Insights into suckling rabbit feeding behaviour: acceptability of different creep feed presentations and attractiveness for sensory feed additives

In young rabbit, digestive disorders are frequently observed around weaning. Stimulating the onset of feed intake in the suckling rabbit might be a way to promote gut health. The aim of this study was to determine the rabbit’s acceptability for different feed presentations and its preferences for flavours at an early stage of life. Two trials were conducted to evaluate the effects of physical form and flavouring on creep feed attractiveness. All the diets tested were provided in the nest from 3 to 17 days, and the daily intake per litter was recorded as of 8 days of age. In the first trial, five feed presentations were tested separately (n = 60 litters). Three dry presentations were chosen: commercial pellet (P), crumb from commercial pellet (cP) and crumb from beet pulp pellet (cBP). Hydrated feeds were also provided with either raw fodder beetroot (B) or a semi-solid feed in agar gel form produced with fodder beetroot juice and pulp (gB). In the second trial, double-choice tests were performed on four feed gels (n = 72 litters), leading to six comparison treatments. These agar gels were made of pellet mash without or with a sensory additive: one non-odorised control gel and three gels with 0.20% banana flavour, 0.06% red berry flavour and 0.10% vanilla flavour, respectively. In the first trial, kits ate more gB in fresh matter than other feed presentations (P < 0.001), with a total intake of 7.0 ± 1.8 g/rabbit from 8 to 17 days. In DM, the total consumption of pellets P (1.6 ± 0.4 g of DM/rabbit) was the highest together with the gB form (1.4 ± 0.4 g of DM/rabbit), whereas cBP was barely consumed (0.3 ± 0.1 g of DM/rabbit). Gel feed supplemented with vanilla was slightly more consumed than other flavoured and non-odorised gels (relative consumption of 57% when compared to control gel; P = 0.001). The gel feed intake was independent of the milk intake but was correlated with the litter weight at 3 days (r = 0.40, P < 0.001). In both trials, rabbit growth before and after weaning was not affected by the type of creep feed provided. Our results confirmed that providing creep feed promotes the solid intake of rabbits at early stages. Gel feed form motivated rabbits to eat and vanilla flavour supplementation increased the feed palatability. Those creep feed characteristics should be explored further for seeking effective stimulation of the onset of the feed intake in suckling rabbit.     

Influence of gestational maternal feed restriction on growth performance and meat quality of rabbit offsprings

The purpose of the present study was to evaluate the effect of feed restriction during pregnancy on reproductive performance of rabbit does and growth performance and meat quality of their offspring. A total of 26 primiparous non lactating does were equally divided into two treatment groups: the control group (C, n=13) that was fed ad libitum throughout gestation and the feed restricted group (R, n=13) that was fed to 75% of maintenance energy requirements from the 7^th to the 26^th day of gestation. Rabbit offsprings were weaned at 35 days of age and grown until the 72 days of age when they were slaughtered for meat quality assessment. Meat quality traits measured were pH₂₄, colour (L*, a*, b*), percentage of released water, cook loss, shear values and intramuscular fat. At kindling, R does produced smaller litter weights compared with those of does from group C, 447.8 and 591.4 g, respectively, and smaller individual kit birth weights, 56.2 and 71.5 g, respectively (P<0.05). Ratio of stillborn kits and mortality rate from parturition until weaning was higher (P<0.05) in the R group, 21.4% and 11.1%, respectively, in comparison with the C group, 8.1% and 3.5%, respectively. Litter size and gestation length were unaffected by maternal undernutrition. Kit birth weight treatment differences were eliminated at weaning because of compensatory growth (P>0.05). Performance and meat quality characteristics of fattening rabbits at 72 days of age were not influenced by gestational feed restriction of their mothers (P>0.05). Taking into consideration that, simultaneous gestation and lactation in rabbit does may be simulated by gestational feed restriction, results of the present study suggest that lactating does can support a simultaneous gestation without any adverse effect on the offsprings’ quantitative and qualitative performance at the expense of increased mortality rates at parturition and until weaning.     

The effect of level of feeding in early gestation on reproductive success in young rabbit does

