Black Rabbits Research Articles

Comparative analysis of meat quality of Laiwu black, Minxinan black and Hyla rabbits

Abstract. The meat rabbit industry in China relies on foreign breeds and synthetic lines; the development of superior domestic breeds has not yet been fully realised. We compared the meat quality of two Chinese local breeds of black rabbits (Laiwu black and Minxinan black) and Hyla commercial rabbits, to provide a reference for the utilisation of meat rabbit breeds. In the present study, 35 d old Laiwu black rabbits, Minxinan black rabbits, and Hyla rabbits (20 rabbits each) were selected and reared under identical feeding and management conditions for 7 weeks, after which 10 randomly selected rabbits from each group were slaughtered for the analysis of meat quality. The a∗ (redness) value of the two local breeds was significantly higher than that of Hyla rabbits (p<0.01). The shearing force and drip loss of Laiwu black rabbits were significantly lower than those of the other groups (p<0.05). The two local breeds exhibited significantly higher myoglobin levels than Hyla rabbits (p<0.01), while melanin was highest in the meat of Minxinan black rabbits. The essential amino acids (valine, isoleucine, leucine and lysine) were significantly lower in Minxinan black rabbits than in the other groups (p<0.05). Aldehyde (heptanal, octanal) contents in Minxinan black meat were significantly higher than those of the other groups (p<0.01); however, nucleotide (guanine, adenine) contents were significantly lower (p<0.01). Unsaturated fatty acids (oleic, linoleic, α-linolenic) were significantly higher in the meat of Laiwu black rabbits than in those of the other groups (p<0.05). Both Laiwu black and Minxinan black rabbits have certain advantages in terms of nutritional indicators while also having good meat colour and flavour. The results of this study provide a theoretical reference for the research and development of meat rabbit breeds.

Dual effects of gonadotropin-inhibitory hormone on testicular development in prepubertal Minxinan Black rabbits (Oryctolagus cuniculus).

Gonadotropin-inhibitory hormone (GnIH) is a neurohormone that not only suppresses reproduction at the brain level but also regulates steroidogenesis and gametogenesis at the gonad level. However, its function in gonadal physiology has received little attention in rabbits. The main objective of this study was to evaluate the effects of GnIH on testicular development and function in prepubertal Minxinan Black rabbits (Oryctolagus cuniculus). In the present study, we investigated the serum reproductive hormone concentration, testicular parameters, morphology of seminiferous tubules, apoptosis of testicular cells, and expression of reproductive-related genes in male prepubertal Minxinan Black rabbits intraperitoneally administered with 0, 0.5, 5, or 50 μg quail GnIH-related peptides (qGnIH) for 10 days. Compared with the vehicle, administration with 5 μg of qGnIH downregulated the serum testosterone concentration and mRNA levels of spermatogenic genes (PCNA, FSHR, INHβA, HSF1, and AR) and upregulated the apoptosis rate of testicular cells; administration with 50 μg of qGnIH decreased the serum testosterone concentration and hypothalamic GnIH gene mRNA level and increased the serum LH concentration, pituitary LHβ gene mRNA level, testicular weight, gonadosomatic index (GSI), and spermatogenic cell layer thickness. It is concluded that GnIH could exert dual actions on testicular development depending on the male prepubertal rabbits receiving different intraperitoneal doses.

Improving indigenous Vietnamese Black Rabbit frozen sperm quality: the role of glycine and sperm selection methods

Rabbit sperm are known to undergo damage during both cryopreservation and thawing, leading to decreased viability, motility and membrane integrity. Glycine can protect sperm and reduce damage during freezing. Swim-up is a simple semen processing method for selecting good motile sperm. The study evaluated the effect of the swim-up method and glycine with different concentrations supplemented to the frozen medium. Three indigenous black rabbits were selected for semen collection by artificial vagina. Next, semen was selected by swim-up method and diluted with glycine-added frozen medium. The samples were then transferred to 0.5 mL straws, cooled to 15°C and 5°C, placed in liquid nitrogen vapour, and finally placed directly into liquid nitrogen (-196°C). The samples were thawed and evaluated for sperm quality. The results showed that the medium supplemented with 10mM glycine in combination with swim-up method for 30 min gave the best results and was significantly different from the remaining concentrations (P<0.01), with viability rate, overall mobility and membrane integrity of 68.0%, 58.7% and 49.7%, respectively. In conclusion, 10 mM glycine concentration combined with swim-up for 30 min is the optimal choice for freezing local black rabbit semen. The study highlights the importance of optimising freezing protocols to improve the quality of frozen rabbit sperm, which can have important implications for animal breeding and conservation efforts.

