Relationship between composition and stability of bovine milk lysozyme.

The amino acid analysis, peptide mapping, and heat stability of bovine milk lysozyme are presented. The bovine milk lysozyme molecule contains approximately 154 amino acids and is strikingly different in amino acid content from human milk lysozyme and egg white lysozyme. Tryptic hydrolysis yielded 26 peptides, all of which are unique from tryptic peptides of human milk lysozyme and egg white lysozyme. In addition, bovine milk lysozyme was more heat stable than human milk lysozyme at pH 4.0 but more labile at pH 7.0 and 9.0. Possible explanations for the differences in heat stability are discussed.     

Changes in milk characteristics and fatty acid profile during the estrous cycle in dairy cows

The relationship of the estrous cycle to milk composition and milk physical properties was assessed on Holstein (n = 10,696), Brown Swiss (n = 20,501), Simmental (n = 17,837), and Alpine Grey (n = 8,595) cows reared in northeastern Italy. The first insemination after calving for each cow was chosen to be the day of estrus and insemination. Test days surrounding the insemination date (from 10 d before to 10 d after the day of the estrus) were selected and categorized in phases relative to estrus as diestrus high-progesterone, proestrus, estrus, metestrus, and diestrus increasing-progesterone phases. Milk components and physical properties were predicted on the basis of Fourier-transform infrared spectra of milk samples and were analyzed using a linear mixed model, which included the random effects of herd, the fixed classification effects of year-month, parity number, breed, estrous cycle phase, day nested within the estrous cycle phase, conception, partial regressions on linear and quadratic effects of days in milk nested within parity number, as well as the interactions between conception outcome with estrous cycle phase and breed with estrous cycle phase. Milk composition, particularly fat, protein, and lactose, showed clear differences among the estrous cycle phases. Fat increased by 0.14% from diestrus high-progesterone to estrous phase, whereas protein concomitantly decreased by 0.03%. Lactose appeared to remain relatively constant over diestrus high-progesterone, rising 1 d before the day of estrus followed by a gradual reduction over the subsequent phases. Specific fatty acids were also affected across the estrous cycle phases: C14:0 and C16:0 decreased (?0.34 and ?0.48%) from proestrus to estrus with a concomitant increase in C18:0 and C18:1 cis-9 (0.40 and 0.73%). More general categories of fatty acids showed a similar behavior; that is, unsaturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, trans fatty acids, and long-chain fatty acids increased, whereas the saturated fatty acids, medium-chain fatty acids, and short-chain fatty acids decreased during the estrous phase. Finally, urea, somatic cell score, freezing point, pH, and homogenization index were also affected indicating variation associated with the hormonal and behavioral changes of cows in standing estrus. Hence, the variation in milk profiles of cows showing estrus should potentially be taken into account for precision dairy farming management.     

Prolactin in blood plasma and milk of buffalo during estrous cycle and early pregnancy

Concentration of prolactin was measured by radioimmunoassay for 11 primiparous and 16 multiparous buffalo. Prolactin concentration of blood plasma on day of insemination was about 200 ng/ml for primiparous and about 315 ng/ml for multiparous animals and fluctuated between 130 and 200 ng/ml for primiparous and between 250 and 345 ng/ml for multiparous pregnant animals. For the nonpregnant group prolactin fluctuated between 145 and 240 ng/ml for primiparous and between 210 and 310 ng/ml for multiparous animals with minor elevations 1 to 2 days before estrus. Concentration of prolactin of milk was not significantly different from that of plasma and was positively correlated .68 for nonpregnant and .93 for pregnant animals.     

Bovine vaginal circulation: changes during estrous cycle.

Vaginal thermal conductance was measured in 12 heifers and 7 cows with a gradient layer heat flow probe. Values rose for 4 to 5 days prior to day of behavioral estrus (day 0), with a peak on days --2 and --1, and then declined from day 0 to +5. Curves for heifers were higher than those for cows although there was no evidence that they were not parallel. Changes during the cycle appear to result from estrogen-induced alterations in blood flow rate in vaginal tissues.     

The composition of milk fat.

