Energy metabolism in the newborn farm animal with emphasis on the calf: endocrine changes and responses to milk-born and systemic hormones

Neonatal mammals need adaption to changes in nutrient supply because energy intake shifts from continuous parenteral supply of nutrients (mainly glucose, lactate, and amino acids) via the placenta to discontinuous colostrum and milk intake with lactose and fat as main energy sources. Besides ingested lactose, endogenous glucose production is essential in the neonate to assure sufficient glucose availability. Fetal endogenous glucose production is low, but endocrine changes (especially the prenatal rise of glucocorticoid production) promote maturation of metabolic pathways that enable marked glycogen synthesis before and enhanced gluconeogenesis after birth to establish an adequate glucose status during postnatal maturation. In preterm born farm animals gluconeogenic activity is low, mainly because of a low glucocorticoid and thyroid status. In full-term neonates, endogenous glucose production increases with age. Colostral bioactive components (such as growth factors, hormones, bioactive peptides, and cytokines) do not have a direct effect on endogenous glucose production. However, colostrum feeding stimulates intestinal growth and development, an effect at least in part mediated by bioactive substances. Increased nutrient and glucose absorption thus allows increased glucose supply and hepatic glycogen storage, which improves the glucose status. The improved energetic status of colostrum-fed neonates is reflected by an accelerated maturation of the somatotropic axis, leading especially to enhanced production of IGF-I in the neonate. Secretion and production of hormones involved in the regulation of glucose and fat metabolism in neonates depend on the developmental stage and the response to feeding. In addition, many such hormones have actions in the neonate that differ from adult animals. Endocrine action to support endogenous energy supply in neonates is probably not fully established, and therefore, needs postnatal maturation. Therefore, our knowledge on energy metabolism in the neonate needs to be extended to better understand the function and the failure and to assess endocrine responses during the neonatal period.     

Effects of colostrum feeding and dexamethasone treatment on mRNA levels of insulin-like growth factors (IGF)-I and -II, IGF binding proteins-2 and -3, and on receptors for growth hormone, IGF-I, IGF-II, and insulin in the gastrointestinal tract of neonatal calves

The somatotropic axis regulates growth of the gastrointestinal tract (GIT). In addition, colostrum feeding and glucocorticoids affect maturation of the GIT around birth in mammals. We have measured mRNA levels of members of the somatotropic axis to test the hypothesis that colostrum intake and dexamethasone treatment affect respective gene expression in the GIT. Calves were fed either colostrum or an isoenergetic milk-based formula, and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/kg body weight per day). Individual parameters of the somatotropic axis differed (P < 0.05) among different GIT sections and formula feeding increased (P < 0.05) mRNA levels of individual parameters at various sites of the GIT. Effects of DEXA on the somatotropic axis in the GIT partly depended on different feeding. In colostrum-fed calves, DEXA decreased (P < 0.05) mRNA levels of IGF-I (esophagus, fundus, duodenum, and ileum), IGF-II (fundus), IGFBP-2 (fundus), IGFBP-3 (fundus), IGF1R (esophagus, ileum, and colon), IGF2R (fundus), GHR (fundus), and InsR (esophagus, fundus), but in formula-fed calves DEXA increased mRNA levels of IGF-I (esophagus, rumen, jejunum, and colon). Furthermore, DEXA increased (P < 0.05) mRNA levels of IGF-II (pylorus), IGFBP-3 (duodenum), IGF2R (pylorus), and GHR (ileum), but decreased mRNA levels of IGFBP-2 (ileum), and IGF1R (fundus). Whereas formula feeding had stimulating effects, effects of DEXA treatment on the gene expression of parameters of the somatotropic axis varied among GIT sites and partly depended on feeding.     

