Introduction

Taeniasis and cysticercosis are important zoonotic infections involving humans and swine, where pigs are the common intermediate hosts (Sato et al. 2006). The disease is highly endemic in Latin America, Asia, and Africa (Ito et al. 2003). Cysticercosis in pigs is also a cause of carcass condemnations particularly in heavy infection, constituting an economical problem. In the field, diagnosis of cysticercosis is made through tongue inspection. This examination can be performed in live swine and aims to find superficial cysts. Even though this technique is commonly used, it is characterized by low sensitivity and specificity (Sato et al. 2003), usually only effective in pigs with heavy infections. In addition, it has been suggested that this method stress and hurts the animal (Herrera-García et al. 2007), but no scientific evidence has been documented to support this assertion. The objective of this study was to find the influence of tongue inspection on some physiological and behavioral stress measures in pigs at different weights.

Material and methods

Twenty-seven Landrace/York male pigs were randomly assigned to one of three experimental groups. In the first group (T1), pigs were held for a minute in standing position by the use of a pig snout noose. Animals in T2 were held as in T1, but their mouth was opened by the aid of a wooden rod twisted across the upper and lower jaw and the tongue was gently pulled out using a piece of a cotton cloth, exposing the inferior surface of the tongue to simulate its examination for cysticerci, while in T0 (controls), none of the procedures described above were performed. Treatments were applied at 60 and 90 kg in the same animals, which correspond to market weight pigs in Mexico. Behavioral and physiological stress-related variables were measured including: resistance to be held (according to a five-point system, ranging from 1 = no movement to 5 = violent struggling), vocalizations (registering the number of vocalizations regardless of duration or intensity), time to approach the feeder (after being released from the snout noose was measured), serum cortisol concentration (blood samples were collected 15 min after treatment and analyzed by RIA), and heart rate (difference in HR observed between the minute before and immediately after treatment application).

A two-way analysis of variance (2 × 3) was used. The analysis compared differences between weights (factor A), effect of treatment (factor B), and interactions.

Results and discussion

Resistance to be handled and serum cortisol concentration were higher (P < 0.05) than those from T0 in T1 and T2 groups, for 60- and 90-kg pigs. Time to return to the feeder observed the same pattern than the previous variables in 60-kg pigs, but T1 and T0 were similar (P > 0.05) for the heavier animals (Table 1). These results are in accordance with the findings of Gavernick et al. (2002) who have also reported an increase in blood cortisol concentration, when pigs were restrained by the use of a nose sling. However, the finding that tongue inspection did not build up a significant amount of stress with respect to T1, displaying only higher values in vocalizations emitted by 90-kg pigs (Table 1), did not support the empirical statement that tongue inspection is an stressful method greater than the effect induced by the use of the snout noose.

Table 1 Some behavioral and physiological stress measures due to handling and tongue inspection during cysticercosis diagnosis in pigs
Full size table

Ruis et al. (1997) found that the capacity of the hypothalamic drive to respond to ACTH decreases with age. Even though Tummaruk et al. (2009) found an association between weight and age, in the present experiment, no difference was found in serum cortisol concentration between 60- and 90-kg pigs, perhaps due to the lack of age control and individual differences (Gavernick et al. 2002) that contributed to the large variations observed. Future research is necessary to establish if tranquilization could improve swine welfare during tongue inspection, increasing efficiency during cysticercosis diagnosis without compromising easy handling. It was concluded that the use of snout noose induces major changes in some behavioral and physiological measures of stress in swine, while the opening of the mouth including tongue inspection does not contribute significantly to this effect.