Endogenous production of immunoglobulin IgG1 in newborn calves

Dynamics of serum immunoglobulin G and total protein concentrations in dairy calves during the first 2 weeks of life

The aim of the present study was to describe the dynamics of serum IgG (determined with radial immunodiffusion) and total protein (TP; determined with refractometry) concentrations during the first 16 d of life. Secondary objectives were to evaluate the transfer of passive immunity (TPI) classification at d 1 of life as a conditional factor for the aforementioned dynamics, and to describe over time changes on calves' TPI classification. At a commercial raising operation, 36 calves (19 Holstein, 17 Jersey) were sampled immediately after arrival (d 1) and at d 4, 8, 12 and 16 of life, for serum IgG and TP concentration, and hematocrit determination (HCT). Transfer of passive immunity was categorized based on serum IgG (IgG-Poor: IgG <18 g/L; IgG-Good: IgG 18 to <25 g/L; IgG-Excellent: IgG ≥25 g/L) and TP concentrations (TP-Poor: <5.8 g/dL; TP-Good: 5.8 to <6.2 g/dL; TP-Excellent: ≥6.2 g/dL). Multiple linear regression was used to evaluate serum IgG and TP changes over time, considering the effects of time after birth, breed, HCT, and TPI classification at d 1 of life. At d 1, median serum IgG and TP concentrations were 29.9 g/L and 6.3 g/dL, respectively (interquartile ranges: 21.3-42.3 g/L and 5.6-6.7 g/dL, respectively). Dynamics of serum IgG and TP concentrations were conditional to TPI at d 1 of life. Serum IgG concentration declined over time for IgG-Excellent and IgG-Good calves (18.1 and 4.6 g/L, respectively), but remained constant for IgG-Poor calves. Serum TP concentration declined over time in the 3 TPI groups but it was more marked for TP-Excellent (27%) and TP-Good (19%) than for TP-Poor (14%) calves. At d 1, 83.3% of the calves were classified as IgG-Excellent or IgG-Good, whereas 77.8, 55.6, 41.7, and 58.3% of calves were classified within these categories at d 4, 8, 12, and 16 of life, respectively. Similarly, at d 1, 66.7% of calves were classified as TP-Excellent or TP-Good, whereas 47.2, 36.1, 25.0, and 2.8% were classified within these categories at d 4, 8, 12, and 16 of life, respectively. In summary, our results indicate that serum IgG and TP concentrations decline over 16 d of life, and the decline is associated with TPI classification at d 1 of life. Further studies are needed to determine the biological implications of serum IgG and TP decline after d 1 of life, and to elucidate the factors determining the different dynamics. Our results suggest that current thresholds for TPI classification should be interpreted carefully when the age of calves is unknown or outside the age range used to define those thresholds (>24 h to 7 d).

Invited review: The importance of colostrum in the newborn dairy calf

It is critical that bovine maternal colostrum is fed to newborn calves during their first hours of life. Colostrum is the secretion a cow produces after mammary involution that is rich in various nutrients. In addition to the nutritive value for newborn calves, immunoglobulins are of interest due to their role in developing the naïve immune system of calves at birth. The process by which a calf acquires immunity via absorption of immunoglobulins is defined as passive immunity. When calves consume an adequate amount of immunoglobulins, they are classified as having successful passive immunity (SPI). In contrast, if they are deprived of adequate colostrum, they are considered to have had a failure of transfer of passive immunity (FPI). Transfer of passive immunity is assessed by measuring serum IgG concentrations at 24 to 48 h of age. The major factors that influence whether a calf has SPI or FPI are colostrum IgG concentration, quantity fed, and age of calf at colostrum feeding. Monitoring apparent efficiency of immunoglobulin absorption in calves is often recommended to evaluate overall colostrum management practices. Serum IgG analyses can be determined with direct (radial immunodiffusion) or indirect (refractometry) methods and used to assess SPI or FPI prevalence.

