Effects of genotype, sex, and feed restriction on the biochemical composition of chicken preen gland secretions and their implications for commercial poultry production.

Preen gland secretions spread on the feathers contain various chemical compounds dominated by fatty acids (FAs) and volatile organic compounds (VOCs). These chemicals may significantly affect plumage condition, microbial and ectoparasitic load on feathers, and chemical communication of birds. However, how chemical composition of preen secretions varies in commercially produced chickens with respect to their genotype, sex, and feeding regime remain largely unknown, as well as the welfare implications for farmed poultry. We found that while polyunsaturated fatty acids in chicken preen secretions differed significantly with genotype (P << 0.001), saturated fatty acids and monounsaturated fatty acids varied with genotype-dependent preen gland volume (P < 0.01). Chickens of meat-type fast-growing Ross 308 genotype had reduced preen gland volume and lower proportions of all FA categories in their preen secretions compared with dual-purpose slow-growing ISA Dual chickens. A total of 34 FAs and 77 VOCs with tens of unique FAs were detected in preen secretions of both genotypes. While differences in the relative proportion of 6 of the 10 most dominant VOCs in chicken preen gland secretions were related to genotype (P < 0.001), only 1 of the 10 most dominant VOCs showed a sex effect (P < 0.01), and only 2 of the 10 most dominant VOCs showed a genotype-dependent effect of feed restriction (P < 0.05). Feed restriction had no effect on the relative proportion of any of the FAs in chicken preen gland secretions. Moreover, we found that meat-type Ross 308 preen secretions were dominated by VOCs, which are proven attractants for poultry red mite and may also increase infestation with other ectoparasites and negatively influence overall odor-mediated intraspecific communication and welfare. This study shows that no feeding management, but long-term genetic selection in commercial breeding may be the main cause of the differences in the biochemistry and function of chicken preen secretions. This might have negative consequences for chemosignaling, antiparasitic, and antimicrobial potential of preen secretions and can lead to increased susceptibility to ectoparasites, plumage care disorders, and can affect the overall condition, welfare, and productivity of commercially bred chickens. Selection-induced preen gland impairments must therefore be considered and compensated by proper management of the chicken farm and increased care about animal well-being.

The preen gland is the largest sebaceous gland in birds, which produces a secretion that is spread on the feathers during comfort behavior. The secretion of the preen gland contains various chemical compounds that are responsible for mechanical, antimicrobial, and antiparasitic protection of the plumage and probably also for chemical communication between birds. However, there are only a limited number of studies on the composition and function of preen secretions in wild birds and only limited evidence in poultry. In this study, we compared the chemical composition of preen secretions in fast-growing meat-type and slow-growing dual-purpose chickens and evaluated the effect of sex, body condition, and feeding regime on preen secretion composition. Fast-growing meat-type chickens had smaller preen glands and lower proportions of all analyzed compounds in preen secretions compared to slow-growing dual-purpose chickens. In addition, compounds that are proven attractants for a poultry-threatening ectoparasite, poultry red mite, were predominant in the secretions of meat-type chickens. This study is the first to show that genetically distinct breeds of chickens can differ significantly in the biochemistry of preen secretions, which can influence susceptibility to ectoparasites, plumage care disorders, and can affect the overall condition, well-being, and productivity of commercially raised chickens.

The potential role of feed restriction on productivity, carcass composition, meat quality, and muscle fibre properties of growing rabbits: A review.

After weaning rabbits, two post-weaning feed restriction (FR) programs are used: a quantitative FR (quantity of feed-limited or time-limited access to feed) or a qualitative FR (modification of diet composition in particularly protein, energy or fibre). Application of post-weaning FR has potential to control post-weaning digestive disorders, and early lower growth rates may be compensated for by later compensatory growth. FR strategies also have potential to enhance feed conversion ratio and reduce carcass fatness. FR may also influence meat chemical composition and physical quality characteristics via controlling the morphological and biochemical properties of muscle fibres. The purpose of this review was to shed light on recent findings regarding benefits of FR on productive performance, carcass characteristics, meat quality characteristics, and muscle fibre properties in growing rabbits.

