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Plasma LH (luteinizing hormone), heat symptoms and the quality of corpora lutea in different oestrous sychronisation protocols in Brown-Swiss daily cows

Abstract:

The aim of this study was to evaluate plasma levels of LH (luteinizing hormone), heat symptoms and the quality of the corpora lutea after different synchronisation protocols in Brown-Swiss dairy cows under the objective of a fixed artificial insemination date (IATF). The study was performed within 120 days in 2013. Twenty four heifers, 24 to 32 months of age, weighing 350 to 400 kg were involved in this study. According to the study protocol, 3 groups with 8 cows in each were formed. The results showed that the treatment with Norgestomed-GnRH for synchronisation is most effective in heifers compared to other treatments (c2; P < 0,01). Animals with this treatment reached the highest level in plasma LH (31,42 ng/ml) and all heifers expressed heat symptoms after 24 hours. In addition, 87,5% of the heifers developed good corpora lutea with a diameter of more than 2,5 cm. After such a treatment, all animals became pregnant following artificial insemination.