Embryo production with sex-sorted semen in superovulated dairy heifers and cows

The aim of this study was to examine the effect of sex-sorted semen on the number and quality of embryos recovered from superovulated heifers and cows on commercial dairy farm conditions in Finland. The data consist of 1487 commercial embryo collections performed on 633 and 854 animals of Holstein and Finnish Ayrshire breeds, respectively. Superovulation was induced by eight intramuscular injections of follicle-stimulating hormone, at 12-hour intervals over 4 days, involving declining doses beginning on 9 to 12 days after the onset of standing estrus. The donors were inseminated at 9 to 15–hour intervals beginning 12 hours after the onset of estrus with 2 + 2 (+1) doses of sex-sorted frozen-thawed semen (N = 218) into the uterine horns or with 1 + 1 (+1) doses of conventional frozen-thawed semen (N = 1269) into the uterine corpus. Most conventional semen (222 bulls) straws contained 15 million sperm (total number 30–45 million per donor). Sex-sorted semen (61 bulls) straws contained 2 million sperm (total number 8–14 million per donor). Mean number of transferable embryos in recoveries from cows bred with sex-sorted semen was 4.9, which is significantly lower than 9.1 transferable embryos recovered when using conventional semen (P ≤ 0.001). In heifers, no significant difference was detected between mean number of transferable embryos in recoveries using sex-sorted semen and conventional semen (6.1 and 7.2, respectively). The number of unfertilized ova was higher when using sex-sorted semen than when using conventional semen in heifers (P < 0.01) and in cows (P < 0.05), and the number of degenerated embryos in cows (P < 0.01), but not in heifers. It was concluded that the insemination protocol used seemed to be adequate for heifers. In superovulated cows, an optimal protocol for using sex-sorted semen remains to be found.     

Endocrine responses and estrous activity in Holstein heifers fed supplemental beta-carotene

Three trials involving 56 Holstein heifers were conducted to determine the effect of feeding supplemental beta-carotene (BC) on several reproductive parameters. Heifers were maintained in a loose housing system and group fed year-old brome hay ad libitum. All heifers were individually fed 2.73 kg of a concentrate mix daily. Half of the heifers received 300 mg BC/d (Trials 1 and 2) or 600 mg BC/d (Trial 3) blended in the concentrate mix. After 4 wk of dietary treatment, estrus was synchronized to facilitate observation for estrous activity and collection of blood samples. Two weeks after the treatment was initiated, concentrations of BC in blood serum were greater in the heifers that were fed supplemental BC as compared to control heifers. This difference increased to 6 wk. However, feeding supplemental BC had no effect on any of the reproductive parameters measured, including incidence of estrus and changes in progesterone and luteinizing hormone (LH) concentrations after PGF(2alpha), intervals from PGF(2alpha) to estrus and LH peak, estrual activity or first service conception rate. The results indicate that feeding supplemental BC does not alter reproductive performance in Holstein heifers.     

Embryo production from superovulated Holstein-Friesian dairy heifers and cows after insemination with frozen-thawed sex-sorted X spermatozoa or unsorted semen

