Search

Copyright of Veterinarska Stanica is the property of Croatian Veterinary Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Great teachers have the extraordinary ability to inspire and motivate even those students who resist learning. The top educators are knowledgeable not only about the content of the course they are teaching but also of the information, literature, and practice of instructional delivery to their audience. Many exemplary educators have been profiled and studied; however, there is a paucity of information pertaining to how the top animal science teachers teach. The objective of this study was to identify and describe characteristics of award-winning animal science teachers. The inclusion criterion for selecting faculty was being bestowed an excellence in teaching award through their professional organization. Each teacher answered a series of questions about themselves, their students, and the class being taught. Lecture was captured using a digital all-inclusive camera and later analyzed for pedagogical trends and instructor–student interactions. Despite a variety of topics being taught by award-winning teachers, there were multiple trends emerging from their classrooms. Common events included reviewing highlights of previous lectures, distributing something to students, posing questions during class, and calling on students by name. Each teacher taught differently, but they all understood their audience; they grasped the subject matter and most importantly, they valued students learning. Collectively, these findings can be utilized and applied by animal science teachers in their own environments in an attempt to foster improved student learning through excellent teaching. [ABSTRACT FROM AUTHOR]

Sheep are a valuable livestock species because of their ability to convert forages, as well as feedstuffs not suitable for human consumption, into meat and milk that are important sources of human dietary protein. Sheep are the most abundant ruminant livestock species in Egypt, and great opportunity exists to enhance their productivity though implementation of a genetic improvement program utilizing the advanced reproductive technologies of artificial insemination and embryo transfer. These two reproductive technologies permit the production of more offspring from genetically superior animals in a shorter amount of time than would be possible through conventional breeding. It will be important to match the appropriate breeds of sheep with the proper nutritional and production environments that will enable animals to express their full genetic potential for enhanced production of meat, milk and fiber. [ABSTRACT FROM AUTHOR]

Background: One of the factors limiting successful processing of alpaca (Vicugna pacos) semen is the viscosity of seminal plasma. The viscous nature of the collected ejaculate has hindered sperm cryopreservation as well as artificial insemination (AI) under field conditions. Aims: The objective of this investigation was to evaluate recovery, motility, and plasma membrane integrity of alpaca spermatozoa after centrifugation in one of two different solutions at one of three different combinations of speed and time. Methods: A total of 24 ejaculates was recovered from seven reproductively sound Huacaya males using a modified artificial vagina (AV) after training the animals for semen collection. A 2 × 3 factorial treatment arrangement was utilized for this study. Ejaculates were divided into fractions for centrifugation in one of two solutions (Tris extender or PureSperm®80 density gradient solution) at one of three combinations of speed and time (492 × g for 15 min, 1968 × g for 10 min, or 4448 × g for 7 min). The experiment was replicated eight times. Results: Analysis revealed that centrifugation at 4448 × g for 7 min in PureSperm®80 provided a high recovery rate of spermatozoa with the highest sperm motility and functional integrity of plasma membrane post-centrifugation. Conclusion: Results suggest that adoption of this procedure (centrifugation at 4448 × g for 7 min in PureSperm®80) in the initial processing of alpaca ejaculates may enhance subsequent ability to use semen for AI and other assisted reproductive biotechnologies in this species. [ABSTRACT FROM AUTHOR]

Embryo transfer is an animal biotechnology that is experiencing a rapidly increasing rate of adoption in production agriculture. Embryo transfer is a comprehensive set of procedures involving the production and collection of preimplantation embryos from genetically superior females (donor females) and subsequent transfer of the harvested embryos into the uteri of recipient females whose estrous cycles have been synchronized with that of the donor. Initial use of embryo transfer in the commerical livestock industry involved the surgical collection and transfer of embryos, and, hence, it was considered a veterinary procedure. However, with the advent of non-surgical embryo collection and transfer techniques, some states have now revised their state veterinary practice acts to allow non-veterinarians to perform embryo transfer for a fee. A course in embryo transfer and related technologies (e.g., embryo cryopreservation and in vitro fertilization) was developed to provide undergraduate students in agriculture with sufficient background information so that they could either pursue further training in the field or alternatively engage in meaningful dialogue with embryo transfer technicians whom they employ. The objective of this presentation is to provide readers with an overview of the development, implementation, and 10-year experience in teaching this course at Iowa State University. Prerequisites for the course include a course in reproductive physiology, and students who enrolled in the course without the necessary prerequisite achieved lower mean course grades than students who had completed the prerequisites. Student enrollment for the initial course offering was 9, but enrollment grew to as many as 38. Student evaluations of the course indicated that a hands-on laboratory course would be helpful, and such a course was developed and implemented. Three students who have taken these courses are now actively engaged in commercial embryo transfer, while other students are actively using embryo transfer in their livestock breeding operations. [ABSTRACT FROM AUTHOR]

