Cows Of Different Breeds Research Articles

Epidemiological Studies on Subclinical Mastitis in Dairy cows in Assiut Governorate

In this investigation, some epidemiological studies were run on subclinical mastitis for totally 350 dairy cows of different breeds, ages and distributed in different villages in Assiut governorate, Assiut, Egypt, along a whole year (during the period from June 2006 till July 2007) through field screening surveys by using of the California mastitis test (CMT) for each quarter milk sample followed by bacteriological examination to identify the major causative agents of intramammary infection (IMI). The dairy cows were differed from the breed point of view as 230 Holstein Friesian breed and 120 native breed. Also, they were differed from the age point of view as a group of 95 cows aged from 2 to 4 years old and another group of 255 cow aged from 5 to 8 years old. All dairy cows were apparently healthy with clinically sound udder secreting apparently normal milk. All the cows lived nearly under the same conditions of breeding from the habitat, hygiene and feeding systems. The obtained results revealed that 67 cows (19.14%) had 80 infected quarters (5.71%). It was found that the most frequently major causative agents isolated were Staphylococcus aureus, Streptococcus agalactiae and Escherichia coli from the positive CMT samples with prevalence 52.5, 31.25 and 16.25%, respectively. With studying the breed factor, it was found Friesian breed was sensitive towards infection (20.43% at the cow level and 6.09% at the quarter level) than of native breed (16.67% at the cow level and 5% at the quarter level). It was also noticed that the prevalence of subclinical mastitis in hot weather as during summer (9.14% at the cow level and 2.64% at the quarter level) and during spring (4.86% at the cow level and 1.36% at the quarter level) was higher than in cold weather as during winter (2% at the cow level and 0.64% at the quarter level) and during autumn (3.14% at the cow level and 1.07% at the quarter level). In relation to age susceptibility, 5-8 years old cows (15.43% at the cow level and 4.36% at the quarter level) were susceptible than those of 2-4 years (3.71% at the cow level and 1.36% at the quarter level). The degree of quarter attack according to positive CMT was varied from 35 quarters (2.50%) showed degree (+++), to 45 ones (3.22%) showed degree (++), to 120 ones (8.57%) showed degree (+) and the rest (85.71%) showed degree (-). The obtained results threw the light on the epidemiology of subclinical mastitis in Assiut villages and provided an importance of the CMT for diagnosis of subclinical mastitis due to it is a reliable, easy, rapid and cheap tool helping in diagnosis and controlling the disease because it directs attention to individual mammary quarter that is secreting milk of high somatic cell content (SCC). Programs for control of subclinical mastitis may be planned around the routine examination of all lactating cows, and consequently early treatment can be applied towards positive cases rapidly for preventing their conversion towards clinical form among dairy cows and for protecting the herd health, milk hygiene and consequently the consumer health.

Comparison of body measurements of beef cows of different breeds

Abstract. Body measurements of 110 beef cows of 9 breeds (Hungarian Simmental, Hereford, Aberdeen Angus, Red Angus, Lincoln Red, Shaver, Charolais, Limousin and Blonde d’Aquitaine) were taken in December 2004. The absolute, relative measurements and measurement indices moreover correlations between age, live weight and measurements were evaluated and compared for the mentioned breeds. Animals in study were born between 1989 and 2002, kept on the same condition on peat-bog soil pasture at Keszthely. Significant differences (P<0.05) were found among breeds in most of the body measurements. Blonde d’ Aquitaine was the heaviest in live weight (638 kg), highest as for the height at withers (142.5 cm), height at rump (146.6 cm) and length of the body (151.5 cm). Limousin had longest measurements as for the length of the rump (47.4 cm) and width of the rump (58.3 cm). Shaver had the longest width between shoulders (52.9 cm) and width of the head (25.1 cm) while Lincoln Red the longest length of the head (52.8 cm). The correlations between live weight and measurements were medium or strong positive (r = 0.40–0.83), between age and measurements slight positive (r = 0.01–0.46), among the different measurements medium or strong positive (r = 0.22–0.81).

