Administration of prostaglandin F2α 14 d before initiating a G6G or a G7G timed artificial insemination protocol increased circulating progesterone prior to artificial insemination and reduced pregnancy loss in multiparous Holstein cows.

The objectives of this study were to determine the effect of PGF2α treatment 14 d before the initiation of a G6G or G7G (PGF2α, 2 d, GnRH, 6 or 7 d, Ovsynch) protocol on ovarian response, synchronization protocol on ovarian response, progesterone (P4) concentration, pregnancy per AI (P/AI), and pregnancy loss in multiparous Holstein cows. Cows (3.6±1.1 lactations and yielding >30kg/d of milk) were randomly assigned to 1 of 4 timed artificial insemination (TAI) protocols: 1) G6G (n=240), one injection of PGF2α, GnRH 2 d later and a 7-d Ovsynch protocol (GnRH, 7 d, PGF2α, 56 h, GnRH 16 h TAI) was initiated 6 d later; 2) PG6G (n=250), PGF2α 14 d before the initiation of the G6G protocol; 3) G7G (n=200), one injection of PGF2α, GnRH 2 d later, and a 7-d Ovsynch protocol initiated 7 d later; and (4) PG7G (n=200), a PGF2α injection 14 d before the initiation of the G7G protocol. Blood samples from a subset of 269 cows were collected at the times of first and second GnRH, and PGF2α of the Ovsynch protocol to measure P4. Ultrasound examinations were performed to evaluate ovarian response to GnRH and PGF2α of Ovsynch, and to determine pregnancy status at 32 and 60 d after TAI. The proportion of cows with high (≥1ng/mL) P4 at first GnRH of Ovsynch was greater for PG6G and PG7G compared with G6G and G7G groups (combined 79.7 vs. 59.3%). In addition, mean (±SEM) plasma P4 concentration (ng/mL) at PGF2α of Ovsynch was also greater in PG6G (6.5±0.2) and PG7G (6.7±0.3) compared with G6G (5.1±0.2) and G7G (5.0±0.2). Cows given PGF2α 14 d before initiating a G6G or a G7G TAI (PG6G and PG7G) tended to have a greater P/AI at 32 d compared with those cows not receiving PGF2α (G6G and G7G). However, P/AI at 60 d was greater in cows subjected to PG6G and PG7G protocols (31.1 vs. 39.2%), with a lower pregnancy loss between 32 and 60 d (11.65 vs. 19.7%). In summary, administration of PGF2α 14 d before initiating a G6G or a G7G TAI protocol increased P4 concentrations before artificial insemination and late embryonic/early fetal survival in multiparous Holstein cows.

Double-Ovsynch, compared with presynch with or without GnRH, improves fertility in heat-stressed lactating dairy cows.

The objective was to compare 3 timed artificial insemination (TAI) protocols in lactating dairy cows during heat stress. Multiparous Holstein cows yielding (mean ± SEM) 29.4 ± 0.3 kg of milk/d randomly were assigned to 1 of 3 TAI protocols at 34 ± 5.1 days in milk: 1) double-Ovsynch (DO; n = 486): the cows received GnRH-7d-2α-3d-GnRH and Ovsynch56 (GnRH-7d-PGF2α-56h-GnRH-16h-AI) was initiated 7 days later; 2) Presynch-GnRH-Ovsynch (PGO; n = 453): the cows received PGF2α-14d-PGF2α-2d-GnRH and Ovsynch56 was initiated 7 days later; and 3) presynch-Ovsynch (PO; n = 435): the cows received PGF2α-14d-PGF2α and Ovsynch56 was initiated 12 days later. The ovulatory response to the first GnRH of Ovsynch56 was higher in DO (65.0%) compared to PGO (53.2%) and PO (45.5%). Luteolytic response to PGF2α of Ovsynch was similar among TAI protocols (90.1%, 87.1%, and 86.2% for DO, PGO, and PO, respectively). Synchronization rate was greater in DO (86.2%) than in PGO (78.1%) and PO (72.1%) protocols. Irrespective of the TAI protocol, cows that ovulated in response to first GnRH had greater response to PGF2α (92.7 vs. 77.1%). Mean (±SEM) diameter (mm) of ovulatory follicle at TAI was larger in DO (16.1 ± 0.3) than PGO (15.6 ± 0.21) and PO (15.2 ± 0.12). Cows subjected to DO had greater P/AI at 32 days and at 60 days after TAI (26.6 and 24.4%) compared with those in PGO (21.4 and 20.0%) and PO (17.2 and 15.9%). However, TAI protocol had no significant effect on the incidence of pregnancy loss (6.1%, 6.6%, and 7.4% for DO, GO, and PO, respectively). In summary, cows in the DO protocol had a greater ovulation rate to the first GnRH and a greater synchronization rate, larger ovulatory follicles and greater P/AI. Of the 3 protocols used, DO yield the best reproductive performance in heat-stressed, lactating dairy cows.

