Variation In Conception Rate Research Articles

Taxa de concepção de acordo com o touro, escore de condição corporal e ocorrência de estro em vacas de corte Bos taurus lactantes submetidas à inseminação artificial em tempo fixo

ABSTRACT The objective of this study was to investigate the effect of estrus expression, body condition score (BCS), different sires and semen batches on the conception rate of suckled Bos taurus beef cows submitted to timed artificial insemination (TAI). Data from 7,737 TAI were obtained from five farms in South Brazil. Cows received an estradiol plus progesterone-based estrous synchronization protocol. Only sires (n = 13) with at least two semen batches and 50 AI in two different lots were included in the study. Conception rate was higher for cows in estrus (66.8% vs. 26.3%) or with BCS ≥ 3 (57.2% vs. 51.6%) than in cows without estrus or BCS < 3, respectively (P≤0.001). Conception rate per sire ranged from 42.6% (Sire L) to 74.3% (Sire K). Conception rate in cows with BCS ≥ 3 and estrus occurrence varied from 47.4% (Sire L) to 86.1% (Sire A) among sires. Conception rate differed among semen batches of the same sire (B1 = 58.5%, B2 = 62.5%, and B3 = 83.2%). In conclusion, there was individual variation in conception rate among AI sires and semen batches within sires. The conception rate was increased by estrus occurrence and greater BCS.

Evaluation of bull fertility in Italian Brown Swiss dairy cattle using cow field data

Dairy bull fertility is traditionally evaluated using semen production and quality traits; however, these attributes explain only part of the differences observed in fertility among bulls. Alternatively, bull fertility can be directly evaluated using cow field data. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. We then estimated sire conception rate using only factors related to the bull. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between high-fertility and low-fertility bulls. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.

Post artificial insemination conception rate of a Brahman bull in selected areas of Bangladesh

Background: To mitigate the increasing protein demand in Bangladesh, recently the government has started a program to inspire the farmers for rearing Brahman as a beef breed. But, it is necessary to assess the performance of frozen semen of Brahman bull and the other factors that affect the rate of conception after Artificial Insemination (AI) before widespread rearing in Bangladesh. Methods: Data on AI performance, different factors and rate of conception were collected from 150 inseminated cows and heifers of Sadar upazila, Mymensingh. The cows were inseminated by trained technician of Research Animal Farm of Department of Surgery and Obstetrics, BAU, Mymensingh. Results: The overall conception rate was 55.3%. The conception rate in Holstein Friesian cross (68.9%) and Sahiwal cross (66.7%) cows were relatively higher than that of Local (46%) cows. Upon increasing age the service required for conception was irregular. The conception rate with respect to different parities ranged from 47.0% to 58.7%. Cows received insemination at parity 1-2 showed highest conception rate (60.0%) and cows received insemination at parity 3-7 showed lowest conception rate (47.0%). There was no significant difference between them on conception rate. The conception rate was observed higher (69.2%) in the cows which were inseminated in spring than cows were inseminated in summer (57.3%), winter (53.3%) and rainy (38.5%). The pregnancy rate in cows having BCS 2.5-3 was higher (60.7%) than that of 2.0 and 3.5-4.0. However, the difference in conception rate did not vary significantly among different BCS of cows (p>0.05). The present study indicated that the pregnancy rate in cows was higher (76.9%) that yield 6-10 L of milk than those of 0, 1-2 and 3-5 L counterpart. However, the variation in conception rate with different milk yield was significant (p<0.05). The pregnancy rate in cows that inseminated between 19-24 hours was higher (66.0%) than that of ≤12 and 13-18 hours. The variation in conception rate with different interval between estrus to AI was significant (P<0.05). Conclusion: Further studies using more population of cows and semen donors are needed to confirm this result as low number of cows and only one semen donor were used in this study.

Factors affecting conception rates in AI bred buffaloes in field conditions

The objective of the study was to identify the factors affecting variation in conception rate of buffaloes inseminated by Murrah bulls’ frozen semen under field conditions. Total of 18,396 insemination records pertaining to 11,793 buffaloes that were inseminated artificially at BAIF’s field AI centers during the period of June 2010 to December 2014 in 3 states. Logistic regression analysis was used to compute the odds ratio and probability of conception rate. Records were classified according to agroclimatic zones, lactation order, season of insemination and body condition score. Agroclimatic zones, lactation order and body condition score showed significant variation. The overall conception rate was 48.01%. Conception rate of western plain zone of Uttar Pradesh was higher than other zones under study. Body condition score 3 was favourable where probability of conception was 0.51. Conception rate of first parity buffaloes was lower than other parities with the probability of 0.46. Conception rate increased in second parity with probability 0.52. Highest conception rate was found in fourth parity with probability 0.53. There was marginal difference between second to fifth parity. Season of insemination did not affect conception rate, however, the distribution of artificial inseminations was higher during the favourable season than that during lean-season. It could be inferred that the factors like agroclimatic zones, lactation order and body condition score should be considered while evaluating the conception rates in buffaloes.

