compared to the summer group of cows during the first five months of lactation (P<0.001). However, between the 6th and 10th months of lactation, GSH-Px activity was significantly higher in the summer group (P<0.001). In both groups of cows, GSH-Px activity was negatively correlated with SCC, TBC and EC during lactation. No correlation was found between GSH-Px activity and milk composition. In conclusion, the alteration of milk GSH-Px levels could be used as a diagnostic tool for monitoring udder health due to its relationship with the parameters of subclinical mastitis. Furthermore, cows calving in winter had higher GSH-Px activity than those calving in summer, especially during the first few months of lactation. These findings indicate that milk GSH-Px activity in cows during lactation could be influenced by seasonal variations.Ciljevi ovog istraživanja bili su, tijekom laktacje zdravih krava, procijeniti aktivnost glutation peroksidaze (GSH-Px) u mlijeku te odrediti različite druge sastojke (mliječnu masti, mliječne bjelančevine, bezmasnu suhu tvar, broj somatskih stanica (SCC), ukupan broj bakterija (TBC), električnu provodljivost (EC) i prikazati značajnost korelacija između aktivnosti GSH-Px, sastava mlijeka, SCC, TBC i EC u uvjetima različitih sezona. Krave oteljene u siječnju raspoređene su u zimsku skupinu (n = 30), dok su ostale krave oteljene u kolovozu dodijeljene ljetnoj skupini (n = 30). Tijekom laktacije, uzorci mlijeka su prikupljani jednom tjedno i na temelju toga za svaki pokazatelj utvrđene su prosječne mjesečne vrijednosti. Iako je aktivnost GSH-Px u mlijeku tijekom laktacije bila varijabilna, krave iz zimske skupine imale su u prvih pet mjesci značajno (P<0,001) višu aktivnost GSH-Px u odnosu na krave iz ljetne skupine. Međutim, između 6. i 10. mjeseca laktacije, aktivnost GSH-Px bila je znatno viša u ljetnoj skupini krava (P<0,001). U obje skupine krava aktivnost GSH-Px bila je negativno povezana sa SCC, TBC i EC tijekom laktacije. Nije pronađena korelacija između aktivnosti GSH-Px i sastava mlijeka. Zaključno, na temelju njezinog odnosa s pokazateljima supkliničkog mastitisa, promjenjivost razine GSH-Px u mlijeku mogla bi se koristiti kao dijagnostički alat u praćenju zdravlja vimena. Nadalje, krave oteljene zimi imale su veću aktivnost GSH-Px od onih oteljenih ljeti, posebno tijekom prvih nekoliko mjeseci laktacije. Ovi rezultati upućuju na to da bi aktivnost GSH-Px u mlijeku krava tijekom laktacije mogla biti pod utjecajem sezonskih promjena

Evalution of the relationship between milk glutathione peroxidase activity, milk composition and various parameters of subclinical mastitis under seasonal variations

YAZLIK, Murat Onur/0000-0002-0039-5597WOS: 000411813300003The aims of this study were to evaluate the Glutathione peroxidase (GSH-Px) activity in milk, and various milk parameters [milk fat, milk protein, milk solids non-fat (SNF), somatic cell count (SCC), total bacteria count (TBC), electrical conductivity (EC)] in healthy dairy cows during lactation, and to demonstrate the significant correlations between GSH-Px activity, milk composition, SCC, TBC and EC under seasonal variations. The cows calving in January were assigned into the winter group (n = 30) while the other cows calving in August were assigned into the summer group (n = 30). Milk samples were collected weekly during lactation, and monthly average values of the parameters were determined. Although milk GSH-Px activity was variable during lactation, it was significantly higher in the winter group compared to the summer group of cows during the first five months of lactation (P<0.001). However, between the 6th and 10th months of lactation, GSH-Px activity was significantly higher in the summer group (P<0.001). In both groups of cows, GSH-Px activity was negatively correlated with SCC, TBC and EC during lactation. No correlation was found between GSH-activity and milk composition. In conclusion, the alteration of milk GSH-Px levels could be used as a diagnostic tool for monitoring udder health due to its relationship with the parameters of subclinical mastitis. Furthermore, cows calving in winter had higher GSH-Px activity than those calving in summer, especially during the first few months of lactation. These findings indicate that milk GSH-Px activity in cows during lactation could be influenced by seasonal variations