Heat stress (HS) depresses pig performance mainly because of appetite reduction, although other factors involved in the cellular availability of nutrients may also contribute to that depression. An experiment was conducted with twelve pair-fed pigs (30.3 ± 2.7 kg BW) to examine the effect of severe HS (up to 45 °C) on the expression of genes coding for two cationic amino acid (AA) transporters (b(0,+) AT and CAT-1), leptin, heat-shock protein (Hsp-90) and myosin in several tissues; serum concentrations (SC) of AA; and performance. There were two treatments: Comfort, pigs housed at an average temperature of 22 (±2) °C; and HS, pigs housed in a similar room with no climate control, where temperature was raised up to 45 °C. All pigs received the same wheat-soybean meal diet and had similar daily feed intake. Comfort pigs had a higher daily gain and better gain/feed ratio than HS pigs (p < 0.05). The expression of b(0,+) AT in jejunum and liver, that of myosin in the Semitendinosus muscle, and leptin in adipose tissue was lower, but CAT-1 in jejunum and liver, and Hsp-90 in liver was higher in HS pigs. The SC of Lys and Met in HS pigs were around 55% and 20%, respectively, of that in Comfort pigs (p < 0.05). In conclusion, HS affects the expression of cationic AA transporters, myosin, Hsp-90, leptin; the SC of Lys and Met; and the performance of pair-fed pigs. These results suggest that HS-related changes in gene expression affect the performance of pigs beyond the effect caused by the reduction in voluntary feed intake.
The effect of breed and dietary avocado level on the total apparent digestibility (RAD) and balance of nitrogen (N) energy, in young pigs, was studied. Four Pelón Mexicano (PM) and four Yorkshire × Landrace (Y×L) barrow male pigs (39.2 kg average inital liveweight) distributed in two groups according to a change over design in a 2×2 factorial arrangement (breed and diet) were used. The pigs received on a pair feeding basis (0.10 kg DM/kg W 0.75 per day), the experimental diets. The diets were formulated to contain 30 or 150 g crude fat by partial replacement of the maize/soyabean meal diet by avocado (Persea americana Mill.) fresh pulp. The RAD of crude fat was 73.8 and 71.5% and that of N was 83.4 and 82.8 % in PM and Y×L pigs, respectively. There was no significant effect (P>0.10) of crude fat level on RAD of N and energy. N and energy balance significantly (P<0.05) favoured Y×L as compared with PM pigs. In conclusion, the poor N retention of PM pigs could be related to body composition of this local, non improved genotype. The use of avocado for feeding pigs, PM included, should determine a high digestibility of the crude fat fraction and at the same time a considerable deterioration of N retention, probably due to an unbalanced composition of amino acids. The level of avocado pulp inclusion in the diet of the pig should be involved in these circumstances.
ABSTRACT. Free amino acids (AA) appear to be absorbed faster than protein-bound AA (PB-AA). We conducted an experiment to assess the effect of feeding pigs with a partially free (F-AA) or totally PB-AA diet on expression of selected genes and performance of pigs. The expression of cationic AA transporters b 0,+ and CAT-1 in intestinal mucosa, liver, and longissimus (LM) and semitendinosus (SM) muscles, as well as that of myosin in LM and SM, was analyzed. Twelve pigs (31.7 ± 2.7 kg) were used. The F-AA diet was based on wheat, supplemented with 0.59% L-Lys, 0.33% L-Thr, and 0.10% DL-Met. The PB-AA diet was formulated with wheat-soybean meal. Average daily feed intake was 1.53 kg per pig. The expression of b 0,+ and CAT-1 was analyzed in jejunal and ileal mucosa, liver, LM, and SM; myosin expression was also analyzed in both muscles. Pigs fed the PB-AA diet tended to have Effect of amino acid form on mRNA expression and performance in pigs higher weight gain and feed efficiency (P < 0.10), and had thinner back fat (P = 0.02). The expression of b 0,+ was higher (P < 0.01) in jejunum but lower (P < 0.01) in the liver of pigs fed the F-AA diet; CAT-1 tended to be lower in liver but higher in LM of PB-AA pigs. Myosin expression was not affected. Intestinal AA absorption was faster in pigs fed the F-AA diet, but AA uptake by the liver seemed to be faster in pigs fed the PB-AA. Performance and expression of AA transporters and myosin suggest that the dietary content of free or protein-bound AA does not affect their availability for protein synthesis in pigs.
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