Mammary transfer of hormones and constituents into secretions when cows were milked or secretions were samples prepartum

Continuous milking of dairy cows disrupts timing of peak IgG concentration appearance in mammary secretions

The length of the dry period in commercial dairy production is under close scrutiny. While the main concern is the composition and volume of milk produced, the evaluation of colostrum quality under these new paradigms has suggested a decline in IgG concentrations, while some reports indicate no change. Colostrum quality has been defined as an adequate concentration (>50 mg/ml) of immunoglobulin in the secretions to provide the newborn with maximal disease resistance. We investigated the appearance of IgG in mammary pre- and post partum secretions in cows without a dry period (continuously milked, Dry0) and compared the secretions with cows that experienced a dry period of 60 d (Dry60). Blood was collected during the experimental period and plasma analysed for progesterone (P4) and prolactin (Prl). Approximately −6 d relative to parturition, the Dry0 animals exhibited increased concentration of IgG in their secretions to an average of ∼35 mg/ml that remained rather constant through subsequent pregnancy and following parturition. Dry0 cows were producing an average IgG concentration in parturition colostrum of 44·2±17·6 mg/ml that was not different than that of controls (66·86±16·8 mg/ml). However, Dry0 cows exhibited high variation, different peak times (day) of IgG concentration including times that occurred both pre and post parturition. IgG mass of the Dry0 cows remained rather constant pre- and post partum and did not show the same declining mass following parturition that was shown for the Dry60 cows. The change in plasma P4 and Prl were shown to have no timing effect on colostrum IgG concentration.

Lactation driven dynamics of adiponectin supply from different fat depots to circulation in cows

Adipose tissue (AT) depots are heterogeneous in terms of morphology and adipocyte metabolism. Adiponectin, one of the most abundant adipokines, is known for its insulin sensitizing effects and its role in glucose and lipid metabolism. Little is known about the presence of adiponectin protein in visceral (vc) and subcutaneous (sc) AT depots. We assessed serum adiponectin and adiponectin protein concentrations and the molecular weight forms in vc (mesenterial, omental, and retroperitoneal) and sc (sternum, tail-head, and withers) AT of primiparous dairy cows during early lactation. Primiparous German Holstein cows (n = 25) were divided into a control (CON) and a conjugated linoleic acid (CLA) group. From day 1 of lactation until slaughter, CLA cows were fed 100 g of a CLA supplement/d (approximately 6% of cis-9, trans-11 and trans-10, cis-12 isomers each), whereas the CON cows received 100 g of a fatty acid mixture/d instead of CLA. Blood samples from all animals were collected from 3 wk before calving until slaughter on day 1 (n = 5, CON cows), 42 (n = 5 each of CON and CLA cows), and 105 (n = 5 each of CON and CLA cows) of lactation when samples from different AT depots were obtained. Adiponectin was measured in serum and tissue by ELISA. In all AT depots adiponectin concentrations were lowest on day 1 than on day 42 and day 105, and circulating adiponectin reached a nadir around parturition. Retroperitoneal AT had the lowest adiponectin concentrations; however, when taking total depot mass into consideration, the portion of circulating adiponectin was higher in vc than sc AT. Serum adiponectin was positively correlated with adiponectin protein concentrations but not with the mRNA abundance in all fat depots. The CLA supplementation did not affect adiponectin concentrations in AT depots. Furthermore, inverse associations between circulating adiponectin and measures of body condition (empty body weight, back fat thickness, and vc AT mass) were observed. In all AT depots at each time, adiponectin was present as high (approximately 300 kDa) and medium (approximately 150 kDa) molecular weight complexes similar to that of the blood serum. These data suggest differential contribution of AT depots to circulating adiponectin.

