Browsing by Author "Nebel, Raymond L."

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    Analysis of early lactation reproductive characteristics in Holstein cows
    Walters, Anneke H. (Virginia Tech, 2000-09-12)
    Ultrasound-guided transvaginal follicular aspiration was used to obtain oocytes from cows to study follicular development and oocyte morphology. Follicular aspiration was conducted once during wk 1 to 12 postpartum on 120 lactating cows with 6 groups, separated by biweekly intervals. Approximately one half of the aspirated cows at each session were from the early groups (wk 1-2, 3-4, or 5-6) and the other half from the later groups (wk 7-8, 9-10, or 11-12). On the day of aspiration the number of follicles on each ovary, and their sizes, small (2-5 mm), medium (6-10 mm) and large (≥ 11 mm), were recorded. The collected oocytes were morphologically classified into 4 grades, with 4 = excellent, 3 = good, 2 = fair, and 1 = poor. Blood samples from the jugular vein and follicular fluid samples from the largest follicle were collected in order to perform hormone and metabolite assays. Environmental data were obtained from the local airport. There was a significant (P < .01) quadratic days pre- and postpartum by parity interaction for BCS. Body condition score for older cattle was the lowest at 90 d prior to calving and changed the least amount over time, while youngest cattle had the highest initial BCS at d 90 prior to calving and had the greatest change in BCS over time. Body condition score was the highest during summer calving season (3.3 ± .06) compared to BCS during winter calving season (2.6 ± .06). But the loss in BCS was greater for cows that calved in summer (-0.53 ± .06) compared to cows that calved in winter (-0.07 ± .08). Increased serum NEFA concentrations with simultaneous decreases in serum insulin concentrations for younger cattle implied a more negative EB status than for older cattle. The total number of follicles and total number of oocytes retrieved was significantly (P < .001) affected by a linear days postpartum by parity interaction with younger cattle having linear increases compared to decreases in the total number of follicles for older cattle. Oocyte quality score was affected by the quadratic days postpartum by parity interaction (P < .01) and calving season (P < .01). Younger cattle had higher initial quality scores compared to older cattle, but older cattle had higher quality oocytes towards the end of the 12 wk period compared with younger cattle. Younger cattle had higher E2 and IGF-I concentrations in follicular fluid associated with a higher number of total follicles and number of oocytes, compared to older cattle. However, oocyte quality of younger cattle seemed to be reduced and oocytes were less competent than for older cattle. Cattle in 3rd and greater lactation showed very little change in BCS and hormone and metabolite measures during early lactation, with no apparent decrease in oocyte quality, despite the aging effect on follicle numbers. This study demonstrated that conditions related to early lactation have a negative effect on oocyte quality and endocrine measures of dairy cattle and that animals of different ages are differentially affected.
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    Artificial Induction of Lactation in Nonbreeder Dairy Cows
    Jewell, Tracy Michelle (Virginia Tech, 2002-08-09)
    Thirty-four cows (26 Holsteins and 8 Jerseys) were subjected to an estrous synchronization protocol administering 2 PGF2Æ Ã injections 11 d apart prior to beginning the lactation-induction protocol. Artificial induction of lactation yielded a 92% success rate for Holstein cows with success defined as achieving >9 kg milk/d, and a 88% success rate for Jersey cows with success defined as achieving > 5 kg milk/d. Mean accumulated milk yield for induced cows at 150 DIM was 65% of mean yield for nontreated cows. Mean peak milk yield for lactation- induced Holsteins and Jerseys was 32 kg/d and 20 kg/d, respectively. Mean serum and milk progesterone concentrations for samples collected during the first 6 d of lactation were not different between lactation-induced and nontreated cows. However, mean serum estradiol concentrations for induced cows were higher (P <0.05) in samples collected 3 and 5 DIM. Lactation-induced cows exhibited an increase in serum alpha-lactalbumin concentrations 2 d prior to initiation of milking, reaching values of ~260 ng/ml. Mean days-to-first service was greatly reduced in cows induced into lactation compared to nontreated cows, while mean services per conception was similar between induced and nontreated cows. Mean days to conception was lower for induced cows than for nontreated cows. By 150 DIM, pregnancy rate of induced cows was 70%, whereas nontreated cows averaged 56% pregnancy rate.