Transfer of maternal colostral leukocytes promotes development of the neonatal immune system Part II. Effects on neonatal lymphocytes

It has been established that maternal leukocytes, conditioned by the mammary environment, cross the neonatal gut and circulate in the newborn calf. However, the impact of these cells on the development of neonatal immunity remains to be determined. This study examined the effects of maternal colostral leukocytes on development and maturation of neonatal adaptive immunity by examining the expression of surface markers on neonatal lymphocytes. At birth, neonatal calves were fed whole colostrum, or colostrum that had the maternal cells removed (cell-free colostrum), from their respective dams. Peripheral blood samples were collected at regular intervals over the first 4 weeks of life and lymphocytes were evaluated for surface expression of cellular markers. The results of these studies demonstrated that calves receiving whole colostrum had fewer CD11a positive lymphocytes in circulation during the first 2 weeks of life and this marker was expressed at a lower density than calves receiving cell-free colostrum. In addition, calves receiving whole colostrum also had a higher percentage of lymphocytes expressing the activation markers CD25 and CD26 by 7 days after birth. During the first week of life, lymphocytes from calves receiving whole colostrum had a higher density of MHC class I expression on their surfaces than cells from calves receiving cell-free colostrum. In general, these results indicate that transfer of maternal cells with colostrum allows for more rapid development of lymphocytes and maternal cells appeared to enhance their activation.     

Effect of maternal cells transferred with colostrum on cellular responses to pathogen antigens in neonatal calves

OBJECTIVE: To assess the effect of maternal cells or cellular components on neonatal immune responses to intracellular pathogens in calves. ANIMALS: 15 Holstein calves. PROCEDURES: Calves were fed whole colostrum, frozen colostrum, or cell-free colostrum within 4 hours after birth. Leukocytes were obtained from calves before feeding colostrum and 1, 2, 7, 14, 21, and 28 days after ingestion. Proliferative responses against bovine viral diarrhea virus (BVDV) and mycobacterial purified protein derivatives were evaluated. Dams received a vaccine containing inactivated BVDV, but were not vaccinated against mycobacterial antigens. RESULTS: All calves had essentially no IgG in circulation at birth, but comparable and substantial concentrations by day 1. Calves that received whole colostrum had enhanced responses to BVDV antigen 1 and 2 days after ingestion of colostrum. In contrast, calves that received frozen colostrum or cell-free colostrum did not respond to BVDV. No differences were identified among the 3 groups in response to mycobacterial antigens. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that transfer of live maternal cells from colostrum to neonatal calves enhanced responses to antigens against which the dams had previously responded (BVDV), but not to antigens to which the dams were na?ve (mycobacterial purified protein derivatives). Results suggested that cell-mediated immune transfer to neonates can be enhanced by maternal vaccination.     

In vitro growth-promoting activity of porcine mammary secretions: initial characterization and relationship to known peptide growth factors

We have examined the in vitro growth-promoting properties and growth factor content of porcine mammary secretions. Defatted, porcine colostrum stimulated the proliferation of fibroblast and epithelial-like cell lines of diverse species origins in serum-free medium and cellular DNA synthesis (4- to 119-fold) as monitored by uptake of 3H-thymidine into DNA of quiescent cells in culture. Porcine milk, although mitogenic, had reduced activity when compared with colostrum on an equivalent-volume basis. Furthermore, the relative mitogenic activity of milk, although still detectable at 3 wk, continued to decline with length of the lactation period. Fractionation of pig colostrum on gel-filtration columns revealed multiple peaks of (AKR-2B) fibroblast mitogenic activity (208, 66 and 4.6 kdaltons) and a heterogenous profile of epithelial cell mitogenicity. Polyclonal antibodies (IgG) specific for murine epidermal growth factor (EGF; the major mitogen in human and murine milk) or human platelet-derived growth factor (PDGF) did not inhibit the mitogenic activity of pig colostrum or milk, demonstrating lack of antigenic relatedness between the contributing porcine factors and mEGF or hPDGF. Also, we were unable to demonstrate similarity of the small Mr colostral factor with EGF by use of EGF radioreceptor assay. These results identify porcine colostrum and milk as sources of potentially important in vitro growth-promoting factors. The enhanced expression of these factors in early mammary secretions suggests their possible in vivo involvement in mammary and neonatal tissue growth processes.     

