The Study On The Effects Of Polymer Coated Urea And Sodium Bentonite In Sheep Fed Corn Stalks As Basal Roughage Diet

Three experiments were conducted to investigate the effects of polymer coated urea and sodium bentonite on sheep fed corn stalk as basal roughages diet, therefore three experiments has been done. Experiment1:Four ruminally cannulated Dorper x thin-tailed Han crossbred wethers were used in a4x4Latin square design experiment to evaluate the effect of polymer-coated urea (Optigen II) and sodium bentonite (SB) on intake, nutrient digestibility, nitrogen retention, rumen fermentation and microbial nitrogen production in sheep fed high levels of corn stalk. Wethers were housed in an enclosed, climate-controlled room in individual pens. Each period lasted24days(d) with14d of diet adaptation and10d of sampling (5d for digestibility and1d of rest before rumen fluid sampling to prevent interference with the digestibility trial,1d for rumen fluid collection, and3d for the in situ trial). Four days prior to the digestibility trial, animals were placed in individual metabolism cages and allowed to adapt to their cages.Four isonitrogenous and isocaloric diets were formulated with60%corn stalk and40%concentrate (DM basis). The control diet (CON) consisted of barley, wheat bran, and soybean meal, the polymer-coated urea diet (PCU) consisted of barley, wheat bran, corn, and Optigen (soybean meal replaced by Optigen), and the SB diet (SB) was comprised of the control diets supplemented with2%SB, and the PCUSB diet was based on the PCU diet with an additional2%SB. Data were analyzed by analysis of variance for a4x4Latin square design using the MIXED procedure from SAS (1999) with variance components and a covariance structure Sheep on PCU treatment showed a greater OM digestibility (P=0.03), true OM digestibility (P=0.04) compared to CON and SB treatment. Nitrogen digestibility in PCU was greater (P<0.01) compared to CON, SB and PCUSB treatments, also it was higher in SB and PCUSB than CON, but digestibility of other nutrients and DMI did not change. SB did not alter nutrient digestibility except for nitrogen. Dietary treatments did not affect nitrogen intake, or its urinary excretion, but fecal N tended to be lower (P=0.09) for PCU. Nitrogen retention tended to increase (P=0.09) in sheep fed Optigen. Moreover, urinary purine derivatives (PD) and ruminal microbial nitrogen production were not influenced by treatments. Ruminal propionate proportions were increased (P<0.01) in diets that included Optigen, but an addition of SB to Optigen did not alter the ratios. The values of ruminal pH and total VFA were also not influenced by treatments. Ruminal NH3-N levels in PCU continuously increased, with the highest level achieved3h after feeding, and sustained for up to7h. Ruminal DM disappearance of corn stalk increased in PCU and SB treatments compared to CON at24h, was greater than CON or PCUSB at48h (P<0.01), but was lowest at72h for the CON treatment (P<0.05). The effective degradability (ED) of corn stalk DM increased in PCU and SB (P<0.05). Therefore, using Optigen as a source of non-protein nitrogen (NPN) to replace soybean meal in sheep fed high levels of corn stalk improved the digestibility of OM, nitrogen, and ED of corn stalk DM. Although SB improved ED of corn stalk DM, it had no effect on nutrient digestibility except for nitrogen. Adding SB to Optigen had no beneficial effects on nutrient digestibility, nitrogen retention, microbial nitrogen, or rumen fermentation and ED of corn stalk DM.Experiment2:This experiment was designed as same as Expt.1, but the ratio of concentrate to roughages changed to60:40. Four isonitrogenous and isocaloric diets consisting of60%concentrate and40%corn stalk (dry matter basis) were formulated. Apparent digestibility of OM tended to be lower (P=0.06) for sheep on the SB and PCUSB diets. True OM digestibility and N digestibility was lower (P=0.04and0.02, respectively) for SB treatment than other treatments. N retention and ruminal microbial nitrogen production were lower (P=0.03) in SB or PCUSB-fed sheep than that of CON. Ruminal NH3-N concentration was decreased in SB-fed sheep (P=0.03) compared to other treatments. The ruminal concentration of total VFA tended to be greater (P=0.052) in PCUSB-fed sheep than CON. PCUSB treatment decreased the ruminal concentration of acetate (P=0.03) and the ratio of acetate to propionate (P=0.01), but increased the ruminal concentration of propionate (P=0.02) and valerate (P<0.02) when compared with the other treatments. Ruminal NH3-N concentrations in PCU continuously increased, with a peak level achieved3h after feeding, and sustained for up to9h. replacing soybean meal with Optigen for sheep fed high levels of concentrate had no adverse effects on nutrient digestibility, microbial nitrogen, rumen fermentation and ED of corn stalk DM. However, adding SB to Optigen had no beneficial effects on nutrients digestibility, N retention, microbial N and ED of corn stalk DM.Experiment3:The objective of this experiment was to evaluate the effects of replacing different levels of soybean meal by Optigen II on feed intake, growth performance and blood parameters of fattening lambs. Sixty-four Dorper x thin-tailed Han crossbred lambs were blocked by BW [27±3.3(s.d.) kg] and allocated in a randomized complete block design to4treatments. Each treatment had4pens with4lambs per pen. The treatments were control (PCUO), PCU33, PCU67, and PCU100with0,33%,67%, and100%substitution rate of soybean meal nitrogen by Optigen II (DM basis), respectively. Four isonitrogenous (CP=13.5%) and isocaloric (ME=8.2Mj/Kg) dietary treatments contained60%concentrate and40%corn stalk (DM basis) and were offered ad libitum as TMR to ensure approximately5%ort. Lambs were fed56d after14d adaptations twice daily in two equal portions at7:00and19:00h. Data were analyzed as a RCBD using the GLM procedure of SAS (pen was as the experimental unit). Substitution of33and67%of soybean meal nitrogen with Optigen had no effects on DMI, but PCU100significantly decreased DMI (P=0.04). There was no difference in average daily gains (ADG) between PCU33and CON. ADG were significantly decreased by increasing dietary Optigen (P<0.01). The ratio of gain to feed (G/F) was not influenced by replacing33%of soybean meal nitrogen with Optigen, but G/F was decreased (P=0.02) in PCU67or PCU100compared to CON. Blood urea nitrogen tended to linearly increase (P=0.09) with increasing Optigen in the diet. Substitution of33and67%of soybean meal nitrogen by Optigen had no effect on plasma total protein, but it was lowest (P=0.02) in PCU100. The results showed that soybean meal could be partly replaced by Optigen in the diet of feedlot lambs. Substitution of33%soybean meal nitrogen by Optigen had no negative effects on growth performance or blood parameters in feedlot lambs fed diets containing40%corn stalk.