Heritability Of Fertility Traits Research Articles

Estimation of genetic parameters for fertility traits in Chinese Holstein of south China.

Introduction: Chinese Holstein in South China suffer heat stress for a long period, which leads to evolutionary differences from Chinese Holstein in North China. The aim of this study was to estimate the genetic parameters of fertility traits for Chinese Holstein in South China. Methods: A total of 167,840 Chinese Holstein heifers and cows from Guangming Animal Husbandry Co., LTD farms were used in this study. The fertility traits analyzed were calving interval (CI), days open (DO), age of first service (AFS), age of first calving (AFC), calving to first insemination (CTFS), first insemination to conception (FSTC), gestation length (GL), non-return rate to 56days (NRR), and number of services (NS). Results: The descriptive statistics revealed that the same trait in heifers performed better than in cows, which was consistent with the other studies. The heritabilities of fertility traits in this study ranged from close to 0 (for NS of cows) to 0.2474 (for AFC of heifers). The genetic correlation of NRR between heifers and cows was 0.9993, which indicates that the NRR for heifers and cows could be treated as one trait in this population. Conclusion: The heritabilities of fertility traits in Chinese Holstein in south China were quite different from the heritabilities of fertility traits in North China. NRR56, NS, AFC, and CI were suggested to be included into the selection index to improve fertility performance of Chinsese Holstein of south China. The results of this study could provide genetic parameters for the animal breeding program of Chinese Holstein in the south of China.

Comparison of heritability estimates of first lactation fertility traits in Mehsana buffaloes

First lactation records of 3068 Mehsana buffaloes sired by 118 sires, under field progeny testing programme distributed in different 149 villages of 14 talukas maintained at Dudhsagar Research and Development Association, Dudhsagar Dairy, Mehsana over a period of 24 years (1989-2012) were used to estimate least squares means and heritability of fertility traits like, first service period (FSP), first calving interval (FCI) and daughter pregnancy rate (DPR). The least squares means of these traits were found to be 189.05±3.34 days, 472.97±2.87 days and 31.08±0.59%, respectively. Non genetic factors such as age at first calving and period of calving were found to have highly significant effect on all the traits, whereas, cluster found to be non-significant for FSP and significant for FCI and DPR. Heritability were estimated for FSP, FCI and DPR as 0.02±0.02, 0.004±0.015 and 0.095±0.031; 0.04±0.03, 0.026±0.024 and 0.089±0.032; and 0.01±0.02, 0.032±0.026 and 0.095±0.034 by LSML, BLUP-SM and BLUP-AM, respectively. BLUP-AM was found to be the best model for heritability estimation based on error variance and BLUP-AM gave highly significant and more accurate results than BLUP-SM and LSML in Mehsana buffaloes.

Symposium review: Breeding a better cow—Will she be adaptable?

Adaption is a process that makes an individual or population more suited to their environment. Long-term adaptation is predicated on ample usable genetic variation. Evolutionary forces influencing the extent and dynamics of genetic variation in a population include random drift, mutation, recombination, selection, and migration; the relative importance of each differs by population (i.e., drift is likely to be more influential in smaller populations) and number of generations exposed to selection (i.e., mutation is expected to contribute substantially to genetic variability following many generations of selection). The infinitesimal model, which underpins most genetic and genomic evaluations, assumes that each quantitative trait is controlled by an infinitely large number of unlinked and non-epistatic loci, each with an infinitely small effect. Under the infinitesimal model, selection is not expected to noticeably alter the allele frequencies, despite a potential substantial change in the population mean; the exception is in the first few generations of selection when genetic variance is expected to decline, after which it stabilizes. Despite the common use of the heritability statistic in quantitative genetics as a descriptor of adaption or response to selection, it is arguably the coefficient of genetic variation that is more informative to gauge adaptation potential and should, therefore, always be cited in such studies; for example, the heritability of fertility traits in dairy cows is generally low, yet the coefficient of genetic variation for most traits is comparable to many other performance traits, thus supporting the observed rapid genetic gain in fertility performance in dairy populations. Empirical evidence from long-term selection studies, across a range of animal and plant species, fails to support the premise that selection will deplete genetic variability. Even after 100 yr (synonymous with 100 generations) of selection in corn for high protein or oil content, there appears to be no obvious plateauing in the response to selection. Although populations in several selection experiments did reach a selection limit after multiple generations of directional selection, this does not equate to an exhaustion of genetic variance; such a declaration is supported by the observed rapid responses to reverse selection once implemented in long-term selection studies. New technologies such as genome-wide enabled selection and genome editing, as well as having the potential to accelerate genetic gain, could also increase the genetic variation, or at least reduce the erosion of genetic variance over time. In conclusion, there is no evidence, either theoretical or empirical, to indicate that dairy cow breeding programs will be unable to adapt to evolving challenges and opportunities, at least not because of an absence of ample genetic variability.

