RESUMO

Laboratory tests in which a fluid or combination of fluids that are injected into a core rock are designed to determine oil reservoir rock petrophysical properties, understand the mobility of fluid flow in the porous samples, and calibrate porous media fluid flow models. The core material is extracted from the oil reservoir. However, the manufacture of core plugs is challenging because of the complexity of extracting natural rocks from the reservoir and their morphological and atypical heterogeneity. In addition, core flooding tests are essentially destructive, making it impossible to achieve experimental repeatability by using identical cores. The use of 3D printing in digital rock physics has permitted the production and replication of synthetic rock samples with the morphological characteristics of natural rocks for core analysis and core flooding tests. This study proposes the 3D manufacture of artificial core plugs from microcomputed tomography of Berea sandstone. The digital samples were constructed using a digital particle packing approach by systematically manipulating rock textural parameters, such as the grain size and shape, cementation pattern, and sorting grain, making it possible to obtain a core plug that fulfills experimental requirements. Before the 3D printing of the sample, the flow distribution through the porous media structure was numerically simulated using the Lattice Boltzmann method to obtain the core plug samples' permeability and porosity. The core plug was digitally embedded within a core holder to generate a stereolithography file for 3D printing of the core flooding setup, which can be used directly in conventional experiments. The permeabilities of the 3D printed plugs were experimentally determined to permit a direct comparison to the numerical results and evaluate the utility of printed plugs for displacement experiments.

RESUMO

The present experiments on goats were conducted with the aim of verifying (a) whether the identity of the goat kids can affect the characteristics of milk let-down during suckling (Study 1) and (b) whether the presence of the goat kids may improve the milk let-down during hand milking (Study 2). In Study 1, 16 lactating goats with twins and 12 with single kids were used. Dams with single goat kids ejected more milk when suckling their kids at Days 5 and 20 of lactation, than when suckling aliens. Dams with twins ejected more milk when suckling their own kids than aliens only at Day 5 of lactation. Taking into account all the dams, they ejected more milk with more fat, protein, and lactose during suckling their own litter than when suckling aliens. In Study 2, when dams (n = 13) were hand milked in the presence of their own litter or in its absence, they ejected more milk with more fat, protein, and lactose than when milked in the presence of alien kids. We conclude that milk let-down in goats can be influenced by the type of stimuli applied or to which they are exposed to during suckling and milking.

Assuntos

RESUMO

Sexually inexperienced ewes display lower estrous behavior during the first contact with rams. The objective of this study was to determine whether sexually inexperienced anestrous females display estrous behavior and ovulatory activity as the sexually experienced females, and with restricted sexual experience exposed to photo-stimulated bucks. Six bucks were rendered sexually active during the non-breeding season by exposure to artificially long days (16 h of light and 8 h of darkness per day) for 2.5 months. The first group, sexually experienced females (n = 10) had physical contact with two vasectomized bucks, and mating was allowed; the second group, with restricted sexual experience (n = 10) had contact with two vasectomized bucks through a wire-mesh fence and mating was prevented; the third group, sexually inexperienced females (n = 9) was totally isolated from bucks. At 14-month-old the females were exposed to photostimulated bucks for 15 days. The proportion of females that displayed estrous behavior, ovulations, short and normal ovulatory cycles, and pregnancy rates did not differ between sexually experienced, with restricted sexual experience, and sexually inexperienced (P > 0.05, in all variables). Similarly, the ovulation rate did not differ between the three groups of females (P > 0.05). However, the interval from introduction of the bucks to the first estrus was shorter in sexually inexperienced females (P < 0.05). Therefore, sexually inexperienced anestrous females displayed estrous behavior, ovulation, and pregnancy rate similar to those displayed by sexually experienced and with restricted sexual experience when exposed to photo-stimulated bucks through the male effect.

