PREGNANCY RATES AND NON-RETURN RATES FOLLOWING ARTIFICIAL AND NATURAL BREEDING IN DAIRY HERDS

SUMMARY Information routinely supplied during the conduct of a dairy herd health program was analysed to evaluate the performance of artificial breeding in Victoria. A comparison was made between 60 to 90-day non-return rates (supplied by artificial breeding centres) and pregnancy rates (determined by manual pregnancy diagnosis) for first artificial inseminations in 108 herd years in which both items were available in the 1973 and 1974 breeding seasons. The values were 69.3% and 58.2% respectively (P <0.001). Non-return rates and conception rates were found to decline as herd size increased. Pregnancy rates to first artificial and natural services did not differ significantly from each other but pregnancy rates were significantly more variable to natural than artificial service (P < 0.001). The mean pregnancy rate to artificial insemination for all herd years studied was 57.5% and the pregnancy rate to natural service was 58.0%.     

Parameters to monitor dairy herd fertility and their relation to financial loss from reproductive failure

Relationships between herd fertility measurements and financial loss from reproductive failure in dairy herds were studied. Financial losses attributable to prolonged calving interval and forced replacement from reproductive failure were considered. Herd fertility parameters were calculated from artificial insemination and calving data (i.e. calving to first service interval, non-return rate 56 days after first service, percentage of correct inseminations carried out in the interval 18–24 days, fertility status, calving interval, an oestrus index and number of insemination per average cow present in the herd.

The herd fertility parameters were moderately-highly related to loss due to suboptimal calving interval (r=0.20−0.79 in absolute values), but only slightly related to losses due to forced replacement (r<0.17 in absolute values).

Repeatabilities, calculated over a 3-year period, were high for the interval to first service, non-return rate and the oestrus index (0.52−0.67) and moderate for percentage correct reinseminations, fertility status, calving interval and loss due to suboptimal calving interval (0.38−0.48). Repeatability of loss due to forced replacement was low (0.20).

In a regression analysis no herd fertility parameter was fitted with respect to loss from forced replacement. Loss due to suboptimal calving interval at herd level was best estimated by the oestrus index (R²=0.63), the addition of the interval to first service to the regression equation explained a further 10% of the variation between herds. It is suggested that the oestrus index and the interval to first service should be presented as management aids to monitor herd fertility.     

Effect of deposition site and sperm number on the fertility of sheep inseminated with liquid semen

The effect of the deposition site and the numbers of sperm on the fertility of sheep was tested in a field trial in which 1292 Norwegian crossbred ewes aged between six months and five-and-a-half years from 52 farms were inseminated with liquid semen after natural oestrus. Cervical insemination with 150 x 10(6) and 75 x 10(6) spermatozoa resulted in 25-day non-return rates of 63.7 and 56.1 per cent, and vaginal insemination gave non-return rates of 63.3 and 56.6 per cent, respectively. There was no significant difference between the cervical and vaginal inseminations, but the inseminations with 150 x 10(6) spermatozoa gave significantly higher non-return rates (P=0.004). There were significant differences between the non-return rates for different rams (P<0.0001) and farmers (P=0.0002) but the age of the ewe had no significant effect.     

Three types of acrosomal aberrations of bull spermatozoa and their relation to fertility

The effect of acrosomal aberrations of the spermatozoa of Finnish Ayrshire bulls on the corrected non-return rate within 60 days of the first 500 inseminations was studied. The material consisted of sperm samples examined by the artificial insemination societies. All samples had been accepted for use in artificial insemination. One Giemsa-stained slide was studied for each of the 95 bulls concerned. Samples showing distinct acrosomal defects were studied by electron microscopy. Three different types of acrosomal aberration were found. One was obviously associated with subfertility in all 6 bulls in which it was detected.     

