Ramifications of Heat Stress on Rabbit Production and Role of Nutraceuticals in Alleviating Its Negative Impacts: An Updated Review.

Heat stress has become a widespread concern worldwide, which is a major environmental stress that causes substantial economic loss in the rabbit industry. Compared to other agricultural animals, rabbits are more sensitive to heat stress as they have fewer sweat glands and a thicker coat of fur, increasing the heat dissipation complexity. Thus, heat stress hurts rabbits' productivity, meat quality, reproductive performance, antioxidative properties, immune responsiveness, intestinal histomorphology, and microbiome. Nutraceuticals include vitamins, minerals, antioxidants, organic acids, fatty acids, probiotics, prebiotics, synbiotics, enzymes, and medicinal plants due to the possible impacts on maintaining common biological situations, strengthening immune response, and preventing illness, which ultimately led to an increase in productivity. Nutraceuticals have recently attracted a lot of attention to alleviate the adverse impacts of heat stress in rabbit farms. The objective of the current review is to provide acquaintance with the recent findings about the impact of heat stress on rabbit productivity and the advantages of dietary supplementation of nutraceuticals in mitigating it.

Dietary Inclusion of Crickets (Acheta domesticus) and Yellow Mealworm Meal (Tenebrio molitor) in Comparison with Soybean Meal: Effect on the Growth, Total Tract Apparent Digestibility, and Nitrogen Balance of Fattening Rabbits.

Three diets were formulated, i.e., soybean meal (SM diet), adult Acheta domesticus (AD diet), and Tenebrio molitor larvae (TM diet), as the main crude protein (CP) sources. A total of 45 rabbits (Hyplus, weaned at 32 days of age) were divided into three groups (15 per treatment) and fed one of the three diets for 42 days. A higher daily weight gain (p = 0.042), as well as daily feed intake (p = 0.022), was observed in rabbits fed the AD and TM diets than in rabbits fed the SM diet within 21 days after weaning. The coefficients of total tract apparent digestibility (CTTAD) of gross energy were higher (p = 0.001) in rabbits fed the SM diet than in rabbits fed the other diets. The CTTAD of CP (p = 0.040) and starch (p = 0.041) was higher in rabbits fed the SM diet compared to those fed the AD diet. There were non-significantly higher losses of nitrogen in the urine (an average by 0.227 g/day; p = 0.094) in rabbits fed the TM diet than in rabbits fed the other diets. It can be concluded that the growth of rabbits and nitrogen output were not detrimentally affected by the insect meal (AD or TM) used in this study.

The effect of housing system on rabbit growth performance, carcass traits, and meat quality characteristics of different muscles.

The present study analysed the effect of housing system (caged versus penned) on the growth performance, carcass traits, and meat quality of rabbits. The physiochemical quality of five muscles was evaluated, together with the chemical composition and fatty acid profile of the meat from the hind leg. Sensory properties of the longissimus lumborum (LL) was also assessed. The LL yields were higher in caged rabbits. According to the results, meat from rabbits raised in cages had higher b* values for the LL (i.e., meat was yellower) than rabbits raised in pens. In addition, the quadriceps femoris from penned rabbits had higher a* and b* values (i.e., were redder and yellower) than caged rabbits. The MUFAs (18:1 n-9 and 20:1 n-9) and ash contents of the hind leg meat were higher in caged rabbits. In conclusion, while housing system influenced the physiochemical traits of rabbit meat, the sensory properties were not influenced.

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.

Effect of an Outdoor Access System on the Growth Performance, Carcass Characteristics, and Longissimus lumborum Muscle Meat Quality of the Prestice Black-Pied Pig Breed.

The effect of an outdoor-access vs. conventional indoor system on the growth, carcass characteristics, and longissimus lumborum muscle (LL) meat quality was evaluated in 24 Prestice Black-Pied pigs, during the growing-finishing period. Two groups received the same complete diet and were housed separately under conventional indoor conditions, with only one group having full access to pasture (350 m2/pig). The animals showed acceptable growth rates (outdoor vs. indoor, average of 740 g/d vs. 700 g/d), feed intake (average of 2700 g/d), and feed conversion ratios (FCR) (average of 3.3 vs. 3.5). The rearing system significantly affected the fatty acid composition of the LL. Outdoor pigs had lower ratios of n - 6/n - 3 polyunsaturated fatty acids, saturation indexes, atherogenic indexes, and thrombogenic indexes, compared with indoor-raised pigs. No differences were recorded in carcass characteristics, physical meat quality traits (pH45, pH24, drip loss, water holding capacity), or the chemical composition of the meat (crude protein, cholesterol, intramuscular fat, hydroxyproline, and tocopherol). The sensory analysis of grilled LL muscle found that outdoor pigs received lower evaluation scores for tenderness, juiciness, and chewiness, but had a better overall acceptance compared to pigs reared indoors.