An experiment examined the effect of restricted feeding during early gestation on later feed intake and on kindling performance in young rabbit does. Nulliparous rabbit does (n=94) were inseminated at 14.5 weeks of age. During the first 10 days of gestation, does were fed individually either to appetite (AL) or 1.35 times maintenance requirement (R). After 10 days of gestation, all animals were fed to appetite. Does were weighed at insemination and after kindling. Feed intake was recorded during the first 10 days of gestation and weekly, thereafter. The number of does that kindled, number of live and stillborn kits and litter weight was recorded. The experiment ended after kindling. During feed restriction, AL does consumed 70 g/day more on an average than R does (209 and 139+/-4 g for AL and R, respectively; P<0.001). In the first and second week after feed restriction, compensatory feed intake occurred. Restrictive fed does ate more than AL does (+34+/-5 g/day from days 11 to 17 of gestation; P<0.001; +17+/-6g/day from days 18 to 24 of gestation; P<0.05). In the last week of gestation, feed intake of AL and R was comparable (89 and 100+/-5 g, respectively). At kindling, AL does had consumed 8+/-3g/day more feed over the total gestation period than R does (P<0.04). Feeding level during early gestation neither affected the kindling rate (83%), total litter size (7.9+/-0.4) nor the number of does with stillborn kits (10 versus 9 for AL and R, respectively). Regardless of treatment, in the last week of gestation (days 25-32) the number of does with stillbirth was lower and average birth weight was higher (P<0.01) in does eating more than the average daily feed intake compared to does eating below average. Based on the results of this study it was concluded that feed restriction for 10 days in early gestation does not affect kindling performance of young does, but feed intake in the last week of gestation affects kit survival and birth weight.     

Performance and welfare of rabbit does in various caging systems

The objective of the study was to compare production and welfare of rabbit does and their kits housed in various types of cages. Female rabbits were randomly allocated to four groups with the following cage types: CN: common wire-mesh flat-deck cage, without footrest; CF: cage similar to the CN but with plastic footrest; ECWP: enlarged cage with wire-mesh platform; and ECPP: extra enlarged cage with plastic-mesh platform. All does were inseminated on the same day, 11 days after kindlings. Reproductive performance was evaluated during the first five consecutive kindlings. Severity of sore hocks was scored at each insemination. Location preference of the does and the platform usage of their kits were evaluated. Kindling rate, litter size (total born, born alive, alive at 21 and 35 days) and kit mortality were not significantly influenced by the cage types. The litter weight at 21 days was higher in ECWP and ECPP cages than in the CF group (3516, 3576 and 3291 g, respectively; P<0.001), and at 35 days the difference was only significant between the groups ECPP and CF (8712 and 8060 g, respectively, P<0.05). At 21 and 35 days of age, the kits were heavier in large (ECWP and ECPP) than in conventional cages (CF and CN) (P<0.001). At the fifth insemination, the percentage of rabbits with sore hocks’ score of 1 to 2 (0=intact foot pads; 1=no hairs, callus formed, <2.5 cm; 2=no hairs, callus formed, >2.5 cm) and 3 to 4 (3=callus opened, cracks present; 4=wounds) were 58%, 60%, 78% and 48%, and 0%, 5%, 0% and 48% in groups ECPP, ECWP, CF and CN, respectively. Higher number of daily nest visits was observed for CF does than for ECWP does (12.5 v. 5.9; P<0.05). The frequency of multiple nursing events (>2/day) was higher in the CF group than in the ECWP group (12.1 v. 3.2%; P<0.01). Within large cages, the does were observed on the platform more frequently in the ECPP cages compared with the ECWP cages (56.9% v. 31.7%; P<0.001). Similarly, 2.7% and 0.2% of kits at 21 days of age, and 33.2% and 5.2% of kits at 28 days of age, were found on the platforms of ECPP and ECWP cages, respectively. In conclusion, cages larger than the conventional ones improved kits’ weaning weight, plastic footrests and plastic-mesh platforms in conventional and/or large cages reduced sore hocks’ problems, plastic-mesh platforms were more used by both does and kits compared with the wire-mesh platforms.     

Comparison of performance and welfare of single-caged and group-housed rabbit does

Although rabbit does are generally single housed on rabbit farms worldwide, it has been suggested by some specialists and recommendation of organic rabbit production systems that group housing of does is more comfortable and similar to the living conditions of the European wild rabbits. The aim of this experiment was to compare production of single-caged (S) and group-housed does (G). The S does were housed in commercial rabbit cages (floor area 0.32 m² and 0.3 m high). In treatment G, four does and one buck were housed in four pens measuring 7.7 m² (half of the floor was deep litter and the other half was plastic slat), with four nest boxes in each pen (n = 16). In treatment S, approximately half of the does (n = 18) were inseminated 2 days after kindling (S-33), whereas in the remaining does (n = 16) AI was done 11 days after kindling (S-42). A single-batch system (all of the does in the group were inseminated on the same day) was used in both S treatments. Kindling rates were 77.6%, 85.2% and 45.6% in treatments S-33, S-42 and G, respectively (P < 0.05). During the experiment, the percentage of does that kindled 0, 1, 2, 3, 4 and 5 times were 17%, 25%, 17%, 25%, 17% and 0% (G); 0%, 0%, 0%, 8%, 69% and 23% (S-33); and 0%, 0%, 17%, 58% and 25% (S-42, in this treatment does had a maximum of four kindlings). There were no significant differences among treatments for litter size. In treatments S-33, S-42 and G, suckling mortality was 14.0%, 15.2% and 38.5%, respectively (P < 0.001); survival of does was 71%, 81% and 50% (P = 0.084); and faecal corticosterone concentrations were 61, 54 and 175 nmol/g (P < 0.001). The high mortality of kits was associated with stress and aggressive behaviour of does, including scratching, biting or killing the kits, which resulted in the high rates of mortality and culling, as well as shorter lifespan of does. Because of high stress, increased mortality and morbidity, and low productivity, group housing of rabbit does resulted in poorer animal welfare and increased production costs, and therefore is not recommended.     

