AI Conception Rate Research Articles

Effect of High Energy Diet Supplementation during Periparturient Period on Ovarian Steroids and Reproductive Performance in Vrindavani Cows

The objective of the study was to assess the effect of high energy diet supplementation during periparturient period on ovarian steroids and reproductive performance in vrindavani cows. Postpartum vrindavani cows (n= 20) of second to fourth parity with lactation yield of > 10 L/day were divided in to two groups (n=10 cow/group). Group I (CON) cows were fed with basal diet to serve as control. Group II (TRT) cows were provided with 20% extra concentrates in the form of energy. 20% additional concentrate diet was supplemented from second week to eight week after calving. Blood samples were collected at weekly interval from 4 week before calving to8weeks after calving. Blood samples were collected to determine estradiol (E2) and progesterone (P4) in the serum using RIA. Postpartum reproductive performance was assessed in terms occurrence of first postpartum estrus, calving to conception interval, conception rate and number of service per conception. Serum estradiol and progesterone concentration increased significantly(P<0.05) from 2 to 8 week postpartum in Group II as compared to Group I. Marked significant(P<0.05)improvement in the postpartum reproductive performance in terms of early occurrence of first postpartum estrus(67.0Vs 53.0), reduced calving to conception interval(85.87 Vs74.4), service per conception (1.62 Vs 1.2), days from calving to first AI(88.5 Vs 65.73), higher first AI conception rate(40 Vs 80%) and cumulative conception rate(88.52 Vs 65.73%) in group II as compared to group I. In conclusion, additional high energy diet supplemented group showed significant increased ovarian steroid hormonal concentrations and marked improvement in the reproductive performance in Vrindavani cows.

Reproductive screening and enhancement of reproductive performance of buffaloes (Bubalus bubalis) on feeding bypass fat and area specific mineral mixture

A total of 491 buffaloes (Murrah and non-descript) reared under unorganized system from semi-arid and arid areas of Rajasthan, India, were screened for their reproductive status. These were screened by history taking, rectal palpation, Ultrasonography and follow up. Out of these screened animals 65.59% were of normal reproductive status (Involved recently parturiated, pregnant etc. animals) while remaining included 11% cases of delayed puberty, 7.94% of delayed post-partum estrus, 5.5% of anestrus/ subestrus, 3.87% of repeat breeding, 2.85% of prolapse, 2.44% of infectious infertility and only 0.81% cases were of cystic ovarian degeneration (COD). Thirty animals were given bypass fat and area specific mineral mixture (ASMM) following parturition till 90 days postpartum, and results were compared with 20 animals from Control group. The uterus of animals given bypass fat and ASMM took significantly less time (24.50±0.34 mean days) for involution than Control group (33±0.61 mean days) also Experimental group took significantly less days (62.60±0.77 mean days) to show first estrus postpartum than Control group (87.00±0.44 mean days). First AI conception rate of Experimental group (60%) was also better than Control group (45%).

Evaluation of Cryoprotective, Cryocapacitation Inhibitory and Fertility Enhancing Potential of RU-486, Sericin and Taurine in Cattle and Buffalo Semen

Background: Artificial insemination with frozen semen is of great value for livestock breeding and improvement. However, the procedure of cryopreservation leads to varying degree of oxidative and cryodamage to sperms deteriorating its quality, capacitation status and fertility. Hence, a variety of protocols, cryoprotectants and additives have been tried to protect sperms from such damages. This study was aimed to evaluate the antioxidant and cryocapacitation inhibitory potential of Mifepristone, Sericin and Taurine in routine extender on cryopreserved bull semen including in vivo fertility. Methods: Semen ejaculates of 3 Gir and 3 Murrah bulls with greater than 75% initial motility were split-diluted @ 100 million spermatozoa ml-1 using TFYG extender without and with Mifepristone (10 µg/ml), Sericin (5 mg/ml) and Taurine (4 mg/ml) and frozen in LN2 using a programmable biofreezer. The freshly diluted as well as frozen-thawed samples were assessed for sperm motility, viability, plasma membrane integrity, CTC (chlortetracycline) fluorescence assay and seminal plasma oxidative markers. The straws frozen as above were used to inseminate 100-375 cows and/or buffaloes with each treatment involving well trained field AI technicians. Conception rates were determined based on confirmation of pregnancy per-rectum 45-60 days after first AI in non-return cases. Result: The mean percentages, on dilution and at post-thaw stage in particular, of motile, live, HOS reactive and non-capacitated sperm were significantly (p less than 0.01) higher with reduced lipid peroxidation (MDA, SOD and GPx) whereas capacitated and acrosome reacted sperm were lower in Mifepristone supplemented extender than in control extender and the values for Sericin and Taurine fortified extender were intermediary in both the species. The first AI conception rates obtained for Gir and Murrah bull semen cryopreserved in control extender and extender supplemented with Mifepristone, Sericin and Taurine were 44.48, 51.11, 47.22 and 48.72% in cattle and 44.44, 55.40, 51.57 and 52.05% in buffaloes, respectively, suggesting that all additives used and Mefipristone in particular can be advantageously incorporated in the semen extender for cryopreservation of both cattle and buffalo semen.

