Reproductive performance of prepubertal Bos indicus heifers after progesterone-based treatments

The objective was to evaluate the effects of exogenous progesterone (P4) on reproductive performance of prepubertal Bos indicus heifers. Prepubertal Nelore heifers (n = 589; 24.0 +/- 1.13 mo; 298.0 +/- 1.89 kg; body condition score of 3.2 +/- 0.26; mean +/- SEM) were randomly assigned to receive, between experimental Days -12 and 0: no treatments (CIDR0; n = 113); a new intravaginal insert (CIDR) containing 1.9 g of P4 (CIDR1; n = 237); or a similar insert previously used three times, with each use occurring for 9 d (CIDR4; n = 239). An additional treatment group was pubertal heifers given 12.5 mg dinoprost tromethamine im on Day 0 (PGF; n = 346), and used as controls for evaluation of conception rates. on Day 0, transrectal palpation was done for uterine score evaluation (UtS; 1-3 scale), blood samples were taken for serum P4 concentrations, and follicle diameter (FD) was measured. The breeding season started on Day 1 and consisted of AI after detection of estrus between Days I and 45, and exposure to bulls between Days 46 and 90. There were effects of treatment (P < 0.05) on serum concentrations of P4 on Day 0 (0.37 +/- 0.16, 2.31 +/- 0.11, and 1.20 +/- 0.11 ng/mL for CIDR0, CIDR1, and CIDR4, respectively; mean SEM), FD on Day 0(9.45 +/- 0.24, 9.72 +/- 0.17, and 11.42 +/- 0.16 mm), UtS on Day 0 (1.49 +/- 0.06, 1.88 +/- 0.04, and 2.24 +/- 0.04), estrus detection rates at 7 d (19.5, 42.6, and 38.3%) and 45 d (52.2, 72.1, and 75.3%) of the breeding season, and on pregnancy rates at 7 d (5.3, 14.3, and 18.4%), 45 d (27.4, 39.2, and 47.7%) and 90 d (72.6, 83.5, and 83.7%) of the breeding season. Conception rate 7 d after the start of the breeding season was greater (P < 0.05) in heifers from the CIDR4 (46.8%) and PGF (43.8%) groups than in the CIDR0 (27.3%) and CIDR1 (33.7%) groups. In conclusion, exogenous P4 hastened puberty and improved pregnancy rates at the beginning of the breeding season in prepubertal Bos indicus heifers. Furthermore, previously used CIDR inserts were better than new inserts. (C) 2010 Elsevier B.V. All rights reserved.

Follicle deviation and ovulatory capacity in Bos indicus heifers

The objectives of Experiment I were to determine the interval from ovulation to deviation, and diameter of the dominant follicle (DF) and largest subordinate follicle (SF) at deviation in Nelore (Bos indicus) heifers by two methods (observed and calculated). Heifers (n = 12) were examined ultrasonographically every 12 h from ovulation (Day 0) to Day 5. The time of deviation and diameter of the DF and largest SF at deviation did not differ (P > 0.05) between observed and calculated methods. Overall, deviation occurred 2.5 +/- 0.2 d (mean +/- S.E.M.) after ovulation, and diameters for DF and largest SF at deviation were 6.2 +/- 0.2 and 5.9 +/- 0.2 mm, respectively. Experiment 2 was designed to determine the size at which the DF acquires ovulatory capacity in B. indicus heifers. Twenty-nine heifers were monitored every 24 h by ultrasonography, from ovulation until the DF reached diameters of 7.0-8.4 mm (n = 9), 8.5-10.0 mm (n = 10), or >10.0 mm (n = 10). At that time, heifers were treated with 25 mg of pLH and monitored by ultrasonography every 12 h for 48 h. Ovulation occurred in 3 of 9, 8 of 10, and 9 of 10 heifers, respectively (P < 0.05). In summary, there was no significant difference between observed and calculated methods of determining the beginning of follicle deviation. Deviation occurred 2.5 d after ovulation when the DF reached 6.2 mm, and ovulatory capacity was acquired by DF as small as 7.0 mm. (c) 2008 Elsevier B.V. All rights reserved.

