I. Valasi

Health management of ewes during pregnancy

The objectives of health management of ewes during pregnancy are as follows: (i) successful completion of pregnancy at term, (ii) birth of healthy and viable lambs, with optimal birth and potential weaning bodyweight, (iii) optimum milk production during the subsequent lactation and (iv) improved management in relation to drug residues in animal products. Knowledge of the physiological background of pregnancy in ewes: changes, mechanisms and interactions, during pregnancy is important for the overall health management of ewes during pregnancy. Health management of pregnant ewes includes diagnosis of pregnancy and evaluation of the number of foetuses borne, which will support strategies for subsequent management of the flock. Nutritional management of ewes depends upon the stage of lactation and specifically aims to (i) prevention of pregnancy toxaemia and other metabolic diseases during the peri-partum period, (ii) formation of colostrum in appropriate quantity and quality, (iii) production of lambs with normal future birth bodyweight and (iv) support of increased milk yield during the subsequent lactation. At the end of lactation, udder management of pregnant ewes includes its clinical examination, culling of ewes considered unsuitable for lactation and, possibly, the intramammary administration of antibiotics; objectives of that procedure are (i) to cure infections which have occurred during the previous lactation and (ii) to prevent development of new mammary infection during the dry period. Management of abortions includes the correct and timely diagnosis of the causative agent of the disorder, as well as the strategic administrations of chemotherapeutic agents, aiming to prevent abortions in flocks with confirmed infection with an abortifacient agent, especially if no appropriate vaccinations had been carried out before the mating season. During the final stage of pregnancy, health management of ewes includes administration of appropriate anthelmintic drugs, aiming to eliminate gastrointestinal helminthes (thus, increasing production output of ewes) and preventing the built-up of parasitic burdens in the environment (thus, reducing infection of lambs during their neonatal period). Vaccinations of pregnant ewes aim to protect these animals, as well as their offspring, especially against diseases which are a frequent cause of neonatal mortality (e.g., clostridial infections). Health management also aims to prevent the main metabolic disorders of pregnant ewes (i.e., pregnancy toxaemia and hypocalcaemia), as well as to monitor flocks for development of these disorders. Health management of pregnant ewes is completed with application of husbandry practices before the start of the lambing season. Finally, in some cases, health management may include induction and synchronisation of lambings, which is a management or therapeutic procedure.

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation.

Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups (A, B and C; n = 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle (oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F2+/- (PGF2+/-) injection, and the animals were inseminated 12-14 h after the second GnRH injection (modified OVSYNCH). For luteinising hormone (LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean +/- s.d.: 64.8 +/- 10.0 ng mL(-1), 41.3 +/- 3.7 ng mL(-1) and 24.6 +/- 9.0 ng mL(-1), respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2+/- caused a significant decrease in progesterone (P4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P4 concentrations than non-pregnant animals. Overall, 21 animals conceived (seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P4 concentration along with a delayed P4 increase should be considered as a causative factor for inability to conceive.

EFFECTS OF MELATONIN TREATMENT ON FOLLICULAR DEVELOPMENT AND OOCYTE QUALITY IN CHIOS EWES - SHORT COMMUNICATION

Follicular development and oocyte quality were assessed by laparoscopic observation and in vitro fertilisation, respectively, in melatonin-treated (Group M) and control (Group C) anoestrous Chios ewes (n = 10 in each group). Fourteen days after melatonin insertion, all ewes had laparoscopic evaluation of the follicular population followed by oocyte pick-up (OPU); on day 22 intravaginal progestagen sponges were inserted for 14 days. Two days after sponge removal the follicular population was re-evaluated and a second follicular aspiration was performed. Collected oocytes from the second OPU underwent in vitro maturation, fertilisation and culture. The number of large follicles was higher in Group M than in the control ewes during the first OPU and tended to be so (P = 0.06) at the second. Morphologically, oocytes collected from controls were of better quality than those from Group M; however, more oocytes collected from melatonintreated animals fertilised and developed in vitro . These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.

Ultrasonographic findings in the ovine udder during involution.