Effects of peroral insulin and glucose on circulating insulin-like growth factor-I, its binding proteins and thyroid hormones in neonatal calves

There is disagreement in the literature about the ability of neonatal calves to absorb perorally administered insulin. This study evaluated the absorption of a bolus of insulin administered alone or with an energy souce and its effects on the circulating insulin-like growth factor system and thyroid hormones in newborn Holstein-Friesian calves. Within 1 h of dosing, mean serum insulin and triiodothyronine (T3) concentrations had increased considerably, whether the insulin was applied alone (n = 4) or together with glucose (n = 4), accompanied by marked hypoglycemia. No significant changes were observed in control calves (n = 4) given the vehicle solution. Increased serum glucose and T3 concentrations with no change in insulinemia occurred in a 4th group of calves given glucose alone. At 32 h of age and after 3 meals of colostrum there were no differences in glycemia, insulinemia, or proteinemia among the 4 groups of calves examined. Mean serum insulin-like growth factor-I (IGF-I) tended to decrease over this period in the control group. The decrease was more pronounced in the insulin-treated group but absent in both groups that received glucose. These differences were associated with equivalent differences in abundance of the 40-45K IGF-binding protein-3 (IGFBP-3); however, lower molecular mass IGFBPs were not affected. The results show that a pharmacological peroral dose of insulin can lead to rapid systemic alterations in the IGF/IGFBP system in neonatal calves that can be modified by simultaneous administration of a small energy supply in the form of glucose.     

Receptor-mediated transport of lactoferrin into the cerebrospinal fluid via plasma in young calves

Milk, especially colostrum, contains different kinds of macromolecules abundantly, such as immunoglobulin G (IgG), lactoferrin (Lf), transferrin (Tf), and growth factors. These are essential for the development and maintenance of health, which greatly depends on the absorption and transportation of macromolecules to the target organs. To evaluate the macromolecular transport, and concentrations in plasma and cerebrospinal fluid (CSF), colostrum was fed to newborn calves followed by milk and milk replacer, and maintained up to the 4th week under farm conditions. Plasma and CSF were collected at different times, and were analyzed for Lf, Tf, IgG and iron concentrations. Lf, Tf and IgG concentrations were steeply increased in plasma and CSF after colostrum feeding, and fluctuating patterns were observed during the experiments. Furthermore, intraduodenal administration of bovine Lf alone in young calf experiments revealed that the Lf concentration reached a peak at 4 hr, and was 7 and 4 times higher than preadministration in plasma and CSF, respectively. To explore the transport mechanism of Lf into CSF in young calves, epithelial membranes of the choroid plexus were prepared and a binding assay for Lf receptors (Lf-R) was carried out with 125I-Lf. The saturation kinetics revealed that the Bmax of epithelial membranes was 26.15 nmol/mg protein with a Kd of 0.11 microM, which also showed that Lf-R is saturable and specific. Scatchard plot transformation showed the presence of a single type of Lf-R in the choroid plexus. These results suggest that Lf is transported into the CSF through receptor mediated transcytosis in young calves, and that Lf may play an important role(s) in brain function.     

Evaluation of serum insulin-like growth factor binding proteins (IGFBP) in Angus cattle divergently selected for serum IGF-I concentration