Seasonal variation in semen quality and conception rate of Jaffarabadi buffalo bulls (Bubalus bubalis) in India

The study was conducted on four Jaffarabadi breeding bulls, 5 to 6 years old, to know the neat characteristics based on total of 192 semen ejaculates evaluated and cryopreserved during winter (10 to 25°C mean temperature) of November to February (n=96 ejaculates) and summer (38 to 45°C temperature) March to June (n=96 ejaculates). The neat seminal characteristics of Jaffarabadi bulls, viz., ejaculate volume (ml), colour/density (score), sperm concentration (million/ml), mass activity (score), initial motility (%), live sperm (%), abnormal sperm (%), HOST reactive sperm (%) and acrosomal integrity (%), first AI conception rate observed during winter season were 5.19±0.18, 2.38±0.10, 1253.36±24.75, 3.73±0.05, 80.31±0.05, 86.20±0.64, 5.00±0.40, 85.75±0.43, 93.56±0.56, 45.75±0.21 respectively, whereas the respective values in summer were 5.07±0.13, 2.00±0.00, 1186.60±24.78, 3.72±0.11, 78.75±0.46, 82.31±0.74, 7.13±0.52, 84.93±0.45, 90.56±0.23, 43.50±0.11. The semen quality of fresh samples was observed better during winter compared to summer season for use in breeding program with satisfactory first AI conception rate.

19 Evaluation of Fixed-time Artificial Insemination and Estrus Expression in Angus-cross Heifers with Female Sex-sorted Semen Using 6-day and 7-day CIDR Protocols at Multiple Time Intervals

Abstract The objective was to investigate the influence of progesterone exposure time and breeding time on fixed-time artificial insemination (FTAI) protocols using sex-sorted semen in Angus-cross heifers (n = 85; mean BW = 324 kg.). Heifers were assigned randomly into four treatment groups. Treatments 1 and 2 used a 6-day CO-synch + controlled internal drug release (CIDR) protocol with gonadotropin releasing hormone (GnRH) administration and CIDR insertion on day 0 and prostaglandin F2α (PGF) administration on day 6, upon simultaneous CIDR removal. Treatment 1 heifers underwent FTAI 72 h post CIDR removal, and Treatment 2 heifers underwent FTAI 80 h post CIDR removal. Treatments 3 and 4 used a 7-d CO-synch + CIDR protocol with GnRH administration and CIDR insertion on d 0 and PGF administration on d 7, upon simultaneous CIDR removal. Treatment 3 heifers underwent FTAI 54 h post CIDR removal, and Treatment 4 heifers underwent FTAI 62 h post CIDR removal. Estrus expression was determined using an estrus detection patch (Estrotect™, Rockway Inc., Spring Valley, WI). Estrus expression was classified as a patch with 50% or more of the color rubbed off and the absence of estrus expression as a patch with less than 50% of the color rubbed off. All heifers were inseminated using female sex-sorted semen from a single Angus sire (SexedULTRA 4M™, STgenetics, Navasota, TX). Pregnancy was determined by ultrasound 57 d following FTAI. Pregnancy rates and patch scores were analyzed using the GLIMMIX procedure of SAS 9.4 with treatment as a fixed effect. There was no effect of treatment on the first service AI rates (P = 0.91) or on estrus expression (P = 0.17) in heifers. In conclusion, the combinations of progesterone and breeding time in this study did not affect first service AI conception rates or estrus expression in beef cattle heifers.

