Blood plasma traits associated with genetic merit for feed utilization in Holstein cows.

The objective of this study was to evaluate the potential of selection for feed utilization on associated blood plasma metabolite and hormone traits. Dry matter intake (DMI) was recorded in 970 Holsteins from 11 commercial farms in Pennsylvania and used to derive dry matter efficiency (DME; fat-corrected milk yield/DMI), crude protein efficiency (CPE; protein yield/crude protein intake), and residual feed intake (RFI, defined as actual feed intake minus expected feed intake for maintenance and milk production, based on calculation of DMI adjusted for yield, body weight, and body condition score). Estimated breeding values for the 4 feed utilization traits (DMI, DME, CPE, and RFI), yield traits, body traits, and days open were standardized according to their respective genetic standard deviations. Up to 631 blood samples from 393 cows from 0 to 60 d in milk (DIM) were evaluated for blood plasma concentrations of glucose, nonesterified fatty acids (NEFA), ß-hydroxybutyrate (BHB), creatinine, urea, growth hormone (GH), 3,5,3'-triiodothyronine (T3), and other parameters. Blood plasma traits were regressed on DIM, lactation number, herd, and standardized genetic merit. Cows with higher genetic merit for yield had significantly higher concentrations of GH, NEFA (milk and protein yield), and BHB (fat yield) from 31 to 60 DIM, but lower concentrations of glucose from 0 to 30 DIM, and T3 (milk yield, 0-60 DIM). The high GH-low glucose-low T3 concentration pattern was further accentuated for cows with genetic merit for enhanced feed efficiency (higher DME and lower RFI). Cows with a genetic tendency to be thin (low body condition score) also had elevated GH concentrations, but lower blood glucose, creatinine, and T3 concentrations. Those characteristics associated with enhanced feed efficiency (higher GH and lower glucose and T3 concentrations) were unfavorably associated with fertility, as indicated by elevated days open. Elevated NEFA and BHB concentrations were also associated with extended days open. Consideration of metabolic profiles when evaluating feed efficiency might be a method of maintaining high levels of health and reproductive fitness when selecting for feed efficiency.

Mammary immunoglobulin transfer rates following prepartum milking.

Colostrum formation is thought to occur slowly over an extended period (4wk) prepartum. Furthermore, colostrum formation is highly variable among cows in total volume, IgG1 concentration, and mass obtained at first postpartum milking. Recent work has suggested that a rapid transfer of IgG1 to secretions may occur if animals are milked prepartum. Our objective was to establish the concentration, mass, and mass transfer rates of IgG1 in multiparous Holstein cows (n=11, parity=3.6±1.1) milked prepartum (-74 to -1h) and again around 4h postpartum. Blood concentrations of IgG1 were very low (<1mg/mL) in 7 cows at prepartum milking and did not decline following prepartum milking. Cows showed variability in the capacity to recover total volume, IgG1 concentration, and IgG1 mass. Three groupings of cows were considered based on the time between the 2 milkings (prepartum + 4h postpartum): long-time (-74 to -54h, n=3), medium-time (-25 to -17h, n=4), and short-time (< -13h, n=4) groups. The average rates of transfer of these groups were 1.4±0.8, 3.0±1.3, and 25.1±15.8g/h, respectively. The data indicate that a longer time between prepartum and postpartum milking is not a main factor in IgG1 secretion transfer. Furthermore, because blood concentrations did not change after prepartum milking and the mass of blood plasma IgG1 was not sufficient to account for the mass occurring in postpartum colostrum, a source of IgG1 other than blood circulation appears to be present during colostrogenesis.

Peripartal progesterone and prolactin have little effect on the rapid transport of immunoglobulin G into colostrum of dairy cows.

