Early genomic prediction of daughter pregnancy rate is associated with improved reproductive performance in Holstein dairy cows.

The use of genomic testing for selecting replacement heifers in commercial farms has recently attracted much attention. Fertility traits are among the most complex, hard to measure, and lowly heritable traits, and hence they can benefit the most from genomic testing. The objectives of this study were to assess the relationship between early genomic prediction of daughter pregnancy rate (GDPR) and pregnancy at the first service (P1), pregnancy at the end of lactation (PEND), number of services for conception (NSFC), days from calving to first service (TP1), and days open (TPEND). Data for GDPR, milk production, and reproductive outcomes from 1,401 multiparous and 3,044 primiparous Holstein cows from 4 commercial farms with the same reproductive management were used in the analyses. All animals were genotyped and genomically evaluated as heifers before first breeding, so no phenotypic data were available for predicting genomic merits. In addition, all animals were genotyped and evaluated as heifers before first breeding, so no phenotypic data were available for prediction. Data for GDPR and milk production were categorized in quartiles. The statistical models included GDPR, farm-year-season of the first insemination, milk yield, breeding code (estrus detection or timed artificial insemination), and the interaction terms as potential predictors for the different reproductive outcomes evaluated. Data were analyzed separately for primiparous and multiparous cows. The proportion of cows bred by estrus detection increased linearly from lowest to highest GDPR in primiparous cows. There were positive associations of GDPR for P1, PEND, NSFC, TP1, and TPEND in both primiparous and multiparous cows. For instance, positive GDPR effects in multiparous cows included a 15.7% higher P1 (47.6% vs. 31.9%), 11.9% higher PEND (84.9% vs. 73.0%), and 48.0-d shorter TPEND (139.8 vs. 175.7 d) for the highest quartile compared with the lowest quartile. Milk yield affected PEND in multiparous cows, and TPEND and NSFC affected PEND in primiparous cows. The only significant interaction between GDPR and milk production was detected for NSFC in primiparous cows, where high-producing cows showed a reduction in NSFC as GDPR increased, whereas low-producing cows showed no relationship between GDPR and NSFC. Overall, our findings show that GDPR can be effectively used as a predictor of future reproductive performance, reaffirming the potential benefits of applying early genomic predictions for making accurate early selection decisions.

Fertility in dairy cows following presynchronization and administering twice the luteolytic dose of prostaglandin F2α as one or two injections in the 5-day timed artificial insemination protocol.

The objectives were to evaluate pregnancy per AI (P/AI) of dairy cows subjected to the 5-day timed AI protocol under various synchronization and luteolytic treatments. Cows were either presynchronized or received supplemental progesterone during the synchronization protocol, and received a double luteolytic dose of PGF2α, either as one or two injections. In Experiment 1, dairy cows (n=737; Holstein=250, Jersey=80, and crossbred=407) in two seasonal grazing dairy farms were randomly assigned to one of four treatments in a 2×2 factorial arrangement. The day of AI was considered study Day 0. Half of the cows were presynchronized (G6G: PGF2α on Day -16 and GnRH on Day -14) and received the 5-day timed AI protocol using 1 mg of cloprostenol, either as a single injection (G6G-S: GnRH on Day -8, PGF2α on Day -3, and GnRH+AI on Day 0) or divided into two injections of 0.5 mg each (G6G-T: GnRH on Day -8, PGF2α on Day -3 and -2, and GnRH+AI on Day 0). The remaining cows were not presynchronized and received a controlled internal drug-release (CIDR) insert containing progesterone from GnRH to the first PGF2α injection of the 5-day timed AI protocol, and 1 mg of cloprostenol either as a single injection on Day -3 (CIDR-S) or divided into two injections of 0.5 mg each on Days -3 and -2 (CIDR-T). Ovaries were examined by ultrasonography on Days -8 and -3 and plasma progesterone concentrations were determined on Days -3 and 0. In Experiment 2, 655 high-producing Holstein cows had their estrous cycle presynchronized with PGF2α at 46±3 and 60±3 days postpartum and were randomly assigned to receive 50 mg of dinoprost during the 5-day timed AI protocol, either as a single injection or divided into two injections of 25 mg each. Pregnancies per AI were determined on Days 35 and 64 after AI in both experiments. In Experiment 1, presynchronization with G6G increased the proportion of cows with a CL on Day -8 (80.6 vs. 58.8%), ovulation to the first GnRH of the protocol (64.2 vs. 50.2%), and the presence (95.6 vs. 88.4%) and number (1.79 vs. 1.30) of CL at PGF(2α) compared with CIDR cows. Luteolysis was greater for two injections compared to a single PGF2α injection (two PGF2α=95.9 vs. single PGF2α=72.2%), especially in presynchronized cows (G6G-T=96.2 vs. G6G-S=61.7%). For cows not presynchronized, two PGF2α injections had no effect on P/AI (CIDR-S=30.2 vs. CIDR-T=34.3%), whereas for presynchronized cows, it improved P/AI (G6G-S=28.7 vs. G6G-T=45.4%). In Experiment 2, the two-PGF2α injection increased P/AI on Days 35 (two PGF2α=44.5 vs. single PGF2α=36.4%) and 64 (two PGF2α=40.3% vs. single PGF2α=32.6%) after AI. Presynchronization and dividing the dose of PGF2α (either cloprostenol or dinoprost) into two injections increased P/AI in lactating dairy cows subjected to the 5-day timed AI protocol.