Effect of litter size on prepartum metabolic and amino acidic profile in rabbit does

The use of modern prolific lines of rabbit does in intensive production systems leads to an increase in productivity but also causes a rise in several problems related to the does’ health status. Hence, the aim of this study was to investigate the effect of the litter size on the metabolic, inflammatory and plasma amino acid profile in rabbit does. The blood of 30 pregnant does was sampled on the 27th day of pregnancy. The does were retrospectively grouped according to the number of offspring into a high litter size group (HI, does with ≥ 12 kits; n= 16) and a low litter size group (LO, does with ≤ 11 kits; n= 14). Data were subjected to Pearson’s correlation analysis. Further, data were analysed in agreement to a completely randomized design in which the main tested effect was litter size. The linear or quadratic trends of litter size on parameters of interests were post hoccompared by using orthogonal contrasts. In addition, compared with the LO group, the HI group had lower levels of glucose (−5%; P< 0.01), zinc (−19%; P< 0.05), albumin (−6%; P< 0.05) and total cholesterol (−13%; P< 0.07), but the total bilirubin level was higher in the HI group (+14%; P< 0.05). Regarding the plasma amino acids, the HI group had lower concentrations of threonine (−15%), glycine (−16%), lysine (−16%) and tryptophan (−26%) and a higher level of glutamic acid (+43%; P< 0.05) compared with the LO group. The exclusively ketogenic amount of amino acids was lower (P< 0.06) in the HI (55.8 mg/100 ml) does compared with the LO does (56.8 mg/100 ml). These results show that a few days before delivery, rabbit does that gave birth to a higher number of offspring had a metabolic profile and an inflammatory status that was less favourable with respect to does who gave birth to a lower number of offspring. Moreover, the plasma amino acid profile points out that there was an enhanced catabolic condition in the rabbit does with a high number of gestated foetuses; it was likely related to the greater energy demand needed to support the pregnancy and an early inflammatory response.     

Early solid additional feeding of suckling rabbits from 3 to 15 days of age

Studies have shown that nutrient requirement of suckling kits is not satisfied, but they can be fed a double quantity of milk (double nursing) resulting in improved BW and weight gain. The aim of our trials was to give additional solid feed during the early suckling period (3 to 15 days of age) when rabbit kits drink exclusively milk. Two experiments were conducted with animals from Pannon Rabbit Breeding Program. In experiment 1 (n=77 does, 734 kits) the does received commercial feed (C) or C pellet supplemented with 0.2 g powdered thyme/kg (CT). Within both dietary groups of the does three groups of litters were formed: no additional solid creep feeding (N); soya bean-based pellet (S); S pellet with 1% added powdered thyme (ST). In group S and ST, cylinder-shaped solid pellets were made. At the beginning (3 days of age) two pieces of pellets were placed daily into the nestbox after nursing. Later on it was increased to six pellets till 15 days of age. The kits consumed the additional solid feed (S and ST), however, it did not affect the BW, weight gain or survival. In experiment 2 (n=30 does, 240 kits) all does consumed commercial feed. The additional feed for kits was based on commercial piglet feed. Three groups were formed: the litters in control group were fed no additional solid feed (K), kits were fed additionally with pellets (8 mm of diameter) based on piglet feed powder, pellet adhesive and water (PI), and extra glycerin powder was added to the mixture of piglet feed powder and water (PG). The experiment lasted from the age of 3 days till 21 days. At the beginning six pellets were placed on the nest material. Later on the amount was gradually increased to 24 pellets till age of 15 days. The kits consumed the pellets. The BW of PI group differed from group PG at age of 5, 9, 12 and 21 days by +7.3%, +6.5%, +5.9%, +4.8%, respectively (P<0.05) and from group K at age of 12 days by +5.9% (P< 0.05). The differences were more expressed at age of 16 and 19 days in favour of group PI (from K by +7.1%, +6.9% and from PG by +5.9%, +5 8%, respectively, P<0.01) and at 21 days of age (from K by +6.2%, P<0.01). To find appropriate composition of creep feed for kits further studies are needed.     