Metabolism and Udder Health at Dry-Off in Cows of Different Breeds and Production Levels

The effects of milk yield at dry-off (DO), different calving intervals (CI; 12 and 15 mo) and breed on metabolism and udder health were studied in 56 primiparous and multiparous cows of the Swedish Red and White (SRB) and Swedish Holstein (SH) breeds. The cows were dried off 55±5 d prior to expected parturition. They were fed 4kg of DM as silage and wheat straw ad libitum for 5 d, and were milked in the morning of d 2 and 5. Depending on their daily milk yield, the cows were divided into 3 numerically equal groups on 2 d during the week prior to DO: low (LY; 5.0 to 11.4kg of milk/d, n=19), medium (MY; 11.5 to 17.7kg of milk/d, n=19), and high (HY; 17.8 to 29.5kg of milk/d, n=18). The plasma cortisol concentration increased during DO only in MY and HY cows. Plasma nonesterified fatty acids increased during DO in all groups, but the maximum nonesterified fatty acid concentration was related to the milk yield prior to DO. The plasma glucose level during the DO period was not significantly affected by yield, but the insulin concentration decreased after DO, with a more pronounced drop in the HY group. The CI 15-mo group had a higher glucose level and tended to have a higher insulin level in plasma than the CI 12-mo group before DO. They also had a higher body condition than the CI 12-mo group. The results indicate that the CI 15-mo cows had a more positive nutrient balance. There were no effects of CI on milk production or composition during DO. The SRB and SH breeds did not differ in any of the measured plasma parameters or milk production. However, the lower somatic cell counts in SRB than in SH observed before and during DO, as well as after parturition, were attributed to being an effect of breed. The proportion of cows with intramammary infections (IMI) was significantly lower just after calving in the LY group than in the other yield groups. At 2 and 3 wk after DO, significantly fewer cows in the LY group had open teat canals compared with the HY and MY groups, respectively, but teat-end condition did not differ between yield groups. The yield before DO did not significantly influence the somatic cell counts during the first 4 wk after parturition or the presence of IMI 4 wk after parturition. We concluded that in the present study, higher milk yield prior to DO gave rise to a more pronounced metabolic response and a higher risk of contracting IMI during the dry period, at calving, or both, but yield at DO did not have any long-term effects on udder health. A prolonged CI did not facilitate a rapid decrease in milk production. The SRB and SH breeds responded equally in decreasing the milk production during DO, but the SRB breed had lower somatic cell counts.

Iodine concentrations in cow's milk in Central and Northern Bohemia

Iodine deficiency and related risks of medical and/or developmental disorders in humans are a worldwide problem. In the last years, Czech endocrinologists and paediatricians have observed a significant increase in the occurrence of goitre in children and adolescents caused by a low dietary intake of iodine. Given the low consumption of seafood, milk and dairy products are the main sources of iodine in theCzechRepublic. Iodine contents of milk of dairy cows of different breeds from seven farms located in Central andNorthern Bohemia were studied over a period of 17 months (April 2000 through August 2001). Iodine content was determined by high-performance liquid chromatography with electrochemical detection (HPLC-ECD) based on IDF Standard 167 (1994), following alkaline mineralization of the sample. An analysis of the certified reference material CRM 063 was used to examine the accuracy of determination. Two-way analysis of variance (ANOVA) with and without replications, including Scheffe’s comparison at a 5% level of significance, was used for statistical evaluation of experimental data. The iodine content of milk ranged from 147 to 605 µg/kg (mean 251  110 µg/kg) during the winter season, and from 35 to 484 µg/kg (mean 212  104 µg/kg) during the summer season. The mean iodine concentration in all samples of milk during the studied period was 225  109 μg/kg.The wide range of iodine concentrations is connected with differences in iodine saturation of dairy cows and it is a result of multiple factors. Iodine reserves in the soil play an important role and influence the content of iodine in feeds for dairy cows and thereby the iodine levels in milk. The presence of goitrogenic substances in feed for dairy cows is another important factor. The iodine content was found to be statistically significantly lower in the milk from dairy cows fed a diet enriched with rapeseed cakes compared to that of dairy cows on a diet without rapeseed cake. Dairy cows on farm F6, which were fed maize silage without added rapeseed cake during winter, had a statistically higher iodine content in milk during the winter season compared to summer, when they were fed fresh fodder. Fresh fodder is supposed to contain goitrogenic substances which significantly reduce iodine levels in milk. This opinion is supported by experimental findings that the date of milk sample collection has no statistically significant influence on milk iodine levels if the dairy cows are fed a diet containing added rapeseed cake (farms F1, F2, F3, and F4) throughout the year. Compared to the other farms, statistically significantly higher milk iodine content was found on farm F5. The mean iodine content in milk from farm F5 was 425  74 μg/kg during the studied period. The main cause is probably that the diet contained no rapeseed cake.  

