The effects of dietary level of tryptophan (TRP) and CP content and composition on voluntary feed intake, growth performance, and carcass characteristics in finishing pigs were studied in two experiments, with an equal number of females and castrated males. In Exp. 1, involving 120 Large White pigs from 44 to 99 kg BW with ad libitum access to feed, six treatments were compared according to a 2 x 3 factorial arrangement: 1) two levels of TRP (.09 and .13%), suboptimal and optimal for growth, respectively, 2) three types of CP supply (a 12.5% CP diet based on corn-soybean meal, and adequately balanced for essential amino acids [EAA] other than TRP; 15.7% CP diet with additional protein from corn gluten meal; 16.2% CP diet with additional nonessential amino acids [NEAA, in the form of L-glutamic acid.HCl and glycine], and the same levels of EAA as in the 12.5% CP diet. In Exp. 2, including four of the six previous factorial combinations (.09 and .13% TRP, 12.3 and 15.8% CP with additional protein), 32 pigs of 50-kg initial BW were used during 21 d, and further observations on meat quality characteristics, plasma free amino acid levels, and serotonin concentrations in the posterior hypothalamus were made. The major observed effects were interactions of different magnitude according to sex between TRP level and the amount and the composition of additional CP. At the suboptimal level of .09% TRP, the increase in protein content severely decreased daily feed intake and growth compared with the .13% level, especially in females. Conversely, the addition of NEAA at both TRP levels had little effect on daily feed intake and growth. Deficiency of TRP exerted a significant increase of pH in adductor femoris and semimembranosus muscles measured 45 min and 24 h postmortem, but only in females. Voluntary feed intake, as affected by dietary TRP and CP levels, was linearly related with concomitant changes in TRP to large neutral amino acids (TRP:LNAA) ratio both in feed and in plasma, which in turn was directly associated to hypothalamic serotonin concentration. It was concluded that an overly low concentration of serotonin in the hypothalamus, especially in females, as a result of TRP:LNAA imbalance, could be involved in the reduction of voluntary feed intake.

Tryptophan (TRP) content in the protein of the weaning diet was varied from deficient (.70 g/16 g N) to adequate (1.15 g/16 g N) and excess (1.60 g/16 g N) in diets fed to 108 pigs from d 5 to d 26 after weaning (W) and in 72 pigs from d 26 after weaning to slaughter (100 kg live weight) to assess immediate and long-term effects of TRP on performance. Daily weight gain and feed efficiency were improved when dietary TRP was increased from deficient to adequate (+60 and +40%, respectively). Concurrently, daily feed intake was elevated moderately (+15%). No further improvement was observed with excess TRP. In the low TRP group, gain/feed was significantly poorer up to 25 kg live weight, but this effect did not continue later. Although no compensatory growth could be shown in the group fed the deficient diet, growth retardation was very small (1.5%; P greater than .10) at slaughter. Early changes in TRP supply did not affect either carcass or meat quality. Behavioral reactivity, as determined on day W + 5 in an "open-field" test, did not affect early performance, but growth rate during the growing-finishing stage (3.2%) or the whole period (2.5%) was greater by nonemotional than by emotional pigs. Plasma amino acid contents in blood samples, withdrawn on day W + 15 (fed state) and W + 17 (fasted state), were consistent with the effect of TRP on growth rates. However, in the fasted state, a diet x reactivity interaction suggested that TRP removal from the plasma was less rapid in nonemotional than in emotional pigs. Furthermore, increased plasma concentrations of essential amino acids and urea in the latter group suggested that protein and amino acid catabolism was more rapid in emotional than in nonemotional pigs. These data are discussed relative to the effect of the behavioral type of pig on its TRP requirement.

The effects of dietary level of lysine and of level and source of CP on voluntary feed intake, growth performance, plasma free amino acids, and carcass characteristics were investigated in a study involving 60 female and 60 castrated male Large White finishing pigs (from 42 to 101 kg live weight) with ad libitum access to feed. Six treatments were compared according to a 2 x 3 factorial plan, with two levels of lysine (.55 and .65% selected below the recommended levels for both sexes) and three types of CP (N x 6.25) supply: a 13% CP diet based on wheat, peanut meal and soybean meal; a 15.6% CP diet providing the same amino acid pattern as that of the basal diet; and a 15.2% CP diet containing the same levels of essential amino acids as the 13% CP diet, with the addition of glutamic acid as a source of nonessential amino acids. By maintaining a constant amino acid pattern separate changes in dietary lysine and CP levels resulted in a relative independency of their effects on feed intake, growth performance, and body composition. Muscle gain increased with supplementary lysine, with a lower response at the lower CP level (13%). At the same level of lysine (.55 or .65%), increasing protein content from 13 to 15.6% did not affect feed intake, but growth rate was lower and feed/gain was increased, partly because of an additional energy cost resulting from catabolism of excess protein.(ABSTRACT TRUNCATED AT 250 WORDS)

