Yolk Content Research Articles

Carotenoid deposition in yolks of laying hens fed with corn diets differing in grain hardness and supplemented with rapeseed oil and emulsifier

This study investigated the effects of supplementing diets consisting of two dent corn hybrids (soft- and hard-type) with different amounts of rapeseed oil (2, 3, and 4%) and with (0.05%) or without emulsifier (Lysoforte Extended, Kemin) on the content and deposition of carotenoids in egg yolk. The feeding trial was conducted with 216 Lohmann Brown laying hens which were by 3 located in 72 cages. The cages were randomly assigned to 12 dietary treatments (2 hybrids × 3 rapeseed oil levels × 2 emulsifier levels), resulting in 6 cages (replicates) per each dietary treatment. After depletion, hens were fed treatment diets without added pigment for 7 wk. After stabilization of the carotenoid profile (lutein, zeaxanthin, α- and β-cryptoxanthin and β-carotene and total carotenoids), eggs were collected once a week until the end of the experiment and deposition efficiency was calculated based on carotenoid content in yolk and diets, yolk weight, egg production and diet intake. Corn hybrid and rapeseed oil affected (P < 0.05) the yolk content and deposition efficiency of most carotenoids. Moreover, a significant (P < 0.05) hybrid × rapeseed oil level interaction for all carotenoids indicated hybrid-specific responses to rapeseed oil supplementation. In the soft-type hybrid, the addition of 3% rapeseed oil enhanced the carotenoid content compared to 2% of rapeseed oil, whereas for the hard-type hybrid, 2 and 3% of rapeseed oil resulted in similar contents. Supplementation of 4% rapeseed oil reduced the content regardless of the hybrid. Emulsifier addition positively affected (P < 0.05) the deposition efficiency of all carotenoids except β-carotene. In conclusion, supplementing corn diets with rapeseed oil and emulsifier affected carotenoid utilization and these responses varied in hybrids differing in grain hardness, which should be considered when using corn as the sole source of carotenoids in hen diets.

Enriching Eggs with Bioactive Compounds through the Inclusion of Grape Pomace in Laying Hens Diet: Effect on Internal and External Egg Quality Parameters.

(1) Background: Grapes and their associated by-products (such as grape pomace, GP) stand out for their polyphenol content, which makes them a source of bioactive compounds with antioxidant capacity. The aim of this research was to determine if the inclusion of 50 g/kg of GP in the diet of hens could enrich eggs with antioxidants and to study its effect on internal and external egg quality parameters. (2) Methods: A trial was conducted with two genetic lines of hens, which were fed either a control diet or a diet containing 50 g/kg of GP. Performance, internal and external egg quality, and egg yolk content of vitamins E and A and gallic acid were determined. (3) Results: In eggs laid by hens fed a GP diet, Haugh units and yolk color scores were enhanced, and eggshells became thinner, but without affecting the breaking strength. No dietary effect was observed on the vitamin contents of the yolk. A higher gallic acid content was observed in the yolks of eggs laid by hens fed the GP diet, suggesting that some dietary phenolic compounds could be transferred to the eggs. Hen genetics influenced egg weight, albumen Haugh units, shell thickness, and α- and γ-tocopherol concentration in yolks. (4) Conclusions: Dietary inclusion of GP improved the internal quality of eggs, enriching yolks with a phenolic compound but reducing shell thickness.