The aim of this study was to evaluate embryo production in superovulated Holstein-Friesian dairy heifers and cows inseminated with either X-sorted spermatozoa (2 million/dose) or unsorted semen (15 million/dose). Experiment 1 at the research farm involved eight heifers, six cows and semen of one Holstein bull. All transferable embryos were diagnosed for sex. Experiment 2 included embryo collections on commercial dairy farms: X-sorted spermatozoa from three Holstein bulls were used for 59 collections on 28 farms and unsorted semen from 32 Holstein bulls were used for 179 collections on 79 farms. Superovulations were induced by eight declining doses of FSH (total of 12 ml for heifers and 19 ml for cows) starting on days 8-12 of the estrus cycle. Inseminations began 12h after the onset of estrus and were performed two to four times at 9-15 h intervals. Low-dose X-sorted inseminates were deposited into uterine horns and unsorted semen was placed into the uterine body. In Experiment 1, on average 70.3 and 75.0% of embryos recovered from heifers, and 48.4 and 100% of embryos recovered from cows were of transferable quality in X-sorted and unsorted groups, respectively. The proportion of transferable female embryos produced approximately doubled when insemination was with X-sorted spermatozoa compared to insemination with unsorted semen (heifers 96.4% versus 41.1%; cows 81.1% versus 39.8%). In Experiment 2, estimated 53.9 and 65.5% of embryos recovered from heifers, and 21.1 and 64.5% of embryos recovered from cows were of transferable quality in X-sorted and unsorted groups, respectively. Proportions of unfertilized oocytes were 21.1 and 10.6% for heifers and 56.0 and 14.4% for cows in X-sorted and unsorted groups, respectively. Consequently, cows inseminated with X-sorted spermatozoa produced significantly smaller proportions of transferable embryos (p<0.005) and significantly larger proportions of unfertilized oocytes (p<0.001) than those inseminated with unsorted semen. Proportions of quality 1 or degenerated embryos were similar for the two treatments in both heifers and cows. Within treatments, bulls did not significantly affect the proportions of transferable, unfertilized or degenerated oocytes/embryos. It was concluded that using low-dose X-sorted spermatozoa rather than normal-dose unsorted semen for the insemination of superovulated embryo donors can improve the proportion of transferable female embryos produced but this potential may not be achieved in commercial practice, particularly in cows, because of reduced fertilization rates when using low doses of X-sorted spermatozoa.     

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers.

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177).No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) >/=2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers.Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF(2alpha) (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001).Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows.These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.     

Function of beta-carotene and tocopherol in photosystem II

New and known structural and functional insights in the role of beta-carotene and of alpha-tocopherol in photosytem II are reviewed. A concept is presented connecting the failure of P680 triplet quenching by beta-carotene with the formation of singlet oxygen and its scavenging in the turnover of the D1 protein and by tocopherol in the maintenance of PS II structure and function.     

Milk production responses and rumen fermentation of dairy cows supplemented with summer brassicas

Forage brassicas, such as summer turnip (ST; Brassica rapa) and forage rape (FR; Brassica napus), are used as supplementary crops during summer. However, studies with lactating dairy cows fed these forages are limited and report inconsistent productive responses. The aim of this study was to determine dry matter intake, rumen fermentation and milk production responses of dairy cows in mid-lactation supplemented with and without summer (‘ST’ or ‘FR’) brassicas. Twelve multiparous lactating dairy cows were randomly allocated to three dietary treatments in a replicated 3 × 3 Latin square design balanced for residual effects over three 21-day periods. The control diet consisted of 16.2 kg DM of grass silage, 2.25 kg DM of commercial concentrate and 2.25 kg DM solvent-extracted soybean meal. For the other two dietary treatments, 25% of the amounts of silage and concentrates were replaced with FR or ST. The inclusion of forage brassicas had no effects on milk production (24.2 kg cow/day average) and composition (average milk fat and protein 43.2 and 33.6 g/l, respectively). Dry matter intake was 0.98 kg and 1.12 kg lower for cows supplemented with FR and ST, respectively, resulting in a greater feed conversion efficiency (1.35 kg milk/kg DM for ST and FR v. 1.27 kg milk/kg DM for the control diet). Intraruminal pH was lower for cows supplemented with ST compared to the control diet; however, it did not decrease below pH 5.8 at any time of the day. After feeding, the concentrations of total short-chain fatty acids (SCFAs) in rumen contents increased with ST supplementation compared to the control diet. Inclusion of FR in the diet increased the molar proportion of acetate (68.5 mmol/100 mmol) in total SCFA at the expense of propionate, measured 6 h after feeding of the forage. The molar proportion of butyric acid was greater with ST and FR supplementation (13.1 and 12 mmol/100 mmol, respectively) than in control cows. The estimated microbial nitrogen (N) flow was 89.1 g/day greater when supplementing FR compared to the control diet. Based on the haematological measures, the inclusion of summer brassica forages did not affect the health status of the animals. These results indicate that mid-lactation dairy cows fed brassicas are able to maintain production despite the reduced intake, probably due to improved rumen fermentation and therefore nutrient utilization.     

