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A nutritional evaluation of buckwheat (Fagopyrum esculentum)
Animal Feed Science and Technology, 3 ( 1 9 7 8 ) 9 5 - - 1 0 8
95
© Elsevier Scientific P u b l i s h i n g C o m p a n y , A m s t e r d a m - - P r i n t e d in T h e N e t h e r l a n d s
A N U T R I T I O N A L E V A L U A T I O N O F B U C K W H E A T (FAGOPYR UM
ESC ULENTUM) D.J. F A R R E L L
Department o f Biochemistry and Nutrition, University o f New England, Armidale, N.S. W. 2351 (Australia) ( R e c e i v e d 18 N o v e m b e r 1 9 7 7 )
ABSTRACT Farrell, D.J., 1978. A n u t r i t i o n a l e v a l u a t i o n of b u c k w h e a t (Fagopyrum esculentum). Anita. Feed Sci. Technol., 3: 9 5 - - 1 0 8 . E x p e r i m e n t s were c o n d u c t e d w i t h rats, pigs, c h i c k e n s a n d laying hens. B u c k w h e a t h a d a high n e u t r a l d e t e r g e n t fibre c o n t e n t o f 20%; digestible energy m e a s u r e d w i t h pigs was 11.5 MJ/kg, a n d a m e a n m e t a b o l i z a b l e e n e r g y value o f 11.0 M J ] k g w i t h p o u l t r y . G r o w t h studies w i t h rats a n d chicks s h o w e d t h a t b u c k w h e a t in m o n o - g r a i n diets was s u p e r i o r t o cereal grains. However, it was n o t possible t o i d e n t i f y l i m i t i n g a m i n o acids in b u c k w h e a t , a n d s u p p l e m e n t a t i o n w i t h fat a n d p r o t e i n sources did n o t p r o m o t e t h e g r o w t h responses a n t i c i p a t e d . R e m o v a l o f t h e fibrous hulls f r o m b u c k w h e a t b y sifting did n o t increase g r o w t h rate, b u t f o o d c o n v e r s i o n was i m p r o v e d . A l t h o u g h c h e m i c a l analysis i n d i c a t e d t h a t a m i n o acids were a d e q u a t e t o m a i n t a i n egg p r o d u c t i o n , this was n o t c o n f i r m e d in laying trials even w h e n a d d i t i o n s o f lysine a n d m e t h i o n i n e were m a d e t o b u c k w h e a t . T h e m o s t favourable r e s p o n s e to b u c k w h e a t was achieved in pig-growth studies. G r o w t h rate o n a n a l l - b u c k w h e a t d i e t was n o t d i f f e r e n t f r o m t h a t o n a n all-wheat (12% CP) diet b u t a d d i t i o n of lysine i m p r o v e d g r o w t h r a t e a n d feed conversion. A d d i t i o n o f 10% m e a t meal or s u n f l o w e r meal to b u c k w h e a t gave similar g r o w t h a n d feed c o n v e r s i o n to t h o s e o f a c o m m e r c i a l grower diet. A m i n o acid disappearance, m e a s u r e d at t h e t e r m i n a l i l e u m o f pigs p r e p a r e d w i t h r e - e n t r a n t cannulas, gave values ranging f r o m 90% for m e t h i o n i n e to 65% for leucine, a l t h o u g h t h e r e was s u b s t a n t i a l variat i o n a m o n g pigs. It was a p p a r e n t t h a t b u c k w h e a t as t h e sole grain s o u r c e was n o t s u i t a b l e for the species e x a m i n e d . D i f f e r e n c e s in p e r f o r m a n c e b e t w e e n individual animals m a y be a t t r i b u t e d t o t h e i r c a p a c i t y to degrade t h e b u c k w h e a t fibre. T h i s m a y in p a r t e x p l a i n the v a r i a t i o n in the r e s p o n s e o f individuals t o t h e e x p e r i m e n t a l diets a n d t h e r e f o r e a t e n d e n c y to m a s k responses t o t h e various s u p p l e m e n t s . I t can be c o n c l u d e d f r o m this s t u d y t h a t b u c k w h e a t as t h e sole s o u r c e of energy is u n s u i t a b l e for pigs a n d p o u l t r y even t h o u g h in t h e diets of pigs it gave a c c e p t a b l e g r o w t h rate a n d feed conversion. S o m e pigs, h o w e v e r , did n o t take readily t o this grain a n d o f t e n t o o k several h o u r s to c o n s u m e t h e i r rations. P o o r a c c e p t a b i l i t y , p e r h a p s d u e t o the p r e s e n c e o f a t o x i n or o t h e r c h e m i c a l c o m p o u n d s , a p p e a r s t o be associated w i t h this grain.
INTRODUCTION
B u c k w h e a t (Fagopyrum esculentum) is a s u m m e r annual, w i d e l y g r o w n
96
throughout the world. The majority of the grain produced in Australia is milled and used in the diets of man. Although buckwheat is n o t a cereal (Gramineae) it does have a number of chemical characteristics in c o m m o n with cereal grains, particularly in relation to its protein concentration, starchy endosperm and oily embryo. The amino acid profile (Pomeranz and Robbins, 1972) suggests that the protein may be of high biological value. Agronomically, buckwheat has some attractive features. It will grow from planting to harvesting in 10--12 weeks, making its best growth in cool areas, and will often yield a better crop on poor soil than the cereal grains. The object of this study was to investigate the chemical composition and nutritive value of Australian-grown buckwheat for various species of domestic animals. A preliminary report on some of this work was published by Farrell (1976). MATERIALS AND METHODS All experiments were carried out on milled buckwheat (cultivar ' T o k y o ' ) taken from the same batch. Chemical composition of diets and excreta was determined by standard procedures (Association of Official Agricultural Chemists, 1970), and the method of Van Soest and Wine {1967) for neutral detergent fibre (NDF); individual amino acids were determined on the acid hydrolysates (Spackman et al., 1958) using a T.S.M.-1 Technicon Analyser. Faeces and excreta were dried to constant weight in a forced-draught oven at 105°C.
Digestibility and metabolizability Apparent digestibility of dry matter, nitrogen (N) and energy of buckwheat was determined by total collection of faeces for 4 days from each of four pigs (20 kg) accustomed to receiving 1 kg of buckwheat daily, and housed in metabolism crates. Metabolizability of the diet, w i t h o u t correction to N equilibrium, was determined by total collection of excreta for 5 days from two groups of 5 chickens aged 3 weeks offered diets of buckwheat ad libitum. Similar determinations were also made on groups of chickens offered all-wheat, or all-oat diets. Metabolizability of buckwheat was also determined with each of four laying, cross-bred hens in individual cages. Excreta were collected for 5 days. Bone meal, limestone and a commercial mineral and vitamin premix were added to the mono-grain diets in recommended amounts. At least 3 days were allowed for animals to become accustomed to the experimental conditions.
Rat growth study There were six experiments. Weanling rats of the Wistar strain were housed individually in wire-mesh cages in a temperature-controlled room (22 + 2°C).
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There were 5 or 6 animals on each dietary treatment, and food and water were always available. Rats and their f ood containers were weighed initially and at intervals o f 5 days. Experiments continued for 10 or 12 days, b u t all data were corrected to a 10-day period. Most o f the diets were based on b u c k w h e a t supplemented with individual, and various combinations of, crystalline amino acids, with di-ammonium citrate as a non-protein nitrogen (NPN) source, with protein concentrates, and with o th er grains and fat. Bone meal, sodium chloride, and a mineral and vitamin supplement (Ivan and Farrell, 1975) were added to all diets. In E x p e r i m e n t 6, de-hulled (sifted) b u c k w h e a t with amino acid additions was compared with wheat with amino acid additions.
Chick growth study There were two experiments. In the first, 28 groups of ten cross-bred cockerels, aged 7 days, were selected for u n i f o r m i t y of weight and each group was placed separately in a c o m p a r t m e n t in electrically heated b a t t e r y brooders with wire-mesh floors and offered one of 14 diets. Most of the diets were buckwheat-based, and several were supplemented with crystalline amino acids which appeared to be limiting on the basis o f chemical analysis. Diets based solely on wheat, oats and maize were also included. Bone meal and a mineral and vitamin supplement were added to all diets. After 10 days the groups of chickens and their food containers were again weighed. In the second e x p e r i m e n t 18 groups of eight 3-day-old cockerels of a commercial broiler strain were placed in small cages in a ventilated, heated r o o m initially at 33°C and offered one of six diets based on buckw heat supplemented with protein sources, essential amino acids, or di-ammonium citrate as a NPN source. After 10 days the groups of chickens and their f o o d containers were again weighed. A commercially available grower diet was included as a control in the experiments. Water was freely available, and illumination was for 24 h.