The effect of feed restriction, sex and age on the carcass composition and meat quality of nutrias (Myocastor coypus).

The objective of the study was to evaluate the effect of quantitative feed restriction on the carcass composition and physical, chemical, histochemical and sensory properties of meat from male and female nutria at the end of the feed restriction and fattening period. In the experiment, from two to eight months of age, males and females were divided into two groups: one group was fed ad libitum throughout the experiment, and the second group was restricted to two weeks (from 11 to 12 weeks of age). The restricted nutrias received 75% ad libitum feeding. The significant interaction among feed restriction, sex and age was revealed only in the cross-sectional area of all muscle fiber types. Age was the main factor affecting carcass composition and meat quality characteristics. Sex-related differences in carcass composition and some sensory attributes and feed restriction-related differences in carcass composition were observed.

Guinea fowl (Numida meleagris) eggs and free-range housing: a convenient alternative to laying hens' eggs in terms of food safety?

The aim of this study was to evaluate the impact of the genotype (guinea fowl, native breed Leghorn, and commercial hybrid hens), storage time (0, 14, 28 d) and storage temperature (fresh, 5, 20°C) on eggshell quality traits and microbiological contamination of eggshell, eggshell membranes, and albumen. A total of 150 hens (50 hens per genotype-divided into 2 equal groups because of the results replication) were used. There were 150 eggs (50 per genotype) used for microbial analysis and 600 eggs used for the analysis of eggshell quality. The effects of genotype, storage time, and storage temperature were observed. Moreover, interactions between these factors were calculated. The significant effect of genotype (P = 0.0001) was found in egg weight, in all observed parameters of eggshell quality (proportion, thickness, strength, surface, and index), eggshell contamination of Escherichia coli (EC) and total number of micro-organisms (TNM), penetration of TNM into eggshell membranes (P = 0.0014), and penetration of TNM into albumen (P = 0.0019). Storage time significantly affected egg weight and all parameters of eggshell quality except the eggshell strength and index. It also significantly affected count of Enterococcus (ENT) on eggshell, TNM in eggshell membranes and TNM in albumen. Storage temperature significantly influenced egg weight (P = 0.0001) and all parameters but eggshell thickness and surface. Regarding the microbial contamination, storage temperature significantly affected a count of ENT on shell, TNM in shell membranes, and TNM in albumen. Concerning significant interactions, the interaction among genotype and storage time was found significant (P = 0.0148). Fresh and 28-day-old commercial hybrid eggs were the most contaminated, whereas guinea fowl eggs (fresh and 14 d old) and Leghorn hen eggs (fresh, 14, 28 d old) had the lowest level of contamination by EC. When looking for an alternative to laying hens, guinea fowls should be taken into consideration due to their higher resistance to diseases, ability of adaptation to different environmental conditions, and especially in terms of eggshell quality and therefore egg safety.

Combined Effect of Genotype, Housing System, and Calcium on Performance and Eggshell Quality of Laying Hens.

The objective of this study was to evaluate hen performance and eggshell quality response to genotype, housing system, and feed calcium (Ca) level. For this purpose, an experiment was conducted on 360 laying hens of ISA Brown, Bovans Brown (commercial hybrids), and Moravia BSL (traditional Czech hybrid). Laying hens were kept in enriched cages and on littered floor and fed similar feed mixtures with different Ca content (3.00% vs. 3.50%). In terms of hen performance, ISA Brown had the highest egg production (84.2%) compared to Moravia BSL (74.3%) and Bovans Brown (71.4%). Regarding eggshell quality, Bovans Brown showed the highest values of all eggshell quality parameters. Increasing feed Ca level augmented egg production (p ≤ 0.001) but had no effect on other performance parameters. Except eggshell thickness, all eggshell quality parameters were affected by the three-way interaction of genotype, housing, and Ca. Bovans Brown, which had the strongest eggshells (5089 g/cm2) when housed on a littered floor system and fed 3.00% Ca, while Moravia BSL housed on a littered floor had the weakest eggshells (4236 g/cm2) at 3.50% Ca. The study pointed out the importance of the interactions between studied factors on performance and eggshell quality compared to an individual factor effect.