Metabolic and biochemical changes in plasma of the periparturient rabbit does with different litter size

The aim of this study was to investigate the metabolic and biochemical changes in plasma that occur in the reproductive rabbit doe close to the parturition, as well as if the number of offspring affects the metabolism and the health status of the doe. At −3, 4 and 12 days from parturition (–D3, D4, and D12, respectively) nine rabbit does at their third parity from a commercial hybrid line (HYPLUS PS 19) selected for high prolificacy were weighted and blood was collected for a wide inflammometabolic profile. According to the number of offspring the does were retrospectively divided in two groups: high litter size group (HI; n=5) and low litter size group (LO; n=4). BW was higher (P<0.01) at –D3 and had the lowest values at D4. At D12, the BW was lower (P<0.05) in LO compared with HI. Several metabolites significantly changed from dry to lactation period. Glucose and cholesterol had the lowest levels at –D3; non-esterified fatty acid (NEFA) and aspartate aminotransferase had the highest values before parturition (P<0.05); creatinine and β-hydroxybutyrate (BHBA) were higher at –D3 with respect to D4 (P<0.05). The lowest value of paraoxonase was observed in does at –D3 (P<0.05), whereas at this time ceruloplasmin and total bilirubin had the highest concentration (P<0.05). The differences for blood profile parameters between does grouped according to litter size were mainly evident before parturition (–D3). In particular, BHBA, NEFA and total bilirubin had higher concentrations (P<0.05) in HI v. LO group, whereas albumin and PON were lower in HI group (P<0.01). After parturition there were no significant differences for the metabolic parameters between the two groups. The results show that for reproductive rabbit doe the last days of gestation are very stressful from a metabolic and inflammatory point of view. The genetic selection of does for higher litter size has increased their ability to mobilize body reserves in order to guarantee the nutrients to a high number of kits. This exposes them to a more severe metabolic and inflammatory challenge during the transition period. Consequently, feeding and managerial strategies for high prolificacy periparturient rabbit does should be revised.     

Effects of Gestational Maternal Undernutrition on Growth,Carcass Composition and Meat Quality of Rabbit Offspring

An experiment was conducted in order to evaluate the effects of gestational undernutrition of rabbit does on growth, carcass composition and meat quality of the offsprings. Thirty primiparous non lactating rabbit does were artificially inseminated and randomly divided in three treatment groups: Control (C; fed to 100% of maintenance requirements throughout gestation, n = 10), early undernourished (EU; fed to 50% of maintenance requirements during days 7–19 of gestation, n = 10) and late undernourished (LU; fed to 50% of maintenance requirements during days 20-27 of gestation, n = 10). During the 4^th week of the gestation period, LU does significantly lost weight compared to C and EU groups (P<0.05). At kindling, C does produced litters with higher proportions of stillborn kits (P<0.05) while the total litter size (alive and stillborn kits) was not different among groups (10.7, 12.8 and 12.7 kits in C, EU and LU groups, respectively). Kit birth weight tended to be lower in the LU group. During fattening, body weight and feed intake were not different among offsprings of the three experimental groups. Moreover, the maternal undernutrition did not have any impact on carcass composition of the offsprings in terms of carcass parts and internal organs weights as well as meat quality of L. lumborum muscle (pH24, colour, water holding capacity and shear values) at slaughter (70 days of age). Therefore, it can be concluded that the gestational undernutrition of the mother does not have detrimental effects on the productive and quality traits of the offsprings.     

Impact of feed restriction and fragmented feed distribution on performance,intake behaviour and digestion of the growing rabbit

Postweaning feed restriction preserves rabbit digestive health after weaning, but the underlying physiological mechanisms are not yet understood. To elucidate whether the feeding intake pattern modification related to feed restriction might be involved, we studied the effects of both feed intake quantity and intake frequency. Animals were allotted at weaning (28 d old) in a 2 × 2 factorial design: feed intake quantity (AL = ad libitum vs R = 75% of AL) and fragmented feed distribution (FFD) (1 vs 13 distributions), thus forming four groups (AL1, AL13, R1 and R13). New Zealand White growing rabbits were used from weaning to slaughter (70 d old), to analyse mortality, morbidity, performance, intake behaviour, digestion and microbial activity. Seven days after starting feed restriction (35 d old, group R1), rabbits consumed 44% of the feed within 2 h, 65% in 4 h and in 7 h over 95%. Over the 28–70 d period, mortality was low (5.3%) while morbidity averaged 18.5% and neither was affected by treatment. However, FFD tended to decrease the morbidity rate during the first 14 days after weaning (P = 0.06). Feed conversion (28–70 d) was improved by restriction (+15%, P < 0.001) and by FFD (+5%, P < 0.001). Nutrient digestibility was improved by restriction (+10% for energy, P < 0.01), but not by FFD. Fragmented feed distribution led to a lower stomachal pH, in the antrum (1.48 vs 2.13, P < 0.001) and in the fundus (1.52 vs 2.63, P < 0.001), while a higher pH was found in the caecum (6.07 vs 5.86, P < 0.001). Butyrate proportion in the caecum was reduced by four units for restricted groups. Fragmented feed distribution reduced the caecal VFA concentration by 23% within restricted rabbit groups only. A similar interaction between intake level and FFD was observed for fibrolytic activity (cellulase and xylanase). The diversity of caecal bacterial community was not modified by either of the two factors studied. Globally, fragmented meals have no major impacts on the caecal microbial activity, diversity, and thus would not be implicated in the better resistance of restricted rabbit to digestive troubles.     

