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

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C.G. Gutier utierrez, S. Fer errar aro, V. Mar artine tinez, et al. <strong>2011</strong>. Increasing ovulation quota: more than a matter of energy. sssssss sss Acta Scientiae Veterinariae. 39(Suppl 1): s305 - s316. and the fatty acid preferably produced after fermentation may alter the glycogenic capacity of the substrate. We studied the in vitro rumen fermentation and the in vivo response of sheep to an isoenergetic (1470.83 kcal) single oral drench of glycerol, propylene glycol or molasses. We observed that glycerol and propylene glycol increased (P < 0.01) the proportion of propionate production in vitro [9]. Glycerol remained unfermented for the longest time as shown by the greater lag time (10h; P < 0.05) and molasses showed a fastest rate of gas production and (P < 0.05) the shortest time to be fermented (Table 3). In vivo, glycerol and propylene glycol increased glucose plasma concentration for up to 12 h after treatment (Figure 3). Insulin secretion increased for a period of 12 h in the glycerol and propylene glycol groups (P < 0.01). In contrast, molasses caused a mild increase in both glucose and insulin that lasted for less than 60 and 12 min respectively (Figure 3) [9]. Hence, the results of this trial showed important differences in the fermentation and glycogenic responses to these three energetic substrates. The longer lag time of glycerol allows for its absorption and its direct use for glucose production by the liver. Propylene glycol has a similar lag time than molasses, but it is preferably fermented to propionic acid thus serving as glycogenic substrate. Thus, glycerol and propylene glycol cause a large and sustained increase in insulin concentrations that together with glucose may enhance ovulation rate. V. WHAT IS THE MINIMUM DOSE NEEDED TO INCREASE OVULATION RATE WITH AN ULTRASHORT FLUSING? So far, we have established that USF with a single drench of 300 ml of a 90% glycerol solution coinciding with the initiation of luteolysis augments the number of ovulations and is associated with a 12h increase in glucose and insulin. In addition, this increase in ovulation rate is related to reduced aromatase mRNA abundance in the ovulatory follicles at 12 h after treatment. Thus, we have limited the time frame where follicles are selected to add to the ovulation quota within a 12h period after luteolysis. However, this period of time could actually be shorter than the period indicated by the results already shown. In all cases, the ultrashort flushing does not alter the body condition score or weight of the ewe and seems to act by its effects on insulin and glucose concentrations rather than the net amount of energy given to the animal. Although flushing can be limited to a single glycogenic drench at the time of luteolysis, we observed as much as 43% of superovulated animals with the 300 mL glycerol dose (Table 2). Thus, the determination of a minimum flushing dose could help reduce the incidence of triple and quadruple ovulations. One hundred and twenty sheep were scanned by ultrasonography to determine their ovulation rate, and were randomly divided into four groups of 30 ewes each that received 300, 200, 100 or 50 mL of glycerol at the time of PGF2α injection. Flushing at all the doses tested increased ovulation rate (P< 0.01). A hundred milliliters of glycerol solution caused the highest ovulation rate. However, doses of 100 mL or above superovulated between 17 and 25% of the sheep (Table 4). Thus, it appears that ultrashort flushing with 50 mL dose is sufficient to cause an increase in ovulation rate without the hindrance of superovulation in sheep [22]. VI. OTHER MANIPULATIONS TO INCREASE OVULATION RATE The static effect of flushing on ovulation quota is apparently due to an increase in the number of Table 3. Cumulative gas production and estimated kinetic parameter model for liquid energetic sources. Substrate Maximum volume (Y), mL -1 Rate of gas production (s), h Lag time (L), h Glycerol 320 µL 178.4 b 0.024 e 10.23 b Propylene glycol 320µL 22.6 d 0.062 c 1.81 d Molasses 320 µL 161.5 cb 0.085 a 1.86 d SEM 4.03 0.001 0.12 R 2 0.98 0.98 0.99 P value of regression model 0.0001 0.0001 0.0001 abc Means within column with different superscript differ (P < 0.05). s310
C.G. Gutier utierrez, S. Fer errar aro, V. Mar artine tinez, et al. <strong>2011</strong>. Increasing ovulation quota: more than a matter of energy. sssssss sss Acta Scientiae Veterinariae. 39(Suppl 1): s305 - s316. N Figure 3. Mean blood concentrations of insulin and glucose at different times after an oral drench (1470.8 Kcal) of glycerol, propylene glycol or molasses in ewes. Values are means ± S.E.D. of logarithmic transformation of insulin and glucose concentrations. Mean values with different letters differ (P < 0.05). gonadotropin responsive follicles. It appears that the increase of glucose and insulin is responsible for the increase in follicular development and, consequently, for the number of available follicles for ovulation. But then, could any nutritional of hormonal treatment that increases insulin cause an increase in ovulation rate We conducted a series of studies to test the effect of treatments that enhance glucose redistribution on the number of small antral follicles growing in the ovaries. However, an increase in the number of gonadotropin responsive follicles is difficult to evaluate in sheep, as the diameter of the gonadotropin sensitive follicles (2 mm) is close to the lower range of sensitivity of the ultrasound scanner. To circumvent this inconvenience, we carried out the first study in cattle, where the gonadotropin sensitive follicles grow up to 4 mm in diameter and can be easily counted by transrectal ultrasound scanning. In addition, we used the gonadotropin inhibited model [16], where cattle are treated chronically with a GnRH agonist for a long period of time, with a consequent inhibition of the pulsatile release of LH and FSH to their basal concentrations, and the arrest of follicle development at 4 mm in diameter. Since dominant follicles do not develop, the gonadotropin sensitive follicles grow without the restrain and the fluctuating inhibition of dominant follicles. Nineteen cows were treated with a continuous infusion of buserelin (37.5 ng/h) for six months after which s311
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A262 Bovine Oocyte Vitrification: E
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