Fine mapping of a quantitative trait locus on chromosome 9 affecting non-return rate in Swedish dairy cattle

We previously mapped a quantitative trait locus (QTL) affecting the trait non-return rate at 56 days in heifers to bovine chromosome 9. The purpose of this study was to confirm and refine the position of the QTL by using a denser marker map and fine mapping methods. Five families that previously showed segregation for the QTL were included in the study. The mapping population consisted of 139 bulls in a granddaughter design. All bulls were genotyped for 25 microsatellite markers surrounding the QTL on chromosome 9. We also analysed the correlated trait number of inseminations per service period in heifers. Both traits describe the heifer's ability to become pregnant after insemination. Linkage analysis, linkage disequilibrium and combined linkage and linkage disequilibrium analysis were used to analyse the data. Analysis of the families jointly by linkage analysis resulted in a significant but broad QTL peak for non-return rate. Results from the combined analysis gave a sharp QTL peak with a well-defined maximum in between markers BMS1724 and BM7209, at the same position as where the highest peak from the linkage disequilibrium analysis was found. One of the sire families segregated clearly at this position and the difference in effects between the two sire haplotypes was 2.9 percentage units in non-return rate. No significant results were found for the number of inseminations in the combined analysis.     

Growth hormone treatment of breeding bulls used for artificial insemination improves fertilization rates

To evaluate new therapeutical concepts for male subfertility, we tested the effects of exogenous recombinant bovine growth hormone (rbGH) on various endocrine and metabolic parameters both in blood and in seminal plasma of bulls. Sperm quality was assessed morphometrically and by monitoring the number of successful artificial inseminations (AIs) defined as non-return rates (NRR). Aliquots of 450 semen samples were used from each bull and each experimental period (4 wk before, 14 weeks during and 6 wk after treatment). Six out of ten sires (average age 8.4 years) were treated every two weeks with 640-mg depot formulated rbGH (Eli Lilly). Four bulls received vehicle only. Blood plasma bGH, IGF-I, insulin and glucose concentrations were increased with rbGH treatment. In seminal plasma there was no effect of rbGH treatment on fructose and citrate or on testosterone concentrations. With one exception, rbGH-treated bulls had greater IGFBP-3 concentrations in seminal plasma. Motility of spermatozoa after freezing and thawing was increased compared with pretreatment rates. Most interestingly, the number of successful AIs was increased by an average of 6.0% NRR when ejaculates from rbGH-treated bulls were used.     

Low Fertility in Daughters of Bulls with 1/29 Translocation

Non-return rates at different stages after insemination were compared in daughters (n = 21,212) of five translocation heterozygous sires with all cows and heifers (n = 610,714) represented in the Norwegian Red Cattle (NRF) breeding statistics during the period October 1970 to September 1972. The daughters of the carrier bulls showed statistically significant lower non-return rates for 0–30, 30–60, 60–90, 90–120, 120–150, 150–180 and 180–270 days as compared with the control animals. The decline in non-return percentage for the daughters of translocation sires was greater than in the control animals during the period from 0–30 to 60–90 days indicating higher losses of fetuses during the early period after insemination.Daughter groups of carrier bulls consisting of adult cows only showed higher non-return rates than groups comprising both cows and heifers.     

Associations of Male Fertility Traits with Blood Groups and Blood Protein Polymorphisms in Dairy Cattle

Abstract

The relationships between 12 polymorphic systems and bull fertility were studied in the Swedish Red and White dairy cattle population. The material consisted of 1447 young bulls with non-return rates based on at least 500 inseminations each. A reduced animal model including a full additive relationship matrix was used. Multiple regressions were fitted for the estimation of the average gene substitution effects as well as the gene-frequency-independent effects of additive gene action and dominance. To evaluate the results a multivariate analysis of variance, classical segregation analyses and marker frequency studies were performed. Significant associations were found between the F, B, Tf, S and C systems, and nonreturn rates, but the contribution of the markers to the total variation of non-return rates was small.     