Fatty acid composition of goose meat depending on genotype and sex.

OBJECTIVE: The aim of this study was to compare male and female geese of two contrasting genotypes in terms of fatty acid composition, indexes related to human health, lipid metabolism and oxidative stability of the meat. METHODS: The experiment was carried out on total of 120 geese of two different genotypes; the native breed Czech goose (CG) and commercial hybrid Novohradska goose (NG). One-d-old goslings were divided into 4 groups according to genotype and sex, and 8 birds from each group were slaughtered at 8 weeks of age. RESULTS: The effects of the interactions between genotype and sex were observed on growth performance and carcass traits. Final body weight (p<0.001), daily weight gain (p<0.001), daily feed intake (p<0.001), slaughter weight (p<0.001), and cold carcass weight (p<0.001) were highest in NG males and lowest in CG females. The meat fatty acid composition results showed effects of both genotype and sex on the total n-6 and the total polyunsaturated fatty acid (PUFA) content, as well as the PUFA n-6/PUFA n-3 ratio. Regarding genotype, the total n-6, the total PUFA content and the PUFA n-6/PUFA n-3 ratio were higher in CG, and higher values were found in females. In terms of the lipid metabolism, Δ5-Δ6 desaturase (p = 0.006) was higher in males. The meat oxidative stability results revealed an interaction between genotype, sex and storage time (p<0.001). The highest (13.85 mg/kg) malondialdehyde content was measured in the meat of CG females after 5 days of storage and was presumably related to a higher PUFA content. CONCLUSION: NG had a relatively higher growth rate and meat oxidative stability, whereas the advantage of CG meat is its favourable fatty acid profile characterized by a higher PUFA content.

The effect of age, genotype and sex on carcass traits, meat quality and sensory attributes of geese.

OBJECTIVE: The aim of this study was to compare carcass traits, meat quality and sensory attributes in two different genotypes of geese according to age and sex. METHODS: The experiment was carried out on 160 birds of two genotypes of geese: the Czech Goose (CG) breed and a Eskildsen Schwer (ES) hybrid. One-d-old goslings were divided into four groups according to genotype and sex. Two dates for slaughtering (at 8 and 16 wk of age of goslings) were undertaken. RESULTS: The slaughter weight, cold carcass weight and dressing percentage were affected by all the studied factors, and significant interactions between age, genotype and sex were detected in the slaughter weight (p<0.001) and cold carcass weight (p = 0.004). The pH was not affected by any of studied factors, whereas in terms of meat colour parameters there were observed significant effects of age on L* and b* value and a significant effect of sex on a* value. The meat fat content was higher (p = 0.002) in ES. Higher score for overall acceptance of goose meat was recorded for ES at both ages compared to CG. CONCLUSION: ES had higher dressing percentage and better sensory attributes, whereas CG exceled in the favourable nutritional value of the meat.

Age-related changes in the carcass yield and meat quality of male and female nutrias (Myocastor coypus) under intensive production system.

The age at which final nutria weight is achieved varies in literature between six and 14months. The aim of this study was to evaluate the growth, carcass composition and meat quality of male and female nutrias between the ages of six and eight months in intensive production system. Sexual dimorphism in growth was observed from three months of age, and in females, growth considerably decreased after six months of age. The dressing-out percentage and the meat color were not affected by the age or sex of nutrias. Dry matter, ether extract and energetic values were significantly higher in females and in older nutrias. The decreasing frequency of type IIA fibers in older nutrias was presumably associated with a conversion of type IIA fibers to type IIB fibers. Nutrias under intensive production system can be slaughtered at six months of age when they reach a high carcass yield and meat quality.