Laying trial Seventy-two White Leghorn hens in their first year of lay and in p r o d u c t i o n for a b o u t six m o n t h s were r a n d o m l y allocated in pairs to single-deck wire cages in a conventional layer shed. All cages were equipped with trough feeders and drinkers. After a preliminary period of one week when hens became accustomed to the experimental conditions, measurements c o m m e n c e d and co n tin u ed for 70 days. Egg p r o d u c t i o n and f o o d intake were recorded each week, and hens were weighed at the start and finish of the experiment. There were two experimental diets (Diets 1 and 2) and a commercial layer's diet which was used as a control. Both experimental diets contained b u c k w h e a t as the sole protein and energy sources. All diets were supplemented with 0.2 NaC1, and limestone and bone meal in amounts sufficient to m eet the
98
calcium and phosphorus allowances of the laying hen (Agricultural Research Council, 1975). A commercially-available mineral and vitamin supplement was included. In addition, Diet 2 contained 0.25% L-lysine HC1, and 0.07% DL-methionine but was otherwise the same as Diet 1. Determined ME of the latter diets was 9.5 MJ/kg.
Pig growth study There were two experiments. In Experiment 1, thirty Large White X Landrace castrate male pigs (15 kg) were placed in individual pens in a temperaturecontrolled piggery. Following a period of adjustment on a commercial grower diet, five pigs (18 kg) were allocated to each of six diets shown in Table I. They were offered restricted amounts of food calculated from liveweight (W, kg) by the formula (Ivan and Farrell, 1975) Digestible energy intake (MJ/day) = 1.36 W°.75 Digestible energy of the diets was computed from values for each ingredient and determined for the commercial diet at this laboratory (Ivan et al., 1975a, b). Pigs were weighed each week, and food allocation was adjusted accordingly for the following week. In Experiment 2, twenty Large White X Landrace entire male pigs were used; experimental conditions were similar to those described. Five pigs were offered each of four diets shown in Table I. A commercial grower diet was used as the control. In both experiments it was planned to grow pigs to 44 kg.
Disappearance of amino acids at the terminal ileum Measurement of disappearance of some dietary amino acids at the terminal ileum was made on three pigs (100--110 kg) fitted with re-entrant cannulas (Holmes et al., 1973a, b). The procedures followed were essentially those described by Ivan and Farrell (1976). The pigs were fed, at 12 h intervals, one kg of a diet containing 0.5 kg of whole buckwheat or sifted buckwheat, and 0.5 kg of a synthetic diet. This contained (g/kg) 698 corn starch, 214 sucrose, 54 maize oil, 27 bone meal, 6 salt, and a mineral and vitamin supplement. Total collection of digesta was made on eight occasions for 12 h from the ileal cannula and commencing immediately after the morning feeding. A 10% portion of the weighed digesta was retained and freeze-dried for amino acid analysis; the remainder was returned through the cannula at frequent intervals. Disappearance of amino acids was calculated by comparing dietary amounts with those in the total digesta collected, and expressing the values as "percentage disappearance".
Statistical methods Analyses of variance and covariance were used. For growth studies, initial
' Commercial
diet of unknown
ME (MJ/kg)
and vitamins
Calculated
Minerals
composition.
11.5
2
18
Bone meal
---
HC1
---
980 ---
A
5
2
1
11.3
--
--
111 --
886 ---
C
1. D i e t
11.5
2
18
--
---
975 ---
B
Experiment
pig diets (g/kg)
L-Iso-leucine
L-Lysine
CP)
CP) CP)
Buckwheat Wheat (11.9% Wheat (17.2%
Meat meal (47.5% CP) Sunflower meal (38.2%
of experimental
I
Composition
TABLE
2
18 11.7
.
.
.
14.0
2
18
. --
-.
-. 134 1.3
-980
E
844.7 --
D
. .
-.
.
14.0
2
18
. 6.5
.
973.5
F
. .
. 5.6
11.5
2
18
.
974.4 .
G
.
2
.
.
12.0
2
18
--
100 100 --
.
780
J
2. D i e t
11.5
2
18
--
978 .
H
Experiment
13.2
--
--
--
----
--
K'
¢O
100
TABLE II Chemical composition and some biological measurements of buckwheat, oats and wheat on an air dry basis Buckwheat
Oats
Wheat
Protein (N × 6.25) (%) Ether extract (%) Neutral detergent fibre (%) Ash (%)
12.6 4.0 19.5 2.0
9.8 5.5 30.6 4.0
12.0 -11.7 --
Moisture (%)
12.4
10.1
--
Metabolizable energy: Chicks (MJ/kg) Hens (MJ/kg) Digestible energy: Pigs (MJ/kg)
11.0 10.9 11.5
8.9
Arginine (%) Iso-leucine (%) Leucine (%) Lysine (%) Methionine (%) Threonine (%) Valine (%) N retention: Chicks (%) N digestibility: Pigs (%) Dry matter digestibility: Pigs (%)
1.13 0.35 0.77 0.58 0.32 0.36 0.79 30.4 74.3 73.7
0.70 0.35 0.80 0.37 0.28 0.33 0.53 19.3
12.4
0.53 0.29 0.77 0.29 0.17 0.23 0.65 26.1
w e i g h t was used as a covariate. Differences b e t w e e n m e a n s were tested b y D u n c a n ' s multiple-range test. RESULTS Chemical c o m p o s i t i o n o f the b u c k w h e a t , oats and w h e a t used is given in Table II. T h e N D F was m u c h l o w e r f o r b u c k w h e a t t h a n f o r oats. C o n c e n t r a tions o f t h e m o r e i m p o r t a n t essential a m i n o acids indicated t h a t b u c k w h e a t was o f higher p r o t e i n q u a l i t y t h a n either w h e a t or oats. This was c o n f i r m e d b y t h e a p p a r e n t l y higher N r e t e n t i o n b y chickens fed o n b u c k w h e a t (Table
II). T h e ME o f t h e grains was related t o N D F and the value f o r b u c k w h e a t o f 11 M J / k g was the same f o r c h i c k e n s and for laying hens. T h e d r y m a t t e r digestibility o f 73.7% f o r b u c k w h e a t m a y be c o m p a r e d with values o f 82.5 t o 89.7 p r e v i o u s l y r e p o r t e d f o r w h e a t (Ivan et al., 1974).
Rat experiments Results o f E x p e r i m e n t s 1, 2 and 3 are given in Table III. In E x p e r i m e n t 1, g r o w t h rate o f rats o n b u c k w h e a t alone was superior t o t h a t o n w h e a t or oats,
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T A B L E III Mean w e i g h t gain and feed c o n v e r s i o n ratio o f groups o f 5 or 6 rats given diets based on b u c k w h e a t , oats or w h e a t w i t h and w i t h o u t various s u p p l e m e n t s Diet
Experiment 1 Buckwheat B u c k w h e a t and lysine B u c k w h e a t , lysine and m e t h i o n i n e B u c k w h e a t , lysine, m e t h i o n i n e and t h r e o n i n e B u c k w h e a t and s u n f l o w e r meal
Gain (g/lO d) ~
F o o d ( g)/ gain (g)
49.9 a 40.3 acd 49.0 a 51.0 a 46.0 a
3.3 ab 4.0 abd 3.2 bc 2.9 cb 3.0 cb
Wheat W h e a t and lysine Wheat, lysine and m e t h i o n i n e Wheat, lysine, m e t h i o n i n e and t h r e o n i n e Wheat and s u n f l o w e r meal
25.8 bf 38.2 cd 30.3 cbg 50.4 a 34.8 cbd
4.8 df 3.6 bc 3.4 bc 2.4 c 3.5 bc
Oats Oats and lysine Oats, lysine and m e t h i o n i n e Oats, lysine, m e t h i o n i n e and t h r e o n i n e Oats and s u n f l o w e r meal
14.2 e 14.3 e 17.0 ef 21.7 efg 23.8 fg
6.7de 5.7 ef 6.2 e 4.4 d 4.5 d
Control SE o f m e a n s
54.2 a -+2.48
2.6 c -+0.32
43.8 a
3.0 a
53.55
3.0 a
44.8 a
3.2 a
Experiment 2 Buckwheat B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e and leucine B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e and leucine B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e , iso-leucine and leucine SE o f m e a n s Experiment 3 Buckwheat B u c k w h e a t and lysine B u c k w h e a t , lysine and iso-leucine B u c k w h e a t , m e a t meal (7%) and s u n f l o w e r meal (7%) Wheat and fish meal (13%) SE o f m e a n s
53.5 b
2.9 a
-+2.34
-+0.12
51. I a 48.8 a 51.7 a
3.5 a 3.5 a 3.2 a
54.8 a 70.0 b
2.9 a 1.9 b
-+2.69
+_0.16
1Values w i t h the s a m e s u p e r s c r i p t s are n o t d i f f e r e n t (P> 0.05).
a n d was n o t significantly d i f f e r e n t f r o m rats o n t h e c o n t r o l d i e t ( w h e a t , fish m e a l a n d m e a t meal). A m i n o acid or s u n f l o w e r m e a l a d d i t i o n s t o b u c k w h e a t did n o t f u r t h e r i m p r o v e g r o w t h r a t e n o r f o o d c o n v e r s i o n r a t i o ( F C R ) as was o b s e r v e d o n t h e w h e a t , and t o a lesser e x t e n t o n t h e o a t - b a s e d diets.