Effects of JUNCAO Ganoderma lucidum polysaccharide peptide on slaughter performance and intestinal health of Minxinan black rabbits

This experiment was conducted to investigate the effects of JUNCAO Ganoderma lucidum polysaccharide peptide (JCGLPP) on slaughter performance and intestinal health of Minxinan black rabbits, which aimed to provide the basis for the application of JCGLPP in meat rabbits. One hundred male weaned Minxinan black rabbits of (33 ± 2) d [(initial body mass (655.65 ± 25.90) g] were randomly divided into four groups with five replicates per group and five rabbits per replicate. The diets were supplemented with 0 (control group), 50 (group I), 100 (group II) and 150 mg·kg−1 (group III) of JCGLPP, respectively. This experiment lasted for 56 days. The results are shown below: (1) The live weight before slaughter of groups I and III was significantly higher than that of control group (p < 0.05); The full net bore weight of group III was significantly higher than that of control group (p < 0.05). (2) pH value of group I was significantly higher than that of control group (p < 0.05); NH3–N content in experimental groups were significantly higher than that in control group(p < 0.05) while NH3-N content in group I was significantly higher than that in groups III and II (p < 0.05); The content of butyric acid in group II was significantly lower than that in control group (p < 0.05); There were no significant differences in acetic acid, isovaleric acid, isobutyric acid and propionic acid in experimental groups compared with control group (p > 0.05). (3) The Occludin content in duodenum, jejunum and ileum of groups I and II was significantly higher than that of control group (p < 0.05). (4) At the phylum level, Firmicutes and Bacteroidetes were the dominant phylum in each group. At the genus level, norank_f__norank_o__Clostridia_UCG-014 in group II were significantly higher than those in control group (p < 0.05). In conclusion, although dietary JCGLPP supplementation could not improve slaughter performance of Minxinan black rabbits, it could improve cecal fermentation parameters and intestinal flora structure and composition of Minxinan black rabbits to a certain extent. Our results revealed that 100 mg·kg−1 might be the optimal concentration obtained in dietary JCGLPP supplementation, which provided ideas and feasibility for drug combination.

Effect of guanidinoacetic acid on the growth performance, myofiber, and adenine nucleotide of meat-type rabbits.

This study aimed to investigate the effect of dietary guanidinoacetic acid (GAA) on the growth performance, slaughter traits, myofiber, and adenine nucleotide of meat-type rabbits. Experimental treatments consisted of control (CON) and GAA addition at 0.04% (T1), 0.08% (T2), and 0.12% (T3) of diet. A total of 240 weaned rabbits (meat-type male Chinese black rabbits) were randomly distributed into four groups with six replicates of ten rabbits each. Results showed that the three doses of GAA increased (p<0.05) final body weight, carcass weight, the density and area of quadriceps femoris fiber; and T3 showed significant effects (p<0.05) on weight gain, feed/gain, and dressing percentage, and the traits of longissimus fiber, compared to CON. Dietary GAA increased (p<0.05) the meat color a* and b* in longissimus and quadriceps; and T3 showed the lowest (p<0.05) shear force of longissimus. Furthermore, GAA increased (p<0.05) the contents of adenosine triphosphate and total adenine nucleotide in longissimus and quadriceps. In longissimus adenosine triphosphate, total adenine nucleotide, and adenylate energy charges, T3 treatment was most effective (p<0.05); while T2 and T3 treatment was more effective (p<0.05) than T1 in quadriceps. Additionally, linear or quadratic responses (p<0.05) to the increased doses of GAA were found on body weight gain, meat color, total adenine nucleotide, and adenylate energy charges. It is concluded that GAA can be used in the rabbit diet to improve growth and carcass traits, and these are related to the high levels of muscle adenine nucleotide.

