Introduction
Feed comprises 70-75% of the total costs in quail production, deserving the attention of nutritionists in search of cost reduction. However, using alternative products should consider their abundance and geographical location (Braga et al., 2005). Price and quality are also essential when choosing a byproduct. Tests to determine the best inclusion level in the diet are also necessary, along with measuring performance and egg quality (Sakamoto et al., 2006).
Liquid vinasse (LV) is the final residue of ethyl alcohol production. It is a distillery effluent with high polluting capacity and high fertilizer value. Between 12 and 20 L of vinasse are produced per liter of ethanol (Cazetta and Celligoi, 2006).
Inclusion of LV in animal feed may increase productive performance because it contains organic acids and B-complex vitamins that improve the use of nutrients and keep the intestinal flora in balance. LV inclusion increased viability, body weight, and development of the reproductive system (oviducts and follicles) in replacement pullets. The literature has described better uniformity of the flock with the use of LV at a rate of 14 mL/bird/d for layers in the rearing period, and an increase in egg production in laying hens supplemented with 15 mL LV/d (Hidalgo et al., 2009; Hidalgo et al., 2011).
The present study evaluated productive performance and egg quality of laying Japanese quails fed commercial feed with increasing levels of LV as well as to evaluate the economic viability of using this byproduct in egg production.
Materials and methods
Ethical considerations
This study was approved by the ethics committee for Animal Experiments of Universidade de Rio Verde (Brazil) protocol 0001-11, following guidelines established by Brazilian law 11.794 (October 08, 2008) and the Brazilian National Council for Control of Animal Experimentation.
Location, animals, and treatments
The experiment was performed at Universidade de Rio Verde (Goiás, Brazil). One-hundred-sixty 150 d-old female laying Japanese quail, weighing 188.96 ± 4.47 g, with 93.37 ± 1.46% initial egg production rate were used. The experimental period consisted of 84 d divided into three cycles of 28 d each and 4 additional days to collect the eggs and perform bromatological analysis. Animals were randomly allotted to five treatments with four replicates and eight birds per experimental group. The treatments consisted of increasing inclusion levels of LV in commercial sorghum-based feed (SBF) for laying quails (COMIGO, Rio Verde, GO, Brazil). Feed composition is presented in Table 1.
Vinasse [pH 4.0; 1,029 Kcal/Kg of gross energy (GE); 0.58% calcium (Ca); 0.01% total phosphorus (P); 2.73% crude protein (CP) on a dry matter (DM) basis of 3.17%] was donated by an alcohol-producing plant. The levels of LV in the feed were 0, 2.5, 5, 7.5, and 10%. The nutritional composition of the feed supplemented with LV was determined in the laboratory (Table 2).
Because of its potential use as a source of organic acids, LV was included as a feed additive. Since LV composition is mostly water, high levels were tested. To prepare the diets, the feed was weighed, the percentage of LV was calculated for each treatment, and LV was incorporated into the feed using a mixer. The diets were weekly prepared and stored in plastic buckets to promote its conservation and avoid deterioration.
The quails were housed in 25 ´ 15 ´ 33 cm (length´ height ´ width) metal cages with a tray for egg collection and feeding and drinking troughs. Each drinking trough supplied four cages. Water and feed were available ad libitum, with feed offered twice daily, at 8 am and 5 pm, times when the eggs were counted and collected. The birds were submitted to a lighting program since the 40th d of age.
At first, 14 h of light were provided daily. The light duration increased weekly in increments of 30 min until quails were exposed to 17 h of light/d, and this level was maintained until the end of the experiment.
Evaluated parameters
Productive performance included the evaluation of laying rate, egg mass, daily feed intake [as DM and fresh matter (FM)], feed conversion ratio/Kg and per dozen eggs as FM and DM, and the daily intake of CP, GE, Ca, and P, as DM.
Of the eggs produced in the last 3 d of the experimental period, two were used to determine egg weight, morphometry (height and diameter), weight of yolk and albumen, and weight and thickness of the eggshell. The height and diameter of the yolk and dense albumen were measured with a manual caliper and the other eggs were used to determine specific weight. Based on the resulting values, Haugh units, yolk, albumen, and eggshell percentages were determined. Haugh units were obtained using the formula:
HU = 100 × log (H − 1.7 × P0.37 + 7.6)
Where:
H: Is albumen height (mm).
P: Is the whole egg weight (g).
The birds received treatment during four more days so that their eggs could be collected for bromatological analysis, which was performed for 25 eggs from each replicate using the method of Silva and Queiroz (2002) to determine DM, CP, ether extract (EE), and MM content.