Sexual Behaviour and Seminal Attributes Associated with Fertility of Jaffarabadi Buffalo Bulls

Background: The selection of breeding bulls based on the association of sexual behaviour, seminal attributes and conception rate are more important and economical. However, information on association of sexual behaviour and seminal attributes with fertility in buffaloes particularly with reference to Jaffarabadi buffalo bulls is meager. Methods: The study was carried out to assess the association of sexual behaviour and seminal attributes with first service conception rate (FCR) of Jaffarabadi buffalo bulls. A total of 192 semen ejaculates were evaluated and cryo-preserved. First AI conception rate (FCR) was carried out on 800 Jaffarabadi female buffaloes inseminated with frozen-thawed semen and pregnancy was confirmed by per rectal palpation at 2 months post-insemination. Result: The results indicated that both sexual behaviour and seminal attributes were associated with fertility in Jaffarabadi buffalo bulls.

61 Effects of fescue cultivar on performance of beef cow/calf pairs grazed on summer stockpiled tall fescue pastures

Abstract This 2-year experiment evaluated productivity of wild-type endophyte-infected tall fescue (KY-31) and novel endophyte-infected tall fescue (MaxQ) summer stockpiled (SS) pastures and the performance of fall-calving beef cow/calf pairs grazed on each cultivar. Pregnant Simmental x Angus cows (128 total, 64 each year) were stratified by BW, BCS, and expected calving date, then allotted to 1 of 10 groups. Forage growth was stockpiled from April to initiation of strip-grazing on 31 August of 2017 and 2018. Cows grazed treatment pastures for 52 d from 23 ± 14 d prepartum to 29 ± 14 d postpartum, and calved on treatment pastures. Forage quadrats were clipped from the grazed and ungrazed portions of each pasture to determine weekly forage mass (FM). Total ergot alkaloid (TEA) concentrations were analyzed for all pastures at the beginning of the experiment and every subsequent 2 weeks for KY-31. Cow BW was recorded on 2 consecutive d and BCS determined at the start and end of the experiment. In year 2, ultrasound 12th rib fat thickness (BF) was measured at the beginning and end of the treatment period Milk production was estimated using the weigh-suckle-weigh technique at 29 ± 14 postpartum. In year 1, TEA concentrations for KY-31 pastures did not differ (P < 0.48) over time. Fescue cultivars were not different (P ≥ 0.15) in forage CP, TDN, and grazed or ungrazed FM. Cow BW, BCS, and BF at the beginning and end of grazing were not different (P ≥ 0.41) by treatment. Milk production was higher (P < 0.01) for KY-31 grazed cows. Calving date, calf BW, calf ADG were not different (P ≥ 0.65) by treatment. Neither AI nor overall conception rates differed (P ≥ 0.23) between cultivars. Performance of fall-calving cows pre-exposed to KY-31 was not improved when grazed on MaxQ in a SS system.

Seasonal Influence on Post Thaw Seminal Attributes and Conception Rate from Semen of Jaffarabadi Buffalo Bulls

Background: The quality of the frozen thawed semen is one of the most powerful factor affecting the conception rate in a buffaloes. The season may have its effect on post thaw seminal attributes and fertility. Therefore, current study was aimed to investigate the effect of winter and summer seasons on post thaw seminal attributes and conception rate from semen of Jaffarabadi buffalo bulls.Methods: The study was conducted on four Jaffarabadi breeding bulls, 5-6 years old, to know the post-thaw semen characteristics based on total of 192 semen ejaculates evaluated and cryopreserved over one year period. Result: The mean percentages of post-thaw motility, live sperm, abnormal sperm, HOST reactive sperm, acrosomal integrity and first AI conception rate for semen cryopreserved during winter were 58.85±0.56, 67.06±0.77, 8.62±0.43, 58.52±0.67, 75.22±0.27 and 45.75±0.21, respectively, whereas, corresponding values for semen cryopreserved during summer were 56.35±0.43, 65.62±0.76, 9.08±0.51, 55.43±0.60, 74.29±0.22 and 43.50±0.11. The semen quality of post thawed samples were observed better during winter compared to summer season for artificial insemination with satisfactory first AI conception rate.

