Oven drying improves the nutritional value of Calliandra calothyrsus and Gliricidia sepium as supplements for sheep given low-quality straw

Leaves from the tree legumes Gliricidia (Gliricidia sepium) and Calliandra (Calliandra calothyrsus) were fed as supplements (200 g dry matter) to sheep (n=3) given a basal diet of barley straw ad libitum. Tree leaves were fed either freshly harvested (F=fresh) or after drying at 60°C in a forced draught oven (D=dried). Voluntary intakes, digestibility and aspects of nitrogen (N) and phenolic compound metabolism were measured in all sheep. Drying decreased the condensed tannin (CT) content of Calliandra (F 117, D 82 g CT kg⁻¹ DM). Total phenolics (TP) were significantly decreased when Gliricidia was dried (F 39, D 21 g TP kg⁻¹ DM), and CT content was reduced from 20 g CT kg⁻¹ DM to zero. Sheep given Gliricidia had higher rumen ammonia concentrations (73–85 mg N litre⁻¹) than did sheep given Calliandra (37–40 mg N litre⁻¹). For both species, drying significantly increased the voluntary consumption of straw, increased DM digestibility, decreased faecal N excretion and increased N balance. For calliandra, drying decreased the apparent degradability of N in the rumen (DNR) from 0·40 to 0·28 g N g⁻¹ N ingested, and increased the apparent digestibility of N (ADN) in the post-ruminal tract from 0·20 to 0·52 g N absorbed g⁻¹ N flowing into the small intestines. For Gliricidia, DNR decreased from 0·64 to 0·51 and ADN increased from 0·41 to 0·56. There were no significant effects of drying on rates of microbial N synthesis. The above changes were discussed in relation to changes in tannin content and it was concluded that drying facilitates the formation of protein–tannin complexes which protect proteins from degradation in the rumen. These proteins are subsequently released in the small intestines, thereby promoting an increased efficiency of dietary N utilisation. ©1997 SCI     

Genetic and Environmental Variation for Seed Yield,Protein, Lipid and Amino Acid Composition in Cowpea (Vigna unguiculata (L) Walp)

The genetic and environmental variability for seed yield (kg ha^-1), protein content (g kg^-1 DM), lipid content (mg g^-1 DM) and essential amino acid composition (g per 16 gN) of cowpea seeds using 15 cultivars grown in three locations (Kano (12°00′ N 8°31′ E), Mokwa (9°17′ N 5°04′ E) and Ago-Iwoye (6°58′ N 4°00′ E)) that differ markedly in climate was studied. The environmental effect accounted largely for the variability observed in yield (93%), protein (71%), lipid (100%), threonine (96%), cystine (80%) and arginine (81%) while the genotypic effect accounted largely for the variability observed in methionine (56%) and lysine (51%) contents. Correlation coefficients (pooled data) from the three locations indicated that yield was negatively correlated to protein content (r=-0·87, P<0·001) and positively correlated to lipid content (r=0·73, P<0·001). Protein content was negatively correlated to lipid content (r=-0·67, P<0·001) and positively correlated to threonine (r=0·66, P<0·01), cystine (r=0·69, P<0·001) and methionine (r=0·88, P<0·001) contents. Similarly, yield was positively correlated to threonine (r=0·22, 0·01<P<0·05), cystine (r=0·38, 0·001<P<0·01) and methionine (r=0·67, 0·001<P<0·01). Yield showed a strong negative correlation with protein content (r=-0·81) and a strong positive correlation with lipid content (r=0·97) at the environmental level. Cystine, methionine and to some extent, threonine were the limiting amino acids in the three environments. This research established the degree of variability for these characters in cowpea and indicated that concurrent selection for yield, lipid content, threonine and sulphur amino acids compositions is feasible. © 1997 SCI.     