Postweaning serum insulin-like growth factor-I (IGF-I) concentrations and serum IGF binding proteins (IGFBP) were investigated in 68 (1992 Fall-born) and 84 (1999 Fall-born) Angus cattle selected for either high or low serum IGF-I concentrations since 1989. Relative serum levels of IGFBP were determined by [¹²⁵I]IGF-I Western ligand blotting. IGFBP species of 38–42, 34, 30, and 24 kDa were identified. The 34 kDa species was identified as IGFBP-2 by immunoblot analysis. No significant line effects were observed for any of the IGFBP. In both 1992 and 1999, heifers had higher IGFBP-2 levels than bulls (P<0.0005). In 1992 calves, relative levels of the 38–42 and 24 kDa species were significantly correlated with serum IGF-I concentration. In 1999 calves, none of the IGFBP were correlated with serum IGF-I, although IGFBP-2 was negatively correlated with several measures of body weight. No significant line effects were observed for growth or serum IGF-I traits in 1992 calves. However, 1999 high line calves had higher serum IGF-I concentrations and body weights than low line calves (P<0.05). In both 1992 and 1999 calves, bulls had higher serum IGF-I concentrations and body weights than heifers (P<0.05). Thus, while selection for high versus low serum IGF-I concentrations has resulted in divergence between the selection lines and also in changes in body weights, it has not resulted in changes in serum IGFBP levels. Furthermore, circulating IGFBP-2 appears to be higher in heifers than in bulls, and also appears to be negatively correlated with body weights.     

Insulin-like growth factor binding proteins initiate cell death and extracellular matrix remodeling in the mammary gland

We have demonstrated that insulin-like growth factor binding protein-5 (IGFBP-5) production by mammary epithelial cells increases dramatically during forced involution of the mammary gland in rats, mice and pigs. We proposed that growth hormone (GH) increases the survival factor IGF-I, whilst prolactin (PRL) enhances the effects of GH by decreasing the concentration of IGFBP-5, which would otherwise inhibit the actions of IGFs. To demonstrate a causal relationship between IGFBP-5 and cell death, we created transgenic mice expressing IGFBP-5, specifically, in the mammary gland. DNA content in the mammary glands of transgenic mice was decreased as early as day 10 of pregnancy. Mammary cell number and milk synthesis were both decreased by approximately 50% during the first 10 days of lactation. The concentrations of the pro-apoptotic molecule caspase-3 was increased in transgenic animals whilst the concentrations of two pro-survival molecules Bcl-2 and Bcl-x were both decreased. In order to examine whether IGFBP-5 acts by inhibiting the survival effect of IGF-I, we examined IGF receptor- and Akt-phoshorylation and showed that both were inhibited. These studies also indicated that the effects of IGFBP-5 could be mediated in part by IGF-independent effects involving potential interactions with components of the extracellular matrix involved in tissue remodeling, such as components of the plasminogen system, and the matrix metallo-proteinases (MMPs). Mammary development was normalised in transgenic mice by R3-IGF-I, an analogue of IGF-I which binds weakly to IGFBPs, although milk production was only partially restored. In contrast, treatment with prolactin was able to inhibit early involutionary processes in normal mice but was unable to prevent this in mice over-expressing IGFBP-5, although it was able to inhibit activation of MMPs. Thus, IGFBP-5 can simultaneously inhibit IGF action and activate the plasminogen system thereby coordinating cell death and tissue remodeling processes. The ability to separate these properties, using mutant IGFBPs, is currently under investigation.     

Evaluation of the pathogenic potential of cervid adenovirus in calves.

Four 3-month-old Jersey calves and three 3-month-old Holstein calves were inoculated with cervid adenovirus and monitored for clinical signs until necropsied between 10 and 42 days postinoculation. The neonatal Jersey calves had received colostrum, and the Holstein calves were colostrum deprived. Preinoculation and postinoculation serum samples were tested for antibodies to the cervid adenovirus, bovine adenovirus type 6, bovine adenovirus type 7, and goat adenovirus type 1. Virus isolation was performed on kidney, nasal secretion, and/or lung homogenates in fetal white-tailed deer lung cells. Negatively stained preparations of feces from Jersey calves were examined weekly using an electron microscope, and weekly blood samples were collected for complete blood counts. Full necropsies were performed on all calves. A complete selection of tissues was evaluated for microscopic changes, and immunohistochemistry was performed on all tissues using a polyclonal antibody to deer adenovirus. No clinical signs were observed in the calves during the study period. Following inoculation, colostrum-deprived calves developed low antibody titers to deer adenovirus, while the Jersey calves that received colostrum did not. Calves that received colostrum had high antibody titers to bovine adenovirus type 7 and goat adenovirus type 1. No consistent gross or microscopic lesions were seen. Adenovirus was not observed in negatively stained preparations of feces. Immunohistochemistry results did not demonstrate virus in all tissues examined microscopically, and virus was not isolated from lungs, nasal secretions, and kidneys.     