The objective of the study was to record, by means of ultrasonographic examination, changes occurring in the udder of ewes during involution and to compare differences between progressive or abrupt udder drying-off. In group A ewes, udder drying-off took place progressively during a period of 22 d; ewes were milked twice daily for the last time on day(D) 0; then, they were hand-milked once daily for a week (D1-D7), which was followed by another week during which ewes were hand-milked once every 2 d (D9, D11, D13), followed by a third week during which ewes were hand-milked once every 3 d (D16, D19, D22). In group B ewes, the procedure took place abruptly; ewes were milked twice daily for the last time on D0 and no milking was carried out after that. B-mode and Doppler ultrasonographic examination of the udder of all ewes was performed throughout the drying-off procedure. Appropriate data management and analysis were performed. Progressive changes of the various parameters evaluated throughout the study period were significant in both groups (P<0.005). Gray-scale results of mammary parenchyma progressively decreased during the study and differed significantly between group A and group B (P=0.049). A temporary increase in cistern volume was evident after cessation of lactation, but differences were not significant between the two groups (P>0.3). Diameter of the external pudendal artery progressively decreased during the study and differed significantly between the two groups (P=0.037). Both resistance index and pulsatility index progressively increased throughout the study period in both groups; for both parameters, differences between the two groups were significant (P<0.0005). B-mode ultrasonographic examination indicated differences in remodelling of the extracellular matrix in relation to the procedure for udder drying-off. Volume of the gland cistern did not appear to be affected by the procedure for udder drying-off. Doppler ultrasonographic examination confirmed that blood flow during initiated involution was lower than during a progressive procedure for drying-off.

Ultrasonographic findings in the ovine udder during lactogenesis in healthy ewes or ewes with pregnancy toxaemia.

Objective of the study was to record, by means of ultrasonographic examination, changes occurring during lactogenesis in the udder of healthy ewes and of ewes with pregnancy toxaemia. The work was carried out in 28 ewes, 16 with pregnancy toxaemia (group A) and 12 healthy controls (group B). B-mode and Doppler ultrasonographic examination of the udder of ewes was performed. During the last month of pregnancy, grey-scale intensity values of mammary parenchyma in group A were significantly greater than in group B (P = 0.007), as was also the progressive increase in grey-scale intensity values in both groups (P < 0.001). Blood mammary input was significantly greater in ewes of group B than in ewes of group A (P < 0.05), as was also the progressive increase in blood input in both groups (P < 0.001). Further, differences between the two groups were identified in pulsatility index (P = 0.007) and in mean blood velocity (P = 0.036), but only during the last fortnight of pregnancy. After lambing, grey-scale values decreased sharply compared to those in pregnancy (P < 0.01), whilst blood input, pulsatility index and mean blood velocity continued the same trend as at the last stage of pregnancy, with differences between the two groups still prevalent (P < 0.05). There was a reverse correlation between grey-scale intensity values and milk quantities (P < 0.035) and a correlation between blood input and milk quantities (P < 0.07). The progressive increase in the diameter of the external pudendal artery was significant (P < 0.001), but no significant differences were evident between the two groups (P > 0.35). Differences between group A and group B in all other haemodynamic parameters studied were not significant, neither throughout the last month of pregnancy (P > 0.25), nor during the first week of lactation (P > 0.06). However, their progressive changes during the last month of pregnancy were significant (P < 0.02).

Combined treatment of eCG and a non-selective inhibitor of phosphodiesterases for enhancing reproductive performance in ewes

The aim of this study was to evaluate the effect of the non-selective phosphodiesterase inhibitor 3isobutyl-1-methyl-xanthine (IBMX) given concomitantly with eCG on reproductive performance of ewes. In trial 1, eighty ewes were allocated into 8 groups (AC, A1, A2, A3 and DC, D1, D2, D3). Oestruses were synchronized by progestagen sponges. At sponges removal all ewes of A groups received 400 IU of eCG. Concomitantly with eCG, ewes of groups A1, A2 or A3 received IMBX at the dose of 2.5, 5.0 or 25.0 mg, respectively. Ewes of D1, D2 or D3 groups received only IBMX at the same doses, respectively; in each case, ewes of AC or DC groups were controls (C). In trial 2, one hundred eighteen ewes were allocated into 4 groups (BC1, B1 and BC2, B2). Oestruses were synchronized by progestagen sponges. At sponges removal ewes of BC1 or B1 received 200 IU of eCG, while ewes of BC2 or B2 groups received 100 IU. At the same time only ewes of B1 or B2 groups received 2.5 mg IBMX. In both trials, 48 hours after hormonal treatment, ewes were mated. In trial 1, pregnancy or lambing rate did not differ among A or D groups (P > 0.05). Total lambs per ewe were significantly higher in A1 compared to AC, A2, A3 or D1 groups (P < 0.05), but did not differ among D groups (P > 0.05). In trial 2, pregnancy or lambing rate did not differ among B groups (P > 0.05). Total lambs per ewe were significantly higher (P < 0.05) in B1 and B2 compared to BC1 and BC2 groups, respectively. These results indicate that IBMX combined with eCG at the end of an oestrus synchronization treatment improves litter size probably by increasing ovulation rate in ewes. This latter effect seems to be mainly dependent on the amount of gonadotrophins used.