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    Bovine embryo microinjection, culture, microsurgery, and DNA analysis by the polymerase chain reaction technique
    Sparks, Amy Elizabeth Thuemmel (Virginia Tech, 1992)
    The first experiment was conducted to determine the optimum in vitro culture system for one-cell bovine embryos. Subsequent experiments compared bisection and biopsy for acquisition of cellular material from bovine morulae for DNA amplification by the polymerase chain reaction technique (PCR), and evaluated the use of DNA microinjection, in vitro culture, morula bisection, and PCR for production and selection of transgenic bovine preimplantation embryos. In vivo fertilized one-cell bovine embryos were cultured in TCM-199 (n=46), co-cultured with bovine oviductal epithelial cells (OEC; n=38), or in explanted immature mouse oviducts (n=54). Of the embryos that cleaved once, 52.6, and 30.4 and 0.0% developed to morulae/blastocysts after culture in OEC, TCM-199, and explanted mouse oviducts. Mean cell number for embryos cultured in OEC (24.5) was higher than for embryos cultured in TCM-199 (12.8) or in explanted mouse oviducts (5.9; P<.05). Bovine morulae were subjected to bisection (n=44; 20 to 30 cells) or biopsy (n=50; 8 to 12 cells) to assess embryo development in vitro and compare the efficiency of PCR amplification of an endogenous 18S rRNA. Mean development scores (l1=degenerate, 2=morula, 3=blastocyst) and mean cell number after microsurgery and 48 h of culture did not differ between treatments (P>.05; 2.4 ± .1 and 41.8 ± 2.5 versus 2.3 ± .1 and 48.8 ± 2.9, respectively). Frequency of the 18S rRNA amplifications was similar (P>.05) for demi-morulae (78%; 32/41) and biopsies (81%; 39/48). In the third experiment, in vivo fertilized one- (n=155), two- (n=57) and four-cell (n=62) bovine embryos were collected for pronuclear and nuclear DNA microinjection. Approximately 70% of the embryos were injected with DNA and 30% served as controls. Injection did not affect (P>.05) mean development scores after 144 h of cultured in TCM-199 with OEC. Sixty-five (34%) of the DNA injected embryos developed to morulae and were bisected. Injected DNA was amplified by PCR in 29% (19/65) of the demi-morulae. Frequency of DNA detection was more frequent (P<.01) in morulae injected at the 1-cell stage (50%: 16/32) than at the 2-cell (10%; 1/10) or 4-cell (9%: 2/23) stage. Production and selection of transgenic bovine morulae was most successful when one-cell bovine embryos were microinjected.
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    Comparison of three estrus detection systems during summer heat stress in a large commercial dairy herd
    Peralta, Oscar A. (Virginia Tech, 2003-06-12)
    The objective of the study was to compare three systems for detection of estrus and combinations of these systems on a large commercial dairy (1000 lactating cows) during stress of summer heat. At 37 to 45 days in milk (DIM), 266 cows were fitted with a HeatWatch (HW) device (HeatWatch; DDx Inc., Boulder, CO), an activity (A) sensor (ALPRO; DeLaval Inc., Kansas City, MO), and observed visually (V) twice daily. Pregnancy status was determined by uterine palpation 35 to 49 d following artificial insemination (AI). The effects of DIM, parity, physical activity, standing events, months, AI technician, and interval between onset of estrus and AI on conception rate were determined using linear contrasts and logistic regression. Efficiencies for detection of estrus, determined by comparing detected periods of estrus with a theoretical total of 707 periods, were 45.8% (V), 33.2% (A), 40.3% (HW), and 71.6% for all three systems simultaneously. Conception rates (LSM ± SE) by method of detection were 16.7 ± 4.9 for HW, 19.8 ± 5.5 for A, 7.9 ± 3.4 for V, 16.3 ± 6.0 for V + A, 27.6 ± 4.6 for V + HW, 21.1 ± 4.9 for A + HW, and 21.9 ± 4.5 for V + A + HW. Conception rate and number of mounts decreased for cows in first versus second and third parity (P < 0.05). For periods of estrus detected by A, the lowest conception rate (P < 0.05) occurred >18 h after the onset of estrus (16.7 ± 7.9). The highest conception rate occurred with the combination of V + HW, which confirms the premise that combination of multiple systems enhances both the efficiency and accuracy of detection.
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    Cystic ovaries in dairy cows
    Nebel, Raymond L. (Virginia Cooperative Extension, 1994)
    Although cystic ovarian disease is one of the oldest recorded diseases in dairy cattle, it remains a major problem in many dairies.
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    Development of an expert system for the evaluation of reproductive performance and management of Virginia dairy farms
    Domecq, Joseph John (Virginia Tech, 1990-08-05)
    An expert system for dairy herd reproductive management for microcomputer was developed using an expert system shell and Turbo Pascal. A dairy extension reproductive specialist provided information for the system and empirical support was provided by research. The expert system initially examines days open, days to first insemination, percent of possible estruses observed, and number of breedings per conception to determine whether a problem exists. Interpretations ranging from “excellent” to “severe” were established for each parameter. “Excellent” and “adequate” interpretations correspond to a 12 to 13 mo calving interval. The system then selects for evaluation one of three areas that influences days open; days to first insemination, efficiency of detection of estrus, or conception percentage. Once an area has been selected for further evaluation, the expert system utilizes information from the user and from DHIA reproductive management reports developed by the Dairy Records Processing Center in Raleigh, NC. The reproductive reports are captured in a computer file and read by the expert system to identify problems of conception categorized by production, parity, service, days in milk, breed, and service sire. In addition, questions are asked by the expert system to isolate problems in data accuracy, semen handling, AI technique, detection of estrus, signs of estrus, and other management areas. Recommendations and suggestions are given. The expert system was designed to be used by extension personnel who may not have extensive knowledge of computers or reproductive management. The compiled program runs on an IBM compatible personal computer with 640K memory. Ten Virginia DHIA herds with conception problems were evaluated by the expert system and the extension specialist. Of 100 potential problem areas, the expert system and extension specialist identified 47, agreeing on 85% of them. Most discrepancies resulted from the expert applying a more restrictive standard when values were close to a preselected threshold.