Effects of ingredients on the characteristics of rice cakes

Steamed leavened rice cakes made from rice flour, sugar, water, yeast or baking powder were used to study the effects of ingredients on cereal-based cakes. Volume expansion linearly correlates to amylopectin and negatively correlates to amylose content (r²=0·84), with an optimum amylose/amylopectin ratio of approximately 1: 8. Higher amylopectin content resulted in sticky, elastic and unacceptable cake. The optimum water content for volume expansion was in the range of 90±5% by weight of rice flour. Sugar content correlates linearly with volume expansion and tenderness of chemically leavened rice cakes (CLRC) (r²=0·99 and 0·92, respectively). Sugar content above 50% of rice flour weight decreased volume and softness of yeast-leavened rice cakes (YLRC). Tenderness of YLRC correlates linearly to fat content (r²=0·98), but volume expansions correlates negatively to the square root of fat content (r²=0·81 and 0·97 for the two rice cakes). Both tenderness (r²>0·92) and volume expansion (r²>0·93) correlates linearly with emulsifier content up to 3% by weight of rice flour, above which the cake becomes crumbly. A little salt increased hardness, but further increase reduced both volume expansion and hardness of rice cakes. Skimmed milk powder greatly increased the expansion of CLRC. Ovalbumin content correlates linearly to volume expansion of YLRC (r²=0·87) but negatively to the expansion of CLRC (r²=0·96). The proteins that improved the textures of rice cakes were skimmed milk and egg white with an optimum content of 2–4%. Egg yolk, soya protein, whey powder and wheat gluten reduced both tenderness and volume expansion. The effects of the various ingredients interacting together were studied and the optimum formulations was determined using a Random Centroid Optimisation Program. © 1998 SCI.     

Effects of intraruminal infusions of propionate and butyrate with two different protein supplements on milk production and blood metabolites in dairy cows receiving grass silage-based diet

Four cows were used in a balanced 4×4 Latin square with 2 week experimental periods to investigate the effects of intraruminal infusions of volatile fatty acids and protein source on milk production and blood metabolites. The four treatments in a 2×2 factorial arrangement were isoenergetic intraruminal infusions of propionate (500 g day⁻¹) or butyrate (417 g day⁻¹) each given with isonitrogenous protein supplementation of fish meal (FM) or barley protein (BP). The cows were fed restrictively with 9 kg dry matter day⁻¹ of formic acid treated grass silage and 8 kg day⁻¹ of concentrate. Propionate infusion increased milk yield (24·9 vs 23·4 kg day⁻¹; P<0·05), milk protein yield (832 vs 778 g day⁻¹; P=0·05) and milk lactose content (44·7 vs 43·5 g kg⁻¹; P<0·05) and yield (1113 vs 1023 g day⁻¹; P<0·01), whereas butyrate infusion was associated with a higher milk fat content (44·7 vs 39·4 g kg⁻¹; P<0·01) and yield (1033 vs 974 g day⁻¹; P<0·01). FM tended (P<0·10) to increase milk yield, but had no significant effects on milk composition or milk component yields compared with BP. Butyrate infusion increased blood ketones, plasma non-esterified fatty acids and glycine relative to propionate infusion. The concentrations of ammonia N in rumen fluid and urea in plasma and milk were similar for both protein supplements. The profile of amino acids in plasma was similar for both protein supplements except for the higher concentrations of phenylalanine, proline and tyrosine with BP. The results show that protein utilisation can be improved by increasing the supply of propionate from rumen fermentation in cows given a grass silage-based diet. © 1998 SCI.     

Response of nutrient digestibilities to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of dietary soybean trypsin inhibitor (SBTI) content on nutrient and energy digestibilities in growing pigs. Six barrows, average initial body weight (BW) 47·8±4·0 kg, were fitted with a simple T-cannula at the distal ileum and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g crude protein (CP) kg⁻¹ from either Nutrisoy (a food-grade defatted soy flour) or autoclaved Nutrisoy. The contents of SBTI in the Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 12 days each. The average BW at the start of the first and second experimental periods were 53·3±3·7 and 61·0±5·1 kg, respectively. The average BW at the conclusion of the experiment was 71·8±7·6 kg. The ileal digestibilities of dry matter (DM), organic (OM), energy, CP and all amino acids measured were higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. The energy digestibility increased from 66·0 to 77·9%, and the CP digestibility increased from 37·4 to 77·1%. The increases in ileal digestibilities of the indispensable amino acids ranged from 27·0 (methionine) to 49·2 (leucine) percentage units. The increases in ileal digestibilities of the dispensable amino acids ranged from 30·2 (aspartic acid) to 50·8 (tyrosine) percentage units. The faecal digestibilities of all criteria measured were also higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. Furthermore, there was a greater (P<0·01) net disappearance (g kg⁻¹ DM intake) of DM, OM, CP, energy and all amino acids in the large intestine of pigs fed the Nutrisoy diet. In conclusion, feeding diets containing high levels of SBTI decreased both ileal and faecal digestibilities of all criteria measured. The formation of SBTI-enzyme complexes is likely to be responsible for the reduction in protein digestion and amino acid absorption. © 1998 SCI.     

