Because weanling pigs cannot properly digest soybean meal, animal proteins such as fish meal and spray-dried plasma protein are often used in starter diets. However, the cost of these ingredients has become prohibitive for many swine producers, and new sources of digestible protein for weanling pigs are being sought.
Researchers at the Stein Monogastric Nutrition Lab have been studying a co-product of the production of synthetic L-Threonine, which is used as a supplement in low-protein diets. Synthetic L-Threonine is produced by fermenting a carbohydrate substrate using bacteria such as E. coli. Threonine is extracted from the fermentation broth. The leftover biomass and substrate have the potential to be used as a feed source, but little is known about its nutritional value. Two experiments were conducted to measure amino acid digestibility and energy concentration in a threonine co-product that is produced by drying this left-over biomass.
Threonine co-product: An even better source of protein and amino acids than fish meal
Three diets were formulated. The first contained 20% threonine co-product for a total of 18% crude protein, and the second contained 25% fish meal for a total of 19% crude protein. Finally, a nitrogen-free diet was used to determine basal endogenous losses of protein and amino acids.
The concentration of crude protein and all indispensable amino acids was greater in threonine co-product than in fish meal (Table 1). Even the concentration of threonine was greater, indicating that the process which extracts threonine from the bacterial biomass is incomplete.
The standardized ileal digestibility of crude protein and all indispensable amino acids except tryptophan was greater (P < 0.05) in threonine co-product than in fish meal. The digestibility of tryptophan did not differ between the two ingredients. However, because the concentration of tryptophan was greater, there was more digestible tryptophan in threonine co-product than in fish meal.
A good source of energy, too
For the second experiment, barrows were fed diets containing 96.4% corn, 79.3% corn + 17% threonine co-product, or 75.3% corn + 24% fish meal.
The concentration of digestible energy in threonine co-product was greater (P < 0.01) than in fish meal or corn. Threonine co-product and fish meal had comparable concentrations of metabolizable energy, and both were greater (P < 0.01) than corn.
Key points
- Threonine co-product is a rich source of crude protein and indispensable amino acids, including threonine itself.
- The concentrations of digestible crude protein and all indispensable amino acids in threonine co-product are greater than in fish meal.
- The energy content of threonine co-product is comparable to that of fish meal and greater than that of corn.
Table 1.Concentration and standardized ileal digestibility (SID) of crude protein and amino acids in threonine co-product (TCP) and fish meal (FM)
|
|
Concentration |
SID |
|||
|
Item |
TCP |
FM |
TCP |
FM |
P-value |
|
CP |
81.8 |
65.62 |
91.3 |
80.4 |
0.002 |
|
Indispensable AA, % |
|||||
|
Arg |
5.11 |
3.7 |
94.9 |
85.7 |
0.003 |
|
His |
1.83 |
1.43 |
91.8 |
82.9 |
0.005 |
|
Ile |
4.15 |
2.64 |
92.5 |
84.9 |
0.007 |
|
Leu |
7.24 |
4.37 |
92.0 |
84.3 |
0.010 |
|
Lys |
5.2 |
4.76 |
92.7 |
85.3 |
0.002 |
|
Met |
2.15 |
1.68 |
92.0 |
86.5 |
0.013 |
|
Phe |
3.45 |
2.38 |
91.2 |
82.5 |
0.010 |
|
Thr |
4.52 |
2.39 |
93.9 |
76.8 |
0.002 |
|
Trp |
1.06 |
0.63 |
95.0 |
92.5 |
0.371 |
|
Val |
5.1 |
3.02 |
90.8 |
81.7 |
0.014 |
|
Mean |
N/A |
N/A |
92.6 |
83.8 |
0.004 |
Table 2.Digestible (DE) and metabolizable (ME) energy content in threonine co-product (TCP), fish meal (FM), and corn
|
|
Ingredient |
|
||
|
Item |
TCP |
FM |
Corn |
P-value |
|
DE, kcal/kg DM |
4935a |
4699b |
3939c |
<0.01 |
|
ME, kcal/kg DM |
4084a |
4319a |
3812b |
<0.01 |
a,b,cValues within a row lacking a common superscript letter are different (P < 0.05).
This research report is based on unpublished research by F. N. Almeida, R. C. Sulabo, and H. H. Stein.