The requirement for Cu for normal metabolism by weanling pigs is 5 to 6 mg/kg, but it is common practice to include additional Cu in diets for pigs to enhance growth performance. Several modes of action for the improved growth performance have been proposed, and one proposed mode of action is the ability of Cu to alter microbial activity. The apparent total tract digestibility (ATTD) of acid hydrolyzed ether extract (AEE) is improved if Cu hydroxychloride is supplemented to high fiber diets. Therefore, an experiment was conducted to test the hypothesis that inclusion of 150 mg/kg of Cu from Cu hydroxychloride (IntelliBond CII; Micronutrients USA LLC; Indianapolis, IN) to diets fed to growing pigs improves apparent ileal digestibility (AID) and ATTD of AEE, and the AID of crude protein. The second objective was to test the hypothesis that supplementing diets with Cu hydroxychloride can reduce the concentration of microbial protein in the small intestine or in the large intestine by pigs fed a corn-soybean meal diet or a diet based on corn, soybean meal, and distillers dried grains with solubles (DDGS).
Experimental design
Twenty four barrows (initial BW: 33.3 ± 3.4 kg) were equipped with a T-cannula in the distal ileum and allotted to a 2-period switch back design with 4 diets and 6 replicate pigs per diet in each period resulting in 12 replicate pigs per diet for the 2 periods. Pigs were randomly allotted to a 2 × 2 factorial design with 2 levels of DDGS (0 or 45%) and 2 levels of supplemental Cu from Cu hydroxychloride (0 or 150 mg/kg). The initial 9 d of each period was considered an adaptation period to the experimental diets. For each period, feces were collected on d 10, 11, and 12, and ileal digesta were collected for 8 h on d 13 and 14. Samples were analyzed for gross energy, crude protein, and AEE to calculate AID and ATTD of nutrients. Samples were also analyzed for concentrations of microbial protein and volatile fatty acids.
Results
Inclusion of 45% DDGS to diets reduced (P < 0.05) the AID and ATTD of gross energy and crude protein (Table 1). Inclusion of DDGS to diets increased (P < 0.05) the concentration of microbial protein in the hindgut (Table 2). However, the total concentration of volatile fatty acids in ileal digesta and in feces from pigs fed the DDGS diets were not different from concentrations in pigs fed diets without DDGS. The AID and ATTD of crude protein were not affected by dietary Cu concentrations, but, the AID and ATTD of AEE were greater (P < 0.05) in diets supplemented with Cu hydroxychloride compared with diets without Cu hydroxychloride. There was a reduction (P < 0.05) in the concentration of microbial protein and a tendency for a reduction (P < 0.10) in the total concentration of volatile fatty acids in feces when diets were supplemented with Cu hydroxychloride.
Key points
- Inclusion of 45% DDGS in diets resulted in a reduced AID and ATTD values for gross energy and crude protein.
- Supplementation of Cu hydroxychloride to diets improved AID and ATTD values for AEE.
- Supplementation of Cu hydroxychloride to diets reduced total concentration of volatile fatty acids and concentration of microbial protein in the hindgut of pigs.
Table 1. Apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of energy and nutrients in experimental diets1
|
|
No added Cu2 |
150 mg/kg Cu2 |
|
P-value |
||||
|---|---|---|---|---|---|---|---|---|
|
Item |
- DDGS3 |
45% DDGS |
- DDGS |
45% DDGS |
SEM |
DDGS |
Cu |
DDGS × Cu |
|
AID, % |
|
|
|
|
|
|
|
|
|
Dry matter |
72.6 |
52.3 |
69.3 |
54.3 |
1.5 |
<0.001 |
0.628 |
0.039 |
|
Gross energy |
70.3 |
53.7 |
67.7 |
55.8 |
1.2 |
<0.001 |
0.818 |
0.054 |
|
AEE4 |
37.6 |
44.0 |
39.1 |
53.0 |
2.2 |
0.004 |
0.025 |
0.108 |
|
Crude protein |
77.8 |
65.6 |
78.0 |
66.2 |
1.3 |
<0.001 |
0.674 |
0.820 |
|
ATTD, % |
|
|
|
|
|
|
|
|
|
Dry matter |
82.4 |
66.9 |
79.8 |
68.6 |
1.1 |
<0.001 |
0.592 |
0.019 |
|
Gross energy |
81.0 |
66.7 |
78.0 |
69.1 |
1.1 |
<0.001 |
0.763 |
0.004 |
|
AEE |
8.2 |
19.4 |
13.8 |
34.3 |
4.1 |
<0.001 |
0.036 |
0.114 |
|
Crude protein |
78.3 |
69.2 |
76.8 |
70.4 |
1.4 |
<0.001 |
0.893 |
0.193 |
1Data are least squares means of 12 observations for treatments without DDGS and 11 observations for treatments with DDGS.
