Abstract
The objective of this study was to evaluate the effects of increasing dietary digestible tryptophan levels on performance and carcass traits of growing pigs. Fifty crossbred castrated male pigs, with average initial and final body weight of 29.0 ± 1.20 kg and 60.4 ± 1.95 kg were allotted in a completely randomized block design, with five treatments (0.125, 0.133, 0.141, 0.149, and 0.157% of digestible tryptophan, corresponding to digestible tryptophan:lysine relations of 15.0, 16.0, 17.0, 18.0, and 19.0%, respectively) and five replicates, with two pigs per experimental unit, which was represented by the pen. Experimental diets and water were supplied ad libitum throughout the experimental period. Averages of minimum and maximum temperatures inside the facility were of 24.3 ± 0.87 ºC and 28.0 ± 1.82 ºC, respectively. Feed intake and body weight gain increased linearly with increasing dietary tryptophan levels. However, there was no effect of digestible tryptophan on feed conversion or protein deposition of pigs. The highest tryptophan level evaluated (0,157%), corresponding to a digestible tryptophan:lysine relation of 19.0%, provided the greatest weight gain of 30 to 60 kg castrated male pigs.
Highlights
The constant genetic selection for increased protein deposition needs constant reassessment of pigs’ nutritional requirements, since changes in rates in body tissues deposition affect the daily need of nutrients, amino acids.Tryptophan is an essential amino acid in the piglets and growing-finishing pigs’ nutrition (NRC, 1998) and in diets with corn as the main ingredient tryptophan is the fourth limiting amino acid
To ensure that no other essential amino acid other than tryptophan was deficient in diets, the ratios of these amino acids with lysine were above those recommended in the ideal protein for animals at the same stage of growth, according to Rostagno et al (2000)
There was effect (P
Summary
The constant genetic selection for increased protein deposition needs constant reassessment of pigs’ nutritional requirements, since changes in rates in body tissues deposition affect the daily need of nutrients, amino acids. Tryptophan is an essential amino acid in the piglets and growing-finishing pigs’ nutrition (NRC, 1998) and in diets with corn as the main ingredient tryptophan is the fourth limiting amino acid. Tryptophan is the fourth limiting amino acid after lysine, methionine and threonine. When the level of tryptophan in the diet is limiting compared with other essential amino acids, protein synthesis, body weight gain and feed efficiency are adversely affected (Le Floc’h & Seve, 2007; Jansman, 2010). In the brain and intestine, tryptophan is required as substrate for the synthesis of serotonin, a neurotransmitter that stimulates feed intake (Henry et al, 1992)
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