The energy value of
Lupinus angustifolius
and
Lupinus albus
for growing pigs
R.H. King
a,*, F.R. Dunshea
a, L. Morrish
a, P.J. Eason
a,
R.J. van Barneveld
b, B.P. Mullan
c, R.G. Campbell
d aVictorian Institute of Animal Science, Private Bag 7, Sneydes Rd., Werribee, Vic. 3030, AustraliabSARDI-Pig and Poultry Production Institute, GPO Box 397, Adelaide, SA 5001, Australia cAnimal Research and Development Services, Agriculture WA, Locked Bag 4,
Bentley Delivery Centre, WA 6983, Australia
dBunge Meat Industries, PO Box 76, Corowa, NSW 2646, Australia
Received 24 November 1998; received in revised form 24 March 1999; accepted 24 September 1999
Abstract
Ninety male crossbred pigs were allocated at 30 kg live weight to a 65 factorial experiment involving six diets and five levels of feeding where average daily intakes were 1.11, 1.36, 1.67, 1.90 kg and ad libitum between 30 and 60 kg live weight. The control diet contained predominantly animal protein sources, another four diets contained 350 g/kg of either kernels or seeds of either
L. angustifoliuscv. Gungurru orL. albuscv. Kiev while the remaining diet contained 350 g/kg of peas. All diets were formulated to contain 15.3 MJ DE/kg and 0.7 g available lysine/MJ DE to ensure that dietary protein was adequate. Six estimates of the digestibility of each protein source were determined by the total faecal collection method. The digestible energy contents (SE) of
L. angustifoliusseed and kernel,L. albusseed and kernel and peas were 15.81 (0.18), 16.85 (0.76), 16.84 (0.34), 17.70 (0.47) and 14.98 (0.15) MJ/kg air dry, respectively. All pigs were killed at 60 kg live weight and the dressing percentage of pigs givenL. angustifoliusandL. albusdiets were 2.6 and 4.7 units lower than the mean dressing percentage of pigs given the other diets. The major factors contributing to this reduction in dressing percentage when lupins were offered to pigs were gut fill and differences in intestinal weight. The relative energy value of the protein sources was assessed by comparing the relationship between the rates of energy deposition in the empty body and DE intake for the diets.
The response of energy deposition to energy intake was similar for kernel and seed for both
L. angustifoliusandL. albusand thus data for kernel and seed were consolidated for both types of lupins. The respective linear relationships between energy deposited in the empty body (E, MJ/day)
Animal Feed Science and Technology 83 (2000) 17±30
*Corresponding author. Tel.:61-3-9742-0441; fax:61-3-9742-0400.
E-mail address: [email protected] (R.H. King).
and DE intake (DE, MJ/day) for the diets, with appropriate SE of the coefficients in parenthesis, were:
Animal protein diet: E0.630 (0.043)DEÿ4.95 (0.99)R20.947p< 0.001
L. angustifoliusdiet: E0.485 (0.035)DEÿ4.88 (0.86)R20.872p< 0.001
L. albusdiet E0.403 (0.033)DEÿ4.35 (0.78)R20.862p< 0.001 Pea diet: E0.582 (0.083)DEÿ5.01 (1.96)R20.816p< 0.001.
The net energy content of the protein sources were calculated to be 5.6, 6.5, 3.0, 4.6 and 8.3 MJ/ kg for L. angustifolius seed, L. angustifolius kernel, L. albus seed, L. albus kernel and peas, respectively.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Pigs; Energy; Lupins
1. Introduction
Lupins are a valuable source of protein for pigs and Lupinus angustifolius has been used extensively in diets for growing pigs. Cultivars of Lupinus albus contain more protein, fat and energy thanL. angustifoliuscultivars and thus offer more potential as an ingredient for pig diets. The levels of anti-nutritional factors are similar for both species but are relatively low and are unlikely to constrain the use of these lupin species for animal feeding. For example, the levels of alkaloids, total tannins, oligosaccharides and trypsin inhibitor in the seeds ofL. angustifoliuscv. Gungurru andL. albuscv. Kiev are 0.2 and <0.1 g/kg, 3.2 and 3.7 g/kg, 51.6 and 66.9 g/kg and 0.14 and 0.13 mg/kg, respectively (Pettersen and Mackintosh, 1994). In addition, the level of total non-starch polysaccarides in lupins is quite high (405 g/kg) relative to other more common protein sources such as soya-bean meal, peas and canola (Bach Knudsen, 1997). However, the major uncertainty facing the use of lupins in pig production is to ascribe an accurate energy value to lupins. Lupins are a unique feedstuff in that, although overall digestibility of dry matter and energy is relatively high (ca. 0.85), a considerable proportion of energy is digested in the hind gut. For example, (Taverner and Curic, 1983) found that the proportion of total digested energy that disappeared in the hind gut was 0.47 forL. angustifolius whereas only 0.05 of the energy in peas was digested in the hind gut.
