in the diet and live weight gain
in the diet and feed conversion
| Livestock Research for Rural Development 32 (4) 2020 | LRRD Search | LRRD Misssion | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
Sixteen Landrace × Large White pigs (8 castrated males and 8 females) of 52.9±4.62 kg live weight were fed in individual pens for 38 days on basal diets of broken rice-soybean meal supplemented with four levels (0, 5, 10 and 15% as DM) of molasses-yeast-powder (MYP) (the dried, yeast-rich residue from ethanol production by fermentation-distillation of molasses). The MYP contained (DM basis) 37% protein, 14.7% β-glucan and 31% mannan-oligosaccharides. The design was a randomized block of four treatments each with four replicates. Blood samples were collected on the last day of the trial and evaluated for hematological and immunological parameters. Carcass characteristics, intestinal histomorphology and meat quality were measured postmortem.
Growth rate and feed conversion were improved by 12 and 9%, respectively when 5% of MYP was added to the diets. For both traits, the dose-response curves were curvilinear, showing no further improvements in live weight gain and feed conversion beyond the 5% level of addition of the MYP. Supplementation with MYP appeared to have no effect on the hematology, intestinal histomorphology, immunological response, carcass traits and meat quality of the pigs.
Keywords: β-glucan, fermentation, mannan-oligosaccharides, prebiotic, yeast
Farmers in Thailand are looking for natural alternatives to antibiotics, Yeast offers several options: from the presence in the cell wall of mannan-oligosaccharides and β-glucans acting as a prebiotic (Kogan and Kocher 2007); and as a live culture, or symbiotic (Broadway et al 2015). The complex structures of the yeast cell wall cannot be digested by enzymes in the stomach and small intestine of monogastric animals, but it is a source of nutrients for communities of intestinal lactic acid bacteria such as Bifidobacteria and Lactobacilli. It is well established that β-glucans occur naturally in fungi, bacteria, cereals, seaweeds and yeast (Soltanian et al 2009).
β-glucan is a polysaccharide compound that has been shown to enhance the digestive system and stimulate the activity of immune cells to combat foreign microorganisms (Li et al 2005; Vetvicka et al 2014). In experiments with pigs it was reported that that β-glucan reduces diarrhea (Chethan et al 2017), is a prophylactic against swine fever (Wang et al 2008b), enhances the immune response (Jin et al 2018) and improuves performance (Li et al 2006).
Mannan-oligosaccharides (MOS) are compounds that consist of linked molecules of D-mannose. They are highly stable, not digested by acids and alkalis, but are digested by mannanase enzymes in bacteria and fungi (Songsiriritthigul et al 2010). Dietary supplementation with MOS was reported to decrease Salmonella spp. and Escherichia coli and to increase lactobacillus spp and height of intestinal in broilers (Zhang et al 2005; Oliveira et al 2008).
Molasses yeast powder (MYP) is the dried residue after fermentation of molasses with yeast (Saccharomyces cerevisiae) and subsequent distillation to produce ethanol. Analysis of MYP in our laboratory showed that it contained (DM basis) 37% protein, 14.7% β-glucan and 31% mannan-oligosaccharides (MOS).
Because of its high content of protein, β-glucan and MOS, MYP was chosen as a logical supplement to be added to diets of grower-finishing pigs.
The experiment was done at the swine farm on the campus of the Rajamangala University of Technology Isan (RMUTI), Sakon Nakhon Campus. Sixteen Landrace × Large White pigs (8 castrated males and 8 females) of 52.9±4.62 kg live weight were housed in individual pens for an experimental period of 38 days. They were managed according to the procedures in the Guide for the Care and Use of Laboratory Animals (U1-01493-2558). The 4 treatments replicated 4 times in a random block design were levels of 0, 5, 10 and 15% of MYP added to a basal diet of broken rice-soybean meal (Table 1) fed ad libitum. The composition of diet ingredients was determined according to AOAC (2012) procedures. The MYP contained (DM basis) 37% protein, 14.7% β-glucan and 31% mannan-oligosaccharides (MOS).
|
Table 1. The chemical composition of the basal diet |
|
|
% air-dry |
|
|
Broken rice |
59.4 |
|
Soybean meal (44% CP) |
24.6 |
|
Fish meal |
8.00 |
|
Tallow |
2.21 |
|
Sugar |
3.00 |
|
Dicalcium phosphate |
1.80 |
|
L-Lysine |
0.19 |
|
DL-Methionine |
0.02 |
|
Salt |
0.35 |
|
Premix |
0.50 |
|
Chemical composition |
|
|
Moisture (%) |
13.0 |
|
Crude protein (%) |
20.0 |
|
Metabolizable energy (kcal/kg DM) |
3377 |
|
Ether extract (%) |
5.89 |
|
Crude fiber (%) |
2.68 |
|
Calcium (%) |
1.06 |
|
Phosphorus (%) |
0.60 |
Feed intake was recorded daily. The pigs were weighed at the start and on the last day of the trial.
