Examination of factors that affect the hormones content in raw and commercial cow's milk

[D. Lj. Knežević]

71 str.

veterinarska medicina / veterinary medicine

Istraživanje je obuhvatilo određivanje koncentracije hormona u mleku krava u različitim fazama laktacije, mleku iz laktofriza i maloprodajnom mleku. Uzorci mleka i krvi prikupljeni su 10., 30., 60., 90., 150., 180., 210., 250. i 280 dana laktacije od četrnaest krava holštajn rase i u njima su određivane koncentracije hormona, masti i proteina u mleku i biohemijskih parametara krvi. U iste svrhe uzorkovano je mleko iz laktofriza i nabavljeno je komercijalno mleko sa 1,5% i 3,2% mlečne masti. Koncentracije insulinu-sličnog faktora rasta-1 (IGF-1) u mleku bile su značajno niže 90., 150., 180., 210. i 250. dana i značajno više 10., 30. i 60. dana laktacije poredeći sa laktacionim prosekom (LP). Insulin je imao značajno niže koncentracije u mleku 30., 60. i 90. dana i značajno više koncentracije 210., 250. i 280. dana laktacije poredeći sa LP. Koncentracija slobodnog tiroksina je bila viša 250. dana, dok je nivo slobodnog trijodotironina bio značajno niži 30., 60., 90. i 280. dana i značajno viši 10. i 180. dana u poređenju sa odgovarajućim LP. Nivo kortizola u mleku je bio niži 60. i 280. dana laktacije poredeći sa LP. Koncentracije progesterona određene 10., 30., 60. i 90. dana su bile statistički značajno niže a koncentracije određene 150., 180., 210. i 250. dana značajno više u odnosu na LP. Koncentracije estrogena određene 10., 30., 60., 90. i 150. dana su bile značajno niže a koncentracije 180., 210. i 250. dana značajno više u odnosu na LP. Svi hormoni su imali značajno niže koncentracije u komercijalnom mleku sa 1,5% masti nego u komercijalnom mleku sa 3,2% masti, mleku iz laktofriza i LP. Izuzetak je LP za IGF-1, koji je bio značajno niži nego nivo IGF-1 u komercijalnom mleku sa 1,5% masti, kao i LP za estogen koji se nije značajno razlikovao u odnosu na nivo estrogena u u komercijalnom mleku sa 1,5% masti. Biohemijski parametri krvi su blago fluktuirali tokom laktacije, ali su ostali u referentnom opsegu. Koncentracije hormona u kravljem mleku fluktuiraju tokom laktacije, što daje značaj mleku u kontekstu javnog zdravlja.

The study aimed to determine the concentration of hormones in cow’s milk sampled from different phases of lactation, bulk-tank milk and retail milk. Milk and blood samples were taken from fourteen Holstein cows on the following days in lactation (DIL): 10, 30, 60, 90, 150, 180, 210, 250 and 280 to determine milk hormones, fat and protein content and blood biochemical parameters. For the same purpose, bulk-tank milk was sampled and samples of retail milk with 1.5% and 3.2% fat was purchased. Milk insulin-like growth factor-1 (IGF-1) values were significantly lower at 90, 150, 180, 210 and 250 and significantly higher at 10, 30 and 60 DIL than lactation average (LA). Milk insulin concentrations were significantly lower at 30, 60 and 90 and higher at 210, 250 and 280 DIL than LA. Free thyroxine level in the milk was higher at 250 DIL, while milk free triiodothyronine concentrations were lower at 30, 60, 90 and 280 DIL, and significantly higher at 10 and 180 DIL than respective LA. Milk cortisol levels were lower at 60 and 280 DIL than LA. Milk progesterone concentrations were significantly lower at 10, 30, 60 and 90 and significantly higher at 150, 180, 210 and 250 DIL than lactation average (LA). Milk estrogen concentrations were significantly lower at 10, 30, 60, 90 and 150 and significantly higher at 180, 210 and 250 DIL than lactation average (LA) All measured milk hormones were significantly lower in retail milk with 1.5% fat compared to retail milk with 3.2% fat, bulk-tank milk and LA. An exception was the LA of IGF-1, which was significantly lower than the IGF-1 content in retail milk with 1.5% fat as well as the LA of estrogen, which did not significantly differ compared to the estrogen content in retail milk with 1.5% fat. Blood biochemical parameters fluctuated evenly during lactation and were within the reference range. Hormone concentrations in cow’s milk fluctuate during lactation, giving milk an important role in the context of public health.

krave, hormoni mleka, zdravlje potrošača

milk hormones, consumer health

636.2:637.12(043.3)

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