Changes in Semen Quality in Estonian Holstein AI Bulls at 3, 5 and 7 years of Age

The predictability of semen quality of mature sires from measurements at an early age is not well established. The aim of the present study was to determine age-dependent changes in the quality of bull semen from six Estonian Holstein (EHF) bulls, processed when the sires were 3, 5 and 7 years old. Fertility data such as 60-day non-return to oestrus rates (60d-NRRs) were available for 3-year-old bulls. From each batch, semen straws were analysed immediately after thawing [i.e. post-thaw (PT)] (controls) and after a swim-up (SU) procedure. The analyses comprised subjective and computerized measurements of sperm motility using computer-assisted sperm analysis (CASA) as well as estimations of sperm concentration, morphology and membrane integrity. There was a significant (p < 0.05) increase in the percentage of sperm motility (SU), membrane integrity (PT, SU) and normal tail and acrosome morphology (SU) with an increase in the age of the sires. The percentage of total motile spermatozoa PT measured by CASA correlated between 3- and 7-, and between 5- and 7-year-old bulls (p < 0.05). In addition, the proportion of head abnormalities tended to correlate between all three age groups both PT and after SU (p < 0.1). The sperm parameters correlating with fertility were average path velocity (VAP) (p < 0.001), total motility as measured by CASA (p < 0.01), linearly motile spermatozoa (p < 0.05) and CASA-assessed numbers of motile spermatozoa (p < 0.05), all after SU selection. The results showed that overall semen quality examined at 3 years of age is related to the semen parameters later in bulls' life. Moreover, CASA-assessed motility after SU seems to be a reliable marker for semen quality assessment as it shows correlation not only between the ages, but also to field fertility.     

Reproductive performance in South Australian dairy herds

SUMMARY Herd breeding records (161) were examined from a random 10% sample of dairy farms (96) in South Australia with more than 40 cows and suitable breeding records for 1988 and/or 1989. Of these farms, 53 (55.2%) had a year-round calving pattern, 42 (43.8%) claimed to be seasonal and one was changing from a year-round to a seasonal pattern. Only 14.6% of farmers observed oestrous behaviour outside milking times and 18.8% used tailpaint. Overall, the average proportion of unobserved heats was estimated to be 32%. Artificial insemination (AI) was carried out on 85.4% of farms (16.7% used AI alone and 68.7% also used bulls) of which 32.9% used commercial technicians and 67.1% were do-it-yourself operators. Overall, the average 30-day submission rate was 59.9% and the average 49-day non-return to service rate was 58.9%. Investigation into the probable causes of suboptimal reproductive performance gave a tentative diagnosis of inefficient oestrous detection, deferral of service, inadequate nutrition, poor AI technique, insufficient bulls, and venereal/other diseases in 69.1, 32.1, 27.2, 28.4, 13.6 and 7.4% of records, respectively.     

Genotype by Environment Interaction in Nordic Dairy Cattle Studied Using Reaction Norms

Genotype by environment interaction for production and fertility was studied by use of a reaction norm model. Milk recording data, comprising 927 929 records, were analysed to predict reaction norms for young bulls of the Nordic Red dairy breeds. Random regressions were estimated for each bull, regressing phenotypic values of daughters on herd environment. The phenotypic measures were 305 days kg protein production and days open in first lactation. The herd environment was defined as the herd-year average of protein production and days open, respectively. Heritability of protein production and days open and genetic correlation between the two traits were estimated as functions of the herd environment. The results showed that the genetic parameters change over environments, which are measured on a continuous scale across countries. Grouping of observations is avoided and thereby the problem of genetic connectedness between groups or countries may be avoided. Although significant genetic variation for the slope of the reaction norm was found, there was little reranking of sires, except between extreme environments. More appropriate models and methods need to be developed for further studies of genetic variation in reaction norms.     