Residue, distribution and depletion of fluralaner in egg following a single intravenous and transdermal administration in healthy shaver hens: fluralaner residue in egg

The demand for the use of fluralaner in an extra label manner is increasing due to lack of efficacious treatment to combat mites and bed bugs in the poultry industry in the United States. Fluralaner residue data in eggs is lacking and residues might cause risks to human health. The present study aimed to determine the depletion profiles of fluralaner in eggs and estimate the drug withdrawal interval in whole eggs by adopting the US Food and Drug administration tolerance limit method with single intravenous (0.5 mg/kg) or transdermal administration (average 58.7 mg/kg) in healthy shaver hens. Hens were treated intravenously or trans-dermally with fluralaner. The eggs were collected daily for 28 days for intravenous treated and for 40 days from the transdermal route group. Fluralaner concentrations in yolk and albumen were determined by mass spectrometry. The greater percentage of fluralaner was observed in yolk when compared to the albumen for both administration routes. Non-compartmental analysis was used to calculate the pharmacokinetic parameters in yolk, albumen and whole egg. The longest apparent half-life confirmed in yolk was 3.7 days for intravenous and 14.3 days for the transdermal route. The withdrawal intervals in whole egg for fluralaner following the intravenous and transdermal administration were 7 days and 81 days, respectively, with maximum residue limits (1.3 µg/g) at 13 days and 171 days, respectively, based on the limit of quantification (0.4 µg/g) from the analytical assay reported by EMA and APVMA.

Effects of supplementation of different selenium sources on lipid profile, selenium, and vitamin E concentration of yolk.

Egg preference as a source of protein also provides beneficial fatty acids, vital for human consumption. However, rich in lipid products are prone to oxidative damage. The study aims to determine the effect of supplementing biogenic selenium (Se) from Stenotrophomonas maltophilia, ADS18 (ADS18) in laying hens' diet on yolk lipid oxidation status (MDA), beta-carotene (β-carotene) content, cholesterol, fatty acids, Se, and vitamin E (VE) level. A total of one hundred and twenty (120) laying hens of Lohmann Brown strains aged 50 weeks, weighing 1500 to 2000g were reared individually in A-shape two-tier stainless-steel cages sized 30cm x 50cm x 40cm (width, depth height). The hens were randomly allotted into four treatments with six replications in a complete randomised design for the period of 12 weeks. The basal diet contains 100mg/kg VE. Treatment diets consist of basal diet as control, SS containing 0.3mg/kg sodium selenite, Se-yeast containing 0.3mg/kg selenised yeast, and VADS18 containing 0.3mg/kg of ADS18. Forty-eight eggs were collected and freeze-dried biweekly for analysis. The results of the present study showed that hens supplemented ADS18 had significantly (P < 0.05) lower MDA and cholesterol levels while their egg yolks had higher levels of Se and mono-unsaturated fatty acids (MUFA). The control group had significantly (P < 0.05) higher saturated fatty acid (SFA) contents than the VE and dietary Se-supplemented groups, while the ADS18 group had the lowest SFA contents. Conversely, in comparison to the inorganic and control groups, the VE content of the egg yolk was significantly (P < 0.05) higher in organic Se-supplemented (Se-yeast and VADS18) groups. Hens with SS supplementation had significantly (P < 0.05) higher egg yolk β-carotene content. When compared to other treatment groups, the control group had higher (P < 0.05) polyunsaturated fatty acids (PUFA) content. The ADS18 is therefore deemed comparable to other Se sources. To prevent Se toxicity, however, a better understanding of the levels of ADS18 incorporation in poultry diets is required.

Yellowness of egg yolks influences consumer preference for eggs in Ghana

The present work evaluated β-carotene content, colour (L*, a*, b*), and consumer preference for egg yolks from chicken, guinea fowl, and quail, sampled from intensive or semi-intensive rearing systems in Ghana. The β-carotene content of guinea fowl yolk was almost seven times greater (p &lt; 0.001) than that of chicken and quail yolks. The yellowness of guinea fowl yolk (82.18; p &lt; 0.01) was approximately 1.5 and 1.3 times greater than that of chicken and quail yolks, respectively. A consumer preference test showed a significantly greater score (5; p &lt; 0.001) for guinea fowl than for the other egg types. The yellowness of egg yolks had strong positive relationship with β-carotene content (r = 0.943; p = 0.216) and consumer preference (r = 0.995; p = 0.064). Therefore, enhancing the yellowness of egg yolks on the Ghanaian market, especially those from chicken, could lead to increased egg consumption in Ghana.