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

The aim of this work was to evaluate the ability of a line selected for reproductive longevity (LP) to confront productive challenges compared to a line selected during 31 generations for litter size at weaning (V). A total of 133 reproductive rabbit does were used (72 and 61 from LP and V lines, respectively). Within each line, three groups with different levels of productive effort were planned: PP9, inseminated at day 4 after the first partum and with nine kits during the second partum, and inseminated after first weaning (30 days) and with nine (PW9) or five kits (PW5) during the second partum. The reproductive performance, body condition (perirrenal fat thickness (PFT)) and lipolytic response were controlled. LP does showed greater mean live weight (LW; +128 g; P < 0.05), PFT (+0.47 mm; P < 0.05) and estimated body energy (EBE; +0.29 MJ/kg; P < 0.01) than V does at second partum. However, LP does that mated at first post partum did not significantly differ in EBE relative to V does at second partum. During the first week of lactation, dry matter (DM) intake was similar for both lines (94 and 95 g DM/kg LW0.75 day for V and LP does, respectively). There was a significant difference in milk yield between both lines during the first week when litter size was nine (60 v. 54 g of milk/kg LW0.75 day for LP and V does, respectively; P < 0.01), but no difference when litter size was five. Consequently, when litter size was nine, LP does showed a lower recovery of PFT (0.6 mm less; P < 0.05) than V does during the first 10 days of lactation. However, when litter size was five, LP does showed a higher LW (+210 g; P < 0.05) than V does at 10 days of lactation and a similar recovery of PFT. During the last 3 weeks of the lactation, LP does showed a higher feed intake (+6 g DM/kg LW0.75 day; P < 0.05) and milk yield (+27 g/day; P < 0.001) than V does when litter size was nine, resulting in no significant differences in LW at 30 days of lactation. However, when litter size was five, both lines showed similar feed intake and milk yield, maintaining their differences in LW at 30 days of lactation (+206 g for LP does; P < 0.05). These results show that the rabbit line selected for reproductive longevity is more robust with respect to coping with productive challenges, than a line selected for reproductive intensity.     

Improvements in the conception rate,milk composition and embryo quality of rabbit does after dietary enrichment with n-3 polyunsaturated fatty acids

This work attempts to confirm the effect of an enriched diet with n-3 polyunsaturated fatty acids (PUFA) trying to mitigate the reproductive performances issues such as low conception rate of primiparous rabbits. A total of 127 does were fed ad libitum throughout their two first cycles with two diets with different fat sources: mixed fat in the control and salmon oil in the enriched one, with 3.19 g/100 g (n=63 does) and 28.77 g/100 g (n=64 does) of n-3 of the total fatty acid, respectively. Feed intake was similar between groups (P>0.05). Plasma progesterone concentration was higher in the enriched females than in control ones at 7 (30.9±2.18 v. 23.9±2.30 ng/ml, respectively; P=0.029) and 14 (38.7±2.18 v. 28.2±2.30 ng/ml, respectively; P=0.001) days of first gestation. Considering both cycles, reproductive parameters of mothers (fertility, duration of gestation and prolificacy) and litter parameters (weight at parturition and weaning, mortality and average daily gain (ADG) of kits during lactation) were similar in both groups. However, individual measurements of neonates of enriched group improved 5.87%, 7.10% and 18.01% (P<0.05) in terms of crown-rump length, biparietal and thoracic diameters, respectively, compared to control ones at first parturition. It is noteworthy that at the second insemination, critical point in rabbit, fertility rate of enriched group did not decline as sharply as in the control group (89.7% v. 76.6%, respectively; P=0.067), although ADG and littler weight were slightly lower at the second lactation after PUFA enrichment (P<0.05). Total PUFA and unsaturated index of milk of enriched does group were significantly elevated than in control one (33.3±0.02 v. 23.2±0.02 g/100 g and 1.20±0.00 v. 0.86±0.00, respectively; P<0.05). Finally, plasma progesterone, ovulation rate, fertility and embryo development at 3.5 days after the artificial insemination were similar between diets (P>0.05), but embryo apoptosis rate was higher in control group than in enriched one (31.1±4.56% v. 17.1±3.87%, respectively; P<0.05). In conclusion, dietary PUFA enrichment from the rearing and throughout two productive cycles improved plasma progesterone during pregnancy, fertility, milk fatty acid profile and neonates development of primiparous supporting the beneficial effect of n-3 PUFA supplementation in rabbit does.     