To investigate the impacts of uterine type and conceptus genotype on development through late gestation, Meishan and Yorkshire embryos were co-transferred into the uteri of either Meishan or Yorkshire recipients that were subsequently slaughtered on Day 90 of gestation. At slaughter, regardless of conceptus genotype, fetuses and placentae were markedly smaller when recovered from Meishan than from Yorkshire recipients. Whereas Meishan and Yorkshire fetuses recovered from Meishan uteri were similar in weight, Meishan fetuses were markedly lighter than littermate Yorkshire fetuses when recovered from Yorkshire uteri. Because of the marked differences between fetal weights observed in Yorkshire recipients on Day 90 of gestation, Meishan and Yorkshire embryos were co-transferred to Yorkshire recipients that were allowed to farrow. Surprisingly, Meishan and Yorkshire fetuses cogestated in Yorkshire recipients were born at similar weights, whereas Meishan placentae were markedly smaller. The weight of Meishan placentae were similar on Day 90 and at term, whereas the weight of Yorkshire placentae were markedly larger (approximately 70%) at term than on Day 90. The constant weight of Meishan placentae from Day 90 to farrowing appears to result from an ability to increase their vascularity during this interval. In contrast, Yorkshire placentae may be forced to increase their weight to keep pace with fetal growth during this period. Because uterine capacity sets the upper limit on litter size, the decreased endometrial surface area required per conceptus in the Meishan pig seems to explain its greater potential for increased litter size.

The aim of this research was to determine the effects of L-cysteine and beta-mercaptoethanol on the in vitro development of bovine embryos that had been produced in vitro. A 2 x 3 factorial arrangement of treatments was used to evaluate the effect of 0.63 or 6.9 microM L-cysteine and 0, 10, or 100 microM beta-mercaptoethanol on the development of bovine embryos in a chemically defined medium. Embryos containing 6 to 8 cells were randomly allocated to one of the six treatment combinations and were cultured for 7 d. Both beta-mercaptoethanol and L-cysteine increased the number of embryos that reached the blastocyst stage of development, although no interaction was observed between the compounds. Embryos that were cultured in the presence of beta-mercaptoethanol had more cells at the blastocyst stage than did embryos cultured in medium without beta-mercaptoethanol. These findings provide evidence that beta-mercaptoethanol and L-cysteine promote increased embryonic development and that beta-mercaptoethanol increases the number of cells in bovine embryos produced in vitro and cultured in a cell-free, protein-free culture system.

The objectives of this research were to determine the effects of beta-mercaptoethanol (beta-ME) and fetal bovine serum (FBS) on in vitro development of bovine embryos derived from oocytes matured and fertilized in vitro and to examine the mechanism through which beta-ME may influence embryo development. A 2 x 2 factorial treatment arrangement was used to evaluate the effect of 0 or 100 microM beta-ME and 0% or 10% FBS on embryos cultured in Medium 199 (M199) in the absence of somatic cells. Embryos were randomly allocated within stage of development (< 8 cells or 8-16 cells) to one of four treatment combinations and were cultured for 6 days. Both beta-ME and FBS promoted increased (p < 0.01) development of embryos to the blastocyst stage, and their effects were greater (p < 0.01) in 8- to 16-cell embryos than in embryos having fewer than 8 cells at the initiation of treatment. The cysteine and cystine content of M199, with and without beta-ME, were determined by HPLC. Medium supplemented with beta-ME contained neither cysteine nor cystine, and it is suggested that these compounds were converted into a mixed disulfide between cysteine and beta-ME. These results indicate that beta-ME is capable of enhancing bovine embryo development in a cell-free, serum-free culture system.

