Cloning cattle

Over the past six years, hundreds of apparently normal calves have been cloned worldwide from bovine somatic donor cells. However, these surviving animals represent less than 5% of all cloned embryos transferred into recipient cows. Most of the remaining 95% die at various stages of development from a predictable pattern of placental and fetal abnormalities, collectively referred to as the "cloning-syndrome." The low efficiency seriously limits commercial applicability and ethical acceptance of somatic cloning and enforces the development of improved cloning methods. In this paper, we describe our current standard operating procedure (SOP) for cattle cloning using zona-free nuclear transfer. Following this SOP, the output of viable and healthy calves at weaning is about 9% of embryos transferred. Better standardization of cloning protocols across and within research groups is needed to separate technical from biological factors underlying low cloning efficiency.     

Serum antigens of cattle

We have produced an alloimmune serum that detects a new cattle immunoglobulin light chain allotype. Genetic analysis involving more than 600 offspring showed that this allotype is controlled by an autosomal codominant allele [Ig(L)b ²], of theIg(L)b ¹ gene previously reported from this laboratory. This system also contains a recessive allele for which no product can now be detected. The frequencies of the three alleles in 5 dairy breeds are reported. The Ig(L)B1 and Ig(L)B2 allotypes are expressed as complexes of 2 or 3 precipitin bands in double diffusion gels containing polyethylene glycol-6000. The complexes are transmitted as genetic units.     

Superovulatory responses of cattle

Non-histological examination of superovulated ovaries of cows does not allow one to distinguish between corpora lutea and luteinized follicles. A better estimation of ovulation rate could, therefore, be made from the number of embryos recovered or from the levels of E₂-17β in the plasma 60 hours after PMSG.For comparison of different treatments, it is necessary to characterize activities of the stimulatory agents used. Administration of an FSH - LH preparation twice a day at decreasing doses gives the best mean responses, but no treatment has been found which can clearly decrease the large variation between individuals in their responses.Numerical, kinetic and endocrine ovarian factors can partly explain the variability of ovarian responses to PMSG in the heifer. Individual differences in follicular populations at the time of treatment, or in E₂-17β levels after stimulation, could be related to differences in responses in ovulation rate. Normal follicles >1.7 mm diameter before treatment would usually ovulate following PMSG injection, whereas early atretic follicles of the same size mostly luteinize.     

Significance of Neospora caninum in British dairy cattle determined by estimation of seroprevalence in normally calving cattle and aborting cattle

A case control study was conducted to evaluate the significance of Neospora caninum infections in cattle in England and Wales. The prevalence of N. caninum in normally calving cattle (the control group; n = 418) and aborting cattle (n = 633) was estimated using a commercial antibody-detection ELISA. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and Leptospira hardjo were also obtained by serology. The prevalence of N. caninum was significantly higher (P < 0.0001) in the aborting group (18%; 95% confidence interval: 15%, 21%) than in the control group (6%; 95% confidence interval: 4%, 8%); the latter is the first estimate, to date, of the national seroprevalence of N. caninum in dairy cattle in England and Wales. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and L. hardjo were not found to be higher in the aborting cattle than in the control group. With N. caninum, a strong association between seropositivity and abortion was found, with seropositive cows being 3.5-times more likely to abort than seronegative cows (odds ratio = 3.49; 95% confidence interval: 2.16, 5.69). Furthermore, 12.5% of abortions in dairy cattle in England and Wales may be attributable to N. caninum, as indicated by estimation of the population aetiological fraction.     

Seasonality in cattle

Although cattle are basically not seasonal breeders, several physiological changes occur in response to two major climatic variables of season: ambient temperature and photoperiod. Ambient temperatures above 27°C lengthen the estrous cycle, decrease duration and intensity of estrus, decrease fertility and increase embryonic mortality. Some of these effects may be mediated via decreased secretion of luteinizing hormone and increased secretion of progesterone. Heat stress also suppresses growth rate, milk production and feed intake. In comparison with cattle exposed to less than 12 h of light per day, 14 to 16 h of light has relatively little effect on secretion of gonadotropins and fertility; however, growth rates, feed intake and milk yield are stimulated. Of all hormones measured in cattle, prolactin is the most responsive to changes in seasons, ambient temperature and photoperiod. Prolactin is greatest in summer when ambient temperatures are highest and photoperiods are longest.     

Paternal origins of Chinese cattle

To determine the genetic diversity and paternal origin of Chinese cattle, 302 males from 16 Chinese native cattle breeds as well as 30 Holstein males and four Burma males as controls were analysed using four Y‐SNPs and two Y‐STRs. In Chinese bulls, the taurine Y1 and Y2 haplogroups and indicine Y3 haplogroup were detected in seven, 172 and 123 individuals respectively, and these frequencies varied among the Chinese cattle breeds examined. Y2 dominates in northern China (91.4%), and Y3 dominates in southern China (90.8%). Central China is an admixture zone, although Y2 predominates overall (72.0%). The geographical distributions of the Y2 and Y3 haplogroup frequencies revealed a pattern of male indicine introgression from south to north China. The three Y haplogroups were further classified into one Y1 haplotype, five Y2 haplotypes and one Y3 haplotype in Chinese native bulls. Due to the interplay between taurine and indicine types, Chinese cattle represent an extensive reservoir of genetic diversity. The Y haplotype distribution of Chinese cattle exhibited a clear geographical structure, which is consistent with mtDNA, historical and geographical information.     

