Effect of including liquid vinasse in the diet of rabbits on growth performance

The effects of liquid vinasse (LV) in the diet for growing rabbits on performance, carcass yield and intestinal morphometry were assessed. Eighty New Zealand white rabbits were used in a randomized block design with five treatments (LV inclusion at 0, 25, 50, 75 and 100 g/kg diet) and four replications. There was no effect of the treatment on final weight, daily weight gain, mortality rate and carcass yield characteristics. The daily intakes of feed, dry matter, crude protein and energy and feed conversion decreased linearly with increase in LV in the diet. Including LV affected the duodenum crypt depth and the ilium villus perimeter and height linearly and affected the duodenum villus perimeter, height and the absorption surfaces and ilium crypt depth and absorption surface quadratically. There was no effect of including LV on jejunum morphometry. Vinasse can be used to feed growing rabbits at up to 87.8 g per kilogram of diet.


Introduction
Sugarcane and ethanol production in the state of Goias, Brazil, in the 2008/2009 growing season, was 29,486,508 tons and 1,726,080 liters, respectively (Unica, 2009a,b).Twelve to 20 liters of vinasse are produced per liter of ethanol produced (Cazetta & Celligoi, 2006).Vinasse has the greatest polluting load of the effluents produced by alcohol distilleries because it presents oxygen biochemistry demand ranging from 20,000 to 30,000 mg/L vinasse (Leite, 1999).
The word vinasse is derived from the Latin vinacaeus, originally known as fermented wine.Its use has been reported in various tropical countries and in Europe as an additive or food supplement for ruminants and nonruminants.Vinasse has approximately 930 g/kg water and 17 g/kg solid compounds, dark color, sweet smell, acid pH and high salt levels.This effluent has high concentrations of potassium, calcium, magnesium, sulfur, nitrogen (Hidalgo et al., 2009) and also yeasts (403.56 mg/L) (Souza, 2007).
According to Hidalgo et al. (2009), vinasse has been used in the liquid form in animal feeding as an additive because of its probiotic properties, as a carrier in premixes, palatabilizer or promoter of sexual maturity and reproduction.Its use as an additive has generally resulted in better feed conversion and increased body weight and growth because of the presence of the organic acids, which improve nutrient use, digestion, vitamin D synthesis and vitamin C and mineral absorption, which facilitate the food metabolism.
Animal feeding accounts for almost 70% of production costs, so any alternative feedstuff that might reduce costs are useful to the producer because this increases his or her profit.
The objective of the present research was to assess the effects of including levels of vinasse (LV) in a diet for growing rabbits on the productive performance and intestinal morphometry.
Eighty male and female New Zealand white rabbits, weaned at 35 days, were used.A randomized block design with five treatments and four replications was used.The treatments consisted of LV inclusion levels (Table 1) in the commercial rabbit diet (Table 1), based on weight.The inclusion levels were 0, 25, 50, 75 and 100 g/kg, based on the weight of the commercial diet ingested daily.
Each rabbit received 70, 90, 110, 130, 140 and 150 g diet per day, in the first, second, third, fourth, fifth and sixth weeks, respectively.The percentages relative to the LV were subtracted from this quantity.The vinasse was weighed, sprayed on the diet and then mixed into it for total incorporation in the pellets.
The rabbits were housed in a masonry barn, in metal cages with drinker and feeder.The water and pelleted commercial diet, mixed with LV, were supplied freely.
The animals were weighed at the beginning and end of the experimental period, when the rabbits reached 77 days of age, to obtain weight gain and the diets were weighed daily to calculate the diet intake and feed conversion.Mortality rate was also determined.
After the final weighing, the animals were feed-deprived for 12 hours and then weighed again to obtain the weight at slaughter, which served as reference to calculate the carcass yield.After evisceration, head and paws were removed, leaving only the carcass, which was then weighed.The edible viscera were also weighed and their relative weights were calculated in relation to the slaughter weight.
Small intestine samples of approximately 3 cm were collected from the duodenum (10 m from the stomach), the jejunum (in the middle region of the small intestine) and the ileum (at 10 cm from the ileocecal junction).The samples were fixed in 10% formaldehyde for 24 hours and fragments were processed for blocking in paraffin.Serial 5 µm sections were made in each fragment and stained with hematoxylin and eosin.Thirty readings were taken per fragment for villus height, perimeter and width, crypt depth, the thickness of the mucous and muscular tunics.The absorption surface (AS) is was calculated by the formula: AS (mm 2 ) = villus height (mm) x width at 50% of the villus height (mm) The economic viability was calculated considering the average sale values of live rabbits for slaughter, slaughtered rabbit and the price of the diet consumed.The gross margin was obtained by the difference between the gross profit (live animal weight × price kg live animal or carcass weight × price kg slaughtered animal) and the diet cost (weight of diet consumed × price kg diet) (Oliveira & Lui, 2006).The price of one kilogram of live animal was R$5.00, of slaughtered animal, R$12.00, and the diet cost R$0.92kg.The rabbit prices were obtained from the Brazilian Scientific Association of Rabbit Breeders on 12/01/2012.
The results were subjected to analysis of variance and polynomial regression using software SAEG (System for Statistical Analyses, version 9.1) and α = 0.05 was adopted.

