PSI-7 Comparison of 6-day versus 7-day CIDR protocol with GnRH and PGFα to synchronize crossbred beef cows for fixed-timed ai with sexed semen at two different times

Preliminary data indicate that shortening the progesterone exposure with CIDR can improve conception rates compared to the established 7-day CO-Synch protocols. The objective was to determine the effects of shortening progesterone exposure from 7 days to 6 days among crossbred beef cows and fixed-time artificial insemination (FTAI) with sex-sorted semen. A total of 147 fall calving (September-November) crossbred beef cows from one location were randomized to one of four treatments: 1 and 4) 7-d CO-Synch + CIDR protocol with administration of gonadotropin-releasing hormone (GnRH) and a CIDR insert on day 0, prostaglandin F2α (PGF) at CIDR removal on day 7, and FTAI occurring 66 h (Treatment 1) or 74 h (Treatment 4) later; 2 and 3) 6-d CO-Synch + CIDR protocol with administration of GnRH and CIDR insert on day 0, prostaglandin F2α (PGF) at CIDR removal on day 6, and FTAI occurring 72 h (Treatment 2) or 80 h (Treatment 3) later. Sex-sorted semen from Angus sires was used for AI. Pregnancy was determined by ultrasound 40 days after AI. Pregnancy rate was analyzed using the MIXED procedure of SAS with CIDR and AI service time as fixed effects. Chi-square analysis was used to assess the number of pregnant and open cows in each treatment using the FREQ procedure of SAS. There was no difference (P = 0.78) in pregnancy rates between 6-d CIDR (0.59 ± 0.05%) and 7 d CIDR (0.57 ± 0.05%) protocols. Cattle bred a shorter period after CIDR removal (0.64 ± 0.05%) had numerically (P = 0.11) greater pregnancy rates compared to those with a longer period after CIDR removal (0.51 ± 0.05%). There was no difference in the number of pregnant and open cows between treatment groups. These data suggest that using a 6-day or 7-day protocol, regardless of breeding time, results in similar conception rates.

Impact of heat stress on embryonic development during first 16 days of gestation in dairy cows

Objective was to elucidate the effects of heat stress (HS) on embryo development during first 16 gestational days (GD) and circulating hormone concentrations on GD-16 in lactating Holstein cows. Cows in HS and control (CON) groups were exposed to temperature humidity index (THI) of ≥ 73 and < 73, respectively, for 3 weeks before the experiment. GD-7 (67 vs 49%) and GD-16 (52 vs. 31%) conception rates following single insemination were greater (P < 0.01) for CON compared with HS cows. Control cows produced more GD-7 transferrable embryos following superovulation compared with HS cows (84.8 vs 53.1%; P < 0.001). Mean (± SEM) length (45.2 ± 10.6 vs. 59.2 ± 9.1 mm) and weight (31.4 ± 4.3 vs. 42.4 ± 6.2 mg) of GD-16 conceptus were greater for CON compared with HS cows (P < 0.05). Control cows yielded more filamentous conceptus (≥ 25 mm) compared with HS cows (71 vs 45%; P < 0.05). Progesterone (2.09-fold) was higher, and cortisol (1.86-fold), prolactin (1.60-fold), substance-P (1.55-fold), Isoprostane-8 (1.34-fold) and prostaglandin F metabolites (1.97-fold) were lower in CON compared with HS cows (P < 0.05). Progesterone positively, and substance-P, isoprostane-8 and the THI negatively were associated with GD-16 conceptus length (P < 0.05). In conclusion, altered hormones concentrations in heat-stressed cows plausibly resulted in lower GD-7 and GD-16 conception rates, fewer GD-7 transferable embryos, and stunted GD-16 conceptus elongation.

The use of fixed time artificial insemination programmes for the use of sexed semen in block calving dairy heifers

In seasonal block calving herds reproductive efficiency can have a significant impact on productivity and profitability. Within this it is key that the nulliparous heifers calve down promptly in the block, and if these heifers can have heifer calves it will expediate genetic gain. There is extensive research into the conception rates of differing protocols and the literature is reviewed to support the choice of protocol used in the subsequent case study. The case study uses a 6-day progesterone protocol with two injections of prostaglandin F2α and sexed semen; it demonstrated acceptable conception rates as well as the variability that can occur between different bulls' semen straws. Finally, the case study assesses the costs and benefits of the synchronisation programme and concludes a cost benefit of £88.55 per heifer.

