Structure and age-dependent development of the turkey liver: a comparative study of a highly selected meat-type and a wild-type turkey line

Gastrointestinal Tract Morphometrics and Content of Commercial and Indigenous Chicken Breeds with Differing Ranging Profiles

Optimal development of the gut is important for nutrient absorption and for poultry to resist diseases. The aim of the study was to compare gastrointestinal tract morphometrics, small intestine microstructure, as well as the amount of pasture matter and feed ingested by the birds with outdoor access presenting either an outdoor-preferring, moderate-outdoor or indoor-preferring ranging profile. Sixty non-beak trimmed birds per strain: broiler hybrid Sasso and Polish indigenous green-legged partridge were housed from week 5 to 10 in groups of 10, under conditions of EU organic meat chicken production. Pens with outdoor ranges were video recorded, to obtain frequencies of the birds' range use. Statistical analysis was conducted applying generalized linear mixed models, applying the ranging profile as a fixed effect and pen as a random factor. The weight of the pasture matter in bird crops was the highest in moderate-outdoor profiled green-legged partridges, as compared to other ranging profiles (p = 0.04). In Sasso, villi in the small intestines were significantly higher in the outdoor-preferring compared to indoor-preferring profiled birds (p = 0.04), while their area was larger in the outdoor-preferring Sasso birds (p = 0.01). The level of development of the gastrointestinal tract and its content may be a potential indicator of the birds' ranging profile and forage consumption.

Early Nutrition with Different Diets Composition versus Fasting on Immunity-Related Gene Expression and Histomorphology of Digestive and Lymphoid Organs of Layer-Type Chicks

Simple Summary

With the continuous improvement in the progress of poultry industry, a better understanding of the avian immune system is necessary. A prolonged holding period (36–72 h), along with a delay in access to feed and/or water post-hatching, has a negative influence on performance, intestinal histomorphology, and the immune system development of chicks. Therefore, the present study aimed to investigate the effect of early feeding with different diet composition or delayed feeding during the first 72 h of chick’s life on the expression of immunity-related genes and histomorphology of digestive and lymphoid organs of layer-type chicks. Early nutrition post-hatching had no negative effect on the development of the lymphoid and digestive organs in chicks. Histomorphological examination revealed an increase in cortex and cortex:medulla of thymus and bursa in the early fed groups compared to the fasted ones, with resultant impacts on the primary lymphoid organs. Higher germinal center areas and white pulp of the spleen were recorded in the early fed chicks, implying augmented proliferation and maturation of B cells in the secondary lymphoid organs. In the liver, a strong positive reaction to Best’s carmine stain in the early fed groups, indicating that the liver of these chicks had numerous glycogen granules in the cytoplasm of hepatocytes. The expression levels of splenic-immunity related genes were up-regulated in most of the early fed chicks at 14 day of age. Our findings suggested that early feeding post-hatch can modify the splenic-immunity related genes and modulate the histomorphology of the digestive (liver and proventriculus) and lymphoid organ in layer-type chicks during the early life post-hatching.