Embryo production by repeated superovulation of commercial donor cows

Mature beef cows of 13 major and several minor breeds were repeatedly superovulated by injections of follicle stimulating hormone (FSH) and prostaglandin F2 alpha (PGF). Embryos were collected nonsurgically 6 to 8 days after artificial insemination. The average number of transferable embryos per collection was measured on the basis of all cows started on superovulation. Within groups of cows superovulated from two to ten times, embryo production per collection declined with repeated collections. This decline was not apparent in the pooled data when the mean number of embryos per collection the first through the tenth collection was 5.6, 5.1, 4.9, 5.0, 4.3, 5.1, 5.0, 5.0, 5.4, and 5.6 embryos, respectively. Embryo production at the first collection was one of the criteria for selecting cows for repeated superovulation. Cows superovulated more than three times had the highest embryo production at the first collection. The decline in embryo production with repeated superovulation could not be corrected by increasing the FSH dose. The number of embryos per collection was significantly correlated in cows superovulated repeated times. The correlation coefficients varied from 0.32 in cows superovulated twice to 0.35 in cows superovulated 10 times. The predictability of embryo production from cows that were selected to remain in the embryo transplant program, and were superovulated more and more times, did not increase. Some cows continued to produce embryos after 20 repeated superovulations. The results indicated that a cow should be superovulated two or three times before being discarded as a poor embryo producer.     

Embryo production in superovulated cows: Transferable embryos correlated with total embryos

Embryo production was studied in 1,263 donor cows. The number of transferable (good) embryos per collection was highly correlated with the total embryos and ova in a collection (r = 0.64). Total ova and embryos per collection averaged 10.1 with a range from 0-70; the number of good embryos averaged 4.5 with a range from 0-37. Of all collections, 15.3% failed to yield any embryos or ova, and 32.4% did not yield any good embryos. The percentage of good embryos averaged 46.1 while the ratio of good embryos produced (5,680) to total embryos and ova produced (12,699) was 0.45.     

Relationships between conception rate in Holstein heifers and cows and milk yield at various stages of lactation

We investigated the relationships between conception rates (CRs) at first service in Japanese Holstein heifers (i.e. animals that had not yet had their first calf) and cows and their test-day (TD) milk yields. Data included records of artificial insemination (AI) for heifers and cows that had calved for the first time between 2000 and 2008 and their TD milk yields at 6 through 305 days in milk (DIM) from first through third lactations. CR was defined as a binary trait for which first AI was a failure or success. A threshold-linear animal model was applied to estimate genetic correlations between CRs of heifers or cows and TD milk yield at various lactation stages. Two-trait genetic analyses were performed for every combination of CR and TD milk yield by using the Bayesian method with Gibbs sampling. The posterior means of the heritabilities of CR were 0.031 for heifers, 0.034 for first-lactation cows and 0.028 for second-lactation cows. Heritabilities for TD milk yield increased from 0.324 to 0.433 with increasing DIM but decreased slightly after 210 DIM during first lactation. These heritabilities from the second and third lactations were higher during late stages of lactation than during early stages. Posterior means of the genetic correlations between heifer CR and all TD yields were positive (range, 0.082 to 0.287), but those between CR of cows and milk yields during first or second lactation were negative (range, −0.121 to −0.250). Therefore, during every stage of lactation, selection in the direction of increasing milk yield may reduce CR in cows. The genetic relationships between CR and lactation curve shape were quite weak, because the genetic correlations between CR and TD milk yield were constant during the lactation period.     

Comparison of embryo quality in high-yielding dairy cows, in dairy heifers and in beef cows

The purpose of this study was to compare embryo quality of lactating Holstein Friesian cows (LHFC), non-lactating Holstein Friesian heifers (NLHFH) and Belgian Blue beef cows (BB) and to identify factors that are associated with embryo quality in LHFC and NLHFH. After superovulation and embryo recovery at Day 7, embryos (n=727 from 47 LHFC, 27 NLHFH and 50 BB) were scored morphologically for quality, colour and developmental stage. Blood samples and data concerning parity, age, milk production and management were collected. Data were compared univariably between the three groups. A multivariable regression model was built with quality and colour of the LHFC and NLHFH embryos as dependent variables. Only 13.1% of LHFC embryos were categorized as excellent compared to 62.5% and 55.0% of the embryos in NLHFH and BB, respectively. Almost none of the NLHFH or BB embryos displayed a dark appearance of the cytoplasm compared to 24.1% of the LHFC embryos. Only 4% of all LHFC embryos reached blastocyst stage compared to 23.2% and 17.3% in NLHFH and BB. Based on the multivariable regression analysis, "physiological status" (lactating or not) together with the serum total protein concentration of LHFC and NLHFH, was significantly associated with embryo quality and colour. Thus, LHFC display an inferior embryo quality compared to NLHFH and BB. Producing milk or not seems to be significantly associated with embryo quality. Therefore, reduced embryo quality on Day 7 following AI, could be an important factor in the subfertility problem in modern high-yielding dairy cows.     

