Dietary strategy with the use of coproducts from the ethanol plant associated with the inclusion of urea for finishing confined sheepRESUMO
O objetivo deste estudo foi avaliar o uso de grãos secos de destilação com solúveis (DDGS) associados à inclusão de níveis crescentes de ureia (0,0%, 0,5%, 1,0%, 1,5%) na dieta de ovinos confinados sobre as características de consumo e digestibilidade dos nutrientes. Foram utilizados oito ovinos Santa Inês, machos, castrados, com peso corporal inicial de 40kg, com idade de 12 meses, distribuídos em delineamento em quadrado latino duplo 4x4. O consumo de matéria seca, matéria orgânica, fibra insolúvel em detergente neutro, carboidrato não fibroso e nutrientes digestíveis totais não foi afetado com a adição de ureia. A adição de ureia promoveu efeito quadrático (P<0,05) no consumo de proteína e tendeu a efeito quadrático (P<0,10) no consumo de extrato etéreo. A digestibilidade da matéria orgânica e da proteína bruta não foi alterada pela adição de ureia. Entretanto, a digestibilidade da fibra em detergente neutro aumentou linearmente (P<0,05). Em contrapartida, a digestibilidade do extrato etéreo foi reduzida (P<0,05), e a digestibilidade dos carboidratos não fibrosos tendeu (P<0,10) a diminuir com a adição de ureia. Conclui-se que não há necessidade de inclusão de ureia em dietas que utilizem 30% de DDGS na MS de cordeiros confinados.
Palavras-chave:
consumo; coproduto; digestibilidade aparente; ruminante; proteína
Keywords:
intake; co-product; apparent digestibility; ruminant; protein
Palavras-chave:
consumo; coproduto; digestibilidade aparente; ruminante; proteína
Keywords:
intake; co-product; apparent digestibility; ruminant; protein
Palavras-chave:
consumo; coproduto; digestibilidade aparente; ruminante; proteína
Feeding strategies in ruminant production systems play a pivotal role in enhancing performance in the production chain, thereby bolstering the competitiveness of Brazilian agribusiness. In recent years, Brazil has witnessed a surge in the demand for foreign meat, a trend that could potentially revitalize the sector and attract substantial investments. However, this increased demand for meat from the global market has also led to a corresponding rise in the demand for grains (such as soy and corn), thereby exerting pressure on commodity prices and escalating production costs.
In this way, food strategies in meat production systems, such as intensification, aim to maintain the sector in the face of increasing production costs. An emerging activity in the country is the production of ethanol from corn grains. In the 2022/23 harvest, 4.54 billion liters of corn ethanol were estimated, an increase of 30.7% compared to the previous harvest (Boletim…, 2022). These plants positioned themselves as buyers of a large volume of corn grain in competition with livestock farming.
At first, the livestock sector does not see these plants as a commercial ally but rather as new, very aggressive, and growing competition. However, the use of corn grain in ethanol-producing plants generates a co-product called dry or wet distillers’ grain with solubles (DDGS or WDGS) that can be used in animal nutrition. The production yield is for every 1000 liters of corn ethanol produced, generating an average of 950kg of DDGS.
The chemical composition of DDGS is significantly more nutritious than that of corn, with crude protein (CP) contents ranging from 22 to 43%, neutral detergent insoluble fiber (NDF) from 30 to 44%, ether extract (EE) from 6 to 11%, and phosphorus from 0.6 to 0.8% (Valadares Filho et al., 2016). The recommended inclusion of DDGS in the diet of confined ruminants is up to 30% in dry matter. This inclusion has been found to have a positive impact on food intake, nutrient digestibility, and prevention of rumen metabolic disorders (Klopfenstein et al., 2008).
Replacing corn with dried distiller grains (DDG) in feedlot diets helps decrease the risk of ruminal acidosis and increases dry matter intake in low-forage diets. Considering that the inclusion of DDG led to an increase in neutral detergent fiber and a decrease in starch content in diets, replacing corn grain promotes healthier conditions in the rumen (Rosa and Silva et al., 2022).
However, DDGS, when included in confinement diets, at a proportion of 30%, positively increases the crude protein content of the diet, combined with the addition of non-rumen degradable protein, to the detriment of rumen degradable protein values. From this perspective, there is a need to clarify whether diets that rely on a high use of DDGS require a correction of the proteins degradable in the rumen (RDP) with the associated use of urea inclusion.