Blood samples were gathered from the jugular vein, transferred test tubes containing EDTA, held in an ice box, and transported to a commercial laboratory, where they were analyzed in an automated process (Sysmex XT-2000iVTM) to quantify red blood cells (RBC), white blood cell (WBC), hemoglobin (Hb), hematocrit (Hct), mean corpuscular volume (MCV), mean cell hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), platelet count (PC) and neutrophil (Neu). The values of immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) were determined using the BN Prospec Nephelometer Analyzer. The values of IgG and IgM were used to calculate IgG: IgM ratio.
The intestinal epithelium was taken from the ileum, washed with a physiological solution (0.9%) and set in 10% buffered formalin. The samples were then put first in individual histological cassettes, embedded with paraffin, cut by a semi-automatic rotation microtome (Leica RM2245, Leica Biosystems), and lastly stained with hematoxylin and eosin. The microtome sample was captured by digital light microscope (40X) to determine the height of the villi (VH), the depth of the crypt (CD), and the proportion of the VH:CD using ImagePro plus version 3.1 (Media cybernatics).
At the end of the experiment, all pigs were fasted for 12 h before slaughter, and then transported to the local abattoir at Sakon Nakhon province, then slaughtered following the technique defined by Jaturasitha (2007). After slaughter, hot carcass weights, carcass length, back-fat thickness, and loin size were recorded. The dressing percentage and lean ratio were measured. Dressing percentage (DP) was calculated as carcass weight ÷ live weight) × 100. The length of the carcass was measured from the first rib cranial edge to the pubic aitch using a metal tape. Back-fat thickness was evaluated in the first rib, last rib, and last lumbar vertebra. Loin-eye area between the 10th and 11th rib was measured using a weighing paper method.
The longissimus dorsi (LD) from the 6th to the 15 th rib muscles from the left side of carcass was collected, and transferred under cooling to the RMUTI Department of Food Science and Technology, where the meat was stored at 4 °C for 24 h until assessed for meat quality. The meat was then cut into 2.54 cm thickness. A pH meter (WTW pH340, Germany) equipped with a penetrating glass electrode was used to measure pH at 45 min and 24 h postmortem. Lightness (L*), redness (a*), and yellowness (b*) color values of meat surface was measured in triplicate using CR-300 Chroma Meter (Minolta Co. Ltd., Osaka, Japan) which was calibrated against a standard white tile. Water-holding capability (WHC) was calculated from the sample weight change before and after chilling at 4 °C for 24 h. The proximate composition including moisture, crude protein, and fat content was analyzed according to AOAC (2012). The meat was vacuum-packed and boiled at 80°C for 15 min before analyzing the shear force by TA-XT.plus Texture Analyzer (Stable Micro System Ltd., Surry, UK).
Data from growth performance, hematology, histomorphology, carcass, and meat quality was subjected to analysis of variance to evaluate the effects of MYP treatment using GLM procedure (SAS 2003). Sources of variation were treatments and error. Dose-response curves for live weight gain and feed conversion were derived by fitting polynomial equations to the data (Y=live weight gain/feed conversion; X=percent MYP in the diet).
Feed intake was not affected by supplementation with MYP (Table 2). There were tendencies for improvements in weight gain (p=0.10) and feed conversion (p=0.066) as the proportion of MYP in the diet was increased.
|
Table 2. Mean values for performance traits of the pigs over the 38-day experiment |
||||||
|
% MYP in the diet |
SEM |
p |
||||
|
0 |
5 |
10 |
15 |
|||
|
Live weight, kg |
||||||
|
Initial |
53.0 |
52.1 |
50.8 |
55.6 |
7.41 |
0.17 |
|
Final |
84.8 |
87.8 |
85.3 |
90.8 |
1.29 |
0.55 |
|
Daily gain |
0.84 |
0.94 |
0.91 |
0.92 |
0.031 |
0.10 |
|
Feed intake, kg/d |
2.50 |
2.54 |
2.42 |
2.50 |
0.026 |
0.59 |
|
Feed conversion# |
3.00a |
2.71b |
2.67b |
2.71b |
0.066 |
0.01 |
Supplementation with MYP appeared to have no effect on the hematology and immunological response of the pigs (Tables 3 and 4).
