Daniel Cavestany

Effect of prepartum diet on postpartum ovarian activity in Holstein cows in a pasture-based dairy system.

The hypothesis was that supplementation during the late prepartum period will differentially affect reproductive and productive variables according to parity. Primiparous (n=22) and multiparous (n=22) pregnant autumn calving Holstein cows were stratified in two groups according to parity (primiparous or multiparous) and within each group were randomly assigned to two treatments: (a) low supplemented (LS) or (b) high supplemented (HS) prepartum diet. The LS group was offered 5.2 kg/cow/day (DM basis) of wheat silage, and the HS group 4.7 kg cow/day (DM basis)/of corn silage and 3.6 kg (DM basis) of wheat bran+12 g of urea. Both groups grazed on natural pastures. After calving, all cows received the same diet. The experimental period was from 3 weeks before calving to 7 weeks postpartum (PP); body condition score (BCS) and blood samples for hormonal analyses were obtained weekly and ovarian ultrasonography was conducted three times per week. The loss in BCS around calving was less pronounced in HS cows, but only multiparous supplemented cows maintained BCS throughout the study. Non-esterified fatty acids (NEFA) increased during the prepartum period in the LS but not in the HS cows, with peak values occurring on day 14 PP in all groups. During the remainder of the experiment NEFA was greater in LS than in HS cows. Prepartum treatment did not affect the proportion of cows that had ovulations from the first dominant follicle postpartum, but decreased the interval to first ovulation in multiparous cows (22.9 compared with 38.2 days; P<0.05). This was associated with greater plasma IGF-I concentrations at the time the dominant follicle of the first follicular wave reached its maximum diameter (8.0 compared with 3.6 nmol/L; P<0.05). However, prepartum treatment had no effect on onset of ovarian activity in primiparous cows. Supplementation had no effect on milk production or milk protein percentage but increased milk fat percentage. We conclude that feeding a high-supplemented prepartum diet to multiparous cows allowed them to maintain BCS around calving, and this was associated with greater concentrations of IGF-I and an earlier onset of estrous cycles after calving.

Effect of dietary supplementation with fish oil during the transition period on milk production, plasma metabolites and postpartum anoestrus interval in grazing dairy cows

Inclusion of fish oil (FO) in the diet of dairy cows could improve the energy status and milk yield and reduce the interval from calving to first postpartum ovulation, but the effects may differ depending on the specific period of supplementation. To test these hypotheses, 28 pregnant Holstein heifers were randomly assigned to four treatments in a 2 × 2 factorial design: prepartum oral drench of FO (0 or 140 g/cow.day) for 21 days before calving, and/or postpartum oral drench of FO (0 or 190 g/cow.day) for 21 days after calving. Prepartum, heifers grazed in native pastures with supplements of wheat silage and wheat bran, while postpartum, cows grazed on improved pastures with addition of concentrates and corn silage. No interaction between prepartum and postpartum FO was detected for any variable analysed. Prepartum and postpartum total DM intake, milk yield, protein yield and percentage were not different among treatments. Milk fat percentage (3.83 versus 3.34 ± 0.10%) and yield (0.88 versus 0.73 ± 0.04 kg/day) decreased with postpartum FO but were not affected by prepartum FO. Prepartum and postpartum body condition score and plasma concentration of non-esterified fatty acids and cholesterol were not different among treatments, but urea concentration was higher in cows drenched with FO during prepartum (5.91 versus 4.64 ± 0.35 mM). Proportion of cows that ovulated the dominant follicle of the first postpartum wave and days to first postpartum ovulation, as determined by ovarian ultrasonography, were not affected by drenching with FO, but size of the dominant follicle in the first wave was decreased when FO was drenched only during the pre- or postpartum period compared with drenching in both periods. Dietary supplementation with FO during the postpartum period affected milk fat synthesis but more research is needed to establish its effects on resumption of ovarian activity in grazing dairy cows.

