TY - JOUR ID - 83942 TI - Investigation of standard and atypical lactation curves of Simmental and Jersey ‎cows in Iran JO - Iranian Journal of animal Science JA - IJAS LA - en SN - 2008-4773 AU - Abbasi, Mokhtar Ali AU - Pahlavan, Rostam AU - Afrazandeh, Mohamadreza AU - kazemi, mazdak AU - Hassani Baferani, Alireza AU - kazemi, ali AU - Jamali, Negin AD - Associate Professor in Animal Breeding and Genetics, Institute of Agricultural Research, Education and ‎Extension Organization (AREEO), Animal Science Research Institute (ASRI), Karaj, Iran AD - Ph.D. in Animal Breeding and Genetics, Animal Breeding Center and Promotion of Animal Products, Ministry of ‎Agriculture, Karaj, Iran AD - M. Sc. in Animal Breeding and Genetics, Animal Breeding Center and Promotion of Animal Products, Ministry of Agriculture, ‎Karaj, Iran AD - Assistant Professor in Animal Breeding and Genetics, Institute of Agricultural Research, Education and Extension Organization ‎‎(AREEO), Ministry of Agriculture, Tehran, Iran AD - Ph.D. in Animal Physiology, Animal Breeding Center and Promotion of Animal Products, Ministry of Agriculture, Karaj, Iran Y1 - 2021 PY - 2021 VL - 52 IS - 2 SP - 123 EP - 131 KW - Atypical lactation curve KW - Jersey KW - milk yield KW - Simmental DO - 10.22059/ijas.2021.323864.653826 N2 - Lactation length is different in individual cows, which is generally converted to a 305-day standard using curve fitting models for genetic and management practices. Individual curves do not have a standard shape in all cases, and can deviate from the standard pattern according to factors such as individual differences, and type of fitted models. These non-standard curves, called atypical, resulted from incorrect estimated parameters of the curves; which consist of: continuously increasing or decreasing and reversed standards. This study was conducted to investigate the importance of atypical curves in estimation of 305-day milk production, by fitting two nonlinear models? Wood (empirical) and Pollott (biological), on 7659 and 6692 test-day milk yield of 977 and 776 first calving Iranian Simmental and Jersey cows, during 2007-2020, using R software. Different patterns obtained based on the combination of increasing (b) and decreasing (c) phase parameters of curves. The number of standard curves from the Pollott and Wood models were 85.5% and 62.2% for Simmental, and 83.1% and 70.6% for Jersey cows, respectively. Only continuously increasing curves were observed in both breeds in Pollott model (14.8% and 16.9%, Simmental and Jersey cows, respectively); Whereas in Wood model, all 3 groups of atypical curves were observed, which the reversed standard was the most (22.3% and 16.5%, Simmental and Jersey cows, respectively). Based on the findings, at the time of standardizing the production of dairy cows (national evaluations), not only differences between breeds, but also special attention to the production of atypical curves, should be paid (to correct or discard them). UR - https://ijas.ut.ac.ir/article_83942.html L1 - https://ijas.ut.ac.ir/article_83942_47052b7b5adf7504cc7ffa2b28923d4a.pdf ER -