Abstract

Early feeding post-hatching (EFPH) can impact the immune response and modify the immunity-related gene expression. Therefore, we aimed to examine the effects of EFPH with different diets composition versus fasting during the first 72 h of chick’s life on the histomorphological structures of the liver, proventriculus, central and peripheral lymphoid organs, and immunity-related genes in layer-type chicks during the brooding period. A total of 400 chicks were randomly allotted into 4 groups with 4 replicates each. The experimental groups during the first 72 h of life were: feed and water deprivation (control, T1), feeding a starter layer diet (20% CP and 11.84 MJ/kg ME, T2), feeding a starter layer diet contained 3% molasses in its composition (20% CP and 11.81 MJ/kg ME; T3), and feeding a starter broiler diet (23% CP and 12.68 MJ/kg ME, T4). After the first 72 h of chick’s life, all chicks were fed ad libitum the T2 diet. EFPH had no negative effect on the development of the lymphoid or digestive organs in chicks. Greater relative weights of the spleen and bursa of Fabricius (p < 0.05) were observed in the early fed chicks compared to control at day 14 of age. Histomorphological examination revealed an increase (p < 0.05) in thymus cortex and cortex:medulla in the T3 and T4 groups compared to the fasted ones at day 28 of age. Pelicae height, follicular width, cortex, and cortex:medulla of bursa were improved (p < 0.01) in the fed groups compared to fasted chicks, with resultant influences on the primary lymphoid organs. Compared to control, higher germinal center areas and white pulp of the spleen (p < 0.05) were recorded in the early fed chicks, implying augmented proliferation and maturation of B cells in the secondary lymphoid organs. In the liver, a strong positive reaction to Best’s carmine stain in the early fed groups, indicating that the liver of these chicks had numerous glycogen granules or greater glycogen density in the cytoplasm of hepatocytes. There was a significant enhancement in the proventriculus mucosal and gland thickness, as well as fold height (p < 0.05) in the early fed chicks. The expression levels of splenic Toll-like receptor 2, interleukin 4, tumor necrosis factor α, and interferon gamma were up-regulated (p < 0.01) in most of the early fed chicks (T2, T3, and T4) compared to fasted ones at 14 day of age. In conclusion, EFPH could modify the splenic-immunity related genes and modulate the histomorphology of the digestive (liver and proventriculus) and lymphoid organs in layer-type chicks during the brooding period.

Suitability of Slower Growing Commercial Turkey Strains for Organic Husbandry in Terms of Animal Welfare and Performance

Intensive turkey production with fast growing strains is often critically discussed regarding animal welfare problems. Studies evaluating the welfare status of both organic and less intensive selected turkey strains are limited, except in the slightly slower growing Kelly Broad Breast Bronze (Kelly). The aim of this study was to assess the welfare of turkeys from two strains with further decreased growth rate, Hockenhull Large Bronze (HoBr) and Hockenhull Black (HoBl), in comparison to Kelly under commercial organic conditions with 100% organic feed. Altogether 844 non-beak-trimmed male turkeys (274-288 per line) were reared and fattened in three replications with each six groups. On group level, use of resources in the 7, 16, and 25th week of life, mortality and feed conversion were recorded. Each bird was assessed with regard to plumage and skin condition as indicators of agonistic interactions, cannibalism and feather pecking, with regard to leg health, footpad, breast skin condition and, as performance indicators, live and carcass weight, utilization, daily weight gain and weights of valuable meat parts. The significantly slower growing HoBl showed slightly fewer malposition of the legs, reduced injury rates and less breast buttons, but a higher susceptibility to footpad dermatitis than Kelly turkeys. HoBr with a similar growth rate compared to Kelly had slightly more problems concerning walking ability and plumage damage, but also less breast buttons than Kelly turkeys. However, effect sizes were negligible (Φ < 0.10), except for the higher occurrence of footpad dermatitis and the reduced number of breast buttons in HoBl with small effect sizes (Φ = 0.20-0.24). Use of resources, prevalence of breast blisters and mortality, were not statistically different, although mortality rate was numerically lower in HoBl. Thus, for none of the studied strains clear benefits or disadvantages in terms of the birds' predisposition for welfare problems could be identified. Overall, prevalences of animal welfare problems were mostly lower than in comparable studies while performances were comparatively high. Therefore, turkeys from the studied strains appear to be suitable for organic rearing and fattening with 100% organic feed, given a good management.

Hepatic lipidosis in fattening turkeys: A review

The conditions on turkey fattening farms, including management, housing, and feeding, have been constantly improved recently in favour of animal health. Many studies deal scientifically with poultry health. However, specifically concerning liver health, there are still open questions regarding the influence of dietary factors on the metabolism and function of the liver. Consideration of the factors that could influence and alter liver metabolism is therefore of critical relevance. The liver, as a major metabolic organ, is the main site of fat synthesis in turkeys. Under certain conditions, fat can excessively accumulate in the liver and adversely affect the birds’ health. The so-called hepatic lipidosis (HL) in fattening turkeys has been known for years. This disease has unacceptable economic and animal welfare impacts, with high animal losses up to 15% within only a few days. To date, little is known about the causes and the metabolic changes in fattening turkeys leading to HL despite the increasing focus on health management and animal welfare. To understand what is different in turkeys compared to other species, it is necessary to discuss the metabolism of the liver in more detail, including HL-associated gross and microscopic lesions. In the current review, aspects of liver structure and lipid metabolism with special regard to lipogenesis are explained to discuss all dietary factors attributing to the development and prevention of HL. As part of the prevention of the HL, dietetics measures can be helpful in the future.

