World Rabbit Science - Vol. 15 (3)-2007

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Alternatives to antibiotic growth promoters in rabbit feeding: a review.
Effect of dietary sodium on digestibility of nutrients and performance in growing rabbits.
Association between litter size and the k-casein genotype in the INRA rabbit lines.
Some factors affecting production and milk composition characters in a crossbreeding experiment involving Gabali and V- line rabbits in Egypt.
Effective generation of genetically modified rabbits by sperm mediated gene transfer.
New Zealand White rabbits show non-selective nursing in various types of nests.

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Some factors affecting production and milk composition characters in a crossbreeding experiment involving Gabali and V- line rabbits in Egypt
(World Rabbit Science. ICTA. UPV, 2007) Iraqi, M.M.; Shenana, M.E.; Baselga, M.; Agencia Española de Cooperación Internacional para el Desarrollo; Universitat Politècnica de València
[EN] Data from 662 litters and 221 samples (two replicates per each sample) of rabbit milk were collectedfrom three different genetic groups [Gabali (G), V-line (V) and GxV (F1)] to study the effect of line and of somenon-genetic factors affecting production and milk composition traits. The studied traits were: number bornalive (LSBA); litter size at weaning (LSW); litter weight born alive (LWBA); litter weight at weaning (LWW); totalmilk yield (TMY) and protein, fat, total solids (TS), ash, phosphorus (P), potassium (K), sodium (Na), calcium(Ca) and magnesium (Mg) milk content. The genetic group effect was significant for LSBA [V (7.3) and F1(7.3)were superior to G (6.6)); LWBA (higher values for V (416 g) and F1 (405 g) than for G (382 g)]; TMY [G (3497g) and F1(3486 g) higher than V (3042 g)]; milk fat [F1 (26%) and G (25%) superior to V (23%)] and milkTS[F1(42%) superior to G (40%) and V (39%)]. The estimates of the heterosis effect ranged between 1.6% and12.8% for production and milk gross chemical traits, being significant only for milk fat content (9.1%). Thepositive values of the heterosis estimates for those traits and the complementarity between the G breed andthe V line, the G superior in milk related traits but the V superior in prolificacy, show the interest of their crossand of the synthetic lines derived from them. The heterosis was non-significant for milk mineral content traits.The parity effects were significant for LSBA, fat, TS, ash and K (the maxima were reached at 6th or 5th parity).The effect of week of lactation was significant for fat, ash and TS, corresponding the maximum values of fatand TS to the 3rd and 4th week. The year-season or the year-month effects were significant for all traitsshowing the importance of including these time-period factors into the statistical models proposed for thetraits.
New Zealand White rabbits show non-selective nursing in various types of nests
(World Rabbit Science. ICTA. UPV, 2007) González-Mariscal, G; Gallegos, J.A.
[EN] We investigated the capacity of New Zealand White female rabbits to nurse their litter in a nestdifferent from their own (i.e., from another female, in a box containing synthetic or male hair, or in a new boxcontaining part of the original nest material). In females that nursed in their own nest across lactation days 1-3 (one nest-condition) the mere addition of any of the above boxes (without pups) across days 4, 5, 6, 7, or8 provoked an increase in the latency to enter their own nest for nursing (0.05±0 vs. 2±1 min; P<0.01; Group1A). In the two-nest condition females took a longer time to enter any box for nursing than they did to enter theirown. These differences were significant only for the synthetic nest (4±1.5 min; P<0.05). When the two-nestcondition began on lactation day 1 (Group 1B) the latency to enter significantly increased only with the malenest (8±4 vs. 1±0 min, own nest; P<0.05). The time inside the nest box devoted to nursing was practically thesame under all conditions and within the normal duration (ca. 3 min). Milk production rose steadily across thedays of observation, regardless of the type of nest-box the litter was placed in. We also explored the effectof using alien kits, rather than the female's own, on the rabbit's capacity to nurse them in any of the above nesttypes (Group 2). The only differences between Group 2 and Group 1B were: a) on day 1 females nursing analien litter produced less milk (48±5 g) than the two groups nursing their own (69±5, 75±8 g; P<0.02); b) thelatency to enter the male nest was smaller in Group 2 (2±2 vs. 8±4 min; P<0.05). These results show that,although able to distinguish among different nest types, rabbits can nurse their own or alien kits in severalenvironments. These findings can be useful in small farm rabbit husbandry practices for facing the problemsof kit death or nest deterioration in early lactation.