Carotenoid content and deposition efficiency in yolks of laying hens fed with dent corn hybrids differing in grain hardness and processing

Yolk carotenoid profile reflects the hen diet when corn grain is the only source of carotenoids, but corn origin and processing may affect carotenoid utilization. In the present study, 2 commercial dent corn hybrids differing in grain hardness (soft- and hard-type) were dried at low (40°C) and high (85°C) temperature and ground through a 5- and 9-mm sieve to investigate their effects on carotenoid bioavailability in laying hens. With 3 hens per cage, 168 Lohmann Brown laying hens were allocated to 8 dietary treatments (2 hybrids × 2 drying temperatures × 2 grinding sieves) in a completely randomized design (8 treatments × 7 cages). The trial lasted 8 wk, during which eggs were collected for analysis every 3 d until carotenoid content stabilized, and then once a week until the end of the experiment. The carotenoid profile of the experimental diets and yolks was analyzed using an HPLC method and deposition efficiency was calculated based on carotenoid contents, yolk weight, egg production and diet intake. The deposition efficiency for lutein, zeaxanthin, α- and β-cryptoxanthin, and β-carotene averaged 27.37, 18.67, 6.29, 3,32, and 0.94%, respectively. As expected, the tested hybrids highly affected the carotenoid content in egg yolk due to their differences in carotenoid profile. Interestingly, hard- and soft-type hybrids differed in the deposition efficiency for all individual carotenoids but not for the total carotenoids. High grain drying temperature tended to increase the bioavailability of lutein and zeaxanthin in both hybrids. For the hard-type hybrid, the content of β-carotene in egg yolk was higher when grains were dried at a high temperature, while the opposite response was found in the soft-type hybrid. The effect of grinding sieve size was important for the zeaxanthin bioavailability in the soft-type hybrid only. In conclusion, our findings showed that corn hybrid had a primary influence on the carotenoid content in the yolks of laying hens, but grain processing may change the bioavailability of carotenoids.

Chinese herb ultrafine powder supplementation improves egg nutritional value and quality in laying hens

This study evaluates the effects of dietary Chinese herb ultrafine powder (CHUP) supplementation in late-phase laying hens on the quality and nutritional values of eggs. A total of 576 Xinyang black-feather laying hens (300-day-old) were randomly allocated into eight groups for a 120-day feeding trial. Each group contained eight replicates with nine hens per replicate. The experimental groups included the control (basal diet) and different levels of CHUP groups (details in ‘Materials and methods’). The results showed that the eggshell strength was increased (p < 0.05) in the L, LF, L-LF, L-T, and LF-T groups on day 60 of the trial. In addition, the plasma estradiol level in the L-LF, LF-T, and L-LF-T groups and unsaturated fatty acids concentrations in egg yolk of the CHUP groups (except LF-T group) were increased, whereas total cholesterol (T, L-LF, L-T, and L-LF-T groups) in egg yolk and the atherogenicity (T, L-T, and L-LF-T groups) and thrombogenicity (T, L-LF, L-T, and L-LF-T groups) indexes were decreased (p < 0.05) on day 60 of the trial compared with the control group. Moreover, bitter amino acids in egg albumen were decreased (p < 0.05) in the L-LF group on day 60 and the L-LF-T group on day 120 of the trial. Collectively, these findings indicate that dietary CHUP supplementation could improve eggshell quality and increase plasma reproductive hormone, fatty acid and amino acid composition, and nutritional values of eggs, especially L-LF and L-LF-T.

Effects of dietary supplementation of polysaccharide from Agaricus blazei Murr on productive performance, egg quality, blood metabolites, intestinal morphology and microbiota of Korean quail.