The behavioral reactivity in an "open-field" test and plasma cortisol levels were studied in 72 pigs from 12 litters fed for 3 wk one of three diets with different levels of tryptophan: deficient (.14%), adequate (.23%), or excess (.32%). "Open-field" tests were performed three times: 5 d (day W + 5), 23 d (day W + 23) and 45 d (day W + 45) after weaning. The exploration time and the number of grunts provided an adequate measure of the individual emotional reactivity at day W + 5. Significant correlations were obtained between exploration time and the number of grunts at each time (r = -.83 at day W + 5; r = -.46 at day W + 23; r = -.71 at day W + 45). The distinction between animals remained (P less than .05) in terms of exploration time at both 23 and 45 d after weaning. At day W + 23, exploration time was lower in the group fed the adequate diet than in the two other groups. This effect was maintained subsequently after feeding all pigs the same adequate diet (day W + 45). In 36 pigs slaughtered at day W + 23, brain TRP concentration was higher with the excess dietary TRP than with deficient or adequate levels. Conversely, other plasma amino acids (particularly threonine) accumulated only in the brains of pigs fed the deficient diet. Plasma cortisol level assayed at weaning (W) and 2 wk later increased with age and was higher in 16-h fasted (day W + 15) than in 3-h fasted (day W + 17) pigs. Correlations were observed within litters in the fasting state, between the cortisol level and behavioral traits measured at day W + 23 (r = .70 for number of grunts, r = -.60 for exploration time). Dietary TRP did not affect the plasma cortisol level irrespective of the nutritional state after weaning. However, an interaction was noted between plasma cortisol and TRP status (P less than .05). Although dietary TRP induced large variations in brain amino acids and 5-hydroxyindole concentrations, changes in behavioral and cortisol responses were relatively minor.

Rat intestinal cells prepared from testes were incubated in the presence of different lutropin derivatives obtained by chemical modification of the amino groups. The cAMP accumulation and the testosterone biosynthesis were determined in the cell homogenates. Binding determinations were carried out by a radioligand receptor assay using tritiated methylated lutropin. The binding activities \ p=m-\ relative to native LH \ p=m-\ of three different derivatives obtained by reductive alkylation (methylated, ethylated and isopropylated LH) were in good agreement with the relative potencies assessed by their capacity to stimulate cAMP and testosterone production. Guanidinated LH (11 \p=m-\ NH2 groups modified) exhibited a binding activity and a relative potency relatively high with regard to cAMP accumulation (as compared with that of native LH). Its steroidogenic potency, however, was very low. When Leydig cells were incubated in the presence of native and guanidinated LH, the testosterone production was similar to that induced by the derivative alone, indicating that the derivative exerted a competitive inhibitory action preventing the stimulation of steroidogenesis by native LH. These results suggest that a guanidinated derivative is able to bind to the LH receptor and the complex so formed is able to be coupled with an adenylate cyclase pool (or cAMP compartment) which is not connected with the steroidogenic pathway.Chemical modification of the amino groups of lysine residues can be achieved in lutropin (luteiniz¬ ing hormone, LH) without loss or with only a partial loss of the biological activity, if the positive charge of these residues is not abolished (De la Llosa et al. 1974a; Liu et al. 1974). These derivatives have been tested by various bioassays, in vivo and in vitro. It has been shown that they are able to bind to the LH-receptors (Liu et al. 1974; De la Llosa-Hermier et al. 1977), to activate ovarian adenylate cyclase (Tertrin-Clary & De la Llosa 1978) and to stimulate steroidogenesis in the ovary. We considered it of interest to investigate the correlation between the succes¬ sive responses induced by these derivatives which are known to be consecutive steps in the mecha¬ nism of action of LH. Rat Leydig cells were used as biological material. As is well known, binding of lutropin to the receptors of Leydig cells is followed by activation of adenylate cyclase, and the subse¬ quent cyclic AMP accumulation is accompanied by stimulation of testosterone production. The data reported here show that a good correlation is observed for most of these derivatives in each of the three steps, but that at least in one case (guanidinatedLH), binding to the receptors and stimula¬ tion of adenylate cyclase do not result in a propor¬ tional increase in testosterone biosynthesis. In such a case an inhibitory effect of the derivative on the final action of the hormone could be expected and was demonstrated. Material and MethodsOvine LH was prepared in a highly purified state (biolo¬ gical potency: 2 x LH-NIHS11) in our labo...