102
In Experiment 2, it appears that iso-leucine was the first limiting amino acid, but this was not confirmed in Experiment 3, although in this experiment the control diet (wheat and fish meal) gave superior performance to all of the buckwheat-based diets. In the other two experiments (4 and 5) with rats, which are not reported in detail, 7.4% fat (tallow) added to buckwheat did not significantly improve growth rate, nor was it possible to conclusively identify a limiting amino acid. A combination of buckwheat, wheat (40%) and fish meal significantly (P<0.05), but not substantially, increased growth rate and FCR. In both experiments addition of NPN as 0.2% diammonium citrate to buckwheat gave a non-significant improvement in growth rate, and a significant (P<0.05) improvement in FCR. TABLE IV Weight gain and feed conversion ratio of groups of rats given diets based on sifted buckwheat o r o n w h e a t w i t h v a r i o u s s u p p l e m e n t s ( E x p e r i m e n t 6) Diet
Gain (g/10 d)'
Buckwheat Buckwheat and lysine Buckwheat and threonine Buckwheat, lysine, methionine and threonine B u c k w h e a t a n d 12% fish m e a l Wheat Wheat, lysine, methionine and threonine
45.0 46.8 47.6 43.7 51.4 30.4 58.1
SE o f m e a n s
_+3.58
a a a a ac b c
F o o d (g)/ gain (g) 3.0 a 3. i a 3.0 a 3.2 a 3.2 a 5.0 b 2.6 c +0.16
1Within a column, values with the same superscripts are not different (P> 0.05).
Compared with previous experiments, no noticeable improvement in growth rate was observed when sifted buckwheat was given to rats with or w i t h o u t supplementation (Experiment 6, Table IV). Growth rate and FCR were significantly (P~0.05) better than on the all-wheat diet, but addition of amino acids to wheat improved performance of rats to the extent that this was significantly better than on the buckwheat-based diets.
Chicken experiments The results of the two experiments (Table V) again show the superiority of buckwheat compared to mono-grain diets of wheat, oats or maize. There was much variation in the performance of chickens on the amino acidsupplemented diets, particularly when each of the amino acids in the mixture was withdrawn individually. In both experiments amino acid supplementation tended to improve performance, particularly with the addition of NPN in
103
Experiment 1, but it was impossible to identify the first limiting amino acid. Addition of 8% maize oil, or NPN w i t h o u t crystalline amino acids (Experim e n t 2), did not improve performance above that observed on the buckwheat diet. However, in both experiments the commercial grower diet (control) was superior to any other diet.
Pig experimen ts Initially, pigs took longrr to adjust to the buckwheat-based diets than to the others, and feed refusals were more frequent on the former diets. In the first experiment (Table VI) pigs grown only to 32 kg, because of a temporary shortage of buckwheat, grew as well on buckwheat (A) as on wheat (E). TABLE V W e i g h t gain o f g r o u p s o f c r o s s - b r e d m a l e c h i c k s ( E x p e r i m e n t 1) a n d m e a t - t y p e m a l e c h i c k s ( E x p e r i m e n t 2) g r o w n o n diets o f b u c k w h e a t , w h e a t , o a t s o r m a i z e Diet
Gain ( g / 1 0 d) 2
Experiment 1 Buckwheat Wheat Oats Maize Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat,
34.4 11.8 15.2 22.9 a n d 8% c o r n oil a n d a m i n o acids 1 a n d a m i n o acids - - l y s i n e a n d a m i n o acids - - m e t h i o n i n e a n d a m i n o acids - - t h r e o n i n e a n d a m i n o acids - - l e u c i n e a n d a m i n o acids - - i s o - l e u c i n e a n d a m i n o acids - - valine a m i n o acids a n d N P N
C o m m e r c i a l diet SE o f m e a n s Experiment 2 Buckwheat Buckwheat, Buckwheat Buckwheat Buckwheat
fish m e a l a n d m e a t m e a l and NPN a n d a m i n o acid m i x t u r e ~ and iso-leucine
C o m m e r c i a l diet SE of m e a n s
a c c d
32.3 a 36.4 a 38.2 a 37.4 a 48.35 46.0 b 47.0 b 4 3 . 0 ab 49.05
F o o d (g)/ gain (g)
5.3 a 9.0 c 8.6 c 6.2 c 6.0 c 4.9 a 4.9 a 5.0 a 4.0 b 4.1 b 4.4 ab 4.8 ab 3.9 b
98.2 d +-2.47
1.9 d +-0.42
20.5 a 47.6 b 22.1 a 37.4 b 20.7 a
5.0 a 3.3 b 5.4 a 5.0 a 5.4 a
60.8 c -+1.65
2.4 c -+0.23
I L y s i n e , m e t h i o n i n e , t h r e o n i n e , l e u c i n e , i s o - l e u c i n e a n d valine. 2Values w i t h t h e s a m e s u p e r s c r i p t ~within e a c h c o l u m n are n o t s i g n i f i c a n t l y d i f f e r e n t (P>0.05).
104
TABLE VI Performance of groups of five castrated male pigs grown to 32 kg in Experiment 1, and of five entire males grown to 40 kg in Experiment 2, on diets based on buckwheat and wheat Diet Experiment 1 Buckwheat Buckwheat and lysine Buckwheat and meat meal Buckwheat and sunflower meal Wheat Wheat and lysine SE of means Experiment 2 Buckwheat and lysine Buckwheat and iso-leucine Buckwheat, meat meal and sunflower meal Commercial diet SE of means
Gain (g/day) 1
Food (g)/gain (g)
(A) (B) (C) (D) (E) (F)
241 a 289 a 434 b 290 ac 269 a 325 c + 17.9
5.2 a 4.3 b 2.9 c 4.3 b 3.9 b 3.3 bc +-0.20
(G) (H)
410 a 371 b
3.7 a
(J) (K)
433 ac 448 c -+17.4
2.7 b +-0.14
3.4 a
3.1 b
IValues with the same superscript within each row are not significantly different (P>O.05). S u p p l e m e n t a t i o n o f b u c k w h e a t w i t h lysine (B) i m p r o v e d g r o w t h r a t e slightly, and F C R significantly ( P < 0 . 0 5 ) . A d d i t i o n o f m e a t m e a l + lysine (C), b u t n o t s u n f l o w e r m e a l + lysine (D), significantly { P < 0 . 0 5 ) i m p r o v e d b o t h g r o w t h rate a n d F C R o v e r all diets, including t h e high p r o t e i n w h e a t (17% CP) + lysine (F). In t h e s e c o n d e x p e r i m e n t (Table V I ) a d d i t i o n o f lysine t o b u c k w h e a t (F) gave a significant ( P < 0 . 0 5 ) i m p r o v e m e n t in g r o w t h r a t e b u t n o t F C R , c o m p a r e d w i t h b u c k w h e a t + iso-leucine (H). A c o m b i n a t i o n o f m e a t m e a l a n d sunf l o w e r m e a l (J) r e s u l t e d in t h e s a m e p e r f o r m a n c e as t h a t o f t h e c o m m e r c i a l ( c o n t r o l ) d i e t (K).
Disappearance o f amino acids D i f f i c u l t y was e n c o u n t e r e d w i t h m e a s u r e m e n t s o n pigs receiving u n s i f t e d buckwheat owing to frequent blockage of the re-entrant cannulae; only two c o m p l e t e c o l l e c t i o n s w e r e m a d e (Table VII). R e m o v a l o f t h e hull, w h i c h c o m prised a b o u t 20% o f t h e t o t a l grain, f r o m t h e f l o u r resulted in s a t i s f a c t o r y collections. Statistical analysis was .restricted t o d a t a f o r a m i n o acid d i s a p p e a r ance w i t h sifted b u c k w h e a t . T h e r e was a significant d i f f e r e n c e ( P ~ 0 . 0 1 ) b e t w e e n a m i n o acids ( T a b l e V I I ) a n d b e t w e e n pigs, in t h a t Pig 3 gave generally l o w e r values t h a n did t h e t w o others. B o t h leucine a n d iso-leucine gave values l o w e r t h a n t h e m e a n o f o t h e r a m i n o acids e x a m i n e d ; d i s a p p e a r a n c e o f m e t h i o n i n e was higher ( P ~ 0 . 0 5 ) t h a n f o r t h e m e a n o f o t h e r a m i n o acids.
105
Laying trial Buckwheat, with or w i t h o u t synthetic lysine and methionine added, resulted in a significant reduction in egg numbers, egg size, and production per hen-day housed compared with the commercial layer diet (Table VIII). There was no significant difference in food intake of hens on the three diets but birds given either buckwheat diet lost significantly more weight than those given the commercial diet (Table VIII). Productivity decreased over time, but there was a diet x time interaction, indicating that the decrease was more rapid on the two buckwheat diets (1 and 2). Addition of the two synthetic amino acids to Diet 1 gave a consistent, but non-significant improvement in performance (Diet 1 vs. Diet 2).
T A B L E VII D i s a p p e a r a n c e (%) o f s o m e a m i n o acids d e t e r m i n e d b y d i f f e r e n c e b e t w e e n t h o s e in feed and in c o r r e s p o n d i n g digesta c o l l e c t e d f r o m r e - e n t r a n t cannulas at t h e terminal ileum o f 3 pigs Pig no.
