-_ _ _~_ _ _ Diets were formulated using sugar, soya-bean meal and free amino acids to contain 0 , 1 4 8 g lysine/MJ digestible energy (DE) and offered at three times maintenance to male and female pigs from 20 to 45 kg live weight. Growth responses and retentions of protein, fat, energy and lysine were assessed.Increasing the dietary lysine concentration resulted in significant (P < 0401) linear and curvilinear increases in growth rates and decreases in food conversion ratios. There was only a small effect of lysine concentration on total energy retention, but a substantial effect on the partitioning of energy deposition, with increases in the rate of protein deposition and decreases in fat retention. There was no difference in the efficiency of protein deposition between male and female pigs but males responded more to higher lysine concentrations than females (estimated 0.93 and 0.74 g lysine/MJ DE for males and females respectively). Lysine concentration in the protein deposited by the pigs increased linearly and curvilinearly (P < 0.01) from 5.8 to 6.6 g lysine/l6 g N with increasing dietary lysine concentration.There was a linear and quadratic response (P < 0.001) in retention of ileal digestible lysine, with the minimum retention of 0.16 occurring at 0.1 g lysine/MJ DE and increasing to a maximum retention of 073 a t a dietary concentration of 0.47 g lysine/MJ DE. The efficiency of lysine retained/ileal digestible lysine intake was 0.86 and the endogenous lysine loss was estimated a t 0.94 g/d.

The availability of lysine and the ileal digestibility of amino acids in three cottonseed meals and a soyabean meal for growerlfinisher pigs were determined. The usefulness of the availability estimates for formulating diets was assessed. The availability of lysine, as assessed with a slope-ratio assay, was (proportion of total): cottonseed meal no. 1, 0.27; no. 2, 0.30; no. 3, 0.29; soya-bean meal, 0.90. Ileal digestibility of lysine in the meals (proportion of total) was: cottonseed meal no. 1,0.58; no. 2,068; no. 3,0.72; soya-bean meal, 089. Pigs given diets formulated to the same available lysine concentration grew at similar rates and retained the same amount of lysine in the carcasses. The results indicate that, for meals of high availability (soya-bean meal), reduced ileal digestibility appears to be the main reason for reduced availability. However, in meals of low availability (cottonseed meal), reduced ileal digestibility only accounts for part of the reduced availability. Thus, the ileal digestibility of lysine is not a reliable indicator of lysine availability.Lysine: Ileal digestibility : Availability : Cottonseed meal: Soya-bean meal: Pigs Previous work (Batterham et al. 1979, 1984) indicated that the availability of lysine in cottonseed meal, as assessed by slope-ratio assays, was low for pigs (0.394.43). This was in contrast to soya-bean meal, where lysine availability was high (0.84-0.98). The low lysine availability in cottonseed meal is presumably due to the processing conditions used in the extraction of oil and inactivation of the toxin, gossypol. It is necessary to formulate diets on an available lysine basis to take into account the large difference in availability for growing pigs that occurs between the different protein concentrates.Slope-ratio assays are time-consuming and expensive to conduct and interest has centred on the use of the ileal digestibility assay to estimate amino acid availability. This assay also has the advantage over slope-ratio assays in that the digestibility of all amino acids can be assessed at the same time and only small numbers of pigs are required per assay. The assumption is made that, if an amino acid is not recovered at the terminal ileum, then it has been absorbed in a form suitable for utilization. This assumption is not strictly correct, as amino acids can be absorbed in forms that are not efficiently utilized (e.g. 6-N-propionyl-L-lysine in rats (Bjarnason & Carpenter, 1969)). Thus, ileal digestibility can overestimate availability.Despite the interest in these assays, there have been few studies of the relationship between ileal digestibility and lysine availability. In comparative studies with one sample of lupin (Lupinus aZbus)-seed meal, the ileal digestibility of lysine for finisher pigs (0.86;

