Good husbandry conditions on farms is of key importance for assuring animal welfare. One of the most important legal documents regulating the rules of maintaining pigs is the Directive 2008/120/EC, which states that group-housed pigs should have access to litter or other materials that provide exploration and occupation. Released in 2016, the Commission Recommendation (EU) 2016/336 on the application of the Council Directive 2008/120/EC characterizes the various categories of materials that may be used to improve animal welfare. According to the document, straw is considered as an optimal material for pig housing, however, materials categorized as suboptimal (e.g., wood bark) and materials of marginal interest (e.g., plastic toys) are often used in practice and scientific research. As such, the aim of this paper is to review and systematize the current state of knowledge on the topic of the impact of environmental enrichment on pig welfare. This article raises mainly issues, such as the effectiveness of the use of various enrichment on the reduction of undesirable behavior—tail biting; aggression; and stereotypies at the pre-weaning, post-weaning, and fattening stage of pig production.

Perception of the environment by farm animals is fundamental for expression of behaviour and of their adaptation to different environmental conditions. From a breeding-environmental perspective, perception becomes increasingly important when a production system negatively impacts on animals such that their normal expression of behaviour is compromised. Therefore, research on the perceptual abilities of farm animals is of crucial importance to understand the animalenvironment relationship. This review is focused on research related to sensory perception of farm animals. It should be stressed that the world of animal senses is very difficult to explore, we have limited knowledge of the complexity of the animal’s ability to perceive and process environmental stimuli.

Weather conditions (temperature, humidity, solar radiation, air pressure, wind strength, wind direction and precipitation) have a significant impact on the behaviour of farm animals. Pigs have developed a wide range of thermoregulatory behaviours that are particular for this species. With increases in temperature the most characteristic behaviour for pigs is decreased activity and increased wallowing in wet surfaces. In addition to this, rooting and wallowing are highly influenced by temperature and humidity. The lack of possibility to express these behaviours leads to development of stereotypies. Interestingly, low temperatures do not increase the use of shelter if not in combination with wind or precipitation. Furthermore, wild pigs build stronger nests in severe conditions. Also, resting behaviour and reproduction may be disturbed by high temperatures. There is a negative impact of foehn wind on boars’ libido and semen parameters.

To ensure the optimal living conditions of farm animals, it is essential to understand how their senses work and the way in which they perceive their environment. Most animals have a different hearing range compared to humans; thus, some aversive sounds may go unnoticed by caretakers. The auditory pathways may act through the nervous system on the cardiovascular, gastrointestinal, endocrine, and immune systems. Therefore, noise may lead to behavioral activation (arousal), pain, and sleep disorders. Sounds on farms may be produced by machines, humans, or animals themselves. It is worth noting that vocalization may be very informative to the breeder as it is an expression of an emotional state. This information can be highly beneficial in maintaining a high level of livestock welfare. Moreover, understanding learning theory, conditioning, and the potential benefits of certain sounds can guide the deliberate use of techniques in farm management to reduce the aversiveness of certain events.

There were two goals of the present experiment, namely (1) to determine and compare the concentrations of basal nutrients and anti-nutrients in the grain of a modern hybrid rye and barley cultivars, and (2) to compare the effectiveness of the rye- and barley-containing diets for pig fattening. Crude protein and starch contents were greater (P < 0.01) in rye (cv. Visello) than in barley (cv. Bryl) but fibre and total lipid concentrations were lower (P < 0.01) in rye grain. Mean concentrations of alkylresorcinols and pentosans, as well as the activity of trypsin inhibitors, were all higher (P < 0.01) in rye grain. In all, 150 PIC gilts were randomly divided into two equinumerous groups; control pigs were fed a diet containing barley as the main cereal ingredient (starter phase (SP), 35% of feed content; grower phase (GP), 40% of feed content; and finisher phase (FP), 65% of feed content), while the experimental group received a diet with rye replacing a proportion of barley (10% during SP, 25% during GP and 50% during FP); the diets for both subsets of animals also contained wheat and soybean meal to obtain a proper level of nutritional value. The average weight gain of the rye-fed gilts (783 ± 183 g/day; mean ± s.d.) was greater (P < 0.05) than that of control animals (747 ± 218 g/day). This difference in weight gain was due mainly to an increase in daily feed intake (2.35 ± 0.21 and 2.15 ± 0.19 kg/day in the experimental and control groups, respectively; P < 0.01) recorded during the grower and finisher phase. Carcasses from both groups exhibited the same lean meat content; however, the percentage of carcasses in the higher classes according to the EUROP quality scale tended to be greater in the experimental group, which resulted in a higher (P < 0.05) carcass value than for barley-fed controls. The present results indicated that a modern rye cv. Visello is a safe and cost-effective feed for growing pigs, and yields significantly better outcomes than commonly used barley-containing diets in terms of carcass quality and price.

Follicular growth after antrum formation is determined by follicle-stimulating 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.