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    Development of mouse morulae after encapsulation in alginate microgels or poly-l-lysine microcapsule
    Krentz, Kathleen J. (Virginia Tech, 1991-07-16)
    Three experiments were conducted to evaluate in vitro and in vivo development of zona pellucid a-intact (ZPI) and zona pellucida-free (ZPF) mouse embryos after encapsulation in either 2% sodium alginate or 0.1% poly-L-Iysine (PLL). In Experiment 1, rate of development of ZPI embryos (n = 150) from morulae to hatched blastocysts was measured after encapsulation in alginate or PLL and as unencapsulated controls. Following encapsulation, developmental stages were recorded every 24 h for 120 h. Percentage of encapsulated embryos completely hatched from the zona pellucid a were not different from each other but were lower than unencapsulated controls at 48, 72, 96 and 120 h. Development of ZPI and ZPF mouse embryos after encapsulation in either alginate or PLL was examined in Experiment 2. Developmental stages and diameters were recorded every 24 h for 72 h. At 72 h, embryos were stained and fixed on slides to examine nuclei. Percentage of ZPI embryos developing to expanded blastocysts, their diameters and nuclear counts were not different from each other or from ZPF embryos. Percentage of ZPI embryos initiating hatching or completely hatched from the zona pellucida, their diameters and nuclear cell numbers were also similar. In the final experiment, ZPI mouse morulae were unencapsulated or encapsulated in either alginate or PLL and transferred into recipients to examine in vivo development. Recipients were allowed to develop fetuses to term. Recipients receiving encapsulated embryos failed to deliver pups. However, five of six recipients of unencapsulated embryos (n = 71) delivered a total of 16 live pups. Additional transfers were performed to examine viable fetuses and resorption sites on day 10 of gestation. Pregnancy rates, diagnosed by the presence of via bIe fetuses or resorption sites, were similar for all treatments: unencapsulated (71.4%), a1ginate (87.5%) and PLL (87.5%). However, the total number of viable fetuses present was higher for unencapsulated embryos (42.1 %) when compared to embryos in alginate microgels (17%) and embryos in PLL microcapsules (14.60/0). Additionally, recipients of alginate and PLL encapsulated embryos had more resorption sites (4 0/0 and 13.4%) when compared to recipients of unencapsulated embryos (0%). These investigations demonstrated that development of encapsulated ZPI mouse morulae is impaired at the hatched blastocyst stage; however, encapsulated ZPI and ZPF mouse morulae develop similarly in size and nuclear counts. In vivo development of ZPI morulae was also impaired due to an asynchronous condition between the uterine environment and the developing embryos.
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    Effect of energy and undegraded intake protein on growth and feed efficiency of growing Holstein heifers
    Bethard, Greg L. (Virginia Tech, 1994-09-30)
    Two trials using 32 heifers each evaluated response to undegraded intake protein (UIP) (30 or SO% CP), energy (supporting .S9 or .91 kg ADG), and source of UIP (blood meal or combination protein supplement). Trial one was a 2x2 factorial, with two levels of energy and UIP. High UIP was achieved with blood meal supplementation. From 6-13 mo of age (phase I), high energy increased ADG and DMI, and high UIP decreased DMI. DM efficiencies (kg DMIlkg BW gain) improved with high energy and high UIP, and roN efficiencies (kg IDN/kg BW gain) improved with high UIP. From 13 mo until calving (phase n), heifers were housed together and fed a common diet. Low energy, high UIP treatment had the highest ADG (1.01 kg/day) for phase I, but the lowest for phase n (.33 kg/day), and low energy, low UIP treatment had the lowest ADG (.62 kg/day) for phase I, but the highest for phase n (.S3 kg/day). Overall ADG from 6 mo until calving averaged .S9 kg/day, and was not affected by energy or UIP. In trial 2, two levels of energy and two sources ofUIP were compared, resulting in four treatments: low energy, high UIP with combination protein supplement; low energy, high UIP with blood meal; low energy, low VIP with soybean meal; and high energy, low UIP with soybean meal. Combination protein supplement contained blood meal, com gluten meal, and fish meal. Trial was 300 days long, and began at 6.5 mo. of age. Dry matter intake and ADO were increased with high energy, but not affected by VIP. Overall DM efficiency was not affected by VIP or energy level. Results of both trials indicate VIP may improve feed efficiency of growing Holstein heifers.
