Early experiences matter: a review of the effects of prenatal environment on offspring characteristics in poultry

Effects of inclusion of the blend of essential oils, organic acids, curcumin, tannins, vitamin E, and zinc in the maternal diet, and of incubation temperature on early and late development of quail

The maternal diet and egg incubation temperature are some of the factors that can influence the embryonic development and performance of the newly chicks at 15 d of age. This study evaluated the effects of adding a blend of organic acids, essential oils, curcumin, tannins, vitamin E, and zinc microencapsulated in to the diet of female quails (Coturnix coturnix japonica) on their productive, reproductive performance and redox parameters of their eggs and the interaction of maternal diet × incubation temperature on embryo (E16 and E18) and chicks development. At 98 d of age, 64 female quails with a mean body weight of 150 g ± 0.5 were distributed into two treatments: a Basal diet or a diet supplemented with blend (Sannimix). The eggs from each female were incubated at 37.5°C (Control) and 38.5°C (High Temperature) throughout the incubation period. After hatching, chicks were distributed in a 2 (maternal diet) × 2 (incubation temperature) factorial design. Female quails supplemented with Sannimix showed better productive and reproductive performance and produced higher-quality embryos. Their offspring had greater weight at hatch and at 15 d of age. The eggs and offspring of supplemented with Sannimix female quails showed better oxidative stability. At E16 and E18, High Temperature increased yolk sac utilization and gene expression of the growth hormone receptor (GHR). At E16, embryos from supplemented with Sannimix female quail had higher expression of insulin-like growth factor type I (IGFI) and heat shock protein 70 kDa genes. At 15 d of age, highest expression of the GHR and IGFI genes was observed in chicks from female quails fed the Sannimix diet, regardless of incubation temperature. Regarding the maternal diet × incubation temperature an improved result was observed for chicks from female quails fed with Sannimix even when eggs are exposed to High Temperature during the incubation. The supplementation of quail diets with blend Sannimix improves productive and reproductive performance, egg quality and their embryos, as well as their offspring quality.

Prenatal auditory stimulation and impacts on physiological response to feed restriction in broiler chickens at market age

Feed restriction could induce physiological stress in broiler chickens, leading to welfare issues. Prenatal stimulation could improve stress-coping mechanisms in poultry. The present study aimed to elucidate the effects of subjecting developing embryos to auditory stimulation on physiological stress response to feed restriction in broiler chickens at market age. A total of 423 hatching eggs of Cobb 500 (Gallus domesticus) were subjected to the following auditory treatments: 1) no additional sound treatment other than the background sound of the incubator's compressors at 40 dB (CONTROL), 2) exposure to pre-recorded traffic noise at 90 dB (NOISE), and 3) exposure to Mozart's Sonata for Two Pianos in D Major, K 488 at 90 dB) (MUSIC). The NOISE and MUSIC treatments were for 20 min/h for 24 h (a total of 8 h/d), starting from embryonic days (ED) 12 to hatching. On d 42, an equal number of birds from each prenatal auditory stimulation (PAS) group were subjected to either ad libitum feeding (AL) or 30-h of feed restriction (FR) in a completely randomised design. The FR chickens exhibited significantly higher serum levels of corticosterone (CORT), and heat shock protein (HSP) 70 compared to those of AL. Prenatal auditory stimulation, particularly NOISE, led to lower serum levels of CORT and alpha-1-acid glycoprotein (AGP) levels compared to the CONTROL group. Additionally, NOISE significantly increased brain mRNA glucocorticoid receptor and HSP70 gene expression. The cecal population of E. coli and Lactobacillus spp. was not significantly affected by prenatal auditory stimulation. In conclusion, our findings suggest that prenatal auditory stimulation, particularly NOISE, positively impacts broiler chickens' ability to cope with feed restriction.

The effect of hydroxy-selenomethionine on the productive and reproductive performance of old broiler breeders

BACKGROUND

Selenium (Se) is a rare essential element that plays a vital role in the health and performance of animals. By interfering in the production of antioxidant enzymes such as glutathione peroxidase, thioredoxin reductase and methionine sulfoxide, Se plays a role in reducing the effects of oxidative stress and animal performance.

OBJECTIVES

This study aimed to investigate the effect of hydroxy-selenomethionine (OH-SeMet) in the diet of broiler breeder and old broiler breeder roosters on productive performance, reproduction and sperm quality parameters.

METHODS

For this purpose, 260 broiler breeders of the Ross 308 strain were used in a completely randomized design with four treatments and five replications (13 hens and one rooster in each replication). Experimental treatments included: (1) a basal diet without OH-SeMet (T1:control), (2) a broiler breeder diet without OH-SeMet and a rooster diet containing 0.1 mg/kg OH-SeMet (T2), (3) broiler breeder diet containing 0.1 mg/kg OH-SeMet and rooster diet without OH-SeMet (T3) and (4) broiler breeder and rooster diet contained 0.1 mg/kg OH-SeMet (T4).

RESULTS

The results showed that T3 and T4 treatments improved egg production, egg weight, egg mass and feed conversion ratio (FCR) compared to the control treatment (p < 0.05). The fertility and hatchability percentages of T4 and T2 treatments increased compared to T1 and T3 treatments (p < 0.05). The rate of embryonic losses in T1 was higher than in other treatments. However, grade one chickens were higher in T4 than in other treatments (p < 0.05). Total motility and viability of sperms were significantly higher in T2 and T4 treatments than in T1 and T3 treatments. The sperm abnormality percentage and sperm MDA concentration decreased in T2 and T4 treatments.

CONCLUSIONS

Therefore, using OH-SeMet may be a practical approach to help old broiler breeders' production and reproduction performance.

Making the most of life: environmental choice during rearing enhances the ability of laying hens to take opportunities

Introduction

The potential of aviary housing for improving laying hen (Gallus gallus domesticus) welfare will be constrained if rearing conditions limit the hens' behavioral ability to take opportunities. Incorporating theories on developmental plasticity and animal agency, this study aimed to determine: (1) whether a choice of litter and perch types during rearing would promote long-lasting changes in use of novel locations and resources, and (2) the influence of timing of choice provision.

Methods

Laying hen chicks were assigned to either a "Single-choice" (one litter and perch type) or "Multi-choice" environment (four litter and perch types) during "Early" (day 1-week 4) and "Late" rearing (week 5-15). The environments were switched in half of the 16 pens in week 5, resulting in a 2 × 2 factorial design with four choice environment by period combinations. The allocation of perch and litter space was the same across all treatment combinations. In week 16, all groups were moved to standard aviary laying pens (Laying period, week 16-27).

Results

When first moved to the laying pens, hens with Multi-choice in either or both rearing periods were quicker to spread out in their pen than hens with Single-choice throughout rearing. Multi-choice in Early rearing also reduced the latency to use novel elevated structures (perches and nests) in the laying pens. Multi-choice during Late rearing increased success in finding and consuming hidden mealworms (tested in weeks 9-17) and increased the proportion of eggs laid on elevated nesting trays. Numerically, hens switched from Multi-choice to Single-choice in week 5 used the outdoor range less than hens switched from Single-choice to Multi-choice.