11 Invivo-derived embryo pregnancy rates at Maddox Dairy from 2008 to 2018

11 Invivo-derived embryo pregnancy rates at Maddox Dairy from 2008 to 2018

10 Pregnancy rates following artificial insemination or embryo transfer in lactating Holstein cows

Excessive heat affects the fertility of high production lactating cows, and reduced pregnancy rates (PR) are observed during summer and early fall. Embryo production programs are used to produce more calves from high genetic merit animals, but could it also increase fertility by bypassing all the negative variables affecting the embryo development before Day 7 (oocyte development, ovulation, fertilization, early embryo development)? The data from AIs and embryo transfers (ET) between June 2017 and May 2019 were analysed. June, July, August, September, and October were called critical months (first-service AI conception rate dropped below 44%). The cows were located at Maddox Dairy in Riverdale, CA, USA, a Holstein herd that milks 3500 cows with a 305-day mature-equivalent milk production of 12 800 kg. First- and second-lactation cows were enrolled in a Presynch-Ovsynch oestrus-synchronization program and scheduled for the first AI at 86 days after calving or to receive an embryo 7 or 8 days after the expected heat. The embryos were produced invivo or invitro from Holstein donors and were transferred fresh or frozen. Blood was sampled on Day 30 after expected heat day (23 days after embryo transfer), and pregnancy was detected by the IDEXX PAG Bovine Pregnancy Test. Table 1 summarises the results, where ET PR% is the number of pregnant cows divided by the number of cows that received and embryo. All the cows synchronized for AI were bred, but only cows with the presence of a corpus luteum (CL) on ET day received an embryo. The presence of a CL was not detected in 28.7% (471/1642) of the cows (32.2% in the critical months and 25.7% in the others). Unfortunately, we could not detect the presence of a CL by ultrasonography every time we transferred embryos, so the nonovulation rate might be overestimated. The cows without a CL were considered open and used to calculate the adjusted PR (AdjPR%). Embryo transfer PR is superior to that of AI, especially during the critical months. Fresh invivo embryos have the most impact. When the cows without CLs are considered open, the difference between AI and ET is still evident for fresh invivo embryos. Besides producing animals with higher genetic merit, depending on the type of embryo used, ET can increase fertility in lactating Holstein cows, especially during the critical months. The other benefit of using ET is that cows that do not ovulate are synchronized right away, which is not the case for AI cows. Table 1.AI×embryo transfer in lactating Holstein cows1 from June 2017 to May 20192 Item Critical months (June to October) Other months (November to May) All year %PR n Adj PR% n %PR n Adj PR% n %PR n Adj PR% n Artificial insemination 41.2% 896 41.2% 896 47.7% 1767 47.7% 1767 45.5% 2663 2663 Fresh invivo embryo 62.7% 373 47.5% 493 69.5% 262 55.3% 329 65.5% 635 50.6% 822 Frozen invivo embryo 59.3% 221 44.8% 292 59.4% 256 47.3% 322 59.3% 477 46.1% 614 IVF fresh embryo 47.9% 167 36.2% 221 54.0% 363 43.0% 456 52.1% 530 40.8% 677 Total embryos 58.5% 761 44.2% 1006 60.2% 881 47.9% 1107 59.4% 1642 46.1% 2113 1Lactating Holstein cows, first and second lactation, first service, Presynch-Ovsynch, 85 DIM. 2PR%=the number of pregnant cows divided by the number of cows that received and embryo; AdjPR%=adjusted pregnancy rate.

216 Effects of low doses of GnRH at CIDR removal on estrus expression and conception rates in beef heifers

Abstract Previous studies evaluating single and multiple GnRH injections at time of CIDR removal have reported decreased interval to estrus and increased expression of estrus, and increased conception rates, respectively. Thus, the objective of this study was to compare the effects of supplementing GnRH at CIDR removal on expression of estrus and conception rates in beef heifers following the 7-d CO-Synch + CIDR protocol. Heifers (n = 1,482) from 11 herds over two years were synchronized using the 7-d CO-Synch + CIDR fixed time AI (FTAI) protocol and were randomly assigned to receive one of three treatments at CIDR removal [0 µg GnRH (0); 5 µg GnRH (5); or 5 µg at CIDR removal and 5 µg 12 h later (5 + 5)]. Expression of estrus and conception rates were analyzed using the GLIMMIX procedure of SAS with treatment as an independent variable and herd as a random effect. There was no effect of treatment on expression of estrus (P = 0.38), or AI conception rates (P = 0.85). There was an effect of estrus (P < 0.01) and a treatment × estrus interaction (P = 0.02). Animals that exhibited estrus prior to FTAI had increased (P < 0.01) conception rates compared with those that did not. Animals that exhibited estrus had increased (P < 0.01) conception rates compared with non-estrus animals in the 0 and 5 + 5 µg groups (54 ± 3% vs 34 ± 3%, and 52 ± 3% vs 36 ± 3%, respectively), but in the 5 µg group, there was no difference (P = 0.53) in conception rates between estrus and non-estrus animals (44 ± 3% vs 41 ± 3%, respectively). In conclusion, estrus expression increased pregnancy success, but supplementation with 5 or 5 + 5 µg of GnRH at CIDR removal did not improve estrus response or conception rates in beef heifers.