Factors Influencing Conception Rates of Cameroonian Zebu Cattle (Bos Indicus) following Oestrus Synchronisation and Artificial Insemination

A study was carried out to identify and evaluate factors affecting variation in conception rate (CR) in Cameroonian Zebu cattle following oestrus synchronisation and artificial insemination (AI). Two hundred and six local female Zebu cattle were evaluated to determine relationship among lactation number, age, body condition score (BCS), days postpartum and conception rate. Animals received an intravaginal progesterone release device (PRID ® ) containing 1.55mg of progesterone and a capsule with 10mg estradiol benzonate for 10 days and were treated with luteolytic dose of PGF2∝ and 1000mg IU PMSG at the time of PRID ® withdrawal. Animals were inseminated 48 hours after PGF2∝ and PMSG injection. Pregnancy status was assessed by observed non-return to oestrus and confirmed by rectal palpation 55-60 days after insemination. The overall CR was 47.6%. CR was influenced (p< 0.05) by lactation number, age and days postpartum of cows. The multivariate logistic regression model used revealed that CR was optimum in primiparous cows, those between 4.5 -7 years old and 151-300 days postpartum.

Management practices associated with conception rate and service rate of lactating Holstein cows in large, commercial dairy herds

Data from lactating Holstein cows in herds that participate in a commercial progeny testing program were analyzed to explain management factors associated with herd-average conception and service rates on large commercial dairies. On-farm herd management software was used as the source of data related to production, reproduction, culling, and milk quality for 108 herds. Also, a survey regarding management, facilities, nutrition, and labor was completed on 86 farms. A total of 41 explanatory variables related to management factors and conditions that could affect conception and service rate were considered in this study. Models explaining conception and service rates were developed using a machine learning algorithm for constructing model trees. The most important explanatory variables associated with conception rate were the percentage of repeated inseminations between 4 and 17 d post-artificial insemination, stocking density in the breeding pen, length of the voluntary waiting period, days at pregnancy examination, and somatic cell score. The most important explanatory variables associated with service rate were the number of lactating cows per breeding technician, use of a resynchronization program, utilization of soakers in the holding area during the summer, and bunk space per cow in the breeding pen. The aforementioned models explained 35% and 40% of the observed variation in conception rate and service rate, respectively, and underline the association of herd-level management factors not strictly related to reproduction with herd reproductive performance.

Genetic and environmental factors influencing first service conception rate and late embryonic/foetal mortality in low fertility dairy herds

The objective of this study was to identify factors affecting variation in conception rate to first artificial inseminations (AI) (CR: number of pregnant cows on D80–100/inseminated cows) and the incidence of embryonic/foetal loss (LEM) between 21 and 80 days of pregnancy (number of cows non-pregnant on D80–100/pregnant on D21) in 44 low fertility dairy herds of the west-central region of France. Reproductive status was assessed using progesterone milk concentration on D0 = Day of AI and D21–24, plasma PSPB concentration on D30–35, rectal palpation on D80–100 and observed return to oestrous. The final data set contained 1285 Prim’Holstein cows, 5.0% (64/1285) were inseminated in the luteal phase (progesterone ≥3 ng/ml on D0), 61.3% (787/1285) were pregnant on D21–24 (progesterone <3 ng/ml on D0 and ≥5 ng/ml on D21–24), 15.4% lost their embryo/foetus between D21–24 and D80–100 (198/1285) and 45.8% (589/1285) were pregnant on D80–100. The incidence of late embryonic/foetal loss (LEM) was 25.2% (198/787). Multivariate logistic regression models including the random herd effect were used to analyse the relationship between AI centre, AI sire, cow's sire, parity, interval between calving and AI, milk production, milk protein content, body condition score (BCS) on D0, season of calving, season of AI, estimated genetic index on CR and LEM incidence. CR was significantly related to parity ( p < 0.05), milk production after calving ( p < 0.05) and estimated genetic value ( p < 0.01). A significant difference in CR was observed for calving to AI interval ≤70 days versus ≥90 days, but the overall effect of the interval was not significant ( p = 0.11). LEM incidence was affected by period of AI ( p < 0.05), milk production ( p < 0.05) and BCS ( p < 0.05), but was not related to estimated genetic index. In conclusion, in these low fertility herds, the incidence of LEM was high and 25% of the cows lost their embryo after 21 days of pregnancy. LEM was affected by specific factors (season, BCS), which were not related to CR. The absence of a relationship between estimated genetic index and LEM in spite of its effect on CR indicates that estimated genetic merit has a greater effect on early embryonic loss or fertilisation failure than on later stages of embryo development.

Impact of Protein Nutrition on Reproduction in Dairy Cows

In most but not all published studies, feeding diets with high concentrations of crude protein decreased reproductive efficiency. We were able to resolve some of the inconsistencies among published reports by considering the fate of consumed protein in the rumen and then using logistic regression analysis to identify factors affecting pregnancy. Our models showed that type and amount of protein fed explained much of the variation in conception rate. Age and dietary concentration of energy were identified as modifiers of the impact of protein on reproduction. Protein nutrition can affect reproduction through toxic effects of ammonia and its metabolites on gametes and early embryos, through deficiencies of amino acids, and by exacerbations of negative balances of energy. Alterations in the hypothalamic-hypophyseal-ovarian axis may be responsible for many of the effects of protein on reproduction.

