Reproductive performance of lactating dairy cows after inducing ovulation using hCG in a five-day progesterone-based fixed-time AI protocol

Dietary Supplementation of Capsaicin Enhances Productive and Reproductive Efficiency of Chinese Crossbred Buffaloes in Low Breeding Season

The present study investigated the role of dietary capsaicin (CPS) supplementation on milk yield (liters/head) and milk composition (total solids, lactose, albumin, protein, fat, milk urea nitrogen (MUN), somatic cell count (SCC) and somatic cell score (SCS), serum metabolites (lipoprotein esterase (LPL) and aspartate aminotransferase (AST)), and reproductive physiology (follicular development, estrus response, ovulation and pregnancy) following synchronization during the low breeding season. One hundred (n = 100) crossbred buffaloes were randomly assigned to four dietary groups consisting of CPS supplementation dosages (0, 2, 4 or 6 mg/kg of total mixed ration; TMR) as CPS-0 (n = 26), CPS-2 (n = 22), CPS-4 (n = 25) and CPS-6 (n = 27), respectively, in a 30-day feed trial. The results revealed that the CPS-4 group of buffaloes had a better estrus rate (72%) along with improved (p < 0.05) ovulatory follicle diameter (13.8 mm), ovulation rate (68%) and pregnancy rate (48%) compared to other treatment groups. Milk yield improved (p < 0.05) in CPS-4 supplemented buffaloes after day 20 of the trial, comparatively. There was a significant effect (p < 0.05) of milk sampling day (day 30) on total milk solids, lactose, milk protein and MUN levels, whereas lactose, MUN, SCC and SCS were influenced by supplementation dosage (CPS-4). Glucose levels were affected in buffaloes by sampling time (artificial insemination (AI) and 50-day post-AI) and CPS-dose (CPS-4 and CPS-6), respectively. LPL level changed in CPS-2 and CPS-4 groups at AI time and 50 days after AI. In addition, the AST level was different in CPS-4 at AI time and 50 days after AI. Therefore, our data suggest that a medium dose (~4 mg/kg of TMR) of CPS provided a better response in the form of milk yield, milk composition, serum metabolites and reproductive performance in crossbred buffaloes during the low breeding season.

LRH-A3 and HCG increase pregnancy rate during timed artificial insemination in dairy cows

The objective of this study was to use luteinizing hormone-releasing hormone A3 (LRH-A3) and human chorionic gonadotrophin (HCG) to improve pregnancy rate of dairy cows during timed artificial insemination (TAI). In experiment 1, the TAI process (0 d, GnRH, 100 μg; 7 d, PGF2α, 0.4 mg; 56 hr, GnRH, 100 μg; 16 hr, AI) was applied to 160 dairy cows on 50th and 60th days after parturition respectively. In experiment 2, 320 postpartum dairy cows were treated with TAI (Group A), TAI + 25 μg LRH-A3 (Group B), TAI + 1,500 IU HCG 5 days after AI (Group C), and TAI + 25 μg LRH-A3 + 1,500 IU HCG 5 days after AI (Group D). In experiment 3, endometrial cells were treated with HCG. The results showed that TAI did not affect the pregnancy rate, while LRH-A3 and HCG increased the pregnancy rate of the cow. HCG of 5 IU/ml and 10 IU/ml increased the expressions of leukemia inhibitory factor but decreased those of interleukin-6, epidermal growth factor and vascular endothelial growth factor in endometrial cells. This study provided a plan for the use of LRH-A3 and HCG to increase pregnancy rate during TAI in dairy cows.

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle

Simple Summary

While cows are usually monovular, the incidence of dizygous twin births has recently increased considerably alongside increasing milk production. Genetic progress and improvements in nutrition and management practices have led to a continuous increase in milk yield and thus also to multiple ovulations and twin pregnancies. Twin pregnancies are undesirable as they seriously compromise the welfare of the cow and herd economy. A better understanding of the processes associated with multiple ovulations should help to reduce rates of twinning. During the stages of the sexual cycle, temperature gradients are established within the ovary and throughout the genital tract. Pre-ovulatory local cooling of the reproductive system favors male and female gamete maturation and subsequent fertilization. In fact, thermal mechanisms may prevent or favor multiple ovulations and thus twinning. The purpose of this review was to update this topic.