Discussion

These results support the hypothesis that offering multiple resource choices during rearing improves hens' ability to make the most of new opportunities by being more proactive in exploring and exploiting newly available resources. In different opportunity challenges, hens showed positive outcomes in response to choice during Early, Late or both stages of rearing, suggesting that best results can be obtained by offering environmental choice throughout rearing.

Effects of the temperature during embryonic development on adult reproduction and the phenotype of the second generation in zebra finches

Across taxa, the temperature experienced by individuals early in life can have large effects on their development. However, comparatively little is known about whether the effects of this thermal developmental environment can be long-lasting or transgenerational. In birds, one important aspect of the developmental environment is incubation and, in general, eggs incubated at low temperatures produce offspring with smaller morphology, suboptimal physiology, and even lower long-term survival. Yet, little is known about whether incubation temperature may affect avian reproduction in adulthood, and nothing is known about whether the effects of avian incubation temperature may be transgenerational. To investigate this, we incubated zebra finch (Taeniopygia guttata) eggs at two different temperatures: 37.5 °C ('control') and 36.3 °C ('low'), raised nestlings until adulthood, and allowed same-temperature treatment pairs to reproduce. We found that F1 individuals incubated at the low temperature had shorter beaks at the start of reproduction than those incubated at the control temperature. Further, compared to those from control parents, F2 offspring from parents incubated at the low temperature had lighter body masses at 5 days-old and had shorter beaks at 30 days-old. However, we found little evidence that incubation temperature affected other aspects of reproduction, with no effect on latency to lay, clutch size, egg mass, incubation period, hatching success/asynchrony, fledging, or the number of offspring that ultimately survived until independence. Overall, we found some evidence that a difference in the early thermal developmental environment can have lasting morphological effects into the next generation. However, future work is needed to determine whether the incubation temperature that birds experience as embryos may influence parental care behaviors or lifetime reproductive success.

Proteomic changes associated with maternal dietary low ω6:ω3 ratio in piglets supplemented with seaweed Part II: Ileum proteomes

This study evaluates how long-term dietary low ω6:ω3 ratio in sows and offspring's seaweed (SW) intake affects piglet intestinal function and growth through modifying ileum proteome. Sows were assigned to either control diet (CR, ω6:ω3 ratio = 13:1) or treatment diet (LR, ω6:ω3 = 4:1) during gestation and lactation (n = 8 each). The male weaned offspring were received a basal diet with or without SW powder supplementation (4 g/kg) for 21 days, denoted as SW and CT groups, respectively. In total, four groups of weaned piglets were formed following maternal and offspring's diets combination, represented by CRCT, CRSW, LRCT, and LRSW (n = 10 each). Piglet ileum tissue was collected on day 22 post-weaning and analysed using TMT-based quantitative proteomics. The differentially abundant proteins (n = 300) showed the influence of maternal LR diet on protein synthesis, cell proliferation, and cell cycle regulation. In contrast, the SW diet lowered the inflammation severity and promoted ileal tissue development in CRSW piglets but reduced the fat absorption capacity in LRSW piglets. These results uncovered the mechanism behind the anti-inflammation and intestinal-boosting effects of maternal LR diet in piglets supplemented with SW.

Effects of maternal methionine supplementation on the response of Japanese quail (Coturnix coturnix japonica) chicks to heat stress

This study investigated the hypothesis that methionine supplementation of Japanese quail (Coturnix coturnix japonica) hens can reduce the effects of oxidative stress and improve the performance of the offspring exposed to heat stress during growth. For that, the quail hens were fed with three diets related to the methionine supplementation: methionine-deficient diet (Md); diet supplemented with the recommended methionine level (Met1); and diet supplemented with methionine above the recommended level (Met2). Their chicks were identified, weighed, and housed according to the maternal diet group from 1 to 14 d of age. On 15 d of age, chicks were weighed and divided into two groups: thermoneutral ambient (constant temperature of 23 °C) and intermittent heat stress ambient (daily exposure to 34 °C for 6 h). Methionine-supplemented (Met1 and Met2) hens had higher egg production, better feed conversion ratio, higher hatchability of total and fertile eggs, and offspring with higher body weight. Supplemented (Met1 and Met2) hens showed greater expression of glutathione synthase (GSS) and methionine sulfoxide reductase A (MSRA) genes, greater total antioxidant capacity, and lower lipid peroxidation in the liver. The offspring of hens fed the Met2 diet had lower death rate (1 to 14 d), higher weight on 15 d of age, weight gain, and better feed conversion ratio from 1 to 14 d of age. Among chicks reared under heat stress, the progeny of methionine-supplemented hens had higher weight on 35 d, weight gain, expression of GSS, MSRA, and thermal shock protein 70 (HSP70) genes, and total antioxidant capacity in the liver, as well as lower heterophil/lymphocyte ratio. Positive correlations between expression of glutathione peroxidase 7 (GPX7) and MSRA genes in hens and offspring were observed. Our results show that maternal methionine supplementation contributes to offspring development and performance in early stages and that, under conditions of heat stress during growth, chicks from methionine-supplemented hens respond better to hot environmental conditions than chicks from nonsupplemented hens. Supplementation of quail hens diets with methionine promoted activation of different metabolic pathways in offspring subjected to stress conditions.

Warmer incubation temperatures and later lay-orders lead to shorter telomere lengths in wood duck (Aix sponsa) ducklings

The environment that animals experience during development shapes phenotypic expression. In birds, two important aspects of the early-developmental environment are lay-order sequence and incubation. Later-laid eggs tend to produce weaker offspring, sometimes with compensatory mechanisms to accelerate their growth rate to catch-up to their siblings. Further, small decreases in incubation temperature slow down embryonic growth rates and lead to wide-ranging negative effects on many posthatch traits. Recently, telomeres, noncoding DNA sequences at the end of chromosomes, have been recognized as a potential proxy for fitness because longer telomeres are positively related to lifespan and individual quality in many animals, including birds. Although telomeres appear to be mechanistically linked to growth rate, little is known about how incubation temperature and lay-order may influence telomere length. We incubated wood duck (Aix sponsa) eggs at two ecologically-relevant temperatures (34.9°C and 36.2°C) and measured telomere length at hatch and 1 week after. We found that ducklings incubated at the lower temperature had longer telomeres than those incubated at the higher temperature both at hatch and 1 week later. Further, we found that later-laid eggs produced ducklings with shorter telomeres than those laid early in the lay-sequence, although lay-order was not related to embryonic developmental rate. This study contributes to our broader understanding of how parental effects can affect telomere length early in life. More work is needed to determine if these effects on telomere length persist until adulthood, and if they are associated with effects on fitness in this precocial species.

Maternal dietary methionine restriction alters hepatic expression of one-carbon metabolism and epigenetic mechanism genes in the ducklings

BACKGROUND

Embryonic and fetal development is very susceptible to the availability of nutrients that can interfere with the setting of epigenomes, thus modifying the main metabolic pathways and impacting the health and phenotypes of the future individual. We have previously reported that a 38% reduction of the methyl donor methionine in the diet of 30 female ducks reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal methionine-restricted diet also altered plasmatic parameters in 30 of their ducklings when compared to that of 30 ducklings from the control group. Thus, their plasma glucose and triglyceride concentrations were higher while their free fatty acid level and alanine transaminase activity were decreased. Moreover, the hepatic transcript level of 16 genes involved in pathways related to energy metabolism was significantly different between the two groups of ducklings. In the present work, we continued studying the liver of these newly hatched ducklings to explore the impact of the maternal dietary methionine restriction on the hepatic transcript level of 70 genes mostly involved in one-carbon metabolism and epigenetic mechanisms.

