The aim of this study was to evaluate the effect of (i) the duration of hormone treatment with progestogen sponges during the seasonal anestrus and (ii) the administration of two doses of prostaglandin at 7 days apart during the breeding season on reproductive parameters of Santa Inês ewes. In experiment 1, 32 ewes received intravaginal MAP sponges for 6 (G6 days), 9 (G9 days), or 12 (G12days) days and 75 μg D-cloprostenol i.m. and 300 IU eCG i.m. 1 day before sponge removal. In experiment 2, 23 ewes received two doses of 0.48-mg sodium cloprostenol i.m. 7 days apart. Ovarian follicular dynamic was assessed through transrectal ultrasonography. Blood samples were collected daily to determine progesterone concentrations. In experiment 1, estrus and ovulation rates did not differ (P > 0.05) among protocols and between cyclic and acyclic ewes at the beginning of the experiment. The G9 days treatment showed a lower dispersion of ovulations in relation to onset of estrus when compared to G6 days and G12 days. In experiment 2, all ewes exhibit estrus and ovulated after the second dose of prostaglandin, although ewes that were in diestrus at D0 showed subluteal concentrations of progesterone during the follicle development stage of the treatment. In conclusion, the use of progestogen device during 9 days promotes lower dispersion of ovulation when compared to its use for 6 or 12 days, and the protocol of two doses of prostaglandin 7 days apart synchronizes estrus efficiently but results in follicular development under low progesterone concentrations.

Progesterone regulates the endometrium to support pregnancy establishment and maintenance. In the ruminant, one action of progesterone early in pregnancy is to alter embryonic development and hasten the process of trophoblast elongation around day 14–15 of pregnancy, which is required for maternal recognition of pregnancy. Here we demonstrate that the WNT antagonist DKK1, whose expression is increased by progesterone treatment, can act on the bovine embryo during day 5 to 7.5 of development (the morula to blastocyst stage) to promote embryonic elongation on day 15 of pregnancy. Embryos were produced in vitro and exposed to 0 or 100 ng/ml recombinant human DKK1 from day 5 to 7.5 of culture. Blastocysts were transferred into synchronized recipient cows on day 7.5 (n = 23 for control and 17 for DKK1). On day 15, cows were slaughtered and embryos recovered by flushing the uterus. Embryo recovery was n = 11 for controls (48% recovery) and n = 11 for DKK1 (65% recovery). Except for two DKK1 embryos, all embryos were filamentous. Treatment with DKK1 increased (P = 0.007) the length of filamentous embryos from 43.9 mm to 117.4 mm and the intrauterine content of the maternal recognition of pregnancy signal IFNT (P = 0.01) from 4.9 µg to 16.6 µg. Determination of differentially expressed genes (DEG), using the R environment, revealed 473 DEG at p < 0.05 but none at FDR < 0.05, suggesting that DKK1 did not strongly modify the embryo transcriptome at the time it was measured. However, samples clustered apart in a multidimensional scaling analyisis. Weighted gene co-expression analysis of the transcriptome of filamentous embryos revealed a subset of genes that were related to embryo length, with identification of a significant module of genes in the DKK1 group only. Thus, several of the differences between DKK1 and control groups in gene expression were due to differences in embryo length. In conclusion, DKK1 can act on the morula-to-blastocyst stage embryo to modify subsequent trophoblast elongation. Higher pregnancy rates associated with transfer of DKK1-treated embryos may be due in part to enhancements of trophoblast growth and antiluteolytic signaling through IFNT secretion. Given that progesterone can regulate both timing of trophoblast elongation and DKK1 expression, DKK1 may be a mediator of progesterone effects on embryonic development.

No abstract

The objective of this work was to evaluate the effect of reducing crude protein (CP) contents in diets with a constant metabolizable protein content on the intake, performance, nitrogen balance, and nutrient digestibility of lactating Holstein-Gyr cows. Animals (n = 24, 103±23 days in milk) were allocated to four treatments (n = 6 per group) with different CP contents: 127, 132, 139, and 156 g kg-1 dry matter (DM). DM intake was not affected by treatments. CP intake and digestibility increased linearly with higher CP contents. Milk yield (23.7±3 kg per day) and the percentages of milk protein (3.3±0.2%) and fat (3.8±0.5%) were not affected by CP reduction. Milk and blood urea nitrogen increased linearly with the increase of CP in the diet, similarly to urinary nitrogen excretion. Nitrogen use efficiency was 29.8 and 22.4% when CP was 127 and 156 g kg-1 DM, respectively. Reducing CP in diets fed to mid-lactating Holstein-Gyr cows increases nitrogen use efficiency and maintains the productive performance of the cows.

The present trial evaluated the effect of crossbred composition and Temperature and Humidity Index (THI) on vaginal temperature (VT) of Girolando dairy cows maintained under tropical pasture during warm seasons. The VT was monitored along 41 to 96 h in 615 Girolando cows with different Holstein (H) × Gir genetic composition (1/2 H = 284, 3/4 H = 248, and 7/8 H = 83) from six Brazilian farms in the summer of 2016 and 2017. VT of each cow at each hour of the day and the respective THI were averaged per hour across all monitoring days to generate an averaged value for VT and THI during 24 h. A linear mixed model with repeated measures using restricted maximum likelihood (REML) method for (co)variance components estimation procedure was employed. The final model adjusted the VT for the effects of cow, time, THI, farm, year, pregnancy status, body condition score (BCS), milk yield, genetic composition, and genetic composition*time interaction. Fixed effects were evaluated by ANOVA and tested with Tukey test in R software version 3.6.1 (R Core Team, 2019). Overall mean of VT, air temperature (AT), and THI were 39.06 ± 0.52 °C, 25.63 ± 0.40 °C, and 75.06 ± 3.96, respectively. VT had moderate positive correlation with THI (r² = 0.45, P &lt; 0.001) and AT (r² = 0.46, P &lt; 0.001). The VT had estimated linear increase of 0.05 °C for each THI unit increase (P &lt; 0.001). Least square mean of VT varied among the farms (P &lt; 0.001), pregnancy status (P &lt; 0.001), and BCS (P &lt; 0.05) but not for Milk yield (P &gt; 0.05). The daily average VT was affected by genetic composition (P &lt; 0.001) with highest temperature for 3/4 H (39.08 ± 0.06 °C a) and 7/8 H (39.09 ± 0.06 °C a) and lowest temperature for 1/2 H (38.95 ± 0.06 °C b). The difference of VT among the three crossbred groups varied in function of the time of the day, from 12:00 to 20:00 h (P &lt; 0.001), with 3/4 Holstein and 7/8 Holstein cows reaching similar VT, above to the upper limit 39.1 °C and higher than 1/2 Holstein cows during all this period. In conclusion, Girolando cows are sensitive to heat stress in tropical condition during warm seasons. Moreover, Girolando cows with genetic composition higher than 3/4 Holstein display reduced thermoregulatory efficiency. Therefore, Girolando cows in tropical dairy farms require strategies to mitigate heat stress according to their genetic composition.