Figure 2 - Effect of lowering dietary crude protein level and heat stress on feed intake and performance of growing pigs (21 days; experiment 1).


0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25


* P = 0.008 P = 0.10 1.683 1.525 1.462 *


P = 0.01 P = 0.004


* 0.938 0.777 0.770 0.557 0.513 0.559 P = 0.06 P = 0.05 * + 5 point


Treatment 1 = High CP diet under thermo neutral Treatment 2 = High CP diet under heat stress Treatment 3 = Low CP diet under heat stress


Nutritional strat- egies of adding amino acids can mitigate the negative effects of heat stress in pigs.


amino acids on performance and serum urea nitrogen of pigs under heat stress with ambient temperatures in the range 25–43°C. Growing pigs of roughly 34 kg were assigned to three diets for 21 days. • Diet 1 was the control diet based on wheat, soybean meal and three supplemental amino acids and adequate in amino acids (15.1% CP; 0.98% SID lysine). • Diet 2 was the same as the control diet plus 25% extra es- sential amino acids (19.0% CP; 1.23% SID lysine) supplied by adding more soybean meal as intact protein. • Diet 3 was the same as the control diet plus 25% more of nine essential amino acids (16.1% CP; 1.22% SID lysine) by adding nine supplemental amino acids. As shown in Figure 3, feed intake was not different among the treatments. Compared with the control diet, supplying extra essential amino acids using crystalline amino acids in- creased ADG by 18% and G:F by 13 points. There was only a trend for improved G:F by increasing soybean meal. It’s interesting to take a look at the concentration of serum urea nitrogen in pigs under heat stress. Compared with the control diet or diet 3, serum urea nitrogen at day 20 was higher in pigs fed diet 2, indicating that 25% extra supply of amino acids by adding more soybean meal resulted in in- creased excess amino acids associated with reduced amino acid utilisation. Lower serum urea nitrogen, on the other hand, indicates improved amino acid utilisation associated with a reduced need for deamination of excess amino acids.


Crystalline amino acids Based on these results, lowering dietary CP content from 22% to 14% and balancing with supplemental amino acids im- proves G:F efficiency of growing pigs under heat stress condi- tions. Supplying an increased amount of essential amino acids (25% above requirement) to a low CP diet using crystalline amino acids rather than intact protein improves the impaired performance of pigs under heat stress conditions.


References available on request.


Figure 3 - Effect of dietary level and form of amino acids supply on feed intake and performance of growing pigs under heat stress (21 days; experiment 2).


0.20 0.45 0.70 0.95 1.20 1.45 1.70 1.95 2.20


P > 0.05 1.639 1.669 1.656


Diet 1 = Control (AA adequate diet) Diet 2 = Diet 1 + 25% AA (soybean meal) Diet 3 = Diet 1 + 25% AA (9 free AA)


P = 0.05 + 18%


* 0.644 0.714 0.761


* + 13 point


P = 0.09 P = 0.02


0.343 ADFI, kg ADG, kg ▶ PIG PROGRESS | Volume 37, No. 5/6, 2021 G:F 13


+ 9 point 0.437 0.477


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