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    Factors affecting expression of estrus in dairy cows with high milk yields
    (Med. Weter., 2018) Gavelis, Aurimas; Žilaitis, Vytuolis; Arunas, Juozaitis; Vida, Juozaitiene; Giedrius, Palubinskas; Yılmaz, Ayhan
    The objectives of this study were to define the effect of the milk progesterone (P4) concentration on estrus expression in dairy cows with high milk yield and to identify the effect of milk yield and parity on the milk P4 concentration and cow’s pregnancy after artificial insemination (AI). In this study, 48 clinically healthy cows without reproduction disorders, on day 90-100 after calving were used. At the beginning of estrus and 12 hours after the beginning of estrus, the milk P4 concentration in dairy cows with high milk yield (group 3) was higher than in group 2 (33.66; 22.36%) and in group 1 (51.60; 65.26%) (P < 0.001). The milk P4 concentration in the ? 3 lactation cows was higher than the second (13.45%; P > 0.05) and the first (28.28%; P < 0.01) lactation ones (28.28%; P < 0.01). The milk P4 concentration at the beginning of estrus and 12 hours after the beginning of estrus in pregnant and non-pregnant cows was 2.58 and 3.32; 4.20 and 5.00 ng/ml, respectively (P < 0.001). As a result, it was concluded that high progesterone concentration affected the expression of estrus and pregnancy results in dairy cows, and the measuring of progesterone concentration in milk can be used as a non-invasive method to provide detailed information about fertility in high milk yield cows.
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    The relationship between milk progesterone and milk traits during estrus in dairy cows
    (Indian Journal Animal Research, 2018) Gavelis, Aurimas; Žilaitis, Vytuolis; Juozaitienë, Vida; Urbonavičius, G; Yılmaz, Ayhan
    The aim of this study was to evaluate relationship between milk progesterone concentration (P4) and milk traits at the start of estrus time and 12h after start of the estrus in dairy cows. The 96 milk samples of 48 Lithuanian dairy cows without reproduction disorders and 90–100 days after calving were evaluated. Cows were classified into two groups based on milk yield per day: <30 kg (n=20) and ?30 kg (n=28). Data were categorized by milk fat and protein content at the start estrus and 12h after start of estrus to evaluate relationship between P4 and milk traits examined. P4 at estrus time in dairy cows was significantly positively correlated with milk yield (P<0.001), whereas it was negatively correlated with milk protein (P<0.05-P<0.01) and fat at 12h after start of estrus. Dairy cows with F/P from 1.0 to 1.5 had the lowest P4 in milk. Results of the pregnancy in dairy cows were related with lower P4 and milk yield level (P<0.001), higher milk fat (P<0.05) and milk protein content (P<0.001). These cows had 1.90 times lower prevalence of the signs of subclinical ketosis (P<0.05) at estrus time when compared with non-pregnant cows. As a result, it was clearly demonstrated that P4 in dairy cows can help to evaluate and improve the reproductive properties of cows.