A m i n o acid Iso-leucine
Leucine
Lysine
Methionine
Valine
Threonine
1" 2*
73 64
78 70
83 70
92 88
85 78
80 79
1 1 2 2 3 3
70 64 78 70 61 44
70 68 76 75 68 49
79 80 85 83 80 69
93 90 92 91 88 82
80 79 85 82 79 68
78 76 76 82 80 63
* U n s i f t e d b u c k w h e a t , r e m a i n d e r received sifted. T A B L E VIII Results o f t h e laying trial over 70 days w i t h 24 birds per dietary t r e a t m e n t Buckwheat I
Eggs ( p e r h e n p e r w e e k ) Egg w e i g h t (g) P r o d u c t i o n (%) F o o d intake (g/d) Loss in w e i g h t (g]70 d)
Commercial
Diet no. (1)
Buckwheat, lysine and methionine Diet no. (2)
3.1 a 54.6 a 45.4 a 111 a 330 a
3.5 a 56.4 ab 50.8 a 120 a 414 a
4.6 b 58.4 b 72.3 b 119 a 159 b
SE of means
Diet no. (3)
~Values w i t h i n a r o w w i t h the s a m e s u p e r s c r i p t are n o t d i f f e r e n t ( P > 0 . 0 5 ) .
-+0.29 +-0.80 -+4.59 + 5.4 +_32.4
106
DISCUSSION The results of this study with various domestic species showed that buckwheat was superior to other grains tested when no protein supplement was provided (Tables III--VI). With pigs, unsupplemented buckwheat gave similar results to unsupplemented wheat in the first experiment (Diets A vs. E), and when L-lysine was added to buckwheat, there were responses in food conversion (Experiment 1, Diet B) and growth rate (Experiment 2, Diet G) which did not occur in the rat experiments. Pigs performed significantly better on a diet with high protein wJ~eat with added lysine (Diet F) than on buckwheat even though dietary lysine concentrations were similar. However, the response of pigs to added lysine was not as great as that found by Ivan et al. (1975a,b) although the response of rats was similar to that of Ivan and Farrell (1975). Addition of only 11% meat meal (Diet C) and 10% meat meal and 10% sunflower (Diet J) to buckwheat substantially improved performance, and growth rate and feed conversion on the latter diet was no different (P~0.05) from that observed on the commercial (control) diet (Diet K). Food conversion would be expected to be better on the latter diet because of the higher calculated digestible energy concentration. These findings with growing pigs are in general agreement with those of van Wyk et al. (1952) who showed that growth on a buckwheat diet supplemented with 9% fish, 3% groundnut and 2% lucerne meal was similar to that on diets containing all, or large amounts of, other grain. Nevertheless, van Wyk et al. (1952) concluded that buckwheat should replace only part of the grain in a ration. It was not possible to identify clearly either the first or subsequent limiting amino acids in the chick or in the rat growth studies. Although iso-leucine in Experiment 2 (Table III) appeared to give significant growth response in rats, this was not repeated in Experiment 3, nor in the pig experiment {Diet H, Table VI). This may be explained in part by the low availability of some amino acids as measured with pigs (Table VII), particularly leucine and iso-leucine. Addition of some crystalline amino acids to rat diets may have been inadequate to allow maximum growth rate. Even when buckwheat was supplemented with fish and meat meals, the response in growth rate was much less than that observed on the commercial diet. Amino acid mixtures in Experiment 2 gave a growth response, but it was n o t possible to identify specific limiting amino acids in Experiment 1 (Table V). Because of the high NDF c o m p o n e n t (Table II), it might have been expected that energy concentration would have been the limiting factor. This was apparently n o t so, since addition of maize oil to chick diets, and animal fat (tallow) to rat diets, did not improve performance. Thus rat and chick studies on buckwheat did not provide here a useful guide to responses found subsequently in pig experiments, as was observed previously for the evaluation of wheat by Ivan and Farrell (1975) and Ivan et al. (1975a, b). In the laying trials, buckwheat apparently did not provide sufficient nutrients to allow maximum egg production even when DL-methionine and
107
I~lysine were added. By calculation, the diet was adequate in these amino acids for egg production but was only just within the minimum value for dietary energy concentration suggested by the Agricultural Research Council (1975). Because of the substantial loss in weight together with the low egg o u t p u t of birds on Diets 1 and 3 (Table VI), it must be concluded that for some reason hens did not consume sufficient amounts of the diet. Morrison (1957) stated that buckwheat was less palatable than cereal grains. This suggests t h a t buckwheat may contain a toxin, or other chemical compound, affecting acceptability. Such a c o m p o u n d would, in part, explain the disappointing performance observed on m a n y of the buckwheat-based diets for rats and chickens. Because pigs were offered restricted amounts of feed, an acceptability problem would be of less significance than for rats and chickens fed ad libitum. Had hens eaten more food, weight loss would have been reduced during the 101week experimental period but it does not follow that productivity would have been increased substantially. Again, availability of many of the essential amino acids in buckwheat is probably lower than that for most other feed grains (Taverner et al., 1978). Our results do not support the assessment of buckwheat protein of Sure (1955), who stated t h a t " b u c k w h e a t flour, without any amino acid additions approximates the nutritive efficiency of proteins of animal origin of high biological value". Although we found that buckwheat without amino acid addition was superior to cereal grains, no significant improvement in growth rate could be elicited as a result of dietary supplementation for rats and chicks. Supplementation with protein sources usually improved performance but not to t h a t promoted by the control diets. Buckwheat in the diets of pigs gave more positive results when supplemented with lysine or protein sources, even to the extent of equalling growth rate of pigs fed on the commercial diet (Table VI, Diets J and K). It was clear in these two experiments that there was large variation between individual pigs in their growth performance on all of the buckwheat-based diets. Buckwheat has a high fibre content owing to the large a m o u n t of hull, and differences in capacity to digest fibre among individual animals may be of importance, particularly in relation to amino acid absorption. The favourable chemical composition of buckwheat, particularly its relatively high concentration of essential amino acids, was n o t confirmed by the biological performance that it supported. ACKNOWLEDGEMENTS I wish to thank Mrs. Barbara Ward and Mr. Evan Thomson for technical assistance. The University of New England provided financial support for this project. I am grateful to Dr. R.G. Packham of Hawkesbury Agricultural College, who carried out the experiment with laying hens.
108
REFERENCES Agricultural Research Council, 1975. The Nutrient Requirements of Farm Livestock No. 1, Poultry. Agricultural Research Council, London. Association of Official Agricultural Chemists, 1970. Official Methods of Analysis, l l t h Edn. Association of Official Agricultural Chemists, Washington. Farrell, D.J., 1976. The nutritive value of buckwheat Fagopyrurn esculentum. Proc. Aust. Soc. Anim. Prod., 11: 413--416. Holmes, J.H.G., Bayley, H.S. and Homey, F.D., 1973a. Digestion and absorption of dry and high moisture maize diets in the small and large intestine of the pig. Br. J. Nutr., 30: 401--410. Holmes, J.H.G., Horney, F.D. and Leadbeater, P.A., 1973b. Re-entrant cannulation of duodenum cranial to pancreatic duct in the pig. Am. J. Vet. Res., 34: 1365--1366. Ivan, M. and Farrell, D.J., 19'75. Nutritional evaluation of wheat. 2. The sequence of limiting amino acids in wheats of different protein content as determined with growing rats. Anim. Prod., 20: 77--91. Ivan, M. and Farrell, D.J., 1976. Nutritional evaluation of wheat. 5. Disappearance of components in digesta of pigs prepared with re-entrant cannulae. Anim. Prod., 23: 111--119. Ivan, M., Giles, L.R., Alimon, A.R. and Farrell, D.J., 1974. Nutritional evaluation of wheat. 1. Effects of preparation on digestibility, metabolizable energy and nitrogen retention in pigs. Anim. Prod., 90: 359--365. Ivan, M., Farrell, D.J. and Edey, T.N., 1975a. Nutritional evaluation of wheat. 3. Effects of supplementation with lysine, threonine and methionine of diets based on wheat containing 13% crude protein on the performance of pigs. Anita. Prod., 20: 267--276. Ivan, M., Farrell, D.J. and Edey, T.N., 1975b. Nutritional evaluation of wheat. 4. Effects of supplementation with amino acids and protein of diets based on wheats containing 10% and 17% crude protein on the performance of growing pigs. Anita. Prod., 20: 277--285. Morrison, F.B., 1957. Feeds and Feeding, 22rid Edn. Morrison, Ithaca, New York. Pomeranz, G. and Robbins, G.S., 1972. Amino acid composition of buckwheat. J. Agric. Food Chem., 20: 270--274. Spackman, D.H., Stein, W.H. and Moore, S., 1958. Automatic recording apparatus for use in the chromatography of amino acids. Anal. Chem., 30: 1190--1206. Sure, B., 1955. Nutritive value of proteins in buckwheat and their role as supplements to protein cereal grains. J. Agric. Food Chem., 9: 793--795. Taverner, M.R., Hume, I.D. and Farrell, D.J., 1978. A study with pigs of amino acid availability in grain. Proc. Second Australasian Poultry and Stock Feed Convention, Sydney, March 1978, pp. 154--157. Van Soest, P.J. and Wine, R.H., 1967. Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell-wail constituents. J. Assoc. Off. Agric. Chem., 50: 50--55. Van Wyk, H.P.D., Verbeck, W.A. and Osthuizin, S.A., 1952. Buckwheat in rations for growing pigs, Farming S. Afr., 27 : 399--402.
