TAILIEUCHUNG - Báo cáo sinh học: "Population analysis of a purebred Hereford and a multibreed synthetic beef cattle herd"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Population analysis of a purebred Hereford and a multibreed synthetic beef cattle herd | 135 Genet Sei Evol 1995 27 135-148 Elsevier INRA Original article Population analysis of a purebred Hereford and a multibreed synthetic beef cattle herd PF Arthur1 M Makarechian2 R Weingardt2 RT Berg2 1 NSW Agriculture Agricultural Research Centre Trangie NSW 2823 Australia 2 Department of Animal Science University of Alberta Edmonton AB T6G 2P5 Canada Received 25 May 1994 accepted 17 November 1994 Summary - Lifetime records of females born from 1966 to 1975 were used to estimate and compare population parameters of a purebred Hereford HE and a multibreed synthetic SY1 beef cattle herd raised under a stringent culling policy whereby heifers and cows failing to wean a calf each year were culled. Population size averaged 118 cows 39 heifers and 155 cows 56 heifers a year for HE and SY1 respectively. The SY1 was a multibreed composite breed group with an average breed composition of 33 Charolais 33 Angus and 20 Galloway and the remainder from other beef breeds. The 2 herds were raised under the same management. Nine life table statistics were studied agespecific survivorship age-specific survival rate mortality rates Qx expected herd life age-specific birth rate reproductive value net reproductive rate Ro instantaneous rate of population increase r and generation interval T . Differences were obtained between the herds for the age-specific life table statistics with SY1 having higher values except for lower Qx values than HE. SY1 had higher means than HE for Ro versus p and r versus p indicating a faster rate of population growth in SY1. The value of T for SY1 was higher p than that for HE versus years . The results indicate that the same management and culling policy may result in different life table statistics which in this study was possibly due to the influence of heterosis for calf survival in the multibreed composite SY1 herd. Over time the stringent culling policy had the effect of .

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