Differences in productive robustness in rabbits selected for reproductive longevity or litter size

Changes in Body Reserves, Non-Esterified Fatty Acids, and Leptin during the Reproductive Lifespan of the Rabbit Female

The aim of this work is to study changes in body weight, perirenal fat thickness (PFT), and non-esterified fatty acid (NEFA) and leptin concentrations throughout the reproductive life of the rabbit female and their correlations when a semi-intensive reproductive rhythm is applied. A total of 46 lactating females were used. Body weight, PFT, and NEFA and leptin concentration were recorded at 12 weeks of age, at first mating and delivery, and at second, third, and fourth mating, 12th d of gestation, and delivery. The highest body weight was detected on the 12th d of any gestation, around 4280 g, and the lowest weight was at delivery, around 4030 g. PFT increased until third mating. NEFA and leptin concentration showed a cyclical pattern throughout the reproductive lifespan of the females. NEFAs presented the highest concentration at delivery within each reproductive cycle and levels decreased over the course of the deliveries (0.423 mmol/L at first delivery, 0.406 mmol/L at second delivery, 0.371 mmol/L at third delivery, and 0.309 mmol/L at fourth delivery). Similar NEFA concentrations at mating and on the 12th d of gestation were obtained. Leptin showed the highest concentrations at mating within each reproductive cycle. Leptin decreased between mating and delivery in all reproductive cycles and it was close to 1 ng/mL HE. Low or null correlations were shown between body weight, PFT, and NEFA and leptin concentration at mating, 12th d of gestation, and delivery. In conclusion, females are able to maintain a semi-intensive reproductive rhythm across four parities weighing around 4 kg from first mating. Females had an increased perirenal fat thickness until third delivery, and their NEFA concentration was maximum at delivery and leptin concentration was maximum at mating. Body weight, PFT, and NEFA and leptin concentration should be measured during critical moments of reproductive life in order to determine body condition and energy mobilization, due to their low or null correlations.

Reproductive performance of rabbit females from three paternal lines with a different potential for growth rate and resilience

A total of 197 nulliparous rabbits (from three paternal lines) were used to test potential strategies to overcome the consequences on reproduction associated with the selection for high growth rate. The R line was selected for growth rate during the growing period for 37 generations, the RF line was founded through a high selection intensity of elite animals of the R line, and the RFLP line, which was obtained by backcrossing RF animals with the LP line (a long-lived productive maternal line, characterised by high resilience). BW, perirenal fat thickness, fertility, daily feed intake, milk yield and blood metabolites of females were controlled from 1st artificial insemination to 3rd parturition. Litter size, litter weight, individual weight and feed ingestion of kits were controlled from birth to weaning. Our results show that RF females were significantly lighter than R and RFLP females throughout the trial (-5.0%; P < 0.05). Furthermore, RF animals had a higher fertility rate than RFLP females, at first cycle (+10.5 percentage points; P < 0.05). However, RFLP had a higher fertility rate than RF females at second cycle (+21.5 percentage points; P < 0.01). On average, RFLP females had higher perirenal fat thickness than R females at parturition (+3.0%; P < 0.05) and higher daily feed intake than of R and RF females during gestation and late lactation (+9.7 and +8.7%, respectively; P < 0.05). RFLP females produced more milk than R and RF females in the two first lactations (+18.5%; P < 0.001). In the first three parturitions, R females delivered fewer kits born alive (-1.7 kits than RF and RFLP; P < 0.05). In addition, R females' blood had a higher concentration of glutamine and glutamate than RFLP (+24 and +22.7%, respectively; P < 0.05). RFLP litters were heavier than both R and RF litters throughout lactation. However, R kits were heavier at birth than RF and RFLP (+7.9%). Results suggest that the foundation of a paternal line using elite animals could generate females with better early reproductive performance. In addition, backcrossing the RF line with a maternal LP line resulted in a genetic line whose females had a different resource allocation strategy to foster reproduction during the studied period.

