The tryptophan requirement of piglets as influenced by the threonine level

Abstract

Summary The tryptophan (Trp) requirement was investigated in post weaning piglets from 5 to 10 weeks of age (7–20kg). Three feeding trials were conducted. All piglets were randomly alloted according to age, sex, weight, pre‐weaning growth and ancestry to the different dietary treatments. Ad libitum feed intake (per 6–7 pigs) and daily gain (individual) were recorded at 5 and 10 weeks (end of experiment). In the first trial 72 Belgian Landrace (BL) and 60 Piétrain × Seghers Hybrid (P × SH) piglets were used for two dietary treatments. The basal diet, 16% crude protein (CP), 1.06% lysine (Lys) and 0.14% Trp, was supplemented up to 0.19% Trp. This trial revealed a significant improvement in daily gain from 0.14% (0.10% ileal digestible Trp) to 0.19% Trp (0.15% ileal digestible Trp). The second trial was based on a lower CP content (14%) and a similar Lys level. Trp was increased in steps from 0.16% to 0.18, 0.21 and 0.24%. One hundred and fifty‐eight BL and 147 P × SH piglets were divided over the four feeding regimes. No improvement in growth was obtained for the levels above 0.16% Trp (0.11% ileal digestible Trp). It was presumed that Thr was the limiting factor. A third trial was conducted, which consisted in a 3 × 3 factorial experiment, using the same CP level as in trial 2, but a lower Lys level (1.03%) and combined three Trp levels (0.18, 0.21 and 0.23%) with three Thr levels (0.65, 0.72 and 0.79%). Nine groups of 49 animals (all P × SH) were used in this experiment. Only a slightly favourable tendency of Trp towards increasing daily feed intake was found and the growth and feed: gain ratio were not affected at all. The Thr, on the contrary, led to increasing growth figures. The optimum Thr level seemed to have been reached by the 0.72% total Thr or 0.57% ileal digestible Thr level, yielding a ratio of 65% of Thr:Lys. For Trp, the requirement was difficult to predict in the conditions of the experiment, as no optimum appeared for Trp from the animal performance results. Zusammenfassung Der Tryptophanbedarf von Ferkeln in Abhängigkeit vom Threoningehalt in der Ration Alle Ferkel wurden nach Alter, Geschlecht, Gewicht, Zunahme vor dem Absetzen und Abstammung den verschiedenen Diäten zugeordnet. Die ad libitum Futteraufnahme (für jeweils 6–7 Schweine) sowie die täglichen Zunahmen (einzeln) wurden mit 5 und 10 Wochen (letztmalig) aufgenommen. Im ersten Versuch wurden 72 Ferkel der Belgischen Landrasse (BL) und 60 Piétrain × Seghers Hybriden (p × SH) für 2 Fütterungsversuche eingesetzt. Die Basisdiät bestand aus 16% Rohprotein, 1,06% Lysin (Lys) und 0,14% Tryptophan (Trp) und wurde auf 0,19% Trp ergänzt. Dieser Versuch ergab einen signifikanten Anstieg der täglichen Zunahmen von 0,14% (0,10% dünndarmverdauliches Trp) bis 0,19% Trp (0,15% dünndarmverdauliches Trp). Im zweiten Versuch wurde ein niedriger Rohprotein‐ und ein vergleichbarer Lys‐Gehalt eingesetzt. Der Tryptophangehalt wurde von 0,16% über 0,18% und 0,21% auf 0,24% gesteigert. 158 BL und 147 p × SH Ferkel wurden auf diese 4 Diäten aufgeteilt. Keine Wach...

Threonine and tryptophan ratios fed to nursery pigs*

“…(1998) showed no performance response to additional Trp above 1.3 g digestible Trp/kg diet and improved gain and feed intake by increasing the Thr:Lys ratio to 0.65, but no effect of supplementing Trp when dietary Thr appeared to be limiting. The discrepancy in results between Warnants et al. (1998) and the current experiment cannot be explained, especially when these two experiments utilized a similar diet composition and used pigs of a similar weight range.…”

“…This is supported by others (Jansman et al., 2000; Lynch et al., 2000) who reported that wheat‐barley‐based diets may need to have a 0.21 Trp:Lys ratio for optimal performance. In contrast, Warnants et al. (1998) showed no performance response to additional Trp above 1.3 g digestible Trp/kg diet and improved gain and feed intake by increasing the Thr:Lys ratio to 0.65, but no effect of supplementing Trp when dietary Thr appeared to be limiting.…”

Studies on the tryptophan requirement of piglets

“…The optimal ratio of tryptophan to lysine in this experiment was about 17:100; it should be pointed out, however, that the dietary lysine concentration, being 12.3 g per kg diet, was about 10% and 30% higher than the levels recommended by the National Research Council (1995) for the body weight categories from 10 to 20 kg (11.5 g lysine recommended per kg diet) and over 20 kg (9.5 g lysine recommended per kg diet), respectively. Although, the optimal ratio of tryptophan to lysine, thus, might be underestimated, it is higher than optimal ratios reported in the literature ranging between 0.14 and 0.15 (Borg et al, 1987;Burgoon et al, 1992;Warnants et al, 1998).…”

“…In the body weight range between 5 to 35 kg, the stated tryptophan requirements for maximum performance vary widely. In most studies tryptophan concentrations between 1.2 und 1.6 g per kg feed were sufficient for maximum performance (Zimmerman, 1975;Leibholz, 1981;Sato et al, 1987;Batterham and Watson, 1985;Wahlstrom et al, 1985;La Rue et al, 1985;Borg et al, 1985a;Borg et al, 1987;Han et al, 1993;Henry et al, 1986;Warnants et al 1998). An older study (Boomgaardt und Baker, 1973) calculated an even lower tryptophan requirement of less than lg per kg feed.…”

Optimum tryptophan: Lysine ratio in diets for growing pigs: Analysis of literature data

“…However, when following this procedure, the optimum ratio (T: L opt ) tends to be overestimated because the true optimum ratio lies between T: L opt and the nearest ratio tested below (T: L opt À 1 ). It is, (Lougnon, 1981; probably in one of the experiments of Batterham and Watson, 1985), threonine (Lougnon, 1984;Warnants et al, 1998;Eder et al, 2001) or crude protein (Mö hn and Susenbeth, 1994) in the diets were limiting. b Initial and final body weight of animals, at which the beginning of the plateau phase was observed.…”