Influence of a Moxidectin treatment in ewes of two German sheep breeds on the growth rate of their lambs

The aim of the present study was to evaluate the effect of an anthelmintic treatment in ewes (n = 133) of two German sheep breeds (German Black Head Mutton and Leine sheep) on the average daily weight gains (ADW) of their lambs (n = 180). Eight weeks prior to the lambing season ewes were randomly divided into two groups: (1) no anthelmintic treatment, (2) Moxidectin (Cydectin®, Forte Dodge, USA) treatment. Starting at birth, body weights of lambs were recorded every other week until 12 weeks of age. Ewes faecal egg count (FEC) was measured 8 weeks after lambing to monitor the efficiency of anthelmintic treatment. Log FEC was significantly lower (P < 0.001) in Moxidectin-treated ewes compared to Moxidectin-untreated ewes. German Black Head Mutton tended (P = 0.212) to have higher log FEC compared to Leine sheep (3.08±0.29 vs. 2.46±0.39). Average daily weight gains were significantly higher in German Black Head lambs compared to Leine lambs (P < 0.001), and in single born lambs compared to multiples (P < 0.001). Furthermore, in single born German Black Head Mutton lambs average daily weight gains were significantly higher (P < 0.05) in the Moxidectin-treated group compared to single born lambs in the untreated group. Gastrointestinal nematode infections tended to be less severe in Leine sheep. The anthelmintic treatment did not influence growth rates of Leine lambs, suggesting a potentially higher nematode resistance or tolerance in this breed. In German Black Head Mutton, single born lambs from Moxidectin-treated ewes had higher growth rates compared to single born lambs from untreated ewes, whereas no differences could be observed between lambs from treated and untreated ewes that had more than one lamb. These findings may be a consequence of differences in intake of milk, concentrate, and hay.