Effects of temperament on reproductive performance of Bos taurus heifers enrolled in the 7-day CO-Synch + controlled internal drug release protocol.

Cattle temperament significantly impacts production traits such as reproduction. The objective of this study was to assess the effects of temperament on pregnancy rates to fixed-timed artificial insemination (TAI) in Bos taurus beef heifers. A total of 297 Angus influenced heifers from 3 different locations were evaluated for temperament based on chute score and exit velocity on the first day of the estrus synchronization protocol (d-9) and classified by temperament type based on temperament score (calm ≤ 3 < excitable). Pregnancy status was determined by transrectal ultrasonography approximately 40 d after TAI. Hair from the tail switch was collected at d-9 and at d0 (TAI) for cumulative cortisol evaluation. A subset of 43 heifers from location 3 had blood samples collected at all handling events and evaluated for cortisol concentrations. Overall, 71% of heifers were classified as calm whereas 29% as excitable. Pregnancy rates to TAI were reduced (P = 0.042) in excitable heifers compared to calm heifers (36% vs. 55%, respectively). Mean concentration of cortisol in the hair was reduced over time (P < 0.001) from d-9 (3.5 ± 0.3 pg/mg) to d0 (1.74 ± 0.3 pg/mg) in all heifers, regardless of temperament. In addition, excitable heifers had increased circulating concentrations of cortisol when compared to calm heifers in all handling events (P = 0.015). More interestingly, despite of temperament, concentrations of circulating cortisol were reduced as the protocol events progressed, with greater cortisol concentrations on d-9, intermediate on d-3, and lesser on d0 (P = 0.031). Therefore, the present study demonstrates that heifer temperament has negative effects in pregnancy rates to TAI programs. However, according to blood cortisol concentrations, no chronic stress response was detected due to cattle handling for the TAI protocol. In fact, blood cortisol concentration was reduced between the initiation and completion of the protocol, indicating that heifers were acclimated to handing. These results support the adoption of acclimation protocols and proper cattle handling as a strategy to increase fertility of heifers that are exposed to TAI.

A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols.

This retrospective study aimed to determine if the number of cows exposed per bull affects pregnancy rates of cows returning to estrus after fixed-time artificial insemination (FTAI). Data were compiled over the course of 13 breeding seasons (six fall and seven spring seasons) between 2010 and 2017 from the Virginia Department of Corrections herd. Available records contained data from 17 farms and 324 groups of cows (average 47 cows/group). Multiparous cows and heifers (average age per group: 5.11 ± 0.14 yr; n = 14,868) were exposed to FTAI. After FTAI, animals were placed on pasture with bulls diagnosed as fertile by a breeding soundness exam for natural service of cows who did not become pregnant to FTAI (n = 7,248; average 22 cows/group). Animals were classified as pregnant to FTAI, to natural service on first return to estrus, or to natural service on second or subsequent estrus determined by fetal aging at pregnancy diagnosis. The bull:cow ratio for the total number of cows exposed ranged from 1:9 to 1:73 with an average of 1:31. The bull:cow ratio considering only open cows exposed after FTAI ranged from 1:2 to 1:44 with an average of 1:14. There was significant negative, small correlation between the bull:cow ratio for total number of cows exposed and return to estrus pregnancy rate in fall breeding seasons (P = 0.01, r 2 = 0.04) but not in spring (P = 0.90). There was a significant negative, small correlation between bull:cow ratio of open cows exposed and pregnancy rates to first return to estrus in fall herds with a single sire (P < 0.001, r 2 = 0.11). There was no correlation in fall herds using multiple sires or spring herds (P ≥ 0.12). Bull:cow ratio accounted for only 1-11% of variation in the pregnancy rates, thus we conclude that a decreased bull:cow ratio (up to 1:73) did not affect natural service return to estrus pregnancy rate. Cattlemen may consider a reduced number of bulls needed for natural service breeding after FTAI, which can decrease bull related costs and increase the economic feasibility of adopting FTAI protocols.

Administration of recombinant bovine somatotropin prior to fixed-time artificial insemination and the effects on fertility, embryo, and fetal size in beef heifers.