Environmental sensitivity differs between rabbit lines selected for reproductive intensity and longevity

To better understand the mechanisms that allow some animals to sustain their productive effort in harsh environmental conditions, rabbit does from two selection lines (LP and V) were housed in normal (NC), nutritional (NF) or heat (HC) challenging environmental conditions from first to third partum. The LP line (n=85) was founded on reproductive longevity criteria by selecting does from commercial farms that had a minimum of 25 partum with more than 7.5 kits born alive per parity. Line V (n=79) was constituted from four specialised maternal lines into a composite synthetic line and then selected by litter size at weaning for 36 generations. Female rabbits in NC and NF environments were housed at normal room temperature (18°C to 24°C) and fed with control [11.6 MJ digestible energy (DE)/kg dry matter (DM)] or low-energy diets (9.1 MJ DE/kg DM). HC does were housed at high room temperatures (25°C to 35°C) and fed the control diet. Female rabbits in the HC and NF environments ingested 11.5% and 6% less DE than NC does, respectively (P<0.05). These differences between environments occurred in both lines, with the differences being higher for LP than for V does (+6%; P<0.05). Milk yield responses followed those of energy intake also being higher for LP does (+21.3 g/day; P<0.05). The environmental conditions did not affect the perirenal fat thickness (PFT), but a genotype by environment interaction was observed. In NC and HC, the PFT was higher for line V (+0.23 and +0.35 mm, respectively; P<0.05) than for LP does, but this was not the case at NF (−0.01 mm). Moreover, the PFT evolution was different between them. In the NC environment, LP does used the accreted PFT in late lactation (−0.29 mm), whereas V does did not (−0.08 mm). Conversely, in the HC environment, LP does showed a flat PFT evolution in late lactation, whereas V does accumulated PFT. In the NF environment, LP and V does had a similar PFT evolution. There was also a litter size reduction for V does of −2.59 kits total born in HC and −1.78 kits total born in NF environments, whereas this was not observed for LP does. The results for LP does indicate a direct use of DE ingested for reproduction with little PFT change, whereas V does actively use the PFT reserves for reproduction.     

Effect of an Escherichia coli F4/F18 bivalent oral live vaccine on gut health and performance of healthy weaned pigs

Oral live vaccines stimulate host immunity, but they could also affect intestinal mucosa development and gut microbiota of piglets during the postweaning. The aim of this study was to determine the effect of an oral vaccine against Escherichia coli F4 and F18 (Coliprotec F4/F18®), on gut functionality and integrity, growth performance and health status of postweaning piglets. A total of 96 weaned piglets (23.30 ± 1.85 days of age; 7334 ± 1039 g BW) were divided into two groups (16 replicates/group; three piglets/replicate) as follows: (1) Control (CO), fed a standard diet (prestarter up to 14 days, then starter feed); (2) Treated (TRT): as CO but vaccinated with Coliprotec F4/F18® at weaning (day 0). Piglets were weighed at day 0 and weekly until day 35. Individual faecal score was recorded daily. Piglets were sacrificed at days 10 (1/3 of total) and 35 (2/3). Samples of jejunum mucosa and of cecum content were collected for morphometric, immunohistochemistry analysis and for microbiota profile analysis, respectively. Data were fitted using a linear model including treatment, class of starting BW as fixed factors and litter as random factor. From days 0 to 7, piglets from the TRT group tended to have a higher average daily gain (+22.6%, P = 0.08) and average daily feed intake compared to the CO group (+13.2%, P = 0.022). Gain to feed ratio was lower in the TRT group from days 14 to 35 (?6.6%, P = 0.011). From days 7 to 14, the TRT group had a higher diarrhoea index (?199%, P < 0.001). Crypt depth was higher in the CO group (+10.9%, P = 0.04) at day 10, but not at day 35. Jejunal expression of Claudin-4 (probability of having a score = 3) was higher in the TRT group at day 10 (CO = 1.50% vs TRT = 2.69%, P < 0.0001) and day 35 (CO = 1.29% vs TRT = 1.92%, P = 0.012). Oral vaccine affected beta diversity at day 10 (P = 0.040; R² = 0.05) and increased the abundance of specific taxa and genera in the cecum at day 10, including Prevotella (lg2FC = 23.2, FDR < 0.001). The results showed how an Escherichia coli-based vaccine supplied to weaned pigs can promote gut health by controlling symptoms of the postweaning perturbation in the first 2 weeks postweaning. In addition, the vaccine strains showed a probiotic-like effect by modulating gut microbiota favouring the establishment of beneficial bacteria, and by promoting gut barrier integrity.     