RESULTS

Among the 12 genes (SHMT1, GART, ATIC, FTCD, MSRA, CBS, CTH, AHCYL1, HSBP1, DNMT3, HDAC9 and EZH2) identified as differentially expressed between the two maternal diet groups (p-value < 0.05), 3 of them were involved in epigenetic mechanisms. Ten other studied genes (MTR, GLRX, MTHFR, AHCY, ADK, PRDM2, EEF1A1, ESR1, PLAGL1, and WNT11) tended to be differently expressed (0.05 < p-value < 0.10). Moreover, the maternal dietary methionine restriction altered the number and nature of correlations between expression levels of differential genes for one-carbon metabolism and epigenetic mechanisms, expression levels of differential genes for energy metabolism, and phenotypic traits of ducklings.

CONCLUSION

This avian model showed that the maternal dietary methionine restriction impacted both the mRNA abundance of 22 genes involved in one-carbon metabolism or epigenetic mechanisms and the mRNA abundance of 16 genes involved in energy metabolism in the liver of the newly hatched offspring, in line with the previously observed changes in their phenotypic traits.

Prenatal auditory stimulation induces physiological stress responses in developing embryos and newly hatched chicks

Prenatal stress may evoke considerable physiological consequences on the developing poultry embryos and neonates. The present study aimed to determine prenatal auditory stimulation effects on serum levels of ceruloplasmin (CPN), alpha-1-acid glycoprotein (AGP), corticosterone (CORT), and heat shock protein 70 (Hsp70) regulations in developing chicken embryos and newly hatched chicks. Hatching eggs were subjected to the following auditory treatments; 1) control (no additional sound treatment other than the background sound of the incubator's compressors at 40 dB), 2) noise exposure (eggs were exposed to pre-recorded traffic noise at 90 dB) (NOISE), and 3) music exposure (eggs were exposed to Mozart's Sonata for Two Pianos in D Major, K 488 at 90 dB) (MUSIC). The NOISE and MUSIC treatments were for 20 min/h for 24 h (a total of 8 h/d), starting from embryonic days (ED) 12 to hatching. The MUSIC (1.37 ± 0.1 ng/mL) and NOISE (1.49 ± 0.2 ng/mL) treatments significantly elevated CPN at ED 15 compared to the Control (0.82 ± 0.04 ng/mL) group and post-hatch day 1 (Control, 1.86 ± 0.2 ng/mL; MUSIC, 2.84 ± 0.4 ng/mL; NOISE, 3.04 ± 0.3 ng/mL), AGP at ED 15 (Control, 39.1 ± 7.1 mg/mL; MUSIC, 85.5 ± 12.9 mg/mL; NOISE, 85.4 ± 15.1 mg/mL) and post-hatch day 1 (Control, 20.4 ± 2.2 mg/mL; MUSIC, 30.5 ± 4.7 mg/mL; NOISE, 30.3 ± 1.4 mg/mL). CORT significantly increased at ED 15 in both MUSIC (9.024 ± 1.4 ng/mL) and NOISE (12.15 ± 1.6 ng/mL) compared to the Control (4.39 ± 0.7 ng/mL) group. On the other hand, MUSIC exposed embryos had significantly higher Hsp70 expression than their Control and NOISE counterparts at ED 18 (Control, 12.9 ± 1.2 ng/mL; MUSIC, 129.6 ± 26.4 ng/mL; NOISE, 13.3 ± 2.3 ng/mL) and post-hatch day 1 (Control, 15.2 ± 1.7 ng/mL; MUSIC, 195.5 ± 68.5 ng/mL; NOISE, 13.2 ± 2.7 ng/mL). In conclusion, developing chicken embryos respond to auditory stimulation by altering CPN, AGP, CORT, and Hsp70. The alterations of these analytes could be important in developing embryos and newly hatched chicks to cope with stress attributed to auditory stimulation.

Arsenic contribution of poultry manure towards soils and food plants contamination and associated cancer risk in Khyber Pakhtunkhwa, Pakistan

Exposure to high level of arsenic (As) through the ingestion of contaminated soil, dust and food plants can pose health risk to humans. This study investigates the total arsenic (As), arsenobetaine (AsB), monomethylarsenate (MMA), dimethylarsenate (DMA), arsenite (As³⁺) and arsenate (As⁵⁺) concentrations in poultry feed, manure, agricultural soils and food plants collected from Khyber Pakhtunkhwa Province, Pakistan. The total mean As concentrations in the edible parts of food plants ranged from 0.096 mg kg^-1 to 1.25 mg kg^-1 with percentile (P) values (P25-0.039, P50-0.0765, P75-0.165 1 mg kg^-1 to P25-0.95, P50-1.23, P75-1.6 1 mg kg^-1) and exceeded the food safety limit (0.1 mg kg^-1) of Food & Agriculture Organization (FAO) and World Health Organization (WHO) in all plant species except Pisum sativum (pea) and Mentha arvensis (mint). The risk to human health was assessed through the average daily intake (ADI), hazards quotient (HQ), health risk index (HRI) and lifetime cancer risk (LTCR). The highest average daily intake of As via the ingestion of Malva neglecta (mallow, a leafy plant) was observed for adults and children. The ADI for adults and children (2.36 × 10^-4 mg kg^-1 day^-1 and 6.33 × 10^-4 mg kg^-1 day^-1) was about 13% and 5%, respectively, of the Bench Mark Dose Limit (BMDL_0.5) of 3.00 × 10^-3 mg kg^-1 day^-1 set by WHO. The HRI was 3 times more in the children (2.1) than the adults (0.79), posing non-cancer health risks (health risk index > 1) for children. The LTCR values were slightly higher (1.53 × 10^-4) relative to USEPA and WHO limits (1 × 10^-6 to 1 × 10^-4) for children whereas a minimal cancer risk was observed for adults via consumption of selected food plants. The results showed that poultry manure can contaminate food plants that may lead to cancer and non-cancer risks in agricultural areas, Pakistan. Thus, it is important to minimize As concentration in poultry feed to safeguard human health and environment from adverse effects.

Increasing Environmental Complexity by Providing Different Types of Litter and Perches during Early Rearing Boosts Coping Abilities in Domestic Fowl Chicks

Simple Summary

The benefits of rearing chicks in complex environments rather than barren environments are well established. However, the typical rearing environments for modern laying hens are still considerably more barren than the complex forest habitat of their ancestors. This small-scale experimental study investigated whether giving chicks of white Bovans Robust the possibility to express choices between different variants of the same resource could result in them being better able to cope with challenges, as well as being better able to make the most of new opportunities. We found that chicks with access to different types of litter and perches were less fearful, less chronically stressed, and were better prepared to cope with pathogenic challenges. Furthermore, they were more successful in a repeated opportunity test, implying an improved learning ability. Overall, the results suggest that rearing laying hen chicks in an environment with access to variation in relevant resources could be a simple and feasible way to increase complexity under commercial conditions. This input could result in them being more resistant to infection and better able to adapt to novel situations later in life.