Energy that is absorbed from the hind gut is utilised less efficiently by the pig than energy which is absorbed from the small intestine. Thus, the energy from lupins that is available to the pig is likely to be lower than anticipated from its digestible energy (DE) and metabolisable energy (ME) contents. A more useful measure is net energy (NE) which is defined as ME minus the amount of heat released due to the energy cost of the digestion processes and nutrient metabolism and, as such, is the best measure of the energy value of a diet as only NE is proportional to the energy value of diets for productive purposes.
The aim of this experiment was to determine the amount of energy in lupin-based diets that is deposited in the body of growing pigs and compare this with the efficiency of energy utilisation with diets containing other protein sources.
2. Materials and methods
2.1. Animals and treatments
Ninety-six male crossbred pigs were used in a growth study. Six pigs were killed at 30 kg live weight to provide representative information on initial body composition. The remaining 90 pigs were allocated at 30 kg live weight to a 65 factorial experiment involving six diets (Table 1) and five levels of feeding where average daily intakes were extended over a wide range and were expected to be 1.15, 1.40, 1.65, 1.90 kg and ad libitum based upon sliding feeding scales which increased according to live weight. The diets contained either predominantly animal protein sources, L. angustifolius cv. Gungurru (kernels or seeds), L. albus cv. Kiev (kernels or seeds) or field peas and were formulated to contain 15.3 MJ DE/kg and 0.7 g available lysine/MJ DE. The seeds of lupins were commercially dehulled and cleaned to produce sufficient quantities of clean lupin kernel for the experiments. The available lysine content of the diets was calculated from estimates of lysine availability provided by Standing Committee on Agriculture (1987) for the individual ingredients in each diet. The ratios of other essential amino acids to lysine were in excess of those ratios suggested by Standing Committee on Agriculture (1987) and the diets were considered to be adequate in protein and essential amino acids (Standing Committee on Agriculture, 1987). The amino acid composition of diet ingredient samples was determined by the method of Spackman et al. (1958) on a Waters ion-exchange amino acid analysis column using post-column derivitisation with ninhydrin. Chemical analysis for crude protein, dry matter, ether extract, crude fibre, acid-detergent fibre, neutral detergent fibre and ash were undertaken using the methods of the Association of Official Analytical Chemists (1984). Non-starch polysaccharides were determined using modifications of the methods described by Theander and Westerlund (1993).
2.2. Husbandry and management
longitudinally after the head was removed and subsequently, the right side was also stored atÿ208C. The right side of each frozen carcass and frozen gut and internal organs were ground separately, and a sample of each was analysed for dry matter, ash and protein Table 1
Composition of experimental diets (g/kg air dry basis)
Constituent Diet
1 2 3 4 5 6
Wheat 747.5 458.8 512.6 502.3 530.2 468.4
Blood meal 35.0 35.0 35.0 35.0 35.0 35.0
Fish meal 90.5 54.6 12.0 27.3 3.6 14.6
Skim milk powder 50.0 50.0 50.0 50.0 50.0 50.0
L. angustifolius(seed) ± 350 ± ± ± ±
Dicalcium phosphate ± 5.7 12.1 9.8 13.3 12.2
Limestone 9.1 7.8 8.2 8.0 11.1 7.4
L-lysine 0.4 0.3 1.5 0.8 1.5 ±
Threonine 0.4 ± ± ± ± 0.6
DL-Methionine ± 1.2 1.4 1.0 1.3 1.5
Vitamin/Mineral premixa 2.0 2.0 2.0 2.0 2.0 2.0
Salt 2.0 2.0 2.0 2.0 2.0 2.0
13.50 (0.11) 14.37 (0.28) 14.89 (0.13) 14.66 (0.13) 15.39 (0.17) 13.85 (0.26)
Metabolisable energyc (MJ/kg)
12.80 (0.16) 13.66 (0.27) 14.22 (0.13) 14.05 (0.18) 14.71 (0.15) 13.03 (0.27)
Gross energy (MJ/kg) 15.76 16.84 17.03 17.31 17.67 16.27
