| Livestock Research for Rural Development 32 (8) 2020 | LRRD Search | LRRD Misssion | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
A total of 256 fifty-six-day-old Noi broilers were allotted to 16 experimental units with 16 chickens for each in a completely randomized design to evaluate the effects of dietary lysine supplement on apparent nutrient digestibility, carcass characteristics and small intestine villi of Noi chickens. The experimental diets consisted of the control (0.8% lysine) and the other three treatments differed by adding 0.1, 0.2, and 0.3% more lysine for each treatment. The dietary crude protein and ME was 15% and 2,900 kcal/kg of feed, respectively. The digestibility of crude protein and overall mean of amino acids were gradually improved as the level of lysine increased. Dressing percent, breast/carcass ratio and length of intestinal villi were increased with extra lysine supplementation.
Keywords: intestinal villi, protein
Lysine is one of the indispensable amino acids (AA) playing an important function in the protein synthesis process of chickens, the first AA limitation, and is used to calculate other essential AAs in chicken diets (Baker 1997; Baker et al 2002; Tesseraud et al 2011). When supplementation with dietary lysine was increased, L-lysine transport capacity by the chicken intestine was higher (Torras-Llort et al 1998) and that resulted in related improvements in apparent ileal digestibility of isoleucine, methionine, phenylalanine, valine, aspartic acid, glutamic acid, tyrosine and lysine (Selle et al 2007). Recent research findings also indicated that the increase of lysine supplementation in the diets improved meat quality (Corzo et al 2005), breast meat yield (Holsheimer and Ruesink 1993) and the breast weight (Tang et al 2007; Kidd et al 1998; Acar et al 1991). High dietary lysine levels for broiler diets have been reported to be strongly correlated with breast meat yield (Dozier et al 2009; 2010). NRC (1994) pointed out a positive effect of lysine in breast meat of broilers and Wijtten et al (2004) observed an improvement in carcass characteristics when lysine was increased with ideal protein concept rather than an increase in lysine alone. Moreover, the reports of Vaezi et al (2011) and Ojediran et al (2017) concluded that supplementation with lysine lengthened the small intestine villi and this led to improved AA digestibility.
Several recent studies on local chickens in Vietnam to assess effects of supplementary lysine (Hung and Ngu 2017; Hung et al 2018; Liu et al 2019; Hung et al 2020) showed benefits on growth and feed conversion. In the present study the objectives were to evaluate the effects of extra lysine in the diet on AA digestibility, carcass characteristics and the length of small intestine villi of Noi chickens.
A total of 256 Noi chickens at 56 days of age were allotted into 16 experimental units with 16 chickens for each. The experiment followed a completely randomized design with four treatments and four replicates. The experimental diet consisted of the control (0.8% Lys) and the other three treatments differed by adding 0.1, 0.2, and 0.3% more lysine for each treatment. The dietary crude protein (CP) and ME were 15% and 2,900 kcal/kg of feed, respectively.
For the digestibility experiment, two broilers (one male and one female) on the 76th day were collected from each replicate to evaluate AA digestibility. They were housed in individual metabolism cages with feed restricted to 80% of requirements, divided into two equal meals daily at 06:00 and 14:00. The digestibility was determined according to concentrations of the indigestible marker ferric oxide (Fe2O3) in the diets and feces. The concentration of Fe2O 3 added to the diets was 0.1% fed during days 77-81 days of age with collection of feces during the last 3 days for storae in a freezer at -20oC. The samples from the 3 days were thawed, then dried at 60 oC for further analysis.
Diets were based on yellow maize, soybean meal, rice bran, synthetic lysine and methionine, dicalcium phosphate, shell, salt, vitamin premix, and mineral premix; the proportions were determined from analysis of ingredients according to AOAC (2000) (Tables 1 and 2). Concentration of methionine, cysteine, threonine, and other essential AA were calculated to be no less than the levels of ideal AA ratios outlined by Baker (1997). The AA levels in feed and feces were determined by high-performance liquid chromatography (HPLC) (AOAC 2006).