Use of linear discriminant analysis to characterise three dairy cattle breeds on the basis of several milk characteristics

To characterise individuals of differents breeds on the basis of milk composition and to identify the best set of variables a linear discriminant analysis (LDA), on 14 milk production traits, was performed on milk samples from 199 cows of different breeds (respectively, 127 subjects were Italian Friesians (IF), 62 were German Friesians (GF), and 10 were Jerseys (J) and all came from the same breeding farm in Tuscany. The variables were: test day milk yield (kg milk), % Fat, % Protein,% Lactose, % solid non fat (SNF), % total solid (TS), pH and titratable acidity (TA); five rheological variables: r, k20, a30, a45, and somatic cell counts /ml (SCC); and one hygiene-related variable: total bacterial count (TBC). The analysis performed on the 14 variables, with regard to the three breeds, allowed us to identify 10 of these as variables useful for discrimination (leaving out kg milk, pH, a45, and TBC). The most important variables were the percentage of Fat and TS for the first canonical variate and SNF, Lactose and Protein for the second. Fat and TS play an important role since they present significant values (even if opposite sign) in the two variates. The resulting classification of subjects was satisfactory: 79% of the Italian Friesians, 73% of German Friesians and 100% of the Jersey cows were classified correctly.

Peripheral circulating insulin-like growth factor-I and -II in cattle.

Interrelationships between circulating concentrations of the insulin-like growth factors (IGF-I and IGF-II) were investigated in 235 blood samples taken from 145 healthy beef or dairy calves, bulls and cows of different breeds and ages. Autoradiography of Western ligand blots indicated different IGF binding protein (IGFBP) profiles between sera from different categories of cattle. Each IGF radioimmunoassay was validated by determining the effects of IGFBPs, ligand and contraligand, as well as serial dilution and comparison with results obtained after molecular sieve chromatography in acid. In female cattle mean values for IGF-I varied from 5.1 nmol/l in postparturient Holstein cows to 18.5-20.5 nmol/l in growing beef heifers, while mean IGF-II concentrations ranged from 30.0 nmol/l in the cows to 14.7-15.7 nmol/l in the beef heifer calves. In male cattle mean serum IGF-I ranged widely from 8.2 nmol/l in 1-day-old Holstein calves to 67.4 nmol/l in 16-month-old Simmental-type bulls. Mean IGF-II concentrations decreased from 22.9 nmol/l in 1-day-old Holstein bull calves to 11.9 nmol/l in 12-month-old beef bulls. Thus, total molar IGF concentrations were fairly stable in female cattle (24.7-35.1 nmol/l) but extended from 27.3 nmol/l to 81.8 nmol/l in the male cattle. The tendency for a reciprocal relationship between serum concentrations of these growth factors was most obvious in the periparturient cows.