Prolactin-induced activation of nuclear factor kappaB in bovine mammary epithelial cells: role in chronic mastitis

We sought to determine whether prolactin (PRL) could influence the neutrophilic inflammation that characterizes chronic mastitis. Most of the genes encoding inflammatory proteins depend on the nuclear factor kappaB (NF-kappaB) for their expression. We addressed the hypothesis that immunomodulatory activities of PRL might arise from an increase in NF-kappaB activity. MAC-T cells, a bovine mammary epithelial cell line, were stimulated with increasing concentrations of bovine PRL (1, 5, 25, 125, and 1,000 ng/mL). Level of NF-kappaB binding activity was measured and mRNA was evaluated for IL-1beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GMCSF), IFN-gamma, and tumor necrosis factor (TNF)-alpha, cytokines known to require NF-kappaB for their maximal transcription. Prolactin activated NF-kappaB; maximal NF-kappaB activation was weaker with PRL than with TNF-alpha at 30 or 180 min poststimulation. In addition, PRL significantly amplified, in a dose-dependent manner, mRNA expression of IL-1beta, IL-6, IL-8, GMCSF, and TNF-alpha. We measured PRL concentrations in blood and milk from healthy and chronic mastitis-infected cows, and studied the relationship between the PRL concentration and the degree of inflammation in the mammary gland as indirectly assessed by somatic cell counts (SCC). Plasma PRL did not differ significantly between healthy and chronic mastitis-affected cows (63.7 and 67.5 ng/mL, respectively). Milk PRL concentration was significantly increased in chronic mastitis-affected quarters with the highest SCC, and had a positive significant correlation between SCC, as well as between the number of neutrophils present in milk samples. The present findings show that PRL promotes an inflammatory response in bovine mammary epithelial cells via NF-kappaB activation, and suggest a role for PRL in the pathogenesis of chronic mastitis.

17Beta-estradiol and estrone concentrations in plasma and milk during bovine pregnancy

Estrone (E1) and 17beta-estradiol (E2) are present in milk, but the mechanism(s) that regulate their appearance in milk are not known. The objectives of this study were to determine the impact of stage of pregnancy on the concentrations of E1 and E2 in plasma and milk and to determine the correlations between plasma and milk E1 and E2 and with milk components throughout pregnancy. Blood and milk samples were collected from 13 cows every 28 d throughout pregnancy. The E1 and E2 were quantified in plasma and milk using RIA after organic solvent extractions and Sephadex LH-20 column chromatography. Plasma E1 concentrations averaged 0.8, 16.9, and 41.8 pg/mL in trimesters 1, 2, and 3, respectively. The respective E1 concentrations in milk averaged 0.6, 7.9, and 27.1 pg/mL. The E2 concentrations in plasma averaged 0.5, 0.9, and 2.0 pg/mL; milk E2 averaged 0.3, 0.9, and 5.0 pg/mL. Plasma and milk E2 concentrations were greater in trimester 3 compared with trimesters 1 and 2. The E1 concentrations in milk were significantly correlated with plasma E1 concentrations (r = 0.77), percentage of milk fat (r = 0.50), and milk yield (r = -0.43). The E2 concentrations in milk were significantly correlated with plasma E2 concentrations (r = 0.93), percentage of milk protein (r = 0.63), and milk yield (r = -0.57). The milk-to-plasma ratio of E2 increased from 0.4 during trimester 1 to 2.2 in trimester 3, which suggested that the mechanism(s) regulating the appearance of E2 in milk may change over the course of pregnancy.

Dairy products and breast cancer: the IGF-I, estrogen, and bGH hypothesis

Research on the role of dietary factors in breast cancer causation has focused predominantly on fat intake. While some studies have examined associations between breast cancer rates and consumption of whole milk, there has been less attention given to dairy products in general. Dairy products contain both hormones and growth factors, in addition to fat and various chemical contaminants, that have been implicated in the proliferation of human breast cancer cells. This literature review evaluates the epidemiological and mechanistic evidence linking dairy consumption with breast cancer risk.

Post-partum, ovarian function in dairy cows as revealed by concentrations of oestradiol-17 beta and progesterone in defatted milk

Concentrations of oestradiol-17 beta and progesterone in defatted milk have been used to study the post-partum restoration of ovarian function in 52 autumn-calved dairy cattle. In 32 cows the first preovulatory peaks in oestradiol-17 beta concentration (indicative of imminent ovulation) were less than or equal to 15 days and in 49 cows less than or equal to 49 days post partum. Delay to first ovulation was mainly due, not to failure of ovarian secretion of oestradiol-17 beta at preovulatory level, but to failure of oestradiol-17 beta at this level to exert its normal preovulatory function. Longer intervals to first ovulation were associated with longer intervals from calving to the clearance of placental oestradiol-17 beta, high peak milk yields and high body weight losses, suggesting that in high-yielding dairy cows these factors (themselves inter-related) may be associated with others, which are the immediate cause of the inhibition of the normal, preovulatory function of oestradiol-17 beta. Forty-eight per cent of cows had short, first ovulation cycles. Ovarian function, comprising oestradiol-17 beta secretion at preovulatory level, normal preovulatory function of oestradiol-17 beta and normal corpus luteum progesterone secretion were almost fully restored in this herd by the 49th day post partum.