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Table 1. Chemical composition of feed ingredients |
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|
Feedstuffs |
Chemical composition (% feed) |
|||||||
|
DM |
ME, kcal/kg |
CP |
Lys |
Met+cys |
Thr |
Ca |
P |
|
|
Yellow maize |
85.8 |
3,345 |
6.94 |
0.25 |
0.37 |
0.23 |
0.21 |
0.31 |
|
Soybean meal |
87.9 |
2,631 |
44.9 |
0.95 |
1.28 |
2.12 |
0.40 |
0.69 |
|
Rice bran |
87.8 |
2,624 |
12.0 |
0.61 |
0.22 |
1.17 |
0.38 |
1.58 |
|
DM: dry matter, ME: metabolism energy, CP: crude protein, Lys: lysine, Met+cys: methionine + cysteine; Thr: threonine; Ca: calcium; and P: phosphorus |
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|
Table 2. Experimental diets of Noi chickens from 57 to 84 days of age |
||||
|
Ingrediets (%) |
Diets |
|||
|
Ctrl |
Lys0.9 |
Lys1.0 |
Lys1.1 |
|
|
Yellow maize |
52.9 |
53.6 |
54.2 |
54.9 |
|
Soybean meal |
17.3 |
17.0 |
16.6 |
16.2 |
|
Rice bran |
25.9 |
25.4 |
25.0 |
24.6 |
|
Lysine |
0.35 |
0.45 |
0.55 |
0.66 |
|
Methionine* |
0.10 |
0.17 |
0.26 |
0.33 |
|
DCP |
1.00 |
1.00 |
1.00 |
1.00 |
|
Shell |
1.76 |
1.76 |
1.76 |
1.76 |
|
Premix** |
0.25 |
0.25 |
0.25 |
0.25 |
|
Salt |
0.400 |
0.400 |
0.400 |
0.400 |
|
Nutritional value of diets |
||||
|
ME (kcal/kg of feed) |
2,900 |
2,900 |
2,900 |
2,900 |
|
CP (%) |
15.0 |
15.0 |
15.0 |
15.0 |
|
Lysine (%) |
0.80 |
0.90 |
1.00 |
1.10 |
|
Methionine (%) |
0.57 |
0.64 |
0.72 |
0.79 |
|
Threonine (%) |
0.79 |
0.78 |
0.77 |
0.75 |
|
Tryptophan (%) |
0.26 |
0.25 |
0.25 |
0.25 |
|
Calcium (%) |
1.03 |
1.03 |
1.03 |
1.03 |
|
Phosphorus (%) |
0.80 |
0.80 |
0.80 |
0.80 |
|
DCP: dicalcium phosphate; *: ingredient source from methionine calculated both methionine and cysteine requirement; **: premix including vitamin and micro-minerals; ME: metabolism energy; CP: crude protein |
||||
For evaluating carcass characteristics, one male and one female Noi broiler at 84 days of age were selected randomly from each replicate. Feed was withdrawn 12 hours before slaughter by asphyxiation with water, then cutting the neck artery to take out all of the blood, followed by removal of all the feathers. Carcass weight was calculated as live weight prior to slaughter subtracting the weight of blood, feathers, head, legs, and evisceration of trachea, lungs, liver, heart, esophagus, full crop, proventriculus, gizzard, intestines, spleen, gall bladder, and bursa of Fabricius. Breast and thigh meat, heart, liver, gizzard, spleen, and bursa were separated and weighed and their percentages calculated relative to the carcass weight.
AA digestibility was determined from the varying concentrations of the indigestible marker present in the feces. Nutrient and AA apparent digestibility were estimated by the following equation:
|
where ND is nutrient content of the diet, Nf is nutrient content of the feces, Fe.D is Fe2O3 content of the diet, and Fe.f is Fe2O3 content of the feces.
The data were analyzed by the General Linear Model - ANOVA with Minitab software version 16.2.1.
