Evaluation of careers and performances of goats with extended lactations

Abstract

In France, the use of extended lactations (EL: more than 485 days of continuous lactation in the absence of parturition) has been developed and diversified to meet farmers’ objectives: management of out-of-season production, staggering production, management of career endings. The study has been carried out to describe EL diversity and performance at the career level. The analysis was based on monitoring data from 1998 to 2016 and involved 739,566 goats from 2103 herds (Alpine, Saanen or crossbred goats). Careers were distinguished according to the existence or not of at least one normal lactation (NL: more than 250 days), the achievement and positioning of EL during animal life. The number of milking days and the cumulative production were compared within first kidding cohorts. In the studied goats, the career spanned from one to 14 lactations. 16.4 % of the goats achieved at least one EL in their career and in more than 90 % of the cases, only one EL. The average EL duration reached 717 days but differed according to the positioning of EL: from 649 days (EL at the beginning of the career) to 782 days (EL at the end of the career or single EL). Differences were observed at the career level on adjusted averages of the number of milking days: 841 to 1845 days, i.e. a factor of 1.10 to 1.79 times the average duration obtained by the goats of the same cohort. Over this period, cumulated productions varied on adjusted average from 2350 to 5704 liters, i.e. a production of 2.73 to 3.01 liters/day compared to 2.68 for the reference goats. Finally, at the career level, no significant difference of milk somatic cell counts means was found between categories (excluding goats without NL). Nevertheless, somatic cell counts were increased during the EL itself. Studies remain to be conducted to clarify the existence of antagonism or not between production, milk persistence and fertility.