Effects of prepartum milking on milk production and health performance

A field study using seven Holstein herds was conducted to determine effects of prepartum milking on milk production, health disorders, and reproductive performance. In each herd, 80 cows (30% first lactation cows) were assigned 1 mo prior to expected calving date to one of two treatments: postpartum or prepartum milking. The group milked prepartum was machine-milked twice daily at regular milking intervals beginning 14 d prior to date of expected calving. The group milked postpartum was milked for the first time after calving. The day prior to calving, 36, 33, and 31% of the cows milked prepartum produced less than 4.5 kg, 4.5 to 9 kg, and greater than 9 kg of milk, respectively. No relationship existed between days milked prepartum and prepartum milk yield. Lactation milk yield and persistency were not affected by prepartum milking. Prepartum milking reduced incidence of milk fever and mastitis during the 1st mo after parturition. Treatment was not a significant source of variation for reproductive performance or body condition; however, culling was higher for cows milked postpartum. Results indicate no adverse effects on cow performance due to prepartum milking nor increase in lactation milk yield.

Secretion and mammary gland uptake of prolactin in dairy cows during lactogenesis

Mammary arteriovenous differences of prolactin concentration and net mammary uptake of prolactin from blood were quantified near parturition in 9 dairy cows. Six cows were milked once daily for at least 6 d before parturition, and prepartum lactogenesis occurred in 3 of 6 cows. Prepartum milking 2 or more d before parturition abruptly increased secretion of prolactin into blood, but milkings within 1 d before or after parturition did not increase prolactin secretion. Concentrations of prolactin in whole milk sampled over 8 d before parturition (64.5 ng/ml) were substantially greater than those occurring several days after parturition (19 ng/ml). Milk prolactin concentrations were unaffected by the successful induction of prepartum lactogenesis, which greatly increased prepartum yields of milk (2 to 8 kg/milking). Therefore, the alveolar lumenal content of prolactin was greatest in pregnant cows with prepartum lactogenesis. This enhanced content of intraalveolar prolactin before parturition was associated with an absence of mammary uptake of prolactin immediately prior to ejection of the prolactin-containing milk from the alveoli. However, prolactin uptake was quickly restored to about 2 micrograms/min per half udder shortly after milk ejection. During the prepartum period, an enhanced intraalveolar reservoir of 200 to 400 micrograms prolactin, due to induction of prepartum lactogenesis, appears to saturate temporarily all putative sites for uptake of prolactin from blood.

Effect of exogenous prolactin administration on lactational performance of dairy cows

Eight Holstein cows were utilized to examine the effect of prolactin on lactational performance prior to peak milk production (day 21-34 postpartum) and after peak milk production (day 60-73 postpartum). During each 14 day period, cows received daily intramuscular injections of pituitary-derived bovine prolactin (120 mg; 13.0 IU/mg protein) or excipient. Cows were housed in a controlled environment at 18.1C, 47.8% relative humidity and a 15 hr light: 9 hr dark cycle. In cows administered exogenous prolactin, circulating prolactin concentrations increased within one-half hr post injection, peaked within 2 to 6 hours and declined through the remainder of the day. Average prolactin concentration in the plasma was increased 2 to 5 fold over the 24 hr period in response to prolactin treatment. Yields of milk and milk components (fat, lactose and protein) were not affected by prolactin treatment in either period but the concentration of alpha-lactalbumin in milk was significantly increased (P less than .10) in both periods. Circulating concentrations of somatotropin, triiodothyronine, thyroxine, glucagon, nonesterified fatty acids and glucose were not altered. In prolactin-treated cows, the milking-stimulated prolactin release was decreased at both the PM milking, when circulating concentrations of prolactin were high, and the AM milking, when prolactin concentrations had returned to baseline. Concentration of prolactin in milk tended to increase but was not significantly altered by administration of exogenous prolactin. However, prolactin concentrations in plasma were correlated (r = .56) with milk concentrations. It is clear that postpartum administration of exogenous prolactin during the period of lactation prior to peak milk yield or after peak milk yield does not alter lactational performance in high producing dairy cows.