This study aimed to investigate the effects of dietary supplementation with Agaricus blazei polysaccharide (ABP) at varying concentrations on the performance, egg quality, blood biochemistry, intestinal morphology, and microflora of quail. The study involved a total of 2,700 Korean quails, which were randomly divided into three groups. The measured variables encompassed productive performance, egg parameters, carcass parameters, serum metabolites, immune response parameters, antioxidative properties, and gut microbiome. The addition of ABP did not have a significant effect on average daily feed intake. However, it was found to increase the average daily egg weight and egg production rate, reduce the feed-egg ratio. There were no significant impacts on egg quality measures such as egg shape index, egg yolk index and color, egg yolk and protein content. However, ABP supplementation significantly increased the Hough unit (p<0.01) and decreased the rate of unqualified eggs (p<0.01). Regarding serum parameters, the inclusion led to an increase in total protein concentration (p<0.05) and a reduction in low-density lipoprotein cholesterol (p<0.05). There were no significant effects observed on immune indicators such as immunoglobulin A (IgA) and IgM. ABP supplementation increased the levels of serum antioxidant indicators, including glutathione peroxidase, total superoxide dismutase (p<0.05), and total antioxidant capacity colorimeter (p<0.05). Furthermore, ABP supplementation significantly elevated the intramuscular fatty acid content in quail meat. Additionally, ABP supplementation demonstrated a significant improvement in the diversity of gut microbiota and induced alterations in the composition of the gut microbiota. The findings of this study indicate that dietary supplementation of ABP enhanced production performance and antioxidant capacity while increasing the levels of polyunsaturated fatty acids in quail muscle.

High Dietary Folic Acid Supplementation Reduced the Composition of Fatty Acids and Amino Acids in Fortified Eggs.

The study aimed to evaluate the effects of dietary folic acid (FA) on the production performance of laying hens, egg quality, and the nutritional differences between eggs fortified with FA and ordinary eggs. A total of 288 26-week-old Hy-Line Brown laying hens (initial body weights 1.65 ± 0.10 kg) with a similar weight and genetic background were used. A completely randomized design divided the birds into a control group and three treatment groups. Each group consisted of six replicates, with twelve chickens per replicate. Initially, all birds were fed a basal diet for 1 week. Subsequently, they were fed a basal diet supplemented with 0, 5, 10, or 15 mg/kg FA in a premix for a duration of 6 weeks. Supplementation of FA could significantly (p < 0.05) enhance the FA content in egg yolks, particularly when 10 mg/kg was used, as it had the most effective enrichment effect. Compared to the control group, the Glu content in the 10 and 15 mg/kg FA groups showed a significant (p < 0.05) decrease. Additionally, the contents of Asp, Ile, Tyr, Phe, Cys, and Met in the 15 mg/kg FA group were significantly (p < 0.05) lower compared to the other groups. Adding FA did not have significant effects on the levels of vitamin A and vitamin E in egg yolk, but the vitamin D content in the 5 and 10 mg/kg FA groups showed a significant (p < 0.05) increase. Furthermore, the addition of FA did not have a significant effect on the levels of Cu, Fe, Mn, Se, and Zn in egg yolk. The dietary FA did not have a significant effect on the total saturated fatty acids (SFA) and polyunsaturated fatty acid (PUFA) content in egg yolk. However, the total monounsaturated fatty acid (MUFA) content in the 5 and 10 mg/kg groups significantly (p < 0.05) increased. These changes in nutritional content might be attributed to the increased very low-density lipoprotein (VLDL) protein content. The significant decrease in solute carrier family 1 Member 1 (SLC1A1), solute carrier family 1 Member 2 (SLC1A2), and solute carrier family 1 Member 3 (SLC1A3) gene expression compared to the control group appeared to be the reason for the decrease in amino acid content in egg yolk within the dietary FA group. The findings suggest that the appropriate addition of FA can enhance the levels of MUFA and vitamin D in egg yolks, thereby improving their nutritional value. Excessive intake of FA can decrease the effectiveness of enriching FA in egg yolk and impact the enrichment of certain amino acids. The yolk of eggs produced by adding 10 mg/kg of FA to the feed contains the optimal amount of nutrients. This study informs consumers purchasing FA-fortified eggs.

