caa a22 4500 469127546 CHVBK 20180323133154.0 cr unu---uuuuu 170328e19921201xx s 000 0 eng 10.1007/BF02356752 doi (NATIONALLICENCE)springer-10.1007/BF02356752 Genetic and environmental variation in reproductive and lactational performance of Jersey cattle in the coastal lowland semi-humid tropics [Elektronische Daten] [D. Njubi, J. Rege, W. Thorpe, E. Collins-Lusweti, R. Nyambaka] Summary: Reproductive and lactational performances, including length of productive life, were evaluated from records for 1960 to 1988 for a Jersey herd in coastal lowland semi-humid Kenya. The herd grazed natural pastures and until the mid 1970s received supplementary feeding. Mean performance included 31 months age at first calving, lactation milk yield (MY) of 1,788 kg in 3·3 lactations and a calving interval (CI) of 408 days. Mean milk yields declined from over 2,200 kg in the 1960s to about 1,500 kg in the 1980s with concomitant changes in calving interval, length of productive life and infertility. While annual genetic components of change in MY and CI were not significantly different from zero, the environmental components were large and significant (P<0·01) showing that the declines in performance probably resulted from decreased feed availability and less efficient disease control. Estimates of genetic parameters were consistent with those in the literature. With good management purebred Jersey cows in coastal lowland semi-humid Kenya were productive, but animal and herd productivity were highly dependent on management level which had a major effect on both milk yield and reproductive wastage. Centre for Tropical Veterinary Medicine, 1992 Njubi D. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut Rege J. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut Thorpe W. Kenya Agricultural Research Institute/International Livestock Centre for Africa Collaborative Programme, PO Box 80147, Mombasa, Kenya aut Collins-Lusweti E. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut Nyambaka R. Kenya Agricultural Research Institute/International Livestock Centre for Africa Collaborative Programme, PO Box 80147, Mombasa, Kenya aut Tropical Animal Health and Production Kluwer Academic Publishers 24/4(1992-12-01), 231-241 0049-4747 24:4<231 1992 24 11250 https://doi.org/10.1007/BF02356752 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02356752 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Njubi D. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut NATIONALLICENCE 700 1- Rege J. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut NATIONALLICENCE 700 1- Thorpe W. Kenya Agricultural Research Institute/International Livestock Centre for Africa Collaborative Programme, PO Box 80147, Mombasa, Kenya aut NATIONALLICENCE 700 1- Collins-Lusweti E. Department of Animal Production, University of Nairobi, PO Box 29053, Nairobi, Kenya aut NATIONALLICENCE 700 1- Nyambaka R. Kenya Agricultural Research Institute/International Livestock Centre for Africa Collaborative Programme, PO Box 80147, Mombasa, Kenya aut NATIONALLICENCE 773 0- Tropical Animal Health and Production Kluwer Academic Publishers 24/4(1992-12-01), 231-241 0049-4747 24:4<231 1992 24 11250 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer