Factors in cattle affecting embryo transfer pregnancies in recipient animals.

The use of embryo transfer (ET) in cattle is important for profitability and improved genetic gains. The advent of the commercial embryo collection and transfer industry has led to advancements in multiple techniques and practices. Specific variables, however, have historically affected pregnancy rates but an understanding of the magnitude of these effects in the current industry is limited. Transfer location (cranial, middle, or caudal third of the uterine horn ipsilateral to the ovary with a CL), transfer score (range of 1-3 with 1 being excellent and 3 poor, based on difficulty of accessing the site of embryo deposition), and amount of time to complete a transfer, therefore, were recorded. These variables were collected in a setting designed to mimic commercial production practices as well as exaggerated time (due to data collection) to assess effects on pregnancy rates. Fresh and frozen in vivo-derived embryos (n = 256) from Bos taurus cows were transferred to Bos taurus recipients. There tended to be more pregnancies when embryos were deposited in the cranial part of the uterus (P = 0.08) compared to the middle and caudal third of the uterus. With a lesser degree of difficulty in transfers (score 1), there tended to be more pregnancies established (P = 0.07). When lesser time was needed for transferring embryos and collecting data, there were greater pregnancy rates (P = 0.03). Thus, these traditionally accepted variables of influence (site of embryo placement in uterus, difficulty, and time) continue to influence ET pregnancy success.

Producer attitudes and practices related to antimicrobial use in beef cattle in Tennessee.

OBJECTIVE: To evaluate knowledge, attitudes, and management practices involving antimicrobial use among Tennessee beef producers. DESIGN: Mail survey. SAMPLE POPULATION: A population-based, stratified random sample of 3,000 beef producers across the state. PROCEDURES: Questionnaires were mailed to beef producers. Questions focused on producer practices related to education, biosecurity, veterinary use, and the purchase and use of antimicrobials. Operation types were categorized as either cow-calf only or multiple operation type (MOT). Associations between various factors and antimicrobial use were evaluated by use of multivariable logistic regression, with the outcome variable being any antimicrobial use (injectable or by mouth) in the past year. RESULTS: Of 3,000 questionnaires mailed, 1,042 (34.7%) were returned. A significantly higher proportion of producers with MOTs reported giving antimicrobials by mouth or by injection than did producers with cow-calf only operations. In addition, higher proportions of producers with MOTs than producers with cow-calf only operations reported treating with macrolides, florfenicol, ceftiofur, and aminoglycosides. In the multivariable analysis, herd size>50 cattle, participation in Beef Quality Assurance or master beef producer certification programs, quarantining of newly purchased animals, use of written instructions for treating disease, and observation of withdrawal times were associated with a higher likelihood of antimicrobial use. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that producers who engaged in more progressive farming practices were also more likely to use antimicrobials. Incorporating training on judicious antimicrobial use into educational programs would likely increase awareness of best management practices regarding antimicrobial use.

Fetal losses and pathologic findings of clones derived from serum-starved versus serum-fed bovine ovarian granulosa cells.

The objective was to evaluate development of cloned embryos constructed with serum-starved versus fed ovarian granulosa cells. Fusion of somatic cells with cytoplasts (50.7 and 50.7%; SEM=5.5), development of cloned embryos to 8-16-cell (59.4 and 62.6%; SEM=6.4), and compact morula/blastocyst-stages (24.9 and 26.5%; SEM=8.5) was similar for serum-starved and fed groups. More heifers were confirmed pregnant with clones derived from serum-starved cells (9/13, 67.2% versus 11/25, 44%). However, embryonic loss between 29-50 days was greater for clones constructed with serum-starved (88.9%) versus fed (36.4%) cells. Development of clones derived from serum-fed cells through placentation and differentiation was not predictive of competency to term. Fetal deaths occurred in the majority of late term pregnancies as a result of complications from hydrallantois. Only one fetus derived from serum-fed ovarian granulosa cells developed to term (278 days). At birth and for approximately 9 consecutive months thereafter, routine veterinary examinations confirmed expected growth patterns. In summary, the use of serum fed granulosa cells for nuclear transfer was coincident with a high incidence of third trimester losses associated with hydrallantois and fetal oversize.

Effects of administration of ergotamine tartrate on fertility of yearling beef bulls.

Sixteen yearling bulls were utilized to investigate administration of ergotamine tartrate on semen parameters, fertilization, and endocrinology. Bulls were allotted to a control diet of cracked corn, corn silage, and soybean meal (CON, n = 8) or a diet supplemented daily with 40 microg/kg body weight of ergotamine tartrate (ET, n = 8). Blood samples, average daily gain, scrotal circumference and rectal temperatures were collected every 14 day. Semen samples were obtained every 60 day and evaluated for motility and morphology. Scrotal temperatures were obtained by thermography immediately before electroejaculation. Semen from a subset of bulls from each treatment was also evaluated for in vitro fertilization. Administration of ET increased rectal temperature and resulted in lower scrotal temperatures compared to CON bulls (P < 0.05). However, prolactin, scrotal circumference, testosterone, and semen motility and morphology did not differ between groups throughout the experimental period (224 day). Cleavage rates of embryos derived from in vitro fertilization (IVF) with semen of bulls, fed with ET, were reduced compared to CON (P < 0.05); however, development of cleaved embryos to blastocyst did not differ between treatments. In conclusion, extended exposure of bulls to ET appeared to reduce fertilization potential of sperm.