Plasma progesterone levels during the estrous cycle of Holstein and Brahman cows, Carora type and cross-bred heifers

Daily plasma progesterone (P(4)) was determined during one estrous cycle of 19 cows and 18 heifers of four different breeds: Holstein (H), Brahman (B), Carora-type (C) and crossbred (CB) females. Estrus detection was made by visual observation and using a teaser bull with a chin-ball marker. The P(4) profiles showed no differences among groups. In Group 1 (H), P(4) levels ranged from 0.5 ng/ml plasma on the day of estrus (Day 0) to 5.1 ng/ml at the luteal phase peak (Day 13). In Group 2 (B), P(4) levels ranged from 0.5 ng/ml on Day 0 to 9.2 ng/ml on Day 13. In Groups 3 (C) and 4 (CB), P(4) levels ranged from 0.5 ng/ml, on Day 0, to 13.7 ng/ml on Day 12 and 8.8 ng/ml on Day 13. These last two groups were moved to the same location and then compared. It was found that P(4) concentrations were significantly higher (P < 0.025) in Group 3 between Days 7 and 14 of the estrous cycle. In all groups, P(4) levels were lower than 1 ng/ml one day before the next estrus, and levels of 0.4, 0.5, 0.4 and 0.4 ng/ml were obtained the day of estrus in Groups 1 to 4, respectively. Results indicated that the pattern of P(4) for each one of the groups was similar to those reported by other investigators.     

Association of genetic polymorphism inGH gene with milk production traits in Beijing Holstein cows

Associations were analysed between polymorphisms of the growth hormone gene (GH-MspI) (localized in intron 3) and milk production traits of Beijing Holstein cows (a total of 543 cows). Polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method was used for identification of various geno-types. Frequencies of genotypes were 0.77, 0,21 and 0.02 for A/A, A/B and B/B, respectively. The frequency of theGH ^A allele is 0.875. The results of the least squares means show that in all three lactations, theGH A/A cows yielded more milk (P < 0.01 for lactation I andP 0.05 for lactations II and III), whereas A/B cows showed higher milk fat content than A/A individuals (P < 0.05 for lactations I and II, andP < 0.01 for lactation III). The A/A cows yielded more fat than A/B individuals (P < 0.01 only in lactation I). The A/A cows yielded more milk protein than A/B individuals (P < 0.01 for lactations I, II, and III). The A/A cows produced milk of higher protein content than of A/B individuals (P < 0.05 only in lactation II).     

Recovery rate and quality of embryos collected from suckled cows and beef heifers after superovulation with PMSG

Recovery rate and embryo quality were investigated in beef heifers and suckled cows following superovulation induced by 2000 IU pregnant mare serum (PMSG) combined with different methods of estrus cycle synchronization (Norgestomet, Prid, Dinolytic, Norgestomet combined with Dinolytic). Genital tracts were flushed upon slaughter with Dulbecco's medium 6.5 to 7.5 days after insemination. Of the heifers, 42 out of 43 responded to treatment. The mean embryo recovery rate, based on the number of corpora lutea, was only 14.8%. Of the 83 embryos recovered, 54.2% had developed to the expected stage and only 40% appeared normal. Of the adult cows, 55 out 58 responded with an embryo recovery rate of 39.5%. Of the 149 embryos recovered, 48.9% had developed to the expected stage and 67.1% of these appeared normal. In both heifers and adult cows, the different methods of estrus synchronization produced no significant differences in recovery rate or embryo quality.     