Genotype by heat conditions interaction effects on growth and litter traits in rabbits

Heat stress has severe impacts on rabbit performance because they have difficulty getting rid of excess heat. The interaction between genetic and environmental factors plays a vital role in the adaptation process. The current study aimed to evaluate the effects of interaction between the genotype and heat conditions (G×H) on litter size and growth traits. Two rabbit lines were used in the current study, Egyptian maternal line (APRI) and New Zealand White (NZW). The rabbits were raised under normal (22°C) or heat stress (35°C) conditions. The does were raised in individual cages, and their kits were reared under the same conditions. Negative effects of heat conditions were noted for litter traits, as heat stress had significantly reduced the number of born alive, total born, and marketed number rabbits by about 16, 11, and 25%, respectively. Moreover, growth traits were reduced under heat stress conditions compared to normal temperature conditions. Significant differences between genotypes were observed, APRI rabbits were higher than NWZ rabbits in the total born, number of born alive, number weaned, and the number of marketed rabbits by 10, 8, 11, and 10%, respectively. Genotype by heat conditions interaction effects were observed, APRI litters under normal conditions showed significantly higher litter traits than NWZ litters, whereas relevant reductions in litter traits of APRI line than NZW litters when reared in heat conditions. For growth traits, the differences between the two lines under normal conditions were reduced when animals of the two lines were raised under heat stress, for BW28, BW42, BW63, ADG28-42, and DF28-42 while these differences were increased for ADG42-63, DF28-42 and feed conversion during the whole fattening period. Based on the observed G × H interactions, it is important to select the animals under the same production conditions to raise rabbits that can cope with the expected global warming conditions.

Genetic factors of functional traits

Selection of functional traits is a challenge for researchers, but an increasingly necessary objective due to the growing concern regarding animal welfare and overcoming the problems of reducing antibiotic use in rabbit production without undermining the animals’ productivity. The aim of this review is to discuss the genetic control of resistance to diseases, longevity and variability of birth weight within a litter, or litter size variability at birth within doe, describing the selection programmes and the first results from a multi-omics analysis of resistance/susceptibility to diseases. The heritability is around 0.13 for longevity, 0.01 for uniformity in birth weight, 0.09 for litter size variability and around 0.11 for disease resistance. Genetic correlations between functional traits and production traits are mostly no different from zero, or are moderately favourable in some cases. Six selection programmes developed in three countries are reviewed. Line foundation with high pressure for selection or divergent selection experiments are different methodologies used, and favourable responses to selection have been achieved. Genomics studies have revealed associations in regions related to immune system functionality and stress in lines selected for litter size variability. Knowledge of the role of gut microbiota in the rabbit’s immune response is very limited. A multi-omics approach can help determine the microbial mechanisms in regulation immunity genes of the host.

Correlated Response to Selection for Litter Size Residual Variability in Rabbits’ Body Condition

A divergent selection experiment for residual variance of litter size at birth was carried out in rabbits during twelve generations. Residual variance of litter size was estimated as the within-doe variance of litter size after pre-correction for year and season as well as parity and lactation status effects. The aim of this work was to study the correlated response to selection for litter size residual variability in body condition from mating to weaning. Body condition is related directly to an animal’s fat deposits. Perirenal fat is the main fat deposit in rabbits. Individual body weight (IBW) and perirenal fat thickness (PFT) were used to measure body condition at second mating, delivery, 10 days after delivery, and weaning. Litter size of the first three parities was analyzed. Both lines decreased body condition between mating to delivery; however, the decrease in body condition at delivery was lower in the low line, despite this line having higher litter size at birth (+0.54 kits, p = 0.93). The increment of body condition between delivery and early lactation was slightly higher in the low line. On the other hand, body condition affected success of females’ receptivity and fertility at the third mating, e.g., receptive females showed a higher IBW and PFT than unreceptive ones (+129 g and +0.28 mm, respectively), and fertile females had a higher IBW and PFT than unfertile ones (+82 g and +0.28 mm, respectively). In conclusion, the does selected for reducing litter size variability showed a better deal with situations of high-energy demand, such as delivery and lactation, than those selected for increasing litter size variability, which would agree with the better health and welfare condition in the low line.

