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Hayashi, T.; Nagamine, Y.

1993

Animal Science & Technology 64(12): 1149-1155

Estimation of lactation curve by only two samplings of daily yield

The objective of this study was to estimate lactation parameters analytically from two sets of data which were maximum yield day and optional day in lactation. HAYASHI et al. proposed the vibration model. This model is composed of two exponential functions of days after calving and three parameters ("a", "b" and "c"). Lactation characteristics are well explained by parameters which are estimated via an iterative procedure with daily or monthly yield data. We estimated three parameters from two sets of data and called it the Two Point Method for the vibration model. The non-linear function of "a" contains constants and four known terms: maximum yield, day of maximum yield, optional day and yield of optional day. Since an adequate estimate of "a" is obtainable by the Newton method, we can obtain estimates of other parameters "b" and "c" from the relationship of maximum yield, day of maximum yield and parameter "a". Multiple correlation coefficients for the models are in order of WOOD'S model using monthly sample data gt vibration model using monthly sample data gt vibration model using the two points method. Standard error in the 305-day yield estimates of the models; 258.2 for WOOD'S model, 218.5 for the vibration model and 349.1 for the two points method for the vibration model is discussed.
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