2011 (SBTE) 25th Annual Meeting Proceedings - International ...

Acta Scientiae Veterinariae, 2011. 39(Suppl 1): Abstracts - 25th Annual Meeting SBTE-Brazil. August 2011.
A165 EMBRYOLOGY, BIOLOGY OF DEVELOPMENT AND PHYSIOLOGY OF REPRODUCTION
BREEDING SEASON ANTICIPATION TION IN MARES SUBMITTED
TED TO A PROGESTER
OGESTERONE ONE INTRAVAGINAL IMPLANT OR ARTIFICIAL
LIGHTING
Rob
ober
erta Pahim de Melo
elo, Fer
ernanda Saules Ignácio, Jair Camar
amargo Fer
erreir
eira,
José Nicolau P. Puoli Filho & Cezinande Meir
eira
FMVZ - UNESP, BOTUCATU, SP, BRAZIL.
The present study was done aiming to evaluate the use of progesterone intravaginal implants on mares’ ovulation anticipation and
to compare with the use of artificial lighting. For this use, 27 cross-breeding mares were randomly assigned into three groups: P4 (n = 7;
progesterone intravaginal implant; Primer ® , 1g of progesterone with no estradiol), lighting (n = 10; artificial lighting program) and control (n =
10; not treated). In P4 group, the progesterone intravaginal implant was introduced and kept for 12 days when transitional phase characteristics
were detected. Animals of the lighting group were daily treated with five hours of artificial lighting (5 to 10 pm) for 60 days, beginning at June
21st. For the comparison of the evaluated intervals among P4, lighting and control groups, analysis of variance followed by Tukey test were
used. For the first ovulation frequency, a chi-square test was used. The progesterone intravaginal implant reduced the interval until detection of
a follicle =35mm when comparing to control group and was similar to mares under artificial lighting program. The findings of =35mm follicles
in P4 group indicate that implant had a higher efficiency on follicular growth stimulation. The interval between transitional phase detection to
=35mm follicles were similar among groups, but the moment transitional phase were detected was different. All mares in P4 group showed
follicles =35mm during treatment to five days post treatment. Even though the largest follicle achieved =35mm, the mean days from removal to
ovulation was of 20.6 days, which was higher than 6.6 days found by Newcomb, 2002 (Journal of equine veterinary science. 22, 378-382). This
difference is explained by the two mares that showed largest follicles regression. Considering the mean interval (days) between winter solstice
and ovulation, lighting treatment was efficient compared to control. The use of progesterone implants showed regular efficiency and it was
similar to both other groups. This fact probably happened because of two mares that ovulated in late December and the cause was not established.
In relation to frequency of ovulation distribution along months, as lighting treatment as progesterone implant promote ovulations earlier in the
breeding season when compared to control (P < 0,05). Concluding, lighting treatment and progesterone implants when used in transitional mares
efficient to promote a higher frequency of ovulations early in the breeding season.
Keywords: p4, lighting, ovulation.
A166 EMBRYOLOGY, BIOLOGY OF DEVELOPMENT AND PHYSIOLOGY OF REPRODUCTION
EVAL
ALUATION OF HYPOTHAL
THALAMIC-PITUIT
AMIC-PITUITAR
ARY RESPONSIVENESS DURING THE POSTPAR
ARTUM NELLORE COWS
Cir
iro Mor
oraes Bar
arros
os, José Rena
enato Cur
ury, Rafael August
ugusto Satr
trapa,
Mar
arcelo Pegor
egorer
er, Luzia Apar
parecida
Trinc
inca & Vinicius Pinheir
inheiro
UNESP, BOTUCATU, SP, BRAZIL.
The presence of calf, body condition score, energy balance, number of births (multiparous vs. primiparous) and breed are factors
that influence the duration of postpartum anoestrus in beef cows. The objective of the present study was to evaluate, during early postpartum, the
time of re-establishment of pituitary LH stocks, mensured by the hypothalamic-pituitary axis responsiveness to exogenous administration of
GnRH or estradiol benzoate (EB). Multiparous lactating Nellore cows (Bos indicus, n = 90) were randomly allocated into eight groups,
according to the hormonal treatment: EB group (1.0 mg of EB, i.m., n = 7), GnRH group (50 µg lecireline, i.m., n = 17). The EB-SUP (n = 9)
and GnRH-SUP (n=11) groups received the same treatments above specified and were supplemented (SUP) with a balanced diet, based on
cotton meal and ground corn (3.5 kg/cow/day). Additionally, animals from EB-CR (n = 4) and GnRH-CR (n = 11) received the same treatments
of EB and GnRH group respectively and had their calf removed (CR) shortly after parturition. Moreover, two other groups were LH (LH 12.5
mg, i.m., n = 14) and Control group (received saline instead of an ovulation-inducing agent, n = 11). The hormones were administered weekly,
from seven days postpartum (±5 days) until the occurrence of the first ovulation, which was determined by the presence of CL during ovarian
ultrasonography weekly performed. Blood samples were collected just before and 2 h (GnRH, LH and control groups) or 18 h (EB groups) after
hormone or saline (control) administration, in order to determine LH concentration by RIA. Data were analyzed by ANOVA. Means values in
days (±SEM) for the first post-partum LH surge were: EB (73.0±5.2); EB-CR (16.7±5.8); EB-SUPL (41.7±6.7); GnRH (32.3±3.0); GnRH-
CR (11.0±3.5); GnRH-SUPL (15.6±2.8). There were significant differences (P, 0.05) between groups EB vs.. EB-CR; EB vs. EB-SUP; BE vs..
GnRH; GnRH vs.. GnRH-CR; GnRH vs.. GnRH-SUP, and a tendency between EB-SUPL vs. EB-CR (P < 0.10). Results indicate that from
the second week postpartum there is sufficient LH in the pituitary to induce ovulation after GnRH or EB administration. However, the cows from
EB group ovulated later than animals from the other groups, possibly due to the sensitivity of the hypothalamus to negative feedback of
estrogens, inhibiting the pre-ovulatory LH surge. Additionally, calf removal and food supplementation reduced in 2 to 4 weeks the time of the
first postpartum LH surge induced by GnRH or EB in Nellore cows.
Keywords: post-partum, lh, bovine.
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