Feed costs were calculated by multiplying feed conversion rate (Kg DM/Kg and Kg DM/dozen) by the price of 1 Kg feed (2.79 USD).
Statistical analysis
The results were subjected to analysis of variance and polynomial regression analysis, and the F-test was used to determine significance of the effects. The analyses were performed using SISVAR software version 5.3 (DEX/UFLA, Lavras, MG, BR), and the significance level was set at 5%.
Results
The laying rate, egg mass, daily feed intake, and feed conversion ratio in Kg/Kg and in Kg FM/dozen were not influenced by LV levels (p>0.05). However, daily intake of DM p<0.003), CP (p<0.03), GE (p<0.03), Ca (p<0.001), and P (p<0.01), and the feed conversion ratio (Kg DM/dozen) decreased linearly as LV increased (Table 3).
The LV levels had no influence (p>0.05) on egg weight, Haugh units, weight and percentage of yolk and albumen, or eggshell percentage and thickness. However, specific weight (p<0.003) and eggshell weight (p<0.4) increased linearly with the level of LV in the diet (Table 4).
There was no effect (p>0.05) of treatment on CP content (as FM) or on MM content (as DM and FM) of the eggs. However, DM content decreased (p<0.004) and CP content (as DM) increased (p<0.014) linearly with LV. The EE content of the eggs, both as DM (p<0.014), and as FM (p<0.001), showed a quadratic effect, with the lowest EE content associated with the 10% level of LV (Table 5).
There was no difference (p>0.05) in the price of a Kg of eggs, but the price of a dozen eggs decreased (p<0.003) linearly with the inclusion of LV (Table 6).
CV: Coefficient of variation. DM: Dry matter. GE: Gross energy. FM: Fresh matter. 1 Linear effect (Ŷ = 28.78 − 0.494x; r2 = 0.84). 2 Linear effect (Ŷ = 5.93 − 0.09x; r2 = 0.77). 3 Linear effect (Ŷ = 99.54 − 1.65x; r2 = 0.78). 4 Linear effect (Ŷ = 1.28 − 0.04x; r2 = 0.96). 5 Linear effect (Ŷ = 0.19 − 0.004x; r2 = 0.79). 6 Linear effect (Ŷ = 0.345 − 0.0059x; r2 = 084).
CV: Coefficient of variation. 1 Linear effect (Ŷ = 1.073 + 0.583x; r2 = 0.84). 2 Linear effect (Ŷ = 1.88 + 0.020x; r2 = 0.57).
DM: Dry matter; EE: Ether extract; FM: Fresh matter; CP: Crude protein; MM: Mineral matter; CV: Coefficient of variation. 1 Linear effect (Ŷ = 26.65 − 0.167x; r2 = 0.59). 2 Quadratic effect (Ŷ = 33.59 + 0.945x − 0.115x 2; R2 = 0.74). 3 Quadratic effect (Ŷ = 8.79 + 0.320x − 0.042x 2; R2 = 0.90). 4 Linear effect (Ŷ = 41.78 + 0.1757x; r2 = 0.63).
Discussion
Inclusion of LV was expected to improve the productive performance because it is an acidifying product with probiotic properties. Although the intake of DM, CP, GE, Ca, and P decreased as LV increased, the feed conversion ratio (Kg DM/dozen) was the only affected variable. It suggests dietary nutrients were used more efficiently as a result of supplementation with LV.
Similarly, Swiatkiewicz et al. (2010) found that laying hens supplemented with prebiotics and organic acids showed no change in egg mass compared with hens fed non-supplemented diets. However, Bahnas (2009) reported an increase in the laying rate of Japanese quail supplemented with 0.05% malic acid.
Dahiya et al. (2016) concluded that laying hens supplemented with salts of organic acids had higher hen-d egg production. Hidalgo (2009) reported an increase of up to 16% in egg production when birds ingested LV with the feed. Dietary supplementation with organic acids for laying hens also increased egg mass (Soltan, 2008).
The DM content of LV is very low (3 to 4%). Thus, the higher the level of LV added, the lower the DM of the diet, accounting for a linear decrease in daily DM intake while daily feed intake remained unaltered. Gallo et al. (1986) also observed a decrease in feed intake of birds receiving LV in the drinking water.
Ribeiro et al. (2010) added organic acids associated with mannan oligosaccharides to the diet of laying hens and observed a decrease in feed intake. According to the authors, this result was caused by inhibition of microbial development and the influence of organic acids on nutrient availability. Bahnas (2009) provided 0.05% malic acid to Japanese quail and observed a decrease in feed intake, together with an increase in egg mass, indicating the economic efficiency of this practice.