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.

Effect of amidated alginate on faecal lipids, serum and hepatic cholesterol in rats fed diets supplemented with fat and cholesterol.

The effect of octadecylamide of alginic acid on serum and hepatic cholesterol, and the faecal output of fat and sterols was examined in female rats fed diets containing cholesterol and palm fat at 10 and 50 g kg-1, respectively. Cholesterol supplementation significantly increased serum and hepatic cholesterol concentrations, and faecal output of cholesterol and coprostanol. Cholesterol and amidated alginate supplementations changed the profile of fatty acids in the faeces. Cholesterol increased molar percentages of saturated fatty acids and amidated alginate reversed this effect. Amidated alginate, supplied at 10, 20 and 40 g kg-1, significantly decreased serum cholesterol from 2.82 to 2.00, 1.95, and 1.63 µmol mL-1, respectively, and significantly decreased hepatic cholesterol from 13.8 to 9.33, 7.81 and 6.3 µmol g-1, respectively. Amidated alginate increased the faecal output of fat and neutral sterols in a dose-dependent manner. In contrast, the output of bile acids was significantly decreased. The faecal outputs of fat and serum cholesterol were negatively correlated. At the highest concentration tested, amidated alginate significantly reduced the serum concentration of triacylglycerols. It can be concluded that amidated alginate is an effective cholesterol-lowering agent and sorbent of dietary fat.

The influences of dried Chicory root and White lupine added to food on jejunal morphology: experimental study.

AIM: The objective of this work was to test the effects of adding dried Chicory root and White lupine food on small bowel morphology and compare it to a standard commercial diet. BACKGROUND: Various commercial gluten-free products, gluten-free raw materials and gluten-free plants are this time available on the food market, but there are still not enough information about their effect on the small bowel morphology. METHODS: Altogether thirty rabbits were used in this study. The control diet (C) contained common feed components. The first experimental diet (E1) contained (per kg) 60 g of dried chicory roots instead of barley, whereas the second experimental diet (E2) was based on white lupine seeds (cv. Amiga; 120 g per kg diet) instead of the soybean meal used in the control diet. The experiment started when the rabbits were 34-days old and lasted until they were 55-days old. At the end, one jejunal small bowel tissue was sampled, and both the heights and depths of the villi and crypts were measured. RESULTS: The highest villi were measured in the E1 (598.99 µm) group, mean in the C (590.30 µm) group and the lowest were in the E2 (563.74 µm) group. The most intense mucin villous positivity was observed in the E2 group, followed by the E1 group, and the weakest positivity was found in the visible C group. CONCLUSION: Chicory root has practical uses in gluten-free industries.

Effect of dietary dehulled white lupine seed supplementation on the growth, carcass traits and chemical, physical and sensory meat quality parameters of growing-fattening rabbits.

This work aimed to extend our current knowledge by obtaining novel information regarding the effect of the dietary inclusion of dehulled white lupine seeds (DWL) on the physical characteristics and sensory qualities of rabbit meat, as well as growth and carcass traits. The DWL diet was compared with a soybean meal-based diet. Feeding the DWL diet to rabbits led to lower Warner-Bratzler shear force values measured in grilled meat samples (Longissimus lumborum muscle) across fibers and this finding was confirmed in the sensory evaluation of texture in terms of higher tenderness and fibrosity of meat samples. No differences were detected by panelists in terms of intensity of aroma, the presence of a flavor typical for cooked meat, or the presence of a flavor typical for rabbit meat. Additionally, saturation and thrombogenic indexes from hind leg meat of rabbits fed the DWL diet were reduced. There was a better feed conversion ratio in rabbits fed the DWL diet.

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.

Comparative study of the hypocholesterolemic and hypolipidemic activity of alginate and amidated alginate in rats.