Crude proteinb 192 236 244 238 248 188
Lysineb 11.2 12.9 13.0 12.9 13.2 11.6
Calciumb 8.0 8.0 8.0 8.0 9.0 8.0
Available phosphorusb 4.0 4.0 4.0 4.0 4.0 4.0
Methionineb 3.6 4.2 3.9 3.9 4.0 4.1
Methionine and cystineb 6.2 7.1 7.2 7.4 7.7 6.4
Threonineb 7.3 8.4 8.5 8.9 9.0 7.6
Tryptophanb 2.3 2.4 2.4 2.3 2.4 2.0
Isoleucineb 6.5 8.5 8.7 8.7 9.1 7.0
aProvided the following nutrients in mg per kg of air dry diet: retinol, 6.4; cholecalciferol, 0.083;
menadione, 0.60; riboflavin, 3.3;/-tocopherol, 22; nicotinic acid, 16.5; pantothenic acid, 5.5; pyridoxine, 1.1; choline, 1100; cyanocobalamin, 0.07; biotin, 0.56; folic acid, 1.0; Fe, 88; Zn, 55; Mn, 22; Cu, 6.6; Co, 0.5; I, 0.22; Se, 0.1.
bCalculated from analyses determined for lupins and peas in the digestibility study and from estimated
values of other ingredients (Standing Committee on Agriculture, 1987).
cDE and ME contents of the diet (meanSE) where determined in digestibility studies with six male pigs
content by the methods of Campbell et al. (1984). The gross energy content of each sample was determined on freeze-dried samples in an adiabatic bomb calorimeter. The amounts of nutrients in the blood and head were added to carcass and viscera data to obtain the composition of the empty body of pigs. The water, protein, fat, ash and gross energy contents of blood and head was assumed to be 820, 164, 6 and 7 g/kg and 4.15 MJ/kg (McDonald et al., 1966) and 627.8, 170.8, 141.5 and 59.9 g/kg and 9.59 MJ/ kg (R.H. King, unpublished data), respectively.
2.3. Digestibility studies
The DE contents of peas and the kernels and whole seeds of bothL. angustifoliusand L. albuswere determined in a metabolism experiment involving 36 male pigs of ca. 55 kg live weight. Six pigs were given a basal diet containing 955 g wheat/kg, 20 g dicalcium phosphate/kg, 15 g limestone/kg, 5 g salt/kg and 5 g mineral/vitamin premix/kg. Six pigs were also given a test diet in which 400 g/kg of the basal diet was replaced by one of five protein supplements. The DE contents of the protein sources were calculated by difference. Pigs were given 1.80 kg/day (except for theL. albusdiets where only 1.0 kg was offered each day because of low voluntary food-intake on these diets) for 14 days and total faecal output was collected daily for the last five days of this period. This difference in level of feeding is not likely to affect the digestibility of energy determination in growing pigs (Whittemore, 1993). Faeces were weighed, mixed, subsampled and subsequently freeze-dried.
The DE and ME contents of diets used in the growth study (Table 1) were also determined in a metabolism experiment involving 36 female pigs of 65 kg live weight. Pigs were given 1.5 kg/day for 14 days and total faecal output was collected daily for the last five days of this period. In addition urine was collected daily via Foley bladder catheters into sulphuric acid, subsequently weighed and 10% (w/w) samples of urine were taken. Frozen daily samples of urine were bulked for each pig at the end of each collection period. The gross energy of all diets, ingredients, freeze-dried faeces samples and urine samples were determined in an adiabatic bomb calorimeter.
2.4. Statistical analysis
Data were subjected to analysis of variance for a completely randomised design (Snedecor and Cochran, 1967). The responses to feeding level were tested for linearity and curvilinearity if there were significant treatment effects. Linear regression coefficients of response of energy deposition to increasing energy intake were calculated and compared between diets. The linear regression coefficients provided a relative efficiency utilisation in the respective diets.
3. Results
The average (SE) DE content of the basal wheat diet on an air-dry basis was 13.28 (0.04) MJ/kg and the energy contents of the protein sources are presented in Table 2.
