Abstract
Few studies have focused on assessing Salmonella infection in the nursery and its role in further pig production periods. Mesenteric lymph nodes, intestinal content, and meat juice from 389 6-week-old male piglets intended for human consumption from five breeding farms and 191 pooled floor fecal samples from gilt development units (GDU) from the same farms were analyzed to estimate and characterize (by pulsed-field gel electrophoresis and antimicrobial resistance analyses) Salmonella infection. The prevalence of infection and shedding among piglets was 36.5% and 37.3%, respectively, shedding being significantly associated with infection (Odds Ratio = 12.7; CI 7.3–22.0). Salmonella Rissen; S. 4,[5],12:i:-; and S. Derby were the most common serotypes. A low level of Salmonella-specific maternal antibodies at the beginning of the nursery period suggested it was a period of high risk of infection. Resistance to 3rd- and 4th-generation cephalosporins was detected in piglet isolates although the piglets never received antibiotics, indicating they could be vectors of antimicrobial resistance. The same Salmonella clones were detected in piglet and GDU isolates, suggesting that infected piglets play a significant role in the infection of gilts and consequently of finishing pigs in the case of production farms. The control of Salmonella infection in nursery piglets may decrease the risk of abattoir and carcass contamination.
Highlights
Salmonella infection is quite common in pigs in the European Union [1]
Few studies have focused on the periods previous to this one, such as the nursery, active Salmonella infections have been identified in pig nurseries [7]
The median optical density percentage (OD%) value for the 389 sampled animals was 4.7
Summary
Salmonella infection is quite common in pigs in the European Union [1]. It usually courses asymptomatically, but infected pigs may shed the bacterium through their feces, making them a major risk factor for carcass contamination at slaughter [2]. The so-called nursery is a period that comprises the time from weaning at 3–4 weeks of age to approximately 10 weeks of age (just before entering the growing unit) This is a critical production phase in which piglets are very susceptible to a variety of enteric infections. A common consequence of weaning is the modification of the piglets’ intestinal microbiota, characterized by a significant reduction in the number of lactobacilli [8], mostly due to sudden changes in their diet, which goes from mostly liquid (sow milk) during lactation to a solid-based diet (prestarter feed) at the beginning of the nursery, and environment [9] These changes, along with the decay of maternal antibodies [10], the only immune protection at this age, and the usual animal stress linked to the piglet’s separation from its dam and its commingling with new piglets, make weaned piglets highly prone to
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