Reproductive performance of grazing dairy cows following presynchronization and resynchronization protocols.

Objectives were to compare the effect of presynchronization and resynchronization methods on fertility responses of grazing dairy cows at first and second artificial insemination (AI) and pregnancy rate during the entire breeding season. Lactating dairy cows (n = 1,263) in 2 seasonal grazing farms were blocked, within farm, by parity, breed and days in milk. Within each block, cows were randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial with 2 presynchronization and 2 resynchronization treatments. Cows had their estrous cycles presynchronized with either a PGF(2α)-based program (Presynch) consisting of 2 injections of PGF(2α) administered 14 d apart and starting the timed AI protocol 11 d later, or with a PGF(2α)-GnRH-based presynchronization program (G6G) consisting of an injection of PGF(2α), followed 3 d later by an injection of GnRH and starting the timed AI protocol 6 d later. All cows received the first insemination on the same day, which was considered study d 0 and also d 0 of the breeding season. All cows received the 5-d timed AI protocol that consisted of GnRH on d -8, PGF(2α) on d -3 and -2, and GnRH+timed AI on d 0. Blood was sampled and analyzed for progesterone on d -8. On d 12, cows in each presynchronization treatment either remained as untreated controls (RCON) or received a controlled internal drug-release (CIDR) insert containing progesterone for 7 d (RCIDR). Estrus was observed daily starting on d 19 and cows in estrus were inseminated on the same day. On d 35, bulls were placed with the cows for an additional 65 d, completing a 100-d breeding season. Holstein cows were less likely to have progesterone ≥ 1 ng/mL on d -8, and had less expression of estrus and pregnancy per AI (P/AI), which resulted in a slower rate of pregnancy and a smaller proportion of pregnancy at the end of the study than did Jersey or crossbred cows. In addition, body condition, days in milk, and plasma progesterone concentration at the first GnRH injection of the timed AI protocol had marked effects on the reproductive performance of lactating grazing dairy cows. A greater proportion of G6G cows had progesterone ≥ 1 ng/mL at the first GnRH injection of the timed AI protocol compared with Presynch cows (82.0 vs. 74.3%). Presynchronization treatment did not influence P/AI, but cows in G6G had increased risk of pregnancy loss between d 30 and 65 after the first AI (12.9 vs. 8.1%). Nevertheless, an interaction between presynchronization and ovarian status was observed, and cows initiating the timed AI with progesterone ≥ 1 ng/mL had greater P/AI when previously treated with Presynch than G6G. On the other hand, G6G benefited P/AI of cows initiating the timed AI with progesterone < 1 ng/mL. Resynchronization with RCIDR altered the pattern of return to estrus, but it did not increase the rate of re-insemination and decreased the proportion of pregnant cows at the end of the 100-d breeding period (80.6 vs. 84.4%).

Effects of differential supplementation of fatty acids during the peripartum and breeding periods of Holstein cows: II. Neutrophil fatty acids and function, and acute phase proteins.