|
Table 3. Mean values for hematology and immunological response of grower-finishing pigs supplemented with MYP |
|||||||
|
Reference# |
% MYP in the diet |
SEM |
p |
||||
|
0 |
5 |
10 |
15 |
||||
|
RBC, ×106/µL |
5.00-8.00 |
2.35b |
2.45ab |
2.57a |
2.57a |
0.068 |
0.023 |
|
WBC, ×103/µL |
11.0-22.0 |
13.7 |
13.9 |
13.6 |
13.9 |
0.41 |
0.92 |
|
Hb, g/dL |
10.0-16.0 |
13.1 |
13.3 |
13.1 |
13.1 |
0.13 |
0.80 |
|
Hct, % |
32.0-50.0 |
37.0b |
38.5b |
40.3a |
40.6a |
0.51 |
<0.001 |
|
MCV, fL |
50.0-68.0 |
78.7 |
78.8 |
78.4 |
78.4 |
1.66 |
0.87 |
|
MCH, pg |
17.0-21.0 |
15.7 |
15.8 |
15.7 |
15.7 |
0.31 |
0.87 |
|
MCHC, g/dL |
30.0-34.0 |
35.4a |
34.4a |
32.6b |
32.5b |
0.50 |
<0.001 |
|
RDW, % |
NR |
14.6 |
14.6 |
14.7 |
14.7 |
0.32 |
0.83 |
|
PC, ×103/µL |
320-520 |
675 |
705 |
593 |
718 |
64.3 |
0.96 |
|
Neu, % |
22.5-78.5 |
73.3 |
74.0 |
74.8 |
72.5 |
1.74 |
0.849 |
|
Lym, % |
32.2-97.3 |
26.8 |
24.5 |
27.3 |
27.3 |
1.60 |
0.56 |
|
IgA, mg/dL |
NR |
99.8 |
103 |
104 |
106 |
2.38 |
0.12 |
|
IgG, mg/dL |
NR |
747b |
747b |
771a |
780a |
6.01 |
<0.001 |
|
IgM, mg/dL |
NR |
66.0 |
66.0 |
66.3 |
62.8 |
2.84 |
0.47 |
|
IgG:IgM ratio |
NR |
11.4 |
11.4 |
11.7 |
12.5 |
0.48 |
0.14 |
|
# Reference values obtained from Radostits et al (2010). RBC, red blood cell; WBC, white blood cell; Hb, hemoglobin; Hct, hematocrit; MCV, mean corpuscular volume; MCH, mean cell hemoglobin; MCHC, mean corpuscular hemoglobin concentration; RDW, red cell distribution width; PC, platelet count; Neu, neutrophil; IgG, immunoglobulin G; IgA, immunoglobulin A; IgM, immunoglobulin M; NR, No report; ab Values in the same row with superscripts differ at p<0.05 |
|||||||
|
Table 4. Mean values for intestinal histomorphology in grower-finishing pigs supplemented with MYP |
||||||
|
% MYP in the diet |
SEM |
p |
||||
|
0 |
5 |
10 |
15 |
|||
|
Villus height (VH), µm |
525 |
555 |
585 |
601 |
34.1 |
0.10 |
|
Cryptal depth (CD), µm |
133 |
142 |
140 |
140 |
2.64 |
0.11 |
|
VH:CD ratio |
3.95 |
3.91 |
3.64 |
4.29 |
0.24 |
0.49 |
Dietary MYP supplementation had no influence on carcass parameters (Table 5) nor on quality of the meat (Table 6).