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    Effect of high and low dosage of fresh and frozen semen on accessory sperm number, fertility and embryo quality in artificially inseminated cattle
    Nadir, Sher (Virginia Tech, 1992)
    This study was designed to : 1) Determine the effects of fresh vs frozen semen at a high inseminate dosage (lOOxl06sperm) contrasted to their effects at a conventional dosage (20xl06 sperm) on accessory sperm per ovum and 2) Evaluate the relationship between accessory sperm number per embry%vum and fertilization status/embryo quality if accessory sperm number were affected by treatment. In this study semen from four bulls routinely giving a minimum of 700/0 morphologically normal and 600/0 motile sperm cells were used. Ejaculates of these bulls were split and prepared for use as fresh and frozen semen at either 100xl06 or 20xI06 cells per dose in.5 mL French straws. Half of the total semen filled straws were frozen in liquid nitrogen at -196°C and half were stored at 5°C for 4 days after collection and used as unfrozen. Cows in standing heat were inseminated with fresh or frozen semen at either high (IOOxl06 sperm) or conventional dose (20xl06 sperm). Ova/embryos were recovered non surgically on day 6 after breeding. Accessory sperm were counted in the recovered embryos/ova after partial digestion with Pronase followed by compression of the embryo/ovum with a cover slip. From 129 inseminations to normally cycling cows, 98 embryos/ova were recovered. To reduce male effects, embryos/ova used were randomly balanced across treatments, by ejaculate within bull for evaluation of frozen vs fresh semen (n = SO) and by bull for evaluation of high vs low dosage treatments (n = 76). No difference (P > 0.05) in accessory sperm was observed for fresh vs frozen semen at either the high or low dosage. The mean accessory sperm values for fresh high dose (n=21), frozen high dose (n=21), fresh low dose (n= 19), and frozen low dose (n= 19) were 26.S1±30.23 (SD), 36.05±44.74 (SD), 29.37± 55.97 (SD) and 30.l6± 70.18 (SD) respectively. When data for embryos/ova resulting from fresh and frozen semen were pooled within dosage, a significant difference was observed between the median accessory sperm values for high and low doses of semen (P < .05). Mean ± SD and median values for accessory sperm were: 37.8± 38.3 and 27.5; 28.9± 62.8 and 3.0, for the high and low dose, respectively. Increasing accessory sperm number by the higher dosage improved the fertilization status/embryo quality (P < .05). Percentage unfertilized ova, degenerate embryos and embryos classified poor to fair and good to excellent were: 3, 5, 24, 68; and 21, 16, 18, 45, for the high and low dose, respectively. Overall, embryos/ova classified good to excellent, poor to fair, degenerate and unfertilized had median accessory sperm values of 18, 9.5, 5.5 and 0, respectively. However, the lack of accessory sperm in unfertilized ova was significantly different from excellent-good quality embryos (P < .05).
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    Effect of seminal plasma on cryopreservation and function of bovine spermatozoa
    Nadir, Sher (Virginia Tech, 1995)
    This study was conducted to :1) determine the effect of seminal plasma (SP) on sperm viability parameters (estimated percent motile sperm, computer-aided percent motile sperm and percent intact acrosomes) and motion characteristics (average path velocity, VAP; curvilinear velocity, VCL; and straight line velocity, VSL) of cryopreserved ejaculated spermatozoa (Experiment 1) and cauda epididymal spermatozoa, both fresh and frozen (Experiment 2).2) determine the effect of additional SP on sperm transport in the female using cryopreserved ejaculated sperm (Experiment 3) or cryopreserved cauda epididymal sperm (Experiment 4). In Experiment I, addition of SP (1:1, v/v, post-thaw) did not affect (P> .05) viability parameters; however, all sperm motion characteristics were improved at 3 h of incubation (P < .05). In Experiment 2, addition of a normal complement of SP to cauda epididymal sperm significantly improved all motion characteristics and viability parameters except acrosomal integrity (P < .05) and semen freezing did not alter this effect. In Experiment 3 and 4, addition of SP to the inseminate did not affect the mean or median accessory sperm number (P> .05); however, in both experiments there was a trend toward increased median accessory sperm values for the SP-treated semen. In Experiment 3, mean ± SD and median accessory sperm values per embryo/ovum were 19.2± 36.9 and 2.5 for the control (n = 32); and 23.1 ± 71.6 and 6.5 for the treatment (n = 32). In Experiment 4, mean± SD and median accessory sperm values per embry%vum were 9.2± 16.7 and 1.0 for the control (n = 30); and 14.2± 21.2 and 3.5 for the treatment (n = 30). We conclude from these experiments that sperm motion characteristics but not viability parameters of ejaculated frozen-thawed semen are improved by additional SP (Experiment 1) and both motility and motion characteristics are modestly improved by a normal complement of SP added to cauda epididymal sperm (Experiment 2). This positive effect of SP on motility/motion characteristics may favor sperm transport, but not at a statistically significant level to be detected by accessory sperm number.
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    Effect of Timing of Insemination and Synchronization of Estrus Method on Artificial Insemination (AI) Pregnancy Rates in Beef Heifers
    Dorsey, Benjamin Reese (Virginia Tech, 2005-04-25)
    Objectives were to evaluate time of insemination relative to estrus and synchronization with melengestrol acetate (MGA) plus prostaglandin (PG) or progesterone insert (CIDR) plus PG on AI pregnancy rate in beef heifers (n = 662) during Fall or Spring. Fall heifers (n = 349) received MGA-PG (MGA for 14 d followed by PG on d 18) or CIDR-PG (CIDR for 7 d, PG administered 1 d before CIDR removal). Estrus was monitored by HeatWatch® (n = 200) or visually (n = 149). Spring heifers (n = 313) underwent CIDR-PG with detection of estrus by HeatWatch®. Heifers not in estrus by 96-100 h after PG were bred AI as non-responsive AI (NRAI). Across seasons, 548 heifers were bred following estrus (EAI). Heifers synchronized during the Fall with MGA received more (P < 0.05) mounts than Fall CIDR heifers (76.8 ± 6.7 and 47.6 ± 7.4, respectively), but duration of estrus was similar. Fall CIDR heifers had greater (P < 0.05) mounting activity and duration of estrus (47.9 ± 5.2 mounts and 15.5 ± 1.1 h) compared to Spring CIDR heifers (34.5 ± 3.1 mounts and 12.7 ± 0.6 h). Heifers grouped in 4 h blocks from 0 to 24 h had no difference (P > 0.05) in pregnancy rates (mean 62.5 %). Treatment had no effect (P > 0.05) on EAI pregnancy rates. Pregnancy rates across seasons for EAI, NRAI and overall was 61.0 %, 26.3 %, and 54.5%. In conclusion, a 24 h window may exist to successfully AI heifers.