Results and Discussion
There was no effect (P<0.05) of the treatments on final weight, daily weight gain and mortality rate but the daily intakes of feed, dry matter, crude protein and energy decreased linearly (P<0.05) with increased LV levels in the diet.Reduction in diet intake without reduction in weight gain resulted in better (P<0.05)feed conversion and these values decreased linearly with increase in LV (Table 2).
The reduction in feed and nutrient intake was probably due to the high water content in LV, which improved the action of the digestive enzymes and increased the quantity of nutrients available for absorption (Luis e Silva et al., 2011).Furthermore, the organic acids in LV, including fumaric acid (Ryznar-Luty et al., 2008), improved nutrient use in the small intestine, inhibited bacterial proliferation and decreased the host-bacteria nutrient competition (Roura & Javierre, 2008), which resulted in better feed conversion.Vinasse also kept the intestinal flora in balance, preventing propagation of intestinal pathogens that could negatively influence the total production (Hidalgo et al., 2009).Similar results were reported by Maertens et al. (1994), who used vinasse obtained from beetroot in the proportion of 40 and 80 g/kg diet for 35 day-old rabbits and observed that the feed conversion was better at the highest inclusion level, and there was no effect on the other parameters.
There is little research on the use of vinasse in rabbit feeding, but according to Waliszewski et al. (1997), who used vinasse in chicken diet at the proportion of 40 and 60 g/kg, there was an improvement in the broiler performance with the dose of 40 g/kg.Similarly, Hidalgo et al. ( 2009) included 14 mL vinasse per bird/day in chicken diet, sprayed on the feed twice a day, and reported similar feed intake (3300 and 3309 g/bird) but with an extra 200 g gain in the bodyweight, better feed conversion (1.81 and 1.60) and a 2% increase in the survival rate and carcass weight.
Including LV in the diet did not affect (P<0.05) the carcass weight and yield and the edible viscera weight (Table 3).
Even with the presence of yeasts and nutrients in the vinasse such as vitamin C, minerals and organic acids, substances that beneficially alter the intestinal flora and increase nutrient digestibility and absorption, there was no effect of including LV on the carcass and edible viscera parameters.Hidalgo et al. ( 2009) assessed the supply of 5, 10 and 15 mL/d/bird in the initial, grower and finishing phases, respectively, for broiler chicks and reported that the carcass, breast and thigh yields increased along with vinasse use.According to the authors, LV can optimize nutrient use in poultry, improving the muscle disposition in the body, but this effect was not observed in the present experiment.
Including LV affected (P<0.05) the duodenum crypt depth (Table 4) and the ileum villus perimeter and height linearly (Table 5) and affected (P<0.05) the villus perimeter and height and duodenum absorption surface and ilium crypt depth and absorption surface quadratically.Including LV in the diet brought no effect to the jejunum morphometry (Table 6).
In the duodenum, the smallest villus perimeter, height and surface absorption values were obtained with 33.4,38.8 and 38.5 g LV inclusion per kg of diet, respectively, and above these levels all the parameter values increased, showing a beneficial effect of LV on the intestinal morphometry.
In the ileum, the highest villus perimeter and height values were observed with 100 g/kg LV inclusion but the highest crypt depth and surface absorption values 2 Linear effect (Ŷ = 110.88-3.2405x, r 2 = 0.38).
The better development of the intestinal mucosa tissues in rabbits fed LV may have been due to the low pH value of the vinasse and the diets with LV levels over 75 g/kg (5.98 and 5.89).Low pH favors the presence of saprophytic intestinal flora and prevents the establishment of pathogenic bacteria that might damage the intestinal mucosa by colonization and toxin production.Acid substances, such as LV, have been used as additives in animal feeding also because they increase energy and crude protein digestibility, mineral absorption and retention (Diebold & Eidelsburger, 2006).
These substances may be used as substrate by beneficial bacteria with later short-chain fatty-acid production that helps reduce the pH of the microenvironment of the brush border even further and decreases pathogen adhesion (Oliveira et al., 2008).Mannan fermentation may also increase the mucosa thickness, number of epithelial cells per crypt and the venous blood flow (Zafar et al., 2004).Liquid vinasse has a good amino acid and mineral profile (Hidalgo et al., 2009) that may have collaborated with cell proliferation and integrity of the intestinal mucosa.
Considering the gross margin resulting from the sale of live rabbits to the slaughterhouse and rabbits already slaughtered for sale, the best values were obtained with inclusion of 75 LV g/kg, which were respectively 8.79 and 7.12% greater than the values obtained with the treatment without vinasse (Table 7).Sarria & Preston (1992) used concentrated vinasse for finishing pigs and observed that its use resulted in 5% faster growth and reduced the diet price by 15%, as was also observed in the present experiment regarding the diet cost.

Conclusions
In natura liquid vinasse can be used to feed growing rabbits at 87.8 g per kilogram of diet.

Table 1 -
Nutritional levels of the commercial diet supplemented with increasing levels of liquid vinasse (LV) and LV based on dry matter

Table 2 -
Productive performance of rabbits at 77 days of age fed diets containing levels of vinasse

Table 3 -
Carcass weight and yield for edible viscera from 77-day-old rabbits fed diets containing vinasse CV -coefficient of variation.

Table 4 -
Duodenum morphometry of 77-day-old rabbits fed diets containing levels of vinasse

Table 5 -
Jejunum morphometry of 77-day-old rabbits fed diets containing levels of vinasse

Table 6 -
Ileum morphometry of 77-day-old rabbits fed diets containing levels of vinasse

Table 7 -
Economic viability of the productive performance of growing rabbits fed diets containing vinasse