|
Table 5. Mean values for carcass traits of grower-finishing pigs supplemented with MYP |
||||||||
|
% MYP in the diet |
SEM |
p |
||||||
|
0 |
5 |
10 |
15 |
|||||
|
Slaughter weight, kg |
525 |
555 |
585 |
601 |
34.1 |
0.10 |
||
|
Hot carcass weight, kg |
133 |
142 |
140 |
140 |
2.64 |
0.11 |
||
|
Carcass percentage, kg |
3.95 |
3.91 |
3.64 |
4.29 |
0.24 |
0.49 |
||
|
Cutting percentage, % |
90.6 |
89.3 |
88.3 |
92.0 |
2.02 |
0.74 |
||
|
Carcass length, cm |
70.4 |
72.1 |
68.9 |
69.8 |
1.67 |
0.53 |
||
|
Back fat thickness, cm |
77.6 |
80.7 |
78.3 |
75.9 |
1.95 |
0.40 |
||
|
Loin eye area, cm2 |
32.6 |
32.5 |
28.6 |
33.1 |
1.47 |
0.73 |
||
|
ab Values in the same row with different superscripts differ at p<0.05 |
||||||||
|
Table 6. Mean values for meat quality of longissimus dorsi muscle in grower-finishing pigs supplemented with MYP |
||||||||
|
% MYP in the diet |
||||||||
|
0 |
5 |
10 |
15 |
SEM |
p |
|||
|
Meat pH |
||||||||
|
pH 45 min. |
6.20 |
6.18 |
6.19 |
6.03 |
0.17 |
0.69 |
||
|
pH 24 h |
5.91 |
5.61 |
6.25 |
6.24 |
0.14 |
0.21 |
||
|
Meat color |
||||||||
|
Lightness (L*) |
53.35 |
54.5 |
54.6 |
51.8 |
0.15 |
0.54 |
||
|
Redness (a*) |
3.51bc |
4.5a |
3.15c |
3.86ab |
0.24 |
0.82 |
||
|
Yellowness (b*) |
14.6 |
15.4 |
15.1 |
14.6 |
0.29 |
0.61 |
||
|
Drip loss, % |
10.7 |
11.6 |
11.8 |
11.6 |
0.94 |
0.51 |
||
|
Shear values |
||||||||
|
Shear force (kgf) |
2.40 |
2.36 |
2.49 |
2.52 |
0.16 |
0.51 |
||
|
Work of shear (kgf.s) |
21.6 |
21.2 |
21.7 |
23.7 |
1.28 |
0.35 |
||
|
Chemical composition |
||||||||
|
Moisture, % |
72.8 |
72.5 |
73.8 |
73.2 |
0.82 |
0.56 |
||
|
Protein, % |
19.7 |
18.8 |
19.7 |
20.1 |
0.66 |
0.51 |
||
|
Fat, % |
3.98 |
4.36 |
3.98 |
4.16 |
0.14 |
0.80 |
||
|
ab Values in the same row with different superscripts differ at p<0.05 |
||||||||
A more detailed analysis of the growth performance data revealed that the dose-response curves to MYP for growth rate and feed conversion were curvilinear with the optimum responses manifested at the 5% level of supplementation with MYP (Figures 1 and 2).
|
|
|
Figure 1.
Curvilinear relationship between % of MYP in the diet and live weight gain |
Figure 2.
Curvilinear relationship between % of MYP in the diet and feed conversion |
A similar curvilinear growth response to a byproduct of yeast fermentation was observed in growing goats (Thuy Hang et al 2018) when their basal diet of cassava foliage was supplemented with brewers’ grains (the residue from yeast fermentation of barley grain to produce beer). The optimum level of the supplement was 4% with a reduced degree of response when the supplement was fed at higher levels.
Increases in N retention of 13 and 18% respectively, were reported in growing pigs in Laos when their diet of ensiled banana pseudo-stem and taro foliage was supplemented with 4% (as DM) of either brewers’ grains, or the residues from rice wine production (Sivilai and Preston 2017). In an experiment with sows, these same byproducts of yeast fermentation, fed at 4% of the diet, supported improvements in feed conversion (total feed in pregnancy-lactation/weight of piglets weaned) of 27 and 67%, respectively (Sivilai et al 2018).
The differences between our experiment and those in Laos were: (i) the carbohydrate source used in the fermentation: barley and rice grains in Laos compared with molasses in our experiment; and the /productive stage of the pigs - early growth and pregnancy-lactation in the experiments reported by Sivilai et al (2017, 2018) compared with the final stage of growth (56-85 kg live weight) in our experiment. A greater response to a supplement thought to act as a prebiotic was perhaps to be expected under the conditions of the experiments reported by Sivilai et al al (2017, 2018). The fact that there were no apparent effects of MYP supplementation on the hematology and immunological response of the pigs in our experiment (Tables 3 and 4) lends support to this idea.
The author would like to thank the Department of Animal Science, Natural Resources Faculty, Isan Technology University of Rajamangala, SakonNakhon Campus for their administrative and technical support. Thank you to the National Research Council of Thailand (NRCT) for financial support (project no. 271433).
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Received 20 February 2020; Accepted 14 March 2020; Published 1 April 2020