Effect of Forage Maturity on Ration Digestibility and Production by Dairy Cows

Mixed grass-legume silages harvested at early and late maturities from the same field were evaluated in three trials to determine maturity effects on ration digestibility when forages were fed alone or in complete rations. In situ dry matter disappearance was examined using a rumen-fistulated steer. Rate of disappearance of potentially digestible dry matter was reduced for forage of greater maturity (−.0504 h⁻¹ for early versus −.0316⁻¹ for late cut silage). Nonlactating cows were used to determine forage digestibility. Apparent dry matter (69.2 versus 54.2%), acid detergent fiber (70.8 versus 52.7%), neutral detergent fiber (74.1 versus 55.9%), and crude protein (66.2 versus 45.6%) digestibilities were higher for early cut forage.Ration digestibility and milk production response were also measured. Concentrate to forage ratios necessary to meet energy requirements were 60:40 and 78:22 for diets containing early or late cut forage, respectively. Digestibilities of acid detergent fiber (60.2 versus 42.5%) and neutral detergent fiber (62.0 versus 52.7%) were higher for lactating animals consuming ration containing early cut forage. Milk yield and composition was not affected by diet. For each day of advancing forage maturity, approximately 1% more concentrate was needed in the total ration.     

全脂乳与脱脂乳挥发性风味成分对比分析

HS-SPME结合GC/MS对比分析全脂乳(WM)和脱脂乳(SM)的挥发性风味成分。结果表明,50/30μm CAR/PDMS/DVB萃取纤维萃取得到的全脂乳、脱脂乳的挥发性风味物质的种类与65μm PDMS/DVB相当,即:全脂乳11种,脱脂乳8种,只是在萃取含量上有差异。因此,相对于65μm PDMS/DVB而言,50/30μm CAR/PDMS/DVB较适合乳风味挥发性物质的萃取。HS-SPME结合GC-O对比分析全脂乳和脱脂乳的呈香组分结果显示,脱脂乳中未发现香气强度较高的呈香成分。而在全脂乳中辛酸(清香)、癸酸(油脂味)香气强度较高。这些结果能为全脂乳和脱脂乳的风味物质组成提供有用信息。     

Effect of Ration Protein Content and Solubility on Milk Production of Primiparous Holstein Heifers

Twenty-eight primiparous heifers were blocked at calving and assigned to four dietary treatments in a 2 × 2 factorial arrangement of two crude protein concentrations (15.4 and 20.7%) and two protein solubilities (22.8 and 53% of protein). Heat-treated soybeans replaced raw soybeans in low solubility rations. Rations were offered for the first 10 wk of lactation divided into two 5-wk periods. Feed was offered ad libitum in period 1 and restricted in period 2. Digestibility and N balance were measured at completion of the lactation study. Body weight change, DM intake, milk yield, milk protein percentage, rumen pH, and total VFA were not affected by treatments. Milk fat percentage was increased by higher CP content during period 1, resulting in a 16.2% increase in 4% FCM. Plasma urea N and rumen NH₃ were elevated by higher CP content. Reducing protein solubility depressed rumen NH₃. A protein × solubility interaction for the acetate to propionate ratio suggests that protein and solubility combinations that optimized plasma urea N and rumen NH₃ provided a more favorable rumen environment and supported highest milk production. Nitrogen digestibility was influenced most by ration CP; however, lower solubility improved DM and N digestibilities. Both dietary CP content and solubility must be considered to maintain optimum rumen environment.     

Influence of Dietary Protein Concentration and Degradability on Milk Production,Composition, and Ruminal Protein Metabolism