Risk factors for repeat-breeder syndrome in New South Wales dairy cows

A retrospective case-control study involving 1041 cow lactations from 10 commercial dairy herds in Australia determined relationships between biographic, production, reproductive and disease factors and repeat-breeder syndrome (RBS) (conception to greater than two inseminations). The study population was stratified into primiparous- and multiparous-cow sub-groups and logistic regression was used. Effects of herd were examined by including this variable alternatively as a fixed and a random effect. In the primiparous-cow fixed-effect model, the risk of RBS was increased with post-calving metritis, stillbirth, and with increasing days taken to reach peak milk yield, and reduced following dystocia. An inverted U-shaped relationship with total milk-solids percentage at the time of first service was detected. In the multiparous-cow fixed-effect model, the risk of RBS was increased in cows with chronic metritis, cystic ovarian disease (COD), in cows of parity >5 and in cows that were sub-fertile in the previous lactation. Increasing days to first recorded heat (DFH) reduced risk of RBS and a non-linear relationship with average 120-day milk-protein percentage was found. When herd was fitted as a random effect, stillbirth and 120-day average milk-protein percentage were no longer significant in the primiparous and multiparous models, respectively. The study emphasises the need to control appropriately for the clustering effect of herd and supports the need to minimise periparturient disease and improve nutrient balance to achieve optimal fertility in dairy herds.     

Direct and maternal genetic parameters of fertility traits in Friesian cattle

Variance and covariance components for sire of cow and sire of insemination of fertility traits were estimated by parity using REML procedures. Subsequently direct genetic and maternal components were calculated. Heritabilities for 56-day non-return rate, conception rate (heifers, parity one to three) and days open (parity one to three) varied between 0.007 and 0.049. The heritability for age at conception in heifers was 0.192. The maternal component for days open was greater than the direct genetic component. The genetic correlations between sire of insemination and sire of cow for non-return rate changed from −0.29 in heifers to 0.59 in parity three, that for conception rate from −0.74 to 0.48. The relation between maternal and direct genetic components changed from −0.94 to 0.26 and −0.97 to 0.12 for non-return and conception rates, respectively. Changes in correlations for days open from parity one to three were smaller. The results indicated that the genetic correlation between the sire of cow components for non-return and conception rate in heifers, first parity and older cows may differ from unity.     

Effects of the Sire and District of A1 on Cow Fertility

Insemination results per bull and district of AI (or technician) were analysed in a 5 year study. Return Rates (RR) were registered between Oct. 1976 and Sept. 1981. Data included 856 850 first AI made by 56 technicians. Depending on years, AI were made with the semen of 81 to 103 bulls of 5 breeds. Only bulls which performed at least 500 AI's per year were taken into account. A first analysis made with the data of 14 bulls represented during the 5 years show that: 1) the breed, the bull within breed and district of AI (or technician) were the most important factors influencing RR. RR were less affected by other factors such as the size of the herd or the year. 2) results given for successive RR were nearly identical from RR₂₄ to RR₉₀. 3) the effect of breed, bull and district of AI were less important on the variable illustrating more specificially late return in oestrus (RR_25–300). Yearly analysis involving larger number of bulls gave very similar results to the 5 year study. Variability due to the district of AI (or technician) and to the bull were of the same magnitude. Maximum differences between bulls or districts varied from 10% (RR₂₄) to 20% (RR₉₀). As strong relationships between bull and district of AI or technician were found, complementary analyses from the 1978 set of data were made to investigate how the variability due to the district of AI could introduce bias when estimating bull's RR. Comparisons between models were made on the basis of correlations between a reference model including a district effect and reduced models. For RR₂₄ and RR₉₀ correlations between solutions were always higher than 0.97. This show that if sufficient number of AI's per bull are performed no major bias is introduced and the district of AI or technician is neglectable when evaluating bull's RR .     

Effect of cattle insemination carried out with and without assistance

It has been studied whether help with the insemination work from a herdsman improves the result of the insemination. Totally 52,716 inseminations performed by 55 insemination technicians and veterinarians are included in the study, 18 per cent of these inseminations were performed without help. The data are analysed by a least squares procedure. The model used included lactation number of the cow (ai), insemination month (mj), the person who performed the insemination (ink), whether he had been helped with the insemination or not (hl) and interaction between ink and hl. As measure of the result of the insemination 60 days non-return percentage was used (total 60 days N.R.-% and 60 days N.R.-% corrected for short returns, zero to three days). There was found no significant effect of help at insemination on either of the 60 days N.R.-%'s studied. However, to encourage good contact between the farmers and the inseminating personnel, it is beneficial that herdsmen are present when cows are inseminated.     

