Olagunju Lydia K, Casper David P
Dairy Science Department, South Dakota State University, Brookings, SD 57006, USA.
Casper's Calf Ranch, LLC, Freeport, IL 61032, USA.
Transl Anim Sci. 2024 Aug 30;8:txae130. doi: 10.1093/tas/txae130. eCollection 2024.
The study objective was to evaluate dietary limestone buffer inclusion rates for impacting nutrient digestibility and excretion when growing dairy cattle are fed high distiller grains with solubles (DDGS) limit-fed ration. The hypothesis was that feeding more limestone buffer would offset a low rumen pH when feeding a high DDGS inclusion rate. Five ruminally cannulated Holstein and Brown Swiss steers were used in a crossover design having 2-wk periods to evaluate high and low buffer inclusion rates when limit-fed. Treatments were similar in ingredient composition being: 1) 40% DDGS at 0.80% high CaCO buffer inclusion () and 2) 40% DDGS with 0.25% low CaCO buffer inclusion ( with the remaining ration consisting of grass hay with minerals and vitamins. Rations were limit-fed at 2.50% of body weight () using Calan feeding doors with steers being weighed every 2 wk with ration amounts adjusted accordingly. Rumen fluid was collected via the ruminal cannula at the start and end of each period for pH, ammonia-n, and volatile fatty acid (VFA)s. Fecal grab samples were collected at the end of each period for measurement of total-tract nutrient digestibility. There were no treatment-by-period interactions ( > 0.10) for any of the growth parameters measured. Gains in frame growth parameters were similar ( > 0.10) for steers fed both rations. BWs and gains were similar ( > 0.10) for steers fed both rations. Steers fed the LOW ration demonstrated a numeric improvement in average daily gain combined with a tendency ( < 0.06) for lower dry matter intake resulting in an improved ( < 0.01) feed efficiency (gain:feed) compared with steers fed the HIGH ration. Steers fed HIGH demonstrated greater ( < 0.01) ruminal ammonia-N and isovalerate concentrations compared with steers fed the LOW buffer ration. Steers fed both buffer inclusion rates were similar ( > 0.10) for ruminal pH and remaining VFAs concentrations. Steers fed both buffer inclusion rates were similar ( > 0.10) in DM and organic matter digestibilities. Limit-feeding a high DDGS inclusion rate ratio combined with a low buffer inclusion rate improved feed efficiency while maintaining growth performance. The study hypothesis was rejected in that feed efficiency can be enhanced when feeding a high DDGS ration by feeding a low calcium carbonate buffer.
本研究的目的是评估在给生长中的奶牛饲喂高比例含可溶物的干酒糟（DDGS）限量日粮时，日粮中添加石灰石缓冲剂的比例对养分消化率和排泄的影响。假设是在高比例添加DDGS的日粮中，添加更多的石灰石缓冲剂可以抵消瘤胃pH值降低的影响。采用交叉设计，选用5头装有瘤胃瘘管的荷斯坦和瑞士褐牛阉牛，每个为期2周的阶段评估高缓冲剂添加比例和低缓冲剂添加比例的限量饲喂情况。各处理组的日粮成分相似：1）40% DDGS，碳酸钙缓冲剂添加比例为0.80%（高添加比例）；2）40% DDGS，碳酸钙缓冲剂添加比例为0.25%（低添加比例），其余日粮由禾本科干草、矿物质和维生素组成。使用卡兰喂料门按体重的2.50%（体重）对日粮进行限量饲喂，每2周对阉牛称重并相应调整日粮量。在每个阶段开始和结束时，通过瘤胃瘘管采集瘤胃液，测定pH值、氨氮和挥发性脂肪酸（VFA）。在每个阶段结束时采集粪便随机样本，测定全消化道养分消化率。在所测定的任何生长参数方面，均未发现处理与阶段之间的交互作用（P>0.10）。两种日粮饲喂的阉牛在体躯生长参数方面的增重相似（P>0.10）。两种日粮饲喂的阉牛体重和增重相似（P>0.10）。与饲喂高比例日粮的阉牛相比，饲喂低比例日粮的阉牛平均日增重有数值上的提高，且干物质摄入量有降低的趋势（P<0.06），从而提高了饲料效率（增重：饲料）（P<0.01）。与饲喂低缓冲剂比例日粮的阉牛相比，饲喂高比例日粮的阉牛瘤胃氨氮和异戊酸浓度更高（P<0.01）。两种缓冲剂添加比例的阉牛在瘤胃pH值和其余挥发性脂肪酸浓度方面相似（P>0.10）。两种缓冲剂添加比例的阉牛在干物质和有机物消化率方面相似（P>0.10）。限量饲喂高比例DDGS日粮并结合低缓冲剂添加比例可提高饲料效率，同时维持生长性能。研究假设被否定，即在饲喂高比例DDGS日粮时，通过饲喂低碳酸钙缓冲剂可提高饲料效率。