Bovine colostrum: more than just an immunoglobulin supplier

The intake of colostrum in newborn calves not only influences the immune status, but also the development of the gastrointestinal tract and other organs, metabolism and endocrine systems. Besides nutrients bioactive substances of colostrum have additionally to be considered. Metabolic and endocrine effects are transient, indications for metabolic and endocrine imprinting by differences in feeding in the first week of life have so far not been found. Nevertheless, changes observed in association with feeding especially of colostrum are considered important for the critical first week of life.     

Effects of the ingestion of whole colostrum or cell-free colostrum on the capacity of leukocytes in newborn calves to stimulate or respond in one-way mixed leukocyte cultures

OBJECTIVE: To evaluate effects of colostral cells on the ability of neonatal leukocytes to respond in a mixed leukocyte response (MLR) as a means of evaluating specific immune responsiveness. ANIMALS: 10 Holstein calves, their respective dams, and 10 unrelated adult Holstein cows. PROCEDURE: Soon after birth, their calves were fed maternal whole colostrum or colostrum after cells were removed by centrifugation. Responses for leukocytes obtained from calves during the first 5 weeks after birth, their dams, and unrelated cows were measured by use of 1-way MLR as an indicator of immune development. An internal control treatment, proliferation of lymphocytes stimulated with Staphylococcus enterotoxin B (SEB), was also measured. RESULTS: Transfer of colostral leukocytes had a significant effect on the MLR and SEB-induced response in calves. Calves receiving whole colostrum had enhanced responses to maternal and unrelated leukocytes 24 hours after ingestion of colostrum. These responses decreased quickly, indicating direct modulation of the neonatal immune response. Calves receiving whole colostrum effectively stimulated the MLR by 24 hours after ingestion of colostrum. In contrast, calves receiving acellular colostrum did not effectively stimulate the MLR until 2 to 3 weeks after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Ingestion of maternal colostral leukocytes immediately after birth stimulates development of the neonatal immune system. These maternal leukocytes enhance development of antigen-presenting capacity as indicated by their ability to stimulate the MLR and SEB response. The influence of ingested maternal cells on neonatal immunity was also indicated by a reduction in reactivity of neonatal cells to maternal alloantigens.     

Lactoferrin interaction with retinoid signaling: cell growth and apoptosis in mammary cells

Lactoferrin (Lf) is a multifunctional iron-binding protein that was first identified in mammary secretions, but is synthesized by most mammalian tissues. The protein has a signal sequence that dictates secretion; it also has a nuclear localization sequence that facilitates entry into the cell nucleus. The mechanism of the latter action is currently unknown, but is thought to occur via a Lf receptor. Lactoferrin content of mammary tissue and secretions varies with developmental state; it is synthesized in mammary tissue at high levels during both pregnancy and involution, and during mammary infections. Using fluorescent (FITC)-labeled holo-bLf, we show that bovine primary epithelial cells and MCF-7 breast cancer cells do not translocate the exogenously added Lf to the nucleus after culture in serum free media (SFM). However, the supplementation of SFM with 1 μM all-trans retinoic acid (atRA) caused breast cancer cells to gain the capacity to take up labeled bLf into the cell nucleus. Primary bovine mammary cells (MeBo) exhibited similar capacity in culture. This suggests that in addition to Lf, one or more components modulated by atRA, are necessary for nuclear translocation to occur. Transfection experiments with atRA treated MCF-7 cells containing retinoic acid response element reporter constructs showed that the extracellular application of lactoferrin alters reporter gene expression. Lactoferrin increased a DR5 luciferase response element in a dose-dependent manner only when atRA was applied. Immunocytochemical markers for the cell cycle (Ki67) and apoptotic events (Caspase-3 and PARP-85) showed that lactoferrin alters the atRA-induced phenotype, blocking apoptosis and maintaining cell cycle activity in both MCF-7 and MeBo cells in the presence of 1 μM atRA. We propose that nuclear lactoferrin interacts with retinoic acid signaling pathways in cells and alters/blocks the signals so that cells remain in the cell cycle and/or do not enter the apoptotic pathway.     