The patterns of AA digestibility and intestinal villi length show curvilinear responses to added lysine (Figures 1 and 2).
 |
 |
| Figure 1. Effect of added lysine on AA digestibility of Noi broilers | Figure 2. Effect of added lysine on length of intestinal villi of Noi broilers |
Overall AA digestibility was improved, in which lysine 0.3% supplementation showed the highest percentage compared with the control and the complementary treatment with 0.1% added lysine (P<0.05). Supporting this study, Selle et al (2007) stated that when 11.8 g/kg of lysine was added to the broiler diet, the content of isoleucine, lysine, methionine, phenylalanine and valine AA was higher compared to the treatment of lower lysine (10 g/kg). After eating, AA released by the digestive protein digestion are absorbed through the lining of the small intestine and a portion of the AA in the diet is metabolized through the intestine before entering the bloodstream. Intestinal AA metabolism involves many processes including protein synthesis and degradation, the transit of AA, arterio-portal inequality, and first pass AA metabolism (Baracos 2004).
|
Table 3. Effects of supplementary lysine on apparent nutrient digestibility (%) |
||||||
|
Treatments |
SEM |
p |
||||
|
Control |
Lys0.1 |
Lys0.2 |
Lys0.3 |
|||
|
CP digestibility |
64.0b |
68.0a |
69.6a |
68.7a |
0.63 |
<0.001 |
|
Calcium digestibility |
47.6 |
46.4 |
49.6 |
48.9 |
1.52 |
0.486 |
|
Phosphorus digestibility |
45.5 |
47.8 |
48.7 |
47.9 |
1.98 |
0.700 |
|
Indispensable AA digestibility, % |
||||||
|
Arginine |
86.5 |
84.9 |
88.9 |
88.2 |
0.96 |
0.052 |
|
Cystine |
68.8 |
71.5 |
71.1 |
73.8 |
2.85 |
0.680 |
|
Glycine |
64.6b |
78.6a |
73.9a |
78.9a |
1.64 |
<0.001 |
|
Histidine |
82.6b |
83.8b |
86.5ab |
88.9a |
1.03 |
0.004 |
|
Isoleucine |
66.9b |
82.4a |
80.3a |
80.2a |
1.12 |
<0.001 |
|
Leucine |
78.7b |
86.4a |
84.1a |
85.4a |
0.85 |
<0.001 |
|
Lysine |
83.3b |
86.7ab |
86.9a |
87.8a |
0.88 |
0.016 |
|
Methionine |
89.7 |
89.4 |
88.4 |
90.7 |
0.78 |
0.271 |
|
Phenylalanine |
83.4 |
87.0 |
86.8 |
85.2 |
1.26 |
0.193 |
|
Threonine |
78.8 |
81.8 |
80.7 |
80.8 |
1.03 |
0.260 |
|
Valine |
62.6b |
65.3b |
78.7a |
75.5a |
1.18 |
<0.00 |
|
Dispensable AA digestibility |
||||||
|
Alanine |
63.7b |
68.3ab |
67.3ab |
72.1a |
1.66 |
0.029 |
|
Aspartic |
60.4c |
74.1b |
79.4a |
75.5ab |
1.19 |
<0.00 |
|
Glutamic |
70.4c |
80.1b |
86.9a |
83.5ab |
1.10 |
<0.001 |
|
Serine |
75.8b |
86.9a |
81.9ab |
90.8a |
2.11 |
0.002 |
|
Tyrosine |
69.5b |
75.7ab |
84.3a |
84.7a |
2.59 |
0.004 |
|
Overall AA digestibility |
73.9c |
79.8b |
81.3ab |
82.5a |
0.48 |
<0.001 |
|
a,b,c Means in the same row without common letter are different at p<0.05; AA: amino acid |
||||||
Baker and Yanming (1994) and Kidd and Fancher (2001) stated that lysine plays an important role in growth and carcass characteristics of broilers. Broilers fed the diet containing 0.3% more lysine had greater breast weight and dressing percentage compared to the control (Table 4). According to Dozier et al (2007), lysine is very important and accounts for 7% of the chicken breast protein. The study of Liu et al (2012) proved that lysine deficiency causes a reduction in protein synthesis rate but an increase in muscle protein fractional breakdown rates. It was previously stated that, dietary lysine is important for maintaining and developing skeletal muscle (Aysan and Okan 2010). Lysine supplementation in the early growth phase is beneficial because it involves the regulation of protein synthesis and increases muscle growth (Eits et al 2003; Campestrini et al 2010), and improves weight gain and feed efficiency (Si et al 2004). Li et al (2013) reported that chickens grow faster with relatively high lysine levels in the diet. Also, when adding lysine at 1.35%, 1.30% and 1.25% in Aseel chicken, it was shown that at 1.35% and 1.30%, chicken growth was improved (Hussain et al 2018).