Impacts of heifer post-weaning residual feed intake classification on reproductive and performance measurements of first, second and third parity Angus beef females

This study evaluated heifer post-weaning residual feed intake (RFI) classification on reproductive and performance measurements of first, second and third parity Angus beef females. We analyzed the annual, as well as, cumulative production of 347 Angus females from birth through weaning of their 3 rd calf. Heifer post-weaning RFI was calculated as the actual dry matter intake minus the predicted dry matter intake based on the average daily gain of the contemporary group on an annual basis. Heifers were categorized based on RFI as either low (&lt; -0.50 SD from mean), average (± 0.50 SD from mean), or high (&gt; +0.50 SD from the mean) within year. There was no RFI × Parity interaction (P ≥ 0.14) observed for all production/reproduction traits except for conception rates (P =0.02). Julian birth date of cows was influenced by RFI classification (P &lt; 0.01) and displayed a quadratic (P = 0.02) effect with high RFI cows being born earlier in the calving season than average RFI cows (71.2 vs 75.3 days), but did not differ from low RFI cows (74.0 vs 75.3 days). Cow birth weight, weaning weight, as well as, all other cow weight and body condition measurements were not influenced by RFI classification (P ≥ 0.14). As expected, there was a linear increase in cow body weight at weaning with increasing parity (P &lt; 0.01). Cow RFI classification had no influence on progeny weaning weight, birth date, calving interval, or postpartum interval (P ≥ 0.15). Calf birth weights displayed a quadratic parity effect (P &lt; 0.01) with 1 st calf heifers having calves with lower birth weights than 2 nd and 3 rd parity calves. Calf 205 day adjusted weaning weights displayed a quadratic effect (P = 0.01) with 1 st calf heifers weaning lighter calves than 2 nd and 3 rd parity cows. Weaning weight ratio displayed a linear decrease with increasing parity (P &lt; 0.01). Cow conception probability displayed a linear tendency for pregnancy 2 (P = 0.09), and a quadratic tendency for pregnancy 4 (P = 0.07) as a function of RFI classification, but no effects were observed for pregnancy 1 and 3. Cow artificial insemination (AI) conception rates differed by year of pregnancy (P &lt; 0.01) but not RFI classification (P = 0.81). In summary, heifer post-weaning RFI classification had minimal effects on beef cattle production and reproductive efficiency.

Effect of Season and Social Environment on Semen Quality and Endocrine Profiles of Three Endangered Ungulates (Gazella cuvieri, G. dorcas and Nanger dama)

Knowledge of factors affecting semen quality could be of great importance for the collection and preservation of semen from threatened animals. To assess the effect of seasonality, sperm parameters and testosterone levels were examined throughout the year and compared with the distribution of conceptions. Cuvier’s gazelle showed higher sperm quantity in April, coinciding with one peak of conceptions. In dorcas gazelle, sperm parameters showed a drop in October. However, percentage of conceptions increased during that month. In Mohor gazelle, sperm quality was best in April and August, in agreement with higher conception rates and high testosterone levels. Percentage of conceptions was correlated with photoperiod and rainfall in Cuvier’s gazelle and with temperature in Mohor gazelle. To assess the effect of social environment, semen quality, testosterone and cortisol levels were quantified in males housed alone, in bachelor groups or with females. No differences were seen in Cuvier’s and Mohor gazelles’ semen traits, whereas dorcas males housed with females showed lower semen quality than males kept alone or with other males. Overall, ejaculate quality is influenced by seasonal factors in the three gazelle species, while social factors only appear to affect that of dorcas gazelle.

Temperature, climate change, and human conception rates: evidence from Hungary

In this paper, we examine the relationship between temperature and human conception rates and project the impacts of climate change by the mid-twenty-first century. Using complete administrative data on 6.8 million pregnancies between 1980 and 2015 in Hungary, we show that exposure to hot temperatures reduces the conception rate in the first few weeks following exposure, but a partial rebound is observed after that. We project that with absent adaptation, climate change will increase seasonal differences in conception rates and annual conception rates will decline. A change in the number of induced abortions and spontaneous fetal losses drives the decline in conception rates. The number of live births is unaffected. However, some newborns will experience a shift in the timing of conception that leads to changes in in utero temperature exposure and therefore might have further consequences.