Use of a sliding scale in allocating feed ensured that the feed intake of each group of pigs was reasonably close to the nominated feed intake (Table 3). There were no significant interactions between diets and feeding level for any of the growth performance data or body organ weights and only main effects are presented (Table 3). On an empty body basis, pigs offered the diet containing predominantly animal protein grew faster and more efficiently than pigs offered diets containing vegetable proteins. The growth performance of pigs given diets containing either the seeds or kernels ofL. angustifolius was similar to that of pigs given peas, but was usually superior to that of pigs receiving diets containing the seeds or kernels ofL. albus.
The carcass yield or dressing percentage of pigs given lupins, particularlyL. albus, was lower than that of pigs receiving the diet containing animal protein and could be attributed in part to differences in gut fill (Table 3). In addition, the weights of liver, heart and kidney in pigs given the lupin diets were often significantly greater than the weights of these organs in pigs given diets containing either peas or predominantly, animal protein Table 2
The composition of dietary ingredients (g/kg air dry basis)
L. angustifolius L. albus Peas
Seed Kernel Seed Kernel
Dry matter 911.1 911.5 929.5 925.5 905.6
Crude fibre 131 21 102 18 60
Crude protein 290 372 332 395 236
Fat 53 67 95 114 11
Ash 25 25 31 33 24
Lysine 13.0 16.5 15.6 18.0 15.3
Methionine 1.7 2.2 2.4 2.8 2.4
Methionine and cystine 4.9 6.6 7.4 8.7 4.9
Threonine 9.4 12.3 12.3 14.0 8.3
Gross energy (MJ/kg) 18.06 18.92 19.63 20.38 16.80
Digestible energy (SE) (MJ/kg)
15.81 (0.18) 16.85 (0.76) 16.84 (0.34) 17.70 (0.45) 14.98 (0.15)
Table 3
The effects of dietary protein sources and feeding level on growth performance and body organ weights of pigs grown between 30 and 60 kg live weight
Main effect Dietary protein sourcea Feeding level Significance of
response Animal L. angustifolius L. albus Peas SED 1.15 1.40 1.65 1.90 Ad libitum SED Linear Quadratic
Seed Kernel Seed Kernel
Feed intake (kg/day) 1.62 1.63 1.63 1.56 1.62 1.60 0.04 1.11 1.36 1.67 1.90 2.00 0.04 *** NS
Growth rate(g/day)
Live weight basis 801 a 741 b 736 b 656 c 651 c 730 b 26 367 614 768 878 969 23 *** NS Empty body basis 756 a 687 b 676 b 594 c 599 c 693 b 24 340 577 722 812 893 22 *** *
FCR
Live weight basis 2.07 a 2.34 b 2.27 ab 2.45 bc 2.68 c 2.32 ab 0.11 3.12 2.25 2.19 2.18 2.12 0.10 *** *** Empty body basis 2.16 a 2.52 b 2.60 b 2.72 bc 2.89 c 2.46 b 0.13 3.39 2.40 2.34 2.36 2.30 0.12 *** *** Protein deposition in
empty body (g/day)
142 a 136 ab 127 bc 117 c 118 c 134 ab 5 69 112 139 158 166 5 *** * Carcass yield 0.787 a 0.767 bc 0.756 cd 0.738 c 0.743 de 0.778 ab 0.008 0.780 0.773 0.761 0.750 0.745 0.007 *** NS Gut fill (g) 2330 c 3190 ab 3650 a 3960 a 3388 ab 2646 bc 385 3342 2920 2937 3289 3482 351 NS NS Empty viscera (g) 6666 b 6855 b 6925 b 7526 a 7524 a 6754 b 176 6272 6679 7146 7490 7623 161 *** NS
Organ weights(g)
Liver 1176 c 1193 bc 1294 ab 1342 a 1353 a 1167 c 56 956 1118 1277 1410 1511 51 *** NS Kidney 261 bc 272 bc 273 bc 283 ab 305 a 248 c 12 227 254 271 306 311 11 *** NS Heart 238 b 241 ab 240 ab 259 a 257 a 238 b 8 241 254 241 246 245 8 NS NS Spleen 102 100 97 103 108 102 9 93 98 107 103 109 8 NS NS Stomach 379 c 454 a 438 ab 428 ab 386 c 406 bc 16 422 440 408 420 385 15 * NS small intestine 1579 b 1402 c 1492 bc 1751 a 1767 a 1533 b 60 1364 1551 1626 1702 1696 55 *** NS large intestine 939 c 1212 a 1140 ab 1312 a 1261 a 1027 bc 56 1103 1055 1145 1170 1270 51 *** NS
aWithin rows and for the dietary protein source main effect, means with different letters are significantly different (
(Table 3). There were small and inconsistent differences in the weight of the stomach but the empty weight of the small intestine of pigs givenL. albuswas heavier than that of pigs receiving the other diets. Furthermore, large intestine weights were greater in pigs giveL. albus compared to pigs receiving animal protein or peas with the weight of the large intestine of pigs given L. angustifolius being intermediate. Dressing percentage decreased linearly as feeding level increased (Table 3). In association with this response of dressing percentage to feeding level, viscera weight, particularly liver, kidney, small intestine and large intestine increased linearly as feeding level increased.