2Diets containing added Cu were fortified with 150 mg/kg of Cu as Cu hydroxychloride (IntelliBond CII; Micronutrients USA LLC; Indianapolis, IN).
3DDGS = distillers dried grains with solubles.
4AEE = acid hydrolyzed ether extract.
Table 2. Intestinal microbial protein concentrations (mg/g, DM basis) and rate of fermentation of volatile fatty acids in ileal digesta and feces of pigs fed experimental diets1
|
|
No added Cu2 |
|
150 mg/kg Cu2 |
|
P-value |
||||
|---|---|---|---|---|---|---|---|---|---|
|
Item |
- DDGS3 |
45% DDGS |
|
- DDGS |
45% DDGS |
SEM |
DDGS |
Cu |
DDGS × Cu |
|
Ileal digesta |
|
|
|
|
|
|
|
|
|
|
Microbial protein |
23.38 |
19.91 |
|
19.09 |
19.37 |
2.36 |
0.501 |
0.312 |
0.430 |
|
Volatile fatty acids (µmol/100 µmol) |
|||||||||
|
Acetate |
93.13 |
93.49 |
|
91.22 |
94.91 |
1.86 |
0.200 |
0.868 |
0.276 |
|
Propionate |
2.54 |
3.66 |
|
3.88 |
2.88 |
1.08 |
0.954 |
0.797 |
0.329 |
|
Butyrate |
3.63 |
1.59 |
|
3.93 |
1.08 |
0.69 |
<0.001 |
0.847 |
0.453 |
|
Isobutyrate |
0.53 |
0.78 |
|
0.68 |
0.74 |
0.07 |
0.019 |
0.434 |
0.139 |
|
Isovalerate |
0.16 |
0.37 |
|
0.28 |
0.27 |
0.07 |
0.170 |
0.874 |
0.123 |
|
Valerate |
0.01 |
0.11 |
|
0.01 |
0.12 |
0.07 |
0.010 |
0.885 |
0.897 |
|
Total [VFA3], µmol/g, |
7.88 |
9.05 |
|
7.88 |
7.00 |
1.10 |
0.866 |
0.229 |
0.230 |
|
DM basis |
|
|
|
|
|
|
|
|
|
|
Feces |
|
|
|
|
|
|
|
|
|
|
Microbial protein |
169.32 |
195.15 |
|
142.08 |
182.07 |
9.63 |
0.002 |
0.046 |
0.469 |
|
Volatile fatty acids (µmol/100 µmol) |
|||||||||
|
Acetate |
69.66 |
75.70 |
|
61.75 |
75.10 |
1.73 |
0.006 |
0.096 |
0.277 |
|
Propionate |
20.27 |
16.17 |
|
25.08 |
16.69 |
2.52 |
0.005 |
0.215 |
0.317 |
|
Butyrate |
1.15 |
1.09 |
|
1.25 |
1.12 |
0.10 |
0.384 |
0.523 |
0.718 |
|
Isobutyrate |
5.56 |
4.15 |
|
7.48 |
4.12 |
0.72 |
0.002 |
0.195 |
0.180 |
|
Isovalerate |
1.34 |
1.18 |
|
1.60 |
1.27 |
0.18 |
0.168 |
0.342 |
0.644 |
|
Valerate |
2.02 |
1.71 |
|
2.84 |
1.70 |
0.42 |
0.067 |
0.300 |
0.280 |
|
Total [VFA], µmol/g, |
12.36 |
10.68 |
|
10.06 |
10.42 |
0.67 |
0.333 |
0.065 |
0.140 |
|
DM basis |
|
|
|
|
|
|
|
|
|
1Data are least squares means of 12 observations for treatments without DDGS and 11 observations for treatments with DDGS.
2Diets containing added Cu were fortified with 150 mg/kg of Cu as Cu hydroxychloride (IntelliBond CII; Micronutrients USA LLC; Indianapolis, IN).
3DDGS = distillers dried grains with solubles; VFA = volatile fatty acids.