Climatic factors affecting quantity and quality grade of in vivo derived embryos of cattle.

The present study investigated the effects of climatic variables on the quality grade and quantity of in vivo derived cattle embryos in the Midwestern United States. Climatic information included greatest and least daily temperature, average daily wind speed and average temperature-humidity index for each of the 765 records. The response variables included the number of ovarian structures, viable embryos, quality grade 1 embryos, quality grade 2 embryos, quality grade 3 embryos, freezable embryos (sum of quality grade 1 and quality grade 2 embryos), transferable embryos (sum of quality grade 1-3 embryos), degenerate embryos and unfertilized ova. Measures for variables among the breeds of donors and sires grouped by geographical origin were compared. A negative effect of greater temperatures during the early embryonic development stage tended (P < 0.10) to be associated with a decrease in the quality of embryos recovered. Interestingly, the greater the Temperature-Humidity Index (THI) during the early ovarian antral follicular development stage 40-45 days prior to ovulation was associated with a tendency for greater numbers of total number of freezable and transferable embryos recovered per uterine flushing (P < 0.10). Increased wind speed at the early antral follicular phase 40-45 days prior to ovulation was associated with an increase in the percentage of quality grade 1 embryos recovered (P < 0.05). Wind speed during the estrous synchronization period was also associated with a lesser number of embryos recovered (P < 0.05). This retrospective study confirms that climatic variables have significant effects on the in vivo production of cattle embryos and that wind speed should be considered in future analyses of factors affecting embryo quality.

Effects of a naturally occurring amino acid substitution in bovine PrP: a model for inherited prion disease in a natural host species.

OBJECTIVE: The most common hereditary prion disease is human Creutzfeldt-Jakob disease (CJD), associated with a mutation in the prion gene resulting in a glutamic acid to lysine substitution at position 200 (E200K) in the prion protein. Models of E200K CJD in transgenic mice have proven interesting but have limitations including inconsistencies in disease presentation, requirement for mixed species chimeric protein constructs, and the relatively short life span and time to disease onset in rodents. These factors limit research on the mechanism by which the mutation drives disease development. Therefore, our objective was to provide the first assessment of cattle carrying the homologous mutation, E211K, as a system for investigating longer-term disease mechanisms. The E211K substitution was associated with a case of bovine spongiform encephalopathy from 2006. RESULTS: We assessed the molecular properties of bovine E211K prion protein, characterized the molecular genetics of a population of cattle E211K carriers (offspring of the original EK211 cow) in relation to findings in humans, and generated preliminary evidence that the impacts of copper-induced oxidative stress may be different in cattle as compared to observations in transgenic mouse models. The cattle E211K system provides the opportunity for future analysis of physiological changes over time.

Embryo Transfer (Techniques, Donors, and Recipients).

Commercial embryo transfer has evolved as an art and as a science since the early 1970s. Today's multiple ovulation embryo transfer is a widely used reproductive tool on many farms and is performed by veterinarians throughout the world. Propagation of the female genomes of select donors, through embryo transfer, has allowed a rapid progression of genetic gain in many breeds, much like what happened with artificial insemination since the 1940s. Advancement of this technology is migrating to in vitro fertilization technology today, allowing a higher volume of offspring to be produced with sex selection in the laboratory.

Effects of label-dose permethrin administration in yearling beef cattle: I. Reproductive function and embryo quality of superovulated heifers.

The objective was to study the effects of a commercial pyrethroid-based pour-on product, permethrin, on reproductive performance in superovulated beef heifers by assessing steroid biosynthesis and embryo quality. Nonpregnant, yearling beef heifers (n = 10; 418 ± 33 kg; 5.5 ± 0.2 body conditioning scores) were assigned by body weight and breed to either (1) saline control or (2) permethrin pour-on administered at label dose (PYR). Superovulation was achieved on all heifers using a timed, 17-day, CIDR-based protocol with GnRH and PGF2α and decreasing total dosage of 240-mg FSH administered twice daily for 4 days. Heifers were artificially inseminated twice (at onset of estrus and 12 hours later) by same technician with frozen semen from single bull collection. To determine short- and long-term effects of permethrin on embryo quality and steroid biosynthesis, superovulation was initiated twice with collection of embryos occurring at 17 and 51 days after treatment. Embryos were recovered 6.5 days after first artificial insemination via nonsurgical flush and were evaluated by International Embryo Transfer Society standards. Blood was collected at standing estrus and day of embryo recovery. Estradiol (E2) and progesterone (P4) concentrations were analyzed via RIA. MIXED and GLIMMIX procedures of SAS were used to analyze continuous and categorical data, respectively. Heifer per flush was the experimental unit. Total embryos recovered did not differ because of treatment (P = 0.30), but did decrease in flush 2 compared with flush 1 (P = 0.02). Quality grade, total transferable quality embryos, and overall flush success did not differ because of treatment (P ≥ 0.16). However, transferable quality embryos were decreased in flush 2 compared with flush 1 (P = 0.05). Total unfertilized oocytes were greater in saline control (P = 0.04). The PYR heifers tended to have less total P4 (P = 0.15) and P4 per CL (P = 0.06) at recovery. E2 per ovulated follicle and E2 per total ovarian structure was greater in flush 2 (P ≤ 0.03) but did not differ because of treatment (P ≥ 0.23). In summary, these data indicate that permethrin administration at label dose in superovulated beef heifers has a tendency to reduce P4, but embryo quality is not affected.