Prevalence and risk factors associated with failure of transfer of passive immunity in spring born beef suckler calves in Great Britain

Calves are born agammaglobulinemic and are dependent on the intake and uptake of immunoglobulins from colostrum for protection against infectious diseases in early life. Failure to absorb sufficient immunoglobulins in the correct timeframe after birth is termed failure of transfer of passive immunity (FPT). FPT has been defined as a serum IgG concentration ([sIgG]) of under 10 g/L in dairy calves, as [sIgG] over 10 g/L has been associated with a decreased risk of mortality and morbidity. In beef calves, a [sIgG] of under 24 g/L has also been shown to be predictive of increased morbidity and mortality. Currently there is limited data relating to the prevalence and risk factors of FPT in the beef sector. This cross-sectional study quantified [sIgG] in 1131 blood samples taken from beef suckler calves born on 84 farms in Great Britain in spring 2018 (mean 13.5 calves sampled per farm, range 3-22). Age of calves at sampling ranged from 1 to 13 days. The estimated prevalence of calves with [sIgG] <10 g/L in this study population was 15 % (n = 145 calves), whilst 37 % (n = 396 calves) calves had a [sIgG] <24 g/L. 22 out of the 84 farms had no calves sampled with [sIgG] <10 g/L. Risk factors predictive of [sIgG] were calculated using generalised linear mixed models, with farm included as a random effect. Calving assistance was significant and increased the likelihood of [sIgG] concentrations <10 g/L and [sIgG] <24 g/L, Odds Ratio (OR) 1.66 (1.05-2.62 95 % CI) and 1.91 (1.33-2.74 95 % CI) respectively. All three levels of assistance with colostrum feeding used in this study were significant for calves having a [sIgG] <24 g/L (Lead to dam OR = 1.85 (1.11-3.06 95 % CI), Bottle/tube fed dam's colostrum OR = 2.35 (1.29-4.30 95 % CI), Bottle/tube fed artificial colostrum OR = 3.78 (1.86-7.70 95 % CI), whilst bottle/tube feeding either dam's or artificial colostrum were also significant for [sIgG] <10 g/L, OR 2.66 (1.32-5.36 95 % CI) and 2.34 (1.09-5.02 95 % CI) respectively. Male calves had a higher likelihood for [sIgG] <10 g/L, OR 1.68 (1.12-2.54 95 % CI) whereas being a twin or being born to a heifer were predictive of having a [sIgG] <24 g/L (OR 3.31 (1.64-6.71 95 % CI), OR 1.57 (1.05-2.35 95 % CI) respectively). This study raises important questions with respect to management practices around calving and highlights the need for reviewing protocols with respect to colostrum assistance and calving assistance on beef farms.

Short communication: Variation in serum immunoglobulin G concentrations from birth to 112 days of age in Holstein calves fed a commercial colostrum replacer or maternal colostrum

Serum IgG concentrations in dairy calves change throughout their first weeks of life, peaking at 24 h and then steadily decreasing until calves begin to produce endogenous IgG. The objective of this study was to observe serum IgG dynamics from birth until 16 wk of life in calves fed either maternal colostrum (MC) or colostrum replacer (CR). A total of 44 Holstein calves were randomly assigned to 1 of the 4 colostrum treatments and followed throughout the study. Treatments consisted of feeding high-quality MC, low-quality MC supplemented with CR, or 1 of 2 distinct levels of IgG concentration from CR. Overall, the interaction between type of colostrum fed and sampling time was significant. Individual differences for this effect were found at d 1, 7, 14, 21, 28, and 98, while the other time points were not different.

Comparison of immunoglobulin G absorption in calves fed maternal colostrum, a commercial whey-based colostrum replacer, or supplemented maternal colostrum