Morphological characterization of follicle deviation in Nelore (Bos indicus) heifers and cows

Follicle diameter deviation is defined as the beginning of the differential change in growth rates between the largest and next largest follicles subsequent to wave emergence and is considered a key component of follicle selection. Follicle selection has been extensively studied in European breeds of cattle (Bos taurus) but has not been critically studied in Zebu breeds (Bos indicus). The objectives of the present study were to determine and compare the morphological characteristics of deviation associated with the first post-ovulatory wave (Wave 1) of the estrous cycle in Nelore heifers (n = 8) and nonlactating cows (n = 11). Beginning on the day of ovulation (day 0), the three largest follicles (F1-F3, respectively) were individually tracked every 12 h for 6 d using transrectal ultrasonography. In individual animals, deviation was determined graphically using visual inspection of the diameter profiles of F1, F2 and sometimes F3 (observed deviation) and mathematically using segmented regression analysis of the diameter differences between F1 and F2 or sometimes F3 (calculated deviation). Mean day of emergence of Wave 1 when F1 reached >3 rum (approximately 1 d after ovulation) and growth rate of F1 during deviation (approximately 1.4 mm/d) were not significantly different between heifers and cows. The results of determining the beginning of deviation within heifers and cows using the observed and calculated methods were not significantly different. Averaged over both methods, diameter deviation occurred 2.8 d after ovulation when F1 reached 5.7 mm in heifers, and 2.4 d after ovulation when F1 reached 6.1 mm in cows. In conclusion, the emergence of Wave 1 and growth rates and diameters of the future dominant follicles at the beginning of deviation were similar in Nelore heifers and nonlactating cows, regardless of the methods used to determine deviation. Relative to Holstein cattle, emergence of Wave 1 appeared to occur about 1 d later and diameter of the future dominant follicle at the beginning of deviation was about 2 turn smaller in Nelore. (C) 2004 Elsevier B.V. All rights reserved.

Effects of dominant follicle aspiration and treatment with recombinant bovine somatotropin (BST) on ovarian follicular development in Nelore (Bos indicus) heifers

Follicle ablation has been recognized as an efficient method of follicular wave synchronization. Treatment with recombinant bovine somatotropin (BST) has been shown to enhance follicular development in <(Bos taurus)under bar>. This experiment assessed the effects of these treatments in Nelore (<(B. indicus)under bar>) heifers. Eight cycling Nelore heifers were randomly assigned to 3 different treatments. on Day 2 of a synchronized cycle (Day 0 = day of ovulation), heifers assigned to Treatments 1 and 2 received 2 mL of saline, whereas heifers assigned to Treatment 3 received 320 mg of BST. on Day 5, the first-wave dominant follicle was ablated by ultrasoundguided transvaginal aspiration in heifers in Treatments 2 and 3, and all heifers received an injection of prostaglandin on Day 11. Aspiration of the dominant follicle advanced and synchronized (P < 0.05) the day of second-wave emergence (6.9 +/- 0.1 vs. 8.4 +/- 0.4) and the day of the pre-wave FSH peak (6.0 +/- 0.0 vs. 6.9 +/- 0.4), and increased FSH peak concentrations (381 +/- 21 vs. 292 +/- 30; pg/mL; P < 0.01). Recombinant bovine somatotropin treatment caused a two-fold increase in plasma insulin-like growth factor-I (IGF-I) concentrations (P < 0.001) and resulted in a 36% increase in the number of small follicles (<5 mm; P < 0.001) compared with saline-treated heifers. In summary, in agreement with previous reports on <(B. taurus)under bar>, dominant follicle aspiration synchronized ovarian follicular development, and BST treatment increased peripheral concentrations of IGF-I in Nelore heifers. Recombinant bovine somatotropin also increased the number of small follicles, but this response appeared to be inferior to that reported for <(B. taurus)under bar>. (C) 2000 by Elsevier B.V.

Ovariectomy by left flank approach in prepubertal Nelore (Bos indicus) heifers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Follicular dynamics and plasma FSH and progesterone concentrations during follicular deviation in the first post-ovulatory wave in Nelore (Bos indicus) heifers

The objective of the present study was to characterize ovarian follicular dynamics and hormone concentrations during follicular deviation in the first wave after ovulation in Nelore (Bos indicus) heifers. Ultrasonographic exams were performed and blood samples were collected every 12 h from the day of estrus until 120-144 h after ovulation in seven females. Deviation was defined as the point at which the growth rate of the dominant follicle became greater than the growth rate of the largest subordinate follicle. Deviation occurred approximately 65 h after ovulation. Growth rate of the dominant follicle increased (P < 0.05) after deviation, while growth rate of the subordinate follicle decreased (P < 0.05). Diameter of the dominant follicle did not differ from the subordinate follicle at deviation (approximately 5.4 mm). The dominant follicle (7.6 mm) was larger (P < 0.05) than the subordinate follicle (5.3 mm) 96 h after ovulation or 24 h after deviation. Plasma FSH concentrations did not change significantly during the post-ovulatory period. The first significant increase in mean plasma progesterone concentration occurred on the day of follicular deviation. In conclusion, the interval from ovulation to follicular deviation (2.7 days) was similar to that previously reported in B. taurus females, but follicles were smaller. Diameters of the dominant follicle and subordinate follicle did not differ before deviation and deviation was characterized by an increase in dominant follicle and decrease in subordinate follicle growth rate. Variations in FSH concentrations within 12-h intervals were not involved in follicular deviation in Nelore heifers. © 2006 Elsevier B.V. All rights reserved.

