There are several findings indicating that the endocannabinoid system (ECS) is an important factor, acting in multiple ways in regulating reproductive function but changes of this system in the bovine endometrium have rarely been investigated; therefore, this study was designed to consider an association between endometrial ECS expression and different stages of the estrous cycles. MRNA expressions of the ECS were investigated during the late luteal phase and estrus using real-time PCR. Following estrous synchronization of sixteen Holstein dairy cows (34±1.3 kg/day of milk production), using two PGF2α injections given 14 days apart, at 30 and 44 days in milk (DIM), blood samples and ultrasonography (US) were performed every other day from the day of second PGF2α injection (44 DIM) until the start of the next estrous cycle (67±2 DIM) to verify CL development and ovulation. Based on blood and US results endometrial tissue was collected on days 16 (late luteal phase) and 21 (estrus) of the synchronized estrous cycle (ovulation = d 0). Real-time PCR analysis of ECS mRNA expression revealed endocannabinoid receptor (CNR2), diacylglycerol lipase (DAGL), cyclooxygenase-2 (COX-2), fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGLL) had significant fold differences when comparing two different stages of the estrous cycle (late luteal phase vs. estrus). CNR2 and DAGL showed 2.01 and 2.57 fold increase, respectively (P=0.04 and P=0.02), in estrous cows. Among the analyzed genes FAAH (P=0.01) and MGLL (P=0.02) were significantly down-regulated in estrous cows, with a 5.01- and 2.44-fold difference in mRNA expression, respectively. Overall, this study highlights an association between the expression of the ECS in the bovine endometrium and stage of the estrous cycle.
The aim was to evaluate the effect of presynchronization with GnRH and PGF2α prior to Ovsynch on ovulatory response to first GnRH, diameter of largest follicle at TAI and pregnancy per AI (P/AI) in multiparous dairy cows during summer. Cows (n=1069) were randomly assigned to one of three timed-AI (TAI) protocols. The TAI protocols were: 1) Ovsynch (O; n=425), GnRH- 7d-PGF2α-56h-GnRH-16h-TAI), 2) double-Ovsynch (DO; n=302), GnRH-7d-PGF2α-3d-GnRH and Ovsynch was initiated 7 days later, and 3) G7G-Ovsynch (G7G; n=342), PGF2α-2d-GnRH and Ovsynch was initiated 7 days later. Ovarian examinations were performed by transrectal ultrasonography during Ovsynch to determine ovulatory response to first GnRH and diameter of largest follicle at TAI. Presynchronization increased ovulatory response after first GnRH of Ovsynch (P=0.001), which was greater in DO (74.0%) and G7G (76.0%) groups compared to O group (50.0%). Means (±SEM) diameter (mm) of largest follicle at TAI was smaller in cows presynchronized before Ovsynch (DO and G7G, overall 15.7±0.3) compared to that in cows subjected to a standard Ovsynch without presynchronization (18.5±0.42). P/AI at 32 d after Al was greater (P=0.001) in G7G (32.7%) and DO (31.1%) groups compared to Ovsynch (19.7%) group. Presynchronization prior to Ovsynch also affected P/AI at 60 and 150 d after AI (P<0.05). In conclusion, DO and G7G protocols resulted in greater ovulatory response to first GnRH, smaller ovulatory follicles and greater P/AI compared to a standard Ovsynch protocol. Therefore, TAI protocols that include a presynchronization with GnRH and PGF2α prior to Ovsynch should be used in multiparous cows during summer to achieve acceptable reproductive performance.