Cryopreservation of local black rabbit spermatozoa in the Mekong delta region of Vietnam: Evaluating cryoprotectant effectiveness.

Rabbit production is well developed in the Mekong Delta and Vietnam, with increased consumption of rabbit meat in both urban and rural areas. Consequently, meat rabbit breeds have become popular in almost all provinces in Vietnam, resulting in a decline in the population of Local Black rabbits over the years. To support breeding programs, there is a crucial need to develop a cryopreservation method. The objective of this study was to develop sperm cryopreservation protocols and determine the optimal cryoprotectant for Local Black rabbit spermatozoa. Rabbit spermatozoa were obtained and diluted with TCG-EggYolk freezing medium containing 5%, 8%, and 10% glycerol or DMSO in a 1:1 ratio. Glycerol and DMSO-free mediums served as the controls. Samples were put into 0.5-mL straws, cooled to 15°C and 5°C, then placed on nitrogen vapour for 15 min and directly immersed in liquid nitrogen at -196°C. Samples were thawed at 37°C for 60 s after being frozen for 72 h Sperm quality measures, such as viability, motility, and membrane integrity, were assessed both before and after freezing. The results showed that the average viability, average motility, and average membrane integrity were 61.9%, 53.9%, and 42.9%, respectively, after thawing with 5% glycerol, which was higher than the two higher concentrations of glycerol (8% and 10%) (p < .05). Similarly, with 8% DMSO, the average viability, average motility, and membrane integrity were 59.2%, 51.0%, and 41.8%, respectively, which were higher than the two concentrations of DMSO (5% and 10%) (p < 0.05). Therefore, the cryopreservation of local black rabbit sperm with 5% glycerol or DMSO 8% resulted in high sperm quality, but considering the practical aspect of minimizing the volume of the preservative, a concentration of 5% glycerol may be the best option.

Impact of different dietary fibre sources on production performance, bacterial composition and metabolites in the caecal contents of rabbits.

This study was conducted to investigate the effects of different dietary fibre sources on growth performance, gastrointestinal tract development, caecal fermentation and bacterial composition in the caecal contents of rabbits. A total of 120 35-day-old weaned Minxinan black rabbits were divided into three groups and fed a diet composed of peanut straw powder (Group A), alfalfa powder (Group B) and soybean straw powder (Group C) as the main fibre source. The final body weight and average daily gainin Group B were higher than those in Group C, and the average daily feed intakeand feed conversion ratio in Group A were lower than those in Group C (p < 0.05). The relative weights of the stomach, small intestine and caecum of rabbits in Group C were higher than those in Groups of B and A, and the relative weights of the caecal contents in Group C were lower than those in Groups A or B (p < 0.05). The pH value and propionic acid, butyric acid and valeric acid concentrations in the caecum of Group C were lower than those in the caecum of Groups A orB, and the concentration of acetic acid in the caecum was lower (p < 0.05). The dominant microbes in the caecal contents of Minxinan black rabbits were Firmicutes, Bacteroidetes and Proteobacteria at the phylum level, and the number of species, Chao1 index and ACE index measured was different between the B-C and A-C groups (p < 0.05). Different dietary fibre sources could affect the growth performance, gastrointestinal tract development and intestinal microbiota of rabbits, and the nutritional value of alfalfa powder was better than that of peanut straw and soybean straw.

Effects of feeding methods on growth and slaughter performance, blood biochemical indices, and intestinal morphology in Minxinan black rabbits (Oryctolagus cuniculus)

