A Comparative Study of the Proteins of the Colostrum and Milk of the Cow and their Relations to Serum Proteins

High frequency of delayed milk delivery to neonates in tropical beef herds

Beef-calf mortality rates across tropical and subtropical Australia are high, with sub-optimal nutrition in pregnant cows being the primary risk. The nutritional deficiencies associated with calf mortality are the same as those associated with reduced milk yields. Although the highest mortality risk occurs during neonatal life, the role of inadequate milk delivery to beef neonates is not well established. This study investigated the frequency of low milk delivery in tropically adapted neonatal calves and the time for their dams to initiate full lactation in five management groups of Brahman and Droughtmaster calving cows in the dry tropics of northern Queensland, Australia. Change in calf weight in the days following birth was the primary measure of milk uptake. Plasma globulin concentration was used to indicate colostrum uptake. Across management groups, data were available on 250 calves for regression analysis of average daily gain vs. globulin and on 78 for plotting calf growth profiles. Calves had one of two growth profiles, either with immediate high growth from birth (day one) or with high growth delayed until day three. The frequency of delayed growth calves (with inadequate milk intake to gain at least 0.5 kg by day three after birth) was on average 30% across management groups, with management groups ranging 25%-50%. The frequency of calves growing ≤0.2 kg/day to day three was 15%-37%, depending on management group. The frequency of calves growing ≤0.2 kg/day to day five was 7%-20%, depending on management group. Calf globulin explained only 25% of the variation in calf average daily gain. Our study shows that a third of tropically adapted calves may experience a three-day delay to initiation of full lactation by their dams. Although study conditions were relatively benign, any additional risks with milk delivery, such as those that occur widely in tropical and subtropical northern Australia, would place such calves at risk of dehydration and mortality. Calf plasma globulin should not be used as a standalone measure of adequacy of neonatal milk delivery, especially when comparing across herds. This study demonstrates a fundamental problem of high frequency in northern Australia. The underlying risks for delayed milk delivery should be considered in the quest for practical solutions to reduce tropically adapted beef-calf mortalities.

Insulin autoantibodies with high affinity to the bovine milk protein alpha casein

Insulin autoantibodies (IAA) can appear in children within months of introducing solid foods to the diet and before clinical type 1 diabetes. The aim of this study was to determine whether infant dietary antigens could be immunizing agents of IAA. To this end, IAA binding to [(125) I]insulin was competed with food preparations and extracts of foods encountered in the infant diet (milk formulas, bovine milk, wheat flour, fowl meal). Bovine milk powder extracts inhibited IAA-positive samples from six of 53 children (age 0·3-14·0 years) participating in German prospective cohorts. Inhibition in these sera ranged from 23 to 100%. Competition was abolished when hydrolyzed milk powder was used. Competition with protein components of bovine milk found that two of the six milk-reactive sera were inhibited strongly by alpha- and beta-casein; none were inhibited by the milk proteins bovine serum albumin or lactoglobulins. The two casein-reactive sera had high affinity to alpha-casein (1·7×10(9) ; 3·1×10(9)  l/mol), and lesser affinity to beta-casein (4·0×10(8) ; 7·0×10(7)  l/mol) and insulin (2·6×10(8) ; 1·6×10(8)  l/mol). No children with milk-reactive IAA developed autoantibodies to other islet autoantigens or diabetes (median follow-up 9·8 years). These results suggest that autoimmunity to insulin can occur infrequently via cross-reactivity to food proteins, but this form of IAA immunization does not appear to be associated with progression to diabetes.

