cjs-202008-0002 ArticleInAPeriodical 2020 Czech Journal of Animal Science 65 8 295-302 ZuborTibor HollóGabriella PósaRoland Nagy-KiszlingerHenrietta VighZsófia HúthBalázs Effect of rectal temperature on efficiency of artificial insemination and embryo transfer technique in dairy cattle during hot season This study aimed to evaluate the effects of rectal temperature (RT) as well as artificial insemination (AI) technique on pregnancy rates in Holstein cows and artificial insemination or embryo transfer (ET) techniques in Holstein heifers during summer. The experiments were conducted on five dairy farms in Hungary, where 1 631 data were examined. The RT was measured immediately before reproductive techniques using a digital thermometer. The effects of animal group and month on RT were analysed. The enhancement of RT until September can be seen in heifers, but the highest RT of cows occurred during July. In line with the enhancement of RT the pregnancy rate decreased in all groups; the lowest (cows) and the highest (heifers) value was observed in July. Moderate to high negative coefficients of correlation were detected between rectal temperature and pregnancy rate for particular groups (r = -0.3 - -0.7). More than 92% of ET, 48% and 16% of inseminated heifers and cows were pregnant up to the category of 39.1 °C of RT, above this it did not change considerably in the inseminated groups. In inseminated animals with RT higher than 39.1 °C significantly higher services per conception could be observed contrary to ET heifers. ET may become a more effective strategy to improve pregnancy success in heifers compared to AI during summer.