Feed restriction after weaning is a common strategy used in commercial rabbit farms to improve feed efficiency, promote health, and reduce mortality. However, few studies have investigated the feed restrictions of Minxinan black rabbits (Oryctolagus cuniculus). Thus, the effects of feed restriction on growth and slaughter performance, intestinal morphology, and blood biochemical indices of Minxinan black rabbits were evaluated in this study. Rabbits in group A (control group) had ad libitum intake, while those in feed restriction groups (groups B, C, and D) were restricted to 80% of the average daily feed intake (ADFI) of group A the day before. The rabbits in group B were fed once per day at 8:00 am. Rabbits in groups C and D were fed twice per day at 8:00 am (50%) and 4:00 pm (50%) and 8:00 am (30%) and 4:00 pm (70%), respectively. The experimental period lasted for 8 weeks. Compared to that in group A, the diarrhea rate of group C was significantly decreased (P < 0.05), and the ADFI, feed conversion ratio, abdominal fat weight, abdominal fat rate, total protein, albumin, globulin, alanine aminotransferase (ALT), low-density lipoprotein, and intestinal crypt depth of all feed restriction groups were significantly reduced (P < 0.01). Feed conversion ratio in group D was significantly better than that in groups B and C (P < 0.05). The efficiency index (EI) of groups C and D was higher than that of groups A and B (P < 0.01). Triglyceride levels in groups C and D were significantly lower than those in group A. The villus length to crypt depth of the duodenum and jejunum in group D was significantly higher than that in group A (P < 0.01). In conclusion, the following parameters can be improved by feed restriction: feed conversion ratio, diarrhea rate, abdominal fat rate, serum ALT, lipid indices and intestinal health of Minxinan black rabbits, and the EI of the farm. Feeding twice per day, 30% at 8:00 am and 70% at 4:00 pm, had the best comprehensive effects.

Dietary addition of Humulus scandens improved the intestinal barrier in rabbits

ABSTRACT This study was conducted to investigate the effect of Humulus scandens (HS) in diet on the production performance and intestinal barrier of rabbits. One hundred and sixty Laiwu black rabbits at 35 days of age with body weight of 692.5 ± 48.3 g were divided into four groups (five replicates per group and eight rabbits per replicate): fed on a basal diet free of HS (control), 4%, 8% or 12% HS powder supplement. The results showed that the dietary addition of HS decreased the ADFI, F/G, diarrhoea ratio and mortality ratio. Besides, the final body weight and ADG (P < .05) increased with the level of HS. Rabbits in 12% HS group had a higher sIgA and IgG concentration in serum and ileum than control, while lower TNFα, IFN-γ and IL-6 concentration (P < .05). Compared with the control, the HS supplementation groups for 12% level could decrease the mRNA expression of ZO-1, JAM3 and mucin1 (P < .05). In conclusion, dietary supplement of HS modulates immune responses and enhances intestinal barrier, meanwhile inhibits the synthesis of cytokine. Besides, our experiment offers positive evidence in improving rabbit health of HS as rabbit feed resource.

Efficiency of leptin gene polymorphisms in the evaluation of the growth performance and carcass measurements of v-line and Baladi black rabbits

This study investigated the association between both polymorphisms and metabolic marker changes of the leptin gene, and body weight, weight gain, carcass traits, feed intake, and feed conversion ratio. Blood samples were collected from 60 V-line and 60 Baladi Black rabbits for DNA extraction and biochemical analysis. DNA sequencing of leptin (202-bp) revealed four non-synonymous single nucleotide polymorphism (SNPs) that characterized a number of V-line rabbits. Statistical analysis revealed that the identified SNPs were associated with rabbit growth and carcass measurements (p &lt; 0.05). A discriminant analysis model showed a high classification percentage for the identified SNPs within and between breeds using body weight at 5-14 weeks of age (91.7%), slaughter traits (91.6%), feed intake, daily feed intake, and feed conversion ratio (76.7%). This study reveals that leptin gene could be a candidate for growth traits in rabbits enabling the development of marker-assisted selection (MAS) in different rabbit breeds.

Dietary inclusion of fermented ginger straw effect on the growth performance, gastrointestinal tract development and caecal fermentation of fattening rabbits