The only significant interaction observed between diet and feeding level occurred for the rate of energy deposition in the empty body of pigs (Table 4). The interaction (p< 0.01) indicated that the linear increases of energy deposition in pigs given the lupin diets were less than that for pigs given the diets containing peas or predominantly animal protein. As the relationship between energy balance and energy intake is linear above the energy intake required for maintenance (Noblet and Henry, 1991), linear regression coefficients of the relationship between energy deposition rate and energy intake were compared between diets. The response of energy deposition to energy intake was similar for kernel and seed for bothL. angustifoliusandL. albusand thus the data for kernel and seed were consolidated for both types of lupins. The respective linear relationships between energy deposited in the empty body (E, MJ/day) and ME intake (ME, MJ/day) or DE intake (DE, MJ/day) for the diets, with appropriate SE of the coefficients (in parenthesis), were:
Animal protein diet
E0:630 0:043 DEÿ4:95 0:99 R20:947 p<0:001 (1)
E0:664 0:046 MEÿ4:95 0:99 R20:947 p<0:001 (2)
L. angustifoliusdiet
E0:485 0:035 DEÿ4:88 0:86 R20:872 p<0:001 (3)
E0:506 0:037 MEÿ4:85 0:86 R20:870 p<0:001 (4)
Table 4
The effects of dietary protein source and feeding level on energy deposited in the empty body of pigs grown between 30 and 60 kg live weight
Feeding level (kg/day) Diet (energy deposited in MJ/day)
Animal L. angustifolius L. albus Peas
Seed Kernel Seed Kernel
1.15 4.18 2.83 2.57 2.28 2.28 2.94
1.40 6.48 4.42 4.98 3.10 4.29 5.72
1.65 9.63 7.93 7.14 5.31 6.10 7.69
1.90 11.01 9.30 9.12 7.28 7.04 10.89
Ad libitum 12.92 9.07 9.38 6.82 8.61 11.30
L. albusdiet
E0:403 0:033 DEÿ4:35 0:78 R20:862 p<0:001 (5)
E0:422 0:034 MEÿ4:36 0:78 R20:863 p<0:001 (6)
Pea diet
E0:582 0:083 DEÿ5:01 1:96 R20:816 p<0:001 (7)
E0:618 0:089 MEÿ5:01 1:96 R20:816 p<0:001 (8)
4. Discussion
4.1. Growth performance and energy utilisation
The growth performance of pigs given lupin, particularlyL. albus, was inferior to that of pigs given the diets containing high quality protein derived from animal sources. King (1981) also found that pigs offered diets containing 330 g/kg of either L. albus and L. angustifoliusgrew slower and less efficiently than pigs offered a diet of similar nutrient composition, but containing soyabean meal as the sole protein supplement. Likewise, pigs fed diets containing 350 g/kg ofL. albusandL. angustifoliusseeds or kernels grew more slowly than those fed either an entirely wheat diet or a wheat diet containing peas (Gannon et al., 1996). Although the apparent i1eal digestibility of lysine in lupins is high (0.86±0.93), the lysine availability estimated from the growth slope-ratio assay is much lower (Standing Committee on Agriculture, 1987). Batterham et al. (1984) suggest that the reduced performance of pigs given lupins could be attributed to low availability of amino acids in lupins. However, in our experiment the reduced feed efficiency and protein deposition is unlikely to be due to dietary amino acid inadequacy as all diets were formulated to contain 0.7 g available lysine/MJ DE which is in excess of that required for pigs 20±45 kg live weight (Standing Committee on Agriculture, 1987). In addition, the calculation of the available lysine content of the diet was based upon a lysine availability of 0.54 in lupins (Batterham et al., 1984) which is likely to be very conservative (van Barneveld et al., 1997).