95
© Elsevier Scientific P u b l i s h i n g C o m p a n y , A m s t e r d a m - - P r i n t e d in T h e N e t h e r l a n d s
A N U T R I T I O N A L E V A L U A T I O N O F B U C K W H E A T (FAGOPYR UM
ESC ULENTUM) D.J. F A R R E L L
Department o f Biochemistry and Nutrition, University o f New England, Armidale, N.S. W. 2351 (Australia) ( R e c e i v e d 18 N o v e m b e r 1 9 7 7 )
ABSTRACT Farrell, D.J., 1978. A n u t r i t i o n a l e v a l u a t i o n of b u c k w h e a t (Fagopyrum esculentum). Anita. Feed Sci. Technol., 3: 9 5 - - 1 0 8 . E x p e r i m e n t s were c o n d u c t e d w i t h rats, pigs, c h i c k e n s a n d laying hens. B u c k w h e a t h a d a high n e u t r a l d e t e r g e n t fibre c o n t e n t o f 20%; digestible energy m e a s u r e d w i t h pigs was 11.5 MJ/kg, a n d a m e a n m e t a b o l i z a b l e e n e r g y value o f 11.0 M J ] k g w i t h p o u l t r y . G r o w t h studies w i t h rats a n d chicks s h o w e d t h a t b u c k w h e a t in m o n o - g r a i n diets was s u p e r i o r t o cereal grains. However, it was n o t possible t o i d e n t i f y l i m i t i n g a m i n o acids in b u c k w h e a t , a n d s u p p l e m e n t a t i o n w i t h fat a n d p r o t e i n sources did n o t p r o m o t e t h e g r o w t h responses a n t i c i p a t e d . R e m o v a l o f t h e fibrous hulls f r o m b u c k w h e a t b y sifting did n o t increase g r o w t h rate, b u t f o o d c o n v e r s i o n was i m p r o v e d . A l t h o u g h c h e m i c a l analysis i n d i c a t e d t h a t a m i n o acids were a d e q u a t e t o m a i n t a i n egg p r o d u c t i o n , this was n o t c o n f i r m e d in laying trials even w h e n a d d i t i o n s o f lysine a n d m e t h i o n i n e were m a d e t o b u c k w h e a t . T h e m o s t favourable r e s p o n s e to b u c k w h e a t was achieved in pig-growth studies. G r o w t h rate o n a n a l l - b u c k w h e a t d i e t was n o t d i f f e r e n t f r o m t h a t o n a n all-wheat (12% CP) diet b u t a d d i t i o n of lysine i m p r o v e d g r o w t h r a t e a n d feed conversion. A d d i t i o n o f 10% m e a t meal or s u n f l o w e r meal to b u c k w h e a t gave similar g r o w t h a n d feed c o n v e r s i o n to t h o s e o f a c o m m e r c i a l grower diet. A m i n o acid disappearance, m e a s u r e d at t h e t e r m i n a l i l e u m o f pigs p r e p a r e d w i t h r e - e n t r a n t cannulas, gave values ranging f r o m 90% for m e t h i o n i n e to 65% for leucine, a l t h o u g h t h e r e was s u b s t a n t i a l variat i o n a m o n g pigs. It was a p p a r e n t t h a t b u c k w h e a t as t h e sole grain s o u r c e was n o t s u i t a b l e for the species e x a m i n e d . D i f f e r e n c e s in p e r f o r m a n c e b e t w e e n individual animals m a y be a t t r i b u t e d t o t h e i r c a p a c i t y to degrade t h e b u c k w h e a t fibre. T h i s m a y in p a r t e x p l a i n the v a r i a t i o n in the r e s p o n s e o f individuals t o t h e e x p e r i m e n t a l diets a n d t h e r e f o r e a t e n d e n c y to m a s k responses t o t h e various s u p p l e m e n t s . I t can be c o n c l u d e d f r o m this s t u d y t h a t b u c k w h e a t as t h e sole s o u r c e of energy is u n s u i t a b l e for pigs a n d p o u l t r y even t h o u g h in t h e diets of pigs it gave a c c e p t a b l e g r o w t h rate a n d feed conversion. S o m e pigs, h o w e v e r , did n o t take readily t o this grain a n d o f t e n t o o k several h o u r s to c o n s u m e t h e i r rations. P o o r a c c e p t a b i l i t y , p e r h a p s d u e t o the p r e s e n c e o f a t o x i n or o t h e r c h e m i c a l c o m p o u n d s , a p p e a r s t o be associated w i t h this grain.
INTRODUCTION
B u c k w h e a t (Fagopyrum esculentum) is a s u m m e r annual, w i d e l y g r o w n
96
throughout the world. The majority of the grain produced in Australia is milled and used in the diets of man. Although buckwheat is n o t a cereal (Gramineae) it does have a number of chemical characteristics in c o m m o n with cereal grains, particularly in relation to its protein concentration, starchy endosperm and oily embryo. The amino acid profile (Pomeranz and Robbins, 1972) suggests that the protein may be of high biological value. Agronomically, buckwheat has some attractive features. It will grow from planting to harvesting in 10--12 weeks, making its best growth in cool areas, and will often yield a better crop on poor soil than the cereal grains. The object of this study was to investigate the chemical composition and nutritive value of Australian-grown buckwheat for various species of domestic animals. A preliminary report on some of this work was published by Farrell (1976). MATERIALS AND METHODS All experiments were carried out on milled buckwheat (cultivar ' T o k y o ' ) taken from the same batch. Chemical composition of diets and excreta was determined by standard procedures (Association of Official Agricultural Chemists, 1970), and the method of Van Soest and Wine {1967) for neutral detergent fibre (NDF); individual amino acids were determined on the acid hydrolysates (Spackman et al., 1958) using a T.S.M.-1 Technicon Analyser. Faeces and excreta were dried to constant weight in a forced-draught oven at 105°C.
Digestibility and metabolizability Apparent digestibility of dry matter, nitrogen (N) and energy of buckwheat was determined by total collection of faeces for 4 days from each of four pigs (20 kg) accustomed to receiving 1 kg of buckwheat daily, and housed in metabolism crates. Metabolizability of the diet, w i t h o u t correction to N equilibrium, was determined by total collection of excreta for 5 days from two groups of 5 chickens aged 3 weeks offered diets of buckwheat ad libitum. Similar determinations were also made on groups of chickens offered all-wheat, or all-oat diets. Metabolizability of buckwheat was also determined with each of four laying, cross-bred hens in individual cages. Excreta were collected for 5 days. Bone meal, limestone and a commercial mineral and vitamin premix were added to the mono-grain diets in recommended amounts. At least 3 days were allowed for animals to become accustomed to the experimental conditions.
Rat growth study There were six experiments. Weanling rats of the Wistar strain were housed individually in wire-mesh cages in a temperature-controlled room (22 + 2°C).
97
There were 5 or 6 animals on each dietary treatment, and food and water were always available. Rats and their f ood containers were weighed initially and at intervals o f 5 days. Experiments continued for 10 or 12 days, b u t all data were corrected to a 10-day period. Most o f the diets were based on b u c k w h e a t supplemented with individual, and various combinations of, crystalline amino acids, with di-ammonium citrate as a non-protein nitrogen (NPN) source, with protein concentrates, and with o th er grains and fat. Bone meal, sodium chloride, and a mineral and vitamin supplement (Ivan and Farrell, 1975) were added to all diets. In E x p e r i m e n t 6, de-hulled (sifted) b u c k w h e a t with amino acid additions was compared with wheat with amino acid additions.
Chick growth study There were two experiments. In the first, 28 groups of ten cross-bred cockerels, aged 7 days, were selected for u n i f o r m i t y of weight and each group was placed separately in a c o m p a r t m e n t in electrically heated b a t t e r y brooders with wire-mesh floors and offered one of 14 diets. Most of the diets were buckwheat-based, and several were supplemented with crystalline amino acids which appeared to be limiting on the basis o f chemical analysis. Diets based solely on wheat, oats and maize were also included. Bone meal and a mineral and vitamin supplement were added to all diets. After 10 days the groups of chickens and their food containers were again weighed. In the second e x p e r i m e n t 18 groups of eight 3-day-old cockerels of a commercial broiler strain were placed in small cages in a ventilated, heated r o o m initially at 33°C and offered one of six diets based on buckw heat supplemented with protein sources, essential amino acids, or di-ammonium citrate as a NPN source. After 10 days the groups of chickens and their f o o d containers were again weighed. A commercially available grower diet was included as a control in the experiments. Water was freely available, and illumination was for 24 h.
Laying trial Seventy-two White Leghorn hens in their first year of lay and in p r o d u c t i o n for a b o u t six m o n t h s were r a n d o m l y allocated in pairs to single-deck wire cages in a conventional layer shed. All cages were equipped with trough feeders and drinkers. After a preliminary period of one week when hens became accustomed to the experimental conditions, measurements c o m m e n c e d and co n tin u ed for 70 days. Egg p r o d u c t i o n and f o o d intake were recorded each week, and hens were weighed at the start and finish of the experiment. There were two experimental diets (Diets 1 and 2) and a commercial layer's diet which was used as a control. Both experimental diets contained b u c k w h e a t as the sole protein and energy sources. All diets were supplemented with 0.2 NaC1, and limestone and bone meal in amounts sufficient to m eet the
98
calcium and phosphorus allowances of the laying hen (Agricultural Research Council, 1975). A commercially-available mineral and vitamin supplement was included. In addition, Diet 2 contained 0.25% L-lysine HC1, and 0.07% DL-methionine but was otherwise the same as Diet 1. Determined ME of the latter diets was 9.5 MJ/kg.