Variation in conception rates following synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha.

Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycle either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F2 alpha (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and (or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (less than 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P less than .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P less than .05).

Seasonality of conception in hutterite colonies of Europe (1758–1881) and North America (1858–1964)

SummaryBirth records of Hutterite colonies were examined for the presence of seasonal variation in conception rate. Month of conception was inferred by counting back 9 months from date of birth. Over 4300 births, occurring between 1758 and 1964 and spanning the years that the colonies inhabited the Ukraine and then migrated to the United States and Canada, were included in the analysis. When combined, the European and North American births showed a seasonal pattern with a general rise in conceptions from December to June followed by a decline in conceptions from July to November. The major peaks in conceptions were in April and June, with a minor peak in December. Separate examination of the European and American records revealed a secular change. The seasonality of North American conceptions was dramatically reduced when compared to the very distinct European seasonal pattern. It is assumed that both biological and cultural factors are responsible for the seasonal variation observed. The influences of light cycle, date of marriage, and work and holiday schedules on conception rates are discussed.

Seasonal migration and seasonal variation in fecundability: Effects on birth rates and birth intervals

Seasonal patterns in conception rates have been documented in several recent studies. In this paper, a mathematical model of the reproductive process is developed through which the impact of such variation in conception rates is assessed. It is found that the effect on fertility can be quite substantial, but that the birth rate when seasonal variation is occurring is approximated well by the birth rate calculated when conception rates are constant at their mean. These results indicate that further documentation of seasonality in conception rates and exploration of the causes of these patterns and their change is an important area for demographic research.

Variation in conception rates due to sires in six breeds of zebu cattle

Variation in conception rates due to sires in six breeds of zebu cattle

Variation in Conception Rates of Guernsey Cattle

Summaary Data from 42 Guernesy herds served by one A.I. stud, and 37 Guernsey herds served by another were analyzed to determine heritability of conception rate. The data included records of 2,470 daughters of bulls in these studs, and breedings occurred during the period of 1950 to 1959. Heritability estimates from intrasire correlations of paternal half-sib groups were 0.08 and 0.02 based on an average of from one to four records per daughter, while those based on heifer records only were 0.06 and zero, respectively. Regression of daughters on dams yielded heritability estimates of 0.03 and 0.10 for the two studs.

Hereditary Variation in Conception Rate of Holstein-Friesian Cattle

Summary Variation in conception rates (based on birth of a live calf from first insemination to a high-fertility service sire) of 1,406 Holstein females was studied at one or two service periods (1,824 records) in 41 artificially inseminated herds. Fertility did not vary significantly between herds. Conception rates ranged from 43 to 94% in 27 paternal half-sib groups of heifers (P The heritability of conception rate was estimated from intrasire correlations of paternal half-sib groups to be approximately 8.5%. A comparison of the records of daughters at both service periods from 22 sires showed a trend toward an interaction between sire and parity of daughters (P ≠ 0.07). The value of selection in improving conception rate is discussed.

Cytological characteristics and fertilizing capacity of bull spermatozoa

1. Two methods were used to estimate the frequencies of nine morphological classes of spermatozoa in 257 ejaculates from one Guernsey, five Friesian and seven Hereford bulls at an insemination centre. In nigrosin-eosin stained preparations and in fixed wet preparations the respective mean frequencies (%) were: malformed heads, 1·08 and 0·98; malformed middle pieces, 0·88 and 0·89; bent tails, 3·92 and 4·56; coiled tails, 0·60 and 0·43; free heads, 3·72 and 2·63; free tails, 1·79 and 1·85; neck beads, 0·87 and 0·93; middle-piece beads, 4·91 and 6·83.2. There were close correlations between the two sets of measurements, but the differences of means were significant for free heads, bent tails, coiled tails, neck beads and middle-piece beads.3. The mean percentage of dead (eosinophil) spermatozoa was 21·0.4. The variations in the frequencies of each morphological class and of dead spermatozoa were divided within and between samples, ejaculates, bulls and breeds. The frequencies of all classes differed significantly between ejaculates within bulls; all but broken necks differed between bulls within breeds, and the Friesian and Hereford bulls differed in the frequencies of malformed heads, free heads, malformed middle pieces, free tails, neck beads and dead spermatozoa. The frequencies of bent tails, coiled tails and dead spermatozoa declined significantly with order of ejaculate.5. The interrelationships of the frequencies of each class were examined. Two new methods used to measure the dead-sperm content of semen were shown to give results significantly correlated with those obtained by the conventional staining method and with motility ratings.6. The interrelationships of measurements of the individual characteristics and conception rate were examined. Within-bull variations in conception rate showed a significant positive correlation (P &lt; 0·05) with the frequencies of malformed heads and free heads. The between bull variation in conception rate showed a negative correlation with the frequency of neck beads (P &lt; 0·05).