Estrogen dynamics and hormonal differences associated with lactational performance of cows induced to lactate

Estrogen Regulates Glucose Metabolism in Cattle Neutrophils Through Autophagy

Hypoglycemia resulting from a negative energy balance (NEB) in periparturient cattle is the major reason for a reduced glycogen content in polymorphonuclear neutrophils (PMNs). The lack of glycogen induces PMNs dysfunction and is responsible for the high incidence of perinatal diseases. The perinatal period is accompanied by dramatic changes in sex hormones levels of which estrogen (17β-estradiol, E2) has been shown to be closely associated with PMNs function. However, the precise regulatory mechanism of E2 on glucose metabolism in cattle PMNs has not been elucidated. Cattle PMNs were cultured in RPMI 1640 with 2.5 (LG), 5.5 (NG) and 25 (HG) mM glucose and E2 at 20 (EL), 200 (EM) and 450 (EH) pg/mL. We found that E2 maintained PMNs viability in different glucose conditions, and promoted glycogen synthesis by inhibiting PFK1, G6PDH and GSK-3β activity in LG while enhancing PFK1 and G6PDH activity and inhibiting GSK-3β activity in HG. E2 increased the ATP content in LG but decreased it in HG. This indicated that the E2-induced increase/decrease of ATP content may be independent of glycolysis and the pentose phosphate pathway (PPP). Further analysis showed that E2 promoted the activity of hexokinase (HK) and GLUT1, GLUT4 and SGLT1 expression in LG, while inhibiting GLUT1, GLUT4 and SGLT1 expression in HG. Finally, we found that E2 increased LC3, ATG5 and Beclin1 expression, inhibited p62 expression, promoting AMPK-dependent autophagy in LG, but with the opposite effect in HG. Moreover, E2 increased the Bcl-2/Bax ratio and decreased the apoptosis rate of PMNs in LG but had the opposite effect in HG. These results showed that E2 could promote AMPK-dependent autophagy and inhibit apoptosis in response to glucose-deficient environments. This study elucidated the detailed mechanism by which E2 promotes glycogen storage through enhancing glucose uptake and retarding glycolysis and the PPP in LG. Autophagy is essential for providing ATP to maintain the survival and immune potential of PMNs. These results provided significant evidence for further understanding the effects of E2 on PMNs immune potential during the hypoglycemia accompanying perinatal NEB in cattle.

Artificial induction of lactation in cattle: initiation of lactation and estrogen and progesterone concentrations in milk

Thirty heifers were given 11 subcutaneous injections of 5 mg estradiol benzoate and 200 mg progesterone every 3 d to develop their mammary glands. Three days later groups of animals were treated with 1) 20 mg dexamethasone twice, 2) 500 micrograms cloprostenol thrice, 3) dexamethasone and cloprostenol, 4) oxytocin 4 IU six times, or 5) no further injections. Two further groups of six heifers each (6 and 7) were treated in a manner similar to groups 1 and 3 except the dose of estrogen to develop their mammary glands was doubled to 10 mg/3 d. Six lactating first calf heifers were controls (8). The proportion of animals lactating, combined milk yield for each group (kg), and mean days lactated were 1) 5/6, 3831, 142; 2) 1/6, 912, 195; 3) 6/6, 4898, 194; 4) 3/6, 1066, 128; 5) 1/6, 293, 154; 6) 6/6, 6109, 130; 7) 6/6, 6265, 130; and 8) 6/6, 19, 190, 251. The lactogenic response to dexamethasone and oxytocin is similar to that in sheep, but the response to cloprostenol indicates a species difference. Intensive blood sampling before and after injection of hormones, intended to trigger lactogenesis, showed that plasma prolactin rose to peaks above 210 ng/ml in cows of groups 2, 3, and 4 and were unchanged from the base below 40 ng/ml in groups 1 and 5. Monitoring of steroids after induction treatment showed estradiol-17 beta ranged between 35 and 400 pg/ml and 20 to 80 pg/ml in mammary secretion and plasma and progesterone concentrations were less than at diestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Induced lactation in dairy ewes by various brief hormone treatments

Hormonal induction of lactation in 40 nonpregnant dairy ewes was attempted by daily injecting subcutaneously 25 mg estradiol-17 beta and 70 mg progesterone for 7 consecutive days. After an interval of 7 days the following treatments were applied: group I (10 ewes), nothing; group II, (10 ewes), 10 mg dexamethasone and 30 mg prednisolone; group III (10 ewes), 10 mg dexamethasone, 30 mg prednisolone, 400 IU insulin; and group IV (10 ewes), 10 mg dexamethasone, 30 mg prednisolone, 400 IU insulin, and 40 mg prostaglandin F2 alpha. Hand milking was initiated at day 16. Thereafter, ewes were milked twice daily for 60 days, and milk yields were recorded and sampled twice weekly for measuring fat, pH, acidity, specific gravity, total solids, lactose, and chloride content. Mean yield of milk of ewes in II was larger than of ewes in I and IV. Four ewes in I, 8 ewes in II, 5 ewes in III, and 3 ewes in IV out of 10 ewes in each group produced more than 200 ml milk daily. The peak milk yield of ewes in I was at day 43, in II at day 28, in III at day 7, and in IV at day 11 of the milking period. Injection of corticoids in the induction scheme of estrogen and progesterone resulted in greater lactogenic response and yields of milk, but injections of insulin or insulin and prostaglandin F2 alpha diminished these responses.

Induction of lactation by two techniques: success rate, milk composition, estrogen and progesterone in serum and milk, and ovarian effects

Induction of lactation was attempted in 12 heifers and 12 cows with estradiol benzoate (.011 mg/kg body weight per day) subcutaneous for 10 days or that plus progesterone (.1 mg + .25 mg/kg body weight per day) for 7 days. Milking commenced on day 20 for those treated with the mixture and on day 11 for the others. Lactations were induced (minimum of 4.5 kg of milk/day) in five of six heifers and two of six cows by the mixture and in six of six heifers and three of six cows for estradiol benzoate. Milk production was 44% of herdmates in the 16 induced lactations. Cows on the single treatment had lower production than the other three groups. Ovarian status, cycling, cystic, or static, was affected adversely in 5 of 16 animals induced successfully. Two of the 16, both heifers, carried calves to term following induction. The transition to normal composition of milk was slower for single than double treatment. Lactose increased slowly to normal over the 1st wk of milking while protein decreased slowly. Estrogen and progesterone in milk of induced cows were approximately twice as concentrated as in normal postparturient cows, probably because milk production was halved.