Pig growth study There were two experiments. In Experiment 1, thirty Large White X Landrace castrate male pigs (15 kg) were placed in individual pens in a temperaturecontrolled piggery. Following a period of adjustment on a commercial grower diet, five pigs (18 kg) were allocated to each of six diets shown in Table I. They were offered restricted amounts of food calculated from liveweight (W, kg) by the formula (Ivan and Farrell, 1975) Digestible energy intake (MJ/day) = 1.36 W°.75 Digestible energy of the diets was computed from values for each ingredient and determined for the commercial diet at this laboratory (Ivan et al., 1975a, b). Pigs were weighed each week, and food allocation was adjusted accordingly for the following week. In Experiment 2, twenty Large White X Landrace entire male pigs were used; experimental conditions were similar to those described. Five pigs were offered each of four diets shown in Table I. A commercial grower diet was used as the control. In both experiments it was planned to grow pigs to 44 kg.
Disappearance of amino acids at the terminal ileum Measurement of disappearance of some dietary amino acids at the terminal ileum was made on three pigs (100--110 kg) fitted with re-entrant cannulas (Holmes et al., 1973a, b). The procedures followed were essentially those described by Ivan and Farrell (1976). The pigs were fed, at 12 h intervals, one kg of a diet containing 0.5 kg of whole buckwheat or sifted buckwheat, and 0.5 kg of a synthetic diet. This contained (g/kg) 698 corn starch, 214 sucrose, 54 maize oil, 27 bone meal, 6 salt, and a mineral and vitamin supplement. Total collection of digesta was made on eight occasions for 12 h from the ileal cannula and commencing immediately after the morning feeding. A 10% portion of the weighed digesta was retained and freeze-dried for amino acid analysis; the remainder was returned through the cannula at frequent intervals. Disappearance of amino acids was calculated by comparing dietary amounts with those in the total digesta collected, and expressing the values as "percentage disappearance".
Statistical methods Analyses of variance and covariance were used. For growth studies, initial
' Commercial
diet of unknown
ME (MJ/kg)
and vitamins
Calculated
Minerals
composition.
11.5
2
18
Bone meal
---
HC1
---
980 ---
A
5
2
1
11.3
--
--
111 --
886 ---
C
1. D i e t
11.5
2
18
--
---
975 ---
B
Experiment
pig diets (g/kg)
L-Iso-leucine
L-Lysine
CP)
CP) CP)
Buckwheat Wheat (11.9% Wheat (17.2%
Meat meal (47.5% CP) Sunflower meal (38.2%
of experimental
I
Composition
TABLE
2
18 11.7
.
.
.
14.0
2
18
. --
-.
-. 134 1.3
-980
E
844.7 --
D
. .
-.
.
14.0
2
18
. 6.5
.
973.5
F
. .
. 5.6
11.5
2
18
.
974.4 .
G
.
2
.
.
12.0
2
18
--
100 100 --
.
780
J
2. D i e t
11.5
2
18
--
978 .
H
Experiment
13.2
--
--
--
----
--
K'
¢O
100
TABLE II Chemical composition and some biological measurements of buckwheat, oats and wheat on an air dry basis Buckwheat
Oats
Wheat
Protein (N × 6.25) (%) Ether extract (%) Neutral detergent fibre (%) Ash (%)
12.6 4.0 19.5 2.0
9.8 5.5 30.6 4.0
12.0 -11.7 --
Moisture (%)
12.4
10.1
--
Metabolizable energy: Chicks (MJ/kg) Hens (MJ/kg) Digestible energy: Pigs (MJ/kg)
11.0 10.9 11.5
8.9
Arginine (%) Iso-leucine (%) Leucine (%) Lysine (%) Methionine (%) Threonine (%) Valine (%) N retention: Chicks (%) N digestibility: Pigs (%) Dry matter digestibility: Pigs (%)
1.13 0.35 0.77 0.58 0.32 0.36 0.79 30.4 74.3 73.7
0.70 0.35 0.80 0.37 0.28 0.33 0.53 19.3
12.4
0.53 0.29 0.77 0.29 0.17 0.23 0.65 26.1
w e i g h t was used as a covariate. Differences b e t w e e n m e a n s were tested b y D u n c a n ' s multiple-range test. RESULTS Chemical c o m p o s i t i o n o f the b u c k w h e a t , oats and w h e a t used is given in Table II. T h e N D F was m u c h l o w e r f o r b u c k w h e a t t h a n f o r oats. C o n c e n t r a tions o f t h e m o r e i m p o r t a n t essential a m i n o acids indicated t h a t b u c k w h e a t was o f higher p r o t e i n q u a l i t y t h a n either w h e a t or oats. This was c o n f i r m e d b y t h e a p p a r e n t l y higher N r e t e n t i o n b y chickens fed o n b u c k w h e a t (Table
II). T h e ME o f t h e grains was related t o N D F and the value f o r b u c k w h e a t o f 11 M J / k g was the same f o r c h i c k e n s and for laying hens. T h e d r y m a t t e r digestibility o f 73.7% f o r b u c k w h e a t m a y be c o m p a r e d with values o f 82.5 t o 89.7 p r e v i o u s l y r e p o r t e d f o r w h e a t (Ivan et al., 1974).
Rat experiments Results o f E x p e r i m e n t s 1, 2 and 3 are given in Table III. In E x p e r i m e n t 1, g r o w t h rate o f rats o n b u c k w h e a t alone was superior t o t h a t o n w h e a t or oats,
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T A B L E III Mean w e i g h t gain and feed c o n v e r s i o n ratio o f groups o f 5 or 6 rats given diets based on b u c k w h e a t , oats or w h e a t w i t h and w i t h o u t various s u p p l e m e n t s Diet
Experiment 1 Buckwheat B u c k w h e a t and lysine B u c k w h e a t , lysine and m e t h i o n i n e B u c k w h e a t , lysine, m e t h i o n i n e and t h r e o n i n e B u c k w h e a t and s u n f l o w e r meal
Gain (g/lO d) ~
F o o d ( g)/ gain (g)
49.9 a 40.3 acd 49.0 a 51.0 a 46.0 a
3.3 ab 4.0 abd 3.2 bc 2.9 cb 3.0 cb
Wheat W h e a t and lysine Wheat, lysine and m e t h i o n i n e Wheat, lysine, m e t h i o n i n e and t h r e o n i n e Wheat and s u n f l o w e r meal
25.8 bf 38.2 cd 30.3 cbg 50.4 a 34.8 cbd
4.8 df 3.6 bc 3.4 bc 2.4 c 3.5 bc
Oats Oats and lysine Oats, lysine and m e t h i o n i n e Oats, lysine, m e t h i o n i n e and t h r e o n i n e Oats and s u n f l o w e r meal
14.2 e 14.3 e 17.0 ef 21.7 efg 23.8 fg
6.7de 5.7 ef 6.2 e 4.4 d 4.5 d
Control SE o f m e a n s
54.2 a -+2.48
2.6 c -+0.32
43.8 a
3.0 a
53.55
3.0 a
44.8 a
3.2 a
Experiment 2 Buckwheat B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e and leucine B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e and leucine B u c k w h e a t , lysine, m e t h i o n i n e , t h r e o n i n e , iso-leucine and leucine SE o f m e a n s Experiment 3 Buckwheat B u c k w h e a t and lysine B u c k w h e a t , lysine and iso-leucine B u c k w h e a t , m e a t meal (7%) and s u n f l o w e r meal (7%) Wheat and fish meal (13%) SE o f m e a n s
53.5 b
2.9 a
-+2.34
-+0.12
51. I a 48.8 a 51.7 a
3.5 a 3.5 a 3.2 a
54.8 a 70.0 b
2.9 a 1.9 b
-+2.69
+_0.16
1Values w i t h the s a m e s u p e r s c r i p t s are n o t d i f f e r e n t (P> 0.05).
a n d was n o t significantly d i f f e r e n t f r o m rats o n t h e c o n t r o l d i e t ( w h e a t , fish m e a l a n d m e a t meal). A m i n o acid or s u n f l o w e r m e a l a d d i t i o n s t o b u c k w h e a t did n o t f u r t h e r i m p r o v e g r o w t h r a t e n o r f o o d c o n v e r s i o n r a t i o ( F C R ) as was o b s e r v e d o n t h e w h e a t , and t o a lesser e x t e n t o n t h e o a t - b a s e d diets.