EVALUATION OF LIFETIME PRODUCTION OF TOP COWS IN DIFFERENT DAIRY BREEDS

Cows of different breeds with high lifetime production were analysed in order to choose the best producers for embryo donors. The cows were ranked based on their milk protein yield, and a rank correlation was calculated between milk and protein yield and age. The probability of a correlation breaker was also investigated. In the Swiss Simmental breed it was found that the lower the protein production, the lower the correlation. This tendency was characteristic for the Brown Swiss population, too. In the first Osnabrück Holstein subpopulation a close correlation (0.74) was found, but not in the other two. The ratio of correlation breakers in the three subpopulations was 12.5%, 33.3% and 56.3%. In populations of German Black & White and Red & White the correlation was very close (0.9 and 0.84, respectively). The ratio of correlation breakers was 26.7% and 22.2%. In the Hungarian Holstein population the correlation was weak (0.29), so the ratio of correlation breakers was relatively high. The value of the rank correlation coefficient between the milk fat and milk quantity of the top cows of the Jersey breed was 0.26, indicating a weak correlation. The ratio of correlation breakers was 36.4%.

Milking characteristics in dairy cows of different breeds from different farms and during the course of lactation

SummaryMilking characteristics were studied in 106 cows belonging to four breeds, and housed in four farms. Cows were either milked without any, or after a 1‐min pre‐milking udder stimulation. Milk yields were not influenced by pre‐milking stimulation, whereas average and peak milk‐flow rates were tendentially greater with than without stimulation, resulting in shorter milking times. However, the time spent on pre‐stimulation was never completely compensated for by faster milking. Bimodal milk flow, indicating delayed milk ejection, was seen in about 70% of milkings without stimulation and in only 13% of SI × RH on the FRS farm also after pre‐stimulation. The size of the mammary cisternal cavities on ultrasound, and most of the evaluated milking characteristics, were not different between farms and breeds. Milk yield, milking time and average flow rate decreased during the course of lactation. Total and main milking times were generally snorter with than without stimulation. Average flow rate was always numerically higher with than without stimulation, but was only significant in late lactation. The time to reach peak flow rate was similar with and without stimulation in early lactation, and was significantly and progressively prolonged without stimulation in mid and late lactation. The interruption of milk‐flow increase in bimodal milk‐flow curves was prolonged during the course of lactation. Increasing effects of pre‐stimulation on milking characteristics towards the end of lactation are indicated.ZusammenfassungMilchabgabeverhalten von Milchkühen verschiedener Rassen und Betriebe sowie während des LaktationsverlaufsIn der vorliegenden Untersuchung wurde das Milchabgabeverhalten von 106 Milchkühen untersucht, die vier verschiedenen Rassen angehörten und auf vier verschiedenen Betrieben gehalten wurden. Die Kühe wurden entweder nach 1‐minütiger manueller Vorstimulation oder ohne jegliche Eutervorbereitung gemolken. Während die Gemelksmenge durch die Stimulation unbeeinflußt blieb, waren Durchschnittsminutengemelk und höchster Milchfluß tendenziell beim Melken mit Stimulation erhöht, woraus auch kürzere Melkzeiten resultierten. Allerdings wurde die Vorstimulationszeit durch die Melkzeitverkürzung nicht kompensiert. Ein bimodaler Milchflußverlauf trat in 70% aller Melkungen ohne Vorstimulation auf, während beim Melken mit Vorstimulation nur bei 13% der SIxRH‐Tiere des Betriebes FRS bimodale Milchflußkurven festgestellt wurden. Die Größe der Zisternenhohlräume (durch Ultraschall vermessen) zeigte keine Betriebs‐und Rassenunterschiede. Milchmenge, Melkzeit und Durchschnittsminutengemelk nahmen im Verlauf der Laktation ab. Gesamt‐und Hauptmelkzeiten waren in alien Laktationsstadien kürzer mit als ohne Vorstimulation. Das Durchschnittsminutengemelk war in alien Stadien numerisch, signifikant aber nur am Laktationsende, höher mit als ohne Stimulation. Die Zeit bis zum Erreichen des Milchflußmaximums war am Anfang der Laktation mit und ohne Vorstimulation gleich, war aber im weiteren Laktationsverlauf progressiv länger beim Melken ohne Vorstimulation. Die Unterbrechung des Milchflußanstiegs bei bimodalen Milchflußkurven nahm im Laktationsverlauf zu. Zusammenfassend war eine zunehmende Bedeutung der Vorstimulation für das Milchabgabeverhalten gegen Laktationsende zu verzeichnen.

