An investigation was carried out to determine the suitability of the screw cap tube method of acid hydrolysis with nitrogen flushing for routine amino acid analysis of animal feeds. Amino acid values determined by the screw cap tube method were compared to those from three other methods, including the conventional reflux method under nitrogen for soybean meal, wheat, meat and bone meal, and casein.The screw cap tube method was shown to be suitable for routine analysis of animal feeds, since similar results to the reflux method were obtained. Methionine was unstable during acid hydrolysis without prior oxidation, for all methods, particularly in soybean and wheat samples, but not in casein. Therefore for routine analysis of animal feeds methionine should be preoxidized to methionine sulfone before acid hydrolysis. Similar values were obtained for methionine and cystine plus cysteine in animal feeds using two different preoxidation procedures.
Forty-three entire males were used to determine the pig's tissue requirements for protein and amino acids from 8-0 to 20-0 kg, and provide information on the capacity of diets formulated with conventional ingredients to contain the same levels and balances of amino acids as ideal protein to supply these nutrients. Seven diets with similar digestible energy (15-9 MJ digestible energy (DE) per kg) and crude protein concentrations from 119 to 232 g/kg (8-7 to 17-3 g lysine per kg) were offered ad libitum between 8-0 and 200 kg live weight. The rate of protein deposition was determined by comparative slaughter. The composition of the protein deposited in the whole empty body was determined from amino acid analyses of pigs killed at 8-0 kg and from the two extreme dietary treatments at 20-0 kg. Growth performance and the rates at which protein and lysine were deposited in the empty body increased linearly with increasing dietary protein concentration up to 187 g/kg and remained relatively constant thereafter. The corresponding dietary protein and lysine intakes required to support maximal protein accretion were 178 g/day (11-7 g/MJ DE) and 13-0 g/day (0-84 g/MJ DE) respectively. Based on the maximal deposition rates for protein (91-8 g/day), and lysine (5-96 g/day) and endogenous protein loss (7-6 g/day) estimated from the linear component of the relationship determined between protein deposition and apparent digestible protein intake, the pig's tissue requirements for protein and lysine were only 99-4 g/day (6-5 g/MJ DE) and 6-46 g/day (0-43 g/MJ DE) respectively. This disparity between the pig's tissue protein and amino acid requirements and the dietary levels needed to support these was associated with the fact that the apparent digestibility and biological value of the dietary protein were 0-92 and 0-602 respectively. Apart from small differences in the lysine content of body protein and the methionine : lysine ratio, the average amino acid composition of pigs killed at 8-0 kg, and from the diet of highest protein concentration at 20 kg, was similar to that of ideal protein, indicating that the low utilizability of dietary protein for tissue growth and maintenance was probably associated with low amino acid digestibility and/or availability. The implications of the results with respect to expression of the growing pig's requirements for protein and amino acids are discussed.
The ileal digestibilities of dry matter (DM), nitrogen (N), energy and amino acids were measured using pigs prepared with either re-entrant or simple ileal cannulae and fed a basal wheat diet, a wheat/lupin diet and a wheatlmeat and bone meal (MBM) diet. The same pigs were also used to determine the faecal digestibilities of DM, N and energy in these diets. Addition of lupins to the basal diet had no significant effect on the true digestibilities of amino acids but addition of MBM significantly (Pc0.01) reduced amino acid digestibility. It was calculated that an average of about 90% of the amino acids in lupin and wheat but only 65% of those in MBM were absorbed from the stomach and small intestine of the pig. Compared to lupin and wheat, a much larger proportion of the protein in MBM disappeared in the large intestine (approximately 4, 6 and 150,; respectively). On the other hand, a large proportion of the energy in lupins but little of that in wheat and MBM (32, 8 and 4 % respectively) disappeared in the large intestine. There were no significant differences between the re-entrant and simple cannulae for ileal digestibility values of DM, N and amino acids. IntroductionMeat and bone meal (MBM) and lupins (L. aagustifolius) are sources of dietary protein and energy often used for pigs in Australia. It is important to specify their nutritive value and clearly, this must include an estimate of nutrient availability.Recent estimates of Iysine availability obtained by slope-ratio assays with pigs show that about 50% of the lysine in MBMl and between 25 and 45% of that in lupins2s3 was not available to the pig. It was suggested173 that protein damage during processing impaired lysine availability in MBM but that the cause of low availability of lysine in lupin was unclear.3 Furthermore, little is known of the availability of other amino acids in these feeds.The digestibility of a nutrient is generally the major factor affecting its availability to the animal for production. However, the value of digestibility measurements in this regard depends upon the site at which digestibility is measured. For example, Zebrowska4 found that amino acids that disappear in the hind gut and subsequently contribute to faecal digestibility values, were not absorbed and hence were not available to the pig. The present work was undertaken, therefore, to compare the extent and site of digestion of protein and energy of various feeds by the pig. This paper reports values of ileal and faecal digestibilities of nitrogen (N) and energy and ileal digestibilities of amino acids in wheat, lupins and MBM. A comparison is also made between ileal digestibility values determined by the use of pigs with simple or re-entrant cannulae.
An investigation of in vitro enzymatic amino acid digestibility of autoclaved rapeseed meals using the enzyme pronase is presented. A correlation coefficient of 0.991 was obtained when comparing in vitro "available" lysine with "Silcock available" lysine. Autoclaving of rapeseed meal for periods of 15, 30, 60, 120 and 180 min at 103 kPa and 120°C caused the following chemical changes. Lysine, methionine and cysteine in vitro digestibilities were markedly decreased as to a lesser extent were the other amino acids. Conversion of methionine to methionine sulphoxide occurred. Deactivation of trypsin inhibitor from 3.8 units of trypsin inhibitor/mg rapeseed for the non-autoclaved meal to zero for the 15 min autoclaved meal was observed. The in vitro enzymatic method described shows considerable promise as a technique to measure amino acid availability.
Effects of dietary protein concentration on the amino acid composition of sow's milk was studied using 10 crossbred first-litter sows. At parturition, diets containing similar concentrations of digestible energy but with either 63 or 238 g crude protein per kg and 4.4 and 15.1 g lysine per kg respectively, were given through lactation (five sows per treatment). The ratios of other amino acids to lysine were in excess of those currently recommended for lactating sows. Dietary protein level significantly affected milk yield, gave higher milk protein output (P> 0.05) but was without significant effect on the proportions of amino acids in the milk.
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