Maryam Arianfar; Mohammad Rokouei; Gholamreza Dashab; Hadi Faraji- Arough
Volume 20, Issue 3 , November 2018, , Pages 351-363
Abstract
The objective of this study was to compare some nonlinear functions (Wood, Dhanoa, Wilmink, Ali-Schaeffer, Cappio Borlino, Cobby – Le Du, Dijkstra, Rook, Gous and Nelder) to describe the milk production curve of Iranian Holstein cattle. A dataset consisted of 6079976, 4879486 and 3312416 test-day ...
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The objective of this study was to compare some nonlinear functions (Wood, Dhanoa, Wilmink, Ali-Schaeffer, Cappio Borlino, Cobby – Le Du, Dijkstra, Rook, Gous and Nelder) to describe the milk production curve of Iranian Holstein cattle. A dataset consisted of 6079976, 4879486 and 3312416 test-day milk yield records related to first, second and third three lactation periods, respectively, from 3550 herds collecting by the Animal Breeding Center of Iran from 1983 to 2017, were used. The average of test day milk records for three lactation was 31.17, 34.08 and 33.83 kg, respectively. The nlme package of R software (version 3.4.3) was used for fitting nonlinear functions. The nonlinear functions were compared using four goodness of fit criteria, including Akaike’s information criterion (AIC), Bayesian information criterion (BIC), Root mean square error (RMSE) and Durbin-Watson index (DW). The Rook function showed the best fit for the milk production curve shape for three lactations in Iranian Holstein cattle when compared to other functions. The Gous and Rook functions showed the highest accuracy in predicting peak time, peak yield and persistency of milk production parameters in different lactations, but in general, the Rook function has a high predictive value in estimating the milk curve parameter descriptors.Therefore, Rook function is recommended for describing the milk production curve of Iranian Holstein cattle.
Zohreh Shirmoradi; Abdol Reza Salehi; Rostam Pahlavan; Mohamad Reza Mollasalehi
Volume 12, Issue 2 , October 2010, , Pages 21-28
Abstract
In this study, the genetic and phenotypic trend of milk and fat production traits were estimated form 94121 cows’ first lactation records and that for age at first calving and calving interval traits were estimated from 41900 cows’ reproduction records. Data related to Iranian Holstein dairy ...
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In this study, the genetic and phenotypic trend of milk and fat production traits were estimated form 94121 cows’ first lactation records and that for age at first calving and calving interval traits were estimated from 41900 cows’ reproduction records. Data related to Iranian Holstein dairy cattle from 1995 to 2003. Data were analyzed, using univariate and mulitivariate animal model with genetic group effects. The heritability of milk yield, fat yield and fat percentage, age at first calving and calving interval were 0.29 (±0.01), 0.22 (±0.01), 0.38 (±0.01), 0.055 (±0.01) and 0.034 (±0.005), respectively. The linear regression of average breeding values and phenotypic values of cows for a trait on birth year provided an estimate of genetic and phenotypic trend, respectively. There genetic trend for milk yield, fat yield and Calving Interval were 53.5 kg, 1.07kg and 0.46 day, respectively. Their trend for fat percentage and Age at First Calving were -0.011% and -0.23 day, respectively. There was a positive phenotypic trend for milk yield, fat yield and fat percentage. This trend was negative for Age at First Calving and Calving Interval.