| The present study was conducted to investigate the effect of paitial or total replacement of maize grains with non-conventional feedstuffs (NCF) on rumen fermentation characteristics, rumen degradation rate, growth performance, nutrient digestion and carcass quality of beef cattle using in vitro gas production, in situ nylon bag technique, total collection digestion trial, and feeding-slaughtering trial.Expt.1. This study was conducted using chemical analysis and model predictions based on NRC and INRA models to compare the chemical compositins and energetic values of some NCF sources including brewer’s grains, tofu residue, Chinese jujube, and molasses. The results showed that contents of CP, NDF, ADF of brewer’s grains and tofu residue were higher than those of maize grains, but the content of starch was lower than that of maize grains. Although the CP content of Chinese jujube was lower than maize grains, their NDF, ADF and sugar were relatively high. Similar to Chines jujube, molasses contained higher sugar and slightly higher CP contents, but had lower NDF and ADF content than jujube. Soybean hulls had the content of CP similar to maize grains, but haigher contents of ADF and NDF than maize grains. In addition, the energetic contents of these NCF such as TDN, DE, ME, NEm, NEg were lower than maize grains. In summary, brewer’s grains, tofu residue, molasses, soybean hulls and Chines jujube due to their high nutritional values, would be used as alternative feeds for substitution of maize grains to feed ruminant animals.Expt.2. This study was conducted to evaluate the nutritive value of NCF-based diets in cattle using in vitro gas production (GP) technique. Three dietary treatments used as substrates were typical diet (TD;45.0%maize), partial replacement diet (PRD;15%maize,67%NCF) and total replacement diet (TRD;0%maize,100%NCF), respectively. The results showed that compared with TD, PRD and TRD had much lower starch content, but higher sugar, ADF and NDF contents. TRD showed a lower96h accumulative GP (P=0.002), potential GP (P=0.001) and GP rate (P<0.001) than TD and PRD, while the PRD was not significantly different from TD (P>0.05). H2percentage was not different among the three treatment diets. The contents of CH4and CO2for PRD were significantly lower than TD and TRD. There were no significant differences in pH among the three diets. Ammonia-N (mg/100ml) and total VFA (mmol/L) did not differ among the three diets. There were lowest acetate and valerate and highest butyrate for TD and there were highest acetate and valerate and lowest butyrate for TRD. Acetate to propionate ratios were significantly lower (p<0.01) for TD than PRD and TRD, whereas PRD and TRD were not significantly different (p>0.05). The digestibilities of organic matter (OMD) were significantly higher (P<0.01) for TD and PRD than TRD, while there were no difference (P>0.05) between TD and PRD. In conclusion, the nutritive values expressed with chemical compositions, gas production characteristics and organic matter digestibility were similar for partial replacement diets to typical diets, while totally replacement diet had lower nutritive values.Expt.3. This study was conducted to evaluate the degradation rate and degradation parameters of three NCF-based diets using the nylon bag method. Dietary treatments are the same as Expt.2. The results showed that the rapid degradation fraction (a) of dry matter of TD was significantly lower (P <0.05), while the slow degradation fraction (b) was significantly higher than (P<0.05) the other two diets. The effective degradation (ED) of DM of PRD and TRD was significantly higher than TD. The value "a" of CP was significantly higher (P<0.05) for TD than PRD and TRD, but the value "b" of CP was significantly lower (P<0.05) for TD than PRD and TRD. The value "c" and ED of CP was significantly lower for TD than the other two diets (P<0.05). The value a, c and ED of NDF were not significantly different (P>0.05) among three diets, but the b fraction of NDF was significantly lower for PRD than TD and TRD. hi conclusion, partial or total replacement of maize grains with NCF would improve the ruminal degradation of DM and CP, but not affect the degradation of NDF.Expt.4. This study was conducted using direct collection feces method to investigate the effects of partial or total replacement of maize grains with NCF on growth performance, blood metabolites, and ecnomics in Limousin crossbred feedlot cattle. Forty-five Limsin x Luxi crossbred bulls were used in a9Id-feeding trail. Dietary treatments were the same as Expt.2. The results showed that final body weights were not significantly different between groups (P>0.05). ADG and DMI were1.72and8.66,1.60and9.10, and1.40and9.11kg/d for TD, PRD and TRD, respectively. PRD and TRD exhibited lower ADG (P<0.01) and higher DMI (P<0.01) than TD. DMI (%of body weight) was not significantly different between groups (P>0.5). Feed efficiency (G/F) of PRD and TRD were lower than TD (P<0.01). Blood urea nitrogen (mg/dl) in PRD and TRD was higher than TD (P<0.01), while other blood parameters did not differ significantly. Feed costs (yuan/head/d) were9.70,6.38and4.69yuan for TD, PRD and TRD, respectively (P<0.01). Feed costs per kg gain (yuan) for PRD (4.10) and TRD (3.52) were significantly lower than TD (5.79; P<0.01). The out/input of TRD were significantly higher than TD, while P RD were significantly higher than TRD. In conclusion, while a traditional diet maximized the growth rate, partial or total replacement of maize grains with NCF proved economically acceptable due to lower costs. Partial replacement may prove economically competitive in China.Expt.5. This study was designed to study the impact of NCF substitution for maize grains on nutrient digestibility and fecal particle distribution of beef cattle. The results showed that dry matter intake of each group was not significant (P>0.05), but fecal DM excretion was significantly lower (P <0.01) for TD than PRD and TRD. The replacement of maize grains with NCF significantly (P<0.018) reduced OM digestibility, but not significantly affect digestibilities of DM, CP, NDF and ADF (P>0.05). After paitial or total replacement of maize grains with NCF, TRD and PRD had significantly higher large particle distributions in the manure than TD (P<0.01), especially the6mm-4mm and4mm-2mm section. In summary, using NCF inst ead of maize grains in the growing cattle diet reduced OM digestility, but did not significantly reduce the digestibilities of other nutrients.Expt.6. This study was conducted to study the effects of partial or total replacement of maize grains with NCF on slaughtering performance, carcass traits and beef quality. After the feeding trial,8cattle were randomly selected from each group to measure the slaughtering performance, carcass traints and beef quality. The results showed that dressing percentage, net meat percentage, bones:muscles, fat thickness, ribeye area, marbling score, yield index, shear force, cooking loss, drip loss, pH value, meat colour, meatm moisture, protein, fat and ash were not significantly different (P>0.05) among the three dietary groups, suggesting that using NCF for replacement of maize grains in the diet would not affect the slaughtering performance, carcass traits and beef quality. |
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