Amino acid requirements of growing pigs 4. Methionine plus cystine

Amino acid requirements of growing pigs 5. The interaction between isoleucine and leucine

Thirty-two female growing pigs (25 to 55 kg live weight) were subjected to four dietary treatments combining two levels of isoleucine and two levels of leucine to investigate the effects of leucine supply on the requirement for isoleucine.

Results for daily live-weight gain, food conversion efficiency and carcass quality judged by ham dissection indicated that 3·8 g isoleucine per kg diet was marginally adequate for the growing pig in diets containing 13·4 g leucine per kg. An interaction between dietary leucine and isoleucine was demonstrated. Increasing the dietary leucine concentration to 20·4 g/kg clearly resulted in a deficiency of isoleucine in the basal diet, as daily gain, food conversion efficiency and carcass quality were significantly improved by increasing the isoleucine concentration from 3·8 g to 4·5 g/kg diet. Dietary leucine concentration did not influence performance at the higher level of isoleucine supply. Changes in plasma urea and amino acid concentrations confirmed the findings from the growth experiment of the interaction between isoleucine, leucine and valine.

Amino acid requirements of growing pigs. 7. The response of pigs from 25 to 55 kg live weight to dietary ideal protein

One hundred and twenty pigs were used in a 3 × 8 factorial design. The factors were sex, 40 trios of littermate boars, castrated males and gilts, and dietary lysine, eight concentrations from 7×5 to 14×5 g/kg diet with 1 g/kg diet intervals of lysine with corresponding crude protein (CP) concentrations from 114 to 226 g/kg diet. Increases in dietary lysine were associated with concomitant increases in the other essential amino acids so as to provide an ideal protein. All diets had similar digestible energy values (13·65 MJ/kg). Pigs were fed once daily on a restricted scale from 25 to 55 kg live weight. For growth and carcass characteristics there was a range of linear response followed by a plateau. The inflexion points of dietary lysine for growth characteristics were at 11·1, 10·2 and 10·9 g/kg diet (171, 157 and 168 g CP per kg diet) together with daily intakes of 18·0, 16·7 and 17·6 g (daily intake of 277, 257 and 271 g CP) for boars, castrated males and gilts respectively. The equivalent points for carcass characteristics were 10·4, 9·7 and 10·1 g/kg (160, 149 and 156 g CP per kg diet) with daily intakes of 16·9, 15·9 and 16·4 g lysine (daily intakes of 260, 245 and 252 g CP). Blood urea data gave good support for these observations.

[The activity of and requirements for selected amino acids in growing female swine. 2. Methionine and cystine]

The methionine/cystine efficiency of ten protein sources including that of different charges of the same protein source was ascertained in N balance experiments with a total of 60 female pigs in the live weight range of 35-50 kg. The variability of the derived sulfur amino acids (SAS) efficiency coefficient (Csas) ranged between 0.64... 0.91 based on the SAS efficiency of casein as a standard. There was an analogous differentiation for the derived requirement values on the basis of the analysed methionine/cystine values of the proteins. For a protein retention of 100 g/day and a live weight of 40 kg, 6.2g methionine/cystine was ascertained based on the highest SAS efficiency (Csas = 1) as yet.