Age-Related Changes in Serum Lipid Levels, Hepatic Morphology, Antioxidant Status, Lipid Metabolism Related Gene Expression and Enzyme Activities of Domestic Pigeon Squabs (Columba livia)

The objective of this study was to evaluate the age-related changes in antioxidant status and the lipid metabolism of pigeon squabs (Columba livia), by determining the BW, antioxidant indices, serum lipid levels, lipid metabolism-related enzyme activities, lipid metabolism-related gene expression, and liver morphology in squabs. Ten squabs were randomly selected and sampled on the day of hatching (DOH), days 7 (D7), 14 (D14) and 21 (D21) post-hatch, respectively. The results showed that BW of squabs increased linearly from DOH to D21. The minimum fold of BW gain was observed in the phase from D14 to D21. Serum triglyceride and free fatty acid levels displayed linear and quadratic trends as age increased, with these maximum responses in D14. Serum low-density lipoprotein cholesterol level responded to age linearly and quadratically with the minimum in D14. Serum high-density lipoprotein cholesterol level and the ratio of high-density lipoprotein cholesterol to low-density lipoprotein cholesterol increased linearly with age, whereas the very low-density lipoprotein cholesterol level decreased linearly. The activities of glutathione peroxidase, catalase, and superoxide dismutase in liver displayed linear and quadratic trends as age increased, with these minimum responses in D14. Hepatic malondialdehyde concentration responded to age linearly and quadratically, with the maximum in D14. Activities of lipoprotein lipase, hepatic lipase, and 3-hydroxy-3-methyl glutaryl coenzyme A reductase in liver responded to age linearly and quadratically, with these minimum responses in D14. Hepatic hormone-sensitive lipase activity displayed linear and quadratic trends as age increased with the maximum in D14. Hepatic acetyl CoA carboxylase activity on D14 was significantly lower than squabs on DOH and D7. Hepatic carnitine palmitoyltransferase 1 mRNA expression responded to age linearly and quadratically, with minimum response in D14. Hepatic mRNA expression of acetyl CoA carboxylase and fatty acid synthetase increased linearly with age. Hepatic Oil-Red-O staining area displayed a quadratic trend as age increased, with the maximum response in D14. In conclusion, the phase from DOH to D14 was a crucial development stage for growth, antioxidant status and lipid metabolism in pigeon squabs. The results suggest it is better to take nutritional manipulation in squabs before D14.

Structure and age-dependent growth of the chicken liver together with liver fat quantification: A comparison between a dual-purpose and a broiler chicken line

Rearing dual-purpose chickens is a practicable approach to avoid culling one-day-old male layer chicks. The present study examined the impact of a conventional fattening diet on the liver of a novel dual-purpose chicken line (Lohmann Dual, LD) in comparison to a broiler (Ross 308) chicken line. Age-related changes of structure and lipid content of the liver were assessed. One hundred twenty and newly hatched chicks (LD = 66, Ross = 54) were kept under the same husbandry conditions and fed a commercial diet for 5 weeks for Ross and 9 weeks for LD. Six birds of each line were examined weekly. Their body weight (BW) and liver mass were recorded. Microscopic structure and ultrastructure of the liver were investigated and the liver lipid content was measured using a pre-validated method. During the study period, liver mass increased with age, while normalized liver mass decreased. Furthermore, liver mass of Ross birds was greater than that of LD birds of the same BW. Overall, no significant differences were observed in the hepatic structure or ultrastructure between the two chicken lines. The hepatic lymphatic aggregations were without fibrous capsules and their number and area increased throughout the first week, then the values began to fluctuate with age in both chicken lines. The changes in the liver lipid content of the two chicken lines were within the normal physiological range over the term of the study. The liver lipid content correlated negatively with age and body weight in both lines. It was the highest on the first day then decreased until day 7 and thereafter did not change in both chicken lines. However, given the same body weight, the Ross chickens had a 9% greater liver lipid content than LD chickens. It is concluded that there is no apparent adverse effect of a high-energy diet on the liver of LD chickens.

