Feeding lupins to pigs

Page last updated: Friday, 17 January 2020 - 8:35am

Australian sweet lupins (Lupinus angustifolius L.) are currently utilised as a valuable protein source in pig diets. It is important to understand the variety of lupin species grown, the digestibility and methods for inclusion in pig diets, along with their beneficial characteristics which have been shown to help sustain optimal pig growth and performance.

Lupins

Western Australia (WA) accounts for more than 72% of global lupin production. Having such an abundant protein source available in WA for pig producers is beneficial in reducing the cost of feeding (which usually represents more than 65% of the total production cost for pig meat).

There are some concerns that lupins are an inferior protein source compared with other sources because they contain anti-nutritional factors such as dietary fibre (known as non-starch polysaccharides or NSP), alkaloids, oligosaccharides, protease inhibitors, tannins and saponins.

However, research conducted by the department and Murdoch University showed that current varieties of Australian sweet lupins can replace all of the soybean meal in diets for grower finisher pigs without compromising growth rate, carcass composition or meat quality if the lupin-based diets are adequately fortified with synthetic amino acids.

The chemical and nutritional characteristics of recent varieties of Australian sweet lupins are presented below along with a strategy to efficiently use lupins in pig diets.

Narrow Leaf Lupin in plant form along side a picture of the seeds produced alongside another picture showing ground lupin seeds.
Figure 1 Narrow leafed lupin, seeds and ground lupin seeds.

Suitable species for pig diets

Among numerous lupin species the most cultivated species include Lupinus albus L. (white lupins), Lupinus angustifolius L. (narrow leafed lupins or Australian sweet lupins) and Lupinus luteus (yellow lupins). Lupinus mutabilis is another species that the department's lupin task force is breeding for low alkaloid variety.

White lupins are not recommended for pig feeding as inclusion of these lupins delays gastric emptying and hence decreases feed intake. Australian sweet lupins (Figure 1) and yellow lupins are the most suitable lupin species for feeding pigs.

Physical and chemical composition

Australian sweet lupin varieties, mostly cropped in WA, include Belara, Mandelup, Tanjil and Coromup (which is a high protein variety released in 2007), along with Wonga, Kalya and Quilinock. Thousand seed weight of recent varieties of lupins harvested in the 2006/07 season varied from 124-204 grams (g) between samples and the proportion of hulls ranged from 21-26%, which are limiting amounts of kernel per unit lupin seeds. While crude fat content was constant across sample, crude protein, neutral detergent fibre (NDF), NSP and phytate P varied (Table 1).

Nutritional composition - energy and protein digestion

Digestible energy (DE) content of the lupin sample was determined using 50 kilogram (kg) male pigs and ranged from 13.3-15.7 megajoules (MJ) per kg, with a mean value of 14.2MJ/kg. A 2.4MJ/kg variation in the DE content is economically important considering that 1MJ of energy in diets for pigs currently costs approximately A$40/tonne.

Subsequent research showed that this variable DE content of lupins can be predicted by measuring proportion of hulls (DE = -0.4107 x % hull + 23.998) or weight of thousand seeds (DE = 0.0292 x thousand seed weight + 9.3838), with 88% and 78% accuracy, respectively (Figure 2).

Alternatively a mean of 2-3 repeats of 100 grain weights can be used for prediction of DE with slightly reduced accuracy (DE = 0.2897 x 100 seed weight + 9.4508, R2=0.76). Use of these prediction equations for diet formulation would improve accuracy of dietary energy levels that pigs required at particular physiological status.

Table 1 Variation in physical and chemical composition of recent Australian sweet lupins harvested in the 2006-07 season (n=8). Note acronyms: grams (g), water extractable fraction (WEF), ethanol extractable fraction (EEF), dry matter (DM), gross energy (GE), crude protein (CP), digestible energy (DE), neutral detergent fibre (NDF), acid detergent fibre (ADF), non-starch polysaccharides (NSP), coefficient of variation % (CV1).

