Search results for "test-day"
showing 5 items of 5 documents
Effects of different simplified milk recording methods on genetic evaluation with Test-Day animal model
2007
The aims of the present study were to compare estimated breeding values (EBV) for milk yield using different testing schemes with a test-day animal model and to evaluate the effect of different testing schemes on the ranking of top sheep. Alternative recording schemes that use less information than that currently obtained with a monthly test-day schedule were employed to estimate breeding values. A random regression animal mixed model that used a spline function of days in milk was fitted. EBVs obtained with alternative recording schemes showed different degrees of Spearman correlation with EBVs obtained using the monthly recording scheme. These correlations ranged from 0.77 to 0.92. A redu…
Suitability of simplified milk recording methods for genetic evaluations using test-day models in dairy sheep
2008
Nowadays in dairy sheep, test-day records are collected monthly under an alternate morning/evening system. This alternate system was implemented because of the steady increase in recording cost per sheep observed in the last few decades. Furthermore, additional modifications to the testing schemes have been proposed to reduce the costs of milk recording. In dairy sheep, the cost for milk recording is indeed too high compared both with individual outputs and with other dairy species. Therefore, the purposes of the present study were: i) to compare estimated breeding values (EBVs) for milk yield using different simplified testing schemes with a test-day sire model; ii) to evaluate the effect …
Trend in dairy sheep BLG genotype found with repeatability test-day model.
2007
A total of 19.207 test-days, collected on 4 farms from 1999-2006 and belonging to 1109 Valle del Belice dairy sheep were analyzed with a repeatability model. After strict outlier analysis 17.747 records were retained. Animals were reared in an extensive system resulting in large environmental influences. However, significant genetic variation was detected in production traits (milk production mean=1336 stdg=93 g/d, fat+protein 167 stdg=12 g/d). Heritability was only 3% while the interaction year by month of test-day explained 27% of the variation. A protein and DNA analysis program was initiated in order to facilitate selection to maintain these flocks under these conditions. In total 427 a…
Test-Day Model Heritabilities for somatic cvell score and production traits in primiparous Valle del Belice sheep
2006
A repeatability test-day animal model was used to investigate heritabilities of somatic cell score (SCS) and milk production traits in Valle del Belice sheep. The heritability estimate for SCS falls within the range reported in literature (0.14±0.03), while estimates for milk production and composition traits were below those obtained by others, 0.12±0.03, 0.09±0.02, 0.14±0.03, 0.14±0.03, and 0.12±0.03, respectively, for milk yield, fat %, fat yield, protein %, and protein yield. Flock-test-day had a substantial effect on milk production traits but not on SCS. These results provide the basic parameters required for discussion of selection strategies and objectives in Valle del Belice sheep.