Abstract
BackgroundWith concerns over the development of anthelmintic resistance in cattle nematode populations, we must re-examine our approach to nematode control in cattle. Targeted selective treatments (TST), whereby individual animals are treated instead of entire groups, are being investigated as an alternative. The study objective was to determine if anthelmintic usage could be reduced using a TST-based approach to nematode control in spring-born suckler beef cattle over their first and second grazing seasons (SGS) without affecting performance. In the first grazing season (FGS), 99 calves with an initial mean (s.d.) calf age and live weight on day 0 (June 28th 2012) of 107 (23.1) days and 160 (32.5) kg, respectively, were used. The study commenced on day 0 when calves were randomised and allocated to one of two treatments; 1), standard treatment (control) and 2), TST. Control calves were treated subcutaneously with ivermectin on days 0, 41 and 82 in the FGS. All calves were treated with ivermectin on day 124 and housed on day 133. In the SGS, only heifer calves from the FGS were used and control heifers were treated with ivermectin on day 393. Animals were weighed, blood and faecal sampled every three weeks. The TST animals were treated with ivermectin if thresholds based on a combination of plasma pepsinogen concentrations, faecal egg count and/or the presence of Dictyocaulus viviparus larvae in faeces (FGS only) were reached.ResultsNo TST calves reached the treatment threshold criteria in the FGS. The FGS average daily live weight gain (ADG ± s.e.m.) for control and TST group calves was 0.89 ± 0.02 kg and 0.94 ± 0.02 kg day−1, respectively (P = 0.17). In the SGS, all heifers were treated with ivermectin on day 431 due to clinical signs of respiratory disease. The ADG for control and TST heifers from turnout on day 321 to day 431 was 0.90 ± 0.04 and 0.80 ± 0.04 kg day−1, respectively (P = 0.03).ConclusionsSpring-born FGS suckler beef calves require minimal anthelmintic treatment to maintain performance. In contrast, clinical parasitic disease may develop in the SGS unless appropriate anthelmintic treatment is provided.
Highlights
With concerns over the development of anthelmintic resistance in cattle nematode populations, we must re-examine our approach to nematode control in cattle
We reported that springborn suckler beef calves did not require anthelmintic treatment during the first grazing season (FGS) under Irish conditions [3], provided appropriate control measures were taken to prevent dictyocaulosis from occurring
Anthelmintic usage, animal performance in the FGS Six calves were removed from the study during the FGS due to the following reasons; 1) two calves were removed due to lameness, 2) one calf died due to acute peritonitis, 3) one calf had diarrhoea and was ill-thrifty, 4) the dam of one calf was identified as a tuberculosis reactor using the intradermal skin test and was removed from the herd, and 5) the dam of one calf developed severe lameness so could not effectively nourish the calf
Summary
Anthelmintic usage, animal performance in the FGS Six calves (three control and three TST) were removed from the study during the FGS due to the following reasons; 1) two calves were removed due to lameness, 2) one calf died due to acute peritonitis, 3) one calf had diarrhoea and was ill-thrifty, 4) the dam of one calf was identified as a tuberculosis reactor using the intradermal skin test and was removed from the herd, and 5) the dam of one calf developed severe lameness so could not effectively nourish the calf. The ADG for control and TST group heifer calves during the FGS was 0.92 ± 0.03 and 0.89 ± 0.03 kg day−1, respectively (P = 0.94). Two other TST heifers exhibited clinical signs of respiratory disease (coughing and tachypnoea) on day 428 Both heifers were clinically examined and individual rectal faecal samples were collected and subsequently examined for the presence of lungworm larvae. Both were treated on day 428 with ivermectin and amoxicillin (1.0 ml per 10 kg bodyweight, Betamox LA 150 mg/ml Suspension for Injection, Norbrook Laboratories Limited). At sampling on day 468 at the end of the SGS, four heifers were serologically positive (three TST and one control)
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