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BEAMES, R. M. AND NGwrP"{, T. N. 1978. Growth and digestibility studies with growing-finishing pigs receiving whole barley or ground barley by various feeding methods. Can. J' Anim. Two growth trials and one digestibility trial with growing-finishing pigs are reportid. In each growth trial, three groups of six barrows and three groups of six giits were placed Jn each of the four dietary treatments of barley plus 15% soybean meal fromapprox.23 kg body weight to approx' 84 kg body weight' The four treatments consisted of providing barley whole or ground, with the concentrates either mixed with the barley oriupplieO e h after the meal of barley. The feed allowance was slightly greater in the iecond trial than in the fint. In the digestibility trial there were two slou.""r of barley, each presented in three forms: whole, rehydrated acid-preserved whole, and giound, all mixed with the concentrates. Each diei was supplied at a restricted level oi ad libitum to barrows at28.9kg and 57'0 kg mean body-weight. In neither growth trial was there a significant effect of method of providing the giound bariey on performance. With whole barley, feed efficiency was iigniricaitly iiferior to thai obtiined with ground barley, betng 2o-37% lower when whole grain and concentrates were rnixed, but only 5-l6Vo lower when the whole grain and concentrates were provided separately. The digestibility trial indicated no differences between the twoiorms of whole grain, but a superior utilization of the ground grain. Dry matter digestibility of both iorms of whole grain was significantly lreater in the younger pigs iiran in the older pigs , increasing from 63 .0 to 7 | 'lVa for ihe whole grain, aid fio-OZ.: to 73.2Vo for the rehydrated acid-preserved whole grain. Dry matter digestibility of ground grain averaged 77

I . Thirty-six male rats of initial age 27 d were fed on diets based on barley grain for 3 weeks. Crude protein (nitrogen x 6.25) was fixed at 120.0 g/kg dry matter (DM) and cystine at 2.0 g/kg DM in all diets. The basal diet contained 3 3 g methionine plus cystine/kg DM with L-methionine added in increments of 0.5 g/kg DM up to a final level of 7.0 g methionine plus cystine/kg DM. A 'positive control' diet of barley plus 193.7 g soya-bean meal/kg DM contained 6.0 g methionine plus cystine/kg DM.2. Weight gain, food conversion efficiency (FCE), urinary urea-N excretion, carcass composition and activities of liver cystathionine synthase (EC 4 . 2 . I . 22) and N5-methyltetrahydrofolate-homocysteinemethyltransferase (EC 2 . I . I . 13) were determined.3. Weight gain, FCE and urinary urea-N excretion indicated that levels of 3 3 and 4.0 g methionine plus cystine/kg DM were inadequate for optimal growth of the rats. These variables indicated 4.7 g/kg DM to be the requirement for methionine plus cystine. Carcass composition results gave no clear indication of optimal requirements for methionine plus cystine.4. Cystathionine synthase and N5-methyltetrahydrofolate-homocysteine-methyltransferase activities (/mg protein per 60 min) were constant at 24.32 pmol and 0 6 4 nmol respectively, when methionine plus cystine level was between 3 3 and 5.0 g/kg DM. Cystathionine synthase was then inhibited at the 6.0 g/kg DM level to a minimum activity of 16.12 pmol/mg protein per 60 min, whereas activity of the re-methylation enzyme increased to a maximum level of 2.92 nmol/mg protein per 60 min at the 6.0 g/kg DM level of methionine plus cystine. At the levels of methionine plus cystine above 6.0 g/kg DM cystathionine synthase activity increased while the activity of Ns-methyltetrahydrofolate-homocysteine-methyltransferase decreased.Most published estimates of the methionine plus cystine requirements of the growing rat and the growing pig have been based on either growth and nitrogen balance results (Byington,

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