Keywords: prediction, age at first calving, exterior traits, model, regression
The results of predicting the age of the first calving using multiple regression analysis, based on exterior measurements and body structure indices of heifers, determined twice – at the age of about 100 days and about a year are shown. The models are designed using both linear and nonlinear components. The developed models are considered in terms of their adequacy and reliability. To improve the quality of the models, the “folding knife” method was tested. Verification of models was carried out by methods of sliding control, division of the sample into educational and examination samples and selection simulation. The most important dependencies are highlighted and analyzed. Based on the exterior indicators of heifers around 100 days of age, we obtained a model for predicting the age of the first calving, which was unreliable (P = 0.91) and characterized by a low reduced coefficient of determination (R2adj = 0.21) and a large standard prediction error (SE = 104.75 days). The final parameters of the model of predicting the age of the first calving based on exterior indicators determined at an age of about one year are characterized by high reliability (p> 0.999), good determination (R2adj = 0.58) and quite acceptable differences between predicted and actual values of the age at first calving (SE = 77.01 days). The most adequate is the model based on a double exterior study. It is advisable to use this model in the version of the “folding knife” for a more accurate and complete assessment of animals at an early age. This model provides a coincidence of predicted and actual negative estimates of the age of the first calving in 65.7% of cases. The most valuable features for predicting and interpreting the dependence of the age of the first calving on the exterior of heifers are such as the stretch index and oblique body length at 365 days of age. The degree of their influence on the expected age of the first calving is the maximum among all predictors and is η2=16.46% and η2=9.10%, respectively.
- Mohd Nor, N., Steeneveld, W., Mourits, M., & Hogeveen, H. (2015). The optimal number of heifer calves to be reared as dairy replacements. J. Dairy Sci., 98(2), 861–871.
- Shablia, V. P., Zadorozhna, I. Yu., & Shablia, P. V. (2019). Porivnialna otsinka vplyvu vyroshchuvannia telyts i hodivli koriv na nadoi. [Comparative assessment of the impact of growing heifers and feeding of cows on milk yield]. Visnyk Sumskoho natsionalnoho ahrarnoho universytetu. Seriia «Tvarynnytstvo». Sumy,1-2 (36-37), 107-113 [in Ukrainian].
- van der Heide, E. M. M., Veerkamp, R. F., van Pelt, M. L., Kamphuis, C., & Ducro, B. J. (2020). Predicting survival in dairy cattle by combining genomic breeding values and phenotypic information J. DairySci., 103(1), 556–571. URL: https://doi.org/10.3168/jds.2019-16626
- van Pelt, M., G. De Jong, & R. Veerkamp.(2016). Changes in the genetic level and the effects of age at first calving and milk production on survival during the first lactation over the last 25 years. Animal, 10, 2043–2050. URL: https://doi.org/10.1017/S1751731116001282
- Boulton, A., Rushton, J., & Wathes, D. (2017). An empirical analysis of the cost of rearing dairy heifers from birth to first calving and the time taken to repay these costs. Animal, 11(8), 1-9. URL: https://doi.org/10.1017/S1751731117000064
- Danets, L. M., Tkachova, I. V., & Shablia, V. P. (2020). Vplyv zhyvoi masy pid chas vyroshchuvannia na tryvalist produktyvnoho vykorystannia koriv ukrainskoi chorno-riaboi molochnoi porody riznoi krovnosti za holshtynskoiu porodoiu. [Influence of live weight during raising on the duration of productive use of cows of Ukrainian black-and-white dairy breed of different blood by Holstein breed]. Tvarynnytstvo ta tekhnolohii kharchovykh produktiv, 11(2), 16-27 [in Ukrainian].
- Kuleshov, P. N. (1926). Vyborloshadej, skota, ovecisvinejpojekster‘jeru (iprisodejstviiindeksovslozhenija, ocenkiposhkalamistandartov: proizvoditel‘nosti, zhivogoiubojnogovesa). [Selection of horses, cattle, sheep and pigs by exterior (and assisted by addition indexes, scores and standards: performance, live and slaughter weight)]. Moskva-Leningrad [in Russian].
- Fenlon, C., O’Grady, L., Mee, J. F., Butler, S. T., Doherty, M. L., & Dunnion, J. (2017). A comparison of 4 predictive models of calving assistance and difficulty in dairy heifers and cows. J. Dairy Sci., 100(12), 1–13. URL: https://doi.org/10.3168/jds.2017-12931
- Lyskun, Ye. (1930). Ekster’ier silskohospodarskykh tvaryn. [Exterior of farm animals]. Kharkiv : Radianskyi selianyn [in Ukrainian].
- Gabris, S. (1965). Rozmery a forma tela pinzgauskych krav vatahu k dojevasti. Zivocisna vyroda. 10(1), 11-18.
- Afifi, A., & Jejzen, S. (1982). Statisticheskij analiz: Podhod s ispol’zovaniem JeVM [Statistical Analysis: A Computer Based Approach]. : Per. s angl. Moscow : Nauka [in Russian].
- Drejper, N., & Smit, G. (1986). Prikladnoj regressionnyj analiz (kniga 1). [Applied regression analysis (book 1)]. Moscow: Finansy i statistika [in Russian].
- Drejper, N., & Smit, G. (1987). Prikladnoj regressionnyj analiz (kniga 2). [Applied regression analysis (book 2)]. Moscow: Finansy i statistika [in Russian].
- Mosteller, F., & T’juki, Dzh. (1982). Analiz dannyh i regressija [Data analysis and regression. Release 1]. Moscow: Finansy i statistika, 1 [in Russian].
- Mosteller, F., & T’juki, Dzh. (1982). Analiz dannyh i regressija [Data analysis and regression. Release 2]. Moscow: Finansy i statistika, 2 [in Russian].
- Ivahnenko, A. G. (1975). Dolgosrochnoe prognozirovanie i upravlenie slozhnymi sistemami [Long-term forecasting and management of complex systems]. Kiev: Tehnіka [in Russian].
- Shablia, V. P. (1997). Patent 29989 Ukraina.
- Shablia, V. P., & Shablia, P. V. (2016). Komp’iuterna ekonometrychna model tekhnolohii skotarstva. [Computer econometric model of livestock technology]. Naukovo-tekhnichnyi biuleten Instytutu tvarynnytstva NAAN [Scientific and Technical Bulletin of the Institute of Animal Science of the National Academy of Agrarian Science of Ukraine]. Kharkiv,115, 242-252 [in Ukrainian].