Therefore, this work hypothesized that increasing the inclusion of urea in diets using DDGS could improve the efficiency of nitrogen use by animals. Thus, the objective was to evaluate the use of distillers’ dry grains with solubles (DDGS) associated with the inclusion of increasing levels of urea (0.0, 0.5, 1.0, 1.5) in the diet of confined sheep based on characteristics intake and nutrient digestibility.
The animal experimentation protocol was approved by the Ethics Committee on the Use of Animals (Ceua) of the Federal Institute of Rondônia, registered with number 005/21, in accordance with the precepts of Law nº 11,794, of October 8, 2008, and with the standards published by the National Council for the Control of Animal Experimentation (Concea).
The experiment was conducted at the Federal Institute of Education, Science, and Technology of Rondônia, Campus Colorado do Oeste, located at BR 435, km 63, a rural area at latitude 11º 43'S and longitude 49º 15'W, and an altitude of 460m in the municipality of Colorado do West, Rondônia. The hot and sub-humid tropical climate predominates, with four months of drought and eight months of rain.
Eight animals of the Santa Inês breed, males, castrated, with 40 kg of initial body weight, aged 12 months, were used to evaluate the use of dry distillers’ grain with solubles (DDGS) associated with urea levels in a confinement diet on nutritional parameters. The animals were distributed in a double 4x4 Latin square design, with four experimental periods of 21 days each, and each period consisted of 16 days of adaptation and five days for sample collection.
Before starting the experimental periods, the animals were weighed, marked with numbered collars, and treated with endo and ectoparasites with administration of Ivermectin (Ivomec® et al., BR). Subsequently, they were distributed in 8 pens (5m2), one animal per pen, and provided with drinking and feeding troughs (unilateral access of 0.5m for each animal).
The diets included 30% DDGS in the dry matter, associated with increasing levels of urea (0.0, 0.5, 1.0, and 1.5%) in the dry matter (Table 1).
According to NRC (Nutrient…, 2007), the diet with 0% urea inclusion was formulated to meet the energy and protein demands of a sheep with an average body weight of 40 kg and a performance of 250 g/animal/day. The diet was provided ad libitum, with an adjustment of 5% leftovers, and carried out in two daily treatments, at 8 a.m. and 4 p.m.
The intake and digestibility of nutrients were estimated in each experimental period, between the 17th and 20th day, with measurement of intake through the difference in the amount of feed offered in relation to the daily leftovers (for 24 hours), and feces sampling was carried out. During the same period, at the times of 6:00 and 14:00, 8:00 and 16:00, 10:00 and 18:00, 12:00 and 20:00, on the 17th, 18th, 19th, and 20th day, respectively, to estimate indigestible nutrients.
Indigestible neutral detergent fiber (iNDF) was used as an indicator of diet digestibility. According to Valente et al. (2012), the concentration of iNDF was determined in samples of the diet provided and in feces through in situ incubation for 288 hours.
The samples of the feed offered leftovers and feces were dried in a forced ventilation oven at 55ºC for 72 hours for subsequent laboratory analysis. Samples of dietary ingredients, feed provided, daily leftovers and feces were analyzed for dry matter (DM, INCT-CA G-003/1), crude protein (CP; INCT-CA N-001/1), ether extract (EE; INCT-CA G-004/1), neutral detergent fiber corrected for ash and protein (apFDN; INCT-CA F-002/1), without the use of sodium sulfite, according to Detmann et al. (2012).
Non-fibrous carbohydrates (NFC) were estimated according to Hall (2000). Total digestible nutrients (TDN) were calculated with adaptations to the method described by Weiss (1999) using the following equation: TDN (g/kg) = CPD + NDFcpD + CNFD + 2.25EED, where CPD = digestible crude protein, NDFcpD = neutral detergent fiber corrected for ash and digestible proteins, NFCD = digestible non-fibrous carbohydrates, and EED = digestible ether extract.