Four groups of cows in early lactation, each group containing one mature cow and three cows in first lactation, were in a 4 × 4 Latin-square arrangement of treatments for us to study influences of altering quantity of undegraded dietary crude protein and quantity of crude protein on milk production and composition. Diets supplemented with protein sources were 1) soybean meal positive control (22.7% crude protein), 2) whole cottonseed-corn gluten meal (14.7% crude protein), 3) extruded whole soybean (14.5% crude protein), or 4) soybean meal supplemented (15.7% crude protein). Concentrate and sorghum silage were fed in a ratio of 62:38 dry matter. Dry matter intake was not influenced by dietary crude protein concentration or source. Cows consuming diet 2 produced less milk, milk protein, total solids, and solids-not-fat than cows receiving diets 1 and 4. Efficiency of conversion of dietary crude protein to milk protein was highest for cows receiving diet 3 and lowest for diet 1.Trial 2, a 4 × 4 Latin-square trial for collection of abomasal digesta, had four ruminal and abomasal cannulated steers and the four diets from the lactation trial; the trial was to determine the influence of source and concentrations of protein on quantity of protein reaching the abomasum daily. Crude protein intake by steers fed diet 1 was greater than for the other three diets. Percentages recovery of dietary crude protein were 122 and 130 for treatments 2 and 3, intermediate for treatment 4 (107%), and lowest for diet 1 (88.0%); crude protein digestibility in the total tract was highest for steers receiving diet 1.     

Effects of Altering Milk Production and Composition by Feeding on Multiple Component Milk Pricing Systems

Data representing 1105 cows were obtained from published scientific reports to estimate the extent to which changes in feeding may affect the composition of milk and the production of milk protein and milk fat. Changes in milk pricing systems were also related to dairy cattle feeding practices that dairy producers may profitably implement. Regression equations were derived to estimate the transfer of gross energy in feed and gross energy in crude protein of feed into milk fat and milk protein. Feeding rations that contained 59% concentrate increased dry matter and crude protein intakes compared to feeding rations that contained 49% concentrate. Feeding higher energy rations also resulted in increased production of milk, milk fat, and milk protein and returned a greater profit over feed costs when milk was priced using each of four milk pricing systems. An increase in milk production, rather than a change in composition of milk components, accounted for most of the economic gain.     

全脂奶粉中蛋白质和氨基酸组成的比较研究

利用凯氏定氮仪和氨基酸自动分析仪对全脂奶粉中的蛋白质和氨基酸进行分析,测得全脂奶粉中氨基酸总量约占蛋白质含量的95%,各种氨基酸含量占氨基酸总量的比值的极差均小于0.010,氨基酸组成相对稳定,特征氨基酸检测快速、准确,各种分析数据可为建立系统的蛋白质监测技术体系提供理论依据。     

Effect of Shredding Alfalfa on Cellulolytic Activity,Digestibility, Rate of Passage,and Milk Production

A series of trials was performed with sheep and goats to compare mechanically shredded with conventionally (control) harvested alfalfa hay. Shredded hay tended to contain less CP and more cell wall constituents than the control; digestibility of NDF in vitro also was increased by shredding. Intake of DM and digestibilities of NDF and ADF were increased in sheep fed shredded hay. Digestibilities of DM and CP were similar between treatments. Total tract digestibilities determined using acid detergent lignin and Yb as internal and external markers were similar to those obtained by total collection. There was no effect of shredding on rate of passage and total mean retention time of hay in the digestive tract of sheep. Ruminal pH and VFA were not altered by shredding of hay. However, production of 4% FCM and milk protein content was increased in goats fed shredded hay. Shredded hay suspended in the rumen in situ had higher particle-associated carboxymethylcellulase activity throughout the incubation period than did control hay. The enzyme activity was maximal at 6 h and declined thereafter for both hays. The pattern of particle-associated carboxymethylcellulase activity was similar to that of NDF digestion in vitro.     

Biofilm Formation in Milk Production and Processing Environments; Influence on Milk Quality and Safety

Abstract: Bacteria in milk have the ability to adhere and aggregate on stainless steel surfaces, resulting in biofilm formation in milk storage tanks and milk process lines. Growth of biofilms in milk processing environments leads to increased opportunity for microbial contamination of the processed dairy products. These biofilms may contain spoilage and pathogenic microorganisms. Bacteria within biofilms are protected from sanitizers due to multispecies cooperation and the presence of extracellular polymeric substances, by which their survival and subsequent contamination of processed milk products is promoted. This paper reviews the most critical factors in biofilm formation, with special attention to pseudomonads, the predominant spoilage bacteria originating from raw milk. Biofilm interactions between pseudomonads and milk pathogens are also addressed, as emerging risks and future research perspectives, specifically related to the milk processing environment.     