215 Influence of BVDV exposure on AI conception and breeding season pregnancy success in beef herds

Abstract Bovine Viral Diarrhea Virus (BVDV) causes reproductive and economic losses in cattle. The objective of this study was to evaluate the influence of BVDV exposure on reproductive success (AI and breeding season conceptions). Well vaccinated cows (n = 367) and heifers (n = 540) from 9 different herds were synchronized using the 7-d CO Synch + CIDR protocol and were fixed-time AI (FTAI). On d 28 following insemination, blood samples were collected, and pregnancy status was determined by transrectal ultrasonography and the IDEXX Rapid Visual Pregnancy Test. Non-pregnant animals were resynchronized and FTAI a second time. In six herds bulls were comingled with females beginning 10-15 d after the second AI. Final pregnancy status was determined 33–80 d following the first pregnancy diagnosis. Blood samples were tested for the presence of BVDV antigen using the IDEXX BVDV PI X2 Kit. Positive samples were indicative of animals with an active infection. Herds were determined as having BVDV exposure by the presence of at least one animal having a positive test for active antigen (n = 4 exposed herds, n = 5 non-exposed herds). Statistical analyses were performed using the GLIMMIX procedure of SAS. Herds that had BVDV exposure during the breeding season had significantly decreased (P < 0.01) first service AI conception rates compared to herds that had no exposure (34 ± 2.3% vs. 54 ± 2.3%). Additionally, breeding season pregnancy rates were decreased (P < 0.01) in herds that had BVDV exposure compared to non-exposed herds (69 ± 3.4% vs. 80 ± 3.6%). There was no significant effect of BVDV exposure on embryonic loss (P = 0.42) or percentage of animals which lost a pregnancy and rebred by the end of the breeding season (P = 0.63). In conclusion, BVDV exposure in well vaccinated herds still had a negative effect on both first service AI conception rate and overall breeding season pregnancy success.

Conception rate following intra-cervical artificial insemination using frozen semen at field level in indigenous sheep of Bangladesh

This study was undertaken to study the AI conception rate using frozen semen at field level. Five farms in Mymensingh, Bangladesh were selected for AI Trial in field ewes. Four rams were selected for semen collection, evaluation, and frozen semen production and further to study conception rate followed by intra-cervical AI in both natural and synchronized ewes. Conception rate were confirmed by non-returned rate and ultrasound scanning at 30-40 days of post insemination. The volume, colour, mass activity, sperm motility, viability, concentration, HOST +ve (%) and normal spermatozoa percentages were 0.8±0.3 ml, 3.9±0.3, 4.4±0.6, 81.3±5.0%, 90.0±4.0%, 3519.0±545.6x106/ml, 87.4±3.3% and 85.6±1.8%, respectively. The sperm concentration of ram R#6 was significantly higher (P<0.05) (4120.5±93.5x106/ml) compared with other rams. The mean motility and viability of pre-dilution, 120 minutes of addition of Part-A, 240 minutes of addition of Part-B and post-thaw were (83.8±4.8%, 81.3±2.5%, 80.0±4.1% and 41.3±9.5%) and (93.3±1.0%, 90.0±1.4%, 88.8±1.0% and 58.3±8.7%), respectively. There were no significant difference (P˃0.05) between pre-dilution and post-dilution sperm motility and viability percentage however, post-thaw sperm motility and viability significantly (P<0.05) decreased compare with the motility and viability of pre-dilution and post-dilution values. Motility and viability percentages of frozen semen did not decrease significantly (P> 0.05) with the increase of preservation time. The mean motility and viability at 24 hrs, day 7, day 15 and day 30 were 41.3±9.5%, 41.5±8.5%, 41.8±9.9% and 40.5±10.2%; and 59.0±10.1%, 58.5±7.7%, 59.0±8.8% and 57.8±8.3%, respectively. The conception rates in natural and synchronized estrous were 26.7% and 25%, respectively. There was no significant difference in conception rates between the natural and synchronized oestrous in field level. However, the present non-return rate and conception rate indicate the suitability of produced frozen semen application in the field level.Asian J. Med. Biol. Res. March 2018, 4(1): 55-62