In the present study, broilers supplemented with 0.3% extra lysine had the highest breast weight which was similar to the report of Tang et al (2007) in Arbor Acres broilers, in which diets with low, medium, and high lysine resulted in gradual increasing of breast muscle weight. The present results confirmed the report of Acar et al (1991) that breast meat yield decreased significantly as lysine content decreased from 1.05% to 0.85%. A study by Nasr and Kheiri (2012) showed that increasing the lysine level (+ 10% NRC standard) in the diet significantly increased carcass, breast, and thigh weight. On the contrary, Tang et al (2007) concluded that dressing percentage did not improve when Arbor Acres broilers received low, medium, and high levels of lysine in the diet.
|
Table 4. Carcass composition and internal orgain ratio of Noi broilers at 84 days old |
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|
Items |
Treatments |
SEM |
p |
|||
|
Control |
Lys0.1 |
Lys0.2 |
Lys0.3 |
|||
|
Live weight (g/bird) |
933 |
945 |
991 |
1,007 |
33.5 |
0.355 |
|
Carcass weight (g/bird) |
612 |
633 |
664 |
695 |
24.5 |
0.108 |
|
Breast weight (g/bird) |
73.0b |
83.8ab |
86.5ab |
93.4a |
3.59 |
0.004 |
|
Thigh weight (g/bird) |
136 |
142 |
153 |
160 |
6.32 |
0.056 |
|
Dressing |
65.5b |
66.9ab |
67.1ab |
69.0a |
0.69 |
0.014 |
|
Yield (% of carcass weight) |
||||||
|
Breast |
11.9b |
13.3a |
13.0ab |
13.4a |
0.32 |
0.014 |
|
Thigh |
22.3 |
22.5 |
23.0 |
23.1 |
0.45 |
0.539 |
|
Heart |
0.46 |
0.43 |
0.44 |
0.44 |
0.02 |
0.741 |
|
Liver |
2.01 |
1.86 |
2.58 |
2.10 |
0.25 |
0.219 |
|
Gizzard |
2.35 |
2.65 |
2.17 |
2.24 |
0.16 |
0.164 |
|
Spleen |
0.24 |
0.17 |
0.19 |
0.18 |
0.03 |
0.438 |
|
a,b,c Means in the same row without common letter are different at p<0.05 |
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The villi iin duodenum, jejunum, and ileum were longer as lysine level was increased (Table 5). This finding is in agreement with the report of Vaezi et al (2011) when supplementing lysine with evels at 1.2, 1.3, 1.4% in diets of Ross chickens resulted in increasing the height of duodenum, jejunum, and ileum villi.
|
Table 5. Effects of dietary lysine on the length (µm) of intestinal villi |
||||||
|
Items |
Treatments |
SEM |
p |
|||
|
Control |
Lys0.1 |
Lys0.2 |
Lys0.3 |
|||
|
Duodenum |
1,070b |
1,181ab |
1,193ab |
1,249a |
38.7 |
0.042 |
|
Jejunum |
931b |
891b |
1,015ab |
1,147a |
40.8 |
0.004 |
|
Ileum |
796b |
794b |
832ab |
1,057a |
58.5 |
0.023 |
|
a,b,c Means in the same row without common letter are different at p<0.05 |
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Franco et al (2006) reported an increasing crypt depth duodenum and jejunum with increased dietary lysine content of 11.4 to 12.7 g/kg in 7-day-old broilers. In another study, Nunes et al (2015) reported higher villus height to crypt depth ratio in the ileum with an increase in dietary lysine content in the diet from the diet. Similar findings were also observed by Nunes et al (2016).
This research was funded by Tra Vinh University under grant number 95/HD.HDKH-DHTV.
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