Whole Milk Reverse Osmosis Retentates for Cheddar Cheese Manufacture: Cheese Composition and Yield

The impact of concentrating whole milk by reverse osmosis prior to Cheddar cheese making was studied. Heat treated, standardized, whole milk was reduced in volume by 0, 5, 10, 15, and 20% prior to Cheddar cheese manufacture. Milk solids at various milk volume reductions were 11.98, 12.88, 13.27, 14.17, and 15.05%, respectively. Permeates contained only traces of organic matter and would not create a significant by-product handling problem for a cheese plant. Solids content of the whey from cheese making increased with increasing milk concentration. Proximate compositions of reverse osmosis cheeses were comparable to control cheeses. Fat losses decreased, and fat retained in the cheese increased with increasing milk solids concentration. Improved fat recovery in the cheese was related to the amount of mechanical homogenization of milk fat during the concentration process. Actual, composition adjusted, and theoretical cheese yields were determined. Increased retention of whey solids and improved fat recovery gave cheese yield increases of 2 to 3% above expected theoretical yields at 20% milk volume reduction. Water removal from whole milk prior to Cheddar cheese manufacture gave increased productivity and cheese yield without requiring different cheese-making equipment or manufacturing procedures.     

Extruding vs Pelleting of a Feed Mixture Lowers Apparent Nitrogen Digestibility in Dogs

The influence of extruding vs pelleting of a feed mixture on nitrogen, dry matter, fat and ash digestibility was investigated in six mature dogs. Extrusion decreased nitrogen digestibility, increased ash absorption and had no effect on dry matter and fat digestibility. After feeding the extruded diet, the pH of faeces was lowered and the faecal water content increased, suggesting that this diet stimulated bacterial fermentation in the intestine.     

棉籽油制备生物柴油技术研究

以棉籽油与甲醇为原料，在催化NaOH存在下，通过酯交换反应制得脂肪酸甲酯，考察了反应条件如醇油摩尔比、催化剂用量、反应温度、反应时间以及原料含水量等的变化对产率的影响，得到棉籽油酯交换反应的最佳反应条件为醇油物质的量比6：1，催化剂用量1．1％，反应温度45℃，反应时间55min。生物柴油的酯交换反应须严格控制原料中的水分。     

棉籽蛋白在天冬氨酸转氨酶发酵制备中的应用

进行了以棉籽蛋白替代蛋白胨和玉米浆的研究 ,培养大肠杆菌生产该酶 ,并对替代前后的酶活进行对比 ,确定了最佳培养基组成及发酵条件。研究表明 ,棉籽蛋白PM8成功替代原常规复合氮源后 ,培养基成本降低了4 0 %左右 ,发酵周期缩短了 2 5 % ,而L 苯丙氨酸的得率反而提高了 5 %。     

By-Product Feeds for Lactating Dairy Cows: Effects of Cottonseed Hulls,Sunflower Hulls,Corrugated Paper,Peanut Hulls,Sugarcane Bagasse,and Whole Cottonseed with Additives of Fat,Sodium Bicarbonate,and Aspergillus oryzae Product on Milk Production

In Experiment 1, Holstein cows (32) fed diets in three 28-day periods were used to evaluate a 3 × 2 × 2 factorial arrangement of fiber sources (sunflower hulls, pelleted cottonseed hulls, and pelleted undelinted cottonseed hulls at 35% of dry matter), fat (0 or 2.5%). and sodium bicarbonate (0 or 1.0%). Sixteen cows also received Aspergillus oryzae product (56.7 g/day) continuously. Sunflower hulls decreased daily intake (19.4 versus 25.1 kg), milk (23.3 versus 26.5 kg), milk protein (2.85 versus 2.95%), and body weight change (?.08 versus .90 kg), but milk fat percent was higher (3.54 versus 3.32%). Sunflower hulls depressed digestibility of dry matter, organic matter, and acid detergent fiber. Added fat reduced milk fat and protein percents. Experiment 2 evaluated fiber sources (20% ground corrugated cardboard boxes, combination of 10% cardboard and 10% peanut hulls, or 30% cottonseed hulls), animal fat (0 or 2.5%), sodium bicarbonate (0 or .75%), and condensed molasses solubles by-product from rum distilling (0 or 10%). Corrugated boxes effected lowest intake (18.0 kg/day), cottonseed hulls highest intake (23.5 kg/day), and combination intermediate (20.2 kg/day). Added fat depressed fat percent. Condensed molasses solubles lowered milk yield but increased milk fat percent (3.76 versus 3.30), molar percent of acetic acid, and ratio of acetic to propionic. In two other experiments whole cottonseed (12.5 or 15% of dry matter) with corn silage, pelleted steam pressure treated sugarcane bagasse, or cottonseed hulls increased milk yield but decreased milk fat percent, especially with pelleted bagasse.     

