Ovulation rate and its relationship with follicle diameter and gene expression of the LH receptor (LHR) in Nelore cows

The objective was to determine the relationship among the diameter of ovarian follicles, ovulation rate, and gene expression of the LH receptor (LHR) in Nelore cattle. In Experiment 1, ovulation was synchronized in 53 Nelore cows. Three days after ovulation, ovaries were assessed with ultrasonography, all cows were given 6.25 mg LH im, and they were allocated into three groups, according to diameter of their largest ovarian follicle: G1 (7.0-8.0 mm); G2 (8.1-9.0 mm); and G3 (9.1-10.0 mm). For these three groups, ovulation rates were 9, 36, and 90%, respectively, (P < 0.03; each rate differed significantly from the other two). In Experiment 2, granulosa and theca cells were subjected to total RNA extraction, and gene expression of the LHR was determined by RT-PCR. Follicles were allocated in three groups based on their diameter (similar to the Experiment 1), which were denoted Groups A, B, and C. Expression of the LHR gene in granulosa cells was lower in Group A than Group C (P < 0.05). However, there were no significant differences among groups in expression of the LHR gene in theca cells. We concluded that ovulatory capacity in Nelore cattle was related to increased follicular diameter and expression of the LHR gene in granulosa cells. (C) 2012 Elsevier B.V. All rights reserved.

Ovarian function in cows submitted to acute stress during proestrus

Studies in which ACTH was administrated in heifers after the occurrence of luteolysis showed a delay in the onset of estrus and the estrus duration was shortened. This study evaluated the effect of acute stress by road transportation on estrous behavior and ovulation, monitored by serum progesterone and cortisol concentrations in cows at the periovulatory period, using a crossover design. Eleven crossbred cows, divided into Control and Transport groups had their estrus cycle synchronized with GnRH, an intravaginal progesterone device, and cloprostenol. Thirty hours after withdrawal of the device, the animals of the Transport group were transported for 60 min by truck and those from the Control group remained at pasture. Ovarian ultrasound examination was performed every 12 h from device withdrawal until ovulation in every cow. From the day after removal of the device until ovulation estrous behavior was monitored 24 h a day. Blood samples for serum cortisol and progesterone concentrations were taken at -90, -60, 0, 30, 60 and 180 min in relation to the end of transportation. Transportation during the estrous period induced stress in cows as reflected by changes in serum concentrations of progesterone and cortisol. However, we did not detect impairment in estrus expression, estrus duration or ovulation (P>0.05). (C) 2010 Elsevier B.V. All rights reserved.

Immunohistochemical detection of receptors for oestrogen and progesterone in endometrial glands and stroma during the oestrous cycle in Nelore (Bos taurus indicus) cows

The aim of the present study was to monitor endometrial distribution and concentrations of oestrogen receptors alpha (ER alpha) and progesterone receptors (PR) by immunohistochemistry in Nelore cows (Bos taurus indicus) during the oestrous cycle. Blood samples were collected for progesterone measurement and endometrial samples were taken from the uterine horn contra lateral to the corpus luteum in 16 cows at days 0 (ovulation), 5, 9, 13 and 19 of the oestrous cycle. Immunostaining evaluation for ER alpha and PR in the glandular epithelium and uterine stroma was performed by two methods: positive nuclei counting and staining intensity of the nuclei. Specific positive staining reactions for both receptors were limited to cell nuclei and they were not identified in the cytoplasm. The proportion of ER alpha positive nuclei had a temporal variation throughout the oestrous cycle in both cell types evaluated and was higher in uterine stroma than the glandular epithelium (p < 0.05). The greatest proportion of ER alpha stained nuclei was observed at oestrus and during the initial and mid luteal phase (days 5, 9 and 13) (p < 0.05) in the glandular epithelium and at days 0, 5 and 9 in the uterine stroma (p < 0.01). The proportion of PR positive nuclei remained constant throughout the entire oestrous cycle for both cell types evaluated (p > 0.05). A higher proportion of PR positive nuclei was measured in the uterine stroma compared with the glandular epithelium (p < 0.05). Intensity of staining for ER alpha and PR varied throughout the oestrous cycle (p < 0.01). There was a higher staining intensity at days 0 and 5 in the stroma for ER alpha (p < 0.01) and PR (p < 0.01) and in the glandular epithelium at days 0, 5, 9 and 13 for ER alpha (p < 0.01) and at days 0, 5 and 9 for PR (p < 0.01) when compared with the other evaluated days. These data demonstrate that ER alpha and PR expression varied throughout the oestrous cycle in Nelore cows, in general with highest concentrations at oestrus and the lowest during the luteal phase. This is similar to patterns observed in Bos taurus taurus.

