Systemic prepartum treatment of end-term dairy heifers with penethamate hydriodide: effect on udder health, milk yield, and culling until 120 days in milk.
Prepartum intramammary treatment with antimicrobials of end-term dairy heifers has frequently been proposed as a practice to reduce the prevalence of intramammary infections (IMI) at calving. From a safety standpoint for both animal and administrator, systemic treatment is preferred. A clinical trial was conducted on heifers from 10 well-managed, commercial dairy farms with a low prevalence of heifer mastitis. The aim was to assess both the short- and long-term effects of a systemic prepartum therapy with penethamate hydriodide on udder health and milk production. Because it was hypothesized that some herds would benefit more from this treatment than others, specific herd-level information was collected before the start of the actual trial to screen for and explain potential herd-specific treatment effects. Further, the effect of treatment on antimicrobial susceptibility of staphylococcal isolates was monitored. End-term heifers were either treated systemically (over 3 consecutive days) 2 wk before expected calving date with penethamate hydriodide (n=76) or remained untreated (n=73). Systemic prepartum treatment of end-term heifers with penethamate hydriodide resulted in fewer IMI in early lactation. However, all 6 cases of clinical mastitis in early lactation occurred in the treatment group [Streptococcus uberis (n=1), Corynebacterium bovis (n=1), Staphylococcus aureus (n=1); 1 sample was contaminated; 2 samples remained culture negative]. No long-term treatment effects (from 4 to 120 d in milk) on milk production, udder health, or culling hazard during later lactation were detected, although treated heifers belonging to herds classified as having low-yielding heifers out-produced the control heifers. Moreover, penicillin susceptibility of staphylococci isolated from milk samples of treated or control heifers did not differ. Herds with a low prevalence of heifer mastitis are not likely to benefit from prepartum systemic antimicrobial treatment of the end-term heifers.
Independent Dairy Consultant, Milk@vice, 8820 Torhout, Belgium; M-team and Mastitis and Milk Quality Research Unit, Department of Reproduction, Obstetrics, and Herd Health, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium. Electronic address: pieter.passchyn@telenet.be.
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De Vliegher
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002417:Cattle; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000382:microbiology*; D008414:Mastitis, Bovine / Q000188:drug therapy*; D008892:Milk / Q000382:microbiology*; D010400:Penicillin G / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011247:Pregnancy; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000662:veterinary*; D013210:Staphylococcus / Q000187:drug effects / Q000302:isolation & purification; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; C008780:penethamate hydroiodide; D010400:Penicillin G
clinical trial; heifer mastitis; penethamate hydriodide; prepartum treatment