Rabbit Lines Divergently Selected for Total Body Fat Content: Correlated Responses on Growth Performance and Carcass Traits

The aim of this experiment was to study the effect of divergently selected rabbits for total body fat content (fat index) on growth performance and carcass traits. The fat index was determined at 10 weeks of age by computed tomography and lasted for four consecutive generations. The rabbits with the lowest fat index belonged to the lean line and those of the highest values belonged to the fat line. At generation four, 60 rabbits/line were housed in wire-mesh cages and fed with commercial pellet ad libitum from weaning (5 w of age) to slaughtering (11 w of age). Growth performance, dressing out percentage and carcass adiposity were measured. The lean line showed a better feed conversion ratio (p < 0.001) than the fat line. Furthermore, the carcass of the lean rabbits had the highest proportion of fore (p < 0.020) and hind (p < 0.006) parts. On the contrary, rabbits of the fat line had the highest carcass adiposity (p < 0.001). The divergent selection for total body fat content showed to be effective for both lean and fat lines. Selection for lower total body fat content could be useful for terminal male lines, while the selection for higher total body fat content could be an advantage for rabbit does in providing fat (energy) reserves.

Correlated response in body condition and energy mobilisation in rabbits selected for litter size variability

A divergent selection experiment on litter size variability (high and low lines) was performed in rabbits over seven generations. The aim of this study was to evaluate the correlated responses to selection in body condition and fat reserves mobilisation. Litter size variability was estimated as phenotypic variance of litter size within female after correcting for the year-season and the parity-lactation status effects. A total of 226 females were used in this study, of which 158 females were used to measure body condition and energy mobilisation. Body condition was measured as BW and perirenal fat thickness. Females were stimulated with the adrenergic isoproterenol. Mobilisation capacity of fat reserves was measured by the lipolytic potential, defined as the increment in non-esterified fatty acids (NEFA) levels from basal concentration until adrenergic stimulation at mating, delivery and 10 days after delivery of the second reproductive cycle. Females were classified as survivor or non-survivor when they were culled for sanitary reasons or died before the third kindling. Data were analysed using Bayesian methodology. Survivor females presented higher BW than the non-survivor females at delivery (238 g, P=1.00) and 10 days after delivery (276 g, P=1.00). They also showed higher perirenal fat thickness at 10 days after delivery (0.62 mm, P=1.00). At delivery, basal NEFA levels was lower in survivor than non-survivor females (-0.18 mmol/l, P=1.00), but their lipolytic potential (∆NEFA) was higher (0.08 mmol/l, P=0.94). Body weight was similar between lines in survivor females. Perirenal fat thickness was lower in the high line than in the low line at delivery (-0.23 mm, P=0.90) and 10 days after delivery (-0.28 mm, P=0.92). The high line exhibited higher NEFA (0.10 mmol/l, P=0.93) and lower ∆NEFA (-0.08 mmol/l, P=0.92) than the low line at delivery. The low line showed a favourable correlated response to selection on body condition and fat reserves mobilisation. In conclusion, the low line selected for litter size variability seems to adapt better to adverse conditions, as it has a greater capacity to mobilise energy reserves at delivery than the high line. Females that adequately manage their body reserves and perform energy mobilisation correctly have a lower risk of dying or being culled.

Long-term implications of feed energy source in different genetic types of reproductive rabbit females: III. Fitness and productivity

The specialization process associated with genetic selection could be associated with functional disorders, affecting the reproductive success of females (fitness). We hypothesized that by modulating energy acquisition and allocation of females we could balance productivity and reproductive success. To test this hypothesis, we used 203 rabbit females belonging to three genetic types: H (n=66) maternal line specialized in prolificacy, LP (n=67) generalist maternal line, R (n=70) paternal line specialized in growth rate. We fed each genetic type with two diets specifically designed to promote milk yield (AF) or body reserves recovery (CS). We controlled females between their first and fifth reproductive cycles, recording traits related with productivity and fitness of females. H females fed CS had on average 11.2±0.43 kits with an individual weight of 54±1.2 g at birth and 525±11 g at weaning. Their conception rate when multiparous was 44% and their survival rate at the end of the experiment 30%. When they were fed AF, the individual weight of kits was 3.8 g heavier (P<0.05) at birth and 38 g heavier at weaning (P<0.05), the conception rate when multiparous increased 23 percentage points (P<0.05) and the survival rate at the end of the experiment 25 percentage points (P<0.05). LP females fed CS had on average 10.8±0.43 kits with an individual weight of 52±1.2 g at birth and 578±11 g at weaning. Their conception rate when multiparous was 79% and their survival rate at the end of the experiment 75%. When they were fed AF, it only increased individual weight of kits at weaning (+39 g; P<0.05). R females fed CS had on average 8.4±0.43 kits with an individual weight of 60±1.2 g at birth and 568±11 g at weaning. Their conception rate when multiparous was 60% and their survival rate at the end of the experiment 37%. When they were fed AF, they presented 1.4 kits less at birth (P<0.05) but heavier at birth (+4.9 g; P<0.05) and at weaning (+37 g; P<0.05). Therefore, we observed that genetic types prioritized different fitness components and that diets could affected them. In this sense, seems that more specialized genetic types, were more sensitive to diets than the more generalist type.