Bovine milk contains about 3.5 to 5% total lipid, existing as emulsified globules 2 to 4 microns in diameter and coated with a membrane derived from the secreting cell. In homogenized milk, the coat is mostly casein. About 98% or more of the lipid is triacylglycerol, which is found in the globule. Phospholipids are about .5 to 1% of total lipids, and sterols are .2 to .5%. These are mostly located in the globule membrane. Cholesterol is the major sterol at 10 to 20 mg/dl. Data are presented on the membrane and the emulsion. Bovine milk contains substantial quantities of C4:0 to C10:0, about 2% each of C18:2 and trans-C18:1, and almost no other long-chain polyunsaturated fatty acids. The fatty acid composition is not altered by ordinary changes in diet. The triacylglycerol structure is unique, with much of the C4:0 to C10:0 at sn-3. The effects of milk cholesterol and fatty acids on human blood cholesterol levels and nonnutritive roles of some microlipids are discussed.     

Molecular approaches to analysing the microbial composition of raw milk and raw milk cheese

The availability and application of culture-independent tools that enable a detailed investigation of the microbiota and microbial biodiversity of food systems has had a major impact on food microbiology. This review focuses on the application of DNA-based technologies, such as denaturing gradient gel electrophoresis (DGGE), temporal temperature gradient gel electrophoresis (TTGE), single stranded conformation polymorphisms (SSCP), the polymerase chain reaction (PCR) and others, to investigate the diversity, dynamics and identity of microbes in dairy products from raw milk. Here, we will highlight the benefits associated with culture-independent methods which include enhanced sensitivity, rapidity and the detection of microorganisms not previously associated with such products.     

Effect of feed on the composition of milk fat.

Researchers attending the Wisconsin Milk Board 1988 Milk Fat Roundtable indicated that the ideal nutritional milk fat would contain 10% polyunsaturated fatty acids, 8% saturated fatty acids, and 82% monounsaturated fatty acids. This cannot be accomplished by modifying diets of lactating cows. Monounsaturated fatty acid (C18:1) content can be increased by 50 to 80% and may approach 50% of milk fatty acids by feeding lipids rich in 18-carbon fatty acids. Because of ruminal hydrogenation and intestinal and mammary desaturase activity, degree of unsaturation of dietary 18-carbon fatty acids is not critical in influencing milk fat C18:1. Feeding low roughage diets increases the proportion of C18:1 in milk fat, and effects of feeding low roughage diets and lipid may be additive. Palmitic acid (C16:0) content of milk fat can be reduced by 20 to 40% unless the supplemented lipid is rich in C16:0. Milk fat alteration is dependent on the level of lipid supplementation. Limited evidence indicates frequency of lipid feeding and physical form of oil (free oil vs. oilseed), and heat treatment of oilseeds has relatively little influence on modification of milk fat. Significant changes in milk fat composition can be achieved on farm via nutritional modifications.     

Altered vocalization rate during the estrous cycle in dairy cattle

Correct detection of estrus is a problem in dairy herds. In practice, several procedures exist for detection of estrus besides conventional visual observation by humans. These procedures deliver very different results regarding detection of estrus. It is known that the calls of female mammals can contain information about reproductive status. It is also suspected that the vocalizations of cattle contain information about age, sex, dominance status, and stage in the estrous cycle. In the present study, a methodology for the continuous automatic recording of vocalization of heifers during the periestrous period is presented. It was shown in 10 tethered heifers that the estrous climax results in an increase in vocalization rate. Vocalization rate of heifers increased approximately 84% from d −2 to 0 (related to observed estrus) and approximately 59% from d −1 to d 0. After d 0, vocalization rate decreased about 79%. Increased vocalization was correlated with the visual observation of estrus by humans. We also found 2 different structures in the vocalization of heifers. The harmonic structure showed regular frequency bands, whereas the nonharmonic structure was noisy. The hypothesis that the disharmonic structure increases near the estrous climax was confirmed. Hence, it seems possible to get information about stage of the estrous cycle of dairy cattle by means of monitoring vocalization. The presented method of automatically detecting the rate of cattle vocalization (patent pending) could be used solely or in combination with other automated systems for detecting estrus and could considerably increase current estrus detection rates once its applicability can be demonstrated in nontethered cattle.     

