Grouping strategies and lead factors for ration formulation in milking ewes of the Chios breed

Abstract The aim of this study was to develop an efficient strategy for ration formulation for milking ewes of the Chios breed in Greece. The strategy involved two and three groupings according to production level and challenge feeding using lead factors. Lead factors, that adjust upwards the average production of a flock or a group of ewes, were calculated for the 83rd and the 90th percentile, using 49,237 milk test-day records from 549 flock-test-days, referring to 64 flocks and 97 complete lactations. Lead factors were 1.25 for the single-group, 1.14 and 1.17 for the two-group, and 1.11, 1.07 and 1.15 for the three-group strategy for the 83rd percentile. Regarding the 90th percentile, these were: 1.33 for the single-group, 1.18 and 1.19 for the two-group, and 1.15, 1.09 and 1.16 for the three-group strategy. Analysis of variance was used to assess the influence of several effects on lead factors. Flock-year and mean and standard deviation milk yield were significant (P   250 kg of milk/ewe/year) and low (

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