Effects of the Oil and Fat Feeding Period on the Nutritional Composition and Functional Properties of Eggs

Lipids are commonly incorporated into the diets of laying hens at a rate of 1% to 2% during production. However, the effects on egg quality can vary based on the source and timing of lipid addition. Hence, this experiment was conducted to investigate the impacts of adding the same concentration of soybean oil, lard, and mixed oils (1.5%) to the daily feed of layer during two feeding periods. This study aimed to assess the changes in nutritional composition and functional properties and offer valuable insights to determine suitable types of oils and fat. In this study, the experiment was conducted in two test periods, 7 days and 21 days after the addition of the lipids, to assess the effects on the nutritional composition and functional properties of eggs. The study revealed the following results: (1) Changes in the yolk’s nutritional composition. Compared to the 7-day addition period, the inclusion of lard significantly increased the unsaturated fatty acids after 21 days; (2) Changes in the albumen’s nutritional composition. Compared to the 7-day addition period, the inclusion of lard and mixed oils significantly reduced the essential and nonessential amino acids after 21 days; (3) Changes in the functional characteristics of the eggs. After 21 days of addition, the eggs from the soybean oil group exhibited significantly higher foaming and emulsifying properties compared to the groups supplemented with lard and mixed oils; (4) Changes in the antioxidant capacity of the eggs. Compared to the 7-day addition period, the inclusion of all oils and fat significantly increased the superoxide dismutase (SOD) content in egg yolk after 21 days. The aim of this experiment was to provide valuable scientific data to assist producers in making informed decisions regarding the utilization of feeding oils.

Acid-modified pea protein isolate and okara cellulose crystal: A co-emulsifier to improve physico-chemical stability of fat-reduced eggless mayonnaise

Mayonnaise, a high fat emulsified food, always contains egg yolk as a source of emulsifier. Lowering fat content and restricting use of egg yolk are promising ways to enhance nutritive profile and attraction to vegan trend. This work aimed to prepare fat-reduced eggless mayonnaise with good physicochemical stability using pea protein isolate (PPI) in combination with cellulose crystals as a co-emulsifier. Emulsifying property of Okara cellulose crystals (OC) and modified OC using gallic acid (OCG) was investigated. The cellulosic materials possessed effective emulsifying property, particularly at increased concentration. The present work suggested that acid-aided hydrolysis could improve emulsifying property of PPI. Then, the acid-modified PPI (aPPI) together with OC or OCG were employed at different ratios as a co-emulsifier for fat-reduced eggless mayonnaise preparation. The co-emulsifier could improve dispersibility and rheological property of the mayonnaise effectively. In addition, the cellulosic materials improved oxidative stability of the mayonnaises, particularly for OCG. This behavior might be expected since a steric hindrance effect of the interfacial films of co-emulsifier, in addition to antioxidant capacity of OCG. Thus, the innovative addition of the dual modes of emulsifying and antioxidant actions could be used to improve physicochemical stability and reduce fat content of eggless mayonnaise.

