Follicular growth after antrum formation is determined by folliclestimulating hormone (FSH). Only two ways are possible for recruited follicles, continuing development or atresia. In gilts, intensive ovarian follicular growth begins between 60 and 100 days of age, and fluctuations of the ovarian morphological status last about 20 days; however, at that time there are no really large follicles. Final follicular development is under luteinising hormone (LH) control; this is why the attainment of puberty is related to an increase in serum oestradiol to a level that causes a preovulatory surge of this gonadotropin. The pool of follicles at the beginning of the oestrous cycle is about 30-40, most of which are small (< 3 mm) and growing. Then, the pool of follicles increases to about 80 in the mid-luteal phase but about 50 of them are small and 30 are medium sized (3-6.9 mm). Some of these follicles are in the growing phase, but some are atretic. Between days 7 and 15 of the oestrous cycle the percentage of atretic follicles fluctuates between 12 and 73%. At that time there are no large (> 7 mm) follicles because of the suppressing effect of progesterone. The number of small follicles declines after luteolysis. From the pool of medium follicles, large follicles are selected under the influence of LH, but about 70% of the medium-sized follicles become atretic. Because of the long-lasting selection process there is a significant heterogeneity in the diameter of large follicles in oestrus. However, the number of follicles correlates with the number of corpora lutea after ovulation. Individual follicular development and the relationship between follicles are still poorly known. The use of ultrasonography may give a closer insight into these phenomena.

No abstract

Purpose -The aim of the study was to assess the impact of the location of farms, the quality of natural conditions and fragmentation of agricultural holdings on the rate of landowners' departure from agricultural activity, including cattle and pig farming.Research method -The study covered six provinces: Dolnośląskie, Małopolskie, Lubelskie, Mazowieckie, Pomorskie, Wielkopolskie. The considerations carried out were conducted in the system of districts for the years 2004-2016.Results -The largest decrease in the number of direct payment beneficiaries in the years 2004-2016 was recorded in the districts located on the outskirts of metropolitan areas. It was observed that in territorial units which obtained a higher evaluation of the quality of agricultural production space the regression in terms of the number of farms involved in animal production was significantly smaller, and the decrease in the number of single area payment beneficiaries was also smaller. In districts with relatively good natural conditions, faster departue from cattle and pig rearing was facilitated by the fragmentation of the area structure of farms.Originality / value / implications / recommendations -So far,the lack of detailed analyses of changes taking place in agriculture in Polish metropolitan areas has been noted, while this issue has been an important field of interest for researchers in the world for several decades. Therefore itmeans that work should be considered innovative. The results of the undertaken considerations constitute a significant contribution to explaining the reasons for the deagrarianisation of rural areas.