Lactation curves of different cattle breeds under cooperative dairying conditions in Bangladesh

摘要

This study was undertaken to compare and evaluate the parameters of 10 different mathematical models for their predictive ability in describing the lactation curves for daily milk yield of different genotypes under cooperative dairying in Bangladesh. A database consisting of 7340 herd-test records from 738 cows over the period 1999?￠????2001 was assembled. Breed combinations included Pabna cattle, Australian-Friesian-Sahiwal????Pabna, Holstein????Pabna, Jersey????Pabna and Sahiwal????Pabna. The estimated parameters of the mathematical models, and the predicted lactation milk yields differed significantly between genotypes. The models were evaluated by four fit statistics: Akaike information criteria, coefficient of determination ( R 2 ), root mean square prediction error (RMSPE) and concordance correlation coefficient (CCC). The AIC values indicated that the Ali model provided a good fit for all genotypes. The R 2 value suggested that the Legendre polynomial and Ali models were the best fit for all genotypes. CCC and RMSPE values indicated that the best models for all genotypes were Nelder and Wood. Since the CCC value was considered the most informative of the four fit statistics, the Nelder model was the best model to predict the full lactation profile based on test-day records for all genotypes. Using the Nelder model, the predicted 270 day milk yield of the Australian-Friesian-Sahiwal????Pabna genotype was higher (1823 kg) than the other genotypes (1509, 1650, 1531 and 1627 kg for Pabna, Australian-Friesian?￠????Sahiwhal????Pabna, Jersey????Pabna and Sahiwal????Pabna, respectively).