Digestibility of amino acids in swine: Results and their practical applications. A review

Predictions of protein digestibility and lysine absorption in pigs

With 294 feedstuffs-classified into 22 feedstuff categories-, from which in the original literature besides the crude protein (CP) and lysine (lys) contents their precaecal (pc) and partly their total (t) digestibilities in pigs had been presented, assessments of the pc and t apparent digestibilities (AD%) were done by two different ways. Between the prediction possibility using the mean value of nondigestible CP resp. lys (mean ndCP, means ndlys, g/kg DM) and the usual way of calculating average digestive coefficients (mean ADCP%, mean ADlys%) there were with regard to the validity of predictions only small differences, with the tendency of partly more advantageous results by the first cited procedure. Good assessments of pc ADCP% and pc ADlys%, where 70 ... 100 per cent of the single feedstuffs showed prediction errors of only < or = 5 digestibility units, were got for the protein concentrates field bean, lupin, soybean meal, sunflower seed meal, rapeseed meal, yeast and casein as well as with some restrictions for sorghum, linseed meal, blood meal and poultry by-product meal. Less reliable and connected with more uncertainties are the pc digestibility predictions for cereals, peas, cottonseed meals, meat (& bone) meals and fish meals: only 20 ... 30 per cent of the single feedstuffs showed good appraisals with differences < or = 5 digestibility units. In the rule t digestibilities can be assessed more exactly than pc digestibilities, for lys these predictions are mostly less precise than for CP.

Ion-pair high-performance liquid chromatography of diaminopimelic acid in hydrolysates of physiological samples

A method is reported for the determination of diaminopimelic acid (DAPA) in physiological samples. DAPA is derivatized with an o-phthaldialdehyde reagent solution, subjected to reversed-phase high-performance liquid chromatography and detected spectrofluorometrically. The method is a significant advance over previous methods because it uses the ion-pairing agent hexadecyltrimethylammonium bromide (HTMA) to facilitate DAPA measurement. Ion-pairing with HTMA avoids interference with co-eluting derivatives to provide simultaneous, sensitive, reproducible measurement of both DAPA peaks (DD,LL-DAPA and DL-DAPA).

The availability of lysine in diets for pigs: comparative methodology

Four experiments were conducted to compare different methods for estimating the availability of lysine in protein feeds. The same feeds were used in all experiments. In the first experiment the apparent digestibility of lysine to the ileum of growing pigs was found to be 0.92, 0.69, 0.73, 0.85, 0.84 and 0.97 for soya-bean meal, cottonseed meal 1, cottonseed meal 2, meat meal, sunflower meal and skim milk respectively. In the second experiment the utilization of lysine (relative to free lysine) for weight gain, as measured in weaner pigs, was found to be 0.68, 0.73, 0.81, 0.86 and 1.00 for cottonseed meal 1, cottonseed meal 2, meat meal, sunflower meal and skim milk respectively. In Expt 3 diets were formulated to contain soya-bean meal, sunflower meal or cottonseed meal 2 with the same available lysine content from the measurements made in Expts 1 and 2. The feed conversion ratios of weaner pigs given these diets were similar for the three sources of protein when the values were adjusted for the differences in digestible dry matter intake. In the fourth experiment isoenergetic and isonitrogenous diets were formulated with increasing amounts of lysine from synthetic lysine or cottonseed meal 2. The diets were given to weaner pigs and resulted in a curvilinear response to lysine particularly for the cottonseed meal, so that the availability of lysine in cottonseed meal was similar to that of synthetic lysine at low lysine intakes and much lower than synthetic lysine at higher lysine intakes. Possible reasons for the curvilinear responses are discussed.