The objectives were to evaluate the effects of differential supplementation of Ca salts (CS) of fatty acids (FA) on plasma acute phase proteins and both FA composition and function (i.e., activity and cytokine production) of neutrophils, during the peripartum and breeding periods. Holstein cows were assigned randomly to receive either CS of palm (PO) or safflower (SO) oils from 30 d prepartum until 35 d postpartum (dpp) and CS of PO or fish oil (FO) from 35 to 160 dpp. Supplementation of CS of FA was at 1.5% of dietary dry matter. Cows (n=32) were sampled three times weekly from parturition to 35 dpp for analyses of plasma concentrations of haptoglobin and fibrinogen. Cows (n=47) were sampled for neutrophil phagocytic and oxidative burst activities toward Escherichia coli and Staphylococcus aureus, and neutrophil abundances of L-selectin and ß(2)-integrin assessed by flow cytometry at 32 d prepartum, within 7h after parturition, and 4 and 7 dpp. Profiles of FA in neutrophils and cytokine production (i.e., tumor necrosis factor alpha, TNF-α, and IL-1ß) were assessed prepartum (n=14), 35 (PO vs. SO; n=26) and 85 dpp (PO vs. FO; n=28). Plasma concentrations of haptoglobin and fibrinogen were greater for cows fed SO compared with PO. The percentage of neutrophils with phagocytic and oxidative burst activities was not affected by transition diets, but activities per neutrophil were greater in SO compared with PO diets at 4 (phagocytosis and oxidative burst) and 7 dpp (oxidative burst). Neutrophil abundance of L-selectin, but not ß(2)-integrin, was greater in SO compared with PO at 4 and 7 dpp. Neutrophil productions of TNF-α and IL-1ß were increased at 35 dpp in SO compared with PO diets, but production of TNF-α was attenuated in FO compared with PO at 85 dpp. Neutrophil ratios of n-6:n-3 FA were greater at 35 dpp in the SO diet and less at 85 dpp in FO compared with PO diets. In conclusion, cows supplemented with CS of SO had improved innate immunity (i.e., acute phase response and neutrophil function) to better cope with the bacterial challenges in the postpartum period. Conversely, CS of FO attenuated neutrophil cytokine production.

Effects of differential supplementation of fatty acids during the peripartum and breeding periods of Holstein cows: I. Uterine and metabolic responses, reproduction, and lactation.

The objectives were to evaluate the effects of differential timing of supplementation of different Ca salts (CS) of fatty acids (FA) on FA profiles of cotyledonary-caruncular tissues, metabolic status, uterine health, pregnancy, pregnancy losses after 2 artificial inseminations (AI), and milk yield. Holstein cows (n=1,380) were assigned randomly to be fed either CS of palm oil (PO) or safflower oil (SO) from 30 d prepartum until 30 d postpartum (dpp) and further randomized to receive either CS of PO or fish oil (FO) from 30 to 160 dpp. Supplementation of CS of FA was at 1.5% of dietary dry matter. Tissues (n=23) and blood (n=32) were collected from a subsample of cows. Blood was collected daily from parturition to 10 dpp and three times weekly thereafter until 30 dpp for analyses of PGF2α metabolite, nonesterified FA, ß-hydroxybutyric acid, blood urea nitrogen, and glucose. Cows were evaluated once between 8 to 10 dpp for cervical discharge type. At 43 dpp, cows received 2 injections of PGF2α 14 d apart, followed 14 d later by injections of GnRH at 7 d before and 56 h after an injection of PGF2α with AI at 16 h after the second GnRH injection. All cows received intravaginally a controlled internal drug-releasing device, containing 1.38 g of progesterone, at 18 d after the first AI followed 7 d later by removal of the device and injection of GnRH. Nonpregnant cows at 32 d after AI were injected with PGF2α, followed 56 h later with a GnRH injection and second AI 16 h thereafter. Cows diagnosed pregnant after both AI were re-examined at 60 d of pregnancy to determine pregnancy losses. Milk weights were recorded monthly for all cows. Caruncular n-6:n-3 FA ratio was greater in cows fed SO. Plasma concentrations of metabolites and frequency of cervical discharge type did not differ between PO- and SO-fed cows. Plasma PGF2α metabolite was greater in SO-fed cows at 4 and 7 dpp. Pregnancy per AI at 32 and 60 d post first AI was not affected by diets, but pregnancy loss was less in FO-fed cows. At second AI, pregnancy was greater in FO-fed cows at 32 d and in SO-FO-fed cows at 60 d post AI. Pregnancy loss after second AI was not affected by diets. Overall pregnancy per AI was greater in cows fed SO followed by FO at 60 d of pregnancy and pregnancy loss was reduced in FO-fed cows. Monthly milk yield was greater (0.7 kg/d) in SO-fed cows. In conclusion, strategic feeding of CS of FA during transition and breeding periods can benefit fertility and milk production of lactating dairy cows.

Perspective on physiological/endocrine and nutritional factors influencing fertility in post-partum dairy cows.