Abstract

Early experience of a complex environment can improve biologically relevant traits related to coping abilities. However, the mechanisms underlying these positive effects have not been well explored. We hypothesized that giving chicks possibilities to express choices within relevant resources could be an important part of the mechanism, as well as a novel way to increase environmental complexity. In a balanced design, laying hen hatchlings of the white hybrid Bovans Robust were reared in a “single-choice” environment (single litter and perch type) or a “multi-choice” environment (four different litter and perch types). Immunological and behavioral indicators of chicks’ coping abilities were explored in this experimental study at three weeks of age. Chicks from “multi-choice” environments had shorter durations of tonic immobility, lower heterophil/lymphocyte ratios, higher natural antibody concentrations, and were more successful in gaining novel food rewards in a repeated opportunity test. These results imply that chicks having access to variation within resource types were less fearful, experienced less chronic stress, would be more able to cope with pathogenic challenges, and potentially had an improved learning ability. To conclude, the more complex environment, achieved by increasing chicks’ possibilities to choose, seemed to make chicks better prepared for potential challenges, boosting their adaptive capacities and their ability to make the most of opportunities.

Maternal dietary methionine restriction alters the expression of energy metabolism genes in the duckling liver

Background

In mammals, the nutritional status experienced during embryonic development shapes key metabolic pathways and influences the health and phenotype of the future individual, a phenomenon known as nutritional programming. In farmed birds as well, the quantity and quality of feed offered to the dam can impact the phenotype of the offspring. We have previously reported that a 38% reduction in the intake of the methyl donor methionine in the diet of 30 female ducks during the growing and laying periods - from 10 to 51 weeks of age - reduced the body weight of their 180 mule ducklings compared to that of 190 ducklings from 30 control females. The maternal dietary methionine restriction also altered the hepatic energy metabolism studied in 30 of their ducklings. Thus, their plasma glucose and triglyceride concentrations were higher while their plasma free fatty acid level was lower than those measured in the plasma of 30 ducklings from the control group. The objective of this new study was to better understand how maternal dietary methionine restriction affected the livers of their newly hatched male and female ducklings by investigating the hepatic expression levels of 100 genes primarily targeting energy metabolism, amino acid transport, oxidative stress, apoptotic activity and susceptibility to liver injury.

Results

Sixteen of the genes studied were differentially expressed between the ducklings from the two groups. Maternal dietary methionine restriction affected the mRNA levels of genes involved in different pathways related to energy metabolism such as glycolysis, lipogenesis or electron transport. Moreover, the mRNA levels of the nuclear receptors PPARGC1B, PPARG and RXRA were also affected.

Conclusions

Our results show that the 38% reduction in methionine intake in the diet of female ducks during the growing and egg-laying periods impacted the liver transcriptome of their offspring, which may explain the previously observed differences in their liver energy metabolism. These changes in mRNA levels, together with the observed phenotypic data, suggest an early modulation in the establishment of metabolic pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08634-1.

Nutrition and Digestive Physiology of the Broiler Chick: State of the Art and Outlook

Simple Summary

The first week after hatch is the most challenging period in the life of broilers. The digestive tract of the newly hatched chick is immature and must undergo dramatic changes before it can efficiently digest and absorb nutrients. The gut is the vital organ where nutrient digestion and absorption take place. Ontogenic changes that accompany improved digestion and absorption include increased secretion of digestive enzymes, increase in the gut absorptive surface area, and enhanced nutrient transporters. The obvious limiting factors are the secretion and activities of digestive enzymes, and the surface area for absorption. These limitations are overcome as the birds grow older, with concurrent improvements in nutrient utilization. In addition, substantial changes also take place in the physical and functional development of the immune system and intestinal microbial ecology. However, the focus of the current review was on nutrition-related challenges and nutritional approaches to assist the chick during this highly demanding period.

Abstract

Because the intestine is the primary nutrient supply organ, early development of digestive function in newly hatched chick will enable it to better utilize nutrients, grow efficiently, and achieve the genetic potential of contemporary broilers. Published data on the growth and digestive function of the gastrointestinal tract in neonatal poultry were reviewed. Several potential strategies to improve digestive tract growth and function in newly hatched chick are available and the options include breeder nutrition, in ovo feeding, early access to feed and water, special pre-starter diets, judicious use of feed additives, and early programming.

Early heat acclimation during incubation improves Japanese quail performance under summer conditions

Effects of exposing quail eggs to high temperature on the heat tolerance ability and productivity of birds were investigated. Four groups of 600 fertile eggs were randomly selected; the first group was incubated under 37.5 °C and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C (Control). The second group was exposed to 39.1 °C for 2 h/day during 4-14 days of embryogenesis and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C. The third group was incubated under 37.5 °C and the hatched chicks were exposed to 39 ± 1 °C for 2 h/day during 4-14 days of age. The fourth group was exposed to 39 ± 1 °C for 2 h during 4-14 days of embryogenesis and the hatched chicks were exposed to 39 ± 1 °C for 2 h/day during 4-14 days of age. The temperature applied changed (P < 0.01) embryo weight and incubation period. Birds exposed to high temperature during brooding had superior growth performance, dressed carcass, body temperature and health traits. Birds subjected to 39 ± 1 °C during brooding exhibited decreased feed consumption and body weight gain. Finally, this work suggests that thermal acclimation during embryogenesis might offer a practical method for easing heat stress.

Short- and long-term consequences of stocking density during rearing on the immune system and welfare of laying hens

Already during early life, chickens need to cope with chronic stressors that can impair their health and welfare, with stocking density being one of the most influential factors. Nevertheless, there is a gap in research on the influence of stocking density on laying hens during rearing and in the subsequent laying period. This study therefore investigated how stocking density during rearing affects the immune system and welfare of pullets, and whether effects are persistent later in life. Pullets were reared at either low (13 birds/m²) or high (23 birds/m²) stocking densities but in identical group sizes from wk 7 to 17. Afterward, hens were kept at the same stocking density (2.4 birds/m²) until wk 28. Blood and tissue samples (spleen and cecal tonsils) were collected at the end of the rearing period and in the laying period. The parameters evaluated encompassed number and distribution of leukocytes and lymphocyte subsets in blood and lymphatic tissue, lymphocyte functionality, plasma corticosterone concentrations as well as behavior and physical appearance of hens. At the end of rearing, pullets kept under high stocking density had lower numbers of T lymphocytes, especially γδ T cells in blood, spleen, and cecal tonsils and displayed a higher heterophil to lymphocyte ratio. These effects are mostly persistent during the laying period, although stocking density was identical at this time. Furthermore, birds from the high stocking density group showed less active behavior, more pecking behavior and worse physical appearance throughout both examination periods. In conclusion, stocking density during rearing affects pullets' immune system and behavior not only in the rearing, but also subsequently in the laying period, indicating a strong correlation between health and welfare during rearing and the laying period.

