Equine chorionic gonadotropin and gonadotropin-releasing hormone enhance fertility in a norgestomet-based, timed artificial insemination protocol in suckled Nelore (Bos indicus) cows

Two experiments were conducted to investigate the effects of equine chorionic gonadotropin (eCG) at progestin removal and gonadotropin-releasing hormone (GnRH) at timed artificial insemination (TA!) on ovarian follicular dynamics (Experiment 1) and pregnancy rates (Experiment 2) in suckled Nelore (Bos indicus) cows. Both experiments were 2 x 2 factorials (eCG or No eCG, and GnRH or No GnRH), with identical treatments. In Experiment 1, 50 anestrous cows, 134.5 +/- 2.3 d postpartum, received a 3 mg norgestomet ear implant se, plus 3 mg norgestomet and 5 mg estradiol valerate im on Day 0. The implant was removed on Day 9, with TAI 54 h later. Cows received 400 IU eCG or no further treatment on Day 9 and GnRH (100 mu g gonadorelin) or no further treatment at TAI. Treatment with eCG increased the growth rate of the largest follicle from Days 9 to 11 (means +/- SEM, 1.53 +/- 0.1 vs. 0.48 +/- 0.1 mm/d; P < 0.0001), its diameter on Day 11(11.4 +/- 0.6 vs. 9.3 +/- 0.7 mm; P = 0.03), as well as ovulation rate (80.8% vs. 50.0%, P = 0.02), whereas GnRH improved the synchrony of ovulation (72.0 +/- 1.1 VS. 71.1 +/- 2.0 h). In Experiment 2 (n = 599 cows, 40 to 120 d postpartum), pregnancy rates differed (P = 0.004) among groups (27.6%, 40.1%, 47.7%, and 55.7% for Control. GnRH, eCG, and eCG + GnRH groups). Both eCG and GnRH improved pregnancy rates (51.7% vs. 318%, P = 0.002; and 48.0% vs 37.6%, P = 0.02, respectively), although their effects were not additive (no significant interaction). In conclusion, eCG at norgestomet implant removal increased the growth rate of the largest follicle (LF) from implant removal to TAI, the diameter of the LF at TAI, and rates of ovulation and pregnancy rates. Furthermore, GnRH at TAI improved the synchrony of ovulations and pregnancy rates in postpartum Nelore cows treated with a norgestomet-based TAI protocol. (C) 2010 Elsevier Inc. All rights reserved.

Validation of body condition score as a predictor of subcutaneous fat in Nelore (Bos indicus) cows

The aim of the present study was to determine the relationship among body weight (BW), body condition score (BCS) and rump fat thickness (RFAT) measured by ultrasonography, and validate the relationship between BCS and RFAT over the time. Two hundred sixty and six Nelore cows had their BW, BCS and RFAT evaluated at five different moments during the production cycle: M1) weaning: M2) parturition, M3) 42 days post-partum; M4) 82 days postpartum and M5) 112 days post-partum. A BCS value was attributed for each cow following a I to 5 points scale. Ultrasonographic images for RFAT measurement were obtained using a 3.5 MHz linear transducer. Images were immediately analyzed as soon as they were formed and frozen. Body condition scores and ultrasound measurements were collected on the same day by a single trained technician. The relationship between BCS and RFAT values was investigated by regression models. The analysis of similarity among the five obtained models was performed using the proc MIXED from SAS and the correlations among variables were analyzed with proc CORR from SAS. The BCS was able to predict RFAT in Nelore cows in all different moments evaluated. Also, it was shown that BCS presented high correlation (r=0.82 to 0.93) and relationship (R(2) = 0.73 to 0.92) with RFAT. However, both BCS and RFAT showed low correlation (r=0.37 to 0.50) and relationship (R(2) = 0.13 to 0.25) with BW. The BCS classification by visual method using a 1 to 5 point scale, was able to predict the RFAT in Nelore cows over the time. (C) 2008 Elsevier B.V. All rights reserved.