The objective of this study was to investigate whether dietary supplementation with different polyunsaturated fatty acids (PUFA s) affects expression of genes related to somatotropic axis and the plasma concentrations of insulin, glucose, non-esterified fatty acids (NEFA), beta hydroxyl butyrate acids (BHBA) and insulin-like growth factor 1 (IGF1) and milk fatty acids profile. Right after calving, Holstein cows (n=45) were randomly assigned to one of three diets supplemented with roasted whole soybean as a source of omega-6 PUFA (omega-6, n=15), linseed as a source of omega-3 PUFA (omega-3, n=15) or palm oil (control, n=15). Each cow was in the study over a period of 70 days. Blood samples were collected every two weeks from day 1 to 70 of lactation and plasma concentrations of insulin, glucose, NEFA, BHBA and IGF1 were determined. Liver samples were taken from a subset of 18 cows (6 per diet) at day 70 postpartum and hepatic mRNA level of total growth hormone-receptor 1A (GHR1A), insulin receptor (INSR), IGF1 and insulinlike growth factor binding protein (IGFBP2) was assessed. Experimental diets did not affect milk yield. Plasma glucose and insulin concentrations were greater for omega-3 treatment compared to omega-6 and control treatments. Cows fed diets enriched in omega-3 exhibited greater INSR and GHR1A mRNA expression, and a tendency for greater IGF1 mRNA expression in the liver compared to omega-6 and control cows. Plasma IGF1 concentration was significantly higher in omega-3 treatment compared with omega-6 and control treatments. Results of this study suggest that feeding omega-3 PUFA s during early postpartum couples with the somatotropic axis, leading to an increase in plasma IGF1 concentration in dairy cows.
The objective of this study was to assess the efficacy of a single injection of Prostaglandin F2α (PGF2α) combined with or without GnRH before initiation of a Heatsynch protocol (GnRH-7d- PGF2α-2d-EB-1d-AI) on ovarian response and fertility in lactating Holstein cows. A total of 252 cows with a corpus luteum (CL; ≥10 mm) were assigned to one of three synchronization groups; 1 - Control (n=84), cows received two injections of PGF2α 14 days apart; 2 - Heatsynch with GnRH (PGH, n=88) the cows received PGF2α followed by GnRH four days later and then a Heatsynch protocol was initiated eight days after GnRH treatment; and 3 - Heatsynch without GnRH (PH, n=80) cows received a single injection of PGF2α followed by a Heatsynch protocol initiated 12 days after PGF2α. Cows detected in estrus were inseminated approximately 12 h after onset of estrus. Ovarian response and pregnancy diagnosis were determined by ultrasonography during the synchronization protocol and 30 days after AI, respectively. Results showed the percentage of cows with plasma P4≤0.4 ng/mL at AI were greater in PGH group compared to other groups (90.3 vs. 75.0%, P=0.03). The percentage of cows that ovulated in response to the GnRH injection of Heatsynch was affected (P<0.01) by synchronization protocol, because PGH cows were more likely to ovulate (77.2%) than PH (56.0%) cows. The proportion of cows displaying estrus was greater in PGH (70.4%) and PH (72.5%) groups compared with control (47.0%, P=0.04). Percentage of cows pregnant at 30 days after AI was (P=0.01) affected by synchronization treatment and was greater in PGH (45.16%) compared to control (25.0%) and PH (34.48%) groups. In summary, a short presynchronization that includes an injection of PGF2α and four days later GnRH increased fertility in Holstein cows subjected to a Heatsynch protocol. The enhanced fertility was due to a greater ovulatory response to GnRH of Heatsynch, more adequate plasma P4 concentrations during follicle development and a greater luteal regression following PGF2α prior to AI.
The aim of this study was to evaluate the effect of feeding oil supplement on mammary gland development and milk production responses in Holstein cows. Ten multiparous Holstein cows (42.2±9.2 d before calving, 3.25±0.25 body condition score, and 620±35 kg body weight) were randomly assigned to treatments. Treatments were a diet with oil added as palm oil (PO; n=5), or fish oil (FO; n=5) given to cows until 63 d in milk. Milk yield was recorded daily, milk composition (fat, protein, lactose, total solid and somatic cell count) was measured weekly and fatty acid profiles of milk fat were determined at first and last week of the experiment. Samples of mammary tissue were obtained at 7 and 63 d in milk by biopsy gun. Tissue slides were analyzed by Image J software. Results showed that fish oil supplemented diet compared to the palm oil supplemented diet increased milk production after 6 weeks of lactation (P<0.05), content of polyunsaturated fatty acids milk fat (P<0.05) and docosahexaenoic acid (P<0.01). Moreover, n-6:n-3 ratio was decreased by fish oil supplement (P<0.05). Histological studies showed that FO increased the relative percentage of tissue area occupied by epithelial cells as well as a number of total alveoli in each microscopic field (P<0.05). Data suggested that feeding fish oil during the dry period and early lactation could improve development and function of the mammary gland in the dairy cow.