Unravelling fatty liver haemorrhagic syndrome: 2. Inflammation and pathophysiology

To study the role of inflammation in the pathophysiology of the fatty liver haemorrhagic syndrome (FLHS), mature laying hens were treated with oestrogen (β-oestradiol-17-dipropionate or E₂) and challenged with lipopolysaccharide (LPS). Oestrogen injections induced FLHS, but the incidence and severity of the condition was increased with a combination of E₂ & LPS. Hepatic mRNA levels of the genes encoding key regulators of inflammation, such as interleukin-1β (IL-1β), interleukin-6 (IL-6) and interleukin-18 (IL-18), were evaluated. The expression of IL-6 mRNA in hepatocytes of all treated groups (E₂, LPS and E₂ & LPS hens) was elevated from 6-fold to 56-fold (P < 0.01), when compared to baseline and control values, with the highest fold change at 3 h post-treatment. The mRNA levels for IL-1β were better expressed at 24 h post-treatments with E₂, LPS and E₂ & LPS. The expression of IL-18 mRNA in the liver tissue was lower than IL-1β and IL-6 mRNA in all treated birds. At 24 h post-treatment, total white blood cell (WBC) counts and fibrinogen levels were elevated (P < 0.05) in E₂-, LPS- and E₂- & LPS-treated hens. Histologically, livers of hens from E₂- and E₂- & LPS-treated groups revealed inflammatory alterations with areas showing mononuclear aggregations, vacuolar fatty degeneration of hepatocytes, and increased sinusoidal congestion and haemorrhages. It was concluded that liver lipid accumulation and injury were associated with incidences of local (hepatic) and systemic inflammation, which could have initiated liver blood vessel and capsule rupture and, subsequently, the onset of FLHS.

Comparison of the gastrointestinal tract of a dual-purpose to a broiler chicken line: A qualitative and quantitative macroscopic and microscopic study

The transition to using dual-purpose chickens is an alternative to killing male hatchlings of high performance egg-laying chickens. This study aimed to compare the gastrointestinal tract of a recently developed genetic line of dual purpose male chicken, Lohmann Dual (LD), with that of a broiler line, Ross 308. Eighty birds from each line were grown until they reached an average body weight 2000 g (5 weeks for Ross and 9 for LD birds). Six birds of each line were sampled weekly. Body weight (BW), normalized mass of gastrointestinal segments and relative length of intestine were determined. Histologically the villus height, epithelium height, crypt depth, mucosal enlargement factor and the tunica muscularis thickness were measured in jejunum and ileum. Data were regressed against body weight and genetic line. Jejunal enterocyte microvilli and junctional complexes length were measured. Normalized mass and relative length of the gastrointestinal segments were greater in LD birds than in Ross birds at all ages. After day 7 these decreased steadily over the lifetime of the birds in both genetic lines. The growth curves of the gastrointestinal segments of the LD birds were similar to those of the Ross birds. In birds of the same BW, LD birds had a significantly heavier gizzard, shorter intestine, higher jejunal villi, thicker ileal tunica muscularis and smaller ileal mucosal enlargement factor than were found in Ross birds. The large gizzard in LD chickens presumably increases the degree of food processing and enhances availability of nutrients in the orad part of the intestine leading to a lower nutrient concentration and a smaller absorption surface area in the ileum of the LD compared to the Ross chickens. The anatomical differences between the two lines are important criteria for further selection and should be considered in their feeding management.