The effect of treatment of dairy cows of different breeds with recombinantly derived bovine somatotropin in a sustained-delivery vehicle

After calving 16 Friesian, 16 Jersey and 16 Dutch Red and White cows were taken into a 252-day experiment to determine the response in milk production, body weight and feed intake to the administration of somidobove (recombinantly derived bovine somatotropin) in a sustained-delivery vehicle. The experiment was divided into an 84 days preliminary period and six consecutive 28-day treatment periods. Four treatments were used: an untreated control and 3 different levels of somatotropin, 320, 640 and 960 mg in a sustained-delivery vehicle, administered once every 28 days by subcutaneous injection. Animals were housed and individually fed ad libitum a complete diet of 50% concentrates and 50% roughage. For none of the analysed characteristics a significant breed × treatment interaction was detected. The 640-mg dosage gave optimum results: in the treatment period the calculated milk energy output increased on an average 19% in Dutch Red and White, Jersey and Friesian cows by an increase in milk yield (3.3 kg) and fat percentage (0.24%). Treatment with somatotropin did not affect protein and lactose percentage, somatic cell count, calcium, magnesium and phosphorus levels in milk. Nonesterified fatty acids (NEFA) in milk of treated cows tended to be lower than in control cows. Glucose, insulin and thyroxin levels in plasma were not affected by somatotropin treatment. The plasma levels of NEFA tended to be higher after the first 3 injections, and that of 3-hydroxybutyrate after the first injection with the higher and medium dosages. The level of urea tended to be lower in treated cows; somatotropin was significantly higher in treated cows. The fluctuations in milk yield and milk composition over a 28-day period indicate that the release characteristics of the release system should be improved to get a more natural lactation curve for treated animals.

Long Term Studies on Bone Mineral Changes During Different Lactations in Swedish Dairy Cattle

Changes in the bone mineral content (BMG) during the first 4 lactations were continuously studied between July 1977 and February 1982 in a total number of 103 dairy cows of different breeds and rearing intensities. The BMG was measured by dichromatic photon absorptiometry in 2 coccygeal vertebrae. Although great individual variations were found, the changes in BMG during the lactation followed a typical pattern with high values during the dry period and low values after calving and during mid-lactation. The influence of body weight on the BMC value is discussed. The changes in BMC were more accentuated during the first lactation, as compared to the subsequent lactations. This could indicate a metabolically more active skeleton in younger cows. In this study no difference in BMC pattern was observed between cows affected or not affected by parturient paresis.

Optimal Culling Strategies for Dairy Cows of Different Breeds

Dynamic programming models were developed to optimize culling decisions for Holstein, Jersey, Guernsey, and Ayrshire cows. Parameters of individual breeds for milk yield, milk fat percent, body weight, and disposal reasons were considered. Replacement heifers were allowed to vary in these traits by a probability distribution function. Maximum discounted returns over major variable costs were computed for 10-yr planning for each breed for five prices.Regardless of prices, Holsteins had the highest weighted average value of discounted returns over variable costs followed in decreasing order by Ayrshires, Guernseys, and Jerseys. Effects of the traits on these values were determined by response surfaces. Holsteins and, to a less extent, Ayrshires, would benefit from increased emphasis on milk fat percent as an effective method of increasing discounted 10-yr returns over variable costs. Values for the Jersey and Guernsey breeds would increase substantially if major emphasis were placed on milk yield. Little would be gained by increases in milk fat percent for these two breeds. These results were consistent over changes in prices of milk and feed.Within breeds, body weight had little effect on response surfaces and had only a slight positive effect on 10-yr discounted returns over variable costs. Body weight could be conveniently omitted from the models.