Long-term implications of feed energy source in different genetic types of reproductive rabbit females: I. Resource acquisition and allocation

To achieve functional but also productive females, we hypothesised that it is possible to modulate acquisition and allocation of animals from different genetic types by varying the main energy source of the diet. To test this hypothesis, we used 203 rabbit females belonging to three genetic types: H (n=66), a maternal line characterised by hyper-prolificacy; LP (n=67), a maternal line characterised by functional hyper-longevity; R (n=79), a paternal line characterised by growth rate. Females were fed with two isoenergetic and isoprotein diets differing in energy source: animal fat (AF) enhancing milk yield; cereal starch (CS) promoting body reserves recovery. Feed intake, weight, perirenal fat thickness (PFT), milk yield and blood traits were controlled during five consecutive reproductive cycles (RCs). Females fed with CS presented higher PFT (+0.2 mm, P0.05), particularly for those fed with AF. Moreover, LP females fed with AF progressively increased PFT across the RC, whereas those fed with CS increased PFT during early lactation (+7.3%; P<0.05), but partially mobilised it during late lactation (-2.8%; P<0.05). Independently of the diet offered, LP females reached weaning with similar PFT. H females fed with either of the two diets followed a similar trajectory throughout the RC. For milk yield, the effect of energy source was almost constant during the whole experiment, except for the first RC of females from the maternal lines (H and LP). These females yielded +34.1% (P<0.05) when fed with CS during this period. Results from this work indicate that the resource acquisition capacity and allocation pattern of rabbit females is different for each genetic type. Moreover, it seems that by varying the main energy source of the diet it is possible to modulate acquisition and allocation of resources of the different genetic types. However, the response of each one depends on its priorities over time.

Energy balance and body reserves in rabbit females selected for longevity

<p>The aim of this study was to compare the energy balance and dynamic of body reserves in rabbit females divergently selected for longevity. One hundred and twenty-nine females from a high longevity line (HL) and 131 females of a low longevity line (LL) were studied from the 1^st to the 3^rd kindling. Litter size and weight and female body weight were measured at kindling (1^st, 2^nd and 3^rd), insemination (2^nd and 3^rd) and at weaning (1^st and 2^nd). The total body electric conductivity (TOBEC) method was used to estimate the body reserves in all females at artificial insemination and at weaning, and at kindling in females that achieved parturition. Energy balance between the 11^th and the 21^th d of lactation was also calculated for these females. No significant difference was found for fertility or for the number of offspring born alive and weaned. However, the total number of offspring born was higher in the LL line than in the HL line at the 2^nd parturition (+1.12±0.46 g; P&lt;0.05). Consequently, the number of stillborn offspring was higher in the LL line. LL females were 4% heavier than HL females at the first parturition (P&lt;0.05), but then HL females had a higher live weight gain than LL females from the 1st parturition to the 2^nd artificial insemination (+107.0±29 g; P=0.049), leading to a similar weight between the lines at the 2^nd artificial insemination. There was no significant difference between lines for estimated energy used for growth between the 11^th and the 21^th d of lactation, or for estimated milk production (2365±30 g in HL line vs. 2398±30 g in LL line), estimated using the weight gain of the kits between the 11^th and 21^st d of lactation, for feed intake measured during this period (351±5 g/d in HL line vs. 359±5 g/d in LL line) or for energy balance (–6.11±0.3 MJ in HL line vs. –6.30±0.3 MJ in LL line). However, body energy content was higher in HL females than in LL (+2.72±0.64 MJ; P=0.001). In conclusion, selection for higher functional longevity results in a better ability of females to use body reserves in their early reproductive life.</p>