Our objectives were to determine the effects of the administration of recombinant bovine somatotropin (bST) at the initiation of a fixed-time AI (TAI) protocol on concentrations of plasma IGF-1, follicle diameter, embryo/fetal size, and pregnancy rates in replacement beef heifers. Four hundred and fourteen Angus-based beef heifers were enrolled in a completely randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) protocol where they received a 100-µg injection of GnRH and a CIDR insert on day -9, 25 mg of PGF2α at CIDR removal on day -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on day 0. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) heifers that received 650 mg of bST on day -9 (BST; n = 191); or 2) heifers that did not receive bST on day -9 (CONTROL; n = 223). Blood samples were collected on day -9, 0, 28, and 60 to determine the plasma concentrations of IGF-1. Follicle diameter was determined on day -2 and 0 by transrectal ultrasonography. Pregnancy was diagnosed via transrectal ultrasonography on day 28 or 35, and again at least 30 d after the end of the breeding season. Embryo morphometry was assessed by measuring crown-to-rump length (CRL) on day 28, and fetal size was assessed by measuring crown-to-nose-length (CNL) on day 60. Concentrations of plasma IGF-1 did not differ between treatments on day -9 (P = 0.924), 28 (P = 0.075), and 60 (P = 0.792); however, concentrations of plasma IGF-1 were greater (P < 0.001) in BST-treated heifers at TAI (372.4 ± 16.6 vs. 193.7 ± 16.6 ng/ml). No differences (P = 0.191) were detected for follicle diameter between CONTROL and BST treatments on day -2 or 0. Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) for CONTROL compared to BST heifers (42.5 ± 4.0 vs. 29.9 ± 4.1%). No differences (P = 0.536) in CRL were observed on day 28 between CONTROL and BST heifers. In addition, no difference (P = 0.890) was observed for CNL between CONTROL and BST treatments. Final pregnancy rates did not differ (P = 0.699) between treatments. The administration of bST to beef heifers at the initiation of a TAI protocol increased plasma concentrations of IGF-1 at TAI; however, failed to enhance follicle diameter, embryo/fetal size, and reduced PR/AI.

Supplementing Ca salts of soybean oil after artificial insemination increases pregnancy success in Bos taurus beef cows.

Two experiments investigated the effects of supplementing Ca salts of soybean oil (CSSO) during early gestation on reproductive function and pregnancy rates to AI in Bos taurus beef cows. In Exp. 1, 771 suckled, lactating, multiparous Angus cows were divided into 22 groups of approximately 35 cows per group and timed inseminated on day 0. After AI, groups were assigned randomly to receive (as-fed basis) 100 g of ground corn + 100 g of soybean meal per cow/d, in addition to 1) 100 g/cow daily of CSSO (n = 11) or 2) 87 g of prilled saturated fat + 13 g of limestone per cow/d (CON; n = 11). Groups were maintained in individual tall fescue-dominated pastures and offered treatments from day 0 to 21. Pregnancy status was determined between days 45 and 55 via transrectal ultrasonography. Cows receiving CSSO had greater (P = 0.01) pregnancy rates to timed AI compared with CON (60.2 vs. 51.7%; SEM = 4.2). In Exp. 2, 90 suckled, lactating, multiparous Angus × Hereford cows housed in 18 drylot pens (5 cows per pen) were assigned to the same timed AI program and treatments from Exp. 1 (9 pens per treatment) and received 20 kg/d (DM basis) of grass-alfalfa hay. Transrectal ultrasonography was performed to verify ovulation and corpus luteum (CL) volume before AI (day 0), on days 7 and 15. After ultrasonography on day 15, cows diagnosed without a CL on day 0, but with a CL greater than 0.38 cm3 in volume on days 7 and 15 (2 or 3 cows per pen; CSSO, n = 20; CON, n = 24), were assigned to conceptus collection via transcervical flushing and endometrial biopsy in the uterine horn ipsilateral to the CL. Blood samples were collected for FA analysis on days 0, 7, and 15. Blood was collected from cows not assigned to conceptus collection for whole-blood RNA extraction on day 20 and for pregnancy diagnosis on day 30 by measuring concentrations of pregnancy-associated glycoproteins. Cows receiving CSSO had greater (P ≤ 0.04) mean plasma concentrations of linoleic acid and ω-6 FA compared with CON on days 7 and 15. Moreover, CSSO supplementation increased (P = 0.05) mRNA expression of interferon-tau by the conceptus and blood mRNA expression of interferon-stimulated gene 15 and 20,50-oligoadenylate synthetase on day 20 in gestating cows. Hence, post-AI CSSO supplementation to B. taurus beef cows improved pregnancy rates to timed AI, which can be associated with increased mRNA expression of interferon-tau by the conceptus when CSSO is supplemented during early gestation.

Fertility in Angus cross beef cows following 5-day CO-Synch + CIDR or 7-day CO-Synch + CIDR estrus synchronization and timed artificial insemination.