Medicagenic acid content in foliage of ten varieties of alfalfa (Medicago sativaL) cultivated in Mexico

Medicagenic acid (MA) content was studied in four Mexican, one Spanish and five USA cultivars of alfalfa (Medicago sativa L) using high-performance liquid chromatography (HPLC) and two bioassays: Trichoderma viride inhibition and ichthyotoxic activity. The MA contents (g kg⁻¹), measured through HPLC, for the 10 varieties were: Valenciana=0·165; Inia 76=0·115; Puebla 76=0·097; Synthetic I=0·042; Pierce=0·031; Maxidor=0·027; Condor=0·024; Synthetic II=0·023; Sundor=0·023; NK-819=0·013. These data confirm the influence of the variety in MA contents. Fungitoxic and ichthyotoxic assays showed that the Spanish cultivar (Valenciana) presented the highest toxicity. The biological activity of the ten varieties was strongly correlated (r=0·97) to medicagenic acid content measured through HPLC. ©1997 SCI     

The Nutritional Value of High-Lysine Barley Determined in Rats,Young Pigs and Growing Pigs

Three experiments, the first with rats, the second with young pigs and the third with growing pigs, were carried out to compare the nutritional value of cv Lysimax, a newly developed high-lysine barley, to cv Lami, a conventional barley grown in Denmark. In the diets for rats and growing pigs the barleys were the sole protein source while in the experiment with young pigs the barleys made up to 649 g kg^-1 of the respective diets. The lysine content of cv Lysimax was 52·6% higher than that of cv Lami; 4·99 g 16 g N^-1 compared to 3·27 g 16 g N^-1. The contents of threonine, tryptophane, methionine and cystine of cv Lysimax were 3·80, 1·41, 1·80 and 2·27 g 16 g N^-1, respectively; being 18·4, 8·5, 9·8 and 5·1% higher than in cv Lami. Conversely, the contents of glutamic acid and proline in cv Lysimax were 15·79 and 7·40 g 16 g N^-1, respectively, being 36·1 and 40·0% lower than in cv Lami. In the experiment with rats, the higher lysine content and the lower content of glutamic acid and proline in cv Lysimax resulted in a 34·8% increase (P<0·05) in biological value (BV); 0·867 for cv Lysimax compared to 0·643 for cv Lami. True protein digestibilities and energy digestibilities in rats fed cv Lysimax were 0·019 and 0·010 units lower (P<0·05) than for cv Lami. For young pigs the increased lysine content and the lower content of glutamic acid and proline of cv Lysimax increased (P<0·05) nitrogen (N) retention from 10·9 to 12·4 g day^-1, respectively, and increased (P<0·05) apparent BV from 0·690 to 0·734, respectively. The digestibility of energy was 0·030 units lower (P<0·05) for the diets with cv Lysimax than for the diets with cv Lami. Likewise, with growing pigs the increased lysine content and the lower content of glutamic acid and proline increased (P<0·05) N retention from 6·4 to 10·8 g day^-1 and apparent BV from 0·271 to 0·495, respectively. The apparent ileal digestibilities of lysine, threonine, tryptophane, methionine and cystine were similar (P>0·05) between the barleys. It is concluded that the development of high-lysine barley varieties could be beneficial for meeting the requirements of essential amino acids for monogastrics. Moreover, N excretion into the environment was substantially reduced due a reduction in the prolamine fraction which is rich in glutamic acid and proline. © 1997 SCI.     