Factors affecting reproductive performance of Holstein heifers

The objectives were to evaluate factors affecting reproductive performance of dairy heifers. Holstein heifers (6389) were housed in a feed lot located in Parma, ID. Each week heifers weighing > or =290 kg were initiated in the reproductive program, which consisted of one injection of PGF(2alpha) and AI on detection of estrus. Heifers not inseminated by 11 days after the initiation of the breeding program received a second injection of PGF(2alpha). Pregnancy was diagnosed at 40+/-3 and 90+/-3 days after AI. Average daily minimum temperature (ADMnT), average daily maximum temperature (ADMxT), and average daily rainfall (ARF) were recorded between 15 days prior to and 15 days after the day of AI or the day of initiation of the breeding program. Exposure to air temperature was classified as: cold stress (CS=ADMnT< or =4 degrees C), no stress (NS=ADMnT>4 degrees C and ADMxT<29 degrees C), and heat stress (HS=ADMxT> or =29 degrees C). Exposure to rainfall was classified as above (HRF) or below (LRF) the mean for the period in question. Heifers were classified according to body weight at initiation of the breeding program as thin (TH<340 kg); moderate (MD=340-365 kg); and heavy (HY>365 kg). Service sire was associated with conception rate at 40 and 90 days after first AI. Although exposure to air temperature was not correlated with conception rate at 40 days after first AI, heifers exposed to cold stress had smaller conception rates at 90 days after first AI because they were more likely to lose pregnancy between 40 and 90 days of gestation. The proportion of heifers inseminated after initiation of the breeding program was correlated with body weight and exposure to cold stress. Exposure to cold stress was also correlated with the proportion of heifers conceiving within 11 and 22 days after initiation of the breeding program. From this study a correlation was established between body weight and rate of insemination and between the exposure to cold stress and reproductive efficiency of Holstein heifers.     

Pregnancy rate in cows and heifers bred to bulls selected for semen quality

A two-year study was conducted to compare fertility in cows or heifers bred to either an unselected group of bulls or bulls selected for semen quality. An improvement of 5% in pregnancy rate was found the first year in 591 cows bred to bulls having 80% or more normal sperm, compared to the 656 cows bred to a group of bulls representative of the original population (original group). A similar difference in pregnancy rate was noted the second year between 1179 heifers bred to the original group of bulls and the 522 heifers bred to bulls having 80% or more normal sperm and the 769 heifers bred to bulls with 70% or more normal sperm.     

Reproductive characteristics of Holstein heifers fitted with intravaginal temperature transmitters

In this experiment, the safety and feasibility of intravaginal temperature transmittance were tested by radio-telemetry. Each transmitter was positioned non-surgically with a plastic anchor. Heifers wore these transmitters for 107 days with no apparent physical or physiological effect. While the transmitters remained in place, estrous cycles, estrous behavior and fertility following artificial insemination were normal. The data usually revealed a temperature spike of one day on the day of standing heat. Time series analysis enabled the identification of significant temperature departures where the base line was a changing value due to seasonal adjustments. The temperature increase measured at 0645 h was about 0.5 degrees C above the previous five-day average. Absence of 21+/-3-day cyclicity in temperature spikes for two heifers revealed their cystic ovary condition which was later confirmed by rectal palpation. Progesterone and estradiol-17beta patterns were normal for all but one of these heifers. Prostaglandin F2 proportional-induced estrous behavior lacked the expected temperature spike. Affected heifers usually continued to have their temperature spike one more time at a regular estrous interval from the spike prior to PGF2 proportional injection.     

Superovulatory responses of Holstein cows

Approximately 1000 registered cows and heifers were superovulated one to 10 times. Nonsurgical embryo recoveries were performed on all donors which exhibited estrus. Healthy donors produced more total ova and cleaving embryos and had a higher ovum recovery rate, fertilization rate and pregnancy rate from embryos transferred than did cows classified as infertile. While ovum number was not affected during 10 repeated superovulations, fertilization rate and embryo number decreased. The number of ova recovered from healthy cows was affected by season, and from infertile cows by the day of the estrous cycle on which FSH was started and by the number of days since calving. More ova were recovered from infertile cows synchronized with prostaglandins prior to superovulation than following a natural estrous cycle. The number of embryos recovered from infertile cows was affected by age and from healthy cows by daily milk production. Fertilization rates in both healthy and infertile cows were affected by age, time since calving, daily milk production, day of cycle FSH was injected and season. There was no effect of the day of recovery on the number of ova or embryos recovered from healthy or infertile cows.     

