A total of 672 male and female piglets (21 d postweaning; approximately 13 kg BW) were selected to be used in 3 different experiments to assess the influence of dietary electrolyte balance (dEB; Na + K - Cl, in mEq/kg of diet) on feed preference and growth performance. In Exp. 1, piglets were fed 4 isoenergetic diets differing in dEB level: 16, 133, 152, and 269 mEq/kg diets. Changes on dEB were obtained by changing the levels of sodium and chloride with calcium chloride, calcium carbonate, and sodium bicarbonate. Piglets fed the 16 and 133 mEq/kg diets achieved a greater ADG (P < 0.04), BW (P < 0.04), and apparent total-tract digestibility of CP and Zn (P < 0.05) than did piglets fed the 269 mEq/kg diet. The 16 mEq/kg level also reduced blood total CO (P < 0.01), bicarbonate (P < 0.01), and base excess (P < 0.02) concentrations compared with the rest of the dietary treatments. Three diets differing in dEB were designed for Exp. 2 and 3: -16, 151, and 388 mEq/kg diets. In Exp. 2, greater ADFI (P = 0.03), BW (P = 0.02), ADG (P < 0.001), and G:F (P < 0.01) were observed for piglets fed the -16 mEq/kg diet than those fed the 388 mEq/kg diet. Subsequently, their short-term preference for these diets was assessed by using a 2-d choice-test protocol (30 min). Piglets preferred (P < 0.001) the 388 mEq/kg diet to the -16 mEq/kg diet, independently of the dietary treatment they received before. Pigs also preferred (P < 0.001) the 151 mEq/kg diet when compared with the -16 mEq/kg diet. Experiment 3 assessed the long-term preference and short-term consumption of the -16 and 388 mEq/kg diets. Similar to Exp. 2, animals showed a greater (P < 0.001) intake of the 388 mEq/kg diet than they did of the -16 mEq/kg diet during both the preference (14 d) and 1-feeder (2 h) tests conducted. Results show that low rather than high dEB levels optimize growth performance of piglets. When they have the opportunity to choose, piglets are unable to select the diet that optimizes their performance, either in short- or in long-term preference tests, showing also a greater short-term consumption of high instead of low dEB levels.

A ten-year food preference database (2007–2017) was used to relate food selection in dogs to the nutritional components of diets by doing a principal component analysis (PCA) and a linear regression between components obtained and dogs’ preferences. Intake and preference of preferred diets were analyzed by dogs’ sex, breed, age, body weight, and the season of the year (hot or cold). The fourth component after PCA presented a relation with food preferences (OR = −2.699, p = 0.026), showing negative correlations with crude fiber (rho = −0.196; P = 0.038) and dry matter (rho = −0.184; p = 0.049). Weight (OR = −1.35; p < 0.001), breed, both Boxer (OR = 10.62; p = 0.003) and Labrador Retriever (OR = 26.30; p < 0.001), and season (hot season) (OR = −5.27; p < 0.001) all influenced animals’ intake. Boxers presented a lower food preference compared to the other breeds (OR = −44.3; p < 0.001), while animals’ weight influenced preferences only in Boxers (OR = 2.02; p < 0.001). Finally, age and sex did not affect dogs’ preference or intake of preferred diets. Thus dry matter and fiber content have a negative impact on dogs’ food choices. Dogs’ weight, breed, and season affected food intake, but only breed affected dogs’ preferences, which is probably explained by adaptive changes in the detection, metabolization, and learning of nutritive food cues.

A total of 552 entire male and female nursery pigs were selected to be used in 2 different experiments that aimed to study if milk ingredients can be replaced by highly preferred protein sources (Exp. 1) and if pre- and postnatal exposure of those protein ingredients through the maternal diet may increase pig performance (Exp. 2). In Exp. 1, 240 pigs were separated after weaning (28 d) into 2 groups depending on the presence of lactose in their diets. Pigs ( =120) fed diets with the precence of lactose (lactose +) were given prestarter (0-14 d) and starter (15-33 d) diets with 142 and 50 g/kg of sweet milk whey, respectively; the lactose-free group ( = 120) was offered an isoenergetic diet with 20 g/kg of porcine-digestible peptides (PDP; Palbio 62SP; Bioibérica S.A., Palafolls, Spain) and wheat replacing sweet milk whey. Choice and 1-feeder tests were performed in another group of animals ( = 72) to evaluate the preference and acceptance for both diets. Pigs preferred ( = 0.039) the lactose+ over the lactose-free diet after a 30-min choice test and consumed more ( = 0.001) lactose+ than lactose-free diet in a 1-feeder test. However, no difference ( > 0.467) in performance was observed between groups for the entire nursery period. In Exp. 2, 120 animals were obtained from sows that, during late gestation (14 d) and lactation (28 d), were fed diets containing 20 g/kg of PDP and another 120 animals were obtained from sows fed an isoenergetic diet without PDP inclusion. Placenta samples were collected at farrowing to assess the volatile compounds present in the placental fluid of sows. After weaning, all pigs received a feed containing 20 g/kg of PDP in the prestarter and starter diets. A principal components analysis of the total volatile compounds showed the exclusive presence of sulfur-containing compounds and a higher presence of terpene compounds in the placental fluid of PDP-supplemented sows. In addition, pigs coming from sows fed diets supplemented with PDP tended to show a higher ADFI ( = 0.07) and ADG ( = 0.06) than did pigs coming from control sows during the 15 to 33 d after-weaning period. These results suggest that dietary incorporation of sweet milk whey may be replaced by a specific protein source without affecting performance of pigs after weaning. However, more experiments are needed to elucidate the mechanism for the sow's diets' influence over pig's performance.

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A ten-year database of food preference tests (n = 1021; period 2007−2017) was used to explore the feeding behavior of domestic cats. Principal component (PC) analysis and linear regression between food nutrients and preferences (for the most preferred diet of each test; Diet A) were performed. Intake and preference for Diet A were analyzed by intrinsic cats’ variables and climate season. The PC1 (calcium (Ca), phosphorus (P), and ash), PC2 (lipids and ether extract) and PC4 (crude fiber; CF) had borderline significance (p < 0.06; β = −1.42, β = −1.56, and β = 2.68, respectively). Ash and CF contents presented negative correlations with food preference (rho = −0.269, p = 0.031; rho = −0.338, p = 0.006, respectively), and Ca had borderline significance and negative correlation with food preference (rho = −0.241, p = 0.054). Body weight and sex influenced the intake of Diet A, being lower for females (β = 11.758; p = 0.014) and heaviest cats (β = −5.490; p < 0.001). However, only body weight affected food preferences, where the heaviest cats had greater preferences for Diet A. Hot season decreased food intake (β = −2,117; p = 0.032), mostly in females (rho = −3.537; p = 0.002). Males had greater preferences for Diet A during hot seasons (β = 10.216; p = 0.023) and females presented similar preferences throughout the year (p = 0.950). Mineral contents, body weight and sex affected food intake and preferences of cats under the influence of climate season, probably explained by adaptive changes in food detection.