Increasing reproductive performance of post-partum lactating dairy cows is a multi-factorial challenge involving disciplines of production medicine, nutrition, physiology and herd management. Systems of programmed timed insemination have been fine-tuned to achieve pregnancy per artificial inseminations (AI) approximating 45%. Systems have optimized follicle development, integrated follicle development with timing of induced corpus luteum regression and fine-tuned sequential timing of induced ovulation and AI. Use of programmes for insemination have identified occurrence of anovulatory ovarian status, body condition, uterine health and seasonal summer stress as factors contributing to reduced herd fertility. Furthermore, programmes of timed insemination provide a platform to evaluate efficacy of nutritional and herd health systems targeted to the transition and post-partum periods. The homeorhetic periparturient period, as cows deal with decreases in dry matter intake, results in a negative energy balance and is associated with a period of immunosuppression. Cows that transition well will cycle earlier and have a greater risk of becoming pregnant earlier post-partum. The innate arms of the immune system (acute and adaptive) are suppressed during the periparturient period. Cows experiencing the sequential complex of disorders such as dystocia, puerperal metritis, metritis, endometritis and subclinical endometritis are subsequently less fertile. Targeted strategies of providing specific nutraceuticals that provide pro- and anti-inflammatory effects, such as polyunsaturated fatty acids (e.g., linoleic, eicosapentaenoic/docosahexaenoic, conjugated linoleic acid), sequential glycogenic and lipogenic enrichment of diets, and organic selenium appear to differentially regulate and improve the immune and reproductive systems to benefit an earlier restoration of ovarian activity and increased fertility.

Supplementation with calcium salts of linoleic and trans-octadecenoic acids improves fertility of lactating dairy cows.

Objectives were to evaluate effects of feeding a calcium salt rich in linoleic and trans-octadecenoic acids (LTFA) on synthesis of prostaglandin F(2alpha) based on its metabolite (PGFM), uterine involution and pregnancy rates in lactating dairy cows. Five hundred and eleven Holstein cows were blocked according to parity, body condition score and milk yield in the previous lactation. Primiparous and multiparous cows were randomly assigned to one of the two treatments consisting of calcium salt (2% diet dry matter) of either palm oil (PO) or LTFA from 25 days prepartum to 80 days of lactation. Cows were time-inseminated at 70 +/- 3 days postpartum. Feeding LTFA tended (p = 0.08) to decrease the incidence of puerperal metritis (15.1% vs 8.8%). Primiparous cows supplemented with LTFA showed larger increase in plasma PGFM concentration at day 1 postpartum (17018 vs 6897 pm). Pregnancy rate after first insemination tended (p = 0.07) to be greater at 27 days after insemination (37.9% vs 28.6%), and was greater (p = 0.05) at 41 days after insemination (35.5% vs 25.8%) for cows fed LTFA compared with PO. These results indicate that unsaturated fatty acids fed in a rumen inert form have the potential to modulate reproductive events and improve pregnancy rates in lactating dairy cows.

Use of increasing doses of a degradable Deslorelin implant to enhance uterine involution in postpartum lactating dairy cows.

Holstein cows received, subcutaneously 1 (1DESL, n=15) or 2 (2DESL, n=12) degradable implant containing 2.1mg of the GnRH agonist Deslorelin or no implant (CON, n=18) within 1.5 days postpartum (dpp). Previous pregnant (PPH) and non-pregnant (PNPH) uterine horns were determined by palpation per rectum. Cows were examined by ultrasonography at 8dpp, 15dpp, 22dpp, 29dpp, and 36dpp (S.E.=1 day) to record ovarian structures, cervical diameter, uterine horns cross-section and lumen diameters, myometrial and endometrial widths. Uterine tone was recorded before ultrasonography. Vaginoscopy was conducted just after ultrasonography for cervical discharge score. At 44dpp cows were inserted with a CIDR followed 7 days later by its removal and injection of PGF(2alpha) 8h later, followed by the Ovsynch 10 days after for timed artificial insemination (TAI). Plasma was analyzed for PGFM daily from parturition to 14dpp and for P(4) trice weekly until 44dpp. Additionally, strategic blood samples were collected during the synchronization protocol to determine whether estrous cyclicity was occurring and ovulation status before and after TAI, respectively. Cows in 1DESL and 2DESL groups had more class 1 follicles (P<0.01), less class 2 (P<0.01) and class 3 follicles (P<0.01) compared with CON. First increase of P(4), indicative of ovulation, occurred in CON (55.5%) cows at 28dpp (S.E.=9 days) and in 1DESL (13.3%) treated cows at 43dpp (S.E.=3). Plasma concentrations of P(4) were suppressed completely in all 2DESL-treated cows before initiation of estrous synchronization. Diameters of PPH (P<0.01), PNPH (P<0.01), uterine horn lumens (P<0.01) were less in the 1DESL and 2DESL groups with greater uterine tone (P=0.07). Frequency distribution of cervical discharge categories did not differ among groups. Proportion of cows with estrous cycles and having ovulations was less (P<0.01) in DESL implant cows compared with CON that was to a greater (P<0.01) extent in the 2DESL. Treatment with Deslorelin during postpartum (1) suppressed follicular development, (2) enhanced physical involution of the uterus, (3) increased tone of the uterine wall, (4) delayed first ovulation and reduced responsiveness to a synchronization of ovulation protocol. Future research should focus in GnRH agonist delivery systems to restrict duration of treatment to optimize uterine involution and avoid a prolonged period of anovulation.