Conception risk of beef cattle after fixed-time artificial insemination using either SexedUltra™ 4M sex-sorted semen or conventional semen

The objective of this study was to compare conception rates of female beef cattle inseminated at a fixed-time with either conventional (CON) or SexedUltra™ sex-sorted (SU) semen. Treatments included CON or SU with two sires represented within each treatment. Cows (n = 316) and heifers (n = 78) from six locations were randomly assigned treatment. Ovulation was synchronized in all females using the industry-standard 7-d CO-Synch + controlled internal drug release (CIDR) protocol (100 μg GnRH + CIDR [1.38 g progesterone] on d 0, 25 mg PGF2α at CIDR removal on d 7, and 100 μg GnRH on d 10, 54 h (heifers) or 60 h (cows) after CIDR removal). Estrotect™ estrous detection aids were applied at CIDR removal and patch activation was recorded at insemination. Animals were assumed estrual if greater than 50% of the patch coating was removed. The results from this study indicated no main effects of treatment (P = 0.82), sire (P = 0.64), or age (P=0.8) on AI conception rates. Additionally, there were not significant interactions between sire and treatment (P=0.19) or age and treatment (P=0.29). There was however, a significant (P=0.0005) effect of estrous expression on conception rates. Conception rate for estrual females (62.8%) was greater (p=0.0001) than non-estrual females (38.7%) at FTAI regardless of treatment. Furthermore, the conception rates were similar (P = 0.61) between conventional (61.9%) and sex-sorted semen (63.8%) when estrus was expressed prior to FTAI. Larger studies are warranted to determine appropriate timing of insemination with sex-sorted semen in FTAI protocols to maximize pregnancy potential.

Influence of vaccination with a combined chemically altered/inactivated BHV-1/BVD vaccine or a modified- live BHV-1/BVD vaccine on reproductive performance in beef cows and heifers

A field trial was conducted on 10 herds of previously- vaccinated cows and heifers (n=1,567) to evaluate the reproductive effects of prebreeding vaccination with either a modified-live virus (MLV) or a chemically altered/inactivated (CA/IV] BHV-1/BVDV vaccine. Animals received a single (cows) or 2 injections (heifers) of either vaccine, with the final injection between 27 and 89 days before breeding, which consisted of timed AI following a 7-d CO-Synch + CIDR synchronization. Conception rates to AI were greater in the CA/IV vaccine group compared to the MLV vaccine group (P=0.05; 60% vs 52%). Interval from vaccination with either vaccine until AI also influenced conception rates (P=0.02), with animals vaccinated 27 to 29 (52%) days or 30 to 37 (52%) days prebreeding exhibiting decreased conception rates compared to animals vaccinated 46 to 89 days prebreeding (P<0.03; 64%). There was no treatment by interval interaction (P=0.79), effect of treatment (P=0.18), or treatment by interval interaction (P=0.17) on breeding season pregnancy rates. In summary, vaccination of previously vaccinated beef cows and heifers with a MLV vaccine pre-breeding (27 to 89 d) was associated with decreased AI conception rates compared to a CA/IV vaccine.

Effects of supplementing methionine hydroxy analog on beef cow performance, milk production, reproduction, and preweaning calf performance.