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In Experiment 2, it appears that iso-leucine was the first limiting amino acid, but this was not confirmed in Experiment 3, although in this experiment the control diet (wheat and fish meal) gave superior performance to all of the buckwheat-based diets. In the other two experiments (4 and 5) with rats, which are not reported in detail, 7.4% fat (tallow) added to buckwheat did not significantly improve growth rate, nor was it possible to conclusively identify a limiting amino acid. A combination of buckwheat, wheat (40%) and fish meal significantly (P<0.05), but not substantially, increased growth rate and FCR. In both experiments addition of NPN as 0.2% diammonium citrate to buckwheat gave a non-significant improvement in growth rate, and a significant (P<0.05) improvement in FCR. TABLE IV Weight gain and feed conversion ratio of groups of rats given diets based on sifted buckwheat o r o n w h e a t w i t h v a r i o u s s u p p l e m e n t s ( E x p e r i m e n t 6) Diet
Gain (g/10 d)'
Buckwheat Buckwheat and lysine Buckwheat and threonine Buckwheat, lysine, methionine and threonine B u c k w h e a t a n d 12% fish m e a l Wheat Wheat, lysine, methionine and threonine
45.0 46.8 47.6 43.7 51.4 30.4 58.1
SE o f m e a n s
_+3.58
a a a a ac b c
F o o d (g)/ gain (g) 3.0 a 3. i a 3.0 a 3.2 a 3.2 a 5.0 b 2.6 c +0.16
1Within a column, values with the same superscripts are not different (P> 0.05).
Compared with previous experiments, no noticeable improvement in growth rate was observed when sifted buckwheat was given to rats with or w i t h o u t supplementation (Experiment 6, Table IV). Growth rate and FCR were significantly (P~0.05) better than on the all-wheat diet, but addition of amino acids to wheat improved performance of rats to the extent that this was significantly better than on the buckwheat-based diets.
Chicken experiments The results of the two experiments (Table V) again show the superiority of buckwheat compared to mono-grain diets of wheat, oats or maize. There was much variation in the performance of chickens on the amino acidsupplemented diets, particularly when each of the amino acids in the mixture was withdrawn individually. In both experiments amino acid supplementation tended to improve performance, particularly with the addition of NPN in
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Experiment 1, but it was impossible to identify the first limiting amino acid. Addition of 8% maize oil, or NPN w i t h o u t crystalline amino acids (Experim e n t 2), did not improve performance above that observed on the buckwheat diet. However, in both experiments the commercial grower diet (control) was superior to any other diet.
Pig experimen ts Initially, pigs took longrr to adjust to the buckwheat-based diets than to the others, and feed refusals were more frequent on the former diets. In the first experiment (Table VI) pigs grown only to 32 kg, because of a temporary shortage of buckwheat, grew as well on buckwheat (A) as on wheat (E). TABLE V W e i g h t gain o f g r o u p s o f c r o s s - b r e d m a l e c h i c k s ( E x p e r i m e n t 1) a n d m e a t - t y p e m a l e c h i c k s ( E x p e r i m e n t 2) g r o w n o n diets o f b u c k w h e a t , w h e a t , o a t s o r m a i z e Diet
Gain ( g / 1 0 d) 2
Experiment 1 Buckwheat Wheat Oats Maize Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat Buckwheat,
34.4 11.8 15.2 22.9 a n d 8% c o r n oil a n d a m i n o acids 1 a n d a m i n o acids - - l y s i n e a n d a m i n o acids - - m e t h i o n i n e a n d a m i n o acids - - t h r e o n i n e a n d a m i n o acids - - l e u c i n e a n d a m i n o acids - - i s o - l e u c i n e a n d a m i n o acids - - valine a m i n o acids a n d N P N
C o m m e r c i a l diet SE o f m e a n s Experiment 2 Buckwheat Buckwheat, Buckwheat Buckwheat Buckwheat
fish m e a l a n d m e a t m e a l and NPN a n d a m i n o acid m i x t u r e ~ and iso-leucine
C o m m e r c i a l diet SE of m e a n s
a c c d
32.3 a 36.4 a 38.2 a 37.4 a 48.35 46.0 b 47.0 b 4 3 . 0 ab 49.05
F o o d (g)/ gain (g)
5.3 a 9.0 c 8.6 c 6.2 c 6.0 c 4.9 a 4.9 a 5.0 a 4.0 b 4.1 b 4.4 ab 4.8 ab 3.9 b
98.2 d +-2.47
1.9 d +-0.42
20.5 a 47.6 b 22.1 a 37.4 b 20.7 a
5.0 a 3.3 b 5.4 a 5.0 a 5.4 a
60.8 c -+1.65
2.4 c -+0.23
I L y s i n e , m e t h i o n i n e , t h r e o n i n e , l e u c i n e , i s o - l e u c i n e a n d valine. 2Values w i t h t h e s a m e s u p e r s c r i p t ~within e a c h c o l u m n are n o t s i g n i f i c a n t l y d i f f e r e n t (P>0.05).
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TABLE VI Performance of groups of five castrated male pigs grown to 32 kg in Experiment 1, and of five entire males grown to 40 kg in Experiment 2, on diets based on buckwheat and wheat Diet Experiment 1 Buckwheat Buckwheat and lysine Buckwheat and meat meal Buckwheat and sunflower meal Wheat Wheat and lysine SE of means Experiment 2 Buckwheat and lysine Buckwheat and iso-leucine Buckwheat, meat meal and sunflower meal Commercial diet SE of means
Gain (g/day) 1
Food (g)/gain (g)
(A) (B) (C) (D) (E) (F)
241 a 289 a 434 b 290 ac 269 a 325 c + 17.9
5.2 a 4.3 b 2.9 c 4.3 b 3.9 b 3.3 bc +-0.20
(G) (H)
410 a 371 b
3.7 a
(J) (K)
433 ac 448 c -+17.4
2.7 b +-0.14
3.4 a
3.1 b
IValues with the same superscript within each row are not significantly different (P>O.05). S u p p l e m e n t a t i o n o f b u c k w h e a t w i t h lysine (B) i m p r o v e d g r o w t h r a t e slightly, and F C R significantly ( P < 0 . 0 5 ) . A d d i t i o n o f m e a t m e a l + lysine (C), b u t n o t s u n f l o w e r m e a l + lysine (D), significantly { P < 0 . 0 5 ) i m p r o v e d b o t h g r o w t h rate a n d F C R o v e r all diets, including t h e high p r o t e i n w h e a t (17% CP) + lysine (F). In t h e s e c o n d e x p e r i m e n t (Table V I ) a d d i t i o n o f lysine t o b u c k w h e a t (F) gave a significant ( P < 0 . 0 5 ) i m p r o v e m e n t in g r o w t h r a t e b u t n o t F C R , c o m p a r e d w i t h b u c k w h e a t + iso-leucine (H). A c o m b i n a t i o n o f m e a t m e a l a n d sunf l o w e r m e a l (J) r e s u l t e d in t h e s a m e p e r f o r m a n c e as t h a t o f t h e c o m m e r c i a l ( c o n t r o l ) d i e t (K).
Disappearance o f amino acids D i f f i c u l t y was e n c o u n t e r e d w i t h m e a s u r e m e n t s o n pigs receiving u n s i f t e d buckwheat owing to frequent blockage of the re-entrant cannulae; only two c o m p l e t e c o l l e c t i o n s w e r e m a d e (Table VII). R e m o v a l o f t h e hull, w h i c h c o m prised a b o u t 20% o f t h e t o t a l grain, f r o m t h e f l o u r resulted in s a t i s f a c t o r y collections. Statistical analysis was .restricted t o d a t a f o r a m i n o acid d i s a p p e a r ance w i t h sifted b u c k w h e a t . T h e r e was a significant d i f f e r e n c e ( P ~ 0 . 0 1 ) b e t w e e n a m i n o acids ( T a b l e V I I ) a n d b e t w e e n pigs, in t h a t Pig 3 gave generally l o w e r values t h a n did t h e t w o others. B o t h leucine a n d iso-leucine gave values l o w e r t h a n t h e m e a n o f o t h e r a m i n o acids e x a m i n e d ; d i s a p p e a r a n c e o f m e t h i o n i n e was higher ( P ~ 0 . 0 5 ) t h a n f o r t h e m e a n o f o t h e r a m i n o acids.
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Laying trial Buckwheat, with or w i t h o u t synthetic lysine and methionine added, resulted in a significant reduction in egg numbers, egg size, and production per hen-day housed compared with the commercial layer diet (Table VIII). There was no significant difference in food intake of hens on the three diets but birds given either buckwheat diet lost significantly more weight than those given the commercial diet (Table VIII). Productivity decreased over time, but there was a diet x time interaction, indicating that the decrease was more rapid on the two buckwheat diets (1 and 2). Addition of the two synthetic amino acids to Diet 1 gave a consistent, but non-significant improvement in performance (Diet 1 vs. Diet 2).
T A B L E VII D i s a p p e a r a n c e (%) o f s o m e a m i n o acids d e t e r m i n e d b y d i f f e r e n c e b e t w e e n t h o s e in feed and in c o r r e s p o n d i n g digesta c o l l e c t e d f r o m r e - e n t r a n t cannulas at t h e terminal ileum o f 3 pigs Pig no.