Sialic acid and hexosamine concentrations in cervical mucus in different breeds of cows and buffalo at oestrus

Gibbons & Mattner (1966) tentatively suggested that cross-linkage of long flexible glycoprotein molecules in cervical mucus occurs through sialic acid (N-acetylneuraminic acid) residues because the extent of cross-linking appears to be related to the level of sialic acid in mucus. Hexosamines represent another important class of organic constituents of cervical mucus. According to Kurzrok (1958), the appearance of glucosamine in cervical mucus signifies the ovulatory phase of the menstrual cycle in women, and changes in sialic acid concentration in human cervical mucus have been associated with sperm receptivity (Carlborg & Gemzell, 1969). Sialic acid and hexosamine concentrations in cervical mucus are influenced by the circulatory level of oestrogen (Kurzrok, 1958; Carlborg & Gemzell, 1969). Oestrogen levels at oestrus in buffaloes and cows of different breeds vary considerably, and are reflected in conspicuous differences in the volume and consistency of the cervical mucus. We have therefore studied the concentrations at oestrus of sialic acid and hexosamine in the cervical mucus of cows and buffaloes of different breeds.

Blood Lipid Changes in Cows of Different Breeds Fed Rations Depressing Milk Fat Test

Blood lipid changes in response to a high-grain ration that depressed milk fat test were studied in four cows each of the Guernsey, Holstein, and Jersey breeds. Milk fat percentage decreased from 4.9 to 3.7 in Guernseys, 3.3 to 2.2 in Holsteins, and 5.3 to 4.3 in Jerseys. Protein content of the milk increased. Although there were some significant breed differences in levels of the blood lipid components, within-breed variations were considerable. Plasma levels of phospholipids, cholesterol esters, free cholesterol, free fatty acids, and acetate decreased during the experimental period in all the breeds. Over-all mean arteriovenous differences exceeded 10% of the arterial level only in acetate, triglycerides, and ketone bodies.Arteriovenous differences for acetate decreased significantly during the experimental period to almost one-third of the original level, whereas the uptake of triglycerides and ketone bodies was not changed significantly. Levels of blood plasma acetate and triglycerides and blood ketone bodies during the post-experimental period exceeded the original levels and were accompanied by arteriovenous differences exceeding the original levels. The milk fat test recovered to the original level 3 wk after returning to a normal ration. Higher levels of propionate and lower levels of acetate in the rumen during the experimental period appeared to be the key factors responsible for the observed changes.

Quantitative analysis of milk and other emulsions by infra-red absorption.

A BEAM of radiation passing through an emulsion can be attenuated by both absorption and scattering effects. Quantitative absorption measurements on such systems are only reliable when the effects of scattering are made small in comparison with those of absorption ; that is, when the ratio of the refractive indices of the two phases approaches unity and when the size of particle is considerably less than the wave-length. For milk, the ratio of the fat/serum refractive indices is approximately 1.1 and since the mean fat globule diameter of homogenized milk samples is about 1µ, scattering effects will be expected to be small at wave-lengths greater than 5µ. Homogenization will therefore reduce photometric errors caused by variations in the sizes of fat globules of milk samples from cows of different breeds and in different states of lactation.

Variation in the Constituents of Milk Under Arizona Conditions. II. Influence of the Month of Lactation in Cows of Different Breeds

Summary The results of analyses of 362 samples of milk were compiled and presented graphically by breeds and compared with results obtained by the Illinois Station. The samples were taken 1 day each month throughout the lactation periods and results were compiled by month of lactation. (1)The data show steady increases in total solids, serum solids, fat, and protein values after the second month of the lactations, and a slight decrease in the values of the constituents of Guernsey milk during the eighth month. A large percentage of the cows were in the eighth month of their lactation during the spring and summer months. (2)Milk produced under Arizona conditions averaged lower in all constituents than milk produced in Illinois, except for the fat content of milk from the Holstein breed. (3)The serum solids of Jersey milk showed less variation than that of the milk of the other breeds studied, as shown by variation of 0.35 per cent throughout the lactation as compared to 1.08 per cent and 0.65 per cent variations for the Guernsey and Holstein milk, respectively. (4)The total solids, fat, and protein of Holstein milk decreased 3.69, 13.26, and 9.52 per cent from the first to the second month and then increased 7.12, 13.03, and 17.65 per cent, respectively, to the end of the lactation. The milk from Jersey and Guernsey cows showed 2.01 and 4.08 per cent increase in fat from the first to second month. The milk increased in fat 26.51 and 21.81 per cent, respectively, in the remainder of the lactation. The milk from the Jersey and Guernsey cows decreased 1.00 and 0.59 per cent in total solids in the second month and increased 6.40 and 14.09 per cent, respectively, from the second month to the end of the lactation. The protein content of the Jersey milk decreased 11.57 per cent in the first period, while Guernsey milk increased 10.44 per cent. The increases for the latter period were 8.99 and 14.66 per cent for Jersey and Guernsey milk, respectively. (5)The ratio of the fat to serum solids shows that as the lactation advances the fat content is higher in proportion to the serum solids. (6)The ratio of fat to serum solids will vary with individual cows even though the fat test is the same.