THE REACTION OF COW'S MILK TO BLOOD SERUM PRECIPITIN

It seems well established that during normal lactation there passes a slight but well defined quantity of blood protein into the udder. When a specific serum precipitin is applied to diluted milk the reaction occurs at a relatively uniform level of dilution. This line may well be considered the normal level of blood protein elimination. In the main the serum protein level is the same when mastitis streptococci are present as when they are absent, provided they are not too numerous. On the other hand it has been shown that when streptococci are present in large numbers the milk while apparently normal reacts at dilutions considerably higher than the normal. In the non-lactating udder, particularly during the latter end of gestation, serum proteins accumulate. Little and Orcutt have shown that certain antibodies tend to become greatly concentrated within the udder. Howe and others have shown that the colostrum of cows is rich in blood proteins. It is to be noted, however, that colostrum while rich in serum proteins usually reacts with serum precipitin to about one-half the titer of the blood serum itself. It may well be that certain proteins of the blood passing into the acini are reabsorbed, leaving a portion of the antigen within the udder. Thus a gradual accumulation of antigen may occur. Shortly after parturition the udder may be drained with a consequent marked fall in serum content. There, however, apparently exists for the next few days considerable permeability of the capillaries for serum proteins. This is borne out by the reaction of the milk to the serum precipitin, since it may react above the normal level for as long as 10 days or 2 weeks after parturition. During the course of inflammation there may occur a considerable outpouring of blood protein. In the severe cases the exudate may give a titer at as great a dilution as the blood serum. In other milder cases where the inflammation may be confined only to the mucosa of the milk cystern, there is usually little that is abnormal in the appearance of the milk. The precipitin test, however, indicates that serum proteins are present in definitely greater concentration than in normal milk. Of practical interest is the effect of heating the milk on the reaction of serum precipitin. Milk heated to a temperature as high as 66°C. for 20 minutes will react at the same dilutions as the raw milk. Milk pasteurized at 68–69°C. for 20 minutes will no longer react. The precipitin test, then, affords a ready means of detecting milk heated above 68–69°C. It is assumed that the precipitin test may have some further practical application. The evidence presented indicates a well defined serum proportion in the milk which may be increased during inflammation of the udder. The experiments in which mastitis exudate was mixed with varying quantities of market milk indicate that such mixtures can readily be detected with serum precipitin. It seems not improbable that some such procedure might be applied as a presumptive test to the product of small herds or to the mixed milk of a number of cows.

THE BACTERICIDAL PROPERTY OF COW'S MILK

The bactericidal activity of fresh raw milk from a number of cows has been tested with the non-hemolytic mastitis streptococcus. By using this organism and other means we were able to rule out the action of agglutinin. The milk of all cows examined inhibited the growth of the streptococcus for definite periods. The length of the inhibition period varied; the milk from some cows prevented growth for 8 hours, that of others for only 4 or 6 hours. The inhibitory action may be as strong in the milk of a young cow in its first lactation period as in that of an old cow known to be resistant to udder infection. It is possible to absorb the streptococcus inhibitory substance by first inoculating the milk with B. bovisepticus. We were unable to show that the substance was increased by artificial immunization of cows with the streptococcus. Whey obtained by the action of sterile rennet solution inhibited the growth of the streptococcus to about the same extent as the milk from which it was obtained. We infer that the substance originates in the udder since it differs from blood alexin in its resistance to heat, it is not increased in the whey although the blood proteins are more concentrated, and it is not increased in the milk when the cows are artificially immunized or repeatedly exposed to natural infection.

Managing the production, storage, and delivery of colostrum

Provision of an adequate immunoglobulin mass to dairy calves is an essential component for survival, health, and future productivity. To prevent FPT of immunity due to suckling of the dam, newborn dairy calves should be removed from the calving area within 30 minutes of birth. First and later lactation cows are suitable colostrum donors, provided they are healthy, well-vaccinated, have had optimal transition management, and an appropriate dry-period length. Early colostrum collection yields an adequate immunoglobulin mass provided that 3 to 4 L of colostrum is fed to the newborn calf. Regular testing for the adequacy of the dairy's colostrum feeding program is an excellent way to prevent calf health problems and identify potential need for CSs or replacement products.

Bovine neonatal immunology

The majority of early, in utero immune development occurs independent of antigen exposure. Only later during development can a fetus respond to antigens, and even then the response depends on the stage of fetal development and the nature of the antigen. At birth, the neonate is rapidly exposed to large numbers of potential pathogens. Although immunocompetent, the neonate is immunonaive and dependent on passively acquired maternal immunoglobulins, immune cells, and other substances from colostrum for protection. Neonates that suffer failure of passive transfer of maternal immunoglobulins may be at increased risk for disease; however, many other factors interact in conjunction with the level of passively acquired immunoglobulin to determine the occurrence of disease. These include, but are not limited to, management, environment, hygiene, infection pressure, virulence of organisms, and antibody specificity. In addition to immunoglobulins, colostrum contains large numbers of immune cells and cytokines. It is thought that the primary role for the cellular component of colostrum is to interact with the development of local immunity and to modulate active immunization of the neonatal intestine. In particular, T lymphocytes are thought to transfer immune functions and secrete cytokines. Although most of the major cytokines have been identified in colostrum and milk, their biologic effects on the neonate have yet to be determined.

Kinins produced from bovine colostrum by kallikrein and saliva

Substances capable of stimulating smooth muscle are produced on the incubation of bovine colostrum with urinary kallikrein or calf saliva. These substances, called urine- and saliva-colostrokinin, have been differentiated from kallidin, substance A and similar smooth muscle activating agents. Saliva-colostrokinin is likely to be formed in the suckling calf. Further, as colostrum became milk, the ability to form colostrokinin diminished. A function for saliva-colostrokinin in the newborn is suggested.