Endometrial expression of leptin receptor and members of the growth hormone—Insulin-like growth factor system throughout the estrous cycle in heifers

The growth hormone (GH)-insulin-like growth factor (IGF) system is expressed in bovine uterus during the estrous cycle and early pregnancy and is acknowledged to play an important role in regulating the development of the embryo and uterus. The leptin receptor (LEPR) is also expressed in the bovine uterus although it is not known whether its expression varies during the estrous cycle. In this study, the expression of the IGF-I and -II, the type 1 IGF receptor (IGF-1R), GH receptor (GHR) and LEPR transcripts was determined on endometrial transcervical biopsies collected on days 0 (estrus), 5, 12 and 19 of the cow estrous cycle (n=8). The expression of mRNA was determined by RT real time PCR using ribosomal protein L19 as a housekeeping gene. It has been demonstrated for the first time that LEPR mRNA is expressed in the bovine uterus throughout the estrous cycle and that it presents a cycle-dependent variation, with higher levels observed during the luteal phase. The expression of IGF-I mRNA was greatest at estrus and day 5 (100%), and decreased on days 12 and 19 to 47% and 35% of the initial values. IGF-II mRNA increased on day 12 and decreased sharply thereafter (to one-third of day 12 values). Interestingly, IGF-1R showed the same pattern as IGF-II: increased 50% on day 12 compared to values at estrus and presented a sharp decrease on day 19. The expression of GHR transcript was greatest at estrus and on day 5 and progressively decreased thereafter. These results show that the GH-IGF system components are distinctively regulated during the estrous cycle suggesting that modulation of the IGF system may influence uterine activity during this period. The increase in the uterine sensitivity to IGFs during the late luteal phase - as demonstrated by the increased IGF-1R expression - concomitant with the increased IGF-II mRNA expression may reinforce the role of IGF-II during early pregnancy. Moreover, leptin is also likely to play roles during early embryo development.

Use of medroxyprogesterone acetate (MAP) in lactating Holstein cows within an Ovsynch protocol: follicular growth and hormonal patterns

To evaluate the effects of incorporating medroxyprogesterone acetate (MAP) in an Ovsynch protocol, cyclic lactating dairy cows were assigned randomly to two groups (control and MAP, n=8 each). Ovsynch treatment (Day 0: GnRH, Day 7: PG, Day 9: GnRH) was initiated at random stages of the estrous cycle (control) and an intravaginal polyurethane sponge impregnated with 300mg of MAP was inserted intravaginally in the MAP group at Day 0 and removed at Day 7 of the Ovsynch protocol (MAP treatment). Ovaries were scanned daily from Day 0 until the second GnRH treatment on Day 9 and from then every 6h for 36 h. Milk samples were collected three times weekly starting 17 days before the initiation of treatment to determine the stage of the cycle at the beginning of the Ovsynch protocol. Blood samples were collected to monitor estradiol (E2), progesterone (P4), LH, and 15-ketodihydro-PGF(2alpha) (PGFM) by RIA. Response to the first GnRH treatment varied with the stage of the cycle at the time of initiation of treatment, as cows in metestrous and late diestrous did not ovulate. In cows ovulating, growth rate of the new follicle was not affected by the addition of MAP. No treatment differences were found in E2 concentrations which reached a maximum at Day 9, consistent with the maximum follicular size. At Day 7, cows with luteal concentrations of P4 had increased concentrations of PGFM, but cows with basal P4 did not show an active release of prostaglandins. There were no treatment differences in the ovulatory response to the second GnRH-induced ovulation, with 11 of the 16 cows ovulating between 16 and 32 h. The addition of MAP to the Ovsynch protocol could not mimic the normal high progesterone levels needed to prevent premature ovulations in those cows with premature CL regression.

Oestrus synchronisation and fixed time artificial insemination in beef heifers

To compare two oestrus synchronisation protocols in beef heifers presynchronised with two prostaglandin F2α (PG) treatments, 36 h after the second PG treatment one group (hCG-OB group; n = 112) received 250 IU of hCG and 0.5 mg of oestradiol benzoate (OB) followed by fixed time artificial insemination (FTAI) 30 h later. Additional oestrus detection (OD) and artificial insemination (AI) was done in this group for 3 days after FTAI; heifers rebred during this period were considered open to the FTAI. The Control group (n = 112) received only OD and AI for 6 days after the second PG treatment. Follicular size was measured at the time of AI in a subsample of heifers (59 in the hCG-OB group and 34 in the Control group). Results were evaluated separately either considering heifers pregnant at FTAI or those pregnant at FTAI + 3-day OD + AI. The FTAI conception rate was 45.5 vs 76.5% for the Control group (P 0.1). In conclusion, acceptable synchronised conception rate and pregnancy rate were obtained by using this protocol, and the results were improved by complementing it with OD + AI for 3 days after FTAI.

