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 pH(24), 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 (P0.05). 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.

Generation of heavy-chain-only antibodies in mice.

We have generated transgenic mice containing hybrid llama/human antibody loci that contain two llama variable regions and the human D, J, and Cmu and/or Cgamma constant regions. Such loci rearrange productively and rescue B cell development efficiently without LC rearrangement. Heavy-chain-only antibodies (HCAb) are expressed at high levels, provided that the CH1 domain is deleted from the constant regions. HCAb production does not require an IgM stage for effective pre-B cell signaling. Antigen-specific heavy-chain-only IgM or IgGs are produced upon immunization. The IgG is dimeric, whereas IgM is multimeric. The chimeric HCAb loci are subject to allelic exclusion, but several copies of the transgenic locus can be rearranged and expressed successfully on the same allele in the same cell. Such cells are not subject to negative selection. The mice produce a full antibody repertoire and provide a previously undescribed avenue to produce specific human HCAb in the future.