Fit of different linear models to the lactation curve of Italian water buffalo (original) (raw)
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Present investigation was undertaken to compare the different lactation curve models for describing the shape of the lactation curve in Murrah buffaloes. Data for the present study included 9071 monthly test-day milk yield (MTDMY) from 965 Murrah buffaloes calved during 1977 to 2012 at the National Dairy Research Institute, Karnal. A total of 10 monthly test-day milk yield records were taken at an interval of 30 days. The data were used to estimate lactation curve parameters for four lactation curve models viz. Gamma type function (GF), Exponential function (EF), Mixed log function (MLF) and Polynomial regression function (MLF). The mean monthly test day milk yields (MTDMY) increased from 5.91±0.13 kg on TD1 to a peak yield of 7.41±0.12 kg on TD3. The estimates of coefficient of determination (R2) and root mean square error (RMSE) for GF, EF, MLF, and PRF were 96.42%, 98.65%, 98.48%, 99.86% and 0.077, 0.049, 0.052, 0.015, respectively. PRF fitted best to the test day data followed by EF on the basis of higher R2 and lower RMSE estimates, whereas GF fitted least.
Comparison of Different Lactation Curve Models of Anatolian Buffaloes
In this study, eight different lactation curve models were compared by using test day milk yield records belonging Anatolian Buffaloes raised in different Farm conditions between 2011 and 2013. To identify the best lactation curve models of Wood, Cobby and Le Du, Logaritmic Quadratic, Exponential, Parabolic exponential, Quadratic, Inverse Polynomial and Logaritmic Linear mathematical functions were used. The coefficient of determination (R2) and residual standard deviation (RSD) statistics were used for determination of best fitted model in lactation curve. Logaritmic Quadratic and Quadratic functions are the best goodness of fit model as having the highest R2 and lowest RSD coefficients. As a result, the parameters are estimated by logarithmic quadratic or quadratic models, for use in breeding programs will make an important contribution to research in this field. Keywords: Lactation curves, Anatolian Buffalo, Coefficient of determination and residual standard deviation
Frequency of standard and atypical lactation curves for milk, fat, protein and lactose yield in Bianca Val Padana cattle – The aim of the research was to evaluate the frequency and the parameters of standard and atypical lactation curves in Bianca Val Padana (BVP) cattle breed and the effects of some environmental factors on equation parameters. Data from 1636 test day controls of 262 lactations of 88 BVP cows were processed. The data relating to the daily production (kg) of milk, fat, protein and lactose were subjected to regression analysis, by applying the model of Wood in linear form (log yn = log A + B log n + Cn). Limited to standard curves with ADJRSQ >80%, persistence, week at peak and peak production were then calculated. Based on the algebraic sign of the parameters B and C, three different types of lactation curves (standard, decreasing, reversed) have been identified while it has never been detected the ascending type. As regards to daily milk production, the most com...