Colostrum formation and lactogenesis in the mammary gland and the timing of parturition are regulated by endocrine signals. Changes in progesterone (P4) and prolactin (PRL) are considered key events that inhibit colostrum formation, trigger parturition, and signal the onset of lactation. The goal of our study was to determine if colostrum yield and composition and immunoglobulin transfer are affected by prepartum milking relative to the decrease in P4, peak of PRL, or occurrence of parturition. Twenty-three multiparous cows were randomly assigned to 1 of 2 groups: (1) control with first milking at 4h postcalving (CON, n=11), and (2) treatment group with first milking approximately 1d before calving and second milking at 4h after parturition (APM, n=12). Colostrum yields were recorded and proportional samples were analyzed for immunoglobulin G (IgG) concentration. Blood plasma samples for the analyses of P4 and PRL were collected 3 times daily at 8-h intervals for 4d prepartum and again taken at 4h after parturition. Total colostrum mass of APM cows was higher than that of CON cows. Immunoglobulin G concentration and protein content did not differ between antepartum milking in APM cows and postpartum milking in CON cows. Colostrum IgG concentration and protein content in APM cows at the postpartum milking were lower compared with the IgG concentration established at the prepartum (APM) and postpartum milkings of CON cows. Immunoglobulin G mass did not differ in first and second colostrum collection in APM cows but was lower compared with that of CON cows. The sum of IgG mass in APM cows (prepartum + postpartum collections) did not differ from that of CON cows. Lactose and fat in milk (concentration and mass) increased from first to second milking in APM cows. Total mass of lactose and fat in APM cows (prepartum + postpartum collections) was greater compared with that of CON cows. The finding that the time of milking relative to parturition, P4 decrease, and PRL peak slightly affected yield and quality of colostrum emphasizes the complex interactions of numerous endocrine and morphological changes occurring during colostrogenesis and lactogenesis in dairy cows. The considerably rapid transfer of immunoglobulins into colostrum of prepartum-milked cows within a few hours leads to the hypothesis that the transfer of IgG can be very fast and-contrary to earlier findings-persist at least until parturition.

Short communication: Feed utilization and its associations with fertility and productive life in 11 commercial Pennsylvania tie-stall herds.

The objectives of this study were to quantify the relationships of various definitions of feed utilization with both fertility and productive life. Intake and body measurement data were collected monthly on 970 cows in 11 tie-stall herds for 6 consecutive months. Measures of feed utilization for this study were dry matter intake (DMI), dry matter intake efficiency (DME, defined as 305-d fat-corrected milk/305-d DMI), DME with intake adjusted for maintenance requirements (DMEM), crude protein efficiency (defined as 305-d protein yield/305-d crude protein intake), and 2 definitions of residual feed intake (RFI). The first, RFI(reg), was calculated by regressing daily DMI on daily milk, fat, and protein yields, body weight (BW), daily body condition score (BCS) gain or loss, the interaction between BW and BCS gain or loss, and days in milk. The second, RFI(NRC), was estimated by subtracting 305-d DMI predicted according to their fat-corrected milk and BW from actual 305-d DMI. Data were analyzed with 8-trait animal models and included one measure of feed utilization and milk, fat, and protein yields, BW, BCS, days open (DO), and productive life (PL). The genetic correlation between DME and DO was 0.53 (± 0.19) and that between DME and PL was 0.66 (± 0.10). These results show that cows who had higher feed efficiency had greater DO (undesirable) and greater PL (desirable). Results were similar for the genetic correlation between DO and crude protein efficiency (0.42). Productive life had genetic correlations of -0.22 with BW and -0.48 with BCS, suggesting that larger, fatter cows in this study had shorter PL. Correlations between estimated breeding values for feed utilization and official sire genetic evaluations for fertility were in agreement with the results from the multiple-trait models. Selection programs intended to enhance feed efficiency should factor relationships with functional traits to avoid unfavorable effects on cow fertility.

Heritability of gross feed efficiency and associations with yield, intake, residual intake, body weight, and body condition score in 11 commercial Pennsylvania tie stalls.