This experiment was conducted to evaluate the effects of dietary inclusion of fermented ginger straw on the growth performance, gastrointestinal tract development and caecal fermentation of fattening rabbits. A total of 160 45-d-old Laiwu black rabbits were randomly divided into 4 groups and fed 0% (Control), 5, 10 or 15% fermented ginger straw in their diet as a replacement for peanut straw powder. The trial lasted for 7 d of adaptation and 43 d for testing. Growth performance was recorded from 52 to 95 d of age (n=5 per treatment with 30 rabbits, 3 males and 3 females per replicate), TTAD of nutrients from 91 to 95 d of age, and gastrointestinal tract development, caecum fermentation and carcass traits were determined at 95 d of age (n=5 per treatment with 10 rabbits, 1 males and 1 females in per replicate).The results showed that the average daily gain and final body weight in the experimental groups (5, 10 and 15% fermented ginger straw) were higher than in the control group (P&lt;0.05). However, the average daily feed intake in the 15% group was higher than in the other groups, while the total tract apparent digestibility of crude protein, ether extract, neutral detergent fibre and acid detergent fibre were lower than in the control group (P&lt;0.05), and the relative weights of the stomach, small intestine and caecum content in the 15% substitution group were higher than those in the control group (P&lt;0.05). In addition, the thickness of the muscle layer in the 15% substitution group was higher than that in the other groups (P&lt;0.05). Moreover, pH and total volatile fatty acids concentration in the caecal content were similar among the 4 groups (P&gt;0.05). The current work shows that fermented ginger straw could be used as roughage material in fattening rabbit production up to a dietary dose of 10%.

Antioxidants status and physiological responses to early and late heat stress in two rabbit breeds.

Early life heat stress negatively affects rabbit production and well-being. However, the physiological response to acute heat stress in later life is not clearly defined. The present study aims to investigate the effects of early and late heat stress at 36°C on some blood constituents, antioxidant enzymes activity in the blood, and muscle in New Zealand white and Baladi Black rabbits. A total of sixty post-weaning rabbits of each breed were randomly divided into two groups; control groups (NZWC and BBC) and early heat-stressed groups for six hours at 36 ± 1°C and 62% relative humidity (RH) (NZWT and BBT groups). After heat stress, six rabbits from each group were slaughtered for blood and muscle tissue collection. The surviving rabbits were kept at 28 ± 1°C and 40% RH till 13 weeks of age. At the end of 13 weeks, all rabbits were exposed to late heat stress as precious described to perform four groups: single late stressed groups; NZWC2, BBC2, and double stressed groups; NZWT2 and BBT2. After late heat stress, six rabbits from each group were slaughtered for blood and muscle tissue collection. The early and late heat stress caused a significant reduction in the blood creatine kinase, lactate dehydrogenase, and high-density lipoprotein and antioxidant enzymes' activity in blood and muscle of both NZW and BB rabbits compared with the control groups. While, the blood total cholesterol, triglycerides, total lipids levels, and lipid peroxidation activity in blood and muscle were significantly increased due to the early and late heat-stressed both breeds compared with the control groups. It could be concluded that the early heat stress at 36°C has negative effects on several physiological indicators and antioxidant activities in the blood and muscle of NZW and BB rabbits.

The effect of conjugated linoleic acids on the growth performance, carcase composition and meat quality of fattening rabbits

This experiment was conducted to study the effects of dietary conjugated linoleic acids (CLAs) on the growth performance, fat metabolism, carcase composition and muscle quality of fattening rabbits. A total of 160 Minxinan black rabbits aged 75 days with body weights of 1658.9 ± 188.8 g were randomly divided into 4 groups. They were fed a basic diet supplemented with 0 (control), 0.5%, 1.0%, or 1.5% CLA for 50 days. Dietary CLA reduced the feed intake and serum triglyceride and cholesterol levels. In addition, the crude protein content in rabbit meat was increased, along with the cholesterol and the ether extract levels in the 1.5% depression group. Moreover, the fatty acid composition in rabbit meat was changed, and the content of polyunsaturated fatty acids/monounsaturated fatty acids (PUFAs/MUFAs) increased with the increasing levels of CLA addition. These findings indicate that CLA greatly improved the nutritional value of rabbit meat. From an economic point of view, CLA would normally be included at a concentration of 0.5% in the formulation of feeds for fattening rabbits. HIGHLIGHTS Minxinan black rabbits were fed conjugated linoleic acid (CLA)- supplemented diets for 50 d. CLA decreased the feed intake of experimental rabbits. CLA has significant effects on fat deposition and serum triglyceride and cholesterol levels. CLA greatly improved the nutritional value of rabbit meat. The recommended CLA level is 0.5% for meat rabbits．

Exploring the genomic resources and analysing the genetic diversity and population structure of Chinese indigenous rabbit breeds by RAD-seq