Successful passive transfer of antibodies in neonatal calves can be achieved by feeding an adequate quantity and quality of maternal colostrum (MC) or colostrum replacer (CR). An alternative could be feeding low-quality maternal colostrum (LMC) with added IgG from a CR. The objective of this study was to determine if a commercial whey-based CR product containing low levels of casein (Premolac PLUS Bovine IgG; Zinpro Corporation, Eden Prairie, MN) fed to replace MC or supplement LMC could lead to adequate serum IgG levels and apparent efficiency of absorption (AEA) in neonatal dairy calves. Holstein calves (n = 20 per treatment) were separated from their dam after birth and randomly assigned to be fed 3.79 L of MC (106 g/L of IgG; 401 g of IgG fed), LMC (30 g/L IgG) supplemented with CR (41 g/L IgG; 154 g of IgG total fed; LMC-CR), or 1.3 L of 1 of 2 levels of CR (110 or 150 g of IgG fed; CR-110 or CR-150) within 1.5 h of birth. Colostrum was obtained from the first (MC) or second and third milkings (LMC) of cows from Pennsylvania State University dairy and pooled by source into large batches. Blood samples were taken from calves before colostrum feeding and 24 h after birth and were analyzed for serum total protein, total IgG, hematocrit, and Brix percentage. Calves fed MC had higher 24-h IgG values (means ± SEM) than calves fed LMC-CR (27.04 ± 1.07 vs. 22.33 ± 1.08 mg/mL, respectively). Feeding 150 g of IgG from CR led to higher 24-h serum IgG values than feeding 110 g of IgG (16.90 ± 1.09 vs. 12.79 ± 1.08 mg/mL). Serum IgG levels were different between the CR-fed calves and the calves fed LMC-CR and MC, but all had average values >10 mg/mL IgG. Calves fed LMC-CR had greater AEA than calves fed MC (54.58 ± 2.39 vs. 24.38 ± 2.36%, respectively). Among calves fed CR-110 or CR-150, AEA did not differ. Serum total protein and Brix percentage had strong correlations with actual IgG values across the entire study. We found no differences in average daily gain or health variables measured, and no differences in final hip width, withers height, or body weight for calves fed MC, LMC-CR, CR-150, or CR-110. These results indicate that CR can be fed successfully as an alternative to MC or as a supplement to colostrum with low IgG.

Salivary IgG levels in neonatal calves and its association to serum IgG: an observational pilot study

The diagnosis of inadequate transfer of colostrum immunoglobulin G (IgG) to calf serum, often known as failure of passive transfer (<10 g/L IgG1 at 24 to 48 h), necessitates blood sampling from the calf and in some instances the presence of a veterinarian. Sampling saliva is both less invasive and easy for the producer. Previous research has shown that quantification of saliva IgG is possible in juvenile and adult cattle. The objectives of this observational pilot study were to investigate whether IgG can be quantified in neonatal calf saliva, if it is correlated to serum IgG concentrations, and if the indirect quantification of saliva IgG is achievable by use of a digital refractometer. Paired blood and saliva samples were collected from 20 healthy dairy calves aged 1 to 3 d. In these samples, IgG was quantified directly with single radial immunodiffusion and indirectly by use of a digital refractometer indicating Brix % (a subsample of n = 12 saliva samples). A strong positive correlation (r = 0.7, P < 0.001) between saliva IgG (mean ± SD; 0.2 ± 0.11 g/L) and serum IgG (32.1 ± 11.94 g/L) was found. Saliva IgG ranged from the lowest detectable value, 0.1 g/L (n = 6 samples) to 0.6 g/L. Saliva Brix (1.2 ± 0.69%) was not significantly correlated to serum IgG (n = 12, r = 0.43, P = 0.155); however, it was significantly correlated to saliva IgG (n = 12, r = 0.7, P = 0.018) and Brix in serum (n = 12, r = 0.7, P = 0.013). We conclude that IgG was quantifiable in most of the saliva samples. For saliva IgG to be of any value with regards to detecting failure of passive transfer, future studies should investigate methods that can detect IgG <0.1 g/L. The results indicate that saliva IgG can be used to predict serum IgG at levels above 10 g/L, which may warrant further exploration of the use of saliva in the surveillance of failure of passive transfer. The results of the current pilot study did not support the potential usage of a Brix % refractometer to quantify saliva IgG.

Effects of difructose anhydride III on serum immunoglobulin G concentration and health status of newborn Holstein calves during the preweaning period

This experiment was performed to investigate the effects of increases in passively acquired immunoglobulin G (IgG) by difructose anhydride (DFA) III supplementation on subsequent serum IgG concentration and health status in calves during the preweaning period. Thirty newborn female Holstein calves were paired by birth order, and 2 calves in each pair were fed 2 L of the same batch of colostrum within 2 h and at 10 h after birth, and followed by 2 L of the same batch of pooled colostrum at 20 h after birth. One calf from each pair was assigned to the control (n = 15) or treatment (n = 15) group. All calves in the treatment group received 18 g of DFA III at each feeding from birth to 7 d of age, whereas calves in the control group did not receive DFA III. Blood samples were collected before feeding at 0, 10, 20, and 36 h, and 4 and 7 d of age, and sampling was repeated at 7-d intervals thereafter until 49 d of age for serum IgG analysis. Calves were monitored daily for diarrhea and respiratory diseases. Serum IgG concentrations peaked at 36 h of age in both groups. Apparent efficiency of IgG absorption and peak serum IgG concentration were higher in the treatment group than in the control group. Using multiple regression analysis, we showed that peak serum IgG concentration in the newborn calves was positively correlated with colostral IgG concentration and DFA III supplementation. Moreover, peak serum IgG concentration (36 h of age) positively influenced subsequent serum IgG concentration until 35 d of age for all calves in both groups. The treatment group had higher serum IgG concentration from 20 h to 21 d of age than the control group. However, we detected no differences between the groups in number of calves with diarrhea or respiratory disease.