Analysed composition

Mean

Minimum

Maximum

CV1Ph

Physical property N/A N/A N/A N/A
1000 seed weight (g) 165 124 204 14
Hull, (% DM) 24 21 26 7
Kernel, (% DM) 76 74 79 2
Chemical Composition N/A N/A N/A N/A
WEF, (g/kg DM) 61 46 85 22
EEF, (g/kg DM) 155 141 164 5
DM, (g/kg) 917 911 926 1
GE, (MJ/kg) 18.6 18.3 18.5 <1
CP, (g/kg) 288 269 319 7
DE, (MJ/kg) 14.2 13.3 15.7 5
Crude fat, (g/kg) 65 61 70 4
NDF, (g/kg) 231 218 257 5
ADF, (g/kg) 231 218 257 5
Lignin, (g/kg) 24 16 39 31
Total NSP, (g/kg) 421 370 512 11
Insoluble NSP, (g/kg) 391 346 479 11
Soluble NSP, (g/kg) 30 24 39 18
Total Phosphorus (P), (g/kg) 3 2.4 3.7 16
Phytate P, (g/kg) 2.1 1.3 2.9 27

As proteins digested in the large intestine are generally not used for body protein synthesis, ileal protein digestibility was measured with 50kg entire male pigs and an average 79% of protein was digestible and available for body protein accumulation (Table 2).

Table 2 Ileal and faecal digestibility of energy and protein

Analysed composition

Ileal

Faecal

Energy digestibility (%)

43 76

Protein digestibility (%)

79 81

Amino acids

Ileal digestible amino acid content of cv. Mandelup was determined using 45kg male pigs. Average apparent and standardised ileal digestibilities of amino acid were 84% and 88% respectively, which is comparable to soybean meal (Table 3).

Table 3 Amino acid composition of Mandelup and apparent and standardised ileal digestibility of amino acids with 50kg male pigs. Note AID: coefficient of variation (%); SID: Standardised ileal digestibility (%), Sum of AA excluding cystine and tryptophan.
Amino acid composition

Chemical content

Lupin (Mandelup)

Ileal digestibility

AID1

Ileal digestibility

SID2

DM (g/kg) 165 124 204
CP (g/kg) 24 21 26
Amino acids (g/kg) N/A N/A N/A
Essential AA 61 46 85
Arg 29.1 94 95
His 8.2 80 82
IIe 13.3 77 80
Leu 20.8 77 80
Lys 15.2 81 84
Met 1.7 64 71
Phe 11.9 73 76
Thr 10.3 77 82
Val 13.3 73 76
Non-essential AA N/A N/A N/A
Ala 10.7 70 76
Asp 28.8 82 85
Glu 60.9 76 78
Gly 13.1 69 75
Pro 12.1 81 97
Ser 12.3 74 77
Tyr 7.1 73 77

Total AA3

269

84

88

Feeding lupins seeds to pigs inclusion level

Inclusion of lupins in diets for growing pigs has been limited to 25% as it was thought that lupins increase the level of dietary NSP and anti-nutritional factors, which in turn compromises nutrient utilisation efficiency and hence growth of pigs.

Table prediction digestibility energy content of Australian sweet lupins.
Figure 2 Prediction of digestible energy content of Australian sweet lupins.
Table predicting the digestible energy content of Australian sweet lupins.
Figure 2a Prediction of digestible energy content of Australian sweet lupins.

The department conducted an experiment to examine the effect of inclusion levels of lupins (cv. Mandelup) at 20, 25, 30 and 35% in diets for pigs on performance from 30kg liveweight until slaughter. The results showed that if diets are formulated based on the ileal digestible amino acid content, a current variety of Australian sweet lupins (cv. Mandelup) can be used up to 350g/kg in diets for grower/finisher pigs. Replacing soybean meal with lupins did not compromise growth performance carcass composition and meat quality (Table 4).

A simple mix of wheat, barley and lupins with essential amino acid supplements supported daily gain of over 1kg with an FCR of 2.7 between 27–108kg liveweight without showing deleterious effects. As sows and gilts react differently to dietary fibre, maximum inclusion needs to be limited to 20% until release of further research information.

Table 4 Effect of lupin inclusion level on performance and carcass characteristics. Meat quality traits were not different between treatments.
Effect

Lupin concentration (200g/kg)

Lupin concentration (250g/kg)

Lupin concentration (300g/kg)

Lupin concentration (350g/kg)

Initial weight (kg) 27 27 27 27
Final weight (kg) 108 108 108 108
ADG (kg/day) 1.00 1.01 1.01 1.03
VFI (kg/day) 2.72 2.74 2.76 2.68
FCR 2.73 2.71 2.74 2.62
Days to 104kg 77.8 76.7 77.4 76.3
Hot carcass weight 69.9 70.0 69.7 69.5
Dressing percentage 65.0 64.9 64.8 64.5
P2 back fat (mm) 13.6 13.5 14.0 14.0

Grinding

Hulls and kernels of Australian sweet lupins are durable and hard to break, which means without reasonable mechanical grinding, nutrients in lupins would not be digested and absorbed efficiently. To test this hypothesis an experiment was conducted investigating the impact of grinding of lupins on the energy and amino acid availability when fed to grower/finisher pigs.