BackgroundChinese indigenous rabbits have distinct characteristics, such as roughage resistance, stress resistance and environmental adaptability, which are of great significance to the sustainable development of the rabbit industry in China. Therefore, it is necessary to study the genetic diversity and population structure of this species and develop genomic resources.ResultsIn this study, we used restriction site-associated DNA sequencing (RAD-seq) to obtain 1,006,496 SNP markers from six Chinese indigenous rabbit breeds and two imported rabbit breeds. Jiuyishan and Fujian Yellow rabbits showed the highest nucleotide diversity (π) and decay of linkage disequilibrium (LD), as well as higher observed heterozygosity (Ho) and expected heterozygosity (He), indicating higher genetic diversity than other rabbits. The inbreeding coefficient (FIS) of New Zealand rabbits and Belgian rabbits was higher than that of other rabbits. The neighbour-joining (NJ) tree, principal component analysis (PCA), and population structure analysis of autosomes and Y chromosomes showed that Belgian, New Zealand, Wanzai, Sichuan White, and Minxinan Black rabbits clustered separately, and Fujian Yellow, Yunnan Colourful, and Jiuyishan rabbits clustered together. Wanzai rabbits were clearly separated from other populations (K = 3), which was consistent with the population differentiation index (FST) analysis. The selection signature analysis was performed in two populations with contrasting coat colours. With Sichuan White and New Zealand rabbits as the reference populations and Minxinan Black and Wanzai rabbits as the target populations, 408, 454, 418, and 518 genes with a selection signature, respectively, were obtained. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed on the genes with a selection signature. The results showed that the genes with a selection signature were enriched in the melanogenesis pathway in all four sets of selection signature analyses.ConclusionsOur study provides the first insights into the genetics and genomics of Chinese indigenous rabbit breeds and serves as a valuable resource for the further effective utilization of the species.

CHARACTERIZATION, GENETIC EVALUATION, AND GENETIC TRENDS FOR SOME REPRODUCTIVE TRAITS OF BALADI BLACK RABBITS DOES

A total of 792 litters from 210 does of Baladi Black (BB) rabbits were considered to make characterization, and genetic evaluation for some doe traits, including litter traits (litter size at birth; LSB, litter size born alive; LSA, litter size at 21 days; LS21, litter size at weaning; LSW, Litter weight at birth; LWB, Litter weight at weaning; LWW, and the pre-weaning mortality rate; PWM), conception traits (number of services per conception; NSC, and gestation length; GL), and interval traits (kindling interval; KI and days open; DO). Heritability for litter traits was relatively low ranged from 0.08 to 0.14 except this for PWM it was moderate (0.15); h2 for conception and interval traits were low ranged from 0.00 to 0.06. Repeatability (R) for litter traits were low to moderate ranged from 0.11 to 0.34; R estimates for PWM and LWB were higher than other traits (0.16 and 0.34) respectively; and R for conception and interval traits was low ranged from 0.01 to 0.11. Genetic correlations among litter traits were positive, and moderate to strong ranged from 0.23 to 0.92 except for this between LSB and LWW and this between LWB and PWM, it was negative -0.16 and -0.08 respectively. Genetic correlations among conception and interval traits were positive and very strong ranged from 0.68 to 1.00 except this between GL and NSC it was negative and strong (-0.77). The ranges of transmitting abilities (TA) for litter size traits ranged from 1.92 to 2.10 kits. Ranges of TA for litter weight traits ranged from 0.01 to 0.70 grams. The range of TA for PWM was 33.90%. Ranges of TA for conception traits were low, 0.08 days for GL and 0.11 (numbers) for NSC. The ranges of TA were 4.93 and 10.72 days for KI and DO respectively. The percentage of positive transmitting ability ranged from 30.95 to 53.81 for litter traits and from 50.00 to 51.90 for conception, and interval traits. The genetic trends for litter traits at different ages, conception and interval traits were low and had fluctuations by year-season which could be due to variation in climatic conditions. Conclusively, Baladi Black rabbits' does have good potential reproduction. Most of doe reproductive traits of these rabbits were largely affected by environmental conditions which would be improved by improving environmental and management conditions. The moderate estimate of h2 for PWM (0.15) and its range of transmitting ability (33.90%) suggest decreasing pre-weaning mortality by selection. Moderate estimates for PWM and LWB comparing with other traits (0.16 and 0.34) respectively suggests using culling and selection strategies. The negative genetic correlation between LSB and LWW (-0.16) should be taken into consideration when designing a breeding program for these rabbits. The perfect genetic correlation between KI and DO (1.00) reflected that these two traits could be indicators of each other when designing breeding programs.