Flavanol Composition and Caffeine Content of Green Leaf as Quality Potential Indicators of Kenyan Black Teas

The flavanol composition and caffeine content of green tea leaf, black tea quality parameters of theaflavins, thearubigins, liquor brightness and total colour varied more among clones than with time of the year. In green leaf, either (-)epicatechin gallate or (-)epigallocatechin gallate was the dominant flavanol present. Regression analysis of tasters' preferences for black teas against green leaf chemical components showed positive and significant correlations for (-)epicatechin gallate (r = 0·498, P ⩽ 0·05 for taster A; r = 0·665, P ⩽ 0·01 for taster B, and r = 0·678, P ⩽ 0·01 for both tasters' overall ranking), (-)epigallocatechin gallate (r = 0·513, P ⩽ 0·05 for taster B; r = 0·532, P ⩽ 0·05 for both tasters' overall ranking and caffeine (r = 0·523, P ⩽ 0·05 for taster A; r = 0·657, P ⩽ 0·01 for taster B; and r = 0·686, P ⩽ 0·01 for both tasters' overall ranking). Similar regressions against black tea theaflavins, thearubigin content, liquor brightness and total colour were not significant. The results suggest that the green leaf chemical components, (-)epicatechin gallate, (-)epigallocatechin gallate and caffeine could be used as quality potential indicators during clonal selection and propagation. © 1997 SCI.     

The glucosinolates sinigrin and progoitrin are important determinants for taste preference and bitterness of Brussels sprouts

The glucosinolates, sinigrin and progoitrin, are related to the bitterness observed in Brussels sprouts. The role of these glucosinolates in taste preference for Brussels sprouts (Brassica oleracea var gemmifera) was studied with two different consumer taste panels and an analytical panel. Four different taste trials were conducted between 1989 and 1995 to study the role of sinigrin and progoitrin on taste preference and bitterness of sprouts. Sinigrin and progoitrin correlated negatively with taste preference of sprouts when their combined content was higher than 2·2 g kg⁻¹. Under these conditions the overall preference for different Brussels sprouts cultivars, in two different trial designs, was accounted for, respectively, 64 (Novartis Seeds BV) and 86% (TNO) by the contents of the glucosinolates sinigrin and progoitrin. In two additional trials, in which the combined content of sinigrin and progoitrin of all cultivars was below 2·2 g kg⁻¹, no relationship between taste preference and the content of both glucosinolates was observed. In the latter trials the content of sinigrin and progoitrin was found to be correlated with bitterness (r²_multiple = 0·67 and 0·93, respectively) as assessed by an analytical panel. The results of the taste trials show that both bitterness and taste preference for sprouts are correlated with the content of sinigrin and progoitrin. Taste preference for sprouts is only correlated with sinigrin and progoitrin when their combined content exceeds 2·2 g kg⁻¹, while bitterness is correlated with both glucosinolates for the whole studied content range. © 1998 Society of Chemical Industry.     

Study of the nutritional value of black cumin seeds (Nigella sativaL)

The nutritional value of five samples of black cumin seeds from five different sources available in the local market were studied. The average values of the proximate analysis on dry matter basis were 216 g kg⁻¹ for crude protein, 406 g fat, 45 g ash, 84 g crude fibre and 249 g of nitrogen-free extract, whereas moisture content was 38 g kg⁻¹. The mineral and vitamin analyses showed that black cumin seeds contained iron, (105 mg kg⁻¹) copper (18 mg), zinc (60 mg) phosphorus (527 mg), calcium (1860 mg), thiamin (15·4 mg), niacin (57 mg), pyridoxine (5·0 mg) and folic acid (160 μg). The protein quality of black cumin seeds was evaluated using net protein utilisation (NPU), protein efficiency ratio (PER) and net dietary protein energy percent (NDPE %) for two samples imported from Syria and Turkey, while PER was determined for the Syrian sample only. The results indicated that the NPU standardised of Turkish black cumin seeds was significantly higher than that of Syrian type (P<0·05). The mean results (±SD) were 54·6±2·72 for the Syrian type and 63·1±3·74 for the Turkish type. The NDPE% mean results (±SD) were 5·3±0·79 and 5·6±0·26 for the Syrian and the Turkish samples, respectively. The PER adjusted value for the Syrian samples was 1·9. The results of protein quality evaluation and those of the nutrient composition suggest that black cumin is of relatively good nutritional value. © 1998 SCI.     

