Prediction of Daily and Lactation Yields of Milk, Fat, and Protein Using an Autoregressive Repeatability Test Day Model

• Published in: Journal of dairy science Vol. 87; no. 8; pp. 2591 - 2598
• Main Authors: Vasconcelos, J., Martins, A., Petim-Batista, M.F., Colaço, J., Blake, R.W., Carvalheira, J.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.08.2004; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: accuracy; Animal productions; Animals; autoregression; Biological and medical sciences; Cattle - genetics; Cattle - physiology; correlation; dairy cattle; dairy cows; Dairying - methods; Female; Food industries; Fundamental and applied biological sciences. Psychology; Lactation - genetics; lactation curve; lactation stage; Lipids - analysis; mathematical models; Milk - chemistry; Milk and cheese industries. Ice creams; milk fat yield; milk protein yield; Milk Proteins - analysis; milk yield; Models, Statistical; Portugal; prediction; prediction of test day record; Regression Analysis; repeatability; Terrestrial animal productions; test day model; Vertebrates; Portugal; TD; ATD; dairy cattle; STE; prediction of test day record; TIM; autoregression; test day model; LTE; Lactation; Dairy cattle; Prediction; Milk production; Repeatability; Vertebrata; Milk protein; Daily; Mammalia; Dairy industry; Models; Artiodactyla; Milk fat; Day; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(04)73384-6

We evaluated the accuracy of an autoregressive multiple-lactation test day (ATD) model to predict missing test day yields of milk, fat, and protein to obtain cumulative 305-d records for cows with incomplete or in-progress lactations. The data consisted of more than one million observations of daily yields on test days in the first 3 lactations of over 75,000 Portuguese Holstein cows. Differences between actual (estimates from complete lactations using the test interval method) and ATD-predicted 305-d yields were negligible and smaller than those predicted by the test interval method. The ATD procedure tended to slightly underestimate cumulative lactation yields, whereas the test interval method substantially overestimated them. Smaller differences obtained by the ATD procedure resulted in less biased estimates of lactation yield, which also implies greater accuracy. As expected, the correlations between actual and predicted lactation yields increased with the number of test days from 0.831 to 0.997. Average correlations (by parity) between actual and ATD-predicted yields ranged from 0.977 to 0.984. Correlations between actual test day yields and corresponding predicted yields exceeded 0.5 for up to 7 time-intervals from the last test day yield used to predict cumulative yield of projected lactations. These correlations indicate the good predictive ability of the ATD method. From a producer's viewpoint, these advantages underwrite management because most on-farm selection decisions are based on the producing abilities of cows. Implementation of ATD methodology does not require special computing capability and is easily transferable to the farm level.