A m i n o acid Iso-leucine
Leucine
Lysine
Methionine
Valine
Threonine
1" 2*
73 64
78 70
83 70
92 88
85 78
80 79
1 1 2 2 3 3
70 64 78 70 61 44
70 68 76 75 68 49
79 80 85 83 80 69
93 90 92 91 88 82
80 79 85 82 79 68
78 76 76 82 80 63
* U n s i f t e d b u c k w h e a t , r e m a i n d e r received sifted. T A B L E VIII Results o f t h e laying trial over 70 days w i t h 24 birds per dietary t r e a t m e n t Buckwheat I
Eggs ( p e r h e n p e r w e e k ) Egg w e i g h t (g) P r o d u c t i o n (%) F o o d intake (g/d) Loss in w e i g h t (g]70 d)
Commercial
Diet no. (1)
Buckwheat, lysine and methionine Diet no. (2)
3.1 a 54.6 a 45.4 a 111 a 330 a
3.5 a 56.4 ab 50.8 a 120 a 414 a
4.6 b 58.4 b 72.3 b 119 a 159 b
SE of means
Diet no. (3)
~Values w i t h i n a r o w w i t h the s a m e s u p e r s c r i p t are n o t d i f f e r e n t ( P > 0 . 0 5 ) .
-+0.29 +-0.80 -+4.59 + 5.4 +_32.4
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DISCUSSION The results of this study with various domestic species showed that buckwheat was superior to other grains tested when no protein supplement was provided (Tables III--VI). With pigs, unsupplemented buckwheat gave similar results to unsupplemented wheat in the first experiment (Diets A vs. E), and when L-lysine was added to buckwheat, there were responses in food conversion (Experiment 1, Diet B) and growth rate (Experiment 2, Diet G) which did not occur in the rat experiments. Pigs performed significantly better on a diet with high protein wJ~eat with added lysine (Diet F) than on buckwheat even though dietary lysine concentrations were similar. However, the response of pigs to added lysine was not as great as that found by Ivan et al. (1975a,b) although the response of rats was similar to that of Ivan and Farrell (1975). Addition of only 11% meat meal (Diet C) and 10% meat meal and 10% sunflower (Diet J) to buckwheat substantially improved performance, and growth rate and feed conversion on the latter diet was no different (P~0.05) from that observed on the commercial (control) diet (Diet K). Food conversion would be expected to be better on the latter diet because of the higher calculated digestible energy concentration. These findings with growing pigs are in general agreement with those of van Wyk et al. (1952) who showed that growth on a buckwheat diet supplemented with 9% fish, 3% groundnut and 2% lucerne meal was similar to that on diets containing all, or large amounts of, other grain. Nevertheless, van Wyk et al. (1952) concluded that buckwheat should replace only part of the grain in a ration. It was not possible to identify clearly either the first or subsequent limiting amino acids in the chick or in the rat growth studies. Although iso-leucine in Experiment 2 (Table III) appeared to give significant growth response in rats, this was not repeated in Experiment 3, nor in the pig experiment {Diet H, Table VI). This may be explained in part by the low availability of some amino acids as measured with pigs (Table VII), particularly leucine and iso-leucine. Addition of some crystalline amino acids to rat diets may have been inadequate to allow maximum growth rate. Even when buckwheat was supplemented with fish and meat meals, the response in growth rate was much less than that observed on the commercial diet. Amino acid mixtures in Experiment 2 gave a growth response, but it was n o t possible to identify specific limiting amino acids in Experiment 1 (Table V). Because of the high NDF c o m p o n e n t (Table II), it might have been expected that energy concentration would have been the limiting factor. This was apparently n o t so, since addition of maize oil to chick diets, and animal fat (tallow) to rat diets, did not improve performance. Thus rat and chick studies on buckwheat did not provide here a useful guide to responses found subsequently in pig experiments, as was observed previously for the evaluation of wheat by Ivan and Farrell (1975) and Ivan et al. (1975a, b). In the laying trials, buckwheat apparently did not provide sufficient nutrients to allow maximum egg production even when DL-methionine and
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I~lysine were added. By calculation, the diet was adequate in these amino acids for egg production but was only just within the minimum value for dietary energy concentration suggested by the Agricultural Research Council (1975). Because of the substantial loss in weight together with the low egg o u t p u t of birds on Diets 1 and 3 (Table VI), it must be concluded that for some reason hens did not consume sufficient amounts of the diet. Morrison (1957) stated that buckwheat was less palatable than cereal grains. This suggests t h a t buckwheat may contain a toxin, or other chemical compound, affecting acceptability. Such a c o m p o u n d would, in part, explain the disappointing performance observed on m a n y of the buckwheat-based diets for rats and chickens. Because pigs were offered restricted amounts of feed, an acceptability problem would be of less significance than for rats and chickens fed ad libitum. Had hens eaten more food, weight loss would have been reduced during the 101week experimental period but it does not follow that productivity would have been increased substantially. Again, availability of many of the essential amino acids in buckwheat is probably lower than that for most other feed grains (Taverner et al., 1978). Our results do not support the assessment of buckwheat protein of Sure (1955), who stated t h a t " b u c k w h e a t flour, without any amino acid additions approximates the nutritive efficiency of proteins of animal origin of high biological value". Although we found that buckwheat without amino acid addition was superior to cereal grains, no significant improvement in growth rate could be elicited as a result of dietary supplementation for rats and chicks. Supplementation with protein sources usually improved performance but not to t h a t promoted by the control diets. Buckwheat in the diets of pigs gave more positive results when supplemented with lysine or protein sources, even to the extent of equalling growth rate of pigs fed on the commercial diet (Table VI, Diets J and K). It was clear in these two experiments that there was large variation between individual pigs in their growth performance on all of the buckwheat-based diets. Buckwheat has a high fibre content owing to the large a m o u n t of hull, and differences in capacity to digest fibre among individual animals may be of importance, particularly in relation to amino acid absorption. The favourable chemical composition of buckwheat, particularly its relatively high concentration of essential amino acids, was n o t confirmed by the biological performance that it supported. ACKNOWLEDGEMENTS I wish to thank Mrs. Barbara Ward and Mr. Evan Thomson for technical assistance. The University of New England provided financial support for this project. I am grateful to Dr. R.G. Packham of Hawkesbury Agricultural College, who carried out the experiment with laying hens.
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REFERENCES Agricultural Research Council, 1975. The Nutrient Requirements of Farm Livestock No. 1, Poultry. Agricultural Research Council, London. Association of Official Agricultural Chemists, 1970. Official Methods of Analysis, l l t h Edn. Association of Official Agricultural Chemists, Washington. Farrell, D.J., 1976. The nutritive value of buckwheat Fagopyrurn esculentum. Proc. Aust. Soc. Anim. Prod., 11: 413--416. Holmes, J.H.G., Bayley, H.S. and Homey, F.D., 1973a. Digestion and absorption of dry and high moisture maize diets in the small and large intestine of the pig. Br. J. Nutr., 30: 401--410. Holmes, J.H.G., Horney, F.D. and Leadbeater, P.A., 1973b. Re-entrant cannulation of duodenum cranial to pancreatic duct in the pig. Am. J. Vet. Res., 34: 1365--1366. Ivan, M. and Farrell, D.J., 19'75. Nutritional evaluation of wheat. 2. The sequence of limiting amino acids in wheats of different protein content as determined with growing rats. Anim. Prod., 20: 77--91. Ivan, M. and Farrell, D.J., 1976. Nutritional evaluation of wheat. 5. Disappearance of components in digesta of pigs prepared with re-entrant cannulae. Anim. Prod., 23: 111--119. Ivan, M., Giles, L.R., Alimon, A.R. and Farrell, D.J., 1974. Nutritional evaluation of wheat. 1. Effects of preparation on digestibility, metabolizable energy and nitrogen retention in pigs. Anim. Prod., 90: 359--365. Ivan, M., Farrell, D.J. and Edey, T.N., 1975a. Nutritional evaluation of wheat. 3. Effects of supplementation with lysine, threonine and methionine of diets based on wheat containing 13% crude protein on the performance of pigs. Anita. Prod., 20: 267--276. Ivan, M., Farrell, D.J. and Edey, T.N., 1975b. Nutritional evaluation of wheat. 4. Effects of supplementation with amino acids and protein of diets based on wheats containing 10% and 17% crude protein on the performance of growing pigs. Anita. Prod., 20: 277--285. Morrison, F.B., 1957. Feeds and Feeding, 22rid Edn. Morrison, Ithaca, New York. Pomeranz, G. and Robbins, G.S., 1972. Amino acid composition of buckwheat. J. Agric. Food Chem., 20: 270--274. Spackman, D.H., Stein, W.H. and Moore, S., 1958. Automatic recording apparatus for use in the chromatography of amino acids. Anal. Chem., 30: 1190--1206. Sure, B., 1955. Nutritive value of proteins in buckwheat and their role as supplements to protein cereal grains. J. Agric. Food Chem., 9: 793--795. Taverner, M.R., Hume, I.D. and Farrell, D.J., 1978. A study with pigs of amino acid availability in grain. Proc. Second Australasian Poultry and Stock Feed Convention, Sydney, March 1978, pp. 154--157. Van Soest, P.J. and Wine, R.H., 1967. Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell-wail constituents. J. Assoc. Off. Agric. Chem., 50: 50--55. Van Wyk, H.P.D., Verbeck, W.A. and Osthuizin, S.A., 1952. Buckwheat in rations for growing pigs, Farming S. Afr., 27 : 399--402.