What best animal science teachers do.

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.

Motility and recovery of alpaca (Vicugna pacos) spermatozoa after centrifugation in a density gradient solution.

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.

Factors influencing the success of embryo transfer in the pig.

Progress in reproductive biotechnologies has led to an increased use of embryo transfer in both swine research and swine production. This review article describes the history and subsequent development of porcine embryo transfer. Special attention is given to aspects of the overall process of embryo transfer which are unique to pigs.

Promotion of development of bovine embryos produced in vitro by addition of cysteine and beta-mercaptoethanol to a chemically defined culture system.

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.

Development of Meishan and Yorkshire littermate conceptuses in either a Meishan or Yorkshire uterine environment to day 90 of gestation and to term.

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.

beta-mercaptoethanol enhances blastocyst formation rate of bovine in vitro-matured/in vitro-fertilized embryos.

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.

Lack of effect of sex on pig embryonic development in vivo.

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.

A comparison of the number of inner cell mass and trophectoderm cells of preimplantation Meishan and Yorkshire pig embryos at similar developmental stages.

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.

Investigations into the control of litter size in swine: III. A reciprocal embryo transfer study of early conceptus development.

A reciprocal embryo transfer study with Meishan and Yorkshire pigs was conducted to examine the influence of embryonic genotype and uterine environment on preimplantation embryonic growth and development. Embryos were collected from gilts on d 2 of a spontaneous estrous cycle (d 0 = onset of estrus), transferred to synchronous recipients, and collected from recipients on d 12 to obtain measurements of embryonic diameter (size) and embryonic DNA, protein, and estrogen content. No difference was detected between Meishan and Yorkshire donors for number of ovulations, number of embryos recovered, or number of cells per embryo. Embryonic genotype affected (P < .01) d-12 embryonic characteristics; Meishan embryos (n = 101) were smaller (4.7 mm diameter) and contained less DNA (4.5 micrograms) and protein (104 micrograms) than Yorkshire embryos (n = 85; 5.9 mm, 6.1 micrograms, and 149 micrograms, respectively). Embryos (n = 80) transferred into a Meishan uterus were reduced (P < .001) in diameter (4.2 vs 6.4 mm) and in DNA (3.2 vs 7.2 micrograms), protein (103.8 vs 149 micrograms), and estrogen (352 vs 1,643 pg) content compared with embryos (n = 106) transferred into a Yorkshire uterus. These data indicate that the increased prolificacy of the Meishan breed may be due to an increased embryonic survival resulting from slower growing embryos and a suppressive effect of the uterus on embryonic growth rate and estrogen secretion.

Investigation of cryoprotectant toxicity to porcine embryos.

The objective of this study was to examine the potential toxicity of sucrose (Experiment 1) and of various cryoprotectants (Experiment 2) to porcine preimplantation embryos. In Experiment 1, 65 embryos, ranging from compact morulae to hatched blastocysts, were allocated within donor female across 5 concentrations of sucrose (0, 0.25, 0.50, 1.0, 2.0 M) to determine the highest concentration that would not inhibit subsequent embryo development. After a 48-h post-treatment culture period, the embryos were stained and cell nuclei were counted. The concentration of sucrose affected embryo development (P < 0.001) and embryo quality (P < 0.001). Embryos placed into 2.0 M sucrose exhibited poorer development and quality than embryos at the lower 4 concentrations, which were not different from one another. In Experiment 2, 182 embryos of the same developmental stages as in Experiment 1 were collected from 16 donors. Embryos were allotted within donor female to 2 of the 5 concentrations (10, 20, 30, 40, or 50%) of each of 3 cryoprotectants (ethylene glycol, propylene glycol, glycerol). After a 30-sec exposure to a cryoprotectant, the embryos were cultured and stained as in Experiment 1. As the concentration of an individual cryoprotectant increased beyond 30%, embryo development decreased. Embryos exposed to glycerol or propylene glycol exhibited poorer development than did embryos placed into ethylene glycol, especially at concentrations of 40% or higher.

Investigations into the control of litter size in swine: I. Comparative studies on in vitro development of Meishan and Yorkshire preimplantation embryos.

Three experiments were conducted to examine the in vitro development of preimplantation embryos from the prolific Chinese Meishan pig. Experiment 1 was conducted to assess whether Meishan embryos would develop in vitro and retain their viability, whereas Exp. 2 and 3 examined the developmental pattern of Meishan embryos. In all three experiments, Yorkshire embryos served as a contemporary comparison. Ovulation and embryo recovery rates were not different between Meishan and Yorkshire gilts. Meishan embryos cultured for 96 h were capable of establishing pregnancies. The number of cell nuclei present after 144 h of culture was lower (P < .01) for Meishan than for Yorkshire blastocysts. Meishan preimplantation embryos exhibited a slower (P < .02) in vitro rate of development from the four-cell to the compact morula stage than did Yorkshire embryos. Early blastocysts from Meishan gilts, although morphologically similar in size, contained fewer (P < .06) cells than did their counterpart Yorkshire embryos. These data demonstrate that Meishan embryos develop more slowly and contain fewer cells than do Yorkshire embryos. This differing developmental pattern of Meishan preimplantation embryos, if similar to that previously reported in miniature swine and mice, may relate to increased embryo survival.

Early embryonic development in prolific Meishan pigs.

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.

In vitro development of ovine embryos in CZB medium.

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.