The analyses referring to the variables evaluated were in accordance with a simultaneous double 4x4 Latin square design, with four treatments and eight replications. The results were interpreted statistically using analysis of variance. For comparisons of urea inclusion levels, the regression test was adopted using mutually orthogonal contrasts, using the Mixed procedure of the Statistical Analysis System, version 9.1.3 (2003), with 5% significance and 10% trend.
Dry matter intake (DMI), dry matter intake per body weight (DMI, BW), organic matter intake (OMI), neutral detergent fiber intake (FDNI), non-fibrous carbohydrate intake (NFCI), total digestible nutrients (TDNI), and total digestible nutrients (TDN) content were not influenced (P>0.05) by the increasing inclusion of urea in the diet's DM (Table 2).
Nutrient intake of confined sheep fed with distillers dried grains with solubles (DDGS) associated with the inclusion of increasing levels of urea (0.0; 0.5; 1.0; 1.5% in the dry matter of the diet).
Observing the intake of crude protein (CPI), a quadratic effect (P<0.05) is noted depending on the amount of urea supplied in the diet; therefore, the CPI increased until reaching 1% of urea in the DM of the diet, and when 1.5% of urea was added to the DM of the diet, the CPI reduced.
Regarding the intake of ether extract (EEI), a tendency towards a quadratic effect (P=0.08) was observed, in which EEI was higher between 0.5 and 1% of urea in the diet's DM and when 1.5% urea in the DM diet reduced EEI.
The digestibility of organic matter (OMD), crude protein (CPD), neutral detergent fiber (NDFD), and non-fibrous carbohydrates (NFCD) were not influenced (P>0.05) by the increasing inclusion of urea in the DM of diet (Table 3). However, the digestibility of ether extract (EED) showed a tendency towards increasing linear behavior (P<0.10) with increasing inclusion of urea in the DM of the diet.
Apparent digestibility of nutrients in confined sheep fed with distillers' dried grains with solubles (DDGS) associated with the inclusion of increasing levels of urea (0.0; 0.5; 1.0; 1.5% in the dry matter of the diet)
Even though no effect was observed on dry matter intake (Table 2), crude protein intake was increased by increasing the content in the diets (Table 1), corresponding to 16.3, 17.7, 19.0 and 20.4% with the inclusion of 0.0, 0.5, 1.0, and 1.5% urea.
The DDGS inclusion level was maintained for all treatments at 30% (Table 1). Dried distillers’ grains with solubles consist of co-products obtained from the conversion of corn into alcohol through dry milling. Conventionally, the corn grain goes through a fermentation stage, and in a fractional way, the fiber, germ, and endosperm of the corn are separated. After this step, the unfermented fraction consists of dried distillers’ grains with solubles (Khullar et al., 2009; Belyea et al., 2010).
However, DDGS is considered a protein source with low degradability in the rumen, presenting high intestinal digestibility and allowing the absorption of amino acids in the intestine, resulting in increased animal performance (Siebert and Hunter, 1982; Schingoethe et al., 2006); in addition to being used to feed ruminants. Based on this assumption, the use of DDGS in the diet of ruminants has been of great relevance in the production of these animals, which were pioneers in the intake of this co-product, which, in addition to its high nutritional value, stimulates rumination, providing considerable additions to the production system (Werle et al., 2018).
As for urea (CH₄N₂O), it is an organic substance rich in non-protein nitrogen; it stimulates the growth of urease bacteria, which convert nitrogen into microbial protein for later use by the animal. In this process that occurs in the rumen, urea is hydrolyzed, ammonia, and transformed into microbial protein in a ratio of 1.0g of urea can become 2.81g of microbial protein (Oliveira et al., 2022). In this study, urea was used for nitrogen balance in the rumen that will serve for the growth of bacteria that degrade fiber.
Furthermore, the protein, in turn, can be classified into two groups: RDP and proteins non-degradable in the rumen (RUDP) (Santos et al., 1998). Rumen microorganisms are generated from RDP peptides, amino acids, and ammonia that are used for the synthesis of microbial protein for animal use (Schwab and Broderick, 2017).
In this way, a source of RUDP (from DDGS) was used in the diet as a strategic form, as it is not affected by rumen microorganisms, to be absorbed in the small intestine, as an amino acid supply to meet the requirements of animal categories. Who needs a more significant amount of protein to meet the possible limitations imposed by the diet used (Schwab and Broderick, 2017). Given this, it was proposed to add increasing levels of urea to the DM of the diet (source of RDP) to evaluate a possible protein deficiency in the rumen, which the use of DDGS alone would not meet.