The diets for the slope-ratio assays that Batterham et al. (1984) used to determine lysine availability inL. angustifoliuswere formulated on a DE basis. The NE of the lupin diets would have been lower than that of the control diets and this may have contributed to the lower growth performance and the relatively low lysine availability reported by Batterham et al. (1987). van Barneveld et al. (1997) recently reported that the lysine availability determined using a slope-ratio analysis inL. angustifoliusseeds and kernels andL. albusseeds and kernels was 0.75, 0.79, 0.67 and 0.76, respectively, while that of peas has been reported to be 0.93 (Standing Committee on Agriculture, 1987).
utilisation of ME in terms of energy retained in the empty body of pigs as a proportion of ME intake was significantly less inL. angustifoliusdiets compared to diets containing either animal protein or peas, and was further reduced forL. albusdiets. It is likely that the low efficiency of use of ME is because a greater proportion of energy in lupins is digested in the large intestine. For example, Taverner and Curic (1983) found that, although 0.81 of the GE inL. angustifoliuswas digested, the large intestine was the site for digestion of 0.47 of the GE in L. angustifolius, whereas in peas only 0.05 of the energy was digested in the hind gut.
In the hind gut, a large proportion of carbohydrates is fermented to volatile fatty acids, while protein and amino acids are probably synthesised into microbial matter that would be excreted in faeces, or catabolised to ammonia and/or amines and excreted in the urine (Just et al., 1981). Furthermore, gas production takes place in the hind gut with the energy in the gases being lost but counted as having been absorbed. Thus, much of the digested energy in the hind gut is wasted and the efficiency of utilisation of ME or NE/ME ratio decreases in a linear fashion as the proportion of digested energy absorbed from the hind gut increases (Just et al., 1983).
4.2. Net energy
Net energy is defined as ME minus heat increment associated with metabolic utilisation of ME and the energy cost of ingestion and digestion of the feed, but may also be defined as the sum of energy retained for productive purposes and fasting head production (Noblet et al., 1994). In our experiment, the amount of energy deposited in the body of pigs was measured directly and fasting heat production may be estimated from the relationship with body weight developed by Noblet et al. (1994). The NE of the diets used in our experiment was calculated for pigs weighing an average of 45 kg and receiving 26 MJ ME/day (Table 5).
If the NE of the balance of ingredients in the lupin and pea diets is assumed to be similar to that of the animal protein diet, the actual NE content inL. angustifoliusseed can be calculated accordingly: NE L. angustifolius seed(1.0/proportion of lupins in diet)(NE L. angustifolius seed dietÿ(NE animal protein dietproportion of other
Table 5
Estimation of the net energy content of the diets fed to pigs between 30 and 60 kg live weight
Diet Animal L. angustifolius L. albus Peas
Seed Kernel Seed Kernel
Energy content (MJME/kg) 12.80 13.66 14.22 14.05 14.71 13.03
Energy intake (MJME/day) 26 26 26 26 26 26
Feed intake (kg/day) 2.03 1.90 1.83 1.85 1.77 2.00
Energy retaineda(MJ/day) 12.31 8.31 8.31 6.61 6.61 11.06
Fasting heat productionb(MJ/day) 7.35 7.35 7.35 7.35 7.35 7.35
Net energy (MJ/day) 19.66 15.66 15.66 13.96 13.96 18.41
Net energy (MJ/kg) 9.68 8.24 8.56 7.35 7.89 9.21
ingredients in lupin diet))(1.0/0.35)(8.24ÿ(9.680.65)) MJ/kg5.6 MJ/kg. Similarly, the NE contents of L. angustifolius kernel, L. albus seed, L. albus kernel and peas would be 6.5, 3.0, 4.6 and 8.3, respectively.
These estimates of the NE contents of peas and, particularly, lupins do appear lower than previous estimates. Taverner and Curic (1983) estimated the NE contents of peas and L. angustifoliusseed were8.7 and 6.6 MJ/kg air dry, respectively. However, the fasting heat production was assumed to be dependent only upon body weight (Noblet et al., 1994). There may be a greater requirement for energy for maintenance in pigs fed L. albus because of the greater visceral mass. Consequently, the NE contents of lupin diets, as calculated in our experiment as the sum of fasting head production and energy retained, may be actually higher than values presented in Table 5. Nevertheless, the possible greater maintenance requirement of pigs fed lupins should still be considered as a specific energy cost of feeding lupins.