Effect of side of the corpus luteum and pregnancy on estrogen and progesterone receptor expression and localization in the endometrium of mares

The effect of side of corpus luteum on uterine gene expression and protein localization of estrogen receptor α (ERα) and progesterone receptor (PR) in healthy cyclic and pregnant mares 13 days after ovulation (day 0) was investigated. Transcervical biopsies were performed to collect endometrium ipsilateral and contralateral regarding the side of corpus luteum on day 13 post-ovulation in cyclic (n = 6) and pregnant (n = 6) mares. Blood samples were collected daily from day 0 until the day of biopsy for 17β-estradiol (E2) and progesterone (P4) determinations. Receptor expression was determined by immunohistochemistry and transcript expression by real time RT-PCR. Serum E2 and P4 concentrations were not affected by reproductive status. The contralateral horn presented higher percentage of positive cells for ERα than the ipsilateral horn (P < .05), but side did not affect PR. ERα showed low staining and no main effect of pregnancy was found, but pregnant mares had lower protein expression of PR (19.8 vs. 40.4 ± 5.3%, P < .01). The contralateral horn tended to present higher expression of ERα mRNA (1.33 vs. 0.97 ± 0.17, P < .10) and PR mRNA (1.96 vs. 1.57 ± 0.52, P < .09). ERα mRNA relative expression was lower in the pregnant group (0.88 vs. 1.44 ± 0.19, P < .05). The interaction of reproductive status and side of corpus luteum tended to affect PR mRNA expression as pregnant mares had a lower PR mRNA content in the ipsilateral horn than cyclic mares. To our knowledge, this is the first study that describes the behavior of steroid receptors in the endometrium of mares regarding side of corpus luteum.

Endocrinología metabólica en la vaca lechera durante el período de transición y su relación con el reinicio de la ciclicidad ovárica

La produccion de leche se ha duplicado en las ultimas decadas y concomitantemente el desempeno reproductivo ha disminuido. Las limitantes reproductivas son el reinicio de la ciclicidad ovarica luego del parto y la mortalidad embrionaria temprana. Esta revision resume algunos trabajos realizados en los ultimos 10 anos respecto de los cambios metabolicos y endocrinos durante el periparto y su relacion con el reinicio de la ciclicidad ovarica en vacas lecheras en nuestro pais. Hemos caracterizado estos cambios en vacas primiparas y multiparas durante el periodo de transicion. Se realizaron estudios con dietas diferenciales en energia y proteina en el pre y postparto con el objetivo de modificar el comportamiento productivo y reproductivo, determinandose en ellos hormonas y metabolitos. Los autores concluyen que los indicadores endocrinos y metabolicos son buenas herramientas de diagnostico que integran la memoria metabolica y el estado nutricional reciente, siendo esenciales para comprender como el eje reproductivo es informado respecto del balance energetico negativo que ocurre en este periodo.

Effect of Pregnancy on Endometrial Sex Steroid Receptors and on Prostaglandin F2α Release after Uterine Biopsy in Heifers

The effect of pregnancy on oestrogen receptor (ER) and progesterone receptor (PR) endometrial expression in heifers was studied. Holstein heifers were not inseminated (controls, n = 8) or inseminated (n = 21). Endometrial biopsies were taken at Day 17 from the uterine horn ipsilateral to the corpus luteum. Hourly samples were taken on the day of the biopsy in 12 animals (controls = 4 and inseminated = 8) to analyze 15-ketodihydro-PGF2α (PGFM) and progesterone concentrations. Pregnancy determined by ultrasonography diagnosed 6 pregnant cows. The uterine biopsy increased PGFM concentrations, which remained high for 2 to 4 hours, followed by a transient decrease in progesterone concentrations, but the procedure neither provoked luteolysis nor blocked pregnancy. PGFM concentrations were higher in cyclic than in pregnant cows. No differences in PR mRNA expression were observed among groups, but ER mRNA in pregnant heifers tended to be lower than controls, suggesting that this pathway is implicated in maintenance of pregnancy.