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    The effects of sperm dose, semen quality, and retrograde sperm blockage on accessory sperm number and embryo quality in the artificially inseminated bovine
    DeJarnette, James Melton (Virginia Tech, 1990-07-15)
    This study was designed to: 1. Determine the effects of sperm dose and retrograde sperm blockage on mean number accessory sperm/ova. 2. Evaluate the relationship between mean number accessory sperm/ova and fertilization status/embryo quality. 3. Determine if mean number accessory sperm/ova or embryo quality are affected by semen quality. 4. Compare the percentage of morphologically normal accessory sperm with the percentage of normal cells in the inseminate. Using excised reproductive tracts, a French insemination rod housed in a 24-gauge Foley catheter was determined to be effective in blocking retrograde flow of semen following insemination. In a preliminary study, blocked vs conventional inseminations (control) were made using average quality frozen semen at 20 x 10⁶ sperm/dose. Although not different (P > .1), the mean number accessory sperm/ovum was 20 ± 40 (n= 24) and 13 ± 28 (n= 26) for the blocked and control methods, respectively. In Expt. 1, the conventional (control) and blocked system were again compared in a 2x2 factorial using low quality semen at 20 and 40 x 10⁶ sperm/dose. Mean number accessory sperm/ova was not affected by dose, blocking, nor the interaction. Embryo quality was negatively affected by blocking (P < .1), and unaffected by sperm dose. In Expt. 2, embryo quality and accessory sperm numbers were unaffected by a 40 x 10⁶ sperm dose of either average or below average quality semen. However, embryo quality tended to be improved by the average quality semen. Accessory sperm were significantly enriched with morphologically normal cells when compared with those in the inseminate (P < .01). Viable quality embryos (poor thru excellent) had the highest mean number accessory sperm/ovum (16.2 ± 28.9), most unfertilized ova (UFO) contained zero accessory sperm (.27 ± .83) and degenerates embryos were intermediate in number (5.4 ± 8.7). The relationship between embryo quality and accessory sperm number appears to vary in response to semen quality.
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    The effects of the cervix on the transport of morphologically abnormal spermatozoa in the female bovine
    Karabinus, David Scott (Virginia Polytechnic Institute and State University, 1988)
    Two studies were conducted to investigate the role of the bovine cervix in filtering abnormal sperm. ln Study 1, semen containing high levels of abnormal sperm was vaginally deposited in 12 cows 80 hours after prostaglandin F₂α treatment. At slaughter, 4-, 8- or 12 hours post-insemination, sperm were flushed from the excised uteri with fixative. Pooled across times post-insemination, viability was greater for uterine vs inseminate sperm, based upon vital smears prepared from inseminate and uterine flush samples. Uterine levels of normal sperm, determined by differential interference contrast (DIC) microscopy, were greater than were inseminated. In Study 2, heifers were estrus synchronized in pairs using prostaglandin F₂α, then inseminated with semen containing high levels of abnormal sperm. In each pair, semen of high viability (Experiment 1, n=10) or low viability (Experiment 2, n=6) was deposited vaginally in one heifer and within the uterine corpus of the other. Using DIC microscopy, viability and morphology were coincidentally determined for sperm in samples from the fixed inseminate and the retrograde mucus, vaginal mucus, cervix, uterus and in vitro incubation of inseminate recovered and fixed 12 hours post-insemination. Uterine sperm quality did not differ between insemination sites, except lower uterine levels of live abnormal sperm alter intrauterine vs vaginal insemination of low viability semen probably due to disproportionately low viability of one abnormality. Sperm viability was enhanced and morphology unchanged in the uterus vs low viability inseminate, while sperm viability was unchanged and abnormal sperm subtly reduced in uterus vs high viability inseminate. Greater levels of live and live normal sperm were found deeper between cervical folds than at apical aspects of folds. Vaginal mucus sperm viability was lower compared to other tract locations and inseminate, especially after high viability insemination. Compared to inseminate viability, retrograde mucus sperm viability was high after vaginal insemination and low alter intrauterine insemination. Differential death of abnormal vs normal sperm neither with incubation of insemination in vitro nor, presumably, in vivo. Results show little evidence of cervical filtration based upon sperm morphology. Sperm retention in the female tract was predominantly related to sperm viability with only very subtle morphology effects.