Aspects of Reproduction in New Zealand Dairy Herds

Summary

Records for over 28 000 cows in 316 herds serviced by the Bay of Plenty Livestock Improvement Association showed the average calving interval (CI) was 364 days (S.D. = ±31 days). Between-herd variation accounted for less than 1% of the total variation. The CI for cows conceiving to first insemination was 358 days compared to 367 days for conceptions to second inseminations, but the CI for this latter group of cows was significantly influenced by the interval between inseminations. When the between-service interval was 17 days or less the ensuing CI was 352 days, compared to 374 days for a between-service interval of 18 to 24 days. The results indicate that while the high incidence of short-return intervals to first insemination in New Zealand dairy cattle will reduce non-return rates, the factors producing these short-return intervals are not increasing CI's. The estimated intervals from calving to first service varied from 57 to 76 days.

Although the A.B. service was used for an average of only 36 days, the total breeding period averaged 102 days after which time 5.4% of the cows in the herd remained empty. The regression coefficient between total breeding period and percentage of empty cows was only ?0.28% fewer empty cows per extra week. While this relationship was statistically significant there was a wide variation in the percentage of empty cows among herds with the same breeding period.     

宁夏地区荷斯坦牛青年牛繁殖性状遗传参数估计

旨在探究青年牛繁殖性状遗传能力群体遗传参数,评估不同配种季节间青年牛繁殖性状基因型与环境的互作效应(G×E).本研究利用宁夏地区12个牧场2007-2019年荷斯坦牛繁殖事件信息记录,计算青年牛繁殖性状包括:首配日龄(AFS)、初产日龄(AFC)、首次配种后56天不返情率(NRR56)、首末次配种间隔(IFL)、妊娠期...     

Reproductive Parameters and Efficiency of Inseminators in Dairy Farms in Portugal

This study was carried out to determine the reproductive efficiency indices of one of the largest dairy co-operatives of northern Portugal, using data from 1980 to 1998. Records were made available by the computerized National Recording System. Age at first calving was 32.0 ± 6.0 months. Mean calving to first AI interval was 95.4 ± 30.0 days, and calving to conception intervals decreased (p < 0.05) from 176.9 ± 4.5 to 148.1 ± 5.6 days from the first to the fourth/fifth parturitions, respectively. Calving intervals decreased (p < 0.05) from 418.1 ± 3.4 to 392.5 ± 7.0 days from the first to fourth/fifth parturitions, respectively. Mean non-return rates at 90 days for first inseminations was 71.7 ± 6.5% and mean calving rates at first insemination was 51.4 ± 8.1%. There were significant differences (p < 0.001) in the inseminators' efficiency, measured by both non-return and calving rates at first AI, with differences between the best and worst results of 13.3 and 16.1% for non-return and calving rates, respectively. The ranking of the inseminators did not coincide when their efficiency was measured by either non-return or calving rates. The mean number of inseminations per pregnancy (pregnant cows only) was 1.4 ± 0.7 with significant (p < 0.001) differences among herds. The mean heat detection rate was 38.1 ± 16.9%, with highly significant (p < 0.001) differences among farms (ranging from 14.2 to 60.8%). Negative (p < 0.001) correlations were found between heat detection rate and calving to first AI, calving to conception and calving intervals. The meaning of these indexes for assessment of reproductive efficiency in the studied system, is discussed.     

Effect of vaginal and cervical deposition of semen on the fertility of sheep inseminated with frozen-thawed semen

The effect of vaginal and cervical deposition of frozen-thawed semen on the fertility of sheep was tested in a field trial in which 543 Norwegian crossbred ewes aged between six months and five-and-a-half years from 10 farms were inseminated after natural oestrus. Cervical insemination with 200 x 10(6) spermatozoa resulted in 25-day non-return and lambing rates of 75.4 and 72.7 per cent, respectively, and vaginal insemination gave rates of 71.3 and 67.4 per cent; the cervical inseminations produced significantly higher lambing rates (P=0.04). There were significant differences between the lambing rates for different rams (P=0.006) and different farmers (P=0.003), and there was a significant interaction between farmer and deposition site (P=0.03). After vaginal insemination fertility was encouragingly high, but the results varied with the farmer, and different flock and management conditions.