Comparison of rapid laboratory tests for failure of passive transfer in the bovine

Background

Failure of passive transfer of maternal immunity via colostrum can occur in the bovine, and a number of blood tests have been developed to test calves for this failure. It is not clear which test is most suitable for this purpose. The objective was to examine the most commonly used tests for failure of passive transfer and to decide which is most suitable for routine laboratory use. 126 serum samples were taken from calves of dairy cows after birth but prior to colostrum feeding, and at 48 h of age. Five different tests were compared against radial immunodiffusion which is considered the appropriate reference method. These tests were serum gamma-glutamyltransferase levels, serum protein levels, serum globulin levels, an enzyme linked immunosorbent assay and the zinc sulphate turbidity test.

Results

The tests examined displayed high sensitivity but widely varying specificity. Examination of the use of different cut-off points allowed some improvement in specificity at the expense of sensitivity, but the tests which had performed best at the original cut-off points still displayed the best performance. Gamma-glutamyltransferase levels as a measure of colostrum absorption returned, in this study, the best balance between sensitivity and specificity. The ELISA used in this study and serum globulin levels displayed performance similar to the gamma-glutamyltransferase levels. Serum total protein was less successful than others examined at providing both sensitivity and specificity but may, when performed via refractometer, be useful for on-farm testing. As currently performed the poor sensitivity for which the zinc sulphate turbidity test is most often criticized is evident. Modification of the cut-off point to increase specificity is less successful at balancing these parameters than the ELISA, gamma-glutamyltransferase levels, and globulin levels.

Conclusions

Gamma-glutamyltransferase levels, ELISA testing and circulating globulin levels performed best in detecting failure of passive transfer in serum samples, although all three had some practical considerations.

Effect of feeding colostrum at different volumes and subsequent number of transition milk feeds on the serum immunoglobulin G concentration and health status of dairy calves

Transfer of sufficient IgG to the newborn calf via colostrum is vital to provide it with adequate immunological protection and resistance to disease. The objectives of the present study were to compare serum IgG concentration and health parameters of calves (1) fed different volumes of colostrum [7, 8.5, or 10% of body weight (BW)] within 2h of birth and (2) given 0, 2, or 4 subsequent feedings of transition milk (i.e., milkings 2 to 6 postcalving). Ninety-nine dairy calves were fed 7, 8.5, or 10% of BW in colostrum within 2h of birth and given 0, 2, or 4 subsequent feedings of transition milk. The concentration of IgG in the serum of calves was measured at 24, 48, 72, and 642 h of age by an ELISA. The apparent efficiency of absorption for IgG was determined. Health scores were assigned to calves twice per week and all episodes of disease were recorded. The effect of experimental treatment on calf serum IgG concentration differed by the age of the calf. Calves fed 8.5% of BW in colostrum had a greater mean serum IgG concentration than calves fed 7 or 10% of BW at 24, 48, and 72 h of age. At 642 h of age, serum IgG concentrations of calves fed 8.5% of BW (24.2g/L) and calves fed 10% of BW (21.6g/L) did not differ, although the serum IgG concentration of calves fed 8.5% of BW was still greater than that of calves fed 7% of BW (20.7 g/L). No difference in serum IgG concentration existed between calves fed 7% of BW and those fed 10% of BW at any age. No significant effect of number of subsequent feedings of transition milk on calf serum IgG concentration was detected. The apparent efficiency of absorption of calves fed 8.5% of BW in colostrum (38%) was greater than calves fed 7% of BW in colostrum (26%) and tended to be greater than in calves fed 10% of BW (29%). Calves fed further feedings of transition milk after the initial feeding of colostrum had a lower odds (0.62; 95% confidence interval: 0.41 to 0.93) of being assigned a worse eye/ear score (i.e., a more copious ocular discharge or pronounced ear droop) and a lower odds (0.5; 95% confidence interval: 0.32 to 0.79) of being assigned a worse nasal score (i.e., a more copious and purulent nasal discharge) during the study period relative to calves that received no further feedings of transition milk. In conclusion, calves fed 8.5% of BW in colostrum within 2h of birth achieved a greater concentration of IgG in serum in the first 3 d of life than calves fed either 7 or 10% of BW. Feeding calves transition milk subsequently reduced their odds of being assigned a worse eye/ear and nasal score.

