冷却排酸期间牛胴体温度与pH的变化及其对牛肉汁液渗出性的影响

为研究牛胴体温度与pH变化规律对牛肉汁液渗出性的影响,本研究对100头秦川牛胴体的前部(脖肉)、中部(外脊)、后部(臀肉)在屠宰后冷却排酸过程中温度与pH随屠宰后时间的变化进行了同步跟踪测定,并对冷却排酸后相应部位肉表面的汁液渗出性加以分析。结果表明,中部胴体温度下降速率最高,分别是前部和后部的1.75和1.45倍。前部胴体pH下降速率最小,中部和后部胴体下降速率分别是前部胴体的6.56和4.88倍,最终pH为前部胴体>中部胴体>后部胴体。而pH下降至6时的温度与汁液渗出性之间具有极好的正相关性,其线性回归方程拟合度R2均达到0.8以上。pH为6时的温度均对汁液渗出性有明显影响。结果提示,胴体温度与pH的相对变化会对肉的持水力产生明显影响。

Carcass and Meat Characteristics of Bulls from Arsi, Boran, Harar and Holstein Frisian Crosses Cattle Breeds Finished under Similar Level of Concentrate Supplementation

A study was conducted to evaluate the effect of age and breeds (Arsi, Borana, HF-Cross and Harar) on carcass and meat characteristics of bulls finished under similar feeding conditions. The feeding experiment was conducted for 90 days at Beef farm of Haramaya University. In this experiment, 24 bulls were fed with roughage (60%) which contained grass hay and wheat straw and concentrate (40%) which contained wheat bran, noug (gucia abysica) cake, maize grain, limestone, salt and ruminant premix. The bulls were transported to Bishoftu ELFORA export abattoir for slaughter following the procedure of the abattoir. The result of the study revealed that the average slaughter weight, hot carcass weight, cold carcass weight, shrink loss, commercial dressing and true dressing percentage were 179.1 kg, 86.8 kg, 82.7 kg 4.7%, 48.8% and 78.3%, respectively. Total edible and nonedible offal were significantly (P < 0.01) influenced by breed and age. Pelvic fat was significantly (P < 0.01) influenced by breeds. Meat yield percentages of Arsi, Boran, Harar, and HF-crossbred were 78.1%, 77%, 72.8% and 77.2% respectively. Meat yield was predicted from fat thickness and ribeye area with 61% accuracy. Arsi bulls attained the highest (78%) meat yield at early age but decreased by 0.713 rate as age of animals advanced by one digit whereas the meat yield from other breeds showed increment in meat yield percentage with the rate of 1.98, 1.1 and 0.1 for cross, Borana and Harar breed bulls, respectively as age advanced. Yield from fore shank, sirloin, top and bottom sirloin primal cuts were affected by breed. Arsi breed had higher meat bone ration than cross breed. Retailed meat yield was significantly (P < 0.001) predicted from rib area and subcutaneous fat thickness (P < 0.001) with a coefficient of determination 61%, from live animal trait and primal cuts with a coefficient of determination 89.56% and 94.78% respectively. Arsi bulls can be used for beef purpose at 2 - 3 years, as the meat percentage decreases thereafter;while bulls from Boran, cross breed and Harar breeds can be used up to 5 years of age. Meat to bone ratio indicated that HF-Crossbred was less appropriate for beef purpose than other breed bulls in this study. The rate of pH decline was not influence (P > 0.05) by age and breed in the current study.

一水肌酸对肉鸭胴体组成及肌肉系水力的影响

研究不同的一水肌酸(creatine monohydrate,CMH)补给方案对樱桃谷鸭生长性能、屠宰性能以及肌肉系水力的作用效果.试验选取体质量相近的25日龄健康樱桃谷鸭360羽,随机分成4组:Ⅰ组为对照组,饲喂基础日粮;Ⅱ组饲喂基础日粮+0.05%CMH;Ⅲ组试验期前5d饲喂基础日粮+0.4%CMH,随后10d饲喂基础日粮+0.05%CMH;Ⅳ组饲喂基础日粮+0.4%CMH.每组3个重复,每个重复30羽,试验期为宰前15d.结果表明:添加CMH能显著提高肉鸭腿肌率,提高肉鸭胸肌、腿肌宰后pH45min、pH24h,减少胸肌、腿肌滴水损失;其中,前5d添加0.4%CMH随后10d添加0.05%CMH的试验组其瘦肉率显著提高4.57%(P<0.05),腿肌滴水损失显著下降34.60%(P<0.05);另外,补充CMH能提高肉鸭血浆中肌酸含量,添加0.4%CMH其含量显著提高33.64%(P<0.05).结果提示:饲料中添加CMH能延缓宰后pH下降,提高肌肉系水力;前5d添加0.4%CMH随后10d添加0.05%CMH的补给效果优于其他方案,且樱桃谷鸭属于有效者或拟有效者.

疫病动物尸骸废水高温厌氧消化中的氨抑制

在不同的pH值和进水总氨氮(TAN)浓度下进行批次实验,对疫病动物尸骸废水高温厌氧消化中的氨抑制作用进行了研究。结果表明,分别固定pH值为7.0,7.4,7.8,8.2时,每个pH值下设置4个初始TAN浓度为100,800,1400,2400 mg·L^(-1),COD去除率分别下降了11.1%,26.7%,50.4%,74.4%,游离氨(FAN)浓度则分别从4,9,20,38 mg·L^(-1)上升到90,214,474,916 mg·L^(-1),FAN浓度的升高是反应器COD去除率下降的主要原因。产酸作用与产甲烷作用受氨抑制程度均随着TAN的升高而增加,且pH值越高,增加的趋势越明显,pH值为8.2时,FAN对两者的IC_(50)分别为843和453 mg·L^(-1),产甲烷作用比产酸作用对FAN更敏感,这导致VFA在反应器中积累。总VFA分别由26,48,129,214 mg·L^(-1)升至150,304,528,656 mg·L^(-1),其中乙酸分别由22,28,76,90mg·L^(-1)升至90,154,356,426 mg·L^(-1),VFA的积累类型表现为乙酸型,FAN抑制了乙酸营养型产甲烷菌的活性。