Effect of prenatal ambient temperature on the performance physiological parameters, and oxidative metabolism of Japanese quail (Coturnix coturnix japonica) layers exposed to heat stress during growth

A strategy to mitigate the negative effects of stress on animals is to enhance their ability to beneficially respond to stressful conditions. This study aimed to assess whether prenatal ambient temperature influences the response of Japanese quail (Coturnix coturnix japonica) chicks to environmental challenges during growth. The experiment was conducted in a 2 × 2 factorial arrangement: two temperature conditions for the mothers (thermoneutral and heat stress by continuous exposure to 32 °C) and two offspring ambient temperature conditions (thermoneutral and heat stress by intermittent exposure to 34 °C for 6 h/day from 15 to 35 days of age). Heat stress in mothers led to lower laying rate, egg mass, expression of methionine sulfoxide reductase A (MSRA) gene, and antioxidant capacity as well as higher chick mortality rate (1-15 days of age). Maternal heat stress led to lower weight gain and total antioxidant capacity and higher feed conversion ratio. Maternal temperature × Offspring temperature interaction effects were observed on carbonylated protein content and HSP70, GSS, and MSRA gene expression. It was observed that, for chicks hatched from heat-stressed mothers, exposure to heat stress led to higher carbonylated protein content and HSP70 expression than exposure to thermoneutral conditions. Maternal heat stress was also responsible for increasing GSS expression in chicks grown under thermoneutral conditions. Chicks hatched from non-stressed mothers and subjected to heat stress had higher MSRA expression compared to chicks maintained in a thermoneutral environment. Our results show that, although maternal heat stress had no negative effects on performance or oxidative metabolism of offspring grown under thermoneutral conditions, it was associated with lower performance and higher protein oxidation in offspring exposed to heat stress during growth. These results could be due in part to alterations in the expression of genes related to antioxidant capacity.

Effect of contact incubation on stress, behavior and body composition in the precocial Red jungle fowl

Birds use contact incubation to warm their eggs above ambient temperature required for embryonic development. In contrast, birds in the industry as well as many birds in breeding programs and scientific studies are incubated in conventional incubators that warm eggs via circulating warm air. This means that contact incubated eggs have different thermal properties than eggs incubated in a conventional incubator. In light of previous studies showing that small differences in incubation temperature can affect chicks post-hatching phenotype, we investigated the consequences of incubating Red jungle fowl eggs at the same temperature (37 °C) either via contact incubation or warm air incubation. We found that contact incubated chicks had a more robust body composition, were more explorative and had a higher temperature preference early in life, as well as a sex dependent difference in plasma Corticosterone levels pre-hatch (measured in down-feathers) and post-hatch (measured in plasma) compared to chicks incubated in a conventional warm air incubator. While previous studies have demonstrated that embryonic development and post-hatch phenotype is sensitive to small variations in temperature, our study demonstrates for the first time that the way heat is distributed to the egg has a similar magnitude of effect on post-hatch phenotype and highlights the sensitivity of the incubation period in shaping birds post-hatch phenotype.

Noise-induced hippocampal oxidative imbalance and aminoacidergic neurotransmitters alterations in developing male rats: Influence of enriched environment during adolescence

Living in big cities might involuntarily expose people to high levels of noise causing auditory and/or extra-auditory impairments, including adverse effects on central nervous system (CNS) areas such as the hippocampus. In particular, CNS development is a very complex process that can be altered by environmental stimuli. We have previously shown that noise exposure of developing rats can induce hippocampal-related behavioral alterations. However, noise-induced biochemical alterations had not been studied yet. Thus, the aim of this work was to assess whether early noise exposure can affect rat hippocampal oxidative state and aminoacidergic neurotransmission tone. Additionally, the effectiveness of an enriched environment (EE) as a neuroprotective strategy was evaluated. Male Wistar rats were exposed to different noise schemes at 7 or 15 days after birth. Upon weaning, some animals were transferred to an EE whereas others were kept in standard cages. Short- and long-term measurements were performed to evaluate reactive oxygen species, thioredoxins levels and catalase activity as indicators of hippocampal oxidative status as well as glutamic acid decarboxylase and a subtype of glutamate transporter to evaluate aminoacidergic neurotransmission tone. Results showed noise-induced changes in hippocampal oxidative state and aminoacidergic neurotransmission markers that lasted until adolescence and differed according to the scheme and the age of exposure. Finally, EE housing was effective in preventing some of these changes. These findings suggest that CNS development seems to be sensitive to the effects of stressors such as noise, as well as those of an environmental stimulation, favoring prompt and lasting molecular changes.

Effects of acute stressors experienced by five strains of layer breeders on measures of stress and fear in their offspring

Stressors experienced by layer breeders during egg production can lead to changes in the egg hormone content, potentially impacting their offspring, the commercial layers. Genetic differences might also affect the offspring's susceptibility to maternal experiences. In this study, we tested if maternal stress affects measures of stress and fear in five strains of layer breeders: commercial brown 1 & 2, commercial white 1 & 2 and a pure line White Leghorn. Each strain was equally separated into two groups: "Maternal Stress" (MS), where hens were subjected to a series of 8 consecutive days of acute psychological stressors, and "Control," which received routine husbandry. Additional eggs from Control were injected either with corticosterone diluted in a vehicle solution ("CORT") or just "Vehicle." Stress- and fear-responses of the offspring were measured in a plasma corticosterone test and a combined human approach and novel object test. While the stress treatments did not  affect the measured endpoints in the offspring, significant strain differences were found. The offspring of the white strains showed a higher physiological response compared to brown strains and the White 2 offspring was the least fearful strain in the human approach test. Our study found that neither the acute psychological stressors experienced by layer breeders nor the egg injections of corticosterone affected the parameters tested in their offspring. Post hoc power analyses suggest that the lack of treatment effects might be due to a small sample size (type II error). Although studies on larger flocks of layers are still needed, our results provide an initial understanding of an important subject, as in poultry production, layer breeders are often subjected to short-term stressors. In addition, our results suggest the dissociation between the physiological and behavioural parameters of stress response in laying hens, showing that increased concentrations of plasma corticosterone in response to stress might not be directly associated with high levels of fear.

Reproductive performance and quality of offsprings of parent stock of layer hens after rearing in open and closed aviary system

In this study, we analyzed the parent stock of ISA Brown hens reared in closed and open aviary (CA and OA, respectively) sections with regard to the productive performance of hens, hatchability, and quality of chicks. The flocks were reared (1,570 cocks and 17,515 hens) for 16 wk in a three-level aviary system. On the 7th wk of rearing, half of the birds (OA group of birds) were allowed to leave the section and use half of the area of the poultry house and to use all levels. The remaining half of the birds were kept in the CA section for the entire duration of rearing. After the duration of rearing, the birds were moved to 2 neighboring production poultry houses (OA = 680 cocks and 8,126 hens; CA = 685 cocks and 8,133 hens). Reproduction was performed in a litter system in accordance with the norms for parent stock of laying hens. During the production cycle (53 wk), laying performance, feed conversion ratio, water consumption, and mortality were analyzed. On 27th, 37th, and 49th wk of production, the following analysis was performed: rate of fertilization (%), rate of hatching (%), and quality of chick. In accordance with the results, birds in OA flock required less amount of feed (P < 0.001) and water (P = 0.020) to produce a laid egg, a hatching egg (respectively: P < 0.001; P = 0.009), and a chick (both P < 0.001) in comparison with the birds in CA flock. In addition, a lower number of litter eggs were found in the OA flock (P < 0.001). Mean laying production, production of hatching eggs, and number of waste eggs did not depend on the flock rearing system (P > 0.05); however, a combined analysis of all these parameters using multivariate analysis of variance demonstrated a better (P < 0.001) result for OA flock than that of CA flock. Rate of fertilization, rate of hatching, and quality of chicks did not depend on the flock rearing system (P > 0.05). In summary, it is possible to rear parent ISA Brown hens in open sections of aviary system without the fear of subsequent deterioration of indicators of future egg production.

