Effects of anthelmintic treatment on milk production in Sarda dairy ewes naturally infected by gastrointestinal nematodes

The objective of this work was to investigate the effects of a single anthelmintic treatment on milk production. In 2008, in a flock of Sarda ewes naturally infected by gastrointestinal nematodes, 162 adult and 72 primiparous ewes were allocated into four groups. For each age class, one group was drenched with albendazole after lamb weaning whilst the other was left untreated as control. The efficacy of single anthelmintic treatment at the beginning of lactation was obtained by a faecal egg count reduction test. The effect of drenching on milk yield and components was studied both using single test date and lactation records. After 1 month geometric mean of eggs per gram of treated ewes decreased up to 1% of the initial value (3.40 eggs/g versus 322.63 eggs/g in primiparous and 2.14 eggs/g versus 312.70 eggs/g in adult ewes). The anthelmintic treatment showed a significant effect only on lactation milk yield of treated adult ewes that produced 19.2 L/year more than control ewes. Production level was investigated as a criterion to apply targeted selective treatment. High producer multiparous ewes produced 32.7 L/year more than control ones. Overall results confirm a beneficial effect of anthelmintic treatment on milk production without any detrimental effect on milk composition only on adult ewes markedly if high producers. Thus, depending on milk price and the required length of the period of discarded milk, the increased milk yield can counterbalance treatment’s costs.