Effects of feeding fish meal to cows on digestibility, milk production, and milk composition.

Holstein cows in early lactation, producing about 30 kg/d of milk, were fed high energy diets containing 5% Megalac. Three protein treatments, soybean meal diet (16% CP), fish meal diet (16% CP), and soybean meal-fish meal diet (20% CP) were compared in a change-over design. Digestibilities of DM, gross energy, CP, and ADF were not affected significantly by protein treatments. The fish meal diet decreased DMI but increased milk and SCM production compared with the soybean meal diet. Daily production of milk, SCM, and milk components (fat, protein, and lactose) were highest and BW gain lowest for the high protein soybean meal-fish meal diet. The fish meal and soybean meal-fish meal diets increased fat percentage but decreased lactose percentage of milk compared with soybean meal diet. This suggests that, for each diet, the energy supply was adequate, and the observed changes were the effects of protein (i.e., AA) supply to the cows. Thus, there seems to be good reason to feed a good quality undegradable protein like fish meal to cows producing more than 30 kg/d of milk.     

Influence of environmental heat on peripheral plasma progesterone and cortisol during the bovine estrous cycle.

Plasm progesterone and cortisol were measured in jugular blood by competitive protein-binding assay. Six cycling, estrus-synchronized Guernsey heifers were followed for four consecutive estrous cycles under two controlled temperature (18.2 C, 55% relative humidity; and 33.5 C, 55% relative humidity) conditions. Prolonged exposure to heat of Guernsey heifers increased plasma progesterone on days 2 to 19 of the first cycle and only on days 2 to 8 of the second cycle. However, heat stress depressed plasma cortisol in both cycles and reduced the correlation coefficient between these steroids relative to specific stages of the estrous cycle.     

Cation concentrations in fluid from the oviduct ampulla and isthmus of cows during the estrous cycle.

To detect variations in oviduct fluid cation concentrations, Ca++, Mg++, K+, and Na+ were determined for daily samples of blood serum and bovine oviduct fluid collected from indwelling isthmic and ampullary catheters. Isthmic oviduct fluid Ca++ concentration was significantly greater than that in ampullary fluid, particularly around estrus and ovulation. Maximum Ca++ concentrations found in isthmic oviduct fluid at estrus (2.57 +/- .22 mM) and at ovulation (2.50 +/- .29 mM) were similar to those of medium used for in vitro capacitation of bovine sperm. Concentrations of Mg++ in oviduct fluid differed significantly by estrous cycle stage, but not by oviduct region, and were consistently lower than those detected in serum. No relationships were found for K+ or Na+ with respect to region or stage, but K+ was generally higher in oviduct fluid than in serum. The concentration of K+ averaged over stage and region (4.46 +/- .13 mM) and the K+:Na+ ratio (.032 +/- .002) were similar to those reported in bovine in vitro capacitating and fertilizing media. Concentrations of Ca++ and Na+ from peritoneal fluid from nonstaged cows were similar to those of oviduct fluid or serum. The Mg++ concentration was greater, and K+ concentration was less, in peritoneal than in oviduct fluid.     

Use of milk fatty acids composition to discriminate area of origin of bulk milk

The fatty acid composition of cow milk, collected in a survey from 19 dairy farms in the border area between Italy and Slovenia, was investigated for 2 consecutive years (2005 and 2006) to assess the possibility of discriminating the area of the origin of the milk. Farms were selected based on diet, animal breed, and farm management to represent the local variability of the systems. In Slovenian farms, grass silage and hay prevailed over corn silage and concentrate feeds, whereas in Italian farms, hay and concentrates were the predominant components of the diet. Fifty-three fatty acids were separated and quantified in Italian and Slovenian milks. Saturated fatty acids represented the most abundant class, followed by monounsaturated and polyunsaturated fatty acids. Significant differences were observed between Italian and Slovenian milks for the concentration of 40 fatty acids, whereas significant differences were observed between years of production for 15 fatty acids. Discriminant analysis was used to identify a classification criterion of milk, using country and year of production as grouping variables. Considering statistical results and the scatter plot of the scores of the first 2 functions, the best discriminant criteria were those based on unsaturated fatty acids and on fatty acids with several carbon atoms ≥18.     

