13 research outputs found
Reproductive performance of Norwegian cattle from 1985 to 2005: trends and seasonality
Declining reproductive performance is a serious breeding concern in many countries. To reveal the situation in Norwegian cattle, trends in reproductive performance were studied using insemination reports from 1985 to 2005 and data based on herd recording files from 1989 to 2005. The total number of first services was 469.765 in 1985 declining to 335.712 in 2005. The number of recorded herds and animals declined from 21.588 to 14.718 and 360.289 to 309.452 from 1989 to 2005, respectively. Sixty days non-return rate after single inseminations (NR60) increased from 68.1 in 1985 to 72.7% in 2005 (p < 0.001) and the number of services per inseminated animal (NIA) decreased from 1.8 to 1.6 (p < 0.001) from 1985 to 2005. However, return rates 0–3 days post insemination (RR0-3) increased from 6 to 12% in the same period (p < 0.001). NR60 was higher and the RR0-3 was lower in the summer season compared to the winter season during the whole period. A fertility index (FS), has been calculated from the herd recording files each year from 1989 to 2005. The average FS-index did not show a significant trend and the calving interval was also fairly constant between 12.4 and 12.6 months during this period. The average interval from calving to first and last insemination, respectively, increased from a low of 79 and 102 days in 1990 to a high of 86 and 108 days in 2005. Both intervals were consistently longer for cows in first lactation than for cows in later lactations. The percentage of inseminated animals reported culled because of poor fertility decreased from 6.0% in 1989 to 4.6% in 1996 and thereafter again increased to 6% in 2005. In conclusion, most fertility measures, mainly comprising the Norwegian Red (NRF) breed, show a relatively high level of reproductive performance with a positive or a relatively constant trend during the last two decades
Gravitational Lensing in Astronomy
Deflection of light by gravity was predicted by General Relativity and
observationaly confirmed in 1919. In the following decades various aspects of
the gravitational lens effect were explored theoretically, among them the
possibility of multiple or ring-like images of background sources, the use of
lensing as a gravitational telescope on very faint and distant objects, and the
possibility to determine Hubble's constant with lensing. Only relatively
recently gravitational lensing became an observational science after the
discovery of the first doubly imaged quasar in 1979. Today lensing is a booming
part of astrophysics.
In addition to multiply-imaged quasars, a number of other aspects of lensing
have been discovered since, e.g. giant luminous arcs, quasar microlensing,
Einstein rings, galactic microlensing events, arclets, or weak gravitational
lensing. By now literally hundreds of individual gravitational lens phenomena
are known.
Although still in its childhood, lensing has established itself as a very
useful astrophysical tool with some remarkable successes. It has contributed
significant new results in areas as different as the cosmological distance
scale, the large scale matter distribution in the universe, mass and mass
distribution of galaxy clusters, physics of quasars, dark matter in galaxy
halos, or galaxy structure.Comment: Review article for "Living Reviews in Relativity", see
http://www.livingreviews.org . 41 pages, latex, 22 figures (partly in GIF
format due to size constraints). High quality postscript files can be
obtained electronically at http://www.aip.de:8080/~jkw/review_figures.htm
Animals living in polluted environments are potential source of antimicrobials against infectious agents
Reproductive performance of crossbred dairy cows under smallholder production system in Kurdistan province of Iran
Meiotic segregation analysis in cows carrying the t(1;29) Robertsonian translocation.
Heterozygous carriers of Robertsonian translocations generally have a normal phenotype but present reproductive failure. In cattle, the t(1;29) Robertsonian translocation is very common and carriers show a 3-5% decrease in fertility. Some data suggest that female carriers have a higher decrease than male carriers but no direct studies of the chromosome content of oocytes from a t(1;29) carrier cow have been performed so far. Four heterozygous carrier cows underwent hormonal stimulations and follicles punctions and about 800 oocytes were matured in vitro. Six hundred metaphase II preparations were obtained and analysed by fluorescent in situ hybridization with bovine chromosome 1 and 29 painting probes. Proportions of different kinds of oocytes were assessed: 74.11% (292/394) were normal and balanced, 4.06% (16/394) unbalanced and 21.83% (86/394) diploid. For all cows, the number of normal oocytes was not significantly different from the number of translocated oocytes but the diploidy and unbalanced rate were significantly different between them. As found in bulls, the meiotic segregation pattern in cows has shown a preponderance of alternate products. However, the frequency of unbalanced gametes determined in females (4.06%) was significantly higher than the frequency observed in males (2.76%). The divergence in the rate of diploid gametes (0.04% vs. 21.83%) is mainly explained by the difference between males and females