Approaches to management and care of the neonatal nondomestic ruminant

Management and care of the nondomestic ruminant neonate are similar in principle to domestic animal practice. Housing of the dam, conditions for birth, preparation for intervention, and plans for treatment and hand-rearing of sick neonates must all be considered carefully before undertaking nondomestic ruminant breeding. Unfortunately, neonatal losses tend to be much higher in nondomestic calves before weaning than in domestic cattle, sheep, and goat herds.1 With continued habitat and population declines in wild species, successful captive breeding of nondomestic herds becomes more important to species sustainability and potential reintroduction programs. The primary challenges contributing to neonatal losses in nondomestic ruminants are often animal temperament and adaptation to captivity. Only through experience can some of these challenges be overcome. However, by understanding some species-specific behavioral tendencies and the fractious nature of nondomestic ruminants in general, we can improve our success in managing and maintaining healthy populations of nondomestic ruminants in captivity.

Influence of pooled colostrum or colostrum replacement on IgG and evaluation of animal plasma in milk replacer

Newborn Holstein (n = 48) and Jersey (n = 30) calves were studied to compare absorption of immunoglobulin G (IgG) from maternal colostrum (n = 39) or colostrum replacement containing an Ig concentrate derived from bovine serum (n = 39). Calves were also fed milk replacer with (n = 38) or without (n = 40) animal plasma (20% of crude protein) to 29 d of age to determine effect of plasma protein on IgG status, health, and growth. Calves were fed maternal colostrum or colostrum replacement at 1.5 and 13.5 h of age and provided a total of 250 or 249 and 180 or 186 g of IgG for Holsteins and Jerseys fed maternal colostrum or colostrum replacement, respectively. Milk replacer (12.5% DM) was fed at 31% of metabolic birth weight (2 feedings/d). Plasma was sampled at 0 h, 24 h, and weekly to determine IgG by turbidimetric immunoassay. At blood collection, calves were weighed and measured to determine growth. Health scores, fecal scores, and grain intake were measured daily. Plasma IgG at 24 h did not differ between calves fed maternal colostrum (13.78 ± 0.39 g/L) and colostrum replacement (13.96 ± 0.38 g/L). Average daily gain, withers height, hip height, body length, heart girth, health, and incidence of diarrhea were not different between treatment groups. Calves fed maternal colostrum used feed more efficiently than calves fed colostrum replacement. Plasma IgG and performance were not affected by the addition of animal plasma to milk replacer. The colostrum replacement used in this study provided adequate IgG for newborn calves. Animal plasma was an acceptable source of protein but did not enhance growth or immunity under the conditions of this study.

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.

Specific immunoglobulins in serum of newborn lambs fed with a single dose of colostrum containing anti-peroxidase IgG

The apparent efficiency of absorption and the decrease of specific colostral IgG after its passage into the blood stream were determined in newborn lambs fed with a single dose of colostrum containing anti-peroxidase IgG at 30 minutes, 12 hours and 24 hours after birth. When colostrum was given at 30 minutes after birth, a value of 16.9+/-4.0 per cent of anti-peroxidase IgG ingested appeared in lamb circulation. This percentage was reduced to 9.8+/-0.8 per cent when the feeding was done at 12 hours after birth and no specific IgG was detected in lambs fed at 24 hours after birth. The concentration of anti-peroxidase IgG in lambs' serum declined quickly within 96 hours of age to about 48 per cent of the initial value, and afterwards the level decreased slowly reaching a value of 10 per cent at 32 days of age. This behaviour probably reflects the protein distribution and use of absorbed antiperoxidase IgG.