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    The effects of varying the interval from follicular wave emergence to progestin withdrawal on follicular dynamics and the synchrony of estrus in beef cattle
    Utt, Matthew Douglas (Virginia Tech, 2002-06-07)
    The objective of this experiment was to examine the effects of varying the interval from follicular wave emergence to progestin removal on follicular dynamics and the synchrony of estrus. The experimental design was a 2x2x2 factorial with GnRH or estradiol-17 beta (E2) + progesterone (P4), controlled internal drug-releasing device (CIDR) treatment duration, and PG or saline treatment as main effects. Cycling, Angus cows (n=49), on d 6 to 8 of the estrous cycle, were randomly assigned to receive a CIDR treatment for 7 or 9 d. Approximately half of the cows from each CIDR group received either GnRH (100 mcg) or E2+P4 (1 mg E2 + 100 mg P4) at CIDR insertion. Cows in GnRH or E2+P4 groups were further divided into those that received PG (37.5 mg) or saline at CIDR insertion. All cows received PG (25 mg) 1 d prior to CIDR removal. The interval from follicular wave emergence to CIDR removal was longer for cows treated with GnRH (6.6 d) or a CIDR for 9 d (6.5 d) compared to those treated with E2+P4 (4.7 d) or a 7-d CIDR (4.8 d) (P < 0.05). Cows treated with PG or GnRH at CIDR insertion or a 9-d CIDR had a larger dominant follicle (DF) at CIDR removal than those treated with saline, E2+P4, or a 7-d CIDR. (P < 0.07). Altering the interval from wave emergence to progestin removal created differences in size of the DF at CIDR removal but did not affect the synchrony of estrus.
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    Estimation of the Economic Impact of a Unit Change in Predicted Transmitting Ability for Daughter Pregnancy Rate and Other Predicted Transmitting Ability in the Merit Indexes
    Yook, Eunsun (Virginia Tech, 2004-04-28)
    These studies deal with lifetime profit analyses for individual cows, and using these estimates to determine the economic value of genetic changes in traits for which genetic evaluations (predicted transmitting ability, PTA) are currently available. Data were collected from six states processed by Dairy Records Management Systems (DRMS) from herds on continuous test for at least 10 yr. The purpose of the first study was to determine how well estimators of lifetime net income based on 305-d lactation yields and a 10-yr opportunity (RNI305.10) and based on complete lactation data but a 5-yr opportunity (RNIc.5) predict the estimate based on complete lactations and a 10-yr opportunity (RNIc.10). Records for 22,854 cows in Virginia herds born in 1988, 1990, and 1992 from the DRMS in Raleigh, NC were used. Each RNI was calculated using fluid (skim/fat) pricing and milk-fat-protein pricing. Regression analyses including herd and birth year were used in the model to estimate the regression of RNIc.10 on RNIc.5, and RNIc.10 on RNI305.10. The resulting regression coefficients for fluid (skim/fat) pricing were $1.53 and $1.12 explaining 67 and 97% of the variation of RNIc.10, respectively. The corresponding results for milk-fat-protein pricing were $1.52 and $1.14 explaining 68 and 96% of the variation of RNIc.10, respectively. Using RNIc.10 as the measure to estimate lifetime profit is strongly recommended over the two alternatives tested. In the second study, the economic impacts of a unit change in PTA of daughter pregnancy rate (DPR) and other PTA in the merit indexes on lifetime profit estimates of a bull's daughters were estimated to determine an economic weight for the PTADPR and other PTA in economic indexes. Records for 71,094 cows born in 1988, 1990, and 1992 from six states processed at DRMS were used: Florida [10,940 cows], Indiana [8,231 cows], North Carolina [12,280 cows], Texas [4,786 cows], Virginia [20,341 cows], and Vermont [14,516 cows]. The basic RNI function consisted of [total milk, fat, and protein income ?feed cost for production] (yield income, YI) + [net value of calves + net salvage value] (non yield income, NYI) ?rearing cost (RC) ?[(daily cost for labor, maintenance feed, supplies, and fixed expenses) x days in herd] (daily cost, DC). Some of the economic impacts of PTA described for the merit indexes were not included in the basic RNI. These were added to RNI by multiplying the respective sire PTA by the economic impact. These included -165*PTASCS (M); 33*udder composite + 15*feet and legs composite -14.86*body size composite (T); and 8.064*PTA for daughter pregnancy rate -4.80*PTA for daughter calving ease (PRCE). Each ARNI was calculated using all production records initiated prior to the cow's tenth birthday with three milk pricing systems comparable to the prices in USDA three merit indexes: fluid (skim/fat) pricing (FARNI), milk-fat-protein pricing (NMARNI), and cheese pricing (CARNI). Two levels of prices for rearing cost per day and daily cost were used for calculating FARNI, NMARNI, and CARNI. Regression analyses including herd and birth year in the model were used to estimate the simple and partial regressions of ARNI or partitioned ARNI on sire PTA. Partial regression included all PTA in Net Merit, except service sire calving ease. Ignoring other PTA, one unit increase in PTADPR increased 476.25kg of lifetime total milk or 18 days of total DIM. One unit decrease in PTASCS increased 4372.50kg of lifetime total milk. With low daily and rearing costs, each 1% change in PTADPR increased ARNI by $59.31 to $55.82 depending on the milk pricing systems. The corresponding results with high daily and rearing costs were $27.50 to $24.01. Standardized multiple regression enabled the comparison of the economic weights of this study with those of USDA. The PTA for productive life (PL) in all three USDA merit index was emphasized less than the results from this study; however, PTADPR in USDA indexes was emphasized more than this study. In this study, the economic weight of PTADPR was negative within the low daily and rearing costs, but it was positive in the high daily and rearing costs.
