Fourier-transform near- and mid-infrared (FTIR) milk spectral data are routinely collected in many coun- tries worldwide. Establishing an optimal strategy to use spectral data in genetic evaluations requires knowledge of the heritabilities of individual FTIR wavelength ab- sorbances. Previous FTIR heritability estimates have been based on relatively small sample sizes and have not considered the possibility that heritability may vary across parities and stages of the lactation. We used data from ~370,000 test-day records of Canadian Holstein cows to produce a landscape of the heritability of FTIR spectra, 1,060 wavelengths in the near- and mid-infra- red spectrum (5,011–925 cm−1), by parity and month of the lactation (mo 1 to 3 and mo 1 to 6, respectively). The 2 regions of the spectrum associated with absorp- tion of electromagnetic energy by water molecules were estimated to have very high phenotypic variances, very low heritabilities, and very low proportion of variance explained by herd-year-season (HYS) subclasses. The near- or short-wavelength infrared (SWIR: 5,066–3,672 cm−1) region was also characterized by low heritabil- ity estimates, whereas the estimated proportion of the variance explained by HYS was high. The mid- wavelength infrared region (MWIR: 3,000–2,500 cm−1) and the transition between mid and long-wavelength infrared region (MWIR-LWIR: 1,500–925 cm−1) harbor several waves characterized by moderately high (≥0.4) heritabilities. Most of the high-heritability regions contained wavelengths that are reported to be associ- ated with important milk metabolites and components. Interestingly, these 2 same regions tended to show more variability in heritabilities between parity and lacta- tion stage. Second parity showed heritability patterns that were distinctly different from those of the first and third parities, whereas the first 2 mo of the lactation had clearly distinct heritability patterns compared with mo 3 to 6.
A landscape of the heritability of Fourier-transform infrared spectral wavelengths of milk samples by parity and lactation stage in Holstein cows
Cecchinato, A.;Bittante, G.;Toledo-Alvarado, H.;
2019
Abstract
Fourier-transform near- and mid-infrared (FTIR) milk spectral data are routinely collected in many coun- tries worldwide. Establishing an optimal strategy to use spectral data in genetic evaluations requires knowledge of the heritabilities of individual FTIR wavelength ab- sorbances. Previous FTIR heritability estimates have been based on relatively small sample sizes and have not considered the possibility that heritability may vary across parities and stages of the lactation. We used data from ~370,000 test-day records of Canadian Holstein cows to produce a landscape of the heritability of FTIR spectra, 1,060 wavelengths in the near- and mid-infra- red spectrum (5,011–925 cm−1), by parity and month of the lactation (mo 1 to 3 and mo 1 to 6, respectively). The 2 regions of the spectrum associated with absorp- tion of electromagnetic energy by water molecules were estimated to have very high phenotypic variances, very low heritabilities, and very low proportion of variance explained by herd-year-season (HYS) subclasses. The near- or short-wavelength infrared (SWIR: 5,066–3,672 cm−1) region was also characterized by low heritabil- ity estimates, whereas the estimated proportion of the variance explained by HYS was high. The mid- wavelength infrared region (MWIR: 3,000–2,500 cm−1) and the transition between mid and long-wavelength infrared region (MWIR-LWIR: 1,500–925 cm−1) harbor several waves characterized by moderately high (≥0.4) heritabilities. Most of the high-heritability regions contained wavelengths that are reported to be associ- ated with important milk metabolites and components. Interestingly, these 2 same regions tended to show more variability in heritabilities between parity and lacta- tion stage. Second parity showed heritability patterns that were distinctly different from those of the first and third parities, whereas the first 2 mo of the lactation had clearly distinct heritability patterns compared with mo 3 to 6.Pubblicazioni consigliate
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