Antibody titres to lamb rotavirus in colostrum and milk of vaccinated ewes.

Ewes were vaccinated two to three weeks prior to mating with a formalin-treated preparation of lamb rotavirus. The colostrum and milk produced by vaccinated ewes after the subsequent pregnancy were shown to contain significantly higher titres of antibody to the virus than did mammary secretions from non-vaccinates. The virus neutralising antibody activity was associated with IgG in both colostrum and milk. However, IgG concentrations in the mammary secretions of vaccinates and non-vaccinates did not differ. It is suggested that vaccination of the dam may be of value in protecting the suckled neonatal lamb against rotavirus infection.     

Insulin-like growth factor-I, passive immunity transfer, and stereological characteristics of small intestine of newborn calves

This study evaluated the concentration of insulin‐like growth factor (IGF)‐I present in the mammary secretions, its relation with changes in serum IGF‐I and immunoglobulin (Ig)G, and intestinal mucosa alterations of 42 calves during the first week of life. Cows were randomly assigned to two groups, treated and control, with 21 animals in each. The treated group was injected with 500 mg recombinant bovine somatotropin (rbST) at day ?35 relative to predicted calving date. Newborn calves were randomly assigned to a 2 × 3 factorial scheme: dams group and slaughter date (at birth, 2 and 7 days of life). IGF‐I concentration was higher in the colostrum of treated cows (P < 0.05), but did not differ in the subsequent mammary secretions. Immunoglobulin G concentration in colostrum and subsequent mammary secretions did not differ between groups (P > 0.05). No differences were found in calf serum IGF‐I levels from birth to the seventh day or serum immunoglobulin G concentration after 24 h of life (P > 0.05). IGF‐I colostrum levels observed in this study did not affect the small intestine morphometry. The segment from the middle jejunum showed higher mucosa partial volume (Vv) at birth and 7 days old compared to other segments, and at just 2 days of age this segment reduced its Vv, not differing from other segments of the same date.     

The ontogeny of the somatotropic axis in male and female Hereford calves from birth to one year of age

Insulin-like growth factor-binding proteins-2 and -3 may play a role in age-dependent growth response to bovine ST (bST) treatment in cattle; however, samples have been collected at infrequent intervals and at limited time points. Therefore, the objective of this experiment was to examine the ontogeny of components of the somatotropic axis in Hereford calves from birth to 1 yr of age at weekly intervals to determine whether there is a certain age or time frame when the somatotropic axis may change and/or potentially become more responsive to exogenous bST administration. Blood samples and body weight measurements were collected from eight male and eight female Hereford calves once per week from birth to 1 yr of age. Serum concentrations of ST, IGF-I, IGFBP-2, and IGFBP-3 were determined. Males began to grow faster than females at approximately 16 wk of age (P < 0.05). Average concentrations of ST, IGF-I, and IGFBP-3 were greater in males than females (P < 0.01). Average concentrations of IGFBP-2 were greater in females than in males (P = 0.05). Concentrations of ST decrease with age (P < 0.01); however, the decrease occurred earlier in female calves. Concentrations of IGF-I and IGFBP-3 increased in males and females (P < 0.01), and concentrations of IGF-I began to plateau at approximately the same time as growth rate differences were observed (16 wk of age). Following an initial increase (birth to approximately 16 wk of age), concentrations of IGFBP-3 remained constant until approximately 43 wk of age. Concentrations of IGFBP-2 increased to approximately 10 wk of age (P < 0.05), followed by a decrease, and then, similar to IGFBP-3, remained constant until 43 wk of age. Correlations between average daily gain, ST, IGF-I, IGFBP-2, and IGFBP-3 were determined. Average daily gain was negatively (P < 0.01) correlated with ST and positively (P < 0.1) correlated with IGF-I. In females, ST was negatively (P < 0.01) correlated with IGF-I. Concentrations of ST were positively correlated (P < 0.01) with IGFBP-2 and IGFBP-3. Concentrations of IGFBP-2 were negatively correlated (P < 0.01) with IGF-I and positively correlated (P < 0.01) with IGFBP-3. In conclusion, serum concentrations of ST, IGF-I, IGFBP-2, and IGFBP-3 differed between male and fe-male calves. In addition, changes in components of the somatotropic axis occurred around the same time as males began to grow faster than females.     