Genetic adaptive potentials of four breeds of rabbit to heat stress in the humid tropics

Rabbit production under tropical conditions is affected by environmental stress mainly from the effect of high ambient temperatures and high humidity, low wind speed and indirect solar radiation. This experiment was conducted to investigate the adaptive potentials of Californian, New Zealand white, Havana black and Palomino brown rabbits to heat stress when raised in humid tropics. A total number of ninety-six rabbits were used. Rectal temperature, respiratory rate, pulse rate and heat stress index were measured in these temperate breeds during rainy and dry season. The results showed that the breed of rabbit had a significant effect (P&lt;0.05) on rectal temperature, respiratory rate, pulse rate and heat stress index. Havana black rabbit had the highest mean rectal temperature value (39.32 ± 0.03°C) followed by Palomino brown (38.97 ± 0.03°C), while the least value was recorded for New Zealand white (38.68 ± 0.02). Respiratory rate values followed the same pattern with that of rectal temperature with higher respiratory rate 69.09 ± 1.05 breaths/min recorded for Havana rabbits. The pulse rate values ranged from 163.23 ± 0.47 - 184.35 ± 0.78 beats/minutes. The highest pulse rate of 184.35 ± 3.78beats/minute was recorded for Havana black. The lowest heat stress index was obtained for New Zealand white followed by California and Palomino Brown while Havana black rabbit had the highest value (1.95± 0.01). The respiratory rate was significantly lower among males as compared to their female counterparts (63.09±0.58 versus 69.54 ± 1.65breaths per minute). The age of the rabbit also significantly affected (P&lt;0.05) the rectal temperature, respiratory rate, pulse rate and heat stress index. 12 weeks old rabbit had the highest mean values while 4 weeks old rabbit had the least values. The heat stress index value obtained during dry season was higher (P&lt; 0.05) than that obtained for rainy season (1.93± 0.02 versus 1.80 ± 0.01). Havana black rabbits and Palomino brown were more prone to heat stress than California and New Zealand white rabbits in tropical environment.

Analysis of MC1R, MITF, TYR, TYRP1, and MLPH Genes Polymorphism in Four Rabbit Breeds with Different Coat Colors.

Simple SummaryCoat color is an important breed characteristic and economic trait for rabbits, and it is regulated by a few genes. In this study, the gene frequencies of some pigmentation genes were investigated in four Chinese native rabbit breeds with different coat colors. A total of 14 genetic variants were detected in the gene fragments of MC1R, MITF, TYR, TYRP1, and MLPH genes, and there was low-to-moderate polymorphism in the populations. The gene frequency showed significant differences among the four rabbit populations. The above results suggest that these genetic variations play an important role in regulating the coat color of rabbits. This study will provide potential molecular markers for the breeding of coat color traits in rabbits.Pigmentation genes such as MC1R, MITF, TYR, TYRP1, and MLPH play a major role in rabbit coat color. To understand the genotypic profile underlying coat color in indigenous Chinese rabbit breeds, portions of the above-mentioned genes were amplified and variations in them were analyzed by DNA sequencing. Based on the analysis of 24 Tianfu black rabbits, 24 Sichuan white rabbits, 24 Sichuan gray rabbits, and 24 Fujian yellow rabbits, two indels in MC1R, three SNPs in MITF, five SNPs (single nucleotide polymorphisms) in TYR, one SNP in TYRP1, and three SNPs in MLPH were discovered. These variations have low-to-moderate polymorphism, and there are significant differences in their distribution among the different breeds (p < 0.05). These results provide more information regarding the genetic background of these native rabbit breeds and reveal their high-quality genetic resources.