Carvacrol in ovo delivery optimization and flow dynamics in broiler chicken eggs

In ovo delivery of carvacrol, the primary active compound in oregano essential oil (OEO) has the potential to enhance gut development in broilers. This study aimed to optimize in ovo application of OEO by investigating day and site of injection and delivery of carvacrol to different embryonic tissues. In Experiment 1, 2 d of injection (embryonic day (E) 12 or 17.5) and 3 sites of injection for OEO (air cell, amniotic fluid, or yolk) were evaluated based on hatchability and posthatching performance. Experiment 2 aimed to examine the impact of combining OEO with the nonionic surfactant polysorbate 80 (p80) at ratios to carvacrol of 0:0, 0:1, 0.5:1, and 1:1 on carvacrol concentration in amniotic fluid, blood, and yolk. The concentration of carvacrol was measured at 3, 6, and 9 h after OEO injection either without (0:1) or with (1:1) p80. Injection of OEO on E12 led to a significant lower hatchability compared to E17.5 (P ≤ 0.01; Δ = 9.2%). Injecting OEO into the air cell, amniotic fluid, or yolk at E17.5 did not significantly affect hatchability and posthatching performance. The highest concentrations of carvacrol found in egg tissues were observed when injected together with surfactant at the 1:1 ratio (P ≤ 0.001; 14.45 µM, 16.64 µM, and 124.82 µM, for air cell, amniotic fluid, and yolk, respectively) compared to the 0:0, 0:1 or 0.5:1 ratios. Carvacrol was highest in the amniotic fluid and blood at the first time point (3 h postinjection) and decreased afterward (P ≤ 0.001), whereas the concentration in yolk remained elevated up to 9 h postinjection. In conclusion, the optimization of the in ovo delivery of carvacrol resulted in that early injection (E12) had negative effects on hatchability and should be avoided. The findings also suggest that using a nonionic surfactant was crucial for an effective delivery of carvacrol in ovo and the migration from amniotic fluid to yolk within 3 h. In addition, carvacrol's persistence in yolk may serve as a route for delivery into the gastrointestinal tract via the yolk stalk during the peri-hatching phase, potentially influencing gut development.

Níveis de energia metabolizável e proteína bruta sobre a taxa de postura e a qualidade de ovos de codornas em fase de postura

ABSTRACT: This study evaluated the zootechnical performance of 192 laying quails, receiving diets with different levels of crude protein (18 and 19%) and metabolizable energy (2,500, 2,600, 2,700 and 2,800 kcal/kg), in a 2 x 4 factorial arrangement. The experiment consists of four experimental periods of 28 days each, where feed intake (g/bird), feed conversion (by dozens of eggs and egg mass), laying rate, weight and mass of eggs and indices of egg quality (yolk, shell and albumen content, shell thickness, Haugh unit). Results indicated that reducing feed energy levels to 2,500 and 2,600 kcal/kg increased feed intake (P &lt; 0.05). However, reducing protein levels to 18% did not change (P &gt; 0.05) feed intake. No differences (P &gt; 0.05) were observed in laying rate, feed conversion per dozen eggs and egg mass, and egg quality indices, in relation to energy or protein levels. There were no interactions between dietary energy and protein levels. In conclusion, the reduction of metabolizable energy levels to 2,500 kcal/kg and crude protein to 18% in diets for laying quails, from 52 to 68 weeks of age, is a viable alternative to reduce production costs, without harming performance and egg quality.

The Level of Fat- and Water-Soluble Antioxidants in Eggs of Free-Range Geese during a Production Season

In this investigation, egg yolk and egg white water and fat-soluble antioxidant concentrations of geese eggs were determined during a production season according to months and weeks. Breeders consumed 100 g commercial layer feed per day during a production season. The farm was located at a semi-open prison of the Ministry of Justice in Van city. Fat-soluble (vitamin A, E, total and individual carotene) of egg yolk and water-soluble (ascorbic acid and GSH) antioxidants of egg white of geese were measured in February, March, April and May per week gazed in pasture conditions. Roche Yolk Color Fun (RYCF) values and Minolta (L* brightness, a* redness, and b* yellowness) values varied according to months and statistically significant differences were observed (p &amp;lt;0.05). RYCF, a * redness, and b *yellowness values were the lowest in February and L* brightness values were the highest in February (p &amp;lt;0.001). According to months (February-May), the egg yolk concentration of vitamin A (retinol) were 3.05±0.11, 1.84±0.10, 1.93±0.09, 2.84±0.19 µg g-1, total vitamin E were 26.87±1.80, 25.07±1.64, 38.16±1.71, 34.30±1.89 µg g-1, and total carotene were 15.49±1.44, 19.50±1.79, 42.39±1.99, 44.30±2.03 µg g-1 (p &amp;lt;0.05), respectively. In this study, lutein, cis-lutein, zeaxanthin, apoester, canthaxanthin, and beta-carotene were identified as individual carotene in goose egg yolks. Glutathione (GSH) and Vitamin C or ascorbic acid (AA) were detected in geese eggs white in the last two weeks of February and four weeks of March, April, and May. The results were recorded as: 0.91±0.14, 1.83±0.19, 2.69±0.15, 1.97±0.09 µg g-1 for AA and 7.71±1.86, 33.22±2.14, 45.37±2.41, 38.75±1.50 µg g-1 for GSH respectively. Both water-soluble GSH and AA data were significantly lower in February and were significantly higher in April (p &amp;lt;0.05) compared to other months.