The endometrial expression of prostaglandin cascade components in lactating dairy cows fed different polyunsaturated fatty acids.

Feeding n-6 polyunsaturated fatty acids (PUFA) increases the endometrial percentages of linoleic and arachidonic acids (AA), enhances the synthesis of prostaglandin F2α (PGF2α), and improves uterine health. In contrary, the n-3 PUFA, eicosapentaenoic acid, and docosahexaenoic acid may play pivotal roles by suppressing the synthesis of uterine PGF2α, a component being centrally involved in the control of the bovine estrous cycle and in early embryo survival. The objectives of the present study were to determine the effect of feeding a diet enriched in either α-linolenic acid (n-3) or linolenic acid (n-6) on the uterine expression of genes related to prostaglandin cascade and uterine release of PGF2α (measured as 13, 14-dihydro-15-keto PGF2α [PGFM]). From calving to 60 days in milk, cows (n = 24) were fed isonitrogenous, isocaloric, and isolipidic diets that differed in the ratio of n-3/n-6 PUFA. Treatments including palm oil ([PLM]; saturated FA, n = 8), soybean whole roast ([SOY]; n-6, n = 8), and linseed extruded ([LIN]; n-3, n = 8). At 30 days in milk, the ovulatory cycles of cows were synchronized using 2 injections of PGF2α with a 14-day interval. On day 15 postovulation, cows were injected with oxytocin and blood samples were collected to monitor the uterine release of PGF2α (measured as PGFM) and uterine endometrial biopsies were prepared to evaluate the expression of genes related to prostaglandin cascade (prostaglandin F synthase [PGFS], prostaglandin E synthase [PGES], prostaglandin endoperoxide synthase-2 [PGHS-2]), phospholipase A2 (PLA2), peroxisome proliferator-activated receptors [PPAR]). Results showed that uterine endometrial PPAR-δ genes were higher in cows fed LIN (3.17-fold) compared with cows fed PLM or SOY (P < 0.05). The messenger RNA (mRNA) level of PGES in the LIN group was threefold as high as those found in SOY and PLM diets (P < 0.05). The mean relative gene expression of PLA2 and PGFS was increased in animals fed the SOY diet (2.4- and 1.7-fold, respectively) compared with LIN and PLM diets (P < 0.05). The expression of mRNA for the PGHS-2, PPAR-α, and PPAR-γ was not influenced by the diet effect. Dietary inclusion of soy FAs was associated with an increase in the PGFM concentration, possibly through an increase in the expression of genes involved in prostaglandin cascade. The uterine concentration of PGFM, however, was decreased in cows fed diets containing n-3 FAs.

Plasma concentrations of PGFM and uterine and ovarian responses in early lactation dairy cows fed omega-3 and omega-6 fatty acids.

A total of 120 dairy cows were assigned randomly to three diets to determine the effects of omega-6 or omega-3 fatty acid (FA) supplementation on uterine diseases, ovarian responses, and blood concentrations of estradiol, progesterone, and PGFM in lactating Holstein dairy cows. Diets contained either protected palm oil (C), extruded linseed (L), or roasted whole soybeans (S), and they were fed from calving to Day 70 postpartum. Estrous cycles were synchronized and ovarian follicular development was monitored daily for an entire cycle. There were no differences among diets in the incidence of lameness, mastitis, or metritis, but the incidence of clinical endometritis was lower (P < 0.05) in cows fed S (0%) compared with cows fed C (28.2%) and L (20.5%). Uterine involution in cows fed S occurred 3.77 and 2.78 days earlier, respectively, than in those fed C and L. The PGFM response 60 minutes after an oxytocin challenge was highest for cows fed S and lowest for cows fed L. Mean plasma progesterone concentration on Day 15 of the synchronized cycle was higher in cows fed S (14.5 ng/mL) and L (15.0 ng/mL) than in those fed C (12.0 ng/mL). The ovulatory follicle on Day 21 of the estrous cycle (estrous = Day 0) was larger in cows fed S (16.1 ± 0.9 mm) and L (15.7 ± 0.7 mm) compared with cows fed C (13.2 ± 0.87 mm; P = 0.02) but there were no significant differences between cows fed diets S and L. The mean number of small and medium follicles and diameter of subordinate follicle were similar among diets. In conclusion, feeding a source of omega-6 FA can be a strategy to improve uterine health after calving, although a source of omega-3 FA such as L should be fed after uterine involution to decrease PGF2α secretion.