Insemination Behaviour Behaviour in Pre-oestrus: In pre-oestrus, the animal starts to become agitated (flehmen response, chin resting). Animals coming into oestrus often hold their tails to the side, especially when sniffed by other animals. It is still too early to inseminate, but you need to observe closely! Behaviour in Oestrus: At the start of oestrus, there can be a lot of agitation around the cow coming into heat. This is especially obvious at pasture. In mid-oestrus, the cow tolerates other cows’ attempts to mount her. She shows the standing reflex. It is still too early to inseminate! But the cow can be reported to the inseminator at this stage. In the barn, animals in oestrus can sometimes be identified by their fixed gaze, pricked ears and arched back. Behaviour in Post-oestrus: Now is the ideal time to inseminate! The animal becomes calmer again and no longer tolerates mounting by other animals. But if there is any bleeding it is too late to inseminate! Behaviour in Inter-oestrus/Dioestrus: During inter-oestrus, the animals’ behaviour is unremarkable. There may be two or three periods of agitation lasting a few hours. There is no point in inseminating at this stage! Ovary Ovary in Pre-oestrus The yellow body regresses. The dominant follicle has a diameter of over 1 cm. The follicle is smooth and rounded (“like a watch glass”). Ovary in Oestrus The follicle grows quickly and is rounded. It may still be possible to feel the yellow body from the previous oestrus. The follicle reaches a diameter of around 1.5 to 2 cm and becomes softer. The follicle has now reached its maximum size. Shortly before it bursts, it becomes soft. Ovary in Post-oestrus At the start of post-oestrus, the follicle bursts. The egg is collected by the funnel-shaped end of the oviduct. Fertilisation by the semen takes place in the oviduct. Ovary in Inter-oestrus The yellow body is often shaped like a champagne cork. During a cycle, one or two follicles may form on the ovary and then regress again. The yellow body does not regress until prostaglandin is produced by the non-pregnant uterus. Uterus and vagina Uterus and vagina in Pre-oestrus Tension builds in the muscles of the uterus. The cervix starts to open. The vaginal mucosae become moist and red. Uterus and vagina in Oestrus The muscles of the uterus contract to the maximum during oestrus. This is why the uterus is small and firm. The vaginal mucosae appear pale pink and moist and the cervix may be clearly open. There is a clear, stringy mucous discharge from the vagina. Uterus and vagina in Post-oestrus The muscles of the uterus relax. Bleeding is a useful indicator and can be recorded on the oestrus calendar. The swelling of the vulva subsides. Uterus and vagina in Inter-oestrus/Dioestrus The muscles of the uterus are loose and relaxed. The cervix is tightly closed and the vaginal mucosae are pale and less moist. The vulva is wrinkled. Hormones Hormones in Pre-oestrus Hormones produced by the hypothalamus (GnRH) and the pituitary gland (FSH) are released into the bloodstream. Follicle-stimulating hormone (FSH) triggers the final maturation of the dominant follicle. The dominant follicle produces the oestrus hormone (oestrogen). Hormones in Oestrus The oestrus hormone is produced by the follicle. The oestrus hormone is responsible for the cow’s typical behaviour during oestrus and the visible changes in the genitals. The rise in luteinising hormone (LH) leads to ovulation at the end of the main phase of oestrus or in early post-oestrus. Hormones in Post-oestrus Luteinising hormone triggers ovulation and the forming of yellow body tissue. Production of the pregnancy hormone begins. The level of oestrus hormone is low again. Hormones in Inter-oestrus/Dioestrus During the cycle, the yellow body produces the pregnancy hormone (progesterone) for around 14 days. If pregnancy occurs, the uterus does not produce prostaglandin F2 alpha (thanks to the signal from the embryo around day 16 of the cycle) and the yellow body persists. Without fertilisation, the uterus produces prostaglandin F2 alpha, the yellow body is reabsorbed and a new cycle begins. Instruction manual Pre-oestrus Oestrus Post-oestrus Inter-oestrus/Dioestrus