Resíduo da indústria de doces associado ao farelo de glúten de milho na alimentação de pequenos ruminantes

Abstract

The objective of this study was to evaluate the effect of replacing ground corn with candy industry residue (CIR) associated with corn gluten meal (CGM) on the intake and digestibility of dry matter and its constituents, water intake, nitrogen balance, ingestive behavior, ruminal dynamics and parameters, microbial protein synthesis, and blood biochemical profile of small ruminants. Four male goats and four male sheep (castrated, fistulated and cannulated in the rumen), with mean aged of over five years and mean body weight (BW) of 70.1 kg ± 0.51 and 63.5 kg ± 1.08, respectively, were used in a replicated 4 x 4 Latin Square with two squares. The experiment lasted 76 days, with four periods of 19 consecutive days, divided into 12 days for adaptation to diets and management and seven days for data collection and samples. The experimental diets consisted of levels of replacement of ground corn with the CIR:CGM mixture in the levels of 0, 133, 267, and 400 g/kg of DM in the diet and were formulated to meet the nutritional requirements for animal maintenance with roughage:concentrated ratio of 50:50. The CGM was used in the ratio in order to correct the protein content of the CIR. Sheep ingested more DM, organic matter (OM), crude protein (CP), non-fibrous carbohydrates (NFC) and total digestible nutrients (TDN) than goats. Fecal nitrogen (N) excretion, as well as rumination time and feeding efficiencies of DM and neutral detergent fiber corrected for ash and protein (aNDFac) were higher and idle time was shorter for sheep. The species did not differ in relation to aNDF and water consumption, apparent nutrient digestibility coefficients, N in urine, N absorbed, N-urea in plasma and urine, in addition to feeding time and rumination efficiencies of DM and aNDF (P > 0.05). The CIR:CGM mixture did not affect the intake of DM, MO and cNDF, DM and cNDF digestibilities (P > 0.05), N in urine, Naabsorbed (g/day), N-urea urinary (mg kg/BW), feeding time and feeding and rumination efficiencies of MS and aNDFcp. There was a trend (P = 0.08 and P = 0.07) for CP and N intakes, respectively; as well as total water, in kg/day (P = 0.06). The behavior for the consumption of CNF and TDN was quadratic, with maximum points of 363.8 and 715.4 g/kg day, respectively. The relationship between total water consumption and DM intake increased linearly (P ≤ 0.05). CP and NFC digestibilities increased linearly (P < 0.01), with a trend towards a quadratic effect on OM digestibility (P = 0.10). CP and CNF digestibilities increased linearly (P < 0.01). The CIR:CGM mixture promoted a reduction in the excretion of N in the feces and N-urea in the plasma. The replacement of corn by the CIR:CGM mixture in the diet of small ruminants did not affect the DM (P = 0.92) and NDF (P = 0.25) pools, as well as the rates of ingestion (Ki), passage (Kp) and ruminal degradation (Kd) of MS and NDF. However, the NDFi pool (P=0.03) linearly decreased and the ruminal passage rate of NDFi, Kpi (P=0.02) increased linearly as the levels of CIR:CGM mixture in the diet increased. Goats and sheep did not show significant differences (P>0.05) in any of the ruminal parameters among themselves, and there was no interaction between species and experimental diets. Dietary levels of the CIR:CGM mixture did not affect pH (P = 0.59). The unfolding of the interaction time x mixture levels for ruminal pH showed a quadratic effect (P<0.05), with minimum response points obtained at 5.92; 5.94; 5.86 and 5.85, which were reached at 3.95; 3.74; 3.59 and 3.44 hours after feeding, respectively. There was a linear decrease in N-NH3 concentration with increasing CIR:CGM mixture in the animals' diets, and an effect on the time and interaction of CIR:CGM levels with collection time. The replacement of corn by the mixture promoted a linear decrease of acetate concentrations (P = 0.001) in the rumen and the acetate:propionate ratio decreased linearly (P <0.0001). However, a linear increase (P = 0.006) was observed in ruminal propionate concentration. Butyrate concentration (P = 0.54) was not affected by substitution. The acetate:propionate ratio showed a quadratic effect (P = 0.0022) for the collection times, with an estimated minimum concentration of 1.73 μMol/mL at 3.42 hours after feeding the animals. In addition, there was interaction between the levels of the CIR:CGM mixture and collection times for the concentration of propionate. The variables evaluated for microbial protein synthesis did not show differences between goats and sheep, as well as on the interaction between species x substitution levels. The replacement of corn by CIR:CGM linearly increased (P = 0.03), uric acid excretion (mmol/L), but did not affect the concentration of allantoin, microbial nitrogen (N) in urine, N g/kg MO rumen fermentability (MOF) and efficiency of microbial synthesis. The concentrations of triglycerides (P=0.046), calcium (P=0.001), phosphorus (P=0.042), potassium (P=0.020) and magnesium (P=0.028) differed significantly between species, but there was no significant difference (P >0.05) in the interaction between the species and the substitution levels for the other parameters. However, glucose (P = 0.83), serum protein (P = 0.43), albumin (P = 0.64), creatinine (P = 0.79) and uric acid (P = 0.22), as well as enzymatic (P > 0.05) and mineral (P > 0.05) profiles were not influenced by the increase in the mixture in the diets. The mixture of candy industry residue with CIR:CGM corn gluten meal (in the proportion of 870:130 g/kg DM) can be used as a total substitute for ground corn in the diet of sheep and goats, without adversely affecting the nutrient intake and digestibility, water intake, balance of nitrogen compounds, ingestive behavior and animal metabolism, when fed with up to 400g of the mixture per kg of dry matter. The use of CIR:CGM in the diet of goats and sheep can contribute to the mitigation of the environmental impact by reducing the excretion of fecal nitrogen.