The effect of sex on pig conceptus development to day 12 of gestation was investigated. On day 2 of gestation, reciprocal embryo transfers were performed resulting in four groups (Yorkshire-Yorkshire, Yorkshire-Meishan, Meishan-Yorkshire and Meishan-Meishan). Conceptuses at day 12 were recovered from each recipient and diameter, as well as DNA, protein and oestradiol content were determined for individual conceptuses. The sex of individual conceptuses at day 12 was determined by amplification of a fragment of the pig SRY gene, using the polymerase chain reaction. Embryos developed more rapidly to day 12 in Yorkshire recipients, but there was no detectable effect of sex on the diameter, DNA, protein or oestradiol content of conceptuses from any transfer group. Thus, no sex effect was apparent under conditions either promoting or retarding the rate of early pig blastocyst growth. These results provide strong evidence that pig embryonic development occurs at a rate determined by uterine environment and not by sex of the conceptus.

Day 12 blastocysts from Meishan gilts contain fewer cells than do day 12 blastocysts from Yorkshire gilts. The purpose of this study was to evaluate the effect of breed on the relative numbers of inner cell mass and trophectoderm cells in Meishan and Yorkshire embryos at similar stages. Embryos were collected on days 5.5-6.5 of gestation and were subjected to image analysis and differential cell staining. No breed differences were detected in the thickness of zona pellucida or in the areas of the perivitelline space, embryo proper, blastocoel and inner cell mass at any of the developmental stages examined (compact morula, early blastocyst or blastocyst). However, differences were observed in the pattern of growth of embryos from Meishan versus Yorkshire gilts. The total number of cells of Meishan embryos from Meishan gilts increased progressively from the compact morula through the blastocyst stage, whereas the total number of cells of embryos from Yorkshire gilts remained constant from compact morula through to early blastocyst, and then increased markedly from the early blastocyst to the blastocyst stage. At the blastocyst stage, Meishan embryos contained fewer (P < 0.05) cells than did Yorkshire embryos, and this lower number of cells was due entirely to fewer (P < 0.05) trophectoderm cells. As the number of inner cell mass cells increased during embryonic growth, Meishan embryos exhibited a slower (P < 0.02) increase in the number of trophectoderm cells than did Yorkshire embryos. These results demonstrate that the reduced number of cells present in Meishan embryos results from a selective reduction in the number of trophectoderm, but not inner cell mass, cells.

Prenatal mortality in European pigs is estimated at 30-40%, the majority of which occurs between days 12 and 18 after mating. Chinese Meishan pigs are prolific, averaging three to five more pigs per litter than do European breeds. Early reports into the fecundity of Meishan females suggested that their prolificacy resulted from lower embryonic mortality when compared with European females exhibiting the same ovulation rate. The preponderance of evidence suggests that there are no differences between Meishan and European breeds in either morphological embryo diversity within a litter or embryo mortality before day 12 after mating. Recent studies from our laboratory suggest that preimplantation embryos from Meishan females exhibit markedly reduced growth rates and oestrogen secretory activities through day 12 when compared with embryos from Yorkshire females. The significantly reduced conceptus sizes of Meishan versus European breeds on day 30 of gestation provide additional evidence of the reduced growth rate of Meishan embryos. Furthermore, because embryonic oestrogen production is known to alter uterine secretion of histotroph, the lower oestrogen production by Meishan embryos in the Meishan uterus may result in more gradual alterations in the uterine environment that are beneficial for conceptus survival and subsequent litter size. Recent studies using cross-transfer of Meishan and Yorkshire embryos on day 2 after mating have led to the suggestion that there is a major effect of recipient genotype on embryonic growth rate and oestrogen secretion. In these studies, both Meishan and Yorkshire embryos transferred to Meishan uteri exhibited marked decreases in morphological development and oestrogen content on day 12 when compared with embryos transferred to Yorkshire recipients. These data suggest the presence of factor(s) in endometrial secretions from Meishan females that reduce the growth rate and oestrogen secretory potential of preimplantation conceptuses.

One- to four-cell embryos were collected from multiparous crossbred ewes and were cultured in vitro for 120 hours in CZB medium. A 2x2 factorial treatment arrangement was used to examine the effects of glucose and ethylenediaminetetraacetic acid (EDTA) on in vitro embryo development. The embryos were examined every 12 hours, and all of the embryos were stained with a DNA-specific fluorochrome after the 120-hour evaluation to enable the counting of cell nuclei. Embryo development was analyzed for cleavage beyond 16 cells as well as for cleavage to at least the compact morula stage based upon both the 120-hour morphological evaluation and nuclear counts. Forty-eight percent of the embryos passed through the in vitro developmental block (i.e., cleaved beyond 16 cells), and 26% developed to 30 or more cells. Neither EDTA nor glucose affected in vitro embryo development based on the nuclear counts.