Effect of dry period versus continuous milking on periparturient concentrations of bovine prolactin in milk from half udders

Four multiparous cows were used to determine whether continuous twice daily milking of half the udder throughout the dry period would alter the prepartum accumulation of prolactin in secreted milk. The control half of each udder was allowed a dry period of 43 d, and twice daily milking was reinitiated in this half udder 11 d before parturition, whereas the treated half was milked continuously throughout. Milk from the treated half decreased to very low yields despite continuous milking, whereas concentrations of prolactin in milk remained low and without much day-to-day variation within each cow. Concentrations of prolactin in milk and yields of milk increased during the week before parturition in both halves of the udder, but there were no significant differences due to previous continuous milking. Therefore, prepartum accumulation of high concentrations of prolactin in secreted milk did not appear to depend on prior occurrence of a dry period. Elevated concentrations of prolactin in milk declined rapidly and equally in each half udder after parturition.

Prolactin in bovine milk near the time of calving and its relationship to premature induction of lactogenesis

Twenty-three primiparous heifers and pluriparous cows were milked once daily beginning 3 to 10 days before parturition. Retrospectively, they were divided into groups representing either successful or unsuccessful premature induction of lactogenesis, depending on milk production prior to calving. Successfully induced animals had prepartum milk yields greater than 4 kg/milking and unsuccessful animals yielded less. Ten of 23 animals satisfied the criterion for successful premature induction at 2.6 +/- .4 days before calving and 3.6 +/- .8 days after first milking and had peak prepartum yields of 7.9 +/- .7 kg/milking. Total number of prepartum days milked did not differ between successful and unsuccessful groups. Greater milk yield prepartum was significantly associated with higher milk prolactin concentration on days -6 to -4. Heifers had less milk yield than cows but did not differ in milk prolactin concentration or in total prolactin per milking. Premature induction of lactogenesis did not confer significant lactational benefits for more than 1 day postpartum or over the first 35 days postpartum. Premature induction of lactogenesis as a result of prepartum milking did not, as hypothesized, decrease the ability of mammary secretions to accumulate prolactin in large amounts. All groups rapidly lost this ability after parturition, suggesting that the hormonal environment of late pregnancy may promote the transfer of prolactin from blood into milk when there is regular removal of prepartum milk.

Oestrogens in milk

The steroid oestrogens oestradiol-17 beta, oestrone and oestradiol-17 alpha have all been adequately identified in various body fluids and tissues of cattle. There is also good evidence for the presence of oestrone sulphate. Oestriol (or similar triols) may also be present. The oestrogens found in the systemic plasma of cattle are present in milk in similar concentrations; whether their passage into milk involves metabolism by the mammary gland is uncertain. Oestrone sulphate, at least at relatively high levels of secretion, is believed to be found only in pregnant cattle and measurement of its concentration in milk is in use as a practical test for pregnancy. A close correlation has been found between the concentrations of oestradiol-17 beta in systemic plasma and milk of non-pregnant cows and levels of this oestrogen in milk may, together with those of progesterone, now be used in studies of post-partum ovarian function.

Relationships of hormones, temperature, photoperiod, and other factors to voluntary intake of dry matter in pregnant dairy cows prior to parturition

Voluntary intake of dry matter per 100 kg body weight (defined as intake) was quantified in 86 pluriparous Holstein cows which calved during 19 consecutive mo. Least squares techniques were used to examine the association of intake during the last 8 days before calving with numerous independent variables representing seasonal and physiological factors. The data were summarized as prepartum days 7, 4, and 1 (means of days 8 to 6, 5 to 3, and 2 to 0, respectively). Intake was lowest on prepartum day 1. Main effects of diet-group, health status, and month were not related significantly to intake when covariates were included in the statistical model. Intake decreased with increasing age of cows, but it was not related independently to body condition score. There were seasonal variations in intake which could be accounted for statistically by either month as a main effect or by quantitative indices of seasonality (temperature, photoperiod, plasma prolactin). Intake was lowest in February, June, and July and highest in October. Calf birthweight was related to intake in an unexpected manner. Intake was lowest in dams carrying either small or large calves. Prolactin of plasma was associated independently with intake, but this hormone may be just another measure of seasonal variation. All variables accounted for 58% of the total variance in intake. When seasonal variations in intake were accounted for statistically by other variables, none of the steroid hormones (progesterone, estrone, estradiol-17 beta, and estradiol-17 alpha) were associated independently with variation in voluntary intake. Associations of cow age and of climatic indices with intake were greater during days 7, 4, and 1 prepartum as compared to day 250 of gestation, days .5 to 2.5 postpartum, and days 3 to 30 of lactation.