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

The aim of this study was to analyze LEP and DGAT1 gene polymorphisms in 3 Nelore lines selected for growth and to evaluate their effects on growth and carcass traits. Traits analyzed were birth, weaning, and yearling weight, rump height, LM area, backfat thickness, and rump fat thickness obtained by ultrasound. Two SNP in the LEP gene [LEP 1620(A/G) and LEP 305(T/C)] and the K232A mutation in the DGAT1 gene were analyzed. The sample consisted of 357 Nelore heifers from 2 lines selected for yearling weight and a control line, established in 1980, at the Estacao Experimental de Zootecnia de Sertaozinho (Sertaozinho, Brazil). Three genotypes were obtained for each marker. Differences in allele frequencies among the 3 lines were only observed for the DGAT1 K232A polymorphism, with the frequency of the A allele being greater in the control line than in the selected lines. The DGAT1 K232A mutation was associated only with rump height, whereas LEP 1620(A/G) was associated with weaning weight and LEP 305(T/C) with birth weight and backfat thickness. However, more studies, with larger data sets, are necessary before these makers can be used for marker-assisted selection.

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)

Constituintes sangüíneos de bovinos recém-nascidos das raças Nelore (Bos indicus) e Holandesa (Bos taurus) e de bubalinos (Bubalus bubalis) da raça Murrah

Newborn Holstein-Friesian and Nelore cattle and Murrah buffalo blood samples were collected for hemograma and serum constituents testing. Results indicated that: 1. buffalo red blood cell (RBC) counts were lower than RBC counts for cattle during the first 30 days after birth; 2. buffalo leukocytes, neutrophil and lymphocyte counts increased in older animals; 3. The highest fibrinogen levels occurred in older calves; 4. buffalo glucose levels were lower than Nelore cattle and decreased in the older calves; 5. buffalo iron, urea, and aspartate aminotransferase levels were higher than in cattle with the highest concentration at the time of birth; 6. cattle bilirubin and alanine aminotranferase levels were higher than buffalo with the highest value at the time of birth; 7. alkaline phosphatase and gammaglutamyltransferase activities were lower in the older calves; 8. buffalo magnesium levels were higher than cattle with lower concentrations at the time of birth..

Constituintes sangüíneos de vacas das raças Nelore (Bos indicus) e Holandesa (Bos taurus) e de bubalinas (Bubalus bubalis) da raça Murrah durante a gestação, no dia do parto e no puerpério

Blood constituents of Nelore, Hosltein and buffalo cows were determined during pregnancy, at the time of calving and at post-partum. It was verified that. 1. The pregnancy and post-partum periods had no influence in the erythrocyte values, but at calving the red blood cell counts and hemoglobin levels of Holstein and buffalo cows were lower than for Nelore cattle; 2. leukocyte counts were similar among groups; 3. total protein levels of Nelore cows were lower than Holstein and buffalo. The albumin levels were rite lowest at rite time of calving compared to late pregnancy; 4. glicose levels were lower ill buffalo cows during pregnancy as compared with Holstein cows. The glicemia of Nelore cows was lower as compared to Holstein cow's irt late pregnancy; 5. urea and creatinine levels were higher in buffalo cows than cattle. The urea and creatinine levels were greater in buffalo cows with maximum values at the post-partum and at the parturition, respectively; 6. bilirrubin levels were higher in bovine than buffalo cows; 7. aspartate aminotransferase activity was greater in buffalo cows and increased at the time of calving; 8. alkaline phosphatase activity was increased during pregnancy and decreased after the time of calving; 9. gammnglutamyltransferase activity,vas the highest for buffalo cows after calving; IO. calcium levels were the highest for Holstein cows at the post-partum and the phosphorus levels were higher in buffalo cows, which had the highest magnesium levels at the parturation.

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.