Riboflavin Content of Milk Collected in Different Months and Correlated with Other Constituents of the Milk

Summary Riboflavin determinations were made on samples of milk collected at intervals from individual normal cows of different breeds and on different rations. The influences of season and individuality on flavin values were considered. The relationship of flavin content to the concentrations of the following constituents in the milk were tested: vitamin C, loss of C on 72 hours storage at 4° C, carotene, lecithin, fat, protein, phosphatase, leucocytes, mastitis streptococci, odd bacteria, lactose, and chlorine. The average flavin contents in March, April, and May were for Ayrshires 1.17 parts per million, for Holsteins 1.37, for Guernseys 1.53, and for Jerseys 1.73. Milk from cows between 15 days and 10 months after freshening, showed no significant difference in flavin content. The flavin content of milk was slightly higher in July after the cows had been pastured. The climate and ration were not the only important factors which caused variations in the flavin content of milk. The fat is the only constituent of milk for which an approach to a significant consistent relation to flavin was found. It is suggested that flavin may have a role in the production of milk fat.

182. Variations in the protein content of milk during lactation

1. It was planned to study the variations of the protein content of milk during the lactation period.2. The total protein nitrogen and the casein nitrogen were determined by approved methods in about 380 weekly samples of milk taken from twentyseven individual cows of different breeds and at different stages of lactation, from February to July 1937. The albumin+globulin nitrogen was calculated in each case by difference.3. The statistical analysis of the figures was made by the methods of “factorial arrangement” and by “pairing”, and also by the estimation of the 95% probability range of the mean of the figures available for each week of lactation.4. It was found that the percentage of total protein nitrogen decreases very significantly from the beginning until the 4th week of lactation, and then rises slowly until the end of lactation, the rise being more pronounced to wards the end. The same was true for casein nitrogen and for albumin+globulin nitrogen, but with the latter only the decrease at the beginning and the rise at the end were sharp. The rise for the rest of the lactation curve, although it did exist, was very slow.5. The lactation curves for the yield of total protein nitrogen, casein nitrogen and albumin + globulin nitrogen were practically parallel with the lactation curve for the yield of milk.6. The correlations between the yield of milk and the percentages of total protein nitrogen, casein nitrogen and albumin + globulin nitrogen are studied and the correlation tables with all details are given for each. It is noteworthy that the regression lines are not linear and that with a poor milker an increase of 1 lb. in yield of milk corresponds to a relatively high decrease in the percentage of protein nitrogen, whereas with a high milker this decrease is relatively much smaller.7. The correlations between the yield of milk and the yield of total protein nitrogen, casein nitrogen and albumin + globulin nitrogen are examined and the correlation tables are given. It is shown that there is a close correlation between the yield of milk and its protein content, from which the conclusion is drawn that a very low protein food does not decrease the percentage of protein in milk as one might expect, but decreases the yield of milk and increases the percentage of protein in milk. On the other hand, an increase of adequate protein in the ration may raise the yield of milk if it is not at its maximum level.8. It is emphasized that the above conclusions are drawn from a study carried out on a group of cows, and may not be strictly applicable to individual cows.