Effects of Silage Fermentation and Post-ruminal Casein Supplementation in Lactating Dairy Cows: 1—Diet Digestion and Milk Production

Two silages were prepared from the first-cut sward of timothy-meadow fescue and wilted to a dry matter (DM) content of 300 g kg^-1. One was ensiled with the addition of a formic-acid-based additive (4 litres formic acid (FA) per tonne) and the other with the addition of a bacterial inoculant (LAB) at a rate of 5×10⁶ colony forming units g^-1. Both silages were well preserved, but the extent of fermentation was greater in LAB-silage than in FA-silage as indicated by a lower concentration of water soluble carbohydrates (68 vs 177 g kg^-1 DM) and a higher concentration of lactic acid (147 vs 32 g kg^-1 DM). Four Ayrshire cows were used in a 4×4 Latin square experiment with 21-day periods to study the effects of silage fermentation and postruminal casein supplementation on silage intake, nutrient supply and milk production. The four treatments were FA-silage without casein (FA-0), LAB-silage without casein (LAB-0), FA-silage with casein (FA-C) and LAB-silage with casein (LAB-C). Both silages were given ad libitum with 8 kg day^-1 of barley without or with 400 g day^-1 of casein infused into the duodenum. Organic matter digestibility was lower (0·723 vs 0·753; P<0·01) for FA-silage than for LAB-silage. Cows offered FA-silage had a higher molar proportion of acetate and a lower proportion of propionate in ruminal fluid than cows offered LAB-silage. Microbial protein synthesis estimated from the output of purine derivatives in urine was greater (288 vs 260 g N day^-1; P<0·05) for cows given FA-silage compared with LAB-silage. Feeding LAB-treated silage tended (P<0·10) to decrease silage DM intake compared with FA-treated silage (10·61 vs 11·77 kg DM day^-1). Silage composition did not affect significantly milk yield or milk composition. Casein infusion increased milk yield (25·1 vs 27·1 kg day^-1; P<0·05), milk protein content (32·4 vs 33·8 g kg^-1; P<0·05) and protein yield (808 vs 905 g day^-1; P<0·01). The responses were similar for both silages. © 1997 SCI.     

Comparative composition of aerial and subterranean potato tubers (Solanum tuberosum L)

The composition of aerial and subterranean tubers of two potato genotypes cvs Desiree (red skin) and Epicure (white skin) was compared immediately after harvest using a range of analytical methods. Irrespective of genotype, aspartic acid, arginine, glycine, glutamic acid, histidine, leucine, serine, threonine and total amino acid concentrations were significantly higher (P<0·05) in aerial compared with subterranean tuber tissue. Significant increases (P<0·05) in valine in aerial tubers, but no significant differences in alanine, tyrosine and iso-leucine, when compared with subterranean tubers of cv Desiree, were found. In cv Epicure, alanine, tyrosine and iso-leucine were significantly higher in aerial tubers (P<0·05); however, no significant differences in valine were recorded. There was no significant increases in lysine and phenylalanine between tuber types. Regardless of genotype α-solanine, α-chaconine, chlorogenic acid, chlorophyll and crude protein concentrations were significantly higher in aerial tubers compared with subterranean ones (P<0·01). No significant increases in total lipids between tuber types were found. In cv Desiree, ascorbic acid content was not significantly different between aerial and subterranean tuber tissue, but in cv Epicure concentrations were significantly higher (P<0·01) in aerial tubers. Starch concentrations were significantly higher in subterranean tubers of both cultivars (P<0·05). Sugar content was significantly higher in aerial tubers of cv Epicure (P<0·01), but not significantly different between aerial and subterranean tubers of cv Desiree. Regardless of genotype, phosphorus, magnesium, potassium, zinc, manganese and sodium concentrations were significantly higher (P<0·05) in aerial tubers. Iron and copper concentrations were significantly higher in aerial tubers of cv Desiree (P<0·01), but significantly less in cv Epicure compared with subterranean tubers (P<0·01, P<0·05). Calcium concentrations were not significantly different between aerial and subterranean tubers of cv Desiree, but significantly higher in aerial tuber tissue of cv Epicure (P<0·01). Total gross energy (mJ kg⁻¹ FW) was higher in aerial tubers of cv Desiree compared with subterranean tubers (P>0·05), but not significantly different between aerial and subterranean tubers of cv Epicure. The potential applications of aerial tubers for industrial purposes are discussed. © 1997 SCI.     