Abstract

While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.

Effect of capsaicin supplementation on lactational and reproductive performance of Holstein cows during summer

Context Summer ambient temperature and humidity are major factors negatively influencing the physiology and the productive and reproductive efficiency of dairy cows. Various management and breeding approaches may be useful for maintaining productivity in dairy cows during summer to minimise these effects. Aims The experiment was designed to test a natural phytochemical supplementation of capsaicin (CPS), followed by a specific oestrus synchronisation protocol as a means to maintain productivity and reproductive performance of Chinese Holstein cows during summer in Hubei province, China. Methods Lactating Chinese Holstein cows (n = 109) were randomly divided into four groups and supplemented with 0 (control, n = 27), 20 (CPS-20, n = 26), 40 (CPS-40, n = 28) and 60 (CPS-60, n = 28) mg of capsaicin (CPS) per kg of total mixed ration respectively for continuous 30 days initiated on 10 July 2018. Milk production and composition were measured over 45 days from the start of CPS supplementation. After CPS supplementation, all cows were synchronised through a modified Ovsynch oestrus synchronisation protocol, and reproductive variables were recorded. Metabolic parameters were measured on the days before CPS supplementation, artificial insemination (AI) and 50 days post-AI. Key results Highest (P &lt; 0.05) milk production were found in the CPS-40 group, and highest total solids and milk fat in the CPS-20 and CPS-40 groups. Milk urea nitrogen and milk fat were generally increased in CPS supplemented cows compared with the control group. Significant increases (P &lt; 0.05) in oestrus response, ovulatory follicle size, ovulation rate and pregnancy rates were observed in the CPS-40 group compared with other groups. Glucose, lipoprotein esterase and aspartate aminotransferase were increased (P &lt; 0.05) in CPS-40 and CPS-60 supplemented groups at the time of AI and 50 days post-AI. Conclusions CPS supplementation has the capacity to maintain milk yield, milk composition and serum metabolites in Chinese Holstein dairy cows during summer. The synergistic effect of CPS and the modified oestrus synchronisation protocol also improved reproductive variables of the cows. Implications Adoption of CPS as a supplement along with oestrus synchronisation could be a useful and economical strategy for dairy herd keepers to improve herd performance during summer.

The GnRH analogue dephereline given in a fixed-time AI protocol improves ovulation and embryo survival in dairy cows

This study compares the fertility effects of inducing ovulation using the GnRH analogue, dephereline, versus natural GnRH at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in in heat-stressed and non-heat stressed lactating dairy cows. Cows were given GnRH (GnRH group, n = 369) or dephereline (DEPH group, n = 379) and were inseminated 14-20 h later. Dephereline treatment increased corpus luteum (CL) size on Day 7 post-AI compared with GnRH (P < .0001) while a one-mm increase in CL size was found to give rise to a 1.1-fold increase in the pregnancy rate at FTAI (P = .001). Based on odds ratios, the interaction between treatment and heat stress had a significant effect on the ovulation failure rate (P < .01). This meant that relative to non-heat-stressed GnRH-treated cows, ovulation failure was 2.9 times more likely in heat-stressed GnRH-treated cows (P = .001), 0.3 times less likely in non-heat-stressed DEPH-treated cows (P = .04) and was similar in heat-stressed DEPH-treated cows. Further, non-heat-stressed DEPH-treated cows were more likely to conceive by a factor of 1.6 than the remaining cows (P = .03). Finally, GnRH-treated multiparous cows were 9.9 times more likely to suffer pregnancy loss than the remaining cows (P = .03). Our results indicate that, compared to treatment with GnRH, dephereline reduced the risk of ovulation failure and consequently increased the pregnancy rate under heat stress conditions. In multiparous cows, dephereline treatment also reduced the negative age effect on pregnancy maintenance.