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    Evaluation of 72 h Cosynch and 5 or 7 d post-AI gonadotropin releasing hormone on first service pregnancy rate in lactating dairy cows
    Mink, Matthew Ryan (Virginia Tech, 2006-05-09)
    Two studies were conducted to evaluate the effects of 5 or 7 d post-AI GnRH on first service PR, plasma P4, and CL volume in lactating dairy cows synchronized using 72 h Cosynch. All cows were synchronized and randomly assigned to one of three treatment groups: Control – no additional GnRH; 5 d – GnRH 5 d after TAI; 7 d – GnRH 7 d after TAI. In the first study, P4 concentrations were evaluated in samples collected at five separate times and CL volume and number were recorded at 30 d pregnancy examination for Holstein (n = 77) and Jersey (n = 33) cows. GnRH treatment did not affect PR (Control - 47.2%, 5 d GnRH - 40.5%, 7 d GnRH – 44.7%) or P4, but increased TCLV compared to controls (Control – 7.33 cm3, 5 and 7 d GnRH – 10.77 cm3). Incidence of accessory CL increased PR (94.7 vs. 60.6%), P4 (6.95 vs. 5.88 ng/mL), and TCLV (15.51 vs. 6.78 cm3) compared to cows with a spontaneous CL. Cows classified as cycling based on P4 evaluation had significantly higher PR than acyclic cows (54.4 vs. 16.1%). In the second study, Holstein cows (n = 1055) were submitted to the same experimental protocol and evaluated for first service PR. Post-AI GnRH treatment did not significantly affect PR. Primiparous cows (32.8%) tended to have higher PR than multiparous cows (27.6%), but GnRH treatment had no influence on this relationship. In conclusion, GnRH post-AI did not affect PR. Further evaluation of accessory CL incidence is warranted as it significantly affected PR. (Abbreviations: AI – artificial insemination, CL – corpus luteum, PR – conception rate, P4 – progesterone, TCLV – total corpus luteum volume)
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    Evaluation of systematic breeding programs in lactating dairy cows
    Jobst, Shelly Marie (Virginia Tech, 1998-11-04)
    Observing cows in estrus and inseminating them at the optimal time are necessary steps for effective reproductive management of a dairy herd. However, increasing herd sizes can lead to reproductive inefficiency resulting in decreased profits on dairy herds. Synchronization of estrus, through pharmacological control, has been used to improve reproductive efficiency. Systematic breeding programs provide an organized approach for administering artificial insemination (AI) at first service. Moreover, reproductive management is based on a methodical approach for the entire herd rather than for the individual cow. Seven-hundred and thirty four Holstein cows from 16 commercial dairy herds were used to conduct this study evaluating three systematic breeding protocols; 14-d PGF2a, timed AI (TAI), and GnRH-PGF2α, in comparison with an untreated control group. Eight herds relied on visual observation as their primary method for detection of estrus, and 8 herds utilized the HeatWatch® (DDx, Inc., Denver, CO) electronic estrus detection system. The average days to first postpartum AI were longer for untreated control cows when compared to the other breeding protocols. First AI conception rates did not differ among control, 14-d PGF2a, or GnRH-PGF2a protocols, but were higher than the TAI protocol. However, first AI pregnancy rates were higher for untreated controls versus hormonally treated cows. Estrus characteristics associated with each protocol were also evaluated and no difference was detected across treatments. An economic analysis determining cost per pregnancy for each protocol when considering drug costs, and pregnancy rates, resulted in the highest cost per pregnancy for TAI followed by GnRH-PGF2a and 14-d PGF2a. These programs should be considered as tools for convenience and efficiency of estrus detection; however, reduced labor costs from less time spent on estrus detection may be offset by the cost of the drug protocols. Cost effectiveness must be calculated on an individual herd basis when deciding whether a systematic breeding program is the appropriate choice.
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    Factors affecting the efficiency of gene transfer in mice
    Canseco-Sedano, Rodolfo (Virginia Tech, 1992-10-11)
    In order to optimize the overall efficiency of pronuclear microinjection, we designed experiments to: 1) test the best developmental stage for transferring injected embryos to obtain pregnancies and transgenic pups; 2) determine the optimum number of injected embryos transferred to obtain pregnancies and transgenic pups; 3) investigate whether addition of non-injected embryos with injected embryos increased pregnancy rate (PR) and transgenic pups; and 4) establish the time during pregnancy of highest embryonic or fetal loss. Mice (CD1; 3 to 4 wk old), were superovulated with 10 iu PMSG and 5 iu hCG 48 h apart. One-cell embryos were collected for microinjection 20 to 24 h after hCG. The gene used was the whey acidic protein promoter linked to a coding sequence of the human protein C gene (WAP-hPC). Embryos were cultured in CZB at 37°C in 5% CO₂ in air. All the live pups born and embryos and fetuses recovered were analyzed by the polymerase chain reaction to detect the presence of the transgene. Experiment one consisted of nine transfer treatments (TRT) which included all the combinations of three developmental stages (1-cell, 2-4 cell and morula/blastocyst) with three quantities of embryos per transfer (15-24, 25-34 and 35-44). Ten transfers were performed for each TRT. The highest PR and total pups born (TOTP) were obtained after transferring 25 to 34 2-4 cell embryos (PR=90% TOTP=3.5/ pregnancy). However, overall analysis indicated that the percentage of transgenic pups born (%TRS) was highest using 1-cell embryos [33.9%, 20.0% and 11.1% for 1-cell, 2-4 cell and morula/blastocyst (mor/bl), respectively]. The second experiment consisted of six transfer TRT: 20-0, 16-4, 12-8,30-0, 26-4, and 22-8 injected - non-injected embryos, respectively (10 transfers/TRT). Data showed that PR and TOTP can be improved by addition of non-injected embryos. However, the percentage of transgenic pups was significantly (p< .05) higher when all the embryos transferred were injected (53.6 % vs 46.4 % for transfers without and with non-manipulated embryos, respectively). Additionally, 30 embryos per transfer yielded a significantly higher percentage (p< .05) of transgenic pups than 20 embryos per transfer (67.9 % vs 32.1 % for 30 and 20 embryos per transfer, respectively). In experiment three 45 transfers of microinjected embryos were performed (30 embryos per transfer). Fifteen recipients were sacrificed on day 4, 12, and 18 of gestation. On each day all embryos and fetuses were counted and analyzed for the presence of the transgene. The percentage of transgenic embryos or fetuses was not statistically different at any recovery day (45.8%, 35.5%, and 34.6% for days 4, 12, and 18, respectively). However, the number of viable embryos at day 4 was significantly greater than the number of viable fetuses on days 12 or 18 (10 ± 1.1,,5.1 ± 1.6, and 2.4 ± 1.3 for days 4,,12 and 18, respectively). Collectively, the results indicate that: 1) transfer of 20 to 30 1-cell embryos was the best method to obtain transgenic mice, 2) addition of non-injected embryos decreased the number of transgenic pups obtained per pregnancy, and 3) although most of the embryonic losses after microinjection happen before day 4 of gestation, additional losses occurred between days 4 and 18 of pregnancy.
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    Factors Important to the Efficiency of Artificial Insemination in Single-Ovulating and Superovulated Cattle
    Dalton, Joseph C. (Virginia Tech, 1999-04-09)
    To identify factors important to the efficiency of artificial insemination in cattle, four studies were conducted. In the first study, the addition of cream to the inseminate was used in an attempt to increase accessory sperm number. On d 6 after insemination, 60 embryos were evaluated. The addition of cream to the inseminate had no effect on accessory sperm number. In the second study, cryopreserved semen of a marked bull (spermatozoa exhibiting a semi-flattened anterior head) was matched with semen from an unmarked bull (conventional sperm head shape) to determine competitively the effect of a deep uterine insemination on accessory sperm number. Forty embryos were recovered 6 d after insemination and the ratio of accessory sperm observed was different: 62:38 for unmarked semen in the uterine body and marked semen in the uterine horn, and 72:28 for unmarked semen in the uterine horn and marked semen in the uterine body (P < .05). In the third study, superovulated cows were utilized to determine the effect of artificial insemination time on fertilization status and accessory sperm number. Cows were inseminated once at 0 h (n=10), 12 h (n=10), or 24 h (n=10) after the first standing event. On d 6 after insemination, 529 embryos(ova) were recovered. Fertilization rates were 29% (0 h); 60% (12 h); and 81% (24 h)(P < .01). Percentages of embryos with accessory sperm were: 5 (0 h); 8 (12 h); and 41(24 h) (P < .01). In the fourth study, three experiments utilizing superovulated cows were conducted to provide a basis for distinguishing unfertilized ova from very early embryonic death. In Exp. 1, recovered d 6 unfertilized ova were classified morphologically as either: 1) typical, 2) satellite, or 3) fragmented. In Exp. 2, recovered d 6 unfertilized ova from the third study were classified morphologically, and typical ova were fixed. In Exp. 3, ultrastructural features of preovulatory, tubal-stage, and typical d 6 unfertilized ova were investigated. Preovulatory ova revealed normal ultrastructure; tubal-stage ova exhibited evidence of degeneration; typical d 6 ova were degenerated and contained no discernable organelles. The first three studies support the use of accessory sperm evaluation as an alternative measure of fertility. The final study provides a basis from which future embryologists may distinguish fertilization failure from very early embryonic death.
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    Hormonal regulation of the onset of puberty in purebred and crossbred Holstein and Jersey heifers
    Getzewich, Karen Elizabeth (Virginia Tech, 2005-07-19)
    The objective of this study was to determine the onset of puberty by using progesterone profiles and anterior pituitary gonadotropin releasing hormone (GnRH) challenges in purebred and crossbred Holstein and Jersey heifers. In experiment 1, fifty prepubertal heifers by four sire - dam classifications (18 HH, 11 JJ, 10 JH, and 11 HJ) were used. The HH heifers attained puberty at an older age than the HJ, JH or JJ heifers, and these three classifications were not different from each other. There were significant differences in weight and wither height at puberty and average daily weight gain (ADWG) between all four sire - dam classifications. Season of birth had a significant effect on age and weight at puberty. In experiment 2, four prepubertal heifers from each sire - dam classification in experiment 1 were used at 3, 6, 9 and 12 mo of age to determine the effects of administering 200 μg GnRH on LH secretion. The effects of breed, age at challenge, and their interaction were only significant for time to LH peak. In conclusion, age at puberty in crossbred Holstein X Jersey heifers is regulated by breed and season of birth, and further research with larger sample sizes is needed to establish the relationship of pituitary maturation and the capacity to secrete LH in response to GnRH stimulation as related to onset of puberty in purebred and crossbred dairy heifers.