Alginate is a copolymer of ß-d-mannuronate and α-l-guluronate, which are present in the cell wall of brown algae. The hypocholesterolemic and hypolipidemic activities of alginate and its derivative, which is prepared by a reaction with octadecylamine, were compared in rats fed diets containing cholesterol and palm fat at 10 and 50g/kg, respectively. Amidated alginate at 20g/kg significantly decreased serum cholesterol from 2.93 to 2.00µmol/mL, serum triacylglycerols from 1.66 to 0.92µmol/mL, hepatic cholesterol from 17.5 to 5.9µmol/g, and total hepatic lipids from 67.4 to 51.7mg/g. Alginate at 20g/kg significantly reduced hepatic cholesterol to 13.1µmol/g, but did not influence serum cholesterol, triacylglycerols, and total hepatic lipids. Amidated alginate significantly increased the faecal concentrations of neutral sterols from 98.7 to 122.4µmol/g DM, but decreased faecal concentration of bile acids from 19.4 to 14.0µmol/g DM. In samples of intestinal contents, taurine-conjugated bile acids dominated glycine conjugates. The supplementation of diets with cholesterol significantly increased the expression of hepatic cholesterol 7α-hydroxylase, especially in rats that received cholesterol without alginate or amidated alginate. In conclusion, amidated alginate is an effective hypocholesterolemic agent that is more efficient than its parent polysaccharide.

Relationships between variable time, percentage of food restriction and liver histology: which alternative is the best for non-alcoholic fatty liver disease (NAFLD) prevention?

The objective of this study was to analyse the hepatic effects of food restriction in an experimental rabbit model. The study comprised 105 rabbits divided into 6 groups. The two control groups were fed ad libitum (ADL) during the entire experiment (C1 and C2). The experimental groups were restricted between 42-49 days of age, where the rabbits received 50g (R1) or 65g (R2) of food per rabbit per day. Others were restricted between 35-42 days of age, where the rabbits received 50g (R3) or 65g (R4) of food per rabbit per day. For liver analysis, 5 rabbits per group were slaughtered at the ages of 49, 56, 63, 70 days from the R1, R2 groups and at 42, 49, 70 days from the R3, R4 groups. All animals from the C1 and C2 groups developed steatosis with inflammation. Animals from the R1 and R2 groups developed steatosis without inflammation while in the R3 and R4 groups steatosis was not visible. In C1 and C2 groups we observed mostly fatty deposit accumulations while in the R1, R2, R3 and R4 groups, more PAS-positive material accumulations were visible. Liver steatosis correlated with inflammation development and interstitial tissue growth. These results can be used in clinical praxis as signs of NAFLD progression. Early food restriction had intense effects on liver morphology and it seems promising that similar approaches could be applied as preventive treatment for NAFLD development.

Histological aspects of the small intestine under variable feed restriction: The effects of short and intense restriction on a growing rabbit model.

The objective of this study was to investigate the effect of seven days of feed restriction (between days 42 and 49) on the morphology of the small intestine in experimental rabbit models. Sixty weaned Hyplus rabbits (35 days old) were included in the experiment and split into three groups of 20 rabbits. The first control group (n=20) received feed ad libitum (ADL group), the second (R1) experimental group (n=20) was fed 50 g feed per rabbit per day and the third (R2) experimental group (n=20) received 65 g feed per rabbit per day. Duodenal samples were collected when the rabbits were aged 49, 56, 63 and 70 days. The mean villus height, crypt depth and small intestine length were measured. Significant interactions (P<0.001) between group and age were identified in the villi height and crypt depths. The maximum mean villus height was found in the R2 group in 56-day-old rabbits (643.14 µm), while the minimum was found in the ADL group in 49-day-old rabbits (460.29 µm). The longest (P<0.001) small intestine was measured in the R1 group in 63-day-old rabbits (347.60 cm), while the shortest was measured in the ADL group in 49-day-old rabbits (263.60 cm). The models show that villus height, crypt depth and the length of the small intestine change with the intensity of feed restriction and age.

Histopathological aspects of liver under variable food restriction: has the intense one-week food restriction a protective effect on non-alcoholic-fatty-liver-disease (NAFLD) development?

