H. Scott Hurd

Associations between off-label feed additives and farm size, veterinary consultant use, and animal age

Data from the United States National Swine Survey collected by the National Animal Health Monitoring System were used to describe the use of feed additives in swine feeds. Data were collected from 710 farms. The concentration of feed additives expressed in grams per ton of complete feed was described by stage of production, and the use of feed additives above the labeled treatment levels (i.e. off-label) was identified. Of the 3328 feeds, about 79% contained feed additives used in the labeled manner. For all classes of pigs, the prevalence of labeled feed additive use was greater than 75%. Penicillin was used according to its label most often, followed by apramycin, bacitracin, tetracyclines, lincomycin, and tylosin. Carbadox had the highest prevalence of off-label use. Of the 699 feeds that included feed additives in an off-label manner, about 57% included additives at greater than the recommended concentrations or were fed to an incorrect class of pig. About 56% of the feeds had off-label combinations of additives. Small farms were more likely to use rations with no feed additives than intermediate or large farms (P < 0.001). Of those farms using feed additives, the odds of a small farm using all feed additives in the labeled manner was 7.7 times that of an intermediate or large farm (P < 0.0001). After controlling for herd size, producers who used a veterinary consultant were 2.1 times more likely to use feeds with feed additives (P < 0.0001).

A stochastic distributed-delay model of disease processes in dynamic populations

Hurd, H.S., Kaneene, J.B. and Lloyd, J.W., 1993. A stochastic distributed-delay model of disease processes in dynamic populations. Prev. Vet. Med., 16:21-29. 1A simulation model that is applicable to infectious and non-infectious disease is proposed. This paper describes a model for simulation of infectious and non-infectious disease processes in dynamic populations, and compares its behavior to a stochastic version of the Reed-Frost model for a hypothetical infectious disease. A distributed-delay model is applied. Monte-Carlo simulations of both modeling approaches produced epidemics of randomly determined sizes. Although both models demonstrated the characteristic bimodal distributions of total number of cases per epidemic, the shape of the distributions was slightly different. Separation between the two peaks was not as great with the distributed-delay model as with the Reed-Frost model. The tail was slightly more extended than the Reed-Frost, and there were more epidemics in the 50100 case range. Both models produced similar average attack rates.

Management and demographic factors associated with seropositivity to transmissible gastroenteritis virus in US swine herds, 1989–1990

n Abstractn n Serum neutralization testing was used to determine transmissible gastroenteritis (TGE) titers of up to 10 sows per herd (mean 8.7, median 10) for 392 herds that participated in the 3 month monitoring of sows and litters in the National Swine Survey. Of the sampled herds, 101 (25.8%) had sow seroprevalences of at least 80%, 79 (20.1%) had seroprevalences between 10 and 79%, and 212 (54.1%) were seronegative. For evaluation of risk factors for TGE seropositivity, analysis was restricted to herds with at least five tested sows and either 0% or at least 20% seropositive sows. In the logistic regression analysis, a herd was considered seropositive if at least 20% of sampled females had titers of 1: 8 or higher (n = 160), and a herd was seronegative if all females had titers of under 1: 8 (n = 178). Factors considered for inclusion in logistic regression models included breeding herd size, biosecurity measures, pig introductions and movements, and access of possible nonporcine reservoirs to the facilities with pigs. After controlling for the effects of season, number of samples tested and TGE vaccination history, large female breeding herd size (at least 500 sows compared with the reference category of 100–199 sows) and purchase of more than 25 pigs from non-specific pathogen free (SPF) herds were associated with significantly (P<0.05) higher odds of herd seropositivity (odds ratios 4.9 and 3.9, respectively). There was some evidence (P = 0.08) of an increased risk of seropositivity when there were more than two swine herds within a 3 mile radius of the study herd.n n

Slatted pen floors reduce Salmonella in market swine held in abattoirs

The objective of this study was to directly compare Salmonella isolation rates from pig slaughtered after ~ 4 hours holding on slatted or solid concrete floors. Seven truckloads (replicates) of market swine (~ 120 kg) from a fully integrated farrow-to-slaughter operation were studied. At unloading, groups of pigs (15-30) were sorted to 1) no-hold (20-45 minutes waiting), 2) pens with solid concrete floors (~ 4 hours), 3) slatted concrete floors (~ 4 hours). Postmortem samples were cultured for Salmonella. Those pigs held in pens with slatted floors (63.6%) had significantly (P < 0.05) less Salmonella in their ceca than those held on solid floors (72.7%).