Estimation of genetic parameters and trends for milk fat and protein percentages in Iranian Holsteins using random regression test day model

Abstract

Abstract. The aim of the present study was to estimate the genetic parameters and trends for fat and protein percentages of milk in Iranian Holsteins calving between 2001 and 2010 using the random regression test day model. Data set included 505 160 test day records that were collected by the Animal Breeding Centre of Iran. The Legendre polynomial functions of orders (5, 5) and (5, 6) were chosen to fit the additive genetic and permanent environmental effects of fat and protein percentages, respectively. Estimated heritabilities ranged from 0.053 to 0.232 and 0.111 to 0.259 for fat and protein percentages, respectively. The averages of estimated breeding values were −8.61 and −3.15 and annual genetic trends were −0.74 kg and −0.64 kg for fat and protein percentages, respectively. Negative genetic trends for fat and protein percentages are likely the result of major emphasis on milk yield in the breeding plan of Iranian Holsteins.

Genetic Parameters, Breeding Values and Genetic Trends for Some Productive and Reproductive Traits of Holstein Cows in Egypt

“…In contrast, they were negative for protein yield (-0.098). The current results were in agreement with those recorded by others [6,45,56], but controversy with Khanzadeh et al [28], Abdullahpour et al [57] and Hossein-Zadeh [58]. The high positive genetic trends for fat and protein yields ensured the strong relationship between milk yield and these traits genetically as compared to percentage traits.…”

“…Heritability estimates of fat and protein% were 0.38 and 0.25, respectively. These estimates were higher than those reported previously [27,28]. High heritability estimates for fat and protein yields (0.37 and 0.32, respectively), which are consistent with those obtained by Mashhadi et al [29], but are higher than those recorded by others [30,31].…”

Genetic Parameters Estimation of Milking Traits in Polish Holstein-Friesians Based on Automatic Milking System Data

“…The curve showing the daily heritabilities of milk yield during lactation has the shape of an inverted parabola, which coincides with the results of other authors [8,15,32]. However, many studies reported that the parameters of milk yield were higher in the initial and final stages of lactation than in mid-lactation [9,20,24]. Jamrozik et al [40] and Strabel et al [23] consider that this trend is especially evident when assuming the fixed effect of PE for each day of lactation, and, unlike in our study, they assumed a random effect of PE.…”

“…Strabel et al [23] demonstrated that the order of polynomial influences the values of estimated genetic parameters, and that it is appropriate to use fifth-order polynomials to estimate genetic variation in Polish Holstein-Friesian (PHF) cattle. The optimum order of Legendre polynomial was investigated by Khanzadeh et al [24]. These authors estimated genetic parameters as well as the breeding value for the fat and protein (%) content of milk by modeling the lactation curve using third-to sixth-order Legendre polynomials.…”

Comparison of random regression models, traditional animal model and with the inclusion of molecular markers in the estimation of genetic parameters in Colombian Holstein cattle

“…PP is reported by several authors to be one of the traits with the highest heritability, with values commonly close to or greater than 0.3 (Zambrano et al, 2014;Rincón et al, 2015) or even reaching values between 0.47 and 0.65 (Makgahlela et al, 2013;Zhao et al, 2015;Gebreyesus et al, 2016), and this trait is less affected by environmental effects than milk production is (Lipkin, Bagnato, & Soller, 2008a). The heritability found for PP with the random regression model was 0.29, surpassing that reported by other authors (Khanzadeh, Hossein, & Naserani, 2013); however, it is important to highlight that few reports on heritability of protein percentage use this methodology; random regression has typically been used to model protein content rather than protein percentage (De Roos, Harbers, & De Jong, 2004;Caccamo et al, 2008;Múnera, Herrera, Gonzáles, Henao, & Cerón, 2014).…”