4.3. Anti-nutritional factors
Mechanical separation and removal of the testa of lupin seed failed to eliminate any factor responsible for the depressed growth performance of pigs given lupins. Within each species of lupins, growth performance and efficiency of energy utilisation was similar, irrespective of whether lupins was offered to pigs as a whole seed or as the kernel. Much of the crude fibre and neutral-detergent fibre is removed with the separation of the testa. However, other dietary fibre fractions such as soluble non-starch polysaccharides, and oligosaccharides are found in appreciable quantities in the kernel and are likely to be responsible for the increased hind gut fermentation and poor efficiency of energy utilisation observed with lupin seed and kernels. These fractions, particularly non-starch polysaccharides, may hinder the action of digestive enzymes in the small intestine and affect microbial activity, and interfere with hind-gut digestion (van Barneveld et al., 1995a).
Little work has been done to quantify the anti-nutritional effects of non-starch polysaccharides from lupins for growing pigs. The main non-starch polysaccharide of lupins is a highly complex branched structure containing long galactose side chains and side chains of arabinose attached to a pectin-like main chain of rhamnose and galacturonic acid (Moughan et al., 1999). van Barneveld et al. (1995b) showed that addition of graded levels of isolated lupin non-starch polysaccharides to sorghum-based diets resulted in decreases in the ileal digestibilities of dry matter and energy.
carbohydrate profile appears to be the major constraint to the nutritive value of lupins for pigs because of its influence on the digestion of energy and other nutrients.
4.4. Digestible energy content
The estimates of the DE content of the seed ofL. angustifolius range from 12.3 to 15.3 MJ/kg (Standing Committee on Agriculture, 1987; Wigan et al., 1994) which is below our estimate of 15.8 MJ/kg. However, the DE content of lupins is often dependent upon the fineness of grinding and the composition of the basal diet in which lupins has been included (Wigan et al., 1995). The DE estimate of the kernels was 16.9 MJ/kg which again is beyond the upper range of 15.4 to 16.6 MJ/kg compiled by Wigan et al. (1994). There is less information on the DE content of L. albus, but the greater oil content of L. albusvarieties should be reflected in greater DE estimates. In our experiment the DE content of L. albus seeds and kernels was 16.8 and 17.7 MJ DE/kg, respectively. The difference in DE content between the whole seed and kernel ofL. albuswas similar to that which is observed forL. angustifolius. In addition, King (1981) reported that the DE content ofL. albus cv. Hamburg was similar, being 16.9 MJ DE/kg.
The determined DE content of the diet containingL. albuswas similar to the estimated value. However, the direct determination of the DE content of other diets was often lower than that predicted from the DE content of individual ingredients of each diet. The differences between the estimated and determined DE contents of the diets appeared to be related to the level of fat blend in the diets. Increases in the level of fat in the diets coincided with a reduction in the DE content of the diet which suggests that the DE content of fat blend, which was assumed to be 34 MJ/kg, may have been overestimated in the calculation of the DE contents of the diets.
4.5. Carcass yield
5. Conclusions
The results of this experiment indicate that DE is a poor estimate of the available energy in diets containing either seed or hulls of L. angustifolius and L. albus. The utilisation of energy in lupins by the growing pigs is low because a considerable proportion of energy is digested in the large intestine. The actual DE and ME utilisation efficiencies in diets containingL. angustifoliusandL. albuswere significantly less than in the control diets. Consequently the estimated NE content of lupins will be substantially lower than other feedstuffs used in commercial diet formulation. In particular, the utilisation of dietary energy and NE content of L. albusis unacceptably low and this feedstuff is unlikely to be used as a major ingredient in commercial pig diets, particularly in view of its adverse effects on voluntary feed intake (Gannon et al., 1996).
Acknowledgements
The authors thank Maurie Miles for grinding up the carcasses and Genny Power for assisting in the digestibility studies. Dr Arnold Just, Danish Institute of Agricultural Science, Denmark, provided helpful comments on the manuscript. The financial assistance of the Pig Research and Development Corporation is also gratefully acknowledged.
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