Impact of Housing Environment on the Immune System in Chickens: A Review

During their lifespan, chickens are confronted with a wide range of acute and chronic stressors in their housing environment that may threaten their welfare and health by modulating the immune system. Especially chronic stressful conditions can exceed the individual's allostatic load, with negative consequences for immunity. A fully functional immune system is mandatory for health and welfare and, consequently, also for high productivity and safe animal products. This review provides a comprehensive overview of the impact of housing form, light regime as well as aerial ammonia and hydrogen sulfide concentrations on the immune system in chickens. Certain housing conditions are clearly associated with immunological alterations which potentially impair the success of vaccinations or affect disease susceptibility. Such poor conditions counteract sustainable poultry production. This review also outlines current knowledge gaps and provides recommendations for future research.

Impact of Maternal High Stocking Density during the Dry Period on Dairy Calf Health, Behaviour, and Welfare

Simple Summary

Negative impacts of stressful maternal experience during pregnancy on offspring health and behaviour have been reported in various mammalian species including humans, laboratory animals, and farm animals. This study investigated the effect of limited space allowance for dairy cows during late gestation on the growth and behaviour of their offspring during the pre-weaning period. Our results indicated associations between maternal high stocking density and a higher frequency of social behaviours and increased behavioural reactivity to weaning in offspring. Maternal high stocking density also reduced behavioural reactions of healthy offspring to a painful procedure. However, there was no association between maternal high stocking density and offspring growth or behaviour in the first week of life. To our knowledge, this study is the first to attempt to demonstrate associations between maternal stocking density during late pregnancy and offspring behaviour in dairy cattle.

Abstract

This study aimed to investigate the effect of maternal stocking density during late pregnancy (approximately 60 ± 4 days before calving) on offspring performance during the pre-weaning period. Forty-five dairy calves were born to cows that went through either industry minimum standards (H: n = 24, high stocking density) or more extensive space allowances (L: n = 21, low stocking density) during the dry period. Body weight and average daily gain during the pre-weaning period (day 1–49) were measured. Observations were made of: (i) activity levels (day 2–6); ii) the level of training required to use an automatic feeder, and behavioural reactions to the group environment (d7); (iii) feeding and social behaviour in the group pen (day 7–21); and (iv) responses to weaning (day 40–49) and disbudding (day 28+). Compared to L calves, H calves made more frequent social contacts with pen mates in the group pen (p = 0.003) and decreased their lying time around weaning (p = 0.045). Among the healthy calves, L calves displayed more severe behavioural reactions to the disbudding procedure (p < 0.001), a significant increase in salivary cortisol concentrations (p = 0.013), and more frequent pain-related behaviour (p = 0.036). This study indicated associations between maternal stocking density during late pregnancy and some welfare-relevant offspring outcomes during the pre-weaning period; these effects were found to be modulated by offspring health status.

Effects of Maternal Stress on Measures of Anxiety and Fearfulness in Different Strains of Laying Hens

Maternal stress can affect the offspring of birds, possibly due to hormone deposition in the egg. Additionally, phenotypic diversity resulting from domestication and selection for productivity has created a variety of poultry lines that may cope with stress differently. In this study, we investigated the effects of maternal stress on the behavior of different strains of laying hens and the role of corticosterone as its mediator. For this, fertilized eggs of five genetic lines-two brown (Brown 1 and 2), two white (White 1 and 2), and one pure line White Leghorn-were reared identically as four flocks of 27 birds (24F: 3M) per strain. Each strain was equally separated into two groups: Maternal Stress ("MS"), where hens were subjected to a series of daily acute psychological stressors for 8 days before egg collection, and "Control," which received routine husbandry. Fertile eggs from both treatments were collected at three different ages forming different offspring groups that were treated as replicates; additional eggs from Control were injected either with corticosterone diluted in a vehicle solution ("CORT") or just "Vehicle." Eggs from each replicate were incubated and hatched, and offspring (N = 1,919) were brooded under identical conditions. To measure the effects of maternal stress on anxiety and fear-like behavior, offspring were subjected to a social isolation test (SI) between 5 and 10 days of age and a tonic immobility test (TI) at 9 weeks of age. Compared to Control, MS decreased the number of distress vocalizations emitted by White 2 in SI. No effects of MS were observed in TI, and no effects of CORT were observed in any tests. Overall, brown lines vocalized more in SI and remained in TI for a longer duration than white strains, suggesting genetic differences in fear behavior. Females vocalized more than males in TI and showed a trend toward significance for the same trait in SI. Overall, results suggest that the effects of maternal stress on fearfulness are not directly mediated by corticosterone. Moreover, it highlights behavioral differences across various strains of laying hens, suggesting that fear responses are highly dependent on genotype.

Fetal betaine exposure modulates hypothalamic expression of cholesterol metabolic genes in offspring cockerels with modification of promoter DNA methylation

In documents, maternal betaine modulates hypothalamic cholesterol metabolism in chicken posthatchings, but it remains unclear whether this effect can be passed on by generations. In present study, eggs were injected with saline or betaine at 2.5 mg/egg, and the hatchlings (F1) were raised under the same condition until sexual maturation. Both the control group and the betaine group used artificial insemination to collect sperm from their cockerels. Fertilized eggs were incubated, and the hatchlings of the following generation (F2) were raised up to 64 D of age. F2 cockerels in betaine group showed significantly (P < 0.05) lower body weight, which was associated with significantly decreased (P < 0.05) hypothalamic content of total cholesterol and cholesterol ester. Concordantly, hypothalamic expression of cholesterol biosynthetic genes, SREBP2 and HMGCR, were significantly downregulated (P < 0.05), together with cholesterol conversion-related and excretion-related genes, CYP46A1 and ABCA1. These changes coincided with a significant downregulation in mRNA expression of regulatory neuropeptides including brain-derived neurotrophic factor, neuropeptide Y, and corticotropin-releasing hormone. Moreover, genes involved in methyl transfer cycle were also modified. Betaine homocysteine methyltransferase (P < 0.05) was downregulated, yet DNA methyltransferase1 tended to be upregulated (P = 0.06). S-adenosyl methionine/S-adenosylhomocysteine ratio was higher in the hypothalamus of betaine-treated F2 cockerels, which was associated with significantly modified CpG methylation on the promoter of those affected genes. These results suggested that betaine might regulate central cholesterol metabolism and hypothalamic expression of genes related to brain function by altering promoter DNA methylation in F2 cockerels.

