Adjustment of lactation yield for age at calving in relation to level of production |
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| Affiliation: | 1. Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education in China, Huazhong Agricultural University, Wuhan, 430070, Hubei, China;2. Dairy Cattle Research Center, Shandong Academy of Agricultural Sciences, No.159 North of Industry Road, Jinan, 250131, Shandong, China;1. Key Lab of Intelligent Computing and Signal Processing of Ministry of Education, School of Computer Science and Technology, Anhui University, Hefei, Anhui, China;2. Department of Computer Science and Engineering, University of Texas at Arlington, Engineering Research Building, Room 529, 500 UTA Blvd, Arlington, TX 76019, USA;1. KU Leuven, Department of Biosystems, Division of Animal and Human Health Engineering, Campus Geel, Kleinhoefstraat 4, 2440, Geel, Belgium;2. Ghent University, Department of Reproduction, Obstetrics and Herd Health, M-team & Mastitis and Milk Quality Research Unit, Salisburylaan 133, 9820, Merelbeke, Belgium;3. Province of Antwerp, Hooibeekhoeve, Hooibeeksedijk 1, 2440, Geel, Belgium;1. Norwegian University of Life Sciences, Department of Production Animal Clinical Sciences, PO Box 369 Sentrum, N-0102, Oslo, Norway;2. TINE SA, P.O. Box 58, N-1430, Ås, Norway;3. Norwegian University of Life Sciences, Department of Animal and Aquacultural Sciences, Ås, Norway;2. Department of Food Science, University of Guelph, Guelph, ON, N1G 2W1, Canada;3. Department of Comparative Biomedicine and Food Science (BCA), University of Padova, Viale dell''Università 16, 35020, Legnaro, Italy;4. Department of Mathematics and Statistics;6. Canadian Dairy Network, Guelph, ON, N1K 1E5, Canada;2. Farm Technology Group, Wageningen UR, Wageningen, the Netherlands 6708 WD |
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| Abstract: | The influence of age at calving on 305-day milk, fat and protein yield in relation to herd and population level of production was investigated and a procedure for age adjustment was derived.Age differences were estimated by a repeatability model for 49 669 complete 305-day lactation records (kg milk, kg fat and kg protein) from 27 965 Dutch Friesian cows calving between 1 June 1979 and 31 May 1982. Several mathematical functions were applied to the estimated age differences. The best fit was by a second degree polynomial for Lactations 1 and 2 separately (R2 ⩾ 0.995) and a linear function including the log of age at calving for third and later lactations (R2=0.967).One set of adjustment factors was found to apply to all herd levels of production. However, age adjustment factors were different from those found by Dommerholt (1975) where the population level was about 1000 kg milk lower. A more accurate age adjustment would be obtained by updating the mean production of heifers at 24 months of age and using mathematical functions for computation of age factors. |
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