Insulin-like growth factor (IGF)-I and -II and IGF binding proteins in serum and mammary secretions during the dry period and early lactation in dairy cows.

Concentrations of IGF-I and IGF-II, and IGF binding proteins (IGFBP) in serum and mammary gland secretions were surveyed during the dry period and early lactation of 30 Holstein cows. Although there was a threefold drop in the concentration of IGF-I in serum from the last week of the dry period to parturition (81 +/- 7 to 24 +/- 3 ng/ml, P less than .01), there was no significant change in serum IGF-II concentration during this period (150 +/- 17 vs 173 +/- 13 ng/ml, P greater than .05). Furthermore, a 57% increase in serum IGF-I was observed from the last week of lactation to the second week of drying off (100 +/- 5 to 157 +/- 8 ng/ml, P less than .05). Changes in serum IGF-II were not observed (126 +/- 11 vs 150 +/- 10 ng/ml, respectively; P greater than .05). Although IGF-I, IGF-II, and IGFBP concentrations in mammary secretions peaked 2 wk before parturition (2.95 +/- 1.1, 1.83 +/- .6, and 7.27 +/- .76 micrograms/ml, respectively), total output/quarter was highest in colostrum (394 +/- 119, 295 +/- 132, and 2,680 +/- 1,967 micrograms/quarter, respectively). Weekly milking of two individual quarters during the dry period did not affect (P greater than .05) IGF-I or IGF-II concentration (ng/ml) or total output (microgram/quarter) and milk yield in colostrum and milk (2 wk and 7 wk) compared with the ipsilateral quarter. The data support the hypothesis that IGF-I may be transported by the mammary gland epithelium. Furthermore, the secretion mechanisms of IGF-I, IGF-II, and IGFBP by the gland may be related to each other.     

Use of mammary gland and colostral characteristics for prediction of colostral IgG1 concentration and intramammary infection in Holstein cows.

OBJECTIVE: To determine whether mammary gland or colostral characteristics at calving could be used to predict colostral immunoglobulin G1 (IgG1) concentration or intramammary infection (IMI) and whether leakage of colostrum affects IgG1 concentration. DESIGN: Prospective study. ANIMALS: 113 multiparous Holstein cows. PROCEDURE: Cows were examined within 3 hours of calving, and mammary gland and colostral characteristics, colostral volume, somatic cell count, and concentrations of IgG1, fat, and protein were determined. Bacteriologic culture of mammary secretions was performed approximately 14 and 7 days before calving and at calving. Associations of gland and colostral characteristics with colostral IgG1 concentration, colostral volume, and IMI were examined. RESULTS: Thick or thin colostrum had higher IgG1 concentration than colostrum of intermediate viscosity. Colostrum from mammary glands that were firm had low IgG1 concentration. Colostral IgG1 concentration was weakly correlated with volume. Intramammary infection was likely to be detected if colostrum contained clots or blood or if the California Mastitis Test (CMT) score was > or = 2. Somatic cell count was higher for glands with IMI than for uninfected glands, and CMT score was correlated with cell count. CLINICAL IMPLICATIONS: Mammary gland and colostral characteristics were of little value in predicting IgG1 concentration. Our findings do not support recommendations that first milking colostrum that is thin (watery) or that is from cows producing large volumes not be fed to dairy calves. Colostral characteristics, particularly CMT score, were of value for predicting IMI.