Reuse of norgestomet implants in an eCG-based superovulation protocol administered to Nelore (Bos taurus indicus) cows

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

Effects of two estradiol esters (benzoate and cypionate) on the induction of synchronized ovulations in Bos indicus cows submitted to a timed artificial insemination protocol

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synchronization of ovulation in beef cows (Bos indicus) using GnRH, PGF2 alpha and estradiol benzoate

The objective of this study was to evaluate protocols for synchronizing ovulation in beef cattle. In Experiment 1, Nelore cows (Bos indicus) at random stages of the estrous cycle were assigned to 1 of the following treatments: Group GP controls (nonlactating, n=7) received GnRH agonist (Day 0) and PGF2 alpha (Day 7); while Groups GPG (nonlactating, n=8) and GPG-L (lactating, n=9) cows were given GnRH (Day 0), PGF2a (Day 7) and GnRH again (Day 8, 30 h after PGF2 alpha). A new follicular wave was observed 1.79+/-0.34 d after GnRH in 19/24 cows. After PGF2a, ovulation occurred in 19/24 cows (6/7 GP, 6/8 GPG, 7/9 GPG-L). Most cows (83.3%) exhibited a dominant follicle just before PGF2a, and 17/19 ovulatory follicles were from a new follicular wave. There was a more precise synchrony of ovulation (within 12 h) in cows that received a second dose of GnRH (GPG and GPG-L) than controls (GP, ovulation within 48 h; P<0.01). In Experiment 2, lactating Nelore cows with a visible corpus luteum (CL) by ultrasonography were allocated to 2 treatments: Group GPE (n=10) received GnRH agonist (Day 0), PGF2a (Day 7) and estradiol benzoate (EB; Day 8, 24 h after PGF2 alpha); while Group EPE (n=11), received EB (Day 0), PGF2a (Day 9) and EB (Day 10, 24 h after PGF2a). Emergence of a new follicular wave was observed 1.6+/-0.31 d after GnRH (Group GPE). After EB injection (Day 8) ovulation was observed at 45.38+/-2.03 h in 7/10 cows within 12 h. In Group EPE the emergence of a new follicular wave was observed later (4.36+/-0.31 d) than in Group GEP (1.6+/-0.31 d; P<0.001). After the second EB injection (Day 10) ovulation was observed at 44.16+/-2.21 h within 12 (7/11 cows) or 18 h (8/11 cows). All 3 treatments were effective in synchronizing ovulation in beef cows. However, GPE and, particularly EPE treatments offer a promising alternative to the GPG protocol in timed artificial insemination of beef cattle, due to the low cost of EB compared with GnRH agonists. (C) 2000 by Elsevier B.V.

Gastrointestinal helminths in calves and cows in an organic milk production system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Risk factors relating to helminth infections in cows during the peripartum

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Daily intake of lactating crossbred cows grazing elephant grass rotationally

O objetivo deste trabalho foi o de estimar o consumo total e o diário de matéria seca do pasto, de vacas mestiças Holandês - Zebu, em piquetes de capim-elefante (Pennisetum purpureum Schum.). Três grupos de 24 vacas foram usados em piquetes (4,5 vacas/ha), pastejados por três dias e submetidos a diferentes períodos de descanso durante dois anos. Os tratamentos consistiram de descansos de 30 dias sem concentrado e 30, 37,5 e 45 dias com a suplementação de 2 kg de concentrado (20,6% de proteína bruta). de julho a outubro, as vacas receberam, como suplementação, cana-de-açúcar mais 1% de uréia. O consumo total de matéria seca foi estimado a partir da digestibilidade in vitro da matéria seca da extrusa e da produção fecal obtida com óxido crômico. Independentemente do tratamento, o consumo total foi 2,7; 2,9 e 2.9±0,03%, e o consumo de matéria seca do pasto foi de 1,9; 2,1 e 2,1±0,03% do peso vivo (p<0,05), respectivamente, no primeiro, segundo e terceiro dia de ocupação do piquete. Somente no verão, o consumo do pasto foi semelhante nos três dias de pastejo. A mistura cana-de-açúcar e uréia substituiu o pasto, principalmente no primeiro dia de pastejo, ocasião em que o consumo do pasto era mais baixo.