The objectives of this study were to calculate the heritability of feed efficiency and residual feed intake, and examine the relationships between feed efficiency and other traits of productive and economic importance. Intake and body measurement data were collected monthly on 970 cows in 11 tie-stall herds for 6 consecutive mo. Measures of efficiency for this study were: dry matter intake efficiency (DMIE), defined as 305-d fat-corrected milk (FCM)/305-d DMI, net energy for lactation efficiency (NELE), defined as 305-d FCM/05-d NEL intake, and crude protein efficiency (CPE), defined as 305-d true protein yield/305-d CP intake. Residual feed intake (RFI) was calculated by regressing daily DMI on daily milk, fat, and protein yields, body weight (BW), daily body condition score (BCS) gain or loss, the interaction between BW and BCS gain or loss, and days in milk (DIM). Data were analyzed with 3- and 4-trait animal models and included 305-d FCM or protein yield, DM, NEL, or CP intake, BW, BCS, BCS change between DIM 1 and 60, milk urea nitrogen, somatic cell score, RFI, or an alternative efficiency measure. Data were analyzed with and without significant covariates for BCS and BCS change between DIM 1 and 60. The average DMIE, NELE, and CPE were 1.61, 0.98, and 0.32, respectively. Heritability of gross feed efficiency was 0.14 for DMIE, 0.18 for NELE, and 0.21 for CPE, and heritability of RFI was 0.01. Body weight and BCS had high and negative correlations with the efficiency traits (-0.64 to -0.70), indicating that larger and fatter cows were less feed efficient than smaller and thinner cows. When BCS covariates were included in the model, cows identified as being highly efficient produced 2.3 kg/d less FCM in early lactation due to less early lactation loss of BCS. Results from this study suggest that selection for higher yield and lower BW will increase feed efficiency, and that body tissue mobilization should be considered.

Colostrogenesis: mass transfer of immunoglobulin G1 into colostrum.

Bovine IgG(1) is thought to be specifically transported by a process of transcytosis across the mammary epithelial cells during colostrogenesis. Mammary IgG(1) appearance in cow colostrum has typically been reported as a concentration and shows IgG(1) concentration to be extremely variable because of animal variation, colostrum milking time, and water dilution effects. To identify animal IgG(1) transfer capacity and separate it from the other effects, our objective was to determine first colostrum IgG(1) total mass. We collected 214 samples of totally milked first colostrum with recorded colostrum weights from 11 Pennsylvania dairy farms that participated in Pennsylvania Dairy Herd Improvement Association, analyzed colostrum for IgG(1) by ELISA, and calculated total IgG(1) mass. Median and mean concentrations of IgG(1) were 29.4 mg/mL and 37.5+/-30.2 mg/mL, respectively, with a range of 9 to 166 mg/mL. However, total mass of IgG(1) had a median of 209.1g, mean of 291.6+/-315.8 g, and a range of 14 to 2,223 g. Colostrum IgG(1) concentration showed no relationship with colostrum volume, but IgG(1) mass had a positive relationship with volume. Colostrum IgG(1) mass was related to IgG(1) concentration (R(2)=0.58). Using DHIA records for 196 animals, we established milk production for these animals to a 15-d equivalent. An established milk secretion relationship to mammary parenchyma tissue (secretory tissue) was calculated and showed no relationship of IgG(1) mass with mammary parenchyma tissue. In addition, we show that approximately 10% of the sampled animals had IgG(1) mass greater than 1 standard deviation above the mean (high mass transfer) and represented all parities tested (1-7). Whereas first-lactation animals showed less overall calculated parenchyma tissue when compared with other parities, approximately 10% of the first-lactation group animals were capable of high mass transfer, with one transporting 2,029 g into first colostrum. Concentration variance of IgG(1) can be attributed to water inclusion, whereas mass transfer provides a clear indication of animal IgG(1) transfer capacity. The specific mechanism of bovine mammary IgG(1) transfer is not clear, but secretory tissue mass does not explain the variation observed. We hypothesize that the animal variation is attributable to endocrine regulation or genetic variation of the transporter(s).

Genetic parameters of feed intake, production, body weight, body condition score, and selected type traits of Holstein cows in commercial tie-stall barns.

The objectives of this study were to determine the feasibility of measuring feed intake in commercial tie-stall dairies and infer genetic parameters of feed intake, yield, somatic cell score, milk urea nitrogen, body weight (BW), body condition score (BCS), and linear type traits of Holstein cows. Feed intake, BW, and BCS were measured on 970 cows in 11 Pennsylvania tie-stall herds. Historical test-day data from these cows and 739 herdmates who were contemporaries during earlier lactations were also included. Feed intake was measured by researchers once per month over a 24-h period within 7 d of 6 consecutive Dairy Herd Information test days. Feed samples from each farm were collected monthly on the same day that feed intake was measured and were used to calculate intakes of dry matter, crude protein, and net energy of lactation. Test-day records were analyzed with multiple-trait animal models, and 305-d fat-corrected milk yield, dry matter intake, crude protein intake, net energy of lactation intake, average BW, and average BCS were derived from the test-day models. The 305-d traits were also analyzed with multiple-trait animal models that included a prediction of 40-wk dry matter intake derived from National Research Council equations. Heritability estimates for 305-d intake of dry matter, crude protein, and net energy of lactation ranged from 0.15 to 0.18. Genetic correlations of predicted dry matter intake with 305-d dry matter, crude protein, and net energy of lactation intake were 0.84, 0.90, and 0.94, respectively. Genetic correlations among the 3 intake traits and fat-corrected milk yield, BW, and stature were moderate to high (0.52 to 0.63). Results indicate that feed intake measured in commercial tie-stalls once per month has sufficient accuracy to enable genetic research. High-producing and larger cows were genetically inclined to have higher feed intake. The genetic correlation between observed and predicted intakes was less than unity, indicating potential variation in feed efficiency.

Hormones and growth factors in milk.

Research dealing with hormones/growth factors in milk has progressed rapidly during the last 10 yr from their identification in milk to their regulation of various functions in the maternal organism and in the neonate. Many hormones, growth factors, and bioactive substances present in the maternal organism are present in colostrum and milk, often exceeding concentrations that occur in maternal plasma. Some appear in milk in different, sometimes multiple, forms from that found in maternal serum, reflecting to some extent synthesis and posttranslational processing by mammary tissue. Recent research has indicated that many milk hormones/growth factors survive the environment of the gut of the neonate, become absorbed into the neonatal circulation, and exert important functions in the neonate.

Effects of nucleotide supplementation in milk replacer on small intestinal absorptive capacity in dairy calves.

Milk replacer was supplemented with nucleotides and fed to dairy calves from birth through weaning to examine the potential for enhancing recovery of small intestinal function after enteric infection. Three treatments of 23 calves each were fed milk replacer (10% body weight/d) supplemented with no nucleotides (C), purified nucleotides (N), or nucleotides from an extract of Saccharomyces cerevisiae (S). Average daily gain, health scores, fecal dry matter, and fecal bacteria were monitored, and blood was analyzed for packed cell volume, glucose, blood urea nitrogen (BUN), and creatinine. Calves were monitored twice daily for fecal score, and 48 h after increased fecal fluidity was recorded, intestinal function was evaluated by measuring absorption of orally administered xylose (0.5 g/kg of body weight). Packed cell volume of blood was greater for treatment N for wk 2 and 5 compared with other treatment groups. Four calves per treatment were killed, and intestinal tissue was evaluated for morphology, enzyme activities, and nucleoside transporter mRNA expression. Treatment S calves had increased abundance of nucleoside transporter mRNA, numerically longer villi, and lower alkaline phosphatase than other groups. Growth measurements and plasma concentrations of glucose, BUN, creatinine, and IgG were not different between treatments; however, BUN-to-creatinine ratio was higher for treatment N, possibly indicating decreased kidney function. There were also no treatment effects on fecal dry matter and fecal bacteria population. However, N-treated calves had the highest detrimental and lowest beneficial bacteria overall, indicating an unfavorable intestinal environment. Supplementation of purified nucleotides did not improve intestinal morphology or function and resulted in higher fecal water loss and calf dehydration. Supplementation of nucleotides derived from yeast tended to increase calf intestinal function, provide a more beneficial intestinal environment, and improve intestinal morphology.

Characterization of Madin-Darby bovine kidney cell line for peroxisome proliferator-activated receptors: temporal response and sensitivity to fatty acids.

