Bulls fed a high-gain diet decrease blastocyst formation after in vitro fertilization.

In brief: Paternal high-gain diet reduces blastocyst development following in vitro fertilization and embryo culture but does not affect gene expression or cellular allocation of resultant blastocysts. Abstract: Bulls used in cattle production are often overfed to induce rapid growth, early puberty, and increase sale price. While the negative consequences of undernutrition on bull sperm quality are known, it is unclear how a high-gain diet influences embryo development. We hypothesized that semen collected from bulls fed a high-gain diet would have a reduced capacity to produce blastocysts following in vitro fertilization. Eight mature bulls were stratified by body weight and fed the same diet for 67 days at either a maintenance level (0.5% body weight per day; n = 4) or a high-gain rate (1.25% body weight per day; n = 4). Semen was collected by electroejaculation at the end of the feeding regimen and subjected to sperm analysis, frozen, and used for in vitro fertilization. The high-gain diet increased body weight, average daily gain, and subcutaneous fat thickness compared to the maintenance diet. Sperm of high-gain bulls tended to have increased early necrosis and had increased post-thaw acrosome damage compared with maintenance bulls, but diet did not affect sperm motility or morphology. Semen of high-gain bulls reduced the percentage of cleaved oocytes that developed to blastocyst stage embryos. Paternal diet had no effect on the number of total or CDX2-positive cells of blastocysts, or blastocysts gene expression for markers associated with developmental capacity. Feeding bulls a high-gain diet did not affect sperm morphology or motility, but increased adiposity and reduced the ability of sperm to generate blastocyst-stage embryos.

Evaluating the use of luteal color Doppler ultrasonography and pregnancy-associated glycoproteins to diagnose pregnancy and predict pregnancy loss in Bos taurus beef replacement heifers.

The objective of this study was to evaluate the use of corpus luteum (CL) color Doppler (CD) ultrasonography and pregnancy-associated glycoproteins (PAG) for early pregnancy diagnosis and examine their ability to predict late embryonic/early fetal mortality (LEM) in Bos taurus beef replacement heifers. Beef heifers (n = 178) were exposed to a 7-d CO-Synch + CIDR protocol followed by fixed-time artificial insemination (day 0). On days 20 and 22, B-mode and CD ultrasonography were performed to evaluate CL morphometries and blood perfusion, respectively. Heifers were considered nonpregnant when CL area was <2 cm2 or estimated luteal blood perfusion was ≤30% of the total luteal area. Blood samples were collected on days 25 and 29 to estimate circulating concentrations of PAG. Conventional ultrasonography on days 29 and 94 was utilized to determine pregnancy status and considered the gold standard method for pregnancy diagnosis. Pregnant heifers had greater (P < 0.01) CL diameter, area, volume, and blood perfusion when compared with nonpregnant heifers on days 20 and 22. Accuracy of CD on days 20 and 22, and PAG on days 25 and 29 were 91%, 94%, 96%, and 98%, respectively. No false-negative results were observed for CD on both days 20 and 22 (negative predicted value = 100%) and false-positive results represented 8% and 6% of the diagnoses. Heifers that experienced LEM between days 29 and 94 of gestation had decreased luteal (P = 0.02) volume on day 20 and tended (P = 0.07) to have decreased concentrations of PAG on day 29 compared with heifers that maintained pregnancy. However, both CD and PAG failed to predict embryonic mortality. In conclusion, CD successfully detected most nonpregnant replacement heifers as early as day 20 of gestation, while resulting in no false negative diagnoses. Both CD and PAG failed to predict LEM in the present study.

Identifying nonpregnant females early after breeding allows cattle producers to rapidly rebreed females that failed to conceive after their first artificial insemination and consequently increases reproductive efficiency. Additionally, embryonic and fetal mortality during early gestation are the main drivers of pregnancy failure and represents a significant economic burden to both the beef and dairy industries. This study evaluated the use of color Doppler (CD) ultrasonography of specific ovarian structures and blood concentrations of pregnancy-associated glycoproteins (PAG) as potential methods to diagnose pregnancy earlier than industry-standard techniques. Moreover, the present study investigated the use of CD and blood PAG as predictor of pregnancy loss. Data generated here indicates that CD and blood PAG can accurately detect pregnancy as early as 20 and 25 d after insemination, respectively. In the present study, heifers that experienced pregnancy loss between days 29 and 94 of gestation tended to have decreased plasma concentrations of PAG during early pregnancy. Heifers experiencing pregnancy loss between days 29 and 94 of gestation were also more likely to have a luteal cavity on day 20 of gestation and had decreased luteal volume on the same day. However, results reported herein indicate that both CD and blood concentrations of PAG failed to predict pregnancy loss in replacement heifers.