Dynamic Changes in Egg Quality, Heritability and Correlation of These Traits and Yolk Nutrient throughout the Entire Laying Cycle.

Egg quality and nutritional value are becoming increasingly important to consumers, offering a new direction for the development of high-quality eggs. In this study, we conducted a comprehensive analysis of egg quality and nutrient profiles in native breeds at different ages, integrating pedigree data. Our results reveal dynamic changes in egg qualities, stronger associations among eggshell-related traits, and the effect of onset production and body weight on egg qualities. The heritability of different traits was estimated, ranging from 0.05 to 0.62. Subsequently, we elucidated that the moisture and nutritional content in the egg yolk were not influenced by the percentage of yolk but were indeed subject to age regulation. There was a notable decrease in moisture, an elevation in crude fat, and an increase in the diversity of fatty acids of yolk with advancing age. In summary, investigating the trends and interrelationships in egg quality, nutrient content, and heritability across the whole laying cycle offers valuable insights for breeders to optimize feeding management strategies and aids consumers in meeting their expectations of egg quality.

The Effect of Low Temperature on Laying Performance and Physiological Stress Responses in Laying Hens.

The present study investigated the effect of low temperature on laying performance, egg quality, body temperature, yolk malondialdehyde, yolk corticosterone, and serum biochemistry in laying hens. A total of 40 laying hens (Hy-Line Brown) aged 36 weeks were housed in one of two environmental chambers kept at 12 ± 4.5 °C (low temperature) or 24 ± 3 °C (normal temperature) for 4 weeks. Low vs. normal temperature significantly increased (p < 0.05) live body weight, feed intake, and feed conversion ratio in laying hens. Skin surface temperature, but not rectal temperature, was decreased in laying hens exposed to low vs. normal temperature. Hens exposed to low temperature laid an intense eggshell color compared with those raised in a normal temperature. Malondialdehyde concentrations in yolk were increased in low-temperature-exposed laying hens compared with those at normal temperature conditions, but this effect was only noted on day 7, post the low-temperature exposure (p = 0.04). Finally, low vs. normal temperature increased the concentrations of total cholesterol and triglyceride in serum. Collectively, this study indicates that exposure to low temperature in laying hens initially disrupted antioxidant system and altered lipid metabolism in laying hens without inducing stress responses.

Incubation as a driver of maternal effects: Temperature influences levels of yolk maternally derived 5α-dihydrotestosterone

In birds, maternal hormones deposited into eggs in response to environmental stimuli can impact offspring phenotype. Although less studied, environmental conditions can also influence females’ incubation behavior, which might play a role in regulating embryo exposure to maternal hormones through changes in incubation temperature that affect the activity of the enzymes responsible for converting testosterone (T) to 5α-dihydrotestosterone (DHT) or estradiol. Here, we tested the hypothesis that the initial T content of the yolk and incubation temperature determine exposure to T metabolites during early embryo development. In the Japanese quail (Coturnix japonica), we experimentally manipulated yolk T and incubation temperature (38° C versus 36° C) and analyzed DHT and estradiol titers on day four of incubation. We found that eggs with experimentally increased T and those incubated at 36° C showed higher DHT concentration in egg yolk (with no synergistic effect of the two treatments). Estradiol titers were not affected by T manipulation or incubation temperature. Our study suggests that incubation temperature influences DHT titers and may act as an understudied source of maternal influence on offspring phenotype.