Relationship between body condition and energy mobilization in rabbit does

<p>The present work was performed to examine the relationships between measures of body condition and energy mobilization in rabbit does. The variables studied were body weight (BW), perirenal fat thickness (PFT), basal non-esterified fatty acid concentration (NEFA_b) and non-esterified fatty acids after lipolysis stimulation by isoproterenol (NEFA_r). The effect of time of measuring (at mating, delivery and 10 d after delivery) was estimated in 157 primiparous does. Correlations between body condition components were estimated and a principal component analysis performed. The does decreased BW (6%) and PFT (3%), and increased NEFA_b (25%) and NEFA_r (16%) from mating to delivery. Later, NEFA_b and NEFA_r decreased around 20% from delivery to 10 d after delivery without changing perirenal fat thickness. All BW and PFT lay in the first principal component, and all NEFA traits lay in the second component, showing low correlations with body condition measurements. Both NEFA traits showed high positive correlations when measured at the same time (0.65, 0.72 and 0.69), but low correlations when measured at different times (0.09, to 0.20). We conclude that although body weight and perirenal fat thickness are good predictors of body condition, NEFA should be used when an accurate measurement of energetic mobilization is needed, due to their low correlation.</p>

Patterns of body condition use and its impact on fertility

<p>A total of 60 nulliparous crossbred rabbit females were, a posteriori, divided into 2 experimental groups according to their natural “decision” to conceive or not at day 11 post first parturition (L: solely-lactating or LP: lactating-pregnant). This design allowed us to study the evolution of body reserves around first parturition and its influence on the future reproductive success of rabbit females. Primiparous rabbit females that failed to conceive when inseminated at day 11 post-partum (L) seemed to have a higher perirenal fat thickness (PFT) 12 d pre-partum (+0.25 mm; P=0.079) than females that conceived (LP). In the subsequent days, L females showed a significantly higher mobilisation rate than LP females (on av.–0.12 and –0.07 mm of PFT per day, respectively; P=0.007), reaching a lower PFT at partum (5.17 mm vs. 5.62 mm, respectively; P = 0.002). However, due to a greater recovery rate observed in L females (+0.15 vs. +0.08 mm of PFT per day for L and LP females, respectively; P=0.007), PFT at 10 d post-partum was similar (on av. 5.86 mm). These different patterns showed that PFT level at 12 d pre-partum and PFT mobilisation rate onwards seems to drive the start of a new pregnancy. It also seems to modify the energy metabolism of rabbit females, allowing does to recover perirenal fat tissue without compromising the production of milk necessary for the current litter.</p>

Reproductive robustness differs between generalist and specialist maternal rabbit lines: the role of acquisition and allocation of resources

Background

Farm animals are normally selected under highly controlled, non-limiting conditions to favour the expression of their genetic potential. Selection strategies can also focus on a single trait to favour the most ‘specialized’ animals. Theoretically, if the environment provides enough resources, the selection strategy should not lead to changes in the interactions between life functions such as reproduction and survival. However, highly ‘specialized’ farm animals can be required for breeding under conditions that differ largely from selection conditions. The consequence is a degraded ability of ‘specialized’ animals to sustain reproduction, production and health, which leads to a reduced lifespan. This study was designed to address this issue using maternal rabbit lines. A highly specialized line with respect to numerical productivity at weaning (called V) and a generalist line that originated from females with a long reproductive life (called LP) were used to study the strategies that these lines develop to acquire and use the available resources when housed in different environments. In addition, two generations of line V, generations 16 and 36, were available simultaneously, which contributed to better understand how selection criteria applied in a specific environment changed the interplay between functions related to reproduction and survival.

Results

We show that, under constrained conditions, line LP has a greater capacity for resource acquisition than line V, which prevents excessive mobilization of body reserves. However, 20 generations of selection for litter size at weaning did not lead to an increased capacity of nutrient (or resource) acquisition. For the two generations of line V, the partitioning of resources between milk production, body reserves preservation or repletion or foetal growth differed.

Conclusions

Combining foundational and selection criteria with a specific selection environment resulted in female rabbits that had a different capacity to deal with environmental constraints. An increased robustness was considered as an emergent property of combining a multiple trait foundational criterion with a wide range of environmental conditions. Since such a strategy was successful to increase the robustness of female rabbits without impairing their productivity, there is no reason that it should not be applied in other livestock species.