Artificial induction of lactation in cattle: Effect of modified treatments on milk yield, fertility, and hormones in blood plasma and milk

Holsteins were divided into groups CON and IL, each with six dry cows and six heifers. Group CON calved in mid-summer when group IL was treated (kg body weight per day) with (a) progesterone (P; .25 mg) and estradiol-17beta (Ebeta), either .05 mg or .10 mg, for 7 days; (b) continued Ebeta at one-third the initial rate until udders were engorged; (c) then 12 injections (8-hr intervals) of TRH (each 200 mug) or saline; and (d) GnRH during lactation. Milk yield was not affected by Ebeta dose rate, TRH or GnRH. GnRH luteinized the persistent ovarian follicles in group IL, and pregnancy rates were 80% and 83% in groups IL and CON, respectively. Large differences (P < .01) between groups IL and CON were observed in plasma prolactin (IL-low), insulin (IL-high) and growth hormone (IL-low) wherein insulin was correlated (P < .01) negatively with milk yield between days 7 to 49 of lactation. Milk concentrations of P, Ebeta, estrone and estradiol-17alpha in group IL were no higher (P > .10) 14 days after the last injection of P or Ebeta than in group CON or in milk from the herd's bulk tank. The steroids were lowest in milk and plasma from ovariectomized cows. It was hypothesized that high insulin, as well as low prolactin and growth hormone, may contribute to inferior induced lactations.

Variables associated with peripartum traits in dairy cows. IV. Seasonal relationships among temperature, photoperiod, and blood plasma prolactin

Concentrations of prolactin in plasma were measured in 176 dairy cows and heifers from 13 days before calving to 2.5 days after calving over 21 mo. Prolactin averaged 35.1, 115.0, and 34.4 ng/ml prepartum (days -13 to -2), peripartum (days -1.0 to +.5), and postpartum (days +1.5 and +2.5). Season of the year affected prolactin in all periods. The linear covariate of daily photoperiod (hours of daylight per 24 h) accounted for as much variation in prolactin prepartum and postpartum as did linear covariates of both photoperiod and average daily temperature. However, it was possible to account for additional seasonal variation in prolactin peripartum by addition of the temperature covariate to the photoperiod covariate. Although photoperiod was related either directly or indirectly more than temperature to factors affecting prolactin seasonally, these statistical inferences cannot prove that prolactin is more dependent on photoperiod than on temperature because the two metereorological measures were correlated (r = .84). When the data were grouped for correlation analysis by months, correlations between temperature and prolactin among prepartum samples collected in the spring and in the fall were positive, small but significant.

Hormonal induction of lactation: estrogen and progesterone in milk

Estrogen and progesterone in milk during the first 21 days of induced and postpartum lactation in Holstein cows and heifers were estimated by assay procedures. Lactation was induced with estradiol-17 beta and progesterone treatment for 7 days. Estrogen and progesterone in induced lactations differed from concentrations in postpartum lactations. In early lactation estrogen was higher in postpartum milk (521 +/- 103 pg/ml on day 1) than in induced milk (336 +/- 46 pg/ml on day 1), but after day 7 the reverse was true (192 +/- 33 pg/ml and 233 +/- 32 pg/ml on day 7). Progesterone remained higher in induced lactation through the first 21 days than in postpartum lactation with the exception of day 19. Progesterone in postpartum milk increased from 4 +/- 1 ng/ml on day 1 to 11 +/- 2 ng/ml on day 21. Progesterone in induced milk showed greater fluctuation (11 +/- 3 ng/ml on day 1 and 22 +/- 9 ng/ml on day 3) but gradually decreased to 12 +/- 2 ng/ml on day 21 (11 +/- 2 ng/ml on day 21 of postpartum lactation).