The peroxisome proliferator-activated receptors (PPAR) are critical for lipid metabolism, and many fatty acids are PPAR agonists. Madin-Darby bovine kidney (MDBK) cells were tested as an in vitro bovine model for PPAR activation, and preliminary evaluation of the effect of fatty acids on bovine PPAR was performed. Cells were treated with Wy-14643 (WY, specific PPARalpha agonist) and rosiglitazone (ROSI, specific PPARgamma agonist). The gene expression of specific PPARalpha-responsive genes such as carnitine palmitoyl transferase-1 (CPT1A) and acetyl coenzyme A oxidase (ACOX1) and of PPARgamma-responsive gene lipoprotein lipase (LPL) were analyzed using real-time reverse transcription PCR. It was found that CPT1A exhibited a significant increase in cells treated with WY, whereas the ACOX1 gene expression was not altered. The LPL gene expression showed an increase in response to ROSI. Interestingly, LPL was almost undetectable in MDBK cells not treated with ROSI. The potency of different fatty acids in activating PPARalpha as assessed by CPT1A mRNA abundance in MDBK cells was also tested. The mRNA of CPT1A (2.5- to 1.4-fold) was significantly increased by fatty acids in the order of palmitate > linolenate > linoleate > conjugated linoleate, and oleate. The results demonstrated MDBK cells to be responsive to PPAR agonists and thus a promising model to evaluate the role of PPAR in bovine cells. In addition, fatty acids were proven to have a different potency in modulating expression of CPT1A through PPARalpha.

The induction and activation of STAT1 by all-trans-retinoic acid are mediated by RAR beta signaling pathways in breast cancer cells.

Retinoic acid receptor-beta (RAR beta) and signal transducer and activator of transcription 1 (STAT1) are important mediators of the antiproliferative and apoptotic actions of retinoids and cytokines/growth factors, respectively. Expression of both RAR beta and STAT1 is lost in most breast cancer cell lines but it can be induced by retinoids in estrogen receptor-positive cells. We investigated a possible functional connection between these two mediators and present evidence supporting RAR beta as a tumor suppressor. First, by using different receptor-selective retinoids, we demonstrated that RAR beta induction in MCF-7 cells by all-trans-retinoic acid (atRA) was associated with the activation of STAT1 gene transcription. The direct involvement of RAR beta in atRA-induced STAT1 gene activation was further demonstrated by showing that transfection with an anti-sense RAR beta construct blocked atRA-induced STAT1 expression in MCF-7 cells whereas introduction of a sense-RAR beta construct resulted in STAT1 induction by atRA in MDA-MB 231 cells. In addition, we showed that STAT1 was phosphorylated/activated under atRA treatment of MCF-7 cells; this process required the involvement of RAR beta and protein synthesis. STAT1 phosphorylation/activation was accompanied by increased tyrosine kinase activity that was not due to the activation of JAK1, JAK2 or Tyk 2, suggesting the possible involvement of an unidentified tyrosine kinase.

Characterization of the change in type I and II insulin-like growth factor receptors of bovine mammary tissue during the pre- and postpartum periods.

Type I and II receptors for the insulin-like growth factors (IGF) were characterized in microsomes from bovine mammary tissue. Specific binding of [125I]IGF-I increased linearly with increasing microsomal protein concentrations. In contrast, IGF-II binding showed a curvilinear relationship over the concentration range tested, with a maximum at 120 micrograms/ml. Kinetic studies conducted at 4 C showed the binding reactions to be reversible. Competition studies showed recombinant human IGF-I (rh-IGF-I) to be 8-, 18-, and 1000-fold more potent at inhibiting [125I]rh-IGF-I binding than recombinant bovine IGF-II (rb-IGF-II), multiplication-stimulating activity, and insulin, respectively. rbIGF-II was 1.8- and 6-fold more potent at inhibiting [125I]rbIGF-II binding than rhIGF-II and multiplication-stimulating activity. Specific binding of [125I]IGF-I and -II was measured in microsomes prepared from cows (n = 47) ranging from 138 days prepartum to 411 days postpartum. IGF-I binding declined during the prepartum period, increased 75% with the onset of lactation, and then declined during the postpartum period. Scatchard analysis showed the presence of a single class of high affinity binding sites for both ligands, with type II receptors being about 10-fold more prevalent than type I receptors. The survey and Scatchard data support the conclusion that the onset of lactation coincides with an increase in the number of type I receptors present in mammary tissue. This increase supports the contention that IGF-I may play an important role in modulating the metabolic activity of the bovine mammary gland.

