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Biomedical subjects

J A Lineweaver

Publications and source records attributed to J A Lineweaver.

9 recordsLinked to original sources
PubMed1983

Environmental and management factors affecting estrous activity in dairy cattle.

One thousand periods of estrus of Holstein and Jersey cows and heifers of breeding age during 27 mo were used to evaluate environmental and management factors related to estrous behavior during twice-daily heat checks. Mounting activity at the first observation of estrus was influenced by sire within genetic selection group for milk yield, lactation number, primary housing location, time of day estrus first observed, and maximum temperature the day of estrus. Mean number of times an estrous cow was mounted increased from 6.0 mounts/h in the morning to 7.7 mounts/h in the evening. Barn-housed cattle had 8.7 mounts/h compared to 6.1 and 5.5 for dry-lot and pasture groups. Estrous activity was least for heifers and increased for older cows. Mounting activity increased with increasing maximum daily temperature to approximately 25 degrees C. Only 17.7% of the cattle initially observed in estrus displayed mounting behavior at the 12-h heat check. Estrous activity at 12 h was affected by lactation number and genetic grouping. Daily milk production near estrus was associated with longer duration between heats but had no effect on conception. Lactation number and service number were related to fertility.

Animals↗
PubMed1981

Rates of conception by artificial insemination of dairy cattle.

Over 41 mo, 1004 first and second service inseminations were evaluated in Holstein cows and heifers of breeding age. Cattle were inseminated either at the end of the heat check in which they were observed in heat (0 h) or at the end of the next heat check (12 h). Rate of conception was affected by estrous behavior at 12 h, site of semen placement in the reproductive tract, sire, and environmental temperature the day after insemination. Service number, time of day at which insemination occurred, inseminator, and timing of insemination in relation to the onset of estrus had no effect on fertility. With twice daily heat checks, a single daily service produced acceptable rates of conception.

Animals↗
PubMed1981

Interrelationships with estrous behavior and conception in dairy cattle.

A total of 199 inseminations and estrous periods of lactating cows and heifers of breeding age were used to assess behavioral, productive, environmental, and hormonal events at first observation of estrus and those 12 h later with concurrent breeding efficiencies. Cattle were observed twice daily for estrus, and blood samples were collected at the initial observation of estrus (0 h) and at 12 h. Fifty-one percent of the cattle first were detected in estrus in the morning. Morning estrous activity was greater (11.4 mounts/h) than that first observed in the evening (7.6). Mean estrous activity declined from 9.4 mounts/h at 0 h to 1.6 mounts/h at 12 h. Older cows exhibited more mounting activity than younger animals at 0 h. Barn housed cattle exhibited more mounts/h during detection of estrus (11.2) than cattle housed primarily in free stalls (6.5) or pasture (5.4). Early estrous activity (0 h) was not affected by estradiol, progesterone, or luteinizing hormone. However, estradiol and progesterone did exert an influence on activity seen at late estrus (12 h). Glucose and urea at 0 and 12 h were similar. There were no significant correlations of glucose or urea of plasma with estrous activity or conception. Feed intake and milk production from 3 days prior to 3 days postestrus did not change. Season affected estrous activity and conception. Highest conception was associated with low progesterone at 12 h.

Animal Feed↗
PubMed1979

Effect of prepartum selenium-vitamin E injection on time for placenta to pass and on productive functions.

The effect of a single injection of selenium-vitamin E containing 21.9 mg sodium selenite upon time for placenta to pass following calving and on subsequent reproductive and lactational performance was evaluated. Incidence of retained placenta was 11.4%. This amount of selenium-vitamin E did not affect the time for placenta to pass, did not reduce calving difficulty, nor did it increase number of heats prior to first breeding, decrease days open or services per conception, or increase milk the next lactation.

Animals↗
PubMed1978

Steroidogenic capabilities of the early mouse embryo.

Preimplantation embryos from ICR albino mice were used to determine progesterone and estradiol-17beta production during incubation in BMOC-2. Following culture of 40 embryos/culture at either the morula, early blastocyst or late blastocyst stages, progesterone and estradiol-17beta contents were 192 +/- 27 and 82 +/- 22 pg, 289 +/- 50 and 147 +/- 46 pg and 157 +/- 28 and 88 +/- 23 pg, respectively, for incubated samples and 306 +/- 68 and 89 +/- 40 pg, 404 +/- 63 and 125 +/- 44 pg, and 241 +/- 54 and 86 +/- 39 pg, respectively for control samples. Although, there were significant stage of development and treatments effects (p less than 0.05) for progesterone, production of this steroid was not evident. These data suggest that the early preimplantation mouse embryo does not produce progesterone or estradiol-17beta in a defined culture system.

Animals↗