The effect of reduced balanced protein diet on the behavior of female broiler breeders in 2 generations

The behavior of 2 generations of broiler breeders undergoing a 25% reduced balanced protein (RP) dietary treatment was investigated in the current study. There were 2 treatments for the F0 generation: control (C) breeders fed with standard C diets and RP breeders fed with RP diets. The female progeny of each treatment was again subjected to 2 dietary treatments, resulting in 4 treatments for F1 generation: C/C, C/RP, RP/C, and RP/RP (breeder feed in F0/F1 generation). To maintain the target body weights throughout the trial, breeders on RP diet received on average 10% more feed than C diet breeders. The behavior of the breeders at 8h30 (30 min before feeding at 9h00), 12h00, and 15h30 in weeks 23 and 37 of the F0 generation and in week 6, 11, and 22 of the F1 generation was observed. Litter scratching, feather pecking, and object pecking were occasionally increased by RP diet feeding which indicated feeding frustration. Drinking behavior decreased dramatically by the RP dietary feeding and resulting in a better litter condition which could benefit dust bathing behavior. In addition, feeding the breeders RP diet in the F0 generation decreased litter scratching (week 6) and feather pecking (week 22, 15h30) but increased sitting (week 11, 15h30) and drinking (a tendency in week 6 and a significant effect in week 11) behavior of offspring breeders (F1 generation). In general, breeders fed with reduced balanced protein diets, to some extent, spent less time drinking and their offspring could have an adaptation to the maternal RP diet. The mechanism of this adaptation still needs to be further investigated. In general, positive effects were found by reducing protein level of breeder diets. However, negative side effects such as feeding frustration were also observed, which merit further study.

Sound exposure and its beneficial effects on embryonic growth and hatching of broiler chicks

1. The physical factors that involve artificial incubation determine embryonic growth and hatching of broiler chicks, and have important implications for the poultry production chain and chick welfare. This study explored the effects of sound exposure on incubation responses (hatching, embryonic development and chick quality).2. A 2 × 2 factorial experiment with the factors 'sound pressure level' (at 70 and 90 dB) and 'species-specific vocalisations' (at 75dB - 85dB) was performed in four experimental incubators (loaded with 90 eggs each) for eight consecutive cycles of incubation, totalling 2880 Cobb-500® broiler breeder eggs.3. Embryonic growth was not influenced by any experimental factor, but the highest sound pressure level (90 dB) led to earlier hatching, higher hatchability, better chick quality and lower weight at hatching. Additional effects of species-specific vocalisations were found at 70 dB noise, which caused early hatching and better chick quality.4. It was concluded that the loud noise found in commercial hatcheries (at 90 dB) can be beneficial. Furthermore, the presence of species-specific vocalisations could improve the hatching time and chick quality from experimental incubators (at 70 dB). However, this would not provide additional benefits in commercial hatcheries, due to the machinery noise masking them.

Human behaviour at the origin of maternal effects on offspring behaviour in laying hens (Gallus gallus domesticus)

Regular visual presence of humans is known to reduce chickens' human-generated stress responses. Here we questioned whether, more than mere visual presence, human behaviour affects laying hen behaviour and subsequently their offspring's behaviour. We hypothesized that human behaviour triggers maternal effects via variations in yolk hormone levels. For five consecutive weeks, two groups of hens were exposed to the same durations of human presence (30 min twice a day, five days a week) but the behaviour of the human differed between groups. The first group (H+) was exposed to predictable arrival of the experimenter, slow movements combined with static presence, stroking during handling and human voice. Whereas the second group of hens (H-) was exposed to unpredictable arrival of the experimenter which remained silent, in motion, and did not provide stroking during handling. At the end of the treatment, we evaluated egg quality and offspring behaviour. We found that avoidance of the experimenter by H+ hens but not by H- hens decreased significantly. Fertility rates and concentrations of yolk progesterone and estradiol in H+ hens' eggs were higher than in H- hens' eggs. Fear of humans, neophobia or the capacity to solve a detour task did not differ significantly between H+ and H- chicks. Social discrimination tests showed that H+ chicks but not H- chicks typically preferred a familiar conspecific to a stranger. These results show that, with the same duration in the presence of the birds, humans through their behaviour engender variations in fertility rates, yolk hormone levels and transgenerational effects on social skills. Rarely explored, our data suggest that maternal effects influence filial imprinting. These data have broad implications for laboratory, commercial systems and conservatory programs where the inevitable presence of humans could trigger maternal effects on offspring phenotype.

Plasma Farming: Non-Thermal Dielectric Barrier Discharge Plasma Technology for Improving the Growth of Soybean Sprouts and Chickens

Non-thermal dielectric barrier discharge (DBD) plasma is an innovative and emerging field combining plasma physics, life science and clinical medicine for a wide-range of biological applications. Plasma techniques are applied in treating surfaces, materials or devices to realize specific qualities for subsequent special medical applications, plant seeds to improve the production and quality of crops, and living cells or tissues to realize therapeutic effects. Several studies that are summarized within this review show that non-thermal DBD plasma technique has potential biological applications in soybean sprout growth, chicken embryonic development and postnatal growth rate, and even male chicken reproductive capacity. The current developments in the non-thermal DBD plasma technique may be beneficial to improve plant and poultry productivity.

Effects of Management Related Practices on Turkey Hen Performance Supplemented With Either Original XPC™ or AviCare™

During commercial production, turkeys may be exposed to several different types of stressors related to environmental conditions and management practices. Historically, antibiotics have been used to aid in the alleviation of the impacts of stressful situations, and alternatives to antibiotics related to reducing stress are being researched. This study consisted of three rearing trials and had two objectives: (1) Investigate the effects of common U.S. turkey production practices, including environmental and management induced stress, on turkey hens grown to 63 days, and (2) Determine the response of stressed birds to dietary supplementation with fermentation derived functional metabolites. Treatments consisted of a positive control (stressed but not supplemented), a negative control (non-stressed and not supplemented) and two treatment groups that were stressed and supplemented with different products (Original XPC™ or AviCare™). Supplemental products were administered in a dry (feed) and liquid (drinking water) form, and consisted of fermentation derived functional metabolites. Products were evaluated on their effectiveness to mitigate stress responses and turkey performance. Birds were exposed to some combinations of the following stressors: feed and water withdrawal, cold, heat, and crowding. Although the stressors in this study were applied for less than 24 h, they produced significant physiological responses. Blood corticosterone levels, measured immediately after stress, were significantly higher in positive control birds than in negative control birds. In addition, stressed birds had reduced body weights and increased FCR after stress. Stressed birds, supplemented with products had mixed, but generally positive response as measured by bird performance. Based on the response to stress, as observed by alterations in blood corticosterone levels and differences in performance between the two control groups, researchers induced an effective stress model. The use of supplementary products consisting of fermentation derived functional metabolites shows promise for reducing negative impacts of a mixture of stressors.