A robust rabbit line increases leucocyte counts at weaning and reduces mortality by digestive disorder during fattening

The present work evaluates how a rabbit line selected for robustness and two other lines selected for productive criteria, could have affected the physiological maturity and blood leukocytes counts of young rabbits at weaning, as well as their possible effect on the subsequent performance and health status during the growing period. The study was conducted on a total of 2904 young rabbits weaned at 30 days, belonging to three different genetic types (line H, founded for litter size at birth and selected for litter size at weaning during 17 generations; line LP, characterised by robustness founded for reproductive longevity criteria and selected for litter size at weaning for 7 generations; and line R, founded and selected during 25 generations for average daily gain from the 4th to the 9th week of life). Two different diets were used during lactation. The two diets were both isoenergetic and isoprotein but their main energy source differed, being either animal fat (AF) or cereal starch (CS). Leucocyte subsets were characterised at weaning, and growing performance was studied until 58 days of age (feed intake, live weight, mortality by digestive disorders and morbidity) for both medicated and non-medicated dietary versions. At weaning, young rabbits fed an AF lactating diet evidenced greater B lymphocyte count (on av. +8.6 ± 3.5 × 10(6)/L; P < 0.05) than those fed a CS diet. With respect to H and R rabbits, blood from LP ones had higher counts for total (on av. 591 ± 167 × 10(6)/L; P < 0.05), B (on av. +11.05 ± 4.3 × 10(6)/L; P < 0.05), T CD5(+) (on av. +266 ± 83 × 10(6)/L; P < 0.05) and CD8(+) lymphocytes (on av. +72.5 ± 28 × 10(6)/L; P < 0.05), and with respect to R, higher counts of CD4(+) (on av. +121 ± 47 × 10(6)/L; P < 0.05) lymphocytes (on av. +12.3 ± 4.1 × 10(6)/L; P < 0.05), monocytes (on av. +66 ± 32 × 10(6)/L; P < 0.05) and granulocytes (on av. +567 ± 182 × 10(6)/L; P<0.05) at weaning. LP line rabbits also showed lower mortality by digestive disorders (on av. -8 points of percentage) and morbidity (on av. -4 points) than those from H and R lines during the growing period (P < 0.05). R animals presented higher feed intake and daily weight gain, and a lower feed conversion ratio than H and LP animals (on av. +16.7 ± 2.7 g dry matter/day, +10.3 ± 0.4 g/day and -0.22 ± 0.04 g dry matter/g, respectively). In conclusion, the foundation of a line for reproductive longevity, which has been previously reported to give greater robustness (low environmental sensitivity) to their reproductive stock, could have conferred higher leukocytes counts at weaning to their offspring, as well as a better ability to confront digestive disorders as compared to other lines founded or selected exclusively for productive criteria.

Comparison of immune response to lipopolysaccharide of rabbit does selected for litter size at weaning or founded for reproductive longevity

To evaluate differences in maternal lines to the immune response of reproductive rabbit does, a total of 64 animals of two different lines: (1) founded for hyper-longevity and litter size criteria (LP) and (2) selected for litter size at weaning (V) were used. Females were subjected to three different reproductive efforts: post-partum (PP) mating at first lactation and 9 kits during the second; post-weaning (PW) mating at first lactation and 9 kits during the second; and PW mating at first lactation and 5 kits during the second. At second weaning (30 days PP), an acute response was induced by intravenous infusion of lipopolysaccharide (LPS). LP females seemed to be lower affected during the hyper-acute phase than V females, showing lower plasma glucose content at 1.5 h post infusion (pi) and rectal temperature at 6 h pi; and showed higher ulterior immune response, with higher levels of C-reactive protein at 48 h pi and haptoglobin in plasma from 24 h pi. Survival test conferred a higher risk of culling for V than for LP females during the first hours after challenge. These results may suggest that, regarding immune response to LPS challenge, foundation by hyper-longevity productive criteria lead to obtain a more robust population of rabbit does, characterized by improved response ability.