Postpartum suppression of ovarian activity with a Deslorelin implant enhanced uterine involution in lactating dairy cows.

Holstein cows received, subcutaneously a non-degradable implant containing 5mg of the GnRH agonist Deslorelin (DESL) or no implant (CON) at 2+/-1 days postpartum (dpp). All cows were injected with PGF(2alpha) at 9 dpp. Previous pregnant (PPH) and non-pregnant uterine horns (PNPH) were determined by palpation per rectum. In Experiment 1, cows [DESL implant (n=10) and CON (n=9)] were examined by ultrasonography to record ovarian structures (23, 30 and 37 dpp) and uterine horn and cervical diameters (16, 23, 30 and 37 dpp). Uterine tone was scored before ultrasonography. Vaginoscopy was conducted just after ultrasonography examination to assess cervical discharge and color of the external cervical os. Blood samples were collected on a weekly basis for hormonal analyses. In Experiment 2, cows [DESL implant (n=77) and CON (n=70)] were palpated per rectum and vaginoscopy at 30 dpp for scoring of uterine tone, uterine horns, cervical diameter, and discharge. Blood samples were collected only at 9 dpp. In Experiment 1, DESL-implant-treated cows had more Class 1 follicles (P<0.01), less Class 2 (P<0.01) and Class 3 follicles (P<0.01) and no corpus luteum (CL) formation (P<0.01). In CON cows, six of nine animals had visible CL at 25+/-7 dpp. At 9 dpp plasma concentration of E(2), P(4) (P<0.01) and PGFM (P<0.05) were less in the DESL-implant treatment group. Diameter of PPH (P<0.01), PNPH (P<0.01) and cervix (P=0.08) were less in the DESL-implant treatment associated with greater uterine tone (P=0.07). The DESL-implant cows had a greater frequency of clear cervical discharge (P=0.09) and pink cervical os (P=0.06). In Experiment 2, plasma concentrations of PGFM were less at 9 dpp in DESL-implant treatment (P<0.01). Diameters of the PPH (P<0.01) and PNPH (P<0.01) were less and more uterine tone (P<0.01) in the DESL-implant treatment. Diameter of cervix and frequency of a cervical discharge score did not differ between treatments. Treatment with non-degradable Deslorelin (5mg) implant during postpartum: (1) suppressed ovarian follicular development, (2) enhanced physical involution of the uterus and cervix, (3) increased tone of the uterine wall, (4) decreased frequency of purulent cervical discharges, and (5) reduced inflammatory processes of the reproductive tract.

Reproductive responses following postpartum suppression of ovarian follicular development with a deslorelin implant during summer heat stress in lactating dairy cows.

The objective was to evaluate pregnancy rate to a timed artificial insemination (TAI) protocol in the autumn for cows treated with a non-degradable GnRH agonist implant (Deslorelin [DESL], 5mg) during the summer heat stress period compared with non-treated controls (CON). Cows were randomly assigned to receive or not a DESL implant within 1-4 days postpartum (dpp) twice weekly, from 25 June through 8 August 2001. All cows in DESL implant and CON treatments were injected with PGF(2alpha) 7 days after enrollment. Ultrasonography (US) monitored numbers of ovarian follicles and corpus luteum (CL) at approximately 10, 30, 35/36, 45/44, 56/55 and 66/63dpp, while DESL implants were in situ and concurrently CON, respectively. DESL implants were removed at two specific days, 28 August and 4 September. Cows had DESL implant in situ for a range of 28-67 days, depending on date of enrollment and implant removal. Within 61-100dpp, 31 days after implant removal, DESL implant and CON cows were initiated in a Presynch-Ovsynch and TAI protocol. Pregnancy was evaluated by US and palpation per rectum at 28 and 46 days after TAI, respectively. Plasma concentrations of progesterone were analyzed for sets of blood samples collected during the Presynch-Ovsynch and at TAI day followed 8 days later. Cows in the DESL-implant treatment had more (P<0.01) Class 1 (3-5mm) follicles, less (P<0.01) Class 2 (6-9mm), Class 3 (> or =10mm) follicles and CL compared with CON cows. Proportion of cows having initiated estrous cycles after calving was less (P<0.01) in the DESL-implant treatment (52.2%, 58/111) compared with CON (93.7%, 104/111) at the beginning of Ovsynch. Pregnancy rate to TAI was less (P<0.01) in the DESL implant (27.5%, 33/120) compared with CON (53.9%, 69/128). Pregnancy rate to TAI was less (P<0.01) in DESL-implanted cows that had initiated estrous cycles after calving (30.6%, 19/62) compared with CON (53.7%, 65/121) cows having initiated estrous cycles after calving. Furthermore, pregnancy rate was less (P<0.01) for cows having ovulations that had initiated estrous cycles after TAI in the DESL implant (39.1%, 18/46) compared with CON (62.1%, 54/87) treatments. Pregnancy losses from day 28 to day 46 of pregnancy did not differ between DESL implant (15.1%, 5/33) and CON (13.0%, 9/69) treatments. The DESL implant induced a delay in initiation of a new wave of follicular development during the postpartum-heat stressed period. The lesser pregnancy rate in the DESL-implant treatment group may be due to a pool of heat stress damaged follicles that were depleted in the control group with re-occurring follicle waves.

