(Co)variance component estimates for milk composition traits in Sarda dairy sheep using a bivariate animal model

Sanna, S.R.; Carta, Antonello; Casu, S.

doi:10.1016/s0921-4488(96)00949-2

Cited by 38 publications

(29 citation statements)

References 9 publications

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“…Genetic parameters of production traits were consistent with sheep literature [3,4,34]. The heritability estimate of lactation mean SCS of 0.15 was in agreement with the only available value of 0.12 estimated in ewes [17] and with the average value of 0.15 provided by more recent studies in dairy cattle [10,27,33].…”

Section: Discussionsupporting

confidence: 88%

Genetic analysis for mastitis resistance and milk somatic cell score in French Lacaune dairy sheep

et al. 2001

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-Genetic analysis for mastitis resistance was studied from two data sets. Firstly, risk factors for different mastitis traits, i.e. culling due to clinical or chronic mastitis and subclinical mastitis predicted from somatic cell count (SCC), were explored using data from 957 first lactation Lacaune ewes of an experimental INRA flock composed of two divergent lines for milk yield. Secondly, genetic parameters for SCC were estimated from 5 272 first lactation Lacaune ewes recorded among 38 flocks, using an animal model. In the experimental flock, the frequency of culling due to clinical mastitis (5%) was lower than that of subclinical mastitis (10%) predicted from SCC. Predicted subclinical mastitis was unfavourably associated with the milk yield level. Such an antagonism was not detected for clinical mastitis, which could result, to some extent, from its low frequency or from the limited amount of data. In practice, however, selection for mastitis resistance could be limited in a first approach to selection against subclinical mastitis using SCC. The heritability estimate of SCC was 0.15 for the lactation mean trait and varied from 0.04 to 0.12 from the first to the fifth test-day. The genetic correlation between lactation SCC and milk yield was slightly positive (0.15) but showed a strong evolution during lactation, i.e. from favourable ( 0.48) to antagonistic (0.27). On a lactation basis, our results suggest that selection for mastitis resistance based on SCC is feasible. Patterns for genetic parameters within first lactation, however, require further confirmation and investigation.dairy sheep / somatic cell count / mastitis / genetic parameters / risk factors

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Section: Discussionsupporting

confidence: 88%

Genetic analysis for mastitis resistance and milk somatic cell score in French Lacaune dairy sheep

et al. 2001

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“…Heritability and repeatability estimated for milk yield from this study (0.26 and 0.38) coincided with the other results previously reported for the same breed [12,17] and other dairy ewes [42,44]. Estimates for fat content remained low in spite of precautions taken in sampling and milk analysis at our dairy plant.…”

Section: Heritability and Repeatability Coefficientssupporting

confidence: 90%

Genetic parameters for lactation traits of milking ewes: protein content and composition, fat, somatic cells and individual laboratory cheese yield

et al. 2002

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-The effects of some environmental variation factors and the genetic parameters for total milk traits (fat content, protein content, casein content, serum protein content, lactation mean of individual laboratory cheese yield (LILCY), lactation mean of somatic cell count (LSCC), and milk yield) were estimated from the records of 1 111 Churra ewes. Genetic parameters were estimated by multivariate REML. Heritability for fat content was low (0.10) as is usually found in the Churra breed. Heritabilities for protein content, casein content, serum protein content, LILCY, milk yield and somatic cell count were 0.31, 0.30, 0.22, 0.09, 0.26 and 0.11, respectively. The highest heritability estimates were for protein and casein contents. Casein content is not advisable as an alternative to protein content as a selection criterion for cheese yield improvement; it does not have any compelling advantages and its measurement is costly. Our results for LSCC indicated that efforts should focus on improving the level of management rather than selecting for somatic cells, in the actual conditions of the Churra breed.

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“…Serrano et al (2003) recently reported a heritability estimate of 0.18 for standardised milk yield (120 days) in Manchega ewes. However, heritability estimated for total milk yield in native Spanish dairy sheep breeds such as those of 0.23 and 0.24 for the Churra breed (ElSaied et al, 1998a;Othmane, 2000) and 0.20 and 0.21 for the Latxa breed (Ugarte et al, 1996;Legarra and Ugarte, 2001) are usually higher than those reported here Table 4 Genetic, permanent environmental, residual and phenotypic covariances and genetic (r g ), permanent environmental (r c ) and phenotypic (r p ) correlations among lactation length (LL) in days, 180 days adjusted milk production (MY 180 Barillet, 1997) or Sarda (0.30; Sanna et al, 1997). However, Portolano et al (2001), in Barbaresca siciliana sheep, reported heritability estimates for milk yield standardised to different lactation lengths that always ranged from 0.14 to 0.15 and Nikolau et al (2004) reported different estimates for total milk yield in Lesbos dairy sheep ranging from 0.16 to 0.20.…”

Section: Resultsmentioning

confidence: 75%

Genetic parameters affecting 180-days standardised milk yield, test-day milk yield and lactation length in Spanish Assaf (Assaf.E) dairy sheep

Gutiérrez

Legaz²,

Goyache

2007

Small Ruminant Research

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A total of 42,197 records of test-day milk yield (TDY) and 7654 lactations from 3854 individuals belonging to the Spanish Assaf (Assaf.E) breed were analysed using univariate and multivariate models to estimate genetic parameters affecting TDY, total milk yield standardised to 180 days (MY 180 ) and lactation length (LL) in order to asses their possibilities of use in the selection scheme of the Assaf.E population. Estimates of h 2 were, in general, on the lower limit of those usually reported for the three analysed traits. Estimates of heritability for MY 180 varied from 0.131 to 0.177. Estimates of h 2 for LL and TDY were consistent regardless the estimation model being of, roughly, 5% and 10%, respectively. The estimates for the permanent environmental effect (c 2 ) of TDY were consistently the same (0.27-0.28) regardless the fitted model whilst they showed large differences for LL and MY 180 . Genetic correlations were always positive and high ranging from 0.792 for the pair LL-TDY to 0.999 for the pair MY 180 -TDY. Correlations between permanent environmental effects were even higher ranging from 0.932 for the pair LL-MY 180 and 0.999 for the pair MY 180 -TDY. The advantages of using TDY as selection criterion in the Assaf.E improvement scheme are discussed.

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(Co)variance component estimates for milk composition traits in Sarda dairy sheep using a bivariate animal model

Cited by 38 publications

References 9 publications

Genetic analysis for mastitis resistance and milk somatic cell score in French Lacaune dairy sheep

Genetic analysis for mastitis resistance and milk somatic cell score in French Lacaune dairy sheep

Genetic parameters for lactation traits of milking ewes: protein content and composition, fat, somatic cells and individual laboratory cheese yield

Genetic parameters affecting 180-days standardised milk yield, test-day milk yield and lactation length in Spanish Assaf (Assaf.E) dairy sheep

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