Superovulation and embryo recovery from peripubertal Holstein heifers

The use of peripubertal donors in embryo transfer (ET) programs presents significant opportunity to accelerate genetic gain in domestic livestock by reducing the generation interval. These studies were designed to evaluate feasibility of superovulation and embryo recovery in peripubertal heifers (starting at 7.8 months of age), and to determine whether subsequent reproductive and lactational performance of donor heifers were impaired. Study 1 utilized 10 pairs of contemporary full-sibling heifers in which one heifer in each pair was assigned to receive a superovulation regimen and her full-sibling contemporary received placebo. Treated heifers were artificially inseminated at estrus and embryos were flushed transcervically 4-6 days later. Based on recovery of oocytes and/or embryos, 9 of 10 heifers responded to the hormonal regimen and 12 total embryos were recovered. Seven embryos (58%) were transferred into recipients resulting in five pregnancies. Control and treated heifers remained in the herd and were bred at a natural estrus by AI at 15 months of age. Lactation records, i.e., 305 days mature equivalent (305 d ME) were obtained, and all animals were evaluated for udder conformation traits between 32 and 38 months of age. Reproductive traits (age at first calving and days to conception) and lactational traits of heifers subjected to embryo transfer and their non-treated full-siblings did not differ (P > 0.05). Study 2 was conducted to establish the commercial feasibility of hormonally programming peripubertal heifers ranging in age from 7.8 to 9.9; 10 to 11.9; 12 to 13.9 and >/= 14 months. In total, 3982 embryos were recovered from 520 heifers, with 2419 (60.7%) of those categorized as viable (transferable). The number of ova/embryos obtained per flush (5.6 +/- 1.0) and the number of transferable embryos (2.8 +/- 0.5) was reduced (P < 0.05) in heifers of age 7.8-9.9 months compared to all other age groups. There was no difference (P > 0.05) in the number of ova/embryos recovered (7.8 +/- 0.3), or the number of transferable embryos (4.8 +/- 0.2), among heifers that were >/=10 months of age. The number of unfertilized ova did not differ by age, however, more degenerate embryos tended to be recovered from heifers <10 months of age compared to heifers >/=14 months of age. These data indicate that transferable embryos can be safely recovered from heifers beginning at 10 months of age without compromising subsequent reproductive or lactational performance of the donor.     

Immunization against inhibin enhances both embryo quantity and quality in Holstein heifers after superovulation and insemination with sex-sorted semen

The objective was to investigate the feasibility of improving embryo yield in superovulated cows following insemination with sex-sorted semen by prior immunization against inhibin. Twenty-eight heifers were allocated into three groups: High (n = 10), Low (n = 10), and Control (n = 8). The High group received one primary (1 mg) and two booster (0.5 mg) vaccinations (28-d intervals) with a recombinant inhibin α-subunit in 1 mL of white oil adjuvant, whereas the Low group received half that dose, and the Control group received only adjuvant. After the last immunization, all heifers underwent a standard superovulation treatment (decreasing doses of pFSH for 4 d), followed by two AI with 2 × 10⁶ sex-sorted semen after the onset of estrus. Inhibin-immunized heifers had higher (P < 0.01) plasma antibody titres, and an earlier onset of estrus (P < 0.05) than Control heifers. The total number of embryo/ova, transferable, and grade 1 embryos in the High group (15.4 ± 1.9, 5.7 ± 0.7, and 3.8 ± 1.0, respectively) was significantly greater than that of the Control group (9.1 ± 1.2, 3.1 ± 0.5, and 0.6 ± 0.2), but was intermediate (P > 0.05) in the Low group (13.0 ± 2.3, 4.4 ± 0.7, and 1.2 ± 0.3). There were no significant differences among groups in number of unfertilized ova and degenerated embryos. The High group also had higher (P > 0.05) plasma progesterone concentrations on the day of embryo collection. In conclusion, immunization against inhibin improved both embryo quantity and quality following superovulation and insemination with sex-sorted semen.