Effects of feed restriction during pregnancy on maternal reproductive outcome,foetal hepatic IGF gene expression and offspring performance in the rabbit

Primiparous female rabbits have high nutritional requirements and, while it is recommended that they are subjected to an extensive reproductive rhythm, this could lead to overweight, affecting reproductive outcomes. We hypothesised that restricting food intake during the less energetic period of gestation could improve reproductive outcome without impairing offspring viability. This study compares two groups of primiparous rabbit does in an extensive reproductive programme, one in which feed was restricted from Day 0 to Day 21 of gestation (R021), and another in which does were fed ad libitum (control) throughout pregnancy. The mother and offspring variables compared were (1) mother reproductive outcomes at the time points pre-implantation (Day 3 postartificial insemination [AI]), preterm (Day 28 post-AI) and birth; and (2) the prenatal offspring characteristic IGF system gene expression in foetal liver, liver fibrosis and foetus sex ratio, and postnatal factor viability and growth at birth, and survival and growth until weaning. Feed restriction did not affect the conception rate, embryo survival, or the number of morulae and blastocysts recovered at Day 3 post-AI. Preterm placenta size and efficiency were similar in the two groups. However, both implantation rate (P < 0.001) and the number of foetuses (P = 0.05) were higher in the R021 mothers than controls, while there was no difference in foetal viability. Foetal size and weight, the weights of most organs, organ weight/BW ratios and sex ratio were unaffected by feed restriction; these variables were only affected by uterine position (P < 0.05). Conversely, in the R021 does, foetal liver IGBP1 and IGF2 gene expression were dysregulated despite no liver fibrosis and a normal liver structure. No effects of restricted feed intake were produced on maternal fertility, prolificacy, or offspring birth weight, but control females weaned more kits. Litter weight and mortality rate during the lactation period were also unaffected. In conclusion, pre-implantation events and foetal development were unaffected by feed restriction. While some genes of the foetal hepatic IGF system were dysregulated during pregnancy, liver morphology appeared normal, and the growth of foetuses and kits until weaning was unmodified. This strategy of feed restriction in extensive reproductive rhythms seems to have no significant adverse effects on dam reproductive outcome or offspring growth and viability until weaning.     

Effect of feeding program during rearing and age at first insemination on performances during subsequent reproduction in young rabbit does

An experiment was performed to study the effect of the feeding program and age at first mating on body growth, feed intake, reproductive performance, and culling of rabbit does over three parities, using 155 does of a strain of New Zealand white rabbits. Three treatments were applied. Ad libitum feeding until first insemination at 14.5 wk (AL-14.5) or 17.5 wk of age (AL-17.5), and restrictive feeding from five wk of age until first insemination at 17.5 wk of age (R-17.5). At first insemination, the BW of AL-14.5 and R-17.5 was similar (3 907 vs. 3 791 +/- 46 g, respectively), whereas AL-17.5 does were heavier (4 390 +/- 46 g, P < 0.001). During reproduction, performance of AL-17.5 was not improved compared to AL-14.5 and R-17.5 does. Al-17.5 does showed a lower feed intake during the first gestation (-25%) and first parity (-10%) than R- 17.5, resulting in weight loss (-6%) during the first gestation and decreased litter weights (-19%) and litter growth (-14%) in the first parity. Extended first mating by three wk (17.5 vs. 14.5 wk) but similar BW at first mating did not affect feed intake and BW development during the first three parities. However, the number of live born kits and weight at first kindling, and litter growth in the first parity were improved in R-17.5 (+23%, +18%, and +14%, respectively). Reproductive performance can be improved by restricted feeding during rearing and extended first insemination to 17.5 wk of age. However, the culling rate was not affected by the rearing strategy.     

Long term effect of post-weaning rhythm on the body fat and performance of rabbit doe

Reproductive protocols based on standard (Control: 11 days post-partum) or extended rhythm (PW: post-weaning at 27 days post-partum) were compared. Two groups of fifty 19-week-old New Zealand White females were inseminated for seven consecutive cycles. The kits were weaned at 26 days. On the day of AI, all the does were submitted to ultrasound scanning of the perirenal regions to measure fat thickness. The fertility rate and several indexes of efficiency were calculated. Fat thickness, estimated perirenal fat and live weight were higher in PW does. The does submitted to post-weaning rhythm had a higher sexual receptivity (P < 0.01), and fertility rate (P < 0.01) whereas litter size and pre-weaning mortality were not affected. Primiparous Control does showed a particularly low fertility rate; the value increased successively but was always lower than in PW does. PW rhythm in comparison with the standard one seemed more adapted to doe reproductive physiology even if there was a lower production (35.0 vs. 38.8 rabbit sold/year) and risk of fatness (18% of multiparous does).     

Effects of feeding programme on the performance and energy balance of nulliparous rabbit does