Effects of method of presynchronization and source of selenium on uterine health and reproduction in dairy cows.

The objectives of this study were to evaluate the effects of method of presynchronization and source of supplemental Se on uterine health and reproductive performance of lactating dairy cows. Holstein cows (n = 512) were assigned randomly to 2 methods of presynchronization, Presynch (2 PGF(2a) given 14 d apart) or CIDR-PS (controlled internal drug releasing inserted for 7 d with an injection of PGF(2a) at removal) and 2 sources of Se, sodium selenite (SS) or selenized yeast (SY) supplemented at 0.3 mg/kg from 25 d before calving to 80 d in milk (DIM) arranged in a 2 x 2 factorial. Cows were inseminated following the Ovsynch protocol (d 0 GnRH, d 7 PGF(2a), d 9 GnRH, timed artificial insemination (AI) 12 h after the final GnRH) starting at 12 and 3 d after Presynch and CIDR-PS, respectively. Cows were diagnosed for pregnancy at 28, 42, and 56 d after AI. Source of Se did not influence uterine health and resumption of cyclicity, but fewer CIDR-PS than Presynch cows were cyclic at the beginning of the Ovsynch, although differences in the proportion cyclic may have been caused by the timing when corpus luteum evaluations were performed in the different pre-synchronization treatments. Ovulatory responses were not influenced by source of Se. However, the CIDR-PS increased ovulation to the first GnRH, double ovulation to the final GnRH, and size of ovulatory follicle at PGF(2a) and final GnRH of the Ovsynch, but did not influence ovulation at the final GnRH of the Ovsynch. Concentrations of estradiol during the Ovsynch increased with follicle diameter and were greater for cows receiving CIDR-PS than Presynch, but they were not influenced by source of Se. Pregnancy per AI on d 28 (32.7%), 42 (28.5%), and 56 (25.9%) after AI, and pregnancy loss (20.5%) from 28 to 56 d were not influenced by source of Se or method of presynchronization. Although cows receiving CIDR-PS had an increased incidence of ovulation to the first GnRH (73.2 vs. 57.8%) and double ovulation to the final GnRH of the Ovsynch (18.7 vs. 9.0%), both of which enhanced pregnancy, the CIDR-PS protocol did not improve pregnancy per AI or reduce pregnancy loss compared with presynchronization with PGF(2a) alone.

Long chain fatty acids of diet as factors influencing reproduction in cattle.

Cattle are fed moderate amounts of long chain fatty acids (FA) with the objective to enhance lactation and growth; however, recent interest on lipid feeding to cows has focused on reproduction, immunity and health. Increasing the caloric density of the ration by fat feeding has generally improved measures of cow reproduction, but when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not always observed. Feeding fat has influenced reproduction by altering the size of the dominant follicle, hastening the interval to first postpartum ovulation in beef cows, increasing progesterone concentrations during the luteal phase of the oestrous cycle, modulating uterine prostaglandin (PG) synthesis, and improving oocyte and embryo quality and developmental competence. Some of these effects were altered by the type of FA fed. The polyunsaturated FA of the n-6 and n-3 families seem to have the most remarkable effects on reproductive responses of cattle, but it is not completely clear whether these effects are mediated only by them or by other potential intermediates produced during rumen biohydrogenation. Generally, feeding fat sources rich in n-6 FA during late gestation and early lactation enhanced follicle growth, uterine PG secretion, embryo quality and pregnancy in cows. Similarly, feeding n-3 FA during lactation suppressed uterine PG release, and improved embryo quality and maintenance of pregnancy. Future research ought to focus on methods to improve the delivery of specific FA and adequately powered studies should be designed to critically evaluate their effects on establishment and maintenance of pregnancy in cattle.