Effective generation of genetically modified rabbits by sperm mediated gene transfer
(World Rabbit Science. ICTA. UPV, 2007) Vasicek, D.; Vasickova, K.; Parkanyi, V.; Rafay, J.; Ondruska, L.; Slovak Research and Development Agency
[EN] Many reports in the past decade showing successful sperm mediated gene transfer (SMGT) offoreign DNA into both non-mammalian and mammalian animals. Fresh collected, extender washed rabbit spermcells were co-cultured with linear 14.3 kb gene construct and used for AI. Transgene integration in rabbitgenome was verified by PCR analysis. The PCR results show that transgenic founder rabbits transmittedtransgene to F1 generation. Our preliminary results suggest that SMGT could be an effective method forproduction of genetically modified rabbits.
Effect of dietary sodium on digestibility of nutrients and performance in growing rabbits
(World Rabbit Science. ICTA. UPV, 2007) Chamorro, S.; Gómez-Conde, M.S.; Centeno, C.; Carabaño, R.; De Blas, J.C.; Ministerio de Ciencia y Tecnología
[EN] The effects of a reduction in the sodium content from 2.6 to 1.6 g/kg DM in diets with similarelectrolyte balance on fattening performances and ileal apparent digestibility of nutrients were investigated inearly weaned rabbits. Two diets containing 17.9% DM of crude protein, with the same composition and onlydiffering in sodium chloride content (0.5 and 0.2%) were given to rabbits weaned at 25 days to measurefattening performance (46 rabbits per diet), and apparent ileal digestibility (AID, 14 rabbits per diet) of DM,crude protein (CP) and amino acids (AA). Neither AID of DM nor AID of CP, which amounted 47.4 and 60.9% asaverage respectively, were affected by the dietary sodium content. The effect of a decrease in dietary sodiumconcentration on the AID differed among amino acids, as a reduction was observed for cystine (by 11%;P<0.01), methionine, arginine, tyrosine and phenylalanine (by 4.9, 5.6, 7.4 and 10.3%; respectively P<0.05),glutamic acid, leucine and isoleucine (by 4.1, 6.1 and 7.1%, respectively P<0.1), whereas no differences(P>0.10) were detected for the other amino acids. A reduction of dietary sodium content did not affect dailyweight gain, feed intake and feed efficiency (46.7 g/d, 76.7 g/d and 0.609 as average, respectively) neitherduring the first two weeks after weaning when the experimental diets were used, nor when the wholefattening period was regarded. The results of this experiment indicate that is possible to reduce the currentdietary sodium recommendations for fattening rabbits to 1.6 g/kg DM during the first two weeks after weaning,without impairing either the fattening performances or the ileal digestibility of DM and CP. In addition, this studyindicate that the level of sodium in the diet affects the gut absorption of methionine and cystine and severalnon-essential AA.
Association between litter size and the k-casein genotype in the INRA rabbit lines
(World Rabbit Science. ICTA. UPV, 2007) Bolet, G.; Devinoy, E.; Viràg, G.; Harsányi, I.; Bosze, Zs.; Hungarian Scientific Research Fund
[EN] The reproductive traits of 276 rabbit does belonging to an intercross generation of two synthetic INRAlines, which differed by their genotypes at the k-casein locus being either AA or AB, were recorded at birth andat weaning for a total of 743 litters. They were the daughters of 77 dams whose k-casein genotype was ABand 18 sires whose genotype was AA. A significant association between the k-casein genotype andreproductive traits at birth was found in favour of the AB females, with an increase in litter size (+0.56;P<0.009) as well as in litter weight (+27 g; P<0.023). After standardisation of the litter size at birth, thegenotype of the dam was found to have no effect on weight gain and the viability of the young between birthand weaning or on the litter weight at weaning. Work is now in progress to explain this association.

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