Prostaglandin treatment at the onset of norgestomet and estradiol-based synchronization protocols did not alter the ovarian follicular dynamics or pregnancy per timed artificial insemination in cyclic Bos indicus heifers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Strategies to improve fertility in Bos indicus postpubertal heifers and nonlactating cows submitted to fixed-time artificial insemination

Two experiments were designed to evaluate strategies to increase fertility of Bos indicus postpubertal heifers and nonlactating cows submitted to a fixed-time artificial insemination (TAI) protocol consisting of an intravaginal device containing 1.9 g of progesterone (CIDR) insertion + estradiol benzoate on Day 0, CIDR withdrawal + estradiol cypionate on Day 9, and TAI on Day 11. In Experiment 1, heifers (n = 1153) received a new or an 18-d previously used CIDR and, on Day 9, prostaglandin F(2 alpha) (PGF(2 alpha)) + 0, 200, or 300 IU equine chorionic gonadotropin (eCG). Heifers treated with a new CIDR had greater (least squares means +/- SEM) serum concentration of progesterone on Day 9 (3.06 +/- 0.09 ng/mL vs. 2.53 +/- 0.09 ng/mL; P < 0.05) and a smaller follicle at TAI (11.61 +/- 0.11 nim vs. 12.05 +/- 0.12 mm; P < 0.05). Heifers with smaller follicles at TAI had lesser serum progesterone, concentrations on Day 18 and reduced rates of ovulation, conception, and pregnancy (P < 0.05). Treatment with eCG improved (P < 0.05) follicle diameter at TAI (11.50 +/- 0.10 mm, 11.90 +/- 0.11 mm, and 12.00 +/- 0.10 mm, for 0, 100, and 200 IU, respectively), serum progesterone concentration on Day 18 (2.77 +/- 0.11 ng/mL, 3.81 +/- 0.11 ng/mL, and 4.87 +/- 0.11 ng/mL), and rates of ovulation (83.8%, 88.5%, and 94.3%) and pregnancy (41.3%, 47.0%, and 46.7%). In Experiment 2, nonlactating Nelore cows (n = 702) received PGF(2 alpha) treatment on Days 7 or 9 and, on Day 9, 0 or 300 IU cCG. Cows receiving PGF(2 alpha) on Day 7 had lesser serum progesterone concentrations on Day 9 (3.05 +/- 0.21 ng/mL vs. 4.58 +/- 0.21 ng/mL; P < 0.05), a larger follicle at TAI (11.54 +/- 0.21 mm vs. 10.84 +/- 0.21 mm; P < 0.05), and improved (P < 0.05) rates of ovulation (85.4% vs. 77.0%), conception (60.9% vs. 47.2%), and pregnancy (52.0% vs. 36.4%). Treatment with eCG improved (P < 0.05) serum progesterone concentration on Day 18 (3.24 +/- 0.14 ng/mL vs. 4.55 +/- 0.14 ng/mL) and the rates of ovulation (72.4% vs. 90.0%) and pregnancy (37.5% vs. 50.8%). In conclusion, giving PGF(2 alpha) earlier in the protocol in nonlactating cows and eCG treatment in postpubertal heifers and nonlactating cows improved fertility in response to a TAI (progesterone + estradiol) protocol. (C) 2009 Elsevier B.V. All rights reserved.

Different true-protein sources do not modify the metabolism of crossbred Bos taurus x Bos indicus growing heifers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessment of DGAT1 and LEP gene polymorphisms in three Nelore (Bos indicus) lines selected for growth and their relationship with growth and carcass traits

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Incidence and transplacental transmission of Neospora caninum in primiparous females from Bos indicus slaughtered in Presidente Pradente, São Paulo, Brazil

To produce an epidemiological map of neosporosis in Brazil and identify the types of transmission of this disease, the present study evaluated the occurrence of Neospora caninum in Nelore cattle (Bos indicus) in Presidente Prudent, west region of São Paulo state; its vertical transmission; and the early stage in which fetuses are infected. To achieve this, serum samples from 518 slaughtered pregnant heifers and their fetuses were tested by ELISA technique and fetal brain tissues subjected to PCR. One hundred and three heifers (19.88%) had antibodies to N. caninum, as well as 38 (36.8%) of fetuses from 4 months of gestation. The conventional PCR failed to detect N. caninum DNA. These findings show that neosporosis occurs in the area studied and that it may be transmitted the transplacental route, althought N. caninum had not detected in brain tissue from non-aborted fetuses. The use of nested PCR it would be applied to increase the sensitivy of test.