Genetic selection for body size during domestication of animal species can inadvertently affect a number of physiological and behavioural traits. The pace-of-life syndrome (POLS) hypothesis predicts that domestication in an artificial environment lacking predators and providing abundant resources prefers proactive individuals with strong feeding motivation, high levels of aggression and risk taking, with low hypothalamus–pituitary–adrenal (HPA) axis responsiveness. In the present experiment we weaned fingerling pike-perch from live feed and habituated them to formulated feed. We recorded the number of weeks needed for the fish to accept pellets, their body length at the age of 100 days, their boldness in a novel object test and their HPI axis responsiveness. Individuals accepting the artificial feed within the first week grew larger than fish habituating later; therefore early weaners would be kept and bred in routine aquaculture procedures. Contrary to predictions of POLS hypothesis, fish weaning earlier and thus growing faster were less bold and had higher HPI axis responsiveness than fish accepting the pellets later or never. As live feed is preferred to artificial pellets, less competitive individuals may switch to pellets earlier. Inadvertent selection for stress sensitive fish may have an effect on production in aquaculture as well as on natural population after intensive restocking.

The pikeperch (Sander luciopercaL.) possesses great potential for diversifying European aquaculture. However, studies on the genetic risk of stocking natural waters with farmed individuals of this species have been limited. Even the effect of pond culture on the genetic composition of stocks with natural-origin has not yet been determined. Our study aimed to compare the genetic variability of a wild living pikeperch population, a pond cultured broodstock (originating from the wild population) and its offspring generation. We also aimed to detect the potential signs of selection using three different methods. By analyzing the molecular data with 14 microsatellite markers, we illustrated that the impact of pond culture on the genetic diversity of fish stocks is similar to hatchery rearing due to its diversity reducing effect caused by using lower effective population sizes. Although the heterozygosity was similar in all populations (H_o= 0.68–0.71), the average number of alleles and allelic richness were significantly lower in the pond cultured stocks (NA = 7.5 and 6; AR = 7.5 and 5.9) compared to the wild population (NA = 11.00, AR = 10.47). Despite the semi-natural conditions of the present study, we detected changing selection pressure in one of the 14 microsatellite markers.

Once a day, nursing and absentee mothering make the wild rabbit (Oryctolagus cuniculus) an ideal model animal for measuring differences in maternal behavior. Behavioral events and their hormonal regulation leading to parturition are well documented; however, the genetic background behind individual differences in this complex process is unknown. Decreased progesterone hormone level and the reduction of progesterone receptor activity are crucial to initiating the collection of nest material. The progesterone receptor gene is a likely candidate affecting nest-building behavior. In addition to several known point mutations in the progesterone receptor gene of the European wild rabbit, we have found a new mutation in the promoter region of the gene at 2682 T > C. Although this new single nucleotide polymorphism (SNP) was not involved in the formation of the nest-building behavior, an SNP (2464G > A) already described in the promoter region showed an association with individual differences in the initiation of hay carrying. The distribution of this SNP delivered an opposite result compared to domestic rabbits. Genotype (GG) with high uterine capacity was most frequent; the hereditary value of the trait was h² = 0.10. Thus, progesterone receptor gene polymorphism may manifest in individual differences affecting breeding success in this species.

The production of pikeperch in a recirculation aquaculture system (RAS) is of growing importance. However, the use of combined technologies may also be justified, especially in countries with larger pond areas. However, this requires the most effective adaptation of pellet-consuming individuals to pond conditions. Foraging training, a form of environmental enrichment to compensate for the poor environment in hatchery rearing, can play a major role in this. The aim of our study was to investigate the prey size preference already observed in wild pikeperch, during prey capture by intensively reared naive individuals. We investigated predation success, latency, number of attempts during the process, and size distribution, in a total of 152 foraging trials of 38 pikeperch fingerlings (mean TL = 90.65 mm) at three different prey sizes (predator–prey length ratio (PPR): 0.11, 0.22, 0.33). Although predation on medium–large prey was more successful overall, it was achieved in more attempts and with greater latency. Small prey was captured with the fewest attempts. These results suggest that when calculating prey size in the foraging training of pikeperch, it is recommended to use a 0.11–0.22 PPR less than the optimal PPR described for wild individuals.

In ovo administration of DL-methionine and post-hatch Hydrogel® supplements were tested to examine the impact of early feeding on performance and immune-related traits in a commercial broiler stock. One thousand one hundred and twenty Ross 308 eggs were incubated and assigned to seven treatment groups: intact (no in ovo administration) and immediate feed access (C1), in ovo saline treatment and immediate feed access (C2), intact and delayed feeding (ID), in ovo saline treatment and delayed feeding (IoS), in ovo DL-Methionine treatment and delayed feeding (IoM), intact and delayed access to feed, but immediate access to commercial Hydrogel® without (Hyd) or with 5mg/kg (HydM) DL-methionine post-hatch. The results showed, that the in-ovo methionine may have positive effects on the weight gain of the birds (p < 0.001) compared to the commercial Hydrogel® however, it cannot compete with the immediate feeding. The number of heterophils decreased significantly (p < 0.001) by day 21 in ID and IoS compared to the immediately fed control (C1). The number of lymphocytes, monocytes, and eosinophils, increased in treatments supplemented with methionine (p < 0.05) (IoM,HydM) indicating enhanced immune protection. There were no differences in the total antioxidant capacity (FRAP) and malonaldehyde concentration (MDA) (p = 0.07) in the examined groups. The Cytochrome P450 H1 (CYP2H1) gene was downregulated in all treatment groups (on days 21 and 35) indicating a slower metabolism, particularly in the ID group compared to C1 and C2 (p < 0.001). The HydM treatment could upregulate the IL2 expression as the immediate feeding, while only IoM treatment resulted in significant downregulation by day 35 (p < 0.001). IL6 was upregulated in all treatment groups (p < 0.001) except for HydM, where the gene expression did not differ from the housekeeping gene. Early administration of dietary methionine has a positive effect on performance and the immune system, however, none of the early feeding methods can compete with immediate feed access. The possible positive effects of early nutrition and its epigenetic impact should be examined in further studies.

One of the problematic points of rabbit breeding is that the nutritional requirements of the kits are not fully satisfied by the does’ milk production from the third week of lactation onwards. The prolactin receptor gene has a significant effect on reproductive processes, and its polymorphisms have been associated with milk production in several species (cattle, goats, sheep, and buffalo). The European wild rabbit (Oryctolagus cuniculus), has a more diverse genetic background compared to domesticated lines. In the course of our study, sequencing of the 1210 bp long segment of the PRLR gene promoter region was accomplished. We detected four point mutations (SNP1-407G > A, SNP2-496G > C, SNP3-926T> and SNP4-973A > C) and one microsatellite at position 574. In our population, the four SNPs were segregated into four genotypes: AACCCCCC, GGGGTTAA, AAGGTTAC, and GGGGTCAC. Our results show that the genotype in the homozygous form is associated with higher milk production (1564.7 ± 444.7 g) compared to the other three genotypes (AACCCCCC 1399.1 ± 326.8 g; GTGACCTT 1403.8 ± 517.1 g; GGGGTCAC 1220.0 ± 666.2 g), and the short microsatellite repeat (167 bp) also coincides with significantly higher milk production (1623.8 ± 525.1 g). These results make the marker-assisted selection possible also for domesticated lines.