Abstract:The threshold level of growing pigs to trypsin and chymotrypsin inhibitors was investigated by adding graded levels of meals rich in these inhibitors to diets and recording responses. Diets were formulated to contain either 250, 500 or 750 g kg-' of Opal chickpea, dehulled Tyson chickpea or dehulled pigeonpea meals and pig response compared to that of pigs given a wheat and soya-bean meal control. Trypsin inhibitor levels (mg g-l) of the diets were, respectively, control, 0.2; chickpea meal 1, 1.2-3.2; chickpea meal 2, 1.74.7; pigeonpea meal, 1.43.6. Chymotrypsin inhibitor levels (mg g-') of the diets were, respectively, control, 0.2; chickpea meal 1, 0.9-2.2; chickpea meal 2, 16-45; pigeonpea meal, 08-2.1. The diets were offered ad libitum over the 20-50 kg growth phase. Growth responses of the pigs fed the two chickpea meals were similar to those of the pigs fed the control soya-bean meal diet (P > 0.05). In contrast, the addition of pigeonpea meal linearly depressed growth rate (P < 0.001), feed intake (P < 0.05) and increased the feed conversion ratio (P < 0.05). inclusion levels of the chickpea meals had no effect on organ weights, whereas the inclusion of pigeonpea meal significantly affected the weights of the liver and pancreas (P < 0.05), indicating the presence of other anti-nutritional factors. The results indicate that the growing pig can tolerate dietary levels of at least 4.7 and 4.5 mg g-' of trypsin and chymotrypsin inhibitors, respectively. These threshold levels are unlikely to be exceeded in conventional diets containing the majority of grain legumes. The results also indicate that dehulled pigeonpea meal contains an anti-nutritional factor(s) for growing pigs.

I. The availability of lysine in nine vegetable-protein concentrates was assessed using the slope-ratio assay for growing pigs and rats. Diets were equalized for crude fibre using solka floc to minimize any possible effects of variation in fibre content on availability estimates.2. The availability of lysine in the nine proteins for pigs, using food conversion efficiency (FCE) on a carcass basis as the criterion of response were (proportion of total): cottonseed meal 0.39, lupin (Lupinus angustijolius) seed meal no. 1 0.37, no.

Two experiments were conducted to determine the utilization of ileal digestible lysine by pigs. In the first, the apparent ileal digestibility of amino acids in cottonseed meal, meat-and-bone meal and soya-bean meal was determined in pigs fitted with 'T'-shaped cannulas. In the second experiment, three lysinedeficient diets were formulated to 0.36 g ileal digestible lysine/MJ digestible energy (DE), with lysine contributed from the three protein concentrates as the only source of lysine in sugar-based diets. An additional three diets were formulated with supplements of lysine to verify that lysine was limiting in the first three diets. The growth performance and retention of lysine by pigs given the six diets over the 20-45 kg growth phase were then determined. The apparent ileal digestibility of lysine in the three protein concentrates (proportion of total) was : cottonseed meal 0.74, meat-and-bone meal 0.78, soyabean meal 0.89. Growth rates (g/d) of the pigs given the three diets formulated to 0.36 g ileal digestible lysine/MJ DE were significantly different (P < 0001): cottonseed meal 377, meat-and-bone meal 492, soya-bean meal 541. The response of pigs to the addition of lysine confirmed that lysine was limiting in these diets. Crude protein (nitrogen x 6.25) deposited by the pigs was significantly higher (P < 0.001) for those given soya-bean meal (77 g/d), relative to meat-and-bone meal (66 g/d) and cottonseed meal (38 g/d). The proportion of ileal digestible lysine retained by pigs given the three protein concentrates was: cottonseed meal 0.36, meat-and-bone meal 0.60, soya-bean meal 0.75. The results indicate that values for the ileal digestibility of lysine in protein concentrates are unsuitable in dietary formulations as the assay does not reflect the proportion of lysine that can be utilized by the pig. It appears that, with heat-processed meals, a considerable proportion of the lysine is absorbed in a form(s) that is (are) inefficiently utilized. Interest has centred on the use of the ileal digestibility assay to estimate amino acid availability. This assay has the advantage that the digestibility of all amino acids can be assessed at the same time and only small numbers of pigs are required per assay. The assumption is made that, if an amino acid is not recovered at the terminal ileum, then it has been absorbed in a form that can be utilized by the pig. With weaner pigs, Leibholz (1985) reported that the retention of apparently absorbed lysine at the terminal ileum was 0.860.94 for five diets containing different protein sources, and suggested that the apparent digestibility of lysine could be used to predict lysine availability.However, in a previous study (Batterham et al. 1990a), there was close agreement between ileal digestibility and lysine availability in soya-bean meal (0.89, 0.90 respectively) but not for cottonseed meal (0.58-0.72 ileal digestibility, 0.274-30 lysine availability). Formulating diets containing cottonseed or soya-bean meals on an available lysine basis