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-_ _ _~_ _ _ 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.

I . A slope-ratio assay was developed with growing pigs to determine the availability of lysine in five protein concentrates. The basal diet contained 5.2 g lysine/kg and six levels of lysine, in 500 mg/kg increments, were used to determine the pig's response to standard lysine. The protein concentrates were incorporated into the basal diet to provide five levels of total lysine, again in 500 mg/kg increments, at the expense of wheat starch. A daily feeding scale based on live weight was used to ensure similar nutrient intakes. Pigs were fed at three-hourly intervals to ensure the utilization of free amino acids in the diets. Four pigs were allotted to each dose level and response was assessed over the 20-45 kg growth phase.2. Potency estimates for available lysine in the five protein concentrates varied, depending on whether live-weight gain or carcass gain was used as the criterion of response. Carcass gain was considered more appropriate as it was not influenced by variation in gut fill. Availability of lysine in the five proteins, using carcass gain/d were (proportion of total) cottonseed meal 0'39, fish meal 0.89, meat-and-bone meal 0.50, skim-milk powder 0.88 and soya-bean meal 0.87.3. Rat slope-ratio assay results for available lysine in the five protein concentrates were in general agreement with those from the pigs. In contrast, thedifferences in available lysinewere not detected by thechemical Previous work (Batterham et al. 1978) showed that for growing pigs, the content of available lysine in locally produced cottonseed meal, two meat meals and sunflower meal was approximately 60% less than that in rapeseed meal, skim-milk powder and soya-bean meal. Similar differences were detected with a slope-ratio assay with rats but not with the chemical Silcock available-lysine assay as developed by Roach et al. (1967). In view of these differences, it seemed appropriate to attempt to quantify the available lysine content of the major protein concentrates for pigs and to evaluate the efficiency of some of the different techniques for estimating available lysine. This paper reports the results of a slope-ratio assay that was developed with growing pigs to determine the availability of lysine in five protein concentrates. Lysine availability in these proteins was also estimated by a slope-ratio assay with rats, the Silcock available-lysine technique and by ihe direct fluorodinitrobenzene (FDNB)-available-lysine assay (Carpenter, 1960).Pig slope-ratio assay Diets. For the pig assay, five protein concentrates were assayed in the one experiment. This involved the use of thirty-two diets; the basal diet (blanks), six diets to determine the pig's response to standard lysine and twenty-five for the five protein concentrates (five/ protein concentrate). The basal diet contained (g/kg) : wheat 730, wheat gluten 50, L-lysine monohydrochloride (anhydrous) I .03, DL-methionine 0.30, L-threonine 0.70, mineral and vitamin premix 5, bone flour 30, and starch 182.97 (Table I). The wheat was a high-protein

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.