Gene Expression in Embryos From Norwegian Red Bulls With High or Low Non Return Rate: An RNA-Seq Study of in vivo-Produced Single Embryos

During the last decade, paternal effects on embryo development have been found to have greater importance than previously believed. In domestic cattle, embryo mortality is an issue of concern, causing huge economical losses for the dairy cattle industry. In attempts to reveal the paternal influence on embryo death, recent approaches have used transcriptome profiling of the embryo to find genes and pathways affected by different phenotypes in the bull. For practical and economic reasons, most such studies have used in vitro produced embryos. The aim of the present study was to investigate the differences in the global transcriptome of in vivo produced embryos, derived from sires with either high or low field fertility measured as the non-return rate (NRR) on day 56 after first AI of the inseminated cows. Superovulated heifers (n = 14) in the age span of 12–15 months were artificially inseminated with semen from either high fertility (n = 6) or low fertility (n = 6) bulls. On day seven after insemination, embryos were retrieved through uterine flushing. Embryos with first grade quality and IETS stage 5 (early blastocyst), 6 (blastocyst) or 7 (expanded blastocyst) were selected for further processing. In total, RNA extracted from 24 embryos was sequenced using Illumina sequencing, followed by differential expression analysis and gene set enrichment analysis. We found 62 genes differentially expressed between the two groups (adj.p-value<0.05), of which several genes and their linked pathways could explain the different developmental capacity. Transcripts highly expressed in the embryos from low fertility bulls were related to sterol metabolism and terpenoid backbone synthesis, while transcripts highly expressed in the high fertility embryos were linked to anti-apoptosis and the regulation of cytokine signaling. The leukocyte transendothelial migration and insulin signaling pathways were associated with enrichments in both groups. We also found some highly expressed transcripts in both groups which can be considered as new candidates in the regulation of embryo development. The present study is an important step in defining the paternal influence in embryonic development. Our results suggest that the sire’s genetic contribution affects several important processes linked to pre-and peri implantation regulation in the developing embryo.

Reproductive Performance and Culling Rate of Purebred Holstein Cows and Their Crosses With Fleckvieh and Brown Swiss Cows Under Subtropical Conditions

This study aimed to elucidate the reproductive performance of purebred Holstein (HO) cows with their crosses with Fleckvieh (FV) and Brown Swiss (BS) cows under subtropical conditions. A total of 677 cows [487 HO, 104 HO × FV (HFV); 50% FV and 50% HO and 86 HO × BS (HB); 50% BS and 50% HO] were enrolled in this study. Pure HO cows had significantly greater service per conception (S/C; 3.69), days open (147.9 days), and calving interval (449.6 days), than the HFV (2.89, 116.7, and 407.4 days, respectively) and HB (3.07, 134.3, and 434.2 days, respectively) crossbred cows. At day 28, the conception percentage was significantly greater among HFV crossbred cows vs. pure HO cows [crude odds ratios (COR) = 2.16], but embryonic loss, abortion percentage, calving difficulty, and retained placenta percentage were similar (p > 0.05) among pure HO cows and their crosses. HFV crossbreds had significantly lower incidence of endometritis (COR = 0.70, p = 0.035), mastitis (COR = 0.69, p = 0.015), and ketosis (COR = 0.53, p = 0.004) vs. other cows. HB and pure HO cows had a similar incidence of mastitis, lameness, and ketosis (COR = 0.76, 0.75, and 0.81; p = 0.223, 0.468, and 0.492, respectively). HFV crossbred cows had a lower risk of culling rate than HB crossbred cows. In summary, HFV cows demonstrated the best reproductive performance in terms of S/C, days open, calving interval, conception at 28 days, mastitis percentage, ketosis percentage, and endometritis.

Investigating the genetic architecture of conception and non-return rates in Holstein cattle under heat stress conditions

This study aimed to investigate the genetic variability of conception rate (CR) and non-return rate (NR) in Iranian dairy cows under heat stress conditions. A total of 34,304 records of CR, and NR at 45 days (NR45) and 90 days (NR90) after the first insemination, from 21,405 Holstein cows were included in this study. The weather records were obtained from seven meteorological stations located at a distance of less than 70 km from the farms. Temperature-Humidity Index (THI) was determined for each record on the insemination day. The statistical models for CR, NR45, and NR90 included the fixed effects of herd-year-season, parity, milk yield, and THI. Genetic components were estimated using an animal model and fitting random regression models on THI based on the Bayesian method. Results showed similar decreasing trends for CR, NR45, and NR90 when increasing the THI levels. The additive genetic variance of heat tolerance for CR, NR45, and NR90 were 0.008 ± 0.0004, 0.0262 ± 0.007, and 0.0254 ± 0.006, respectively. The additive genetic variance of heat tolerance increased directly with THI, and therefore, our findings indicate that a combined selection using heat tolerance can be considered for genetic evaluation of reproduction traits under heat stress conditions.

Reproductive performance of Brown Swiss, Holstein and their crosses under subtropical environmental conditions

Selection has been emphasized for increasing production traits with ignoring the fertility traits, which leads to a general loss of reproductive fitness. The aim of this study was to evaluate the reproductive performance of the pure Brown Swiss (BS), Holstein (HO), their first-generation crossbred (F1), and backcross (BC) cows under subtropical Egyptian conditions. The reproductive performance and health traits were measured in the pure BS, HO, their F1, and BC crossbred, in addition to investigating the impact of temperature-humidity index level (THI) on reproductive traits. Brown Swiss and her F1 had a better reproductive efficiency and health traits than in HO and BC. They possess a higher conception (34.1% and 36.9%, respectively) and pregnancy rates (32.8% and 31.1%, respectively), a shorter calving interval (401 and 420 days, respectively), and a lower average insemination per parturition (3.18 and 3.45, respectively), with a lower incidence of metritis (14.1% and 14.6%, respectively). Moreover, no difference has been detected in the fertility of BS with different THI levels, whereas F1 was slightly affected by increasing THI, especially for conception rate which declined from 43.1% at low to 24.1% at high THI. But the pregnancy rate did not change with different levels of THI. Our results indicate that BS and her F1 have a better reproductive performance and adaptability than pure HO and BC under subtropical Egyptian conditions. Furthermore, milk yield of the F1 crossbred is comparable to that of the pure HO cows.