Lupins (cv. Mandelup) were ground to have mean particle sizes varying between 567 micrometres (µm) and 1304µm, which are typical of the range found in commercial production, and fed to pigs. The results showed that decreasing particle size of lupins from coarse to fine (1304µm–567µm) significantly increased ileal digestible nitrogen (N), energy and amino acids (Figure 3). In general, every 100µm increase in lupin particle size over 567µm reduced ileal digestible N, energy, and other essential amino acids in lupin seeds by 4-6% units.

Figure 3 shows the effect lupin particle size has on apparent ileal digestibility of energy, nitrogen and amino acids.
Figure 3 Effect of lupin particle size on apparent ileal digestibility of energy, nitrogen and amino acids.

Anti-nutritional factors and supplementation of exogenous enzymes

Research showed that even young grower pigs (30kg liveweight) can effectively handle lupin fibre (NSP) at 35% dietary inclusion levels. However there are possibilities to increase feed intake and hence growth rate by using lupin-specific enzymes (polygalacturonase and pectin methyl esterase) as it was found in a poultry study. These enzymes are not commercially available to date but may be a strategy in the future. Among other anti-nutritional factors, alkaloid content was a concern in the past and should be monitored to limit dietary alkaloid contents of 0.2g/kg, which is the maximum level that maintains pig performance. Since diet formulations rarely have more than 350g/kg lupin seed, alkaloids only become a problem when they exceed 0.6g/kg of the seed.

As alkaloid content of recent varieties of Australian sweet lupins ranges from 0.1-0.4g/kg with a mean content of 0.2g/kg, poor pig performance due to alkaloids in sweet lupin varieties is unlikely. Other anti-nutritional factors such as oligosaccharides, trypsin inhibitors, chymotrypsin inhibitors, tannins, saponins and phytin are similar to the levels found in SBM and can be considered low enough for use in pig diets without problems.

Diet formulation with lupin seeds

Formulating diets has to account for many nutritional and biological principles for the particular physiological status of the target pigs to supply precise nutritional requirements at cheapest price. Producers are recommended to seek advice from qualified consultants/feed manufacturers for specific diet formulations.

The diets presented in Table 5 are provided only as a guide. Although these diets are nutritionally adequate, they may not represent the cheapest solution.

Table 5 Typical grower-finisher diets with sweet narrow-leafed lupins.

Ingredient

Grower (25-55kg)

Finisher (56-90kg)

Pre-sale (>90kg)

Wheat 660 541 477 11 0 0
Barley 0 34 232 576 703 619
Lupins 250 350 250 350 250 350
Meat meal 41 0 13 0 27 0
Fish meal 16 15 0 0 0 0
Canola oil 14 27 0 31 0 2
L-Lysine 4.2 4.0 2.3 1.4 0.3 0
DL-Methionine 1.2 1.4 0.8 0.8 0.3 0.5
L-Threonine 1.2 1.1 0.6 0.3 0 0
L-Tryptophan 0.3 0.2 0 0 0 0
Vit/Min1 0.7 0.7 0.7 0.7 0.7 0.7
Limestone 2.4 6.8 6.2 7.5 4.9 7.6
Dicalcium phosphate 7.9 17.7 15.9 18.8 12.0 18.6
Salt 1 1 1 1 1 1
Choline CI 0 0 0.4 0.7 1.1 0.7
Chemical composition 0 0 0 0 0 0
DE (MJ/kg) 14.0 14.0 13.2 13.2 12.5 12.5
CP (%) 19.5 19.5 17.0 17.3 16.4 17.4
Av Lysine (%) 0.98 0.98 0.73 0.73 0.60 0.63
Av P (%) 0.45 0.45 0.45 0.45 0.45 0.45
Ca (%) 0.90 0.90 0.90 0.90 0.90 0.90

1Vitamin/mineral premix.

Note: amounts in kg to make up one tonne of feed.