Mature Simmental × Angus cows (214 cows; 635 ± 7 kg) were utilized to determine the effects of late gestation and early postpartum supplementation of methionine hydroxy analog (MHA) on cow BW, BCS, milk production, milk composition, reproduction, and calf performance until weaning in a fall-calving, cool-season grazing system. Cows were stratified by BW, age, AI sire, and assigned to 1 of 12 pastures (17 or 18 cows·pasture). Pastures were randomly allotted to 1 of 2 treatments: control (0.45 kg·cow·d of wheat midd-based pellets, = 6) or supplement including MHA (0.45 kg·cow·d of wheat midd-based pellets including 10 g MHA supplied as MFP (Novus International, Inc., St. Charles, MO; = 6). Treatments were fed 23 ± 7 d prepartum through 73 ± 7 d postpartum. Cow BW was collected at postcalving (27 ± 7 d postpartum), end of supplementation (73 ± 7 d postpartum), AI, pregnancy check, and end of trial (192 and 193 ± 7 d postpartum). At 73 ± 7 d postpartum, a subset of cow-calf pairs was used in a weigh-suckle-weigh procedure to determine milk production, and milk samples were taken to determine milk composition ( = 45·treatment). Serum from blood was collected at 73 ± 7 and 83 ± 7 d postpartum to determine cow cyclicity and concentrations of 2-hydroxy4-(methylthio) butanoic acid (HMTBa) and L-Methionine. After supplementation, all cow-calf pairs were managed as a common group until weaning (193 ± 7 d of age). Cows were bred via AI at 97 ± 7 d postpartum and clean-up bulls were turned out 11 d post-AI for a 55-d breeding season. Cows fed MHA had greater ( < 0.01) serum concentrations of HMTBa. Cow BW and BCS were not different ( ≥ 0.10) at any time points between treatments. There was no treatment effect ( ≥ 0.17) on calf birth BW, calf weaning BW (193 ± 7 d of age), or calf ADG. Calculated 24-h milk production, milk composition and component production did not differ ( ≥ 0.21). There were no differences ( ≥ 0.50) in percentage of cows cycling, AI conception rate, and overall pregnancy rate between treatments. Post-trial nutritional modeling suggests cows experienced several nutritional deficiencies beyond methionine (Met) that limited the response to Met supplementation. Although supplementation of MHA during late gestation through estimated peak lactation increased serum HMTBa concentrations, it did not affect cow performance, cow milk production, or calf performance when fall-calving cows grazed cool-season forages.

Comparison of timed insemination versus modified estrus detection protocol in beef heifers

Our objectives were to evaluate a fixed-time AI (FTAI) protocol versus a modified estrus detection with fixed-time AI (MTAI) protocol on estrus synchronization and pregnancy rates. Angus-based, crossbred heifers (n = 971; 346 ± 14 kg) were estrus synchronized via a melengestrol acetate-prostaglandin F2α (PG) protocol. An estrus detection aid (patch) was applied at PG injection. Each heifer was assigned a patch score (reflecting the amount of rub-off coating removed) at AI to reflect estrus status. At 72 h following PG, FTAI heifers received a 2-mL gonadotropin-releasing hormone injection and were inseminated. Estrus was detected in MTAI heifers at 58 and 70 h after PG. Approximately 72 h after PG, MTAI heifers were inseminated in the following order: heifers in estrus at 58 h after PG, heifers in estrus at 70 h after PG, and heifers not appearing in estrus at either observation. Heifers not expressing estrus received gonadotropin-releasing hormone at AI. Pregnancy was determined via transrectal ultrasonography 51 d after AI. In both treatments, heifers exhibiting estrus had greater (P < 0.01) AI conception rates than heifers not expressing estrus (71 and 66 ± 5% for FTAI vs. MTAI, respectively, vs. 47 and 53 ± 9% in nonestrus heifers for FTAI and MTAI, respectively). However, overall AI pregnancy rate (62 ± 5%) and final pregnancy rates were similar between treatments (P ≥ 0.49; 97 ± 3%). Similar AI pregnancy rates were achieved without the added labor of estrus detection.

Effects of dam prepartum supplement level on performance and reproduction of heifer progeny

Objectives were to determine the effect of dam prepartum supplement level on growth performance, feed efficiency and reproductive performance of female progeny (127 heifers in year 1, 138 heifers in year 2). Mature, multiparous, fall-calving, Angus × Simmental cows (initial age = 5.6 ± 1.9 years, BW = 623 ± 70 kg, BCS = 5.7 ± 0.7) were used in a completely randomised design that included three supplement levels: no supplement (NS), low supplement, 2.16 kg·cow−1·d−1 (LS), or high supplement, 8.61 kg·cow−1·d−1 (HS). Cows grazed endophyte-infected tall fescue/red clover pastures and were bunk-fed supplement (70% dried distiller’s grains plus solubles [DDGS] and 30% soybean hulls) 103 ± 11 d prepartum to 2 ± 11 d postpartum. Dam prepartum supplementation did not affect (p ≥ .60) heifer progeny BW at weaning, breeding, nor at pregnancy verification. Dam prepartum supplementation did not affect (p ≥ .18) heifer progeny AI conception rate, overall pregnancy rate, nor calving rate. Calving date, calf birth BW, percentage of unassisted births, milk production and calf BW at 73 ± 16 d of age were not different (p ≥ .24) among heifer progeny, regardless of dam supplement level. In conclusion, these data suggest within a fall-calving, fescue-based production system, supplementing dams with 2.16 or 8.61 kg·cow−1·d−1 of a DDGS-based supplement does not affect growth performance and reproductive performance of subsequent female progeny.