Non-alcoholic-fatty-liver-disease (NAFLD) is a clinicopathologic entity characterized by a variety of hepatic injury patterns without significant alcohol use. It has a close association with obesity, so treatment includes weight loss, control of insulin sensitivity, interventions directed at inflammation and fibrosis. There is a certain relationship between the grade and duration of food restriction and hepatic function. The objective of this work was to describe the relationship between biochemistry, autoantibodies, insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 3 (IGFBP-3), and liver morphology in experimental rabbit groups with food restriction as compared to controls with ad libitum food (ADL) income. The experiment was performed on a total of 24 rabbits of a weaning age of 25-81 days. The first group (R1) was restricted between 32 and 39 days of age to 50 g of food per rabbit a day. The second group (R2) was also restricted between 32 and 39 days, but the rabbits received 65 g of food per rabbit a day. At the end of the experiment, the blood and liver samples were collected at necropsy. NAFLD has developed in all three groups. There was any autoantibody positivity in all three groups. IGF-I is moderately higher in R1 and R2 group, as compared to the control group (P > 0.05). IGFBP-3 is without statistical significance in all three groups. Alkaline phosphatase (ALP) is the only liver biochemical parameter that has significantly increased following food restriction (P > 0.039). Single one-week restriction has any protective effect on NAFLD development.

Dose-response efficacy and long-term effect of the hypocholesterolemic effect of octadecylpectinamide in rats.

The dose-response efficiency and long-term effect of the hypocholesterolemic effect of octadecylpectinamide was examined in female rats fed diets containing cholesterol at 10 g/kg. In our first experiment, amidated pectin supplied at 20 g/kg, 40 g/kg and 60 g/kg significantly decreased serum cholesterol from 3.32 µmol/ml (control) to 1.23 µmol/ml in a dose-dependent manner. In a second experiment, the hypocholesterolemic effect of amidated pectin supplied at 20 g/kg persisted after 3 months of feeding. In both experiments, the amidated pectin significantly decreased the concentrations of cholesterol in hepatic tissue and triacylglycerols in serum. The serum concentration of aspartate aminotransferase significantly increased in rats fed amidated pectin at 60 g/kg for 4 weeks, and at 20 g/kg for 3 months. In conclusion, amidated pectin at a low dose and used for a period shorter than 3 months might be considered as an effective hypocholesterolemic and lipid-lowering agent that may substitute typical antilipidemic drugs.

Effect of feeding growing-fattening rabbits a diet supplemented with whole white lupin (Lupinus albus cv. Amiga) seeds on fatty acid composition and indexes related to human health in hind leg meat and perirenal fat.

A total of 20 weaned rabbits (33 days old) (10 per treatment) were fed one of two diets that included 150 g of sunflower meal (SF)/kg of diet or 120 g of whole white lupin (WL)/kg of diet for 42 days. The WL diet contained less saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) but more monounsaturated fatty acids (MUFA) than the SF diet. The WL diet significantly decreased SFA and PUFA content, as well as the PUFA n-6/PUFA n-3 ratio and saturation, atherogenic and thrombogenic indexes in hind leg meat. The fatty acid composition in perirenal fat was similar to that of hind leg meat; however, significantly higher MUFA levels were observed in rabbits fed the WL diet. Thus, feeding rabbits the WL diet affected the fatty acid profile of hind leg meat and perirenal fat in a favourable manner.

Effect of Cryptosporidium parvum infection on the absorptive capacity and paracellular permeability of the small intestine in neonatal calves.

Cryptosporidium parvum is recognized as one of the most important pathogens causing enteritis and severe diarrhoea in calves up to 1 month of age. Although the infection may be responsible for some mortality, its impact is mainly associated with the impairment of intestinal functions and lower performance of animals. The aim of this study was to determine the effect of cryptosporidiosis on the intestinal functions in neonatal experimentally infected Holstein calves. Absorption tests with d-xylose and retinyl-palmitate, and the lactulose/mannitol test of intestinal permeability were simultaneously performed in 1-week intervals from challenge to full recovery. In infected animals, reduced intestinal absorptive capacity for both D-xylose and retinyl-palmitate was observed on day 7 post-infection (p.i.). At the same time, a more than 100% elevation of intestinal permeability was observed in the infected calves. All intestinal functions, except absorption of retinyl-palmitate, were significantly affected and changes were detected up to day 14 p.i. In contrast, results of all tests obtained on day 21 p.i. suggest full recovery of the infected intestine. Significantly, growth of the calves which had recovered from cryptosporidiosis was still affected between days 14 and 21 p.i.