1,720,995 research outputs found
International genetic evaluation for fertility traits in dairy cattle
No full textThe objective of this study was to review and discuss the results of the first international evaluation for female fertility of Holstein dairy cattle. Fifteen countries, including Italy, provided breeding values of bulls and joined the evaluation. Four trait groups were used to analyze animal's ability to became pregnant and animal's ability to recycle after calving. Italy submitted three traits: days to first service (DTFS), non-return rate at 56 days (NR56) and calving interval (CI). Genetic correlation between Italy and the other countries ranged from 0.72 to 0.94 for DTFS, from 0.25 to 0.90 for NR56 and from 0.67 to 0.87 for CI. Results represent another step forward in the international trade of dairy cattle genetic material
The accuracy of test day model evaluation for the Italian Holstein
No full textGenetic evaluation for production traits in the Holstein breed in Italy has been based on a Random Regression Test Day Model (RRTDM) since November 2004. More specifically, the model is a multiple lactation, multiple trait RRTDM, similar to the model used in Canada for official genetic evaluation. Fixed regression curve effect include time, region, age at calving, parity and season of calving. Last changes in the model included a new definition of the proof scale and of the genetic base. The accuracy of the model was assessed by analyzing residuals and testing Mendelian sampling trends. Residuals were normally distributed for all traits and had zero mean. Residual trends for all the effects included in the model were analyzed also for effects not included in the model like number of milkings per day and number of days pregnant at the test date. Mendelian sampling did not show any significant trend over time both for cows and bulls
Improving the stability of test day model evaluation for production traits in the Italian Holstein
No full textGenetic evaluation for production traits in the Holstein breed in Italy is based on a Random Regression Test Day Model (RRTDM) since November 2004. More specifically the model is a multiple lactation, multiple traits RRTDM, similar to the model used in Canada for official genetic evaluation. In order to improve stability, data were pre-adjusted for number of days pregnancy at test day and fixed regression curve effects include now the effect of year of production, four calving seasons instead of two and a general effect for days in milk (DIM) was added. The changes in the model improved stability of proofs over time, thus increasing the ability of the test day to accurately predict the breeding value of both bulls and cows. Trend validation results showed also improvements and residuals were positively affected by the changes. Trends in trait residuals previously detected with respect to DIM and month of calving did show a significant reduction. The new model was officially introduced in January 2009
CHANGE OF GENETIC PARAMETERS FOR NATIONAL EVALUATIONS OF ITALIAN HOLSTEIN AND EFFECT ON INTERNATIONAL PROOFS
No full textPROCEEDINGS OF THE OPEN SESSIO
EFFECT OF LIVE WEIGHT, DAILY GAIN AND PARENT AVERAGE FOR ILQM ON TIME FOR PROGENY TESTING OF ITALIAN FRIESIAN YOUNG BULLS
No full textConsequences of differences in pricing systems between regions on economic values and revenues of a national dairy cattle breeding scheme in Italy
No full textProfit equations were used to determine the relative importance of different mil yield traits, with and without product limitations. Economic value were calculated for three different Italian payment systems: the “average” payment system emplyed by Unalat [Unalat, 1995. Accordo interprofessionale per la determinazione del prezzo del latte per il periodo dal 174/1994 al 31/3/1995. Roma, Italy. P.10 (personal correspondence).], payment system in areas of Parmesan cheeseproduction, and the payment system that is used in deriving the current economic weights. The Parmesan payment system resulted in the highest marginal value of milk with average composition in situations without herd output limitation. With aherd output limitation considering milk yield and fat content, marginal value decreased by 47 to 52%. The economic value of fat relative to that of protein ranged from -0.031 to 0.135 without herd output limitation and -0.432 to -0.020 with herd output limitation. The relative economic value of carries ranged from -0.012 to 0.07 without and -0.020 to 0.042 with herd output resctriction. The sensitivity analysis revealed taht the average herd yield levels for fat, and especially protein, are the main factors influencing the relative economic values. Losses, which occured from and economic repsonse of a breeding scheme due to changes in pricing systems ranged from 4.2 to 16.7%, whereas with the herd output limitation losses up tp 57.0% were found. Losses in economic response to selection indicated that there is potential for diversification of the breeding goal. The benefits of diversification at the population level have to be balanced against the costs of running a larger selection programme in deciding on a longer-term selection policy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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