Absorption spectrum of cattle hypsorhodopsin

On irradiation at liquid helium temperatures, rhodopsin is converted into hypsorhodopsin which decays to bathorhodopsin above 23 K. The absorption spectrum of cattle hypsorhodopsin (λ_max = 435 nm) is found to include a new sideband around 540 nm. This sideband may be due to π^* ← π transition to ¹A^?_g like state, which is made partially allowed by distortion of polyene chain of the retinylidene chromophore.     

Compass of 47,787 cattle ESTs

Comparative Mapping by Annotation and Sequence Similarity (COMPASS) has been demonstrated to be an effective approach for predicting the chromosome location of expressed sequence tags (ESTs) and other sequence-based markers on the basis of comparative mapping information. Herein, we describe the development and use of a computer program to execute the COMPASS strategy en masse. The program was used to identify orthologs and predict map locations of 47,787 cattle ESTs. Among these 47,787 ESTs, 30,097 had significant matches with sequences in the human UniGene database and 21,311 were annotated with human GB4 radiation hybrid mapping data. These sequences are contained within 9,956 and 6,295 individual human UniGene clusters, respectively. The putative human orthologs and predicted cattle chromosome locations of the 21,311 cattle ESTs with GB4 mapping data are provided in this report as a resource for the research community.     

Breed structure of Senepol cattle

Data were collected by the Virgin Islands Beef Cattle Improvement Program and the Virgin Islands Agricultural Experiment Station staff to establish the breed structure of the Senepol cattle. Data for the analysis were limited to the two Virgin Islands Senepol breeders with the most complete and largest set of records, representing approximately 65% of the entire Senepol population. Inbreeding (F) and coancestry relationship coefficients (rAB) and the theoretical inbreeding (FT) were determined from each data set and for the combined data from both farms, for each year, ranging from 1947 to 1984 for Annaly Farms, and from 1967 to 1984 for Castle Nugent Farm. The data sets for both farms were examined for the possibility of separation into families. Actual F within the Senepol population was relatively low, averaging less than 1.00%. Some separation into families occurred within Annaly Farms' cattle. The F and FT decreased (1.6 to 0.7% and 1.0 to 0.2%, respectively) as population numbers increased. The low F was accomplished through the breeding programs and exchanges of animals between farms on the island.     

Agro-economic impact of cattle cloning

The purpose of this paper is to review the economic and social implications of cloned cattle, their products, and their offspring as related to production agriculture. Cloning technology in cattle has several applications outside of traditional production agriculture. These applications can include bio-medical applications, such as the production of pharmaceuticals in the blood or milk of transgenic cattle. Cloning may also be useful in the production of research models. These models may or may not include genetic modifications. Uses in agriculture include many applications of the technology. These include making genetic copies of elite seed stock and prize winning show cattle. Other purposes may range from "insurance" to making copies of cattle that have sentimental value, similar to cloning of pets. Increased selection opportunities available with cloning may provide for improvement in genetic gain. The ultimate goal of cloning has often been envisioned as a system for producing quantity and uniformity of the perfect dairy cow. However, only if heritability were 100%, would clone mates have complete uniformity. Changes in the environment may have significant impact on the productivity and longevity of the resulting clones. Changes in consumer preferences and economic input costs may all change the definition of the perfect cow. The cost of producing such animals via cloning must be economically feasible to meet the intended applications. Present inefficiencies limit cloning opportunities to highly valued animals. Improvements are necessary to move the applications toward commercial application. Cloning has additional obstacles to conquer. Social and regulatory acceptance of cloning is paramount to its utilization in production agriculture. Regulatory acceptance will need to address the animal, its products, and its offspring. In summary, cloning is another tool in the animal biotechnology toolbox, which includes artificial insemination, sexing of semen, embryo sexing and in vitro fertilization. While it will not replace any of the above mentioned, its degree of utilization will depend on both improvement in efficiency as well as social and regulatory acceptance.     

Induced abortion in cattle

Several procedures were used to abort cattle during the second and third trimesters of gestation. The treatment to abortion interval was better (P<0.05) when dexamethasone trimethyiacetate (DTMA) injections repeated at either 6 or 4 day intervals than when a single injection of DTMA was followed 6 days later by the administration of stilboestrol. The treatment to abortion interval was not significantly shorter when DTMA was repeated after 4 days rather than 5 days (0.10<P>0.05). Prostaglandin F_2α produced abortion 1 to 4 days following direct administration into the foetai fluids.Peripheral plasma progesterone concentration had a tendency to rise immediately following the second injection of DTMA given at a 6 day interval. This was followed by a decline. Two injections of DTMA given at 4 day intervals resuited in a decline in progesterone concentration. Abortion occurred when plasma progesterone concentrations were about 1 ng/ml in cows treated with DTMA. In cows treated with prostagiandin F_2α the plasma progesterone concentration fell rapidly within one day of administration to approximately 2 ng/ml, at which concentration abortion took place.