Chemical characterisation and ruminal nutrient degradability of hulled and hull-less oats

The objectives of this study were to determine the chemical and ruminal nutrient degradability characteristics of two hulled (Calibre and AC Mustang) and one hull-less (AC Belmont) oat varieties. Ruminal nutrient degradability characteristics of the oat varieties were determined relative to barley using one ruminally fistulated cow. Neutral (NDF) and acid (ADF) detergent fibre levels were higher (P < 0·05) in hulled than hull-less oats. Hulled AC Mustang had higher (P < 0·05) NDF and ADF content than hulled Calibre. Starch content was higher (P < 0·05) in AC Belmont (590 g kg⁻¹) than Calibre (457 g kg⁻¹) and was higher in Calibre than AC Mustang (415 g kg⁻¹). Crude protein was higher (P < 0·05) in hull-less than hulled oat. Both hulled varieties had similar CP content (average 124 g kg⁻¹). Estimated digestible energy value was highest (P < 0·05) for AC Belmont (16·94 MJ kg⁻¹), intermediate for Calibre (14·18 MJ kg⁻¹) and lowest for AC Mustang (13·34 MJ kg⁻¹). Ruminal dry matter and NDF degradability were higher (P < 0·05) in hull-less than barley and was higher in barley than hulled oats. Ruminal starch degradability exceeded 900 g kg⁻¹ for all tested feeds and had the order AC Belmont = barley > Calibre = AC Mustang. It was concluded that oat varieties used in this study varied considerably in their chemical composition and ruminal degradability. When compared with barley, hulled oats had lower while hull-less oats had higher ruminal degradability. © 1998 SCI.     

Dietary manipulation of the yield and composition of milk: Effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition

Eight 1st-lactation cows were given four dietary treatments in a duplicated 4×4 Latin square experiment. Diets consisted of hay and soya bean meal together with barley, formaldehyde-treated barley, oats or formaldehydetreated oats (approximately 34:12:54 on a dry matter basis). Barley diets supplied 211 g fatty acids d^?1, oats diets supplied 537 g d^?1. The fatty acid composition (g kg^?1 total fatty acids) for barley diets was: 300 (16:0); 20 (18:0); 150 (18:1); 470 (18:2); 60 (18:3). Corresponding values for oats diets were 180, 20, 390, 380 and 30 g kg^?1. Formaldehyde treatment of the cereals tended to increase milk yield and reduce milk fat content (P<0·01 for barley) but did not affect milk fatty acid composition. Feeding oats in replacement for barley significantly (P<0·05) increased milk yield and lactose yield and reduced milk fat content (P<0·05 for the untreated cereals) and protein contents (P<0·01) without significant effects on milk fat or protein yields. Oats diets led to significant (P<0·001) reductions in the content of 8:0–16:0 fatty acids in milk fat with associated increases (P<0·001) in the content of 18:0 and 18:1. Changes in milk fat content of 18:2 and 18:3 acids were small. The results show the inclusion of oats in the cow's diet to be a means of reducing the saturated fatty acid content of milk fat thereby improving the nutritional value of milk and milk products and their appeal to the health-conscious consumer.     

Combined Effect of Drying Time and Slice Thickness on the Solar Drying of Okra

The effect of slice thickness and drying time on colour, viscosity, microbial load, moisture, crude fibre, vitamin C and ash contents of okra (Hibiscus esculentus) during solar drying was studied using three slice thicknesses (5·0 mm, 10·0 mm, 15·0 mm) obtained from a survey and five drying times (0, 24, 48, 72 and 96 h). The results showed that slice thickness had a significant effect (P<0·01) on moisture, crude fibre and ash contents but not on vitamin C content, viscosity, colour and microbial load. However, the effect of drying time was highly significant (P<0·01) on all the parameters determined. The combined effects of slice thickness and drying time were observed to be highly significant (P<0·05) on ash, crude fibre and moisture contents, viscosity and microbial load but had no significant effect (P<0·05) on colour and vitamin C content. There was a strong correlation between moisture content and ash (R=-0·926), crude fibre (R=-0·94), vitamin C contents (R=0·928) and viscosity (R=-0·963) in all samples during drying. The study showed that a slice thickness of 10·0 mm and a drying time of 48 h was suitable for the solar drying of okra. © 1997 SCI.     

