Repeatability of reproductive performance of beef bulls as yearlings and two-year-olds at pasture |
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| Affiliation: | 1. SaBio IREC (UCLM-CSIC-JCCM), Campus Universitario, Albacete, Spain;2. Regional Center of Animal Selection and Reproduction (CERSYRA) JCCM, Valdepeñas, Spain;3. Reproductive Ecology and Biology Group, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain;1. Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB, 08193, Cerdanyola del Vallès, Catalonia, Spain;2. Animal Breeding and Genetics Program, Institute for Research and Technology in Food and Agriculture (IRTA), Torre Marimon, 08140, Caldes de Montbui, Catalonia, Spain;3. GABI, INRA, AgroParisTech, Université Paris-Saclay, UMR, 1313, Jouy-en-Josas, France;4. Departament de Sanitat i d’Anatomia Animals, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain;5. IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193, Bellaterra, Catalonia, Spain;6. Department of condensed matter physics, Faculty of Physics, Universitat de Barcelona, Barcelona, Cataloina, 08028, Spain;7. Department of Animal Medicine and Surgery, School of Veterinary Sciences, Universitat Autonoma de Barcelona, 08193, Cerdanyola del Vallès, Catalonia, Spain;8. Biotechnology of Animal and Human Reproduction (TechnoSperm), Unit of Cell Biology, Department of Biology, Institute of Food and Agricultural Technology, Faculty of Sciences, University of Girona, E-17003 Girona, Catalonia, Spain;9. Departament de Ciència Animal i dels Aliments, School of Veterinary Sciences, Universitat Autonoma de Barcelona, 08193, Cerdanyola del Vallès, Catalonia, Spain;10. Consejo Superior de Investigaciones Científicas (CSIC), 08003, Barcelona, Catalonia, Spain;2. Poultry CRC, PO Box U242, University of New England, Armidale, NSW 2351, Australia;3. Animal Welfare Science Centre, The University of Melbourne, Parkville, VIC 3010, Australia;1. Research Unit of Behavioural Ecology, Ethology and Wildlife Management, Department of Life Sciences, University of Siena, Siena, Italy;2. Chair of Wildlife Ecology and Management, University of Freiburg, Freiburg, Germany;3. Alpine Wildlife Research Centre, Gran Paradiso National Park, Noasca, Torino, Italy;4. Maremma Natural History Museum, Grosseto, Italy;1. Department of Animal Biochemistry and Biotechnology, Faculty of Animal Bioengineering, University of Warmia and Mazury in Olsztyn, 10-719, Olsztyn, Poland;2. Department of Animal Genetics, Faculty of Animal Bioengineering, University of Warmia and Mazury in Olsztyn, 10-719, Olsztyn, Poland;3. Centre of Veterinary Sciences, Inter-University Centre of Veterinary Medicine, Nicolaus Copernicus University, 87-100, Torun, Poland;4. Department of Plant Physiology and Biotechnology, Faculty of Biology and Biotechnology, University in Olsztyn of Warmia and Mazury in Olsztyn, 10-719, Olsztyn, Poland;5. Department of Clinical Sciences, Internal Disease Unit, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, 10-719, Olsztyn, Poland;6. Department of Cattle Breeding, National Research Institute of Animal Production, 32-083, Balice, Poland;1. Animal and Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Athenry, Co. Galway, Ireland;2. Animal and Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland |
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| Abstract: | Bull fertility, measured as pregnancy rate, percentages of calves born during the first 4 and 6 weeks of calving and means and medians of calving date distributions, was studied in 62 single-sire breeding herds of three breed groups over a 10-year period. Each bull was used as a yearling and then again as a 2-year-old. Average bull-to-cow ratio was approximately 1:20, and the breeding season started on 1 July and extended for approximately 60 days. The average pregnancy rate of cows mated to yearling bulls was similar to that for 2-year-old bulls (83.9% vs. 82.5%, respectively). There was a tendency towards earlier breeding among 2-year-old compared to yearling bulls as shown by 6.8% more (P = 0.09) calves born during the first 4 weeks of calving and 2.5 days advancement (P = 0.10) in the median of calving date distribution. Year and breed group of bull had no significant effect on the measures of bull fertility. The repeatability estimates of the measures of bull fertility were low, indicating that the reproductive performance of a 2-year-old bull cannot be accurately predicted from his performance as a yearling. |
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