[Comparison of methods for determining the prececal nutrient digestibility and amino acid absorption of swine with ileorectal anastomoses and ileocecal bridge cannulas]

The apparent precaecal nutrient digestibility and amino acid (a.a.) absorption of 10 diets were estimated in pigs with end-to-side ileorectal anastomoses (IRA) as well as with ileocaecal re-entrant cannulae (IZB). The digestibilities of organic matter and crude carbohydrates were significantly higher in IRA pigs than in IZB pigs in two resp. three diets only. There were no practical important differences for the digestibilities of crude protein and crude fat in all diets. Out of the 180 a.a. absorption comparisons only 20 (i.e. 11%) showed differences larger than 5%-units. The absorption rates of several a.a. were lower in IRA than in IZB pigs and of some other a.a. on the contrary. The methionine absorption of five legume diets and one barley + lysine diet were up to 15% resp. 4%-units lower in IRA pigs. Possibly this was due to the activity of microbes in the rectum in connection with a small intake level of protein bound methionine. In order to minimize such a falsification it is proposed to use the end-to-end anastomosis. The deviations in the apparent a.a. absorption between IRA and IZB pigs can be explained partly by differences in the quantity of precaecally excreted endogenous a.a. per 100 g DM intake.

Utilization of ileal digestible amino acids by pigs: lysine

Two experiments were conducted to determine the utilization of ileal digestible lysine by pigs. In the first, the apparent ileal digestibility of amino acids in cottonseed meal, meat-and-bone meal and soya-bean meal was determined in pigs fitted with 'T'-shaped cannulas. In the second experiment, three lysine-deficient diets were formulated to 0.36 g ileal digestible lysine/MJ digestible energy (DE), with lysine contributed from the three protein concentrates as the only source of lysine in sugar-based diets. An additional three diets were formulated with supplements of lysine to verify that lysine was limiting in the first three diets. The growth performance and retention of lysine by pigs given the six diets over the 20-45 kg growth phase were then determined. The apparent ileal digestibility of lysine in the three protein concentrates (proportion of total) was: cottonseed meal 0.74, meat-and-bone meal 0.78, soya-bean meal 0.89. Growth rates (g/d) of the pigs given the three diets formulated to 0.36 g ileal digestible lysine/MJ DE were significantly different (P less than 0.001): cottonseed meal 377, meat-and-bone meal 492, soya-bean meal 541. The response of pigs to the addition of lysine confirmed that lysine was limiting in these diets. Crude protein (nitrogen x 6.25) deposited by the pigs was significantly higher (P less than 0.001) for those given soya-bean meal (77 g/d), relative to meat-and-bone meal (66 g/d) and cottonseed meal (38 g/d). The proportion of ileal digestible lysine retained by pigs given the three protein concentrates was: cottonseed meal 0.36, meat-and-bone meal 0.60, soya-bean meal 0.75. The results indicate that values for the ileal digestibility of lysine in protein concentrates are unsuitable in dietary formulations as the assay does not reflect the proportion of lysine that can be utilized by the pig. It appears that, with heat-processed meals, a considerable proportion of the lysine is absorbed in a form(s) that is (are) inefficiently utilized.

A comparison of the availability and ileal digestibility of lysine in cottonseed and soya-bean meals for grower/finisher pigs

The availability of lysine and the ileal digestibility of amino acids in three cottonseed meals and a soya-bean meal for grower/finisher 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, 0.68; no. 3, 0.72; soya-bean meal, 0.89. 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.

Biotin studies in pigs. 4. Biotin availability in feedstuffs for pigs and chickens

Six pigs (initial weight 30 kg) were fitted with T-shaped cannulas in the ileum, 0.3 m from the ileocaecal junction. Each pig was given each of seven diets for a 10 d period. The diets contained wheat (var. Banks and Egret), barley, sorghum, meat meal, soya-bean meal or casein as test feedstuffs. The apparent digestibilities of biotin to the ileum of the pigs were 0.06, -0.03, -1.23, 0.18, 0.82, 0.12 and 0.95 for the diets containing wheat (var. Banks), wheat (var. Egret), sorghum, barley, meat meal, soya-bean meal and casein respectively. The same diets were given to 168 chickens. Digesta were collected from the terminal ileum after 7 d. The apparent digestibilities of biotin to the ileum of the chickens were 0.11, -0.10, -0.73, 0.05, 0.69, 0.28 and 0.75 for the diets containing wheat (var. Banks), wheat (var. Egret), sorghum, barley, meat meal, soya-bean meal and casein respectively.