The reduction in nutrient and energy intake did not affect feed conversion values, indicating dietary nutrient usage was optimized, possibly because of the presence of organic acids in the LV. Evaluating the effect of organic acids on productive performance of laying hens, Lala et al. (2016) observed a decline in feed conversion (g/g) when humic acid was added to the diet of laying hens, compared to the control group.
Acidifying substances also act as antibiotics, and supplementing birds with these substances is a strategy for improving animal performance. However, because of the differences in the modes of action, environmental conditions, used doses, and the conditions evaluated for this supplementation, conflicting results have been reported regarding response to the use of these substances (Viola and Vieira, 2007). These differences could explain the small effect of LV on quail performance in the present experiment. The animals did not face health challenges, considering the clean and comfortable environment in which they were housed. According to Ricke (2003), the antibacterial mechanism of acidifiers is not completely understood and variations may occur depending on the organism and the environment.
Acidifying substances may also positively influence egg weight (Soltan, 2008). On the other hand, Kaya et al. (2014) found no difference in shape index, shell thickness and weight, yolk and albumen index and Haugh unit in eggs laid by hens receiving a mixture of organic acids.
The yolk contains the greatest concentration of nutrients in the egg, so that increasing its size is desirable. Similarly to the present results, Soltan (2008) observed that supplementing the diets of laying hens with organic acids produced eggs with similar yolk weights. The characteristics of the albumen were unaltered, but adding organic acids to the diet of laying hens increased the albumen percentage and simultaneously decreased the percentage of yolk in the egg (Rahman et al., 2008).
Specific weight is an estimate of eggshell density. It is related to the resistance of the eggshell, and according to Güçlü et al. (2008), an increase in eggshell density indicates an improvement in eggshell quality. Integrity and resistance of the eggshell are essential for maintaining the nutritional and microbiological properties of the egg (Murata et al., 2009). Given that Ca is the main component of eggshell, the quality of this structure may be compromised when the diet provides low levels of Ca (Paz et al, 2009).
Considering a mean feed intake of 32 g/bird/d, Ca intake should be 0.89 (NRC, 1994), 0.95 (Silva e Costa, 2009), or 0.77 g/bird/d (Rostagno et al., 2011) for good eggshell quality. In this study, even the lowest level of Ca intake (0.95 g/bird/d) met the requirement of the bird. Thus, the best eggshell quality obtained by including 10% LV could be the result of the acidification of the diet and the greater Ca absorption in the intestines that results from acidification, as Suiryanrayna et al. (2012) reported. A similar effect was also observed by Soltan (2008), who supplemented the diets of laying hens with organic acids and observed increased eggshell thickness and weight, although the change in the latter was not significant.
Reduction in the DM content of eggs is not desirable in the egg industry. The DM content of the eggs remained relatively stable (approximately 26%) up to 7.5% LV inclusion. This reduction could be associated with lower daily DM intake, given that bird nutrition can influence egg quality. The values we obtained are similar to those reported by Genchev (2012), who evaluated the chemical composition of eggs from two lines of Japanese quail and found DM values of 26.72 and 26.06%.
The highest EE values were obtained at levels of 4.16 and 3.76% LV, and the lowest at 10% LV in the diet. Although jejunum is the main site for fat absorption (Krogdahl, 1985), the duodenal region may have been acidified with 10% LV supplementation. Moreover, the optimum pH for pancreatic lipase activity is close to 8, and these enzymes are inactivated at pH lower than 6 because low pH precipitates biliary acids, interfering with fat digestion and absorption (Ros, 2000) and consequently with its deposition in eggs.
The linear increase observed in CP content associated with LV is desirable because biological value of egg protein is high. As previously mentioned, duodenum acidification may improve the activity of intestinal proteolytic enzymes, whose optimum pH is between 3.5 and 4 (Goldberg et al., 1969). In addition, duodenal acidification can stimulate secretion of pancreatic juice, trypsin, and chymotrypsin (Thaela et al., 1998), improving protein digestion and absorption so that protein can be deposited in the egg. The linear increase in CP in this experiment could be explained by amino acid supplementation (Shafer et al., 1998) owing to their increased availability and digestibility offered by organic acids (Partanem and Mroz, 1999).
Although the effects of LV on egg production costs have not been thoroughly described in the literature, economic benefits of using LV in other animal species have been reported. Oliveira et al. (2013) found that the gross margin was greater when LV is added to the diet of rabbits.