Browsing by Author "Scott Whisnant, Committee Member"

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    The Development of a Streptoccocus uberis mastitis Challenge Protocol
    (2007-03-11) Tillman, Warren Scott; Peter Farin, Committee Member; Kevin Anderson, Committee Member; Mitchell Hockett, Committee Chair; Scott Whisnant, Committee Member
    A series of experiments was conducted using a S. uberis bacterial isolate in order to produce a predictable and effective protocol for experimental induction of mastitis. A bacterial isolate was obtained from a clinical mastitis infection in a local, North Carolina dairy herd. In vitro growth of the bacterial isolate produced a predicted lag, log, stationary, and death phase. Comparison of optical absorbance values to bacterial concentrations resulted in a Pearson's correlation coefficient of 0.71. It was determined that time of growth would be a better indicator of bacterial concentration. S. uberis isolates were incubated for 3 hours of growth and placed on ice to observe temporal changes in bacterial concentration. Bacterial concentration did not differ over time (P=0.96), indicating that ice storage maintained S. uberis concentrations for 3 hours. S. uberis bacterial concentrations deviated from predicted values in growth curves, so an alteration to the serial dilution protocol was performed in order to reach the desired concentration. Four Holstein cows were challenged with 5, 400 cfu of S. uberis in 2 quarters that contained no mastitis pathogens and were compared to 4 Holstein control cows. The inoculum concentration produced a 100% incidence of clinical infection in all quarters challenged. The challenged group exhibited elevated quarter milk scores, quarter pain scores, attitude scores, and quarter size scores, with first clinical signs occurring at 36 hours. Rectal temperatures were highest at 36 hours (40.5 ± .3 o C vs. 38.5 ± .3 o C; P<0 .0001) (mean ± SEM) compared to control. Challenged quarter somatic cell counts (SCC) were elevated at 24 hours post-infusion in comparison to control quarter SCC at 0 (Challenge 24: 3.5 X 106 ± 5.6 X 106 vs. Control 0: 4.3 X 104 ± 3.1 X 104; P < 0.0001) and 24 hours (Challenge 24: 3.5 X 106 ± 5.6 X 106 vs. Control 24: 6.7 X 104 ± 5.0 X 104; P = 0.003). Challenge quarter SCC at 24 hours also differed from challenge SCC values at time of challenge (Challenge 24: 3.5 X 106 ± 5.6 X 106 vs. Challenge 0: 1.4 X 105 ± 2.1 X 105; P < 0.0001). While a predictable mastitis model was acquired using 5,400 cfu, the response in challenged cows was more severe than preferred. In the attempt to obtain a clinical infection that was physiologically more benign (low-grade pyrexia, less severe quarter abnormalities, and faster response to treatment), it was determined that lower doses might still produce a high incidence of clinical infection while presenting less severe clinical signs. In this trial, 500 cfu (low dose; n=6 quarters in 3 cows), 1,950 cfu (medium dose; n=5 quarters in 3 cows), and 4,000 cfu (high dose; n=6 quarters in 3 cows) were inoculated into quarters that contained no intramammary pathogens. All cows (n=9) and 13⁄17 (76.5%) quarters developed a clinical infection. Regardless of dose, an overall elevation in SCC from baseline values was reported following challenge (P < 0.0001). SCC was found to be elevated in the high dose group on day 2, and in both the medium and high dose group on days 3 and 4 (P < .05). The low dose tended to be elevated 2 days post challenge (P < 0.1). Regardless of dose, peak rectal temperature after challenge (39.8 ± .2 ◦C) was higher (P = 0.03) than initial rectal temperature (39.1 ± .1 ◦C). Milk score, quarter pain score, quarter size score, attitude score, and appetite score were elevated following challenge for each dose. Udder temperature was elevated only in the low group (P < .05). Serum levels of IL-1β, TNF-α, and IL-8 were not elevated during the sampling period. Five hundred cfu of this S. uberis strain produced a predictable clinical infection in challenged cows. Therefore, higher doses would not be needed to produce mastitis.
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    Effect of GnRH compared to Estradiol-17-Beta at beginning of Superovulation Protocol on Superovulatory Response and Embryo Quality
    (2008-07-24) Wock, Jillene Marie; Mitchell Hockett, Committee Chair; Scott Whisnant, Committee Member; William Flowers, Committee Member; Charlotte Farin, Committee Member
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    Ovulatory and Reproductive Characteristics of Sows Treated with an Intravaginal GNRH Agonist Gel
    (2005-03-01) Roski, Kara Howes; Glen Almond, Committee Member; Scott Whisnant, Committee Member; William Flowers, Committee Chair; Mitchell Hockett, Committee Member
    This study was designed to test the reproductive and ovulatory characteristics of sows treated with Ovugel® (EIEICO, Radnor, PA), a gel containing a GnRH agonist (Triptorelin) administered intravaginally. The treatment groups received 100μg of GnRH agonist intravaginally in varying viscosities of the gel, .6%(n=12), .9%(n=12), 1.2%(n=12), and 1.5%(n=12) respectively. A positive control group (n=11) received saline containing 100μg of GnRH agonist while the control sows (n=12) received a vehicle of the 1.2% gel and at 96h post weaning. Jugular cannulas were placed 48 hours before administration of the treatment. Blood samples were taken every 6 hours before treatment, then every 2 hours for the first 12 hours after treatment, then every 6 hours for the next 18 hours. Estrus detection occurred every 6 hours through the entire study. Real time ultrasonography was conducted every 4 hours to determine the time of ovulation. Control sows were bred based on the onset of estrus and treatment sows were bred at +8 and +32 h after the gel was administered. All data was analyzed using SAS and the proc GLM procedure. Treatment Saline + GnRH Control 0.6% + GnRH 0.9% + GnRh 1.2% + GnRH 1.5% + GnRH Ovulation time (h) 46.5±1.2 43.8±5.4 43.8±2.0 41.2±3.3 43.5±1.8 44.5±1.5 Estrus length (h) 45.8±3.4 45.6±3.8 49.0±3.8 47±3.2 46.9±3.9 55.1±3.9 LH surge (0-30h post treatment) 7/10 5/8 7/10 9/11 8/10 8/9 Farrowing Rate 8/8 9/9 11/12 10/12 11/12 10/11 Litter Size 12.9±0.7 9±3.1.2 11±1.3 11.6±1.0 11±0.5 10.6±1.4 There were no differences in treatments in ovulation time from the onset of estrus or administration of Ovugel® (p=0.28), estrus length (p=.60), farrowing rate (p=0.80), litter size (p=0.35), or LH surge (p=0.49). However, variation associated with ovulation time was significantly reduced (p=0.01) for saline, 1.2%, and 1.5% treatments compared with controls. The duration of estrus was greater for the 1.5% gel with the triptorelin than the sows receiving only the 1.2% gel (p=0.04). The intravaginal absorption of GnRH in Ovugel® or saline along with a timed insemination program is an effective method to reduce the interval over which ovulation occurs without overtly decreasing fertility. KEY WORDS: ovulation, GnRH agonist, swine