Inducing ovulation with hCG in a five-day progesterone-based fixed-time AI protocol improves the fertility of anestrous dairy cows under heat stress conditions

This study compares the fertility effects of inducing ovulation using human chorionic gonadotropin (hCG) versus gonadotropin releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in heat-stressed and non-heat stressed anestrous lactating dairy cows. Heat stress (HS) was defined as an environmental temperature-humidity index (THI) > 72. A P4 intravaginal device (CIDR) was fitted for five days and GnRH administered upon CIDR insertion and a double dose (24 h apart) of prostaglandin F_2α upon CIDR removal. Cows then received either GnRH (GnRH group; n = 506), or hCG (hCG group; n = 493) 36 h after CIDR removal and were inseminated 50-56 h after CIDR removal. Ovulation failure was investigated in a subset of 425 cows: 223 and 202 receiving GnRH and hCG, respectively. Based on odds ratios, the interaction between treatment and HS had a significant effect on the ovulation failure rate (P = 0.01). This meant that compared to the rates recorded in non-heat-stressed, GnRH-treated cows (13%), ovulation failure in heat-stressed GnRH-treated cows (25.3%) was more likely by a factor of 2.3 (P = 0.04), in non-heat-stressed hCG-treated cows (2.3%) was less likely by a factor of 0.16 (P = 0.02) and was not significantly different in heat-stressed hCG-treated cows (7%). Interactions between treatment and HS and between treatment and parity had a significant effect on the pregnancy rate (P = 0.0001 and P = 0.001, respectively). The treatment-HS interaction determined that compared to the rates recorded in non-heat-stressed, GnRH-treated cows (30.5%), pregnancy in heat-stressed GnRH-treated cows (17.6%) was less likely by a factor of 0.48 than the remaining cows (P = 0.001), whereas because of the treatment-parity interaction, compared to the rates recorded in primiparous, GnRH-treated cows (31.4%), pregnancy in GnRH-treated multiparous cows (18.9%) was less likely to conceive by a factor of 0.51 than the remaining cows (P = 0.002). No significant effects of treatment on the rates of pregnancy loss or twin pregnancy were identified by binary logistic regression. In conclusion, hCG treatment given at the end of a 5-day P4-based protocol for FTAI improved ovulation and pregnancy rates in anestrous cows under conditions of HS and also had a beneficial impact on the pregnancy rate in anestrous multiparous cows throughout the year.

The presence of two ovulatory follicles at timed artificial insemination influences the ovulatory response to GnRH in high-producing dairy cows

This study sought to examine the impact of the presence of two co-dominant (ovulatory) follicles at the time of artificial insemination (AI) on the ovulatory response to GnRH given in a fixed-time AI protocol. The study population comprised 622 lactating dairy cows: 306 (49.2%) with a single follicle, 198 (31.8%) with two bilateral follicles (one follicle per ovary) and 118 (19%) with two unilateral follicles (same ovary). Based on odds ratios, cows with two bilateral or unilateral follicles were less likely (by factors of 0.09 and 0.11, respectively) to undergo ovulation failure compared with cows with one follicle (P = 0.01 and P = 0.02, respectively); the likelihood of ovulation failure decreased 0.75 times with every one-mm increase in follicle diameter for cows with a single follicle, whereas individual follicle diameter was not related to ovulation failure in cows with two bilateral follicles (P = 0.001). The likelihood of double ovulation decreased 0.7 times with every one-mm diameter difference between the larger and smaller follicle for all cows with two follicles (P = 0.001), whereas cows with two unilateral follicles showed a higher (P < 0.05) double ovulation rate than cows with two bilateral follicles. In 116 (58.6%) of the cows with two bilateral follicles, only the larger follicle ovulated in 59.5% cows, whereas only the smaller one ovulated in the remaining 40.5% cows. In these cows, a one-mm size difference between the larger and the smaller follicle gave rise to a 1.12-fold increase in the ovulation failure rate for the larger follicles (P = 0.0001). Cows with two bilateral follicles were more likely (by a factor of 1.5) to conceive than cows with one follicle (P = 0.001). Significant right-left differences were not found in cows with two bilateral follicles, whereas the right ovary was more active than the left in the remaining cows. Our results indicate that cows with two co-dominant follicles at AI show different ovulation patterns to those with one dominant follicle. A higher rate of ovulation failure was observed among cows with one follicle than cows with two follicles, whereas the conception rate was higher for cows with two bilateral follicles than for the remaining cows. In cows with two follicles, double ovulations along with ovulation of the smaller follicle were related to the least size difference between the larger and smaller follicle.