Perinatal expression of type I IGF receptors in porcine small intestine.

The gastrointestinal tract of the pig undergoes enhanced growth as well as morphological and functional differentiation during the perinatal period. Concurrently, porcine neonates ingest physiologically significant amounts of insulin-like growth factor-I (IGF-I) via colostrum and milk. The objectives of this study were to examine newborn pig small intestine for the presence of high affinity, IGF-I receptors and to evaluate the possible contributions of maternally derived and locally produced IGF-I to receptor-mediated postnatal growth of intestine. The specific binding of 125I-IGF-I to membranes prepared from scraped intestinal mucosa was time, temperature, and pH dependent; optimal conditions were 48 h, 4 C, and a pH of 7.8, respectively. Several pure peptides were evaluated for competition with 125I-IGF-I in binding to intestinal membrane sites. The relative order of competition was IGF-I greater than insulin-like growth factor-II (IGF-II) greater than insulin, whereas bombesin and epidermal growth factor were noncompetitive. Chemical cross-linking of 125I-IGF-I to binding sites, followed by denaturing SDS-PAGE and autoradiography, demonstrated labeled protein complexes of Mrs 135,000 and 260,000. Both autoradiographic bands were diminished when excess unlabeled IGF-I or IGF-II was included in the binding step. Insulin at higher concentrations also slightly inhibited labeling of both membrane proteins. Membranes prepared from intestinal mucosa of piglets at days 0 (less than 2-h old, colostrum-deprived), 3, 5, and 21 postnatal were evaluated for developmental variations in specific binding of 125I-IGF-I. Binding was highest at birth, declined (-43%) by day 3, remained low at day 5, and increased by day 21. Receptor affinity was relatively invariant whereas receptor number (per mg membrane protein) was variable. Intestine wt increased disproportionately to body wt between days 0 to 3, postnatal. Radioimmunoassay of extracts of the corresponding intestinal mucosa revealed a significant increase in content of IGF-I by day 3 (P = 0.05), whereas RNA dot-blot hybridization demonstrated low and unchanging IGF-I mRNA abundance in intestine. The quantitative variations in IGF-I protein content and IGF receptor numbers temporally coincide with intestinal villous growth, cessation of intestinal transport of macromolecules (closure), and onset of maturation of intestinal function.

Targeted expression of des(1-3) human insulin-like growth factor I in transgenic mice influences mammary gland development and IGF-binding protein expression.

To test the hypothesis that insulin-like growth factor I (IGF-I) regulates mammary gland development and lactation, the expression of both human (h) IGF-I and des(1-3)hIGF-I was targeted to the mammary gland in transgenic mice using a novel exon replacement strategy and the rat whey acidic protein (rWAP) gene regulatory sequences. Both transgenes expressed a 0.7-kilobase messenger RNA (mRNA). The abundance of WAP-IGE-I and WAP-DES mRNA on day 10 of lactation ranged from 0.2-1.0% and 0.2-13% of the endogenous mouse WAP mRNA, respectively. For WAP-DES mice, transgene expression was greatest from midpregnancy throughout lactation. Western blot analysis showed the presence of correctly processed hIGF-I in milk from these transgenic mice. This hIGF-I was capable of stimulating protein synthesis in cultured rat L6 myoblasts. Ligand blotting indicated changes in mammary gland secretion of IGFBP in response to WAP-DES expression. Histological analysis of mammary tissue from mice overexpressing des(1-3)hIGF-I showed incomplete mammary involution, ductile hypertrophy, and loss of secretory lobules associated with increased deposition of collagen. These changes are believed to occur through autocrine and paracrine effects of des(1-3)-hIGF-I on both epithelial and stromal cells.

Insulin-like growth factor-I and its association with binding proteins in bovine milk.