Effects of dietary unsaturated fatty acids on oocyte quality and follicular development in lactating dairy cows in summer.

Dietary sources of fatty acids were evaluated for their influence on oocyte quality and follicular development using 54 lactating cows in summer. Fat supplements were 1) sunflower oil (80% cis 18:1), 2) Ca salt of transoctadecenoic acids (57% trans 18:1), 3) Ca salt of vegetable oils (30% 18:2), and 4) linseed oil (56% 18:3 and 16% 18:2). Fats were fed at 1.35% of dietary dry matter beginning at 5 wk prior to expected calving date and at 1.5% (oils) and 1.75% (Ca salts) of dietary dry matter for 15 wk after parturition. Four days following a programmed induced ovulation, 5 transvaginal oocyte aspirations were performed 3 or 4 d apart. Three days after the last aspiration, PGF2alpha was injected, followed 3 d later by a GnRH injection and a timed artificial insemination (d 0) 16 to 20 h later. For the first 4 aspirations, oocytes grading 1 or 2 were used for in vitro embryo production. Total cell number and the proportion of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive blastomeres were analyzed at d 8. At the fifth aspiration, the occurrence of metaphase II, group II caspase activity, and TUNEL labeling were determined after oocyte maturation. A total of 1,011 oocytes were collected. The proportion of oocytes with high caspase activity was greater for grade 3 compared with grades 1 and 2 (37.5 vs. 1.54 and 1.61%). Feeding polyunsaturated fatty acids, as compared with monosaturated fatty acids, failed to affect oocyte quality, as demonstrated by subsequent embryo development. Cows fed 18:2- or 18:3-enriched diets had a larger preovulatory follicle at insemination and subsequent volume of the corpus luteum compared with those fed cis 18:1 or trans 18:1 diets (16.8, 16.2 vs. 15.0, 14.9 +/- 0.7 mm; 7,323, 8,208 vs. 6,033, 5,495 +/- 644 mm3, respectively). The previously documented benefits of polyunsaturated fatty acids on reproductive performance appear to reflect actions at alternative biological windows in lactating dairy cows.

Pregnancy, bovine somatotropin, and dietary n-3 fatty acids in lactating dairy cows: I. Ovarian, conceptus, and growth hormone-insulin-like growth factor system responses.

The objective was to examine effects of bovine somatotropin (bST), pregnancy, and dietary fatty acids on reproductive responses in lactating dairy cows. Beginning at approximately 17 d in milk (DIM), a comparison was made of isoenergetic diets comprising supplementary lipids of whole cottonseed vs. calcium salts of fish oil enriched lipid (FO). Ovulation was synchronized in cows with a presynchronization plus Ovsynch protocol, and cows were inseminated artificially by appointment or not inseminated (d 0 = time of synchronized ovulation; 77 +/- 12 DIM). On d 0 and 11, cows received bST (500 mg) or no bST. All cows were slaughtered on d 17. Number of cows in each group was as follows: control diet had 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows; and cyclic cows fed FO diet had 4 bST-treated (bST-FO) and 5 non-bST-treated cyclic (no bST-FO-C) cows. Feeding FO increased milk production, number of class 1 follicles (2 to 5 mm), and decreased insulin during the period before d 0 compared with control-fed cows. The bST increased milk production, pregnancy rate [83% (5/6) vs. 40% (4/10)], conceptus length (45 vs. 34 cm), and interferon-tau in the uterine luminal flushings (9.4 vs. 5.3 microg) with no effect on interferon-tau mRNA concentration in the conceptus. Treatment with bST increased plasma growth hormone (GH) and insulin-like growth factor (IGF)-I. Among control-fed cows (cyclic and pregnant), bST decreased progesterone concentration in plasma. Cows fed FO had less plasma insulin than control-fed cyclic cows, and FO altered the plasma GH (bST-FO > bST-C) and IGF-I (bST-C > bST-FO-C) responses to bST injections. Endometrial IGF-I mRNA was reduced in pregnant cows and tended to decrease in those fed FO. The IGF-II mRNA was increased in the endometrium of pregnant and bST-treated cows fed the control diet. Cows fed FO had increased concentrations of IGF-II mRNA, when bST was not injected. The insulin-like growth factor binding protein-2 (IGFBP-2) mRNA was increased in bST-P cows, whereas bST decreased the IGFBP-2 mRNA in all cyclic cows. In summary, bST and FO seemed to modulate reproductive responses that may be beneficial to the developing conceptus and pregnancy rate.