Assuntos

RESUMO

Sexually inexperienced ewes display lower estrous behavior during the first contact with rams. The objective of this study was to determine whether sexually inexperienced anestrous females display estrous behavior and ovulatory activity as the sexually experienced females, and with restricted sexual experience exposed to photo-stimulated bucks. Six bucks were rendered sexually active during the non-breeding season by exposure to artificially long days (16 h of light and 8 h of darkness per day) for 2.5 months. The first group, sexually experienced females (n = 10) had physical contact with two vasectomized bucks, and mating was allowed; the second group, with restricted sexual experience (n = 10) had contact with two vasectomized bucks through a wire-mesh fence and mating was prevented; the third group, sexually inexperienced females (n = 9) was totally isolated from bucks. At 14-month-old the females were exposed to photostimulated bucks for 15 days. The proportion of females that displayed estrous behavior, ovulations, short and normal ovulatory cycles, and pregnancy rates did not differ between sexually experienced, with restricted sexual experience, and sexually inexperienced (P > 0.05, in all variables). Similarly, the ovulation rate did not differ between the three groups of females (P > 0.05). However, the interval from introduction of the bucks to the first estrus was shorter in sexually inexperienced females (P < 0.05). Therefore, sexually inexperienced anestrous females displayed estrous behavior, ovulation, and pregnancy rate similar to those displayed by sexually experienced and with restricted sexual experience when exposed to photo-stimulated bucks through the male effect.(AU)

Assuntos

RESUMO

This study was designed to determine whether any relationship exists between exposure to artificial long days, milk yield, maternal plasma insulin-like growth factor 1 (IGF-1) levels, and kid growth rate in goats. One group of lactating goats was maintained under naturally decreasing day length (control group; n = 19), while in another one, they were kept under artificial long days (LD group; n = 19). Milk yield was higher in goats from the LD group than that in the control group (P < 0.05). Maternal IGF-1 levels at day 57 of lactation were higher (P < 0.05) in goats from the LD group than the levels in the control group and were positively correlated with the total milk yields per goat at days 43 and 57 of lactation (r = 0.77 and r = 0.84, respectively; P < 0.01). Daily weight gain at week 4 was higher (P < 0.01) in kids from the LD group than that in kids from the control group and was correlated with total and average IGF-1 maternal levels (r = 0.60 and r = 0.60, P < 0.05). It was concluded that submitting lactating goats to artificial long days increases milk yield, plasma IGF-1 maternal levels and the growth rate of the kids.

Assuntos

RESUMO

We investigated whether live vocalizations emitted by bucks interacting with anestrous females stimulate secretion of LH, estrous behavior and ovulation in anestrous goats. In experiment 1, bucks rendered sexually active by exposure to long days followed by natural photoperiod were exposed in a light-proof-building to five anestrous females. Buck vocalizations were reproduced through a microphone-amplifier-loudspeaker system to an open pen where one group of goats (n=6) was exposed for 10 days to these live vocalizations. Another group of females (n=6) was isolated from males and vocalizations. The proportion of goats displaying estrous behavior was significantly higher in females exposed to buck vocalizations than in females isolated from males. The proportion of goats that ovulated did not differ between the 2 groups (exposed to males versus isolated). In experiment 2, female goats that either had previous contact with males (n=7), or no previous contact with males (n=7) were exposed to live buck vocalizations, reproduced as described in experiment 1, for 5 days. The number and amplitude of LH pulses did not differ between groups before exposition to buck vocalizations. Five days of exposure to male vocalizations significantly increased LH pulsatility only in females that had previous contact with males, while LH pulse amplitude was not modified. We concluded that live buck vocalizations can stimulate estrous behavior and LH secretion in goats if they have had previous contact with bucks.

Assuntos

RESUMO

We investigated whether LH secretion, estrous behavior and fertility would differ between sexually inexperienced and experienced anestrous goats exposed to the males. Male goats were rendered sexually active during the reproductive rest season by exposure to 2.5 months of artificial long days. Two groups of anovulatory sexually inexperienced and sexually experienced does were exposed to males during 15 days (n = 20 per group). LH pulsatility was determined every 15 min from 4h before to 8h after introducing males (Day 0). Estrous behavior was recorded twice daily. Pregnancy rates were determined on Day 50. Fertility was determined at parturition. Male sexual behavior was registered on days 1 and 2 during 1h. Before introducing the males, the number of LH pulses did not differ between groups. After introduction of the males, all females increased their LH pulsatility, but the number of pulses did not differ between sexually inexperienced and experienced goats. The proportion of females displaying estrous behavior with a high pregnancy rate and fertility did not differ between inexperienced and experienced goats. The sexual behavior of the males did not differ significantly between those interacting with sexually inexperienced or experienced goats. We conclude that goats can show substantial endocrine and reproductive responses to males, even in the absence of previous sexual experience, when sexually active bucks are used.

Assuntos