Genetic parameters for lactose percentage in the milk
of Polish Holstein-Friesians

Ptak, E.; Brzozowski, P.; Bieniek, J.

doi:10.22358/jafs/66072/2012

Cited by 17 publications

(18 citation statements)

References 15 publications

(48 reference statements)

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“…This disagrees with reports by Miglior et al (2006) and Ptak et al (2012), who found that the lactose curve was very similar to the milk yield curve, with a maximum value between 30 and 60 days and a gradual decrease in the remaining days. Miglior et al (2006) found that the lowest lactose concentration occurred in summer time.…”

Section: Discussioncontrasting

confidence: 99%

Lactose and milk urea nitrogen: fluctuations during lactation in Holstein cows

et al. 2014

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-The objective of this study was to evaluate lactose and milk urea nitrogen (MUN) in milk from Holstein cows and their relationship with days in milk (DIM), milk yield, milk fat, milk protein, and somatic cell count (SCC). A total of 1,034 records corresponding to morning and afternoon milkings of 148 Holstein cows were used. Records were taken from 16 herds located in the Northern and Eastern dairy regions of Antioquia (Colombia). The curves were fitted using a generalized additive mixed model with smoothed estimates to find the best smoothing intensity factors involved in MUN and lactose concentration. Regarding MUN, the contemporary group effect was highly significant, but the parity effect was not significant. The DIM, lactose and milk fat smoothed covariates were highly significant, while milk yield and fat and SCC showed no statistical difference. Regarding lactose content, the contemporary group effect was highly significant, while the parity effect was not significant. Days in milk, MUN, milk fat, milk protein, and afternoon-milking SCC smoothed covariates were highly significant, while milk yield and morning-milking SCC were not significant. Lactose and milk urea nitrogen concentrations are affected by various factors throughout lactation, mainly by days in milk.

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Section: Discussioncontrasting

confidence: 99%

Lactose and milk urea nitrogen: fluctuations during lactation in Holstein cows

et al. 2014

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“…The heritabilities for SCS were lower than the heritabilities for the production traits, and were equal to 0.13, 0.14 and 0.16 for the first three parities, respectively. The heritabilities for production traits and SCS were within the ranges reported for Polish Holstein-Friesians (Strabel et al 2004 ; Strabel and Jamrozik 2006 ; Yazgan et al 2010 ; Jesiołkiewicz et al 2011 ; Rzewuska et al 2011 ; Ptak et al 2012 ) and all—except the heritability for SCS—were lower than those obtained for Canadian and Dutch populations (Wood et al 2003 ; Miglior et al 2007 ; Stoop et al 2007 ). A similar relation between heritabilities estimated for the production traits of the Polish and Canadian populations, with higher values for the latter, was indicated in an earlier study (Strabel et al 2004 ).…”

Section: Resultssupporting

confidence: 61%

Genetic parameters for milk urea concentration and milk traits in Polish Holstein-Friesian cows

Rzewuska

Strabel

2013

J Appl Genetics

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Milk urea concentration (MU) used by dairy producers for management purposes can be affected by selection for milk traits. To assess this problem, genetic parameters for MU in Polish Holstein-Friesian cattle were estimated for the first three lactations. The genetic correlation of MU with milk production traits, lactose percentage, fat to protein ratio (FPR) and somatic cell score (SCS) were computed with two 5-trait random regression test-day models, separately for each lactation. Data used for estimation (159,044 daily observations) came from 50 randomly sampled herds. (Co)variance components were estimated with the Bayesian Gibbs sampling method. The coefficient of variation for MU in all three parities was high (40–41 %). Average daily heritabilities of MU were 0.22 for the first parity and 0.21 for the second and third lactations. Average genetic correlations for different days in milk in the first three lactations between MU and other traits varied. They were small and negative for protein percentage (from −0.24 to −0.11) and for SCS (from −0.14 to −0.09). The weakest genetic correlation between MU and fat percentage, and between MU and lactose percentage were observed (from −0.10 to 0.10). Negative average genetic correlation with the fat to protein ratio was observed only in the first lactation (−0.14). Genetic correlations with yield traits were positive and ranged from low to moderate for protein (from 0.09 to 0.33), fat (from 0.16 to 0.35) and milk yield (from 0.20 to 0.42). These results suggest that the selection on yield traits and SCS tends to increase MU slightly.

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“…However, the lactose content found by Brito et al (2011) was much lower (0.17) than that presented in our and Andonov et al (2007) studies. In the literature different results for lactose content in cow's milk are presented -from 0.17 to 0.36, depending of the stage of lactation and parity with the lowest at the beginning of the first lactation (Ptak et al, 2012) up to an average heritability of 0.48 in the first, and 0.51 in the second and later parities (Miglior et al, 2007).…”

Section: Resultsmentioning

confidence: 99%