Immunoreactive insulin-like growth factor-1 (IGF-I in bovine milk was quantified. IGF-I was principally assoication with an approximately 45 kDa binding protein. In addition, a small fraction of IGF-I occurred at a molecular weight approximately the same as that of unbound IGF-I. Available binding sites existed on the approximately 45 kDa binding protein. Bound IGF-I was readily dissociated from binding protein by acid treatment. When IGF-I was estimated in milk obtained from primiparous and multiparous cows, mutiparous cows had a higher concentration (40 nmol/1) [corrected] at parturition than primiparous cows (19.2 nmol/1) [corrected]. By day 2 of lactation, IGF-I concentrations were 30 and 50% of initial estimates for multiparous and primiparous cows respectively. the final IGF-I concentration, on day 56 of lactation, was 4.5 nmol/1 [corrected] for combined parity groups. At parturition in multiparous cows, the mass of IGF-I was estimated at 183 and 157 nmol [corrected] for blood and milk pools respectively. Milk, therefore, represents a substantial pool of IGF-I in the cow. The mechanism of the appearance of IGF-I in bovine milk is unknown.

Effects of dietary recombinant human insulin-like growth factor-I on concentrations of hormones and growth factors in the blood of newborn calves.

Colostrum is rich in insulin-like growth factor-I (IGF-I) and IGF-II and the dietary effects of recombinant human IGF-I (rhIGF-I) on the newborn are of interest. The objective of this study was to examine the effects of dietary rhIGF-I upon selected hormones and growth factors in the blood. Calves were fed for the first 2 days of life with one of three experimental diets: (1) milk replacer plus isolated colostrum-derived globulin (MR-), (2) as (1) plus 98 mumol rhIGF-I/l (MR+) or (3) pooled cow colostrum. Thereafter, all animals received only milk replacer at 5% of body weight/feeding twice a day with only treatment 2 having the continued addition of 98 mumol rhIGF-I/l until completion of the experiment 7 days after birth. Radioimmunoassays for insulin, prolactin, IGF-I, IGF-II, GH, L-thyroxine, 3,5,3'-L-tri-iodothyroline and cortisol were conducted. With the exception of GH, all hormones and growth factors examined showed some form of dietary effect, but many were transient, changing only with the first feeding. Both insulin and prolactin concentrations exhibited a transient increase in blood at the first feeding, but insulin increased with the MR- treatment whereas prolactin increased with the MR+ treatment. Total IGF-I concentration in blood did not show any diet-induced changes for the first 4 days, but thereafter a rise in blood concentrations of IGF-I was observed. These data indirectly support the hypothesis that dietary IGF-I may be absorbed and causes transient systemic effects in the newborn calf.

Effects of elevated blood insulin-like growth factor-I (IGF-I) concentration upon IGF-I in bovine mammary secretions during the colostrum phase.

The objectives of these studies were to determine if the concentration of insulin-like growth factor-I (IGF-I) in mammary colostrum secretions could be altered through manipulation of IGF-I concentrations in blood and to compare the temporal changes of IGF-I in mammary secretions to those occurring for IgG1. Milking of 15 pregnant Holstein cows was stopped at 8 weeks prepartum and they were randomly assigned to one of three treatments. A control (C) treatment consisted of feeding the animals 100% of NRC requirements for protein and energy. A second group of cows was fed as the control group and injected with 1.8 mumol bovine GH/day. The third group was fed at 70% of NRC requirements for protein and energy to cause a moderate nutrient restriction (NR). Body weight was measured weekly. Blood was collected by tail venepuncture at 4 h intervals for 24 h. Mammary secretions were collected and pooled among contralateral front and rear quarters (diagonal) for measurement of volume, IGF-I and IgG1 concentrations. Samples were collected at -7, -5, -2, 0 and 1 week postpartum. Cows on the NR treatment failed to gain weight during the dry period compared with C cows (P < 0.05). Blood GH and IGF-I concentrations (P > 0.1) were unaffected by NR treatment. Cows treated with GH had higher (P < 0.01) serum GH and IGF-I levels throughout the entire treatment period, and higher serum IgG1 at 5 and 2 weeks prepartum (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in insulin-like growth factor-binding proteins in bovine mammary secretions associated with pregnancy and parturition.