Constituintes sangüíneos de bovinos lactantes, desmamados e adultos das raças Nelore (Bos indicus) e Holandesa (Bos taurus) e de bubalinos (Bubalus bubalis) da raça Murrah

Blood samples from lactating, weaned and adult Holstein-Fresiean and Nelore cattle and Murrah buffaloes were tested through the study of hemogram and serum constituents. Red cell and leukocyte counts, and blood pH, fibrinogen, glucose, calcium, and phosphorus levels were similar in cattle and buffalo. Total protein, urea, creatinine, hemoglobin, magnesium, iron and aspartato aminotransferase and alanine aminotransferase activities were higher in buffalo than cattle. Leukocyte counts were higher for weaned Holstein cattle than for Nelore cattle but similar to buffalo and Nelore cattle had the lowest neutrophil counts. Bilirrubin levels were lower for buffalo than for cattle. Phosphatase alkalyne activities were lower for weaned buffalo than for other animals. Gammaglutamyltransferase activities were the highest for lactating and weaned buffalo.

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.

Comparison of embryo yield and pregnancy rate between in vivo and in vitro methods in the same Nelore (Bos indicus) donor cows

To investigate why the preferred means to produce bovine embryos in Brazil has changed from in vivo to in vitro, we compared these two approaches in the same Nelore cows (n = 30) and assessed total embryo production and pregnancy rates. Without a specific schedule, all cows were subjected to ultrasound-guided ovum pick up (OPU)/in vitro production (IVP) and MOET, with intervals ranging from 15 to 45 d between procedures, respectively. To produce in vivo embryos, cows were superovulated and embryos were recovered nonsurgically from 1 to 3 times (1.4 +/- 0.6). whereas OPU/IVP was repeated from 1 to 5 times (3.2 +/- 1.2) in each donor cow during a 12-mo interval. Embryos obtained from both methods were transferred to crossbred heifers. on average. 25.6 +/- 15.3 immature oocytes were collected per OPU attempt. The average number of embryos produced by OPU/IVP (9.4 +/- 5.3) was higher (P < 0.05) than the MOET method (6.7 +/- 3.7). However, pregnancy rates were lower (P < 0.05) following transfer of IVP (33.5%) versus in vivo-derived embryos (41.5%) embryos. Embryonic losses between Days 30 and 60 and fetal sex ratio were similar (P > 0.05) between in vivo and in vitro-derived embryos. We concluded that in Nelore cows, with an interval of 15 d between OPU procedures, it was possible to produce more embryos and pregnancies compared to conventional MOET. (C) 2009 Elsevier B.V. All rights reserved.

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.

Perfil de FSH e LH na divergência folicular em novilhas Nelore (Bos indicus)

Present study aimed to evaluate gonadotropins profiles in 12 Nelore heifers, in order to test the hypothesis that FSH concentrations decrease and LH presents a transient increase during follicle selection. Blood samples from jugular vein were harvested twice daily starting at the time of ovulation (D0) until D5. Plasma samples were assayed for FSH and LH by double antibody radioimmunoassay method. LH and FSH assay sensitivity was 0,02ng/ml and 0,005ng/ml, respectively. The intraassay coefficient of variation was 13,6% and 18,8%, respectively. Data (mean±SEM) were normalized to follicle deviation and analyzed by ANOVA and by linear, cubic, and quadratic regressions. Comparisons between higher and lower FSH values were also performed by T-test. There was no effect of time in plasmatic FSH and LH circulating levels when variance analysis or regression analysis were performed. However, by T-test, FSH concentrationsreached the lowest plasmatic levels 36 (0,40±0,05ng/ml) and 60 hours (0,42±0,04ng/ml) after follicular deviation, comparatively to 36 hours before deviation, when the concentrations were maximal (0,63±0,08ng/ml). In conclusion, there is a FSH decrease, although a transient LH elevation has not been confirmed encompassing follicle deviation in Nelore females.