8 ANTI-MÜLLERIAN HORMONE AT WEANING AND BREEDING AS A PREDICTOR OF BEEF HEIFER FERTILITY

This study examined the relationship between serum anti-Müllerian hormone (AMH) concentration at weaning and breeding to determine if either or both measures could predict subsequent fertility of beef heifers. Blood was collected from 71 Angus based heifers at ~7 and 14 months of age and serum stored frozen (−20°C) until analysis for AMH, using bovine AMH ELISA kits (AL115; Ansh Laboratories, Webster, TX, USA). Before breeding, transrectal ultrasonography was used to determine cyclic status of heifers. Heifers received 25 mg of prostaglandin F2α (PGF) and those detected in oestrus were AI ~12 h after detected oestrus. Heifers not detected in oestrus after 7 days received a second PGF injection and oestrus detection and AI continued for 4 days. Ten days later, the heifers were exposed to fertile bulls for a 45-days breeding season. At 50 to 60 days after insemination, transrectal ultrasonography was used to identify pregnant heifers and to confirm conception date based on fetal size. At 60 days after bull removal, ultrasonography was performed to determine pregnancy in heifers conceiving during the breeding season and confirm continuing pregnancy in heifers previously identified as pregnant. Based on fetal size at ultrasonography, the oestrous cycle after initiation of breeding when conception occurred was estimated. For comparison, AI pregnancies were considered cycle 1, and pregnancies initiated during subsequent 21-day intervals of the breeding season were classified as cycles 2, 3, and 4, respectively. For analysis, frequency distribution was used to assign serum AMH concentration measured at weaning, breeding, and the change from weaning to breeding, into quartiles. Comparisons were then made via Chi-squared analysis for heifers in each quartile that were cyclic at synchronization, detected in oestrus, conceived after AI, pregnant at the end of the breeding season, and the estimated cycle that conception occurred. Comparison of heifers based on serum AMH quartiles at weaning failed (P ≥ 0.35) to detect any effect of AMH on subsequent heifer cyclicity at breeding, oestrous response after synchronization, AI conceptions, overall pregnancy rate, or estimated oestrous cycle of the breeding season when conception occurred. Based on AMH concentration at breeding, heifers in the lowest quartile (Q1) had a lower (10%; P = 0.02) AI conception rate than heifers in other quartiles (43 to 73%), and conceived at a later oestrous cycle (P = 0.03) in the breeding season. Comparison of heifers based on the change in AMH concentrations from weaning to breeding revealed that none of the heifers in the lowest quartile (Q1) conceived after AI, compared with 80% in the highest quartile (Q4; P &lt; 0.001). Heifers in the lowest quartile also conceived at a later oestrous cycle in the breeding season than heifers in the other quartiles (P = 0.01). Results indicate that either AMH concentration at breeding or the change in AMH from weaning to breeding can identify beef heifers more likely to conceive to AI and to conceive early in the breeding season.

Effect of supplementation on performance and reproduction of lactating beef cows grazing lush spring pasture

ABSTRACT Our objectives were to use 230 Angus × Simmental beef cows in a 2-yr experiment to determine the effects of supplementation on cow BW and BCS, first-service AI conception rate, and blood metabolites (nonesterified fatty acids, BHBA, and BUN). Cows (110 in yr 1 and 120 in yr 2) were randomly assigned to 1 of 2 treatments: control or supplement (SUPP). There were 3 replicates per treatment each year, and both treatments grazed clover–tall fescue pasture in early spring. The supplement contained 45% ground corncobs, 45% soybean hulls, and 10% dry molasses (DM basis), and 1.81 kg/cow per d was offered to cows fed SUPP starting 10 d before breeding. Forage samples were collected as groups were rotated to new pastures. Throughout the grazing season, forage CP decreased (P