The apparent ileal digestibility of amino acids and the digestible energy content of naked oats (Avena sativa cv Bandicoot) fed to growing pigs

An experiment was conducted to determine the apparent ileal digestibility of amino acids and the digestible energy (DE) content of two samples of naked oats (Avena sativa cv Bandicoot) and to compare these parameters in wheat (Triticum aestivum cv Machete) and dehulled oats (groats; Avena sativa cv Echidna). Four Large White male pigs were fitted with simple T-piece ileal cannulae and allocated to experimental diets in a 4×4 Latin square design. Amino acid digestibility coefficients were determined after continuous eight hour collections of digesta over two consecutive days using acid-insoluble ash as an indigestible marker. Digestible energy was determined using grab samples of faeces. No significant difference between the four test cereals was found in the digestibility of all amino acids, except for proline and lysine. The apparent ileal digestibility of lysine in wheat (0·87) and two samples of naked oats (0·89 and 0·82, respectively) was lower (P<0·05) than dehulled oats (0·91). The mean DE value of the naked oats samples was 16·96 MJ kg⁻¹ (air-dry basis). The results suggest that Bandicoot naked oats and dehulled oats are superior amino acid and DE sources to wheat and have potential for use in weaner and grower pig diets. © 1998 SCI.     

Response of pancreatic secretions to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of soybean trypsin inhibitors (SBTI) on exocrine pancreatic secretions in growing pigs. Six barrows with an average initial body weight (BW) of 27·1±1·4 kg were fitted with permanent pancreatic re-entrant cannulas and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g kg⁻¹ crude protein from either Nutrisoy (food grade defatted soy flour) or autoclaved Nutrisoy. The concentrations of SBTI in Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 9 days each. The average BW at the start of the first and second experimental periods was 33·5±2·7 and 37·2±3·7 kg, respectively. The average BW at the conclusion of the experiment was 41·8±3·9 kg. The volume of pancreatic secretion was higher (P<0·01) when the Nutrisoy, as opposed to the autoclaved Nutrisoy diet was fed (3804 vs 2634 ml (24 h)⁻¹). The concen-tration of nitrogen and protein and specific activities (units litre⁻¹) of amylase, chymotrypsin and trypsin were lower (P<0·05) in pancreatic juice of pigs fed the Nutrisoy diet. There were no differences (P>0·05) in the total secretions of nitrogen (g (24 h)⁻¹) and total activities (units (24 h)⁻¹) of amylase, lipase, chymotrypsin and trypsin in pancreatic juice of pigs fed the Nutrisoy and autoclaved Nutrisoy diets. However, the total secretion of protein was slightly higher (25·7 vs 22·8 g (24 h)⁻¹; P<0·05) in pancreatic juice of pigs fed the autoclaved Nutrisoy diet, which corresponded with the increase in the secretion of protein-bound amino acids. There was also an increase in the total secretion of free amino acids in pancreatic juice. These studies show no effect of SBTI on the total enzyme activities in pancreatic juice of growing pigs. © 1998 SCI.     

