Flavour preferences conditioned by protein solutions in post-weaning pigs

The effect of a feed additive supplemented with porcine plasma protein on growth performance and selected biochemical indices of nursing piglets

The aim of this study was to evaluate the health state, performance, and selected serum biochemical indices in nursing piglets after supplementation of a feed additive containing porcine plasma protein in comparison to the control group fed a standard pre-starter feed mixture. The study was carried out in the conditions of industrial farming. Four sows of the Large White swine breed with their litters were included in the study. Piglets were homogenously distributed into control (22) and experimental (24) groups according to weight and sex. Piglets in both groups suckled their mothers' milk. In addition, piglets in the experimental group were also fed a feed supplemented by porcine plasma protein (5%), starting on the third day post partum, whereas piglets in the control group were offered a standard pre-starter feed mixture. We recorded average daily weight gains calculated per the 27-day trial, and body weight at weaning. Clinical findings, mortality, and selected biochemical indices of protein (total immunoglobulins, total protein, albumin, creatinine, urea), and energy (glucose, total cholesterol, total lipids) metabolism were assessed as well. Results of the study showed a significant difference (P < 0.01) in average daily weight gains in the experimental group compared to the control group (0.245 kg and 0.177 kg, respectively). Addition of plasma protein in the experimental group also resulted in a significantly higher serum concentration of total immunoglobulins, total protein and creatinine, and a significantly lower concentration of urea and albumin in this group compared to the control group at weaning.

Palatability in pigs, the pleasure of consumption1

Despite the importance of hedonic reactions in pig's intake, feed palatability has been typically inferred from preference or acceptance measures. However, these measures are influenced by factors beyond palatability, such as energy density and hunger. The aim of this study was to evaluate palatability responses in pigs to sweet and umami taste at different inclusions levels. Pigs (24 per experiment) were video recorded while exposed in pairs to different sucrose (Exp. 1) or monosodium glutamate (MSG, Exp. 2) solutions over seven consecutive 10 min tests (one concentration per day). In both experiments, palatability was estimated through consumption patterns (consumption time per approaches, CT/A), facial expressions (snout openings and tongue protrusions), and consumption during a brief 2 min period. Data were analyzed by sucrose or MSG concentration. Sucrose concentration affected total intake, producing an inverted-U function and a quadratic relationship with sucrose concentration (P = 0.012). In contrast, CT/A and snout openings showed a dose effect (P < 0.005) with a direct correlation between sucrose concentration and CT/A (R = 0.23, P = 0.033) but not for openings (R = 0.18, P = 0.105) where a quadratic relationship appears (P < 0.001). Tongue protrusions and brief consumption time were not affected by sucrose concentration (P = 0.144 and 0.205, respectively). MSG concentration affected consumption, CT/A, snout openings, and brief consumption time (P < 0.001), with significant (P < 0.001) positive correlations (R = 0.59, 0.56, 0.56, and 0.68), respectively. As with rats, CT/A appears to provide a novel and interesting measure reflecting the palatability of preferred ingredients in pigs. However, brief consumption time and orofacial reactions show less similarity between pigs and rodents. Thus further studies are necessary both to better understand the measurement methods themselves and relationship between hedonic reactions and simple consumption in pigs.

An attempt to condition flavour preference induced by oral and/or postoral administration of 16% sucrose in pigs

The present study investigated the acquisition of conditioned flavour preferences in pigs using the caloric value and/or sweet taste of sucrose. Nine water-deprived juvenile pigs were given four three-day conditioning sessions during which they received flavoured solutions as conditioned stimuli (CS). The CS solutions were paired with three treatments that generated a gustatory and/or a caloric reinforcement (US). The CS++ solution was added with 16% sucrose and paired with an intraduodenal (ID) infusion of water, the CS+ solution was paired with an ID infusion of 16% sucrose and the CS- solution was paired with an ID infusion of water. One and two weeks after conditioning, the water-deprived pigs were subjected to two-choice preference tests with the unreinforced CS solutions. Solutions intake, behavioural activity and some drinking parameters were measured. Despite no difference in CS intake during conditioning, the animals spent less time inactive and more time standing during CS++ than CS+ conditioning. When receiving CS++, the pigs explored the drinking trough more than when receiving CS-. Compared to the CS- condition, the numbers of drinking episodes and intra-drinking episode (IDE) pauses were also 36% and 49% lesser in the CS++ condition, but these differences were not significant. During the two-choice tests, the pigs did not show significant preferences. Nevertheless, during the first session, the pigs seemed to show a slight preference for the CS++ (57% of total intake) compared to CS+. The duration of CS++ drinking episodes represented 64% of the total duration compared to CS+ and CS- . The total time spent drinking the CS++ also represented 57% of the total time in the CS++ vs. CS- test. To conclude, although no clear-cut preferences were found during two-choice tests, the oral perception of 16% sucrose during conditioning induced changes in behavioural activities, motivational responses and microstructure of CS intake, suggesting the importance of oral food perception for food selection processes in pigs. Further studies are needed to investigate the impact of water deprivation on the expression of flavour preferences in pigs.