YAC transgenesis in farm animals: Rescue of albinism in rabbits

The generation of transgenic mice with mammalian genes cloned in yeast artificial chromosomes (YACs) has generated great interest in the field of gene transfer into livestock. Many of the problems associated with standard transgenesis—such as lack of crucial regulator elements and position effects related to the integration site, which lead to variation in expression levels irrespective of the dose of the transgene—have been practically overcome. The large size of YAC-derived gene constructs (in excess of 1 Mb) facilitates the presence and transfer of all elements required for the faithful regulation of a gene. With the experiments discussed in this report, we have addressed the possibility of applying the obvious advantages of YAC transgenesis to farm animals. We have generated transgenic rabbits carrying a 250 kb YAC covering the mouse tyrosinase gene by pronuclear microinjection, and thus rescued the albino phenotype of the transgenic individuals. To date, this is the first demonstration of a successful transfer of large genetic units into the germ line of farm animals. This development might improve the occurrence of transgene expression at physiological levels and specific sites in livestock. YAC transgenesis therefore will be applied in genetic engineering, for example, in the production of pharmacologically interesting proteins encoded by large gene units and generating transgenic donors for xenotransplantation. © 1996 Wiley-Liss, Inc.     

Biodiversity and fermentative activity of caecal microbial communities in wild and farm rabbits from Spain

In order to study the microbial caecal ecosystem of wild and domestic rabbits through the fermentation characteristics and concentration and diversity of bacterial and archaeal communities, caecal samples from sixteen wild rabbits (WR) were contrasted with two groups (n = 4) of farm rabbits receiving low (LSF) or high (HSF) soluble fibre diets from 28 (weaning) to 51 days of age. DNA was extracted for quantifying bacteria and Archaea by qPCR and for biodiversity analysis of microbial communities by DGGE. Samples from WR had lower caecal pH and ammonia and higher volatile fatty acids concentration than farm animals. Lower acetate and higher butyrate proportions were detected in WR. Bacterial and archaeal DGGE profiles were clearly different between wild and farm rabbits, and diet-affected population of farm rabbits. Similarity index of bacteria was lower than 0.40 among WR, and 0.52 among farm rabbits. In conclusion, caecal fermentation characteristics differ between wild and farm rabbits, which harbour clearly different bacterial and archaeal communities. In farm rabbits, diversity is influenced by the dietary level of soluble fibre.     

Maternal care of rabbits in the lab and on the farm: endocrine regulation of behavior and productivity

Maternal behavior in rabbits has been well described in the wild, the laboratory, and the farm. Salient characteristics include: (a) the construction of a nest (inside an underground burrow or a box), composed of straw/grass and body hair and (b) the display of a single, brief (ca. 3 min) nursing bout per day. The onset and decline of nest-building in mid and late pregnancy are controlled by specific combinations of estradiol, progesterone, testosterone, and prolactin. Following parturition (kindling) does can mate and become pregnant again. Management strategies have been used on the farm to enhance productivity, impinging on specific reproductive processes (e.g., use of hormones to synchronize estrus, artificial insemination at kindling, doe-litter separation on specific days of lactation to increase sexual receptivity and fertility). Knowledge about the rabbit's reproductive physiology and behavior will be enriched by integrating research coming from the laboratory (where estrus, pregnant-only, or lactating-only animals are the main categories investigated) with studies performed on the farm or research station (where pregnant-lactating rabbits are prevalent). Similarly, the high productivity demands of modern rabbit farms will benefit from the information obtained in the laboratory where specific issues in reproductive neuroendocrinology are explored with methodologies that are not amenable for farm use.     

MicroRNAs in farm animals

MicroRNAs (miRNAs) are a class of ∼22 nucleotide-long small noncoding RNAs that target mRNAs for translational repression or degradation. miRNAs target mRNAs by base-pairing with the 3′-untranslated regions (3′-UTRs) of mRNAs. miRNAs are present in various species, from animals to plants. In this review, we summarize the identification, expression, and function of miRNAs in four important farm animal species: cattle, chicken, pig and sheep. In each of these species, hundreds of miRNAs have been identified through homology search, small RNA cloning and next generation sequencing. Real-time RT-PCR and microarray experiments reveal that many miRNAs are expressed in a tissue-specific or spatiotemporal-specific manner in farm animals. Limited functional studies suggest that miRNAs have important roles in muscle development and hypertrophy, adipose tissue growth, oocyte maturation and early embryonic development in farm animals. Increasing evidence suggests that single-nucleotide polymorphisms in miRNA target sites or miRNA gene promoters may contribute to variation in production or health traits in farm animals.     

Genetic diversity in major farm crops on the farm and in reserve

Genetic vulnerability does not at this time present a major threat to production of United States field crops, according to a 1981 survey of U.S. crop breeding directors. But plant breeders do regard genetic vulnerability as an important and potentially dangerous problem. The 1981 survey indicated that although the genetic base of U.S. field crop production is not as narrow as in 1970, it still is concentrated on a relatively small number of favored cultivars. Genetic diversity is provided, nevertheless, in other and less obvious ways. Survey responses indicated that the genetic base of the elite germplasm pool is wider and provides more useful diversity than is usually supposed. However, breeders also value the national germplasm repositories as indispensable sources of needed diversity.     

Exomphalos in four consecutive pregnancies

Summary Four consecutively born siblings were affected by Exomphalos. In 2 cases, major and minor anomalies were associated. Cytogenetic examination of the fourth infant revealed a normal karyogram. The parents and their families did not exhibit any relevant genetic defect. On the other hand it is unlikely that such a series of exomphalos was due to chance.The increased liability to exomphalos might be conditioned by a polygenic multifactorial system and induced by environmental influences of an unknown nature. Recessive inheritance is not excluded.     

Giardia infection in farm animals

Giardia infection is prevalent in farm animals from an early age. Despite the wide occurrence of the infection and recent understanding of its epidemiology, many aspects of giardiasis of farm animals remain unclear. In this article, Lihua Xiao discusses the prevalence, patterns, sources and clinical importance of Giardia infection in a variety of farm animals.