Effects of Enriched-in-Oleuropein Olive Leaf Extract Dietary Supplementation on Egg Quality and Antioxidant Parameters in Laying Hens.

The objective of the present study was to evaluate the effects of an olive leaf extract obtained with an up-to-date laboratory method, when supplemented at different levels in laying hens' diets, on egg quality, egg yolk antioxidant parameters, fatty acid content, and liver pathology characteristics. Thus, 96 laying hens of the ISA-Brown breed were allocated to 48 experimental cages with two hens in each cage, resulting in 12 replicates per treatment. Treatments were: T1 (Control: basal diet); T2 (1% olive leaf extract); T3 (2.5% olive leaf extract); T4 (Positive control: 0.1% encapsulated oregano oil). Eggshell weight and thickness were improved in all treatments compared to the control, with T2 being significantly higher till the end of the experiment (p < 0.001). Egg yolk MDA content was lower for the T2 and T4 groups, while total phenol content and Haugh units were greater in the T2. The most improved fatty acid profile was the one of T3 yolks. The α-tocopherol yolk content was higher in all groups compared to T1. No effect was observed on cholesterol content at any treatment. Based on the findings, it can be inferred that the inclusion of olive leaf extract at a concentration of 1% in the diet leads to enhancements in specific egg quality attributes, accompanied by an augmentation of the antioxidant capacity.

Interventional effect of compound sugar and salt on the thermal instability behavior of liquid egg yolk.

In this study, the influence of compound sugar (glucose, sucrose, trehalose, and arabinose) and compound sugar and salt (glucose, sucrose, trehalose, arabinose, and NaCl) on the thermal stability of heat-treated liquid egg yolk was explored. The results showed that the addition of 4% compound sugar or 4% compound sugar salt could significantly enhance the heat resistance of liquid egg yolk and increase the denaturation temperature of liquid egg yolk to above 77°C. Moreover, the addition of sugar and salt could improve the functional properties of liquid egg yolk to varying degrees, allowing it to maintain excellent emulsification and soluble protein content after heat treatment. Further analysis using Fourier transform infrared spectroscopy showed that the increase in α-helix content in liquid egg yolk treated with sugar salt also contributes to improving the thermal stability of egg yolk. The method of inhibiting egg yolk aggregation caused by heat treatment provided in this study provides a selective method and theoretical basis for the commercial production of heat-resistant liquid egg yolk.

Evolutionary dynamics of whole-body regeneration across planarian flatworms

Regenerative abilities vary dramatically across animals. Even amongst planarian flatworms, well-known for complete regeneration from tiny body fragments, some species have restricted regeneration abilities while others are almost entirely regeneration incompetent. Here, we assemble a diverse live collection of 40 planarian species to probe the evolution of head regeneration in the group. Combining quantification of species-specific head-regeneration abilities with a comprehensive transcriptome-based phylogeny reconstruction, we show multiple independent transitions between robust whole-body regeneration and restricted regeneration in freshwater species. RNA-mediated genetic interference inhibition of canonical Wnt signalling in RNA-mediated genetic interference-sensitive species bypassed all head-regeneration defects, suggesting that the Wnt pathway is linked to the emergence of planarian regeneration defects. Our finding that Wnt signalling has multiple roles in the reproductive system of the model species Schmidtea mediterranea raises the possibility that a trade-off between egg-laying, asexual reproduction by fission/regeneration and Wnt signalling drives regenerative trait evolution. Although quantitative comparisons of Wnt signalling levels, yolk content and reproductive strategy across our species collection remained inconclusive, they revealed divergent Wnt signalling roles in the reproductive system of planarians. Altogether, our study establishes planarians as a model taxon for comparative regeneration research and presents a framework for the mechanistic evolution of regenerative abilities.