Body weight and body condition of breeding rabbits in commercial units

Live BW and BCS data were collected from 2,775 breeding rabbits (644 males and 2,131 females) of 34 genetic types and sorted according to their specialization (maternal, paternal, and others). Data were gathered on 66 visits to 43 commercial farms in Spain between 2009 and 2011. Mean BW was 4.72 kg (range of 2.87 to 8.13 kg, with a median BW of 4.60 kg) and mean BCS was 4.6 (range of 1.0 to 9.0, with a median BCS of 5.0). females had heavier (P < 0.05) BW than males and paternal lines of rabbits had greater (P < 0.05) BW than maternal lines and other breeds/lines not selected for meat production. Between 69.3% and 75.4% of the rabbits were deemed healthy by a veterinarian and, as expected, healthy rabbits were heavier (P < 0.05) than sick rabbits diagnosed with rhinitis, mastitis, sore hocks, and several other diseases. Among purebred, maternal lines of rabbits, Hyplus GD24, UPV A, and UPV V were heavier (P < 0.05) than hyplus GD14 and Hyla HL-D lines, and line UPV R had the greatest (P < 0.05) BW among the purebred, paternal lines. Additionally, A×H, A×V, PS19, and P×A crossbreds had greater (P < 0.05) BW than HE-C×D, HL-C×D, H×V, LP×V, and V×P crossbreds among the maternal lines, whereas HE-SL were the heaviest (P < 0.05) crossbred paternal line of rabbits. Additionally, females received greater (P < 0.05) BCS than males and BCS were greater (P < 0.05) in healthy than sick rabbits. Moreover, maternal lines had smaller (P < 0.05) BCS than either paternal lines or other lines/breeds not selected for meat production. Results also indicated a moderate relationship between BCS and BW (r = 0.32), with a 1-point change in BCS equivalent to an ~ 245-g change in BW. results from this study can be used as baseline figures for breeding rabbits in spain and are essential factors in several decisions concerning housing, feeding, reproduction, health, and welfare of breeding rabbits.

Health and body condition of lactating females on rabbit farms

The aim was to study relationships between morbidity, defined through prevalence of diseases of rabbit females, and BCS, and to assess the effect of several risk factors on both morbidity and BCS. Our study was based on individual examinations of 18,510 does in lactation on 103 farms. We evaluated BCS on a linear scale from 1 to 9, with 5 being the optimum. Prevalence of major diseases were 22.7%, 4.0%, and 6.4% for coryza, mastitis, and ulcerative pododermatitis, respectively. In addition, prevalence was 3.0% for diseases of minor presentation, including mange, which had a prevalence of 1.9%. The BCS of the R line (selected for growth) was 5.55 ± 0.14, whereas for the A line (selected for litter size) it was 4.40 ± 0.11. Females with more than 20 kindlings had on average a BCS 0.25 ± 0.07 units less than those in the 12th lactation (P = 0.0002). Optimal BCS 4.60 ± 0.11 was reached during the third lactation week. Sick females had a BCS of 0.6 ± 0.01 units less than healthy females. Females with a footrest had on average a BCS 0.19 ± 0.05 units greater than those without. The absence of footrests was an enabling risk factor for ulcerative pododermatitis, the prevalence of which increased by 53%. Ulcerative pododermatitis was associated (P = 0.045) with diet; females consuming a rich energy diet were prone to having this disorder; 1 SD increase in DE (0.32 MJ) determined an increase in ulcerative pododermatitis prevalence of 0.8 percentage points. Diet was not an enabling risk factor for the other diseases. The genetic type to which a female belongs is a predisposing risk factor of disease; P, V and H were also maternal lines, while S group was exclusively formed by maternal lines. With regard to coryza, the S group had the greatest prevalence (44.0%), followed by A, P, R (19.0 to 21.0%); the V line, selected for prolificacy, showed the least prevalence (12.0%). For the case of mastitis although significant (P < 0.05), the magnitude of the differences between disease prevalence was less; R line had a mastitis prevalence of 11.0% while the least prevalence was observed for V does (4.0%). Simultaneous evaluation of both BCS and morbidity on the rabbit farm is recommended for the right assessment of welfare conditions. In this study, the relationships between both variables have been shown, as well as how other intrinsic and extrinsic risk factors modulate these variables; and thus, these factors should be considered during a welfare assessment.