Resynchronization of ovulation and timed insemination in lactating dairy cows I: use of the Ovsynch and Heatsynch protocols after non-pregnancy diagnosis by ultrasonography.

The objective was to compare pregnancy rates and pregnancy losses in lactating dairy cows that were diagnosed not pregnant and re-inseminated following either the Ovsynch or Heatsynch protocols. Also evaluated were the effects of stages of the estrous cycle, ovarian cysts and anestrus on pregnancy rates for both treatments. Non-pregnant cows (n = 332) as determined by ultrasonography on day 27 post-AI (study day 0) were divided into two groups. Cows in the Ovsynch group (n = 166) received GnRH on day 0, PGF2alpha on day 7, GnRH on day 9, and timed AI (TAI) 16 h later (day 10). Cows in the Heatsynch group (n = 166) received GnRH on day 0, PGF2alpha on day 7, estradiol cypionate (ECP) on day 8, and TAI 48 h later (day 10). Cows detected in estrus on days 8 and 9 were inseminated and included in the study. On day 0, cows were classified according to different stages of the estrous cycle, or presence of ovarian cysts or anestrus. Pregnancy rates were evaluated 27, 45 and 90 days after resynchronized AI. Overall, there was no difference in pregnancy rates on days 27, 45 and 90 between cows in the Ovsynch (25.2, 17.5, and 13.9%) and Heatsynch (25.8, 19.9, and 16.1%) groups. There was no difference in pregnancy losses from days 27 to 45 and days 45 to 90 for cows in the Ovsynch (25.0 and 17.9%) and Heatsynch (14.7 and 10.3%) groups. However, pregnancy rates were increased when cows in metestrus were subjected to the Heatsynch protocol and cows with ovarian cysts were subjected to the Ovsynch protocol.

Resynchronization of ovulation and timed insemination in lactating dairy cows, II: assigning protocols according to stages of the estrous cycle, or presence of ovarian cysts or anestrus.

Pregnancy rates were compared in lactating dairy cows (n = 1083) assigned to protocols for resynchronization of ovulation based on stages of the estrous cycle, or presence of ovarian cysts or anestrus. Cows were detected not pregnant by ultrasonography 30 d after a previous AI (study day 0) and classified as diestrus, metestrus, proestrus, with ovarian cysts or anestrus. Cows in diestrus (January-May) were assigned to either Ovsynch (GnRH day 0, PGF2alpha day 7, GnRH day 9, and timed-AI [TAI] 16 h later; n = 96), or Quicksynch (PGF2alpha day 0, estradiol cypionate [ECP] day 1, AI at detected estrus [AIDE] on day 2, or TAI on day 3; n = 96). Cows in diestrus (June-December) were assigned to either Ovsynch (n = 156) or Modified Quicksynch (PGF2alpha day 0, ECP day 1, AIDE days 2 and 3, and to Ovsynch on day 4 if not detected in estrus; n = 142). Cows in metestrus were assigned either to Ovsynch (n = 68), Heatsynch (GnRH day 0, PGF2alpha day 7, ECP day 8, AIDE day 9, or TAI day 10; n = 62), or GnRH + Ovsynch (GnRH on day 0, followed by Ovsynch on day 8; n = 64). Cows in proestrus, with ovarian cysts, or anestrus were assigned to either Ovsynch (proestrus n = 89, ovarian cysts n = 97, anestrus n = 8) or GnRH + Ovsynch (proestrus n = 87, ovarian cysts n = 109, anestrus n = 9). Pregnancy rate was evaluated 30, 55 and 90 d after resynchronized AI. For cows in diestrus (January-May), pregnancy rates were higher for Ovsynch (35.9, 29.2 and 26.0%) than for Quicksynch (21.7, 16.7 and 15.6%). For cows in diestrus (June-December), pregnancy rates were similar for Ovsynch (34.4, 24.0 and 23.6%) and Modified Quicksynch (27.1, 26.2 and 21.6%). For cows in metestrus, pregnancy rates were higher for GnRH + Ovsynch (33.3, 24.5 and 20.3%) than for Heatsynch (20.3, 12.9 and 9.8%). For cows with ovarian cysts, pregnancy rates were higher for GnRH + Ovsynch (30.3, 26.6 and 22.9%) than for Ovsynch (20.2, 18.5 and 14.7%). Assignment to resynchronization protocols based on the stages of the estrous cycle, or presence of ovarian cysts improved pregnancy rates.