A series of experiments was designed to evaluate inert markers employed in studies of ileal and faecal apparent digestibilities of nitrogen and amino acids in pigs fitted with simple 'T' piece cannulas. Trial 1 assessed the palatability of diets containing (a) 5 g chromic oxide/kg, (b) 1 and (c) 5 g titanium dioxide/kg at two levels of feeding. The results indicated that there were slight problems in terms of period of feed consumption associated with diets (a) and (c), but that these effects were transitory and disappeared following acclimatization, although higher levels of feeding may compound the problem. Trial 2 estimated N balance, faecal apparent digestibility of amino acids as determined by both total collection and ratio of markers, ileal apparent digestibility of amino acids and recovery of markers using diets containing (a) 1 and (b) 5 g Cr,O,/kg, (c) 1 and (d) 5 g TiO,/kg. An additional assessment of acidinsoluble lignin present within the diet was also undertaken. Cr,O, was associated with the lowest recovery, whilst calculations based on TiO, gave lower standard errors. Trial 3 examined diurnal variation in digesta sampling and its effect on faecal apparent digestibility of N and amino acids. There were no evident effects. In general, it was concluded that the most appropriate marker to use in studies of this nature was TiO, at a rate of 1 g/kg.

Data from experimental programmes designed to investigate the effect of chemical structure of fats upon their apparent digestible energy (DE) value for pigs were subjected to regression analysis. For growing pigs, over the approximate live-weight range 30 to 90 kg, 25 data points were available, with fats evaluated having a range in the ratio of unsaturated to saturated fatty acids (U/S) from 0-66 to 15-67 and in free fatty acid (FFA) content from 8 to 818 g/kg. Sixteen data points were available for young pigs of approximately 12 kg live weight with a range in U/S from 0-62 to 5-71 and in FFA content from 54 to 756 g/kg. The wide range of values for U/S and FFA content had been obtained by blending different fats and, therefore, represented both the range and extremes likely to be found in the formulation of pig diets. Derivation of prediction equations for DE were based upon a series of non-linear regression analyses employing, in sequence, U/S, U/S + FFA content and U/S X FFA content. The DE of fats could be predicted from U/S and FFA content with equations accounting for 0-802 and 0-768 of the variation in DE values for growing and young pigs respectively. The most appropriate equation for pigs of all live weights employed U/S and FFA content additively (U/S + FFA content). The equation for growing pigs was DE (MJ/kg) = 36-898 -(0-0046FFA (g/kg)) -7-33e(-0-906U/S) and for young pigs was DE (MJ/kg) = 37-890 -(0-0051FFA (g/kg)) -8-20e(-0-515U/S). Comparisons revealed that differences between the two age groups, with lower values achieved with younger pigs, -were more pronounced the lower U/S and the higher FFA content of the fat.

No abstract

A batch offish meal was (a) untreated, (b) heated to 130°C and (c) heated to 160°C under controlled conditions.In trial 1, these materials were incorporated into a diet based on barley meal (278·7 g/kg), wheat starch (412·5 g/kg), maize meal (245·3 g/kg) and tallow (33·5 g/kg) at a rate of inclusion of 100 g/kg. Diets contained a vitamin/mineral pre-mix together with the inert marker titanium dioxide and were given to four pigs fitted with simple T-piece Heal cannulas over four time periods each of which lasted for 6 days and which allowed the determination of faecal and Heal apparent digestibilities of nitrogen and amino acids. The results indicated that over-heating fish meal results in a reduction in both Heal and faecal apparent digestibility although, as there was no effect of treatment on the quantity of nitrogen absorbed from the large intestine, the two measurements were directly related. Heal and faecal apparent digestibilities for individual amino acids were not the same as data for nitrogen and, accordingly, the latter cannot be used to predict the two former.In trial 2, the three fish meal samples were included in diets formulated on the basis of total, faecal and Heal apparent digestible amino acids. The nine diets were given to pigs over the live-weight range 27·5 to 52·5 kg. Giving diets formulated on the basis of both faecal and Heal apparent digestible amino acids resulted in improved performance compared with giving diets based on total amino acids when the diets containing fish meal heated to 160°C, but performance achieved with diets containing untreated fish meal was still higher.Heal apparent digestible amino acids from heat-treated fish meal are not completely available to the pig, and it is suggested that care needs to be taken in equating digestibility with subsequent availability. There appears to be no advantage of using Heal rather than faecal, apparent digestible amino acid values in texms of accuracy of diet formulation.

No abstract