title: Gastrointestinal nematode infection and performance of weaned stocker calves in response to anthelmintic control strategies.
abstract: Gastrointestinal nematode (GIN) parasite control recommendations are in a state of flux because of the increase in anthelmintic resistant cattle parasites, such as Cooperia spp. In addition, Cooperia spp. infection is typically high in warm-season grass pastures and can affect growth performance of grazing stocker calves in the Gulf Coast Region. This study evaluated the effects of moxidectin pour-on, oxfendazole oral suspension, or a combination of the two given at separate times on infection and performance of weaned beef calves grazing summer forages. Steers (n=42) and heifers (n=31) were stratified by sex, d-11 fecal egg count (FEC), and d-1 shrunk body weight (BW) to one of 10 pastures with four anthelmintic treatments and one control. Treatments included: (1) oxfendazole given on d 0 and moxidectin on d 73 (O+M), (2) moxidectin given on d 0 and oxfendazole on d 73 (M+O), (3) moxidectin given on d 0 (M), (4) oxfendazole given on d 0 (O) and (5) no anthelmintic given (CON). Calves grazed for d-110 beginning May 27th. Response variables were FEC (collected on d-11, 14, 31, 45, 59, 73, 87 and 108), coprocultures (evaluated for d 87 and 108), final shrunk BW, shrunk BW gain, average daily gain (ADG), and full BW gain (collected on d 31, 59, 73, 87, and 108). Calves treated with either oxfendazole (O+M and O) or moxidectin (M+O and M) on d 0 had significantly lower (P<0.001) FEC than the CON calves on d 14, 31 and 45. However, the M+O treated calves had significantly higher (P<0.001) FEC than both oxfendazole treated groups. In addition, calves treated with a second dewormer on d 73 (O+M and M+O) had significantly lower (P<0.001) FEC by d 87 than the CON or M treated calves. Shrunk BW gain and ADG were significantly greater (P=0.005) for the O+M compared to the M treated and CON calves, but comparable with the M+O and O treated calves, respectively. Coprocultures sampled on d 87 and 108 for calves not receiving a second dewormer were predominantly Cooperia spp. and Ostertagia spp. On d 87, no larvae were recovered from the M+O treated calves, whereas the O+M treated calves had 94% Cooperia spp. and 3% Ostertagia spp. recovered. Providing a benzimidazole with a macrocyclic lactone given at two different periods may provide better GIN parasite control and improve animal gains for stocker calves grazing warm-season grass pastures.
authors: Louisiana State University Agricultural Center, Hill Farm Research Station, 11959 Highway 9, Homer, LA 71040, United States. rswalker@agcenter.lsu.edu
authors: R S
authors: RS
authors: Walker
authors: J E
authors: JE
authors: Miller
authors: C J
authors: CJ
authors: Monlezun
authors: D
authors: D
authors: LaMay
authors: C
authors: C
authors: Navarre
authors: D
authors: D
authors: Ensley
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D001562:Benzimidazoles / Q000008:administration & dosage / Q000627:therapeutic use*; D001835:Body Weight; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000469:parasitology*; D004359:Drug Therapy, Combination; D005260:Female; D005767:Gastrointestinal Diseases / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D018942:Macrolides / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*
chemical_list: D000871:Anthelmintics; D001562:Benzimidazoles; D018942:Macrolides; C027837:moxidectin; C011030:oxfendazole
keywords: Anthelmintic resistance; Benzimidazoles; Cooperia; Macrocyclic lactones; Ostertagia; Stocker calves