The bovine mammary gland accumulates large quantities of insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) during late gestation which are secreted at parturition. The present study was conducted to determine the changes in the profiles of IGFBPs secreted by the mammary gland and in blood during late gestation and early lactation in dairy cows. Ligand blotting of serum and mammary secretions showed that IGFBPs of Mr 25,000, 30,000, 34,000, 42,000, 46,000 and greater than 200,000 were present in both fluids. The binding activity of the 42-46,000 Mr IGFBP predominated in prepartum mammary secretions and colostrum but was reduced postpartum. The binding activities of the 30,000 and 34,000 Mr IGFBPs, relative to other IGFBPs, were increased postpartum. Concentrations of IGF-I and IGF-II in mammary secretions declined from 347.1 and 181.1 nmol/litre 1 week prepartum to 0.7 and 0.3 nmol/litre 1.5 weeks postpartum. The volume of mammary secretions obtained was 0.109 litre and 6.690 litres at 1 week prepartum and 1.5 weeks postpartum respectively. In prepartum serum, the greatest binding activity was at Mr 42-46,000. The activity at this Mr decreased at parturition but was restored postpartum. The binding activities of the 30,000 and 34,000 Mr IGFBPs were increased around parturition. The 25,000 Mr IGFBP had minor activity during all periods. IGF-I concentrations decreased from 10.6 nmol/litres 1 week prepartum to 4.7 nmol/litres 1.5 weeks postpartum but IGF-II concentrations remained constant. In conclusion, IGFBP activity secreted by the mammary gland shifts from primarily Mr 42-46,000 prepartum to Mr 30,000 postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion of insulin-like growth factor-I (IGF-I) and IGF-binding proteins from bovine mammary tissue in vitro.

In vitro, insulin-like growth factor-I (IGF-I) promotes both growth and development of bovine mammary tissue. In vivo, the effects of IGF-I may encompass endocrine, paracrine or autocrine mediation. We addressed the possibility of paracrine/autocrine effects of IGF-I in the mammary gland by examining the in-vitro secretion of IGF-I and IGF-binding proteins (IGFBPs) from bovine mammary tissue. Bovine mammary explants from pregnant non-lactating and lactating non-pregnant animals were found to synthesize and secrete IGF-I and IGFBPs. Mammary acini cultures, representative of mammary secretory epithelia, secreted both IGF-I and IGFBP, but synthesized only IGFBP. Concentrations of IGF-I in conditioned media from explants were 1.54 and 0.72 fmol/micrograms DNA for pregnant and lactating animals respectively. Concentrations of IGFBPs in conditioned media from explants were similar for both physiological states at 2529 pmol 125I-labelled IGF-I bound/micrograms DNA. Ligand/Western blotting procedures identified four IGFBPs of 29, 33, 37 and 44 kDa for acini cultures and five IGFBPs of 28, 31, 36, 44 and 46 kDa for explant cultures. Similar affinities for IGF-I and IGF-II were shown by IGFBP, using 125I-labelled recombinant human IGF-I as the competing ligand (median effective dose (ED50) of 0.085 pmol). When 125I-labelled bovine IGF-II was used as the ligand, only bovine IGF-II (ED50 of 0.25 pmol) inhibited binding. The addition of prolactin, insulin and cortisol, with or without GH, did not affect secretion of either IGF-I or IGFBP. This report describes the ability of normal mammary tissue to synthesize and secrete IGF-I and IGFBPs.

The glycoprotein nature and antigenicity of a fungal D-glucosyltransferase.

D-Glucosyltransferase (EC 2.4.1.24) from Aspergillus niger has been prepared in pure form by chromatography on DEAE-cellulose. The enzyme transfers D-glucosyl units from maltose and other alpha-linked D-glucosyl oligosaccharides to glucosyl co-substrates resulting in the synthesis of new types of oligosaccharides. The glucosyltransferase has been found to be a glycoprotein containing 20% of carbohydrate consisting of mannose, glucose, and galactose. The carbohydrate residues are attached as either single units or as short oligosaccharide chains by O-glycosyl linkages to the serine and threonine residues of the protein. Antibodies directed against glucosyltransferase have been induced in animals by appropriate immunization regimes. These antibodies combine with the carbohydrate components of the enzyme and, therefore, the carbohydrate residues are the immunodeterminant groups of the glucosyltransferase.