Somatic cell counts: associated factors and relationship to production.   总被引：1，自引：1，他引：0       下载免费PDF全文

E Salsberg  A H Meek    S W Martin 《Canadian journal of veterinary research》1984,48(3):251-257

Factors affecting somatic cell counts and the association between somatic cell counts and milk production were evaluated. Data were collected from 748 Ontario Dairy Herd Improvement Corporation supervised herds that were on production and somatic cell count programs between April 1981 and March 1983. Two data files were created; one, the lactation summary file, contained one record per cow on each of 9406 Holsteins and the other, the test day file, included results of all tests during the complete lactation on each of the above cows. The latter file contained 85,236 records. Multiple curvilinear least squares regression was used to create five separate models. The dependent variables used in the models were natural logarithms (Loge) of the geometric mean of the somatic cell count for the lactation, 305 day milk production and breed class average for milk from the lactation summary file, and loge of the 24 hour somatic cell count and 24 hour milk production from the test day file. The somatic cell count at both the lactation and test day level increased with age up to approximately ten years and thereafter slowly decreased. The variable "days in milk" was not significantly associated with the lactation average somatic cell count. A curvilinear relationship was found between days in lactation at the time of test and the somatic cell count of 24 hour milk production. The somatic cell count increased until approximately 250 days in lactation and thereafter slowly decreased. It was found that the highest cell counts occurred in summer and the lowest in winter.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

Incompatibility Between the Dimorphic Flowers of Collomia grandiflora, a Cleistogamous Species     

Lord EM  Eckard KJ 《Science (New York, N.Y.)》1984,223(4637):695-696

The cleistogamous species Collomia grandiflora produces dimorphic cross-incompatible flowers on a single plant. The open or chasmogamous flower has smaller, flask-shaped stigmatic papillae, larger pollen grains, longer styles, and faster pollen tube growth rates down the style than the closed or cleistogamous flower. In intermorph crosses, pollen tube growth rates are greatly decreased and fertilization does not occur.  相似文献   

Renewed Interest in Food Irradiation: FDA ponders approval as proponents push it as an alternative to pesticides     

Sun M 《Science (New York, N.Y.)》1984,223(4637):667-668

  相似文献   

The Fifth Generation: Taking Stock: The Japanese computer project is approaching its third birthday; meanwhile, the American programs are finally getting organized     

Waldrop MM 《Science (New York, N.Y.)》1984,226(4678):1061-1063

  相似文献   

Ethics in neuroscience: ethical questions in brain and behavior     

Bird SJ 《Science (New York, N.Y.)》1984,224(4649):595-596

  相似文献   

Groundwater contamination     

Bredehoeft JD  Usselman TM 《Science (New York, N.Y.)》1984,224(4655):1292

  相似文献   

Newton: in the presence of the creator     

Mahoney MS 《Science (New York, N.Y.)》1984,226(4670):39-40

  相似文献   

Effects of pretreatment conditions on ammonium and nitrate uptake by Douglas-fir seedlings     

Rygiewicz PT  Bledsoe CS 《Tree physiology》1986,1(2):145-150

Effects of pretreatment solutions containing varying concentrations of calcium, potassium, ammonium and nitrate were evaluated by measuring fluxes of the same ions during a subsequent 4-hour uptake by Douglas-fir seedlings. Maximal rate of ammonium uptake (11 microeq g(-1) root dry weight h(-1)) was about 5 times faster than that of nitrate (2 microeq g(-1) root dry weight h(-1)). Ammonium uptake was most rapid after pretreatment with low potassium levels and was unaffected by ammonium pretreatment. Nitrate uptake was most rapid after pretreatment with high levels of nitrate and low levels of potassium. Calcium uptake was greater when nitrate replaced ammonium as the N source. High calcium pretreatment levels depressed subsequent calcium uptake or resulted in calcium release in both ammonium and nitrate experiments. Potassium efflux occurred with both N sources, but the release was less during nitrate uptake than during ammonium uptake. Efflux of potassium is probably associated with the high potassium status of the seedlings and the exchange between potassium and other cations. High levels of potassium in the pretreatment solutions enhanced potassium efflux and caused a reduction in the subsequent rates of uptake of both ammonium and nitrate. Length of pretreatment and seedling size generally did not affect uptake rates.  相似文献   

Venus: detailed mapping of maxwell montes region     

Alexandrov YN  Crymov AA  Kotelnikov VA  Petrov GM  Rzhiga ON  Sidorenko AI  Sinilo VP  Zakharov AI  Akim EL  Basilevski AT  Kadnichanski SA  Tjuflin YS 《Science (New York, N.Y.)》1986,231(4743):1271-1273

From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled.  相似文献   

Research Coterie Meets At NAS to Assess Budget: NAS assembles 400 representatives academe, industry, and government to discuss priorities for science     

Crawford M 《Science (New York, N.Y.)》1986,231(4743):1239

  相似文献