A total of 190 rabbit females were used to evaluate five feeding programmes from 9 weeks of age to the first parturition: CAL, fed ad libitum with a control diet (C: 11.0 MJ digestible energy (DE) and 114 g digestible protein (DP)/kg dry matter (DM)) until first parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until first parturition; F, fed ad libitum with a low-energy, high-fibre diet (F: 8.7 MJ DE and 88 g DP/kg DM) until first parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until first parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until first parturition. The rabbits were artificially inseminated at 18 weeks of age. CAL group had a higher mortality rate compared with the other groups between 9 and 12 weeks of age (34% v. 3%; P < 0.05) and during the last 3 weeks of first pregnancy (14% v. 3%; P < 0.05). The CAL and FC females presented higher BW and perirenal fat thickness (PFT) than CR females at 11 days of pregnancy (+0.41 kg and +0.6 mm; P < 0.05), with F females showing medium values. The type of feeding procedure did not affect the fertility rate of young females at first artificial insemination. Differences in BW disappeared at parturition, when only CAL females presented a greater PFT than CR and FC females (+0.3 mm; P < 0.05). In comparison with FCF, CAL females had smaller and thinner live born litters (−2.5 kits and −139 g, respectively; P < 0.05), with CR, F and FC females showing medium values. The low number of kits born alive for CAL females was because of their lesser total number of kits born (−1.7 kits; P < 0.05) and the greater mortality of their litters at birth (+13.9%; P < 0.05) compared with FCF females. Non-esterified fatty acid was higher in the blood of females fed C diet (CAL and CR) than in others at partum day (on average +0.15 mmol/l; P < 0.05). In conclusion, the ad libitum use of diets for lactating rabbit does throughout the rearing period could lead young rabbit females to present a higher risk of early death and smaller litter size at first parturition. Feed restriction or earlier use of suitably fibrous diets led females to achieve the critical BW and fat mass at first mating to ensure reproduction.     

The effect of 1-week feed restriction on performance,digestibility of nutrients and digestive system development in the growing rabbit

A 3 to 4 week feed restriction of about 20% to 25% of the free intake is widely applied in rabbit breeding systems to reduce post-weaning digestive disorders. However, a short intensive feed restriction is described in few studies and can be beneficial for growing rabbits due to a longer re-alimentation period. The aim of this study was to evaluate the effect of ad libitum (AL) and two restriction levels of feeding (50 and 65 g/rabbit per day) applied for 1 week on performance, gastrointestinal morphology and physiological parameters during the restriction and during the re-alimentation period. Rabbits were divided into three experimental groups: AL rabbits were fed AL, R1 rabbits were restricted from 42 to 49 days of age and received 50 g daily (29% of AL) and R2 rabbits were restricted at the same age and were fed 65 g of feed daily (37% of AL). In the 1^st week after weaning and in the weeks after restriction, all the groups were fed AL. During the restriction period, daily weight gain (DWG) in R1 significantly dropped to 11% (experiment 1) and 5% (experiment 2) compared with rabbits in the AL group, although they were fed 29% of AL, whereas in the R2 group it decreased to 20% (experiment 1) and 10% (experiment 2). In the week following feed restriction, DWG in the restricted groups increased (P<0.001) to 166% and 148% in R1 and to 128% and 145% in R2. Restricted rabbits in both the experiments reached up to 90% to 93% of the final live weight (70 days) of the AL group. Over the entire experimental period, feed restriction significantly decreased feed intake to 85% to 88% of the AL group; however, the feed conversion ratio was lower (P<0.05) only in experiment 1 (−6% in R1 and −4% in R2). Digestibilities of CP and fat were not significantly higher during the restriction period and during the 1^st week of re-alimentation compared with the AL group. Significant interactions between feeding regime and age revealed the shortest large intestine in the AL group at 49 days of age and the longest at 70 days in the AL and R1 groups. Small intestinal villi were significantly higher and the crypts were significantly deeper in the restricted groups. It could be concluded that short intensive feed restriction increased digestible area in the small and large intestines, including the height of villi and depth of crypts, which might be involved in the compensatory growth and defence mechanism.     

Part-time grouping of rabbit does in enriched housing: effects on performances,injury occurrence and enrichment use

Collective housing is perceived as a possible way to improve rabbit welfare, especially among adult females, which are normally individually housed. Part-time group housing seems to allow a better balance between welfare and health than continuous group housing, but practical implementation and consequences for reproductive performance have not been extensively studied. The aim of this work was to compare weight, feed intake, litter size, injury occurrence, body integrity, and spatial location of female rabbits housed part-time in group housing (PGH group, n = 32) or housed individually (IH group, n = 8). Females were grouped by opening connecting hatches between four individual enriched cages (platform, wood stick and gnawing block). Collective housing started 12 days after artificial insemination and was interrupted at the 10th day (instead of the 15th day later as originally planned) due to high injury rates and severe injuries caused by fighting. The proportion of injured females increased from 25% on the first day of grouping to 63% on the 10th day. Female weight gain during the experiment was similar in the two groups. Litter size at weaning was 9% lower in the PGH group than in the IH group (9.2 vs 10.0, P < 0.01). Platform use was recorded in 32% of the observations and was the highest during the 2 weeks before weaning (46% and 47% of total observations, P < 0.05). During the grouping period, there were at least two females in the same housing unit in 59.4% of the cases, at least two females were located on the same level in 31.3% of the cases. In conclusion, connecting individual cages is an ergonomic solution for part-time group housing, but does not prevent fights for the establishment of a social hierarchy. This is detrimental to the health and body integrity of female rabbits.