Biomedical subjects

R W Everett

Publications and source records attributed to R W Everett.

28 records · Page 2Linked to original sources

PubMed1982

Effect of Dursban 44 on semen output of Holstein bulls.

Dursban 44, an insecticide for lice control, was applied to 185 Holstein bulls 9 to 52 mo of age. These sires were in various stages of progeny testing at an artificial insemination center. Application of this product killed 7 bulls, and the remaining bulls exhibited varying severity of illness with 6 classified as very sick. This study evaluated the effect of this illness on semen production. Semen output on 40,950 ejaculates from 583 Holstein bulls collected from July 1, 1975, through March 31, 1981, was analyzed to establish normal semen production and to estimate the effect of illness caused by Dursban 44 treatment. Ejaculate number, days between collections by previous number of ejaculates, calendar months, years, and ages of bulls affected the semen output characteristics, original volume, sperm concentration, percent motile sperm, total sperm per ejaculate, percent prefreeze discards, percent postthaw sperm motility, and percent postthaw discards. Ejaculate volume, motility, total percent prefreeze discards, and percent postthaw discards were influenced negatively on the 6 very sick bulls. Percent postthaw discards were higher on all bulls treated with Dursban 44 for up to 6 mo post-treatment.

Animals↗

PubMed1982

Comparison of first lactations and all lactations of dams to predict sons' milk evaluations.

Multiple regression of genetic evaluations of about 170 Holstein bulls on sire, dam, and maternal grandsire genetic evaluations indicated that the partial regression coefficient for the sire is similar to the theoretical regression coefficient (.45 vs. .50), that the regression coefficient for the dam is much smaller than the theoretical regression coefficient when all records of the dam including her first are included in her evaluation (.12 vs. .35), although about as expected when only first records of the cow and her herdmates are used (.33 vs. .35), and that the regression for the maternal grandsire is larger than expected when his proof and all records of the dam are used in her evaluation (.07 vs. .00), although about as expected when his proof and only her first record is used (-.02 vs. .00). Preferential treatment of potential bull dams is a possible explanation for these results. Genetic correlations among lactations are not likely to be small enough to account for the differences in regression coefficients for the dam's genetic evaluations for all and first lactations. If conditions for selecting bull dams in the future will be similar to what they have been in the past, the conclusion is that genetic evaluations of cows from their first lactation records be used in preference to genetic evaluations from all lactation records for selection of dams of bulls.

Animals↗

PubMed1981

The relationships between energy balance, milk production and ovulation in postpartum Holstein cows.

Energy balance and serum progesterone concentrations were monitored during early lactation in a group of high producing Holstein cows. The postpartum interval to normal ovulation averaged 36 +/- 6 days (range 6 to 83 days). Average energy balance during the first 20 days of lactation (cumulative daily calculated energy balance divided by days in milk) was inversely related to days to normal ovulation (r = -.60) and to milk production (r = -.80). Milk yield during this period was not closely related to days to ovulation (r = .30). Milk yield was also not significantly related to serum prolactin concentrations over the first 12 weeks of lactation (r = .27). During early lactation, energy balance was maximally negative until peak milk yield and then began returning toward zero, with the magnitude and duration of negative energy balance being quite variable. On the average, ovulation and the initiation of the first normal luteal phase occurred approximately 10 days after energy balance began returning toward zero. During this 10-day interval, a transient elevation in serum progesterone concentrations occurred in eight of 13 cows. These results suggest that energy balance during the first 20 days of lactation is important in determining the onset of ovarian activity following parturition.

Animals↗

PubMed1981

Effect of adrenocorticotropin on milk and plasma cortisol and prolactin concentrations.

Milk cortisol and prolactin concentrations were measured in 12 lactating Holstein cows for 3 days (Experiment 1). On day 3, cows were divided randomly into groups: IV1, IV4, IM, and control. Group IV1 received one intravenous injection of 49 IU adrenocorticotropin, group IV4 the same dosage four times at 2-h intervals, group IM 240 IU adrenocorticotropin intramuscularly, and control cows were injected with saline. Cortisol concentrations in blood plasma were increased in all groups following adrenocorticotropin injection, while milk cortisol concentrations increased fourfold in groups IV4 and IM and remained unchanged in group IV1. In Experiment 2, infusion of 18% saline into the mammary gland of three cows increased the somatic cell count in the infused quarter but had no effect on prolactin and cortisol of milk or plasma. In Experiment 3, six cows each were assigned to treatment groups of saline controls, IV2-0 (40 IU adrenocorticotropin intravenously at 0 and 2 h post-milking) or IV2-8 (40 IU adrenocorticotropin intravenously at 8 and 10 h post-milking). Half udders of each cow were milked before treatment and 4 h later. Increases of cortisol in plasma increased cortisol concentrations of milk 4 h after each treatment (IV2-0 and IV2-8). However, by 12 h after treatment in IV2-0 cortisol concentrations of milk had returned to normal. Increases in adrenal cortisol secretion are followed rapidly (within 4 h) by increased cortisol concentrations in milk. However, these decline rapidly in the absence of sustained increments in blood cortisol. Increased cortisol concentrations in milk most likely represent sustained elevation in plasma cortisol.

Adrenocorticotropic Hormone↗

PubMed1978

Sources of variation of semen output.

Data from 5033 ejaculates during 1 yr from 55 mature Holstein bulls were analyzed to determine the effects of ejaculate number, days between ejaculates, month of the year, solunar periods, and sires on spermatozoal output and seminal characteristics. First ejaculates contained 49.7% more sperm and 40.8% more sperm per ml than second ejaculates. Increasing the interval between collections from 2 to 6+ days resulted in 45.9% more sperm per ejaculate, 31.0% more sperm per ml. and 14.0% greater volume. However, daily sperm output was highest when bulls were ejaculated most frequently. Lowest semen output was in February and March, associated with a decrease in sperm per ml. Highest semen output was in April and June, associated with the highest concentration of sperm per ml. Solunar periods had no effect on any measure of semen output. The concentration of sperm per ml varied more than the volume per ejaculate and had the largest influence on variation in total sperm harvested per ejaculate. Frequency of ejaculation was a major factor in total sperm harvested per bull per year.

Animals↗

PubMed1975

Effect of drying off practices on mastitis infection.

Two methods of drying off cows, intermittent milking and abrupt cessation, were studied with data from 9254 quarters of cows on 36 New York dairy farms. Eighty percent of the cows were infused with nine different antibiotic preparations separately at drying off, and 20% served as controls. Cows dried off by intermittent milking has a similar number of quarters infected at drying off, had fewer spontaneous recoveries, had a higher rate of cure, and developed fewer new infections in control quarters in comparison with cows dried off by the stop method. Methods worked equally well in treated cows. However, intermittent milking resulted in fewer infections at subsequent calving than stop milking in nondry treated cows. Cows producing less than or equal to 4 kg of milk at drying off were more highly infected than higher producing cows. Hind quarters contained more infections at drying off, fewer responded to therapy, and more infections developed in the dry period. Cows with dry periods of less than or equal to 30 days had more infected quarters respond to therapy and had the fewest new infections in the dry period. The role of routine dry cow therapy in decreasing the number of infections in dairy herds by preventing new infections and removing old infections is demonstrated.

Animals↗

PubMed1972