Age and previous lactations as factors in the amount of bovine colostral immunoglobulins

Blood and colostrum samples were obtained from 87 dairy cows in five lactation groups and analyzed for immunoglobulins G1, G2, M, and A. The five groups ranged from cows in first lactation, about 30 mo of age, to cows in fifth or more lactation, about 84 mo of age. Compared to older groups, blood serum of cows in first lactation contained less G1. Cows in first lactation also produced less total colostrum containing less total G1, G2, and M. Immunoglobulin G1 comprised over two-thirds of the immunoglobulins in the colostrum of all groups. Older cows had more immunoglobulin G1 in their colostrum with a tendency toward a higher ratio of G1 to G2. Amount of immunoglobulin A was constant through all lactations. After a rise in the second lactation, total amount of immunoglobulins G2 and M tended to level off. Total immunoglobulin G1 tended to reach a maximum in the third or fourth lactation, almost doubling in amount compared to the first lactation. Age and number of lactations are factors correlated with amounts of these immunoglobulins in colostrum.

Absorption of colostral immunoglobulin G in the newborn dairy calf

Five groups of eight newborn calves were used to study absorption of colostral immunoglobulin G. One feeding of 2 liters of pooled colostrum was given at one of 6, 12, 24, 36, or 48 h after birth. Concentrations of immunoglobulin G in blood plasma and feces were measured by an immunodiffusion technique. Plasma volume and fecal excretion also were measured. When colostrum was given 6 h after birth, 65.8% of the ingested immunoglobulin G appeared in the plasma. This percentage declined rapidly to reach 46.9%, 11.5%, 6.7%, and 6.0% when colostrum was given at the ages of 12, 24, 36, and 48 h. Total fecal immunoglobulin G increased linearly with age. The quantities not recovered from plasma and feces reached a maximum when colostrum was given at 24 or 36 h after birth. Immunoglobulin G can be "lost" to a great extent via routes other than plasma and feces during this time. Quantities of immunoglobulin G measured in plasma represent apparent rather than true absorption.

Advances in Nutrition and Management of Calves and Heifers

Strides have been significant in the knowledge of calf and heifer rearing during the last 25 yr. Much information has been gathered on digestive enzymes, development of the digestive system, and metabolism. Investigations have clarified further the role of colostrum in immunity and nutrition of the young calf. Several sources of nutrients have been tested for their suitability in formulation of acceptable milk replacers and calf starters. Once-a-day feeding of milk, colostrum, or milk replacer and early weaning are practical management procedures. Labor and cost efficient methods of feeding and caring for young calves have developed. Extensive work on rearing rates and methods of rearing was published during these 25 yr.

Successful schemes have evolved for feeding heifers to freshen at an optimal age and to occupy a respectful position in the milking line. Developments in housing have been phenomenal – from the calf hutch to environmentally controlled nurseries for calves. Heifer housing has ranged from relatively simple, but labor-efficient housing, to complete confinement systems. Herd health programs have developed to minimize many disease problems that can be particularly disastrous in large herds. Contract rearing of herd replacements has become a more frequently chosen option in this period. Budgets for rearing calves from birth to freshening have appeared in recommendations for raising heifers.

Immunoglobulin production and transport by the mammary gland

In origin immunoglobulins in mammary secretions are both humoral, arising from the blood stream, and local, arising from production by plasmacytes in the mammary gland. The relative importance of each of these sources varies between species. In some species (human, rabbit, etc.), the transfer of maternal immunoglobulins to the blood stream of the neonate occurs in utero across the placenta or yolk sac membrane. In other species, including ruminants, transfer of maternal immunoglobulins to the neonate occurs exclusively via the colostrum. Both in utero and colostral routes of transfer are operative in other species. The concentration and class of immunoglobulins in the colostrum and milk of a species reflect the route and origin of the immunoglobulins. Immunoglobulins transferred in quantity in utero or via the colostrum are mainly of the IgG class. Immunoglobulins locally produced by plasmacytes located adjacent to the secretory epithelium and in the mammary secretions are largely of the IgA and IgM classes. The bovine transfers large amounts of IgG immunoglobulins, and IgG1 in particular, from the blood stream across the mammary barrier into colostrum (and milk) by a specific transport mechanism. Bovine colostrum and milk also contain much smaller amounts of locally produced IgA and IgM.