Transgenerational epigenetic inheritance in birds

While it has been shown that epigenetics accounts for a portion of the variability of complex traits linked to interactions with the environment, the real contribution of epigenetics to phenotypic variation remains to be assessed. In recent years, a growing number of studies have revealed that epigenetic modifications can be transmitted across generations in several animal species. Numerous studies have demonstrated inter- or multi-generational effects of changing environment in birds, but very few studies have been published showing epigenetic transgenerational inheritance in these species. In this review, we mention work conducted in parent-to-offspring transmission analyses in bird species, with a focus on the impact of early stressors on behaviour. We then present recent advances in transgenerational epigenetics in birds, which involve germline linked non-Mendelian inheritance, underline the advantages and drawbacks of working on birds in this field and comment on future directions of transgenerational studies in bird species.

Spatial Cognition and Range Use in Free-Range Laying Hens

Simple Summary

Individual free-range laying hens vary in their use of the outdoor range. The outdoor environment is typically more complex and variable than indoor housing and thus range use may be related to differences in spatial abilities. Individual adult hens that never went outside were slower to learn a T-maze task—which requires birds to repeatedly find a food reward in one arm of the maze, compared to outdoor-preferring hens. Pullets that were faster to learn the maze also showed more visits to the range in their first month of range access but only in one of two tested groups. Early enrichment improved learning of the maze but only when the birds were tested before onset of lay. Fear may play a role in inhibiting bird’s spatial learning and their range use. More studies of different enriched rearing treatments and their impacts on fear and learning would be needed to confirm these findings. Overall, these results contribute to our understanding of why some birds choose to never access the outdoor range area.

Abstract

Radio-frequency identification tracking shows individual free-range laying hens vary in range use, with some never going outdoors. The range is typically more environmentally complex, requiring navigation to return to the indoor resources. Outdoor-preferring hens may have improved spatial abilities compared to indoor-preferring hens. Experiment 1 tested 32 adult ISA Brown hens in a T-maze learning task that showed exclusively-indoor birds were slowest to reach the learning success criterion (p < 0.05). Experiment 2 tested 117 pullets from enriched or non-enriched early rearing treatments (1 pen replicate per treatment) in the same maze at 15–16 or 17–18 weeks. Enriched birds reached learning success criterion faster at 15–16 weeks (p < 0.05) but not at 17–18 weeks (p > 0.05), the age that coincided with the onset of lay. Enriched birds that were faster to learn the maze task showed more range visits in the first 4 weeks of range access. Enriched and non-enriched birds showed no differences in telencephalon or hippocampal volume (p > 0.05). Fear may reduce spatial abilities but further testing with more pen replicates per early rearing treatments would improve our understanding of the relationship between spatial cognitive abilities and range use.

Tissue-Specific Expression of DNA Methyltransferases Involved in Early-Life Nutritional Stress of Chicken, Gallus gallus

DNA methylation was reported as a possible stress-adaptation mechanism involved in the transcriptional regulation of stress responsive genes. Limited data are available on effects of psychological stress and early-life nutritional stress on DNA methylation regulators [DNMTs: DNA (cytosine-5)-methyltransferase 1 (DNMT1), DNMT1 associated protein (DMAP1), DNMT 3 alpha (DNMT3A) and beta (DNMT3B)] in avian species. The objectives of this study were to: (1) investigate changes in expression of DNMT1, DMAP1, DNMT3A, and DNMT3B following acute (AS) or chronic immobilization stress (CS); (2) test immediate effect of early-life nutritional stress [food deprivation (FD) for 12 h (12hFD) or 36 h (36hFD) at the post-hatching period] on expression of DNA methylation regulators and glucocorticoid receptor (GR), and the long-term effect of early-life nutritional stress at 6 weeks of age. Expression of DNMTs and plasma corticosterone (CORT) concentration decreased by CS compared to AS (p < 0.05), indicating differential roles of DNA methylation regulators in the stress response. Plasma CORT at 12hFD and 36hFD birds increased compared to control birds (12hF and 36hF), but there were no significant differences in plasma CORT of 12hFD and 36hFD birds at 6 weeks of age compared to 6 week controls. DNMT1, DMAP1, and DNMT3B expression in the anterior pituitary increased by 12hFD, but decreased at 36hFD compared to their controls (P < 0.05). In liver, DNMT1, DNMT3A, and DNMT3B expression decreased by 12hFD, however, no significant changes occurred at 36hFD. Expression of DMAP1, DNMT3A, and DNMT3B in anterior pituitary and DMAP1 and DNMT3A expression in liver at 6 weeks of age were higher in 36hFD stressed birds compared to controls as well as 12hFD stressed birds. Hepatic GR expression decreased by 12hFD and increased by 36hFD (p < 0.05). Expression patterns of GR in the liver of FD stress-induced birds persisted until 6 weeks of age, suggesting the possible lifelong involvement of liver GR in early-life nutritional stress response of birds. Taken together, results suggest that DNA methylation regulator genes are tissue-specifically responsive to acute and chronic stress, and hepatic GR may play a critical role in regulating the early-life nutritional stress response of birds. In addition, the downregulation of DNMT1 and DMAP1 may be one of the adaptive mechanisms to chronic early-life nutritional stress via passive demethylation.

Invited review: resource allocation mismatch as pathway to disproportionate growth in farm animals - prerequisite for a disturbed health

The availability of resources including energy, nutrients and (developmental) time has a crucial impact on productivity of farm animals. Availability of energy and nutrients depends on voluntary feed intake and intestinal digestive and absorptive capacity at optimal feeding conditions. Availability of time is provided by the management in animal production. According to the resource allocation theory, resources have to be allocated between maintenance, ontogenic growth, production and reproduction during lifetime. Priorities for these processes are mainly determined by the genetic background, the rearing system and the feeding regimen. Aim of this review was to re-discuss the impact of a proper resource allocation for a long and healthy life span in farm animals. Using the barrel model of resource allocation, resource fluxes were explained and were implemented to specific productive life conditions of different farm animal species, dairy cows, sows and poultry. Hypothetically, resource allocation mismatch neglecting maintenance is a central process, which might be associated with morphological constraints of extracellular matrix components; evidence for that was found in the literature. A potential consequence of this limitation is a phenomenon called disproportionate growth, which counteracts the genetically determined scaling rules for body and organ proportions and could have a strong impact on farm animal health and production.

Lipids in maternal diet influence yolk hormone levels and post-hatch neophobia in the domestic chick

We assessed whether the ratio of dietary n-6/n-3 polyunsaturated fatty acids (PUFA) during egg formation engenders transgenerational maternal effects in domestic chicks. We analyzed yolk lipid and hormone concentrations, and HPA-axis activity in hens fed a control diet (high n-6/n-3 ratio) or a diet enriched in n-3 PUFAs (low n-6/n-3 ratio) for 6 consecutive weeks. Their chicks were tested for neophobia during the first week of life. We found higher corticosterone metabolites in droppings of hens fed the diet enriched in n-3 and significantly higher concentrations of yolk progesterone, androstenedione, and estradiol in their eggs compared to controls. Chicks of hens fed the n-3 enriched diet showed a lower body mass at hatch than controls and expressed higher neophobia when exposed to a novel object. These results add support to the hypothesis that the nutritional state of female birds produces variation in yolk hormone levels and engender maternal effects.