Fat content, fatty acid pattern and iron content in livers of turkeys with hepatic lipidosis

BACKGROUND

The so-called "hepatic lipidosis" in turkeys is an acute progressive disease associated with a high mortality rate in a very short time. Dead animals show a massive fatty degeneration of the liver. The cause is still unclear. Previous findings suggest that there may be parallels to human non-alcoholic fatty liver disease. The object of the study was to examine the changes in the fat contents, the fatty acid composition and the iron content in livers of animals, which have died from hepatic lipidosis.

METHODS

The conspicuous livers (n = 85) were collected from 20 flocks where the phenomenon of massive increased animal losses accompanied by marked macroscopically visible pathological liver steatosis suddenly occurred. For comparison and as a reference, livers (n = 16) of two healthy flocks were taken. Healthy and diseased flocks were fed identical diets concerning official nutrient recommendations and were operating under standardized, comparable conventional conditions.

RESULTS

Compared to livers of healthy animals, in the livers of turkeys died from hepatic lipidosis there were found massively increased fat levels (130 ± 33.2 vs. 324 ± 101 g/kg dry matter-DM). In all fatty livers, different fatty acids concentrations were present in significantly increased concentrations compared to controls (palmitic acid: 104 g/kg DM, +345%; palmitoleic acid: 18.0 g/kg DM, + 570%; oleic acid: 115 g/kg DM, +437%). Fatty acids concentrations relevant for liver metabolism and inflammation were significantly reduced (arachidonic acid: 2.92 g/kg DM, -66.6%; eicosapentaenoic acid: 0.141 g/kg DM, -78.3%; docosahexaenoic acid: 0.227 g/kg DM, -90.4%). The ratio of certain fatty acids to one another between control and case livers changed analogously to liver diseases in humans (e.g.: C18:0/C16:0 - 0.913 against 0.311; C16:1n7/C16:0 - 0.090 against 0.165; C18:1/C18:0 - 0.938 against 4.03). The iron content in the liver tissue also increased massively (271 ± 51.5 vs 712 ± 214 mg/kg DM).

CONCLUSION

The hepatic lipidosis has a massive impact on the lipid content, the lipid composition and the iron content in the liver. The character of the metabolic disorder includes parallels to the non-alcoholic steatohepatitis in humans.

Comparative Quantitative Studies on the Microvasculature of the Heart of a Highly Selected Meat-Type and a Wild-Type Turkey Line

In this study the macroscopic and microscopic structure of the heart of a fast growing, meat-type turkey line (British United turkeys BUT Big 6) and a wild-type turkey line (Canadian Wild turkey) were compared. At 8 and 16 weeks of age, 10 birds of each genotype and sex were sampled. The body mass and heart mass of the meat-type turkey both increased at a faster rate than those of the wild-type turkey. However in both turkey lines, the relative heart mass decreased slightly with age, the decrease was statistically significant only in the male turkeys. Furthermore meat-type turkeys had a significantly (p < 0.01) lower relative heart mass and relative thickness of the left ventricle compared to the wild-type turkeys of the same age. The wild-type turkeys showed no significant change in the size of cardiomyocytes (cross sectional area and diameter) from 8 weeks to 16 weeks. In contrast, the size of cardiomyocytes increased significantly (p < 0.001) with age in the meat-type turkeys. The number of capillaries in the left ventricular wall increased significantly (p < 0.001) in wild-type turkeys from 2351 per mm² at the age of 8 weeks to 2843 per mm² at 16 weeks. However, in the meat-type turkeys there were no significant changes, capillary numbers being 2989 per mm² at age 8 weeks and 2915 per mm² at age 16 weeks. Correspondingly the area occupied by capillaries in the myocardium increased in wild-type turkeys from 8.59% at the age of 8 weeks to 9.15% at 16 weeks, whereas in meat-type turkeys this area decreased from 10.4% at 8 weeks to 9.95% at 16 weeks. Our results indicate a mismatch in development between body mass and heart mass and a compromised cardiac capillary density and architecture in the meat-type turkeys in comparison to the wild-type turkeys.