Changes in cell-wall composition and degradability of sorghum during growth and maturation

Samples of sorghum (Sorghum bicolor Moench × Sorghum sudanense Stapf, cv ‘P 988’) were harvested at five growth stages. Quantitative methylation and acetalation–methylation methods were used to examine changes during growth of cell-wall polysaccharides, their association with phenolic compounds and the effects of changes on rumen degradability. Cellulose degradability, as measured by a nylon-bag method, decreased from 82·5% at the youngest stage to 36·5% at the milk-ripe stage, at a greater rate of change than degradability of dry matter. Among the monosaccharides contributing to cell-wall polysaccharides, the degradabilities of arabinose and uronic acid residues were consistently higher than those of xylose and glucose, the main components of structural carbohydrates. Recovery of parent neutral sugars from cell wall polysaccharides, calculated as the sum of partially methylated alditols, was in good agreement with the values obtained by direct estimation of individual sugars as their alditol acetate derivatives. Total non-starch polysaccharide content increased from 31·1% to 45·1% between the first two growth states, with little change evident thereafter. The relative proportion of individual to total sugars remained consistent throughout growth. The values for arabinose, xylose and glucose residues accounted for 4·9%, 27·9% and 63·0% of total neutral sugars, respectively. The pattern of glycosidic linkages detected could be mainly ascribed to the presence of (1–4)-β-D -glucans (cellulose), arabinoxylan, (1–3)(1–4)-β-D -glucans, (1–4)-β-D -galactan, (1–3)(1–6)-β-D -galactan, rhamnogalacturonan and, possibly, xyloglucan. The cellulose content of the five sorghums was, in order of growth, 14·3%, 21·8%. 22·3%, 21·2% and 22·0% of dry matter. The ratio of the mixed-linked g1ucan:cellulose decreased during growth. Arabinoxylan, the predominant hemicellulosic polysaccharide, was estimated to comprise about 33% of total neutral sugars consistently for all sorghum samples. Arabinose, found largely as terminal residues in the cell walls, carried various amounts of alkali-labile substituents, particularly at position 0–5, depending on the growth stage of sorghum. The extent of 0–5 substitution was closely correlated with both the lignin content (total phenolics minus phenolic acids, r = 0·903) and with cellulose degradability (r = 0·915).     

Compositional analysis and viscosity measurements of commercial oat brans

Chemical analysis of commercial oat brans (n=10) collected from five different countries showed wide variations in the contents of starch (40–61%), crude protein (9·6–21%), crude fat (8·2–12%), ash (2·0–4·1%), dietary fibre (10·7–19·4%) and mixed-linkage β-glucan (4·7–8·3%). A significant correlation (r=0·83; P<0·005) between the contents of total and extractable mixed-linkage β-glucan was found. Reproducible increases in viscosity were noted for all samples when the finely ground samples were dispersed in phosphate buffer and viscosity development was followed for 100 min. Addition of mixed-linkage β-glucanase greatly reduced the viscosity. Addition of amyloglucosidase, with no detectable mixed-linkage β-glucanase activity, increased viscosity, which could be related to an increased solubilisation of mixed-linkage β-glucan. Highly significant correlations (r>0·90) were found between the contents of both total and extractable mixed-linkage β-glucan and viscosity after dispersion. © 1998 SCI.     

Wet Milling Comparison of Quality Protein Maize and Normal Maize

Quality protein maize (QPM) experimental hybrids and normal maize possessing different physical and chemical properties were studied as the raw material for wet milling. Maize samples were steeped for 36 h in a 600-ml solution containing 15 g kg⁻¹ lactic acid and 0·5 g kg⁻¹ SO₂ followed by 12 h in a second 600-ml solution containing 5 g kg⁻¹ lactic acid and 1 g kg⁻¹ SO₂. The steeped grain was then wet milled and the yields and purity of fractions were analysed. Water-soluble solids, kernel size, quality protein, total dietary fibre and ash content were higher in QPM samples than in normal maize. Water-soluble solids were positively correlated to kernel size ( r =0·97, P< 0·05), test weight ( r =0·83, P< 0·05) and density ( r =0·57, P< 0·05). Total fraction recovery for the five hybrids tested ranged from 921 to 955 g kg⁻¹, with the highest values corresponding to QPM hybrids. QPM hybrids yielded slightly higher starch content than normal maize. Gluten yields of QPM-HO (high oil) presented the highest values. The lysine contents of kernel, gluten and milling solubles were highest for QPM hybrids. QPM contained more palmitic acid than the other hybrids. The H-137 normal maize and QPM yellow dent-HO contained more oleic and linolenic acids than the other samples, and the QPM white-C (corneous) contained more linoleic acid than QPM-HO and normal maize.