Hepatic acute-phase response, antioxidant biomarkers and DNA fragmentation of two rabbit breeds subjected to acute heat stress

Acute heat stress (AHS) is known to affect rabbit production and well-being negatively. Yet, early acute heat stress effect on later physiological response is poorly studied. Our study aimed to provide more knowledge of rabbit physiological response to early acute heat stress in two distinguished rabbit breeds. A total of 120 males of New Zealand White (NZW) and Baladi Black (BB) rabbits five weeks old were recruited and randomly divided into two sub-groups, control groups (Control) reared in a controlled environmental chamber 28 °C, and 40% RH and early acute heat stress groups (HS) exposed to 36 °C and 62% RH for 6 hours. At 13 weeks, rabbits of all groups were subjected to the same AHS conditions. Our results, irrespective of breeding differences, demonstrate a significant (p < .05) increase in inflammation markers (TNFα, IL-6 and lipid peroxidation), acute-phase proteins (ceruloplasmin, α-1-acid glycoprotein), and DNA fragmentation with a significant reduction in liver antioxidant enzymes concentrations (glutathione reduced, superoxide dismutase, and catalase) in HS groups compared to breed relative control groups. Furthermore, when all experimental groups at 13 weeks of age were subjected to the same stress conditions, the early HS group showed the same significant adverse physiological effects. It can be suggested that rabbits from different genetic groups are vulnerable to acute heat stress exposure at the early stage of life compared to later stages. Highlights Heat stress is one of the most critical issues facing rabbit production. Exposure young rabbits to acute heat stress had adverse effects on physiological parameters in later life. Rabbits exposed to acute heat stress at an early age did not produce thermo-tolerance ability to later time heat exposure.

Association of leptin mRNA expression with meat quality trait in Tianfu black rabbits

Leptin is a hormone synthesized and secreted primarily in adipocyte which can help to regulate energy balance. In this experiment, three tissue samples of Tianfu black rabbits at four growing periods were selected. The expression levels of leptin gene in different tissues were detected by real-time fluorescence quantitative PCR. The correlation analysis showed that the correlation coefficient between the expression levels of leptin gene in perirenal fat and intramuscular fat content in 84-day-old male rabbits was 0.73 (p < 0.05); the correlation coefficients between the expression levels of leptin gene in left biceps femoris and intramuscular fat and 24-hour pH in 84-day-old male rabbits were 0.95 (p < 0.01) and 0.85 (p < 0.05), respectively. Besides, the correlation coefficient between the expression levels of leptin gene in male left biceps femoris and cooked meat rate was 0.83 (p < 0.05). According to the analysis results, we inferred the expression levels of leptin gene in Tianfu black rabbits can influence meat quality and the meat quality of high expression levels of leptin gene in Tianfu black rabbits is better. These results revealed the leptin gene may be one of the important candidate genes for meat quality traits of molecular markers.

Effect of early age heat stress on growth performance and some blood parameters of two strains of rabbits

The main objective of the present study was to evaluate the effect of short term Heat Stress on productive performance and some blood parameters in two strains of growing rabbits. A total number of 60 weaned unsexed rabbits (6 weeks of age) were used in this study (30 from each of New Zealand White, NZW, and Local Baladi Black, BB rabbits). They were randomly divided into two experimental groups: a control group and heat stressed one. The latter group was exposed to four hours of heat stress at 36 ± 1 ⁰C and 55 – 60% RH for three consecutive days at 42 days of age. The same manner was applied after six weeks of age (at marketing). After HS exposure, three rabbits from each treatment were used to determine some blood parameters, heat shock protein (HSP 70, 90); Growth performance data were also recorded. Results showed that daily weight gain was significantly increased in heat stressed rabbits than control, while feed consumption was significantly reduced in NZW rabbits, resulting in an improvement in FCR of NZW rabbits than BB. Heat stress (p≤0.05) increased plasma total protein, albumin and Globulin than control group, while A/G ratio was not influenced. Baladi Black rabbits had significantly lower IGF and Corticosterone level compared by NZW rabbits, while T3 hormone level was not significantly affected. HS increased (p ≤ 0.05) IGF and Corticosterone levels. A significant interaction effect between HS and breed was recorded for all studied hormones. Heat shock protein were significantly increased in local BB rabbits compared to NZW ones. It is concluded that it is concluded that early age heat exposure of weaning rabbits could be used as an alternative tool to alleviate the negative impact of heat stress at older age. We chose two strains of rabbits (BB NZW) because they the most common types in our country.