Associations between infectious bovine keratoconjunctivitis at weaning and ultrasongraphically measured body composition traits in yearling cattle

• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 1, 2014, págs. 100-106
• Idioma: inglés
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• Resumen

  • Objective�To assess associations between infectious bovine keratoconjunctivitis (IBK) diagnosed at weaning and production traits in yearling beef calves.

    Design�Retrospective population-based cohort study.

    Animals�1,882 Angus calves.

    Procedures�Angus calves from 1 farm were evaluated over 7 years. The association between yearling body production traits and detection of IBK lesions at weaning was evaluated.

    Results�Yearlings that had evidence of IBK at weaning had less 12th rib fat depth, ribeye area, and body weight than did cohorts without evidence of IBK. Average daily gain was greater in cattle that had IBK lesions at weaning, but this did not offset lower body weight at weaning.

    Conclusions and Clinical Relevance�The associations between IBK at weaning and production variables persisted well into the postweaning period, and there appeared to be a relationship between decreased body composition traits at yearling evaluation and IBK infection before weaning.

    Infectious bovine keratoconjunctivitis, commonly referred to as pinkeye, is one of the most important ocular diseases in cattle worldwide.1 Moraxella bovis is widely considered to be the primary causative agent of IBK, although other organisms have been mentioned as possible causative agents.2 Although cattle of all ages can be affected by IBK, most cases occur in cattle between 2 and 12 months of age. Cattle with IBK have clinical signs that include lacrimation, photophobia, corneal edema, ocular pain, and corneal ulceration. Although most cattle recover from IBK without serious sequelae, corneal scarring and vision loss can be permanent sequelae to acute infection.3 Infectious bovine keratoconjunctivitis lesions have been associated with mean weaning weight losses of 17 kg (37.4 lb) in bulls and 18 kg (39.6 lb) in heifers in a 1974 study4 as well as a mean 31-kg (68.2-lb) loss for the 365-day adjusted weight in the bulls that continued on a feed trial. More recently, a randomized and masked field trial5 found mean losses at weaning in spring of 8.2 kg (18.04 lb; 95% CI, 4.04 to 12.52 kg [8.89 to 27.54 lb]).

    Animal suffering and decreased weaning weight associated with IBK are likely the most important motivators for adoption of management practices to control IBK. However, it is unclear whether the production losses reported at weaning carry over to the postweaning production stage. Evidence that losses from IBK carry over to the postweaning periods would imply that cattle with evidence of IBK such as corneal scarring might reasonably be discounted at sale, further increasing the economic cost of IBK to producers. Alternatively, if the losses that occur before weaning are regained after weaning, perhaps because of the phenomenon of compensatory gain, discounting the value of calves with IBK lesions would not be necessary. Further, evidence that IBK could affect yearling trait measurements would imply that IBK could have influence on replacement selection decisions. Therefore, the aim of the study reported here was to examine whether the occurrence of IBK before weaning was associated with differences in production traits measured in yearlings for breed improvement purposes in cattle.