几种酵母菌添加剂对奶牛产奶量及乳成分的影响

将54头高产中国荷斯坦奶牛随机分为6组，1组基础对照组，5组（A，B，C，D，E）试验组，试验组在基础日粮的水平上添加15g不同型号的酵母菌制剂，预试期2周，正试期为6周。结果表明：不同型号的酵母菌对奶牛产奶量和奶成分有不同程度的影响，其中C和E组奶牛的产奶量分别比对照组有所增加，B和D组的产奶量与对照组相比增加显著（P〈0．05），A组则有所下降；不同型号的酵母菌制剂对牛乳成分也有不同程度的影响，试验组B，D，E组乳脂日产量比对照组有增加，并且差异显著（P〈0．05）；E组乳脂率增加，差异显著；蛋白质日产量除A组无显著性差异（P〉0．05），B，C，D，E组相比对照组都有所增加，其中C和E组相比对照组，差异显著（P〈0．05）；试验组的乳糖、非脂固形物产量与对照组没有显著差异（P〉0．05）；各试验组的所生产牛奶的比重、冰点、酸度与对照组无显著差异，但试验组的酸度除D组外均比对照组有所提高，乳中体细胞数均比对照组低，其中酵母菌C和D能显著减少乳中体细胞数（P〈0．05）。     

水牛乳蛋白质的组成

分析了摩拉水牛（M）、尼里-拉菲水牛（N）、一代杂交水牛（F1）、二代杂交水牛（F2）和高代杂交水牛（Fh）5个品代水牛的乳蛋白主要组分的相对百分比含量．同时分析了总氨基酸组成及钙、磷含量。结果表明，水牛乳蛋白的主要组分有：α-乳清蛋白（α-LA）、β-乳球蛋白（β-LG）、免疫球蛋白轻链（IgG—L）和重链（IgG—H）、αs1-酪蛋白（αs1-CN）、αs2-酪蛋白（αs2-CN），β-酪蛋白（β-CN）、κ-酪蛋白（κ—CN）、血清白蛋白（SA）和乳铁蛋白（LF）等；CN在水牛乳蛋白中占优势，与荷斯坦牛乳相比，水牛乳中CN的质量分数稍低，而且各品代水牛乳中的CN有显著性差异（P〈0．05）；乳清蛋白中β-LG含量最高；杂交水牛乳蛋白高于纯种摩拉水牛和尼里一拉菲水牛，差异显著（P〈0．05）：各品代水牛乳的氨基酸比例比较接近；不同品代水牛乳中钙、磷含量没有显著性差异。     

Collection of fore and hind milk from the sow and the changes in milk composition during suckling.

A new sampling method for the collection of fore and hind milk from the sow has been developed which resembles normal milk removal by the piglet, yet overcomes the difficulties of collecting milk that is available for only a short time (10-20 s) at each let-down. Samples of hind milk were collected immediately after the completion of a successful sucking, while the fore milk was collected at the beginning of the next natural let-down. Modification of existing assays for fat, protein and lactose was required to provide rapid analysis of the small volumes (less than 0.5 ml) of milk collected using this procedure, and these methods were validated by comparison with reference methods. Total solids and the concentration of fat in whole milk, and protein and lactose in skim milk, were measured in fore and hind milk collected from 4, 20, 12 and 12 sows respectively, 6-11 d post partum. For fore milk, the results (mean +/- SD (n)) were: total solids, 199.9 +/- 9.9 g/l (8); fat, 96.7 +/- 13.9 g/l (41), protein, 47.7 +/- 4.5 g/l (27) and lactose, 58.3 +/- 4.0 g/l (27). In hind milk, there was a significant increase in the concentration of fat (15.3 g/l, P less than 0.001, n = 41) which was reflected by a significant increase in total solids (14.7 g/l, P less than 0.001, n = 8) and calculated energy (511 kJ/l, P less than 0.001, n = 27), but there was no significant difference in the concentration of either protein or lactose. This increase in milk fat during milk let-down is in contrast to the results of most previous studies in the sow and is discussed in terms of the possible mechanisms that may cause the concentration of fat to increase as milk is removed from the mammary gland.