The main goal of this study was to assess the usefulness of two imaging modalities, namely the B-mode and colour Doppler sonography, and serum progesterone (P ) concentrations for determining the ovarian response in superovulated ewes. Twenty-four sexually mature Santa Inês ewes underwent the superovulatory treatment consisting of eight injections of porcine FSH (total dose of 200 or 133 or 100 mg; n = 8 ewes/total dose) given at 12-hr intervals and initiated 48 hr before CIDR (Pfizer Inc., Auckland, New Zealand) removal. Six days after natural mating, the ovaries of all donor ewes were visualized and examined with transrectal ultrasonography and then with videolaparoscopy to identify and enumerate corpora lutea (CL) and luteinized unovulated follicles (LUFs). Jugular blood samples were collected just prior to ovarian examinations. The total number of CL (r = .78 and 0.83, p < .0001) and LUFs (r = .74 and 0.90, p < .0001) enumerated using the B-mode and colour Doppler ultrasonographic technique, respectively, were correlated with that ascertained by videolaparoscopy. Circulating concentrations of P were related directly to the number of healthy CL (r = .73, p = .0002) and inversely to the number of prematurely regressing CL (r = -.46, p = .03), but the accuracy of predicting the number of short-lived CL with serum P concentrations was very poor. The present results indicate that ultrasonographic imaging and serum P measurements on the day of embryo recovery are useful indicators of total/normal CL numbers and both ultrasonographic techniques can be used to quantify LUFs in superovulated ewes.

RESUMO: A paca é um grande roedor, presente em parte do território brasileiro e na América Latina, cuja importância está na crescente produção comercial de carne exótica e na pesquisa científica como um promissor modelo experimental. Assim, este trabalho objetivou-se descrever a morfologia e a topografia do baço da paca (Cuniculus paca). Foram utilizadas cinco pacas adultas, machos e fêmeas, fixadas em formaldeído a 10% e armazenados em solução salina a 30% para sua conservação. Na paca, o baço tem sua localização relacionada ao estômago, ao fígado, ao rim esquerdo, ao pâncreas e ao omento maior. Possui forma irregular, sendo mais longo do que largo, possui coloração avermelhada-escura e textura lisa. Quanto à descrição histológica, apresenta cápsula de tecido conjuntivo denso que emitiu trabéculas que se projetam no parênquima. A cápsula e as trabéculas apresentam fibras musculares lisas. O parênquima è composto pela polpa branca e polpa vermelha, esta última formada por seios e cordões esplênicos.

The main goal of this study was to assess the usefulness of the 2 imaging modalities—B-mode and colour Doppler sonography—for determining the superovulatory response in ewes. In addition, serum concentrations of progesterone (P4) were examined for correlations with the numbers of laparoscopically detected luteal structures. Oestrus was synchronized in 24 sexually mature Santa Inês ewes with intravaginal P4-releasing devices (CIDR®) inserted for 8 days on a random day of the oestrous cycle. An injection of 37.5 μg of prostaglandin F2α analogue (d-cloprostenol) was given at the time of CIDR® insertion and withdrawal. The superovulatory treatment consisting of 8 consecutive doses of porcine FSH (total dose of 200 or 133 or 100 mg of pFSH; n = 8/total dose) given at 12-h intervals began 48 h before CIDR® removal. All animals received a single injection of 300 IU of eCG concurrently with a first dose of pFSH. On the day of surgical embryo recovery (6 days after the onset of behavioural oestrus), the ovaries of all donor ewes were visualised and examined with transrectal ultrasonography and then with videoendoscopy to identify and enumerate corpora lutea (CL) and luteinized unovulated follicles (LUF). Jugular blood samples were collected just before ovarian imaging for the measurement of circulating P4 concentrations. Ovaries could be easily and repeatedly detected with both the transrectal ultrasonography and videoendoscopic technique. Prematurely regressing CL could not be distinguished from healthy CL using either B-mode or colour Doppler ultrasonography but they were identified by their pale color by using videoendoscopy. All animals responded to the superovulatory treatment and produced ≥4 CL; however, a wide variation in ovarian responses was observed among ewes (range: 4–24 CL/ewe). Three ewes failed to produce healthy CL and had prematurely regressing CL only. In general, LUF were observed in 20/24 ewes (1–5/ewe) and 14/24 ewes had regressing CL (1–22/ewe). The total number of CL (r = 0.78 and 0.83; P < 0.0001) and LUF (r = 0.74 and 0.90; P < 0.0001) enumerated using the B-mode and colour Doppler ultrasonographic technique, respectively, were correlated with that ascertained by videoendoscopy. The determination of the superovulatory response was better by colour Doppler ultrasonography in relation to the B-mode, because it allows a better delimitation of the luteal structures. Serum P4 concentrations were related inversely to the numbers of prematurely regressing CL (r = –0.70; P = 0.0004) and directly to the number of healthy CL (r = 0.69; P = 0.0005). The present results indicate that ultrasonographic imaging and serum P4 measurements on the day of embryo recovery are both very accurate indicators of ovarian responses in superovulated ewes.