The present study determined whether a 5-day CO-Synch + controlled internal drug release (CIDR) protocol with two doses of PGF2α would improve timed artificial insemination (AI) pregnancy rate compared with 7-day CO-Synch + CIDR protocol in beef cows. Angus cross beef cows (N = 1817) at 12 locations were randomly assigned to 5-day CO-Synch + CIDR or 7-day CO-Synch + CIDR groups. All cows received 100 µg of GnRH and a CIDR insert on Day 0. Cows (n = 911) in the 5-day CO-Synch + CIDR group received two doses of 25 mg PGF, the first dose given on Day 5 at CIDR removal and the second dose 6 hours later, and 100 µg GnRH on Day 8 and were inseminated concurrently, 72 hours after CIDR removal. Cows (n = 906) in 7-day CO-Synch + CIDR group received 25 mg of PGF at CIDR removal on Day 7, and 100 µg GnRH on Day 10 and were inseminated concurrently, 66 to 72 hours after CIDR removal. All cows were fitted with a heat detector aid at CIDR removal and were observed twice daily until insemination for estrus and heat detector aid status. Accounting for estrus expression at or before AI (P < 0.0001) and body condition score (P < 0.01), cows in the 5-day CO-Synch + CIDR group had greater AI pregnancy rate compared with cows in the 7-day CO-Synch + CIDR group (58.1% vs. 55.1%; P = 0.04). More cows that exhibited estrus at or before AI became pregnant compared with cows that did not [65.7% (681/1037) vs. 44.5% (347/780); P < 0.0001]. The AI pregnancy rate was lesser for cows with body condition ≤4 [≤4 - 49.3% (101/219), 5-6 - 57.9%; >6 - 55.8%]. The mean AI pregnancy rate difference between treatment groups and projected economic outcome varied among locations. In conclusion, cows synchronized with the 5-day CO-Synch + CIDR protocol had greater AI pregnancy rate than those that received the 7-day CO-Synch + CIDR protocol.

Phalaris arundinacea (reed canarygrass) grass staggers in beef cattle.

Four adult mixed-breed beef cows from a cow-calf operation in West Virginia were referred to the Virginia-Maryland Regional College of Veterinary Medicine in March 2009 with weakness, ataxia, hind limb paresis progressing to lateral recumbency, and death within 2-3 days. Histologically, there was accumulation of light brown, granular pigment in neurons of the ventral gray horns of the spinal cord (more severe in thoracic and lumbar sections), brain stem, and pons, resulting in distortion and bulging of the cell body and displacement of the Nissl substance, suggestive of Phalaris sp. grass toxicosis. The most severely affected cow had accumulation of dark green-brown pigment in renal tubular epithelial cells. Reed canarygrass (Phalaris arundinacea) was identified in pastures, and the concentration of tryptamine alkaloids in new leaf blades was approximately 0.2% on a wet weight basis. These alkaloids are serotonergic receptor agonists, resulting in neurologic "staggers" in ruminants. Delayed onset times of up to 4-5 months have been reported in sheep after removal from Phalaris sp. pastures. Distribution of pigment in serotonergic tracts of the midbrain, brain stem, and spinal cord with Phalaris sp. toxicoses is distinct and differs from lipofuscin. Electron microscopy confirmed that the pigment was not lipofuscin. From these findings, a diagnosis of delayed P. arundinacea toxicosis was made. Over a 2-month period, 18 cows died with similar clinical signs.

A field study of the effects of a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine administered with oxytetracycline on reproductive performance in beef cattle.

OBJECTIVE: To determine whether vaccination with a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine coupled with parenteral long-acting oxytetracycline treatment would improve the reproductive performance of beef cows. DESIGN: Randomized controlled field trial. ANIMALS: 1,446 Angus-cross beef cows in 8 locations. PROCEDURES: Cows were given 2 doses, 4 weeks apart, of vaccine (treatment; n=741) or placebo (control; 705). Cows in the treatment group were also given a single dose of a long-acting oxytetracycline formulation (20 mg/kg [9.1 mg/lb], SC) at the time of booster vaccination. Estrus synchronization was performed, followed by fixed-time artificial insemination; bulls were introduced 14 days after insemination. Serum and urine samples were obtained on a random subset of cows (n=194) for detection of serologic titers and leptospiruria, and locations were categorized as positive or negative for leptospirosis on the basis of detection of leptospiruric cows. RESULTS: No differences in pregnancy and calving rates between treatment and control groups were detected. Pregnancy rate following artificial insemination was lower among cows in locations positive for leptospirosis than among cows in locations negative for leptospirosis; however, overall pregnancy rate, calving rate following artificial insemination, and overall calving rate did not differ between groups when cows were grouped on the basis of location leptospirosis status. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that under the conditions of the present study, administration of a monovalent Leptospira vaccine in conjunction with systemic administration of oxytetracycline did not significantly improve reproductive performance of beef cows.