Pereira et al. (2008) evaluated the intake and apparent digestibility of nutrients in beef cattle receiving diets containing 0, 0.5, 1.0, and 1.5% urea in total dry matter. The proportions of the concentrate ingredients were soybean meal, corn meal, salt, calcitic limestone, urea, ammonium sulfate, and dicalcium phosphate. As a source of roughage, sorghum silage, Volumax hybrid, was used in a roughage: concentrate ratio of 70:30, based on dry matter. They found that the intake and digestibility of DM, OM, CP, EE, TC, NDF, NFC, and TDN were not influenced by increasing levels of urea in the diet. This is different from what was observed in the results of this study, in which urea influenced some intake variables (CPI) and digestibility (EED).
Magalhães et al. (2006) found that the intake of DM and CP were not influenced by the addition of urea at 0% levels, 0.65%, 1.30%, and 1.95%, which is different from the current study, in which protein intake increased. The increase in protein intake was expected due to the increase in urea in the diet, as, according to Wilson et al. (1975), the negative effect on intake with urea inclusion is only observed at levels greater than 2% in the dietary DM. In this study, the maximum inclusion of urea was 1.5% in the dietary DM, being the inclusion level that favored the increase of protein intake.
For Magalhães et al. (2006), despite not having obtained results of increased intake of DM and CP with increasing addition of urea to the DM of the diet, DM and CP digestibility increased, with the justification for this result by meeting the amount of ammonia for ruminal microorganisms with the addition of RDP in the diets, favoring the digestibility of DM. In relation to CP, it can be justified by the fact that urea is considered 100% digestible in the rumen environment.
Uwituze et al. (2010) used a diet with 25% inclusion of DDGS in the dry matter of the diet, which resulted in an improvement in the total digestibility of DM (P = 0.01), OM (P = 0.01), starch (P = 0.02), and CP (P = 0.03), but did not affect the total digestibility of NDF (P = 0.99) and ether extract (P = 0.17). The results observed differ from the current study with the inclusion of 30% of DDGS in the DM of the diet because, in relation to EED, there was a significant effect with the inclusion of urea in the diet. However, in contrast to EED results, Magalhães et al. (2006) did not obtain a significant effect on the digestibility of EE, only demonstrating oscillation in the results according to the levels of urea in the diet (0.0, 0.65, 1.30, and 1.95% in DM of the diet).
Vander Pol et al. (2006) state that when using DDGS in the diet of animals in confinement as a source of energy in the proportion of 15% to 25% of the DM of the diet, there is no need to use urea in the animals' diet, suggesting possible recycling nitrogen (via saliva or rumen epithelium), to the point that the use of DDGS could meet protein requirements. Since, in this study, 30% of DDGS was used in the DM of the diet, precisely with the aim of meeting the possible need for metabolizable protein for the animal, corroborating with the author above, in which it is concluded that urea was not included in this level of DDGS use in confinement diets.
Klopfenstein et al. (2008) state that the inclusion of DDGS, at a level of up to 30% in confinement diets, increases the availability of RUDP, promoting a more excellent supply of metabolizable protein to the animal, which can provide more protein and energy for animal metabolism with greater efficiency compared to proteins or carbohydrates degradable in the rumen, as RUDP has no fermentative losses. The use of DDGS between 20 and 30% inclusion promotes maximum dry matter intake and weight gain, and the inclusion of 10 to 20% promotes maximum feed efficiency.
According to Nunez et al. (2015), the use of DDGS at a level higher than 20% of inclusion in the diet would already promote a necessary supply of metabolizable protein by the animal. The use of urea would cause an excess of nitrogen in the liver, which could reduce matter drought and increase the energy cost of nitrogen purification, both for excretion and recycling. Moreover, that reaffirms the non-inclusion of urea in these diet profiles.
There is no need to include urea in diets that use 30% DDGS in DM of confined lambs, as it does not affect intake and digestibility.
ACKNOWLEDGMENTS
The authors would like to thank the funding for the realization of this study provided by the Federal Institute of Rondônia, campus Colorado do Oeste.
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