Production and Quality of Cheddar Cheese Manufactured from Whole Milk Concentrated By Reverse Osmosis

Pasteurized whole milk was concentrated by reverse osmosis (RO) on a pilot plant scale. The retentate was then used to produce cheddar cheese following the traditional method but using 50% less starter and 60% less rennet. The biochemical composition of the RO cheese was close to that of ordinary cheddar. The resulting non uniformity of the fresh curd as well as the granular texture of the cheese were probably due to the high lactose content of the retentate. Contamination of the milk from bacteria already present in the reverse osmosis system caused the high coliform level of the cheese.     

乳成分对牛奶起泡性和泡沫稳定性的影响

探讨牛乳中蛋白质、脂肪、乳糖和游离脂肪酸含量对卡布奇诺咖啡牛奶起泡性和泡沫稳定性的影响。研究结果表明:牛乳中蛋白质含量在2.8%~3.2%范围内,乳蛋白质含量与牛奶的起泡性和泡沫稳定性呈正相关性,蛋白质浓度越高牛奶的起泡性和泡沫稳定性越好;乳脂肪含量在0.5%~3.7%范围内,随乳脂肪含量的升高,牛奶的起泡性是缓慢提高,而泡沫稳定性相反是缓慢降低;乳糖含量在4.7%~5.5%范围内,随着乳糖含量的增加,牛奶起泡性降低,而泡沫稳定性提高;乳中游离脂肪酸含量在0.31 mmol/L~2.35 mmol/L范围内,随牛乳中游离脂肪酸含量增加,牛奶的起泡性和泡沫稳定性都呈显著降低。     

Effects of Feeding Protected Tallow on Composition of Milk and Milk Fat

Official methods were used to analyze composite samples of milk collected during the first 15 wk of lactation from 21 Holstein cows fed a milled ration containing 0 (basal), 15% (medium), or 30% (high) protected-tallow supplement (seven cows per treatment). Protein fractions and amino acid composition of the total proteins were determined from samples of individual milking. Melting characteristics of pooled samples were determined by nuclear magnetic resonance. Milk yield was similar for the three treatments, but percent fat and fat yield were higher for cows fed protected tallow. Percentages and yields of protein and solids-not-fat were decreased on the protected tallow treatments, especially for high tallow. The decrease in protein was in the casein fraction. Amino acid composition of the total proteins was similar for the three treatments. Feeding protected tallow caused decreases in all fatty acids except 4:0, 16:1, 18:0, and 18:1 which increased. Nuclear magnetic resonance indicated that butter from the basal group would be harder than that from cows fed protected tallow.     

Effects of Milk Composition and Genetic Polymorphism on Coagulation Properties of Milk

Milk samples from 31 Holstein cows of different phenotypes for β-casein, κ-casein, and β-lactoglobulin were collected monthly over the entire lactation. These samples were analyzed for total solids, fat, protein, casein fractions, lactose, urea, citric acid, somatic cell count, and pH. Rennet clotting time, rate of firming, and curd firmness as measured by a Formagraph were not significantly influenced by phenotypes for β-casein and κ-casein. Phenotype AA for β-lactoglobulin gave the best clotting time (3.91 min) and firmness of curd (36.30 mm) when compared with AB and BB phenotypes. Relative percentages of the different caseins and α-lactalbumin affected significantly rate of firming and curd firmness at cutting. Amount of κ-casein in milk was the most significant factor that affected curd firmness with a coefficient of regression of 15.96.