130 ANTRAL FOLLICLE COUNTS, VULVA WIDTH, AND SERUM ANTI-MULLERIAN HORMONE CONCENTRATIONS IN BOVINE FEMALES OF THE TABAPUÃ BREED

Bovine genetic selection for fertility is difficult in part due to the low heritability of fertility traits and to the extension of the calving interval and the productive life length inherent to this species, which makes it harder to identify superior individuals from their records. In this regard, it is feasible to try to identify characteristics that are easy to detect and may be linked to superior reproductive efficiency as early as possible in females. The objective was to evaluate the possible relationships between vulva width, antral follicle counts (AFC), and the serum concentrations of anti-Mullerian hormone (AMH). Tabapuã (a Brazilian Zebu breed) heifers (n = 155) and cows (n = 422) from 4 herds were used in the study in which all antral follicles ≥3 mm were counted directly with an ultrasound unit. Follicle counts were classified into 2 classes, based on the methodology proposed by Burns et al. (2005) in dairy cattle, such that the low and intermediate AFC classes were merged into one class (low; n = 245) and the high and very high into another (high; n = 332). The vulva width was determined by measuring the distance between the lateral borders of the vulva with a digital caliper placed at a 90-degree angle from the half point of the rima vulvae. Single blood samples were collected from a subgroup of animals (n = 220) and the serum frozen (–20°C) after centrifugation for the AMH analysis, which was performed by specific bovine ELISA (Ansh Laboratories, Webster, TX, USA) test. All statistical analyses were performed with SAS (SAS Institute Inc., Cary, NC, USA). Data was submitted for analyses of variance using the PROCGENMOD procedure. Vulva width was larger (P = 0.02) in the class of animals of the high AFC (8.73 ± 0.11 cm) in comparison with those of the low AFC (8.39 ± 0.09 cm), considering the larger sample (n = 591). In the subsample (n = 220) the concentration of AMH was higher (P < 0.0001) in the high AFC class females (1.15 ± 0.07 ng mL–1; n = 95) in comparison with the low AFC class (0.50 ± 0.06 ng mL–1; n = 125). Vulva width, AFC, and AMH serum concentrations were interrelated and likely fertility indicative phenotypes under the present experimental conditions and should be further evaluated in larger samples in order to be considered in bovine genetic selection.

Genetic and phenotypic parameter on fertility traits of Red Chittagong Cattle in Bangladesh

The fertility of Red Chittagong Cattle (RCC) of Bangladesh was studied using data from 122 animals from four herds. The least squares means of female fertility traits were 1.4 ± 0.1, 72.6 ± 3.6% and 85.0 ± 2.0%, respectively, for number of services per pregnancy, first service pregnancy rate and overall pregnancy rate. The least squares mean of non-return rate to first service of bull was 58.7 ± 5.1%. The factor having a significant effect on female fertility was herd, while parity had no effect. Herd and parity of dam, season of service and sire had no effect on non-return rate to first service of bull. The heritability of fertility traits were very low: values were 0.07 ± 0.04, 0.03 ± 0.04, 0.05 ± 0.04 and 0, respectively, for number of services per pregnancy, first service pregnancy rate, overall pregnancy rate and non-return rate to first service of bull. The corresponding repeatability values were 0.18 ± 0.08, 0.08 ± 0.07, 0.13 ± 0.08 and -0.07 ± 0.02, respectively. This study reveals the fertility to be good. However, better reproductive management may enhance the overall herd fertility of RCC. DOI: http://dx.doi.org/10.3329/bvet.v29i2.14347 Bangl. vet. 2012. Vol. 29, No. 2, 78-89

Genetic correlations between body condition scores and fertility in dairy cattle using bivariate random regression models

Genetic correlations between body condition score (BCS) and fertility traits in dairy cattle were estimated using bivariate random regression models. BCS was recorded by the Swiss Holstein Association on 22,075 lactating heifers (primiparous cows) from 856 sires. Fertility data during first lactation were extracted for 40,736 cows. The fertility traits were days to first service (DFS), days between first and last insemination (DFLI), calving interval (CI), number of services per conception (NSPC) and conception rate to first insemination (CRFI). A bivariate model was used to estimate genetic correlations between BCS as a longitudinal trait by random regression components, and daughter's fertility at the sire level as a single lactation measurement. Heritability of BCS was 0.17, and heritabilities for fertility traits were low (0.01-0.08). Genetic correlations between BCS and fertility over the lactation varied from: -0.45 to -0.14 for DFS; -0.75 to 0.03 for DFLI; from -0.59 to -0.02 for CI; from -0.47 to 0.33 for NSPC and from 0.08 to 0.82 for CRFI. These results show (genetic) interactions between fat reserves and reproduction along the lactation trajectory of modern dairy cows, which can be useful in genetic selection as well as in management. Maximum genetic gain in fertility from indirect selection on BCS should be based on measurements taken in mid lactation when the genetic variance for BCS is largest, and the genetic correlations between BCS and fertility is strongest.

Genetic Correlations Among Body Condition Score, Yield, and Fertility in First-Parity Cows Estimated by Random Regression Models

Twenty type classifiers scored body condition (BCS) of 91,738 first-parity cows from 601 sires and 5518 maternal grandsires. Fertility data during first lactation were extracted for 177,220 cows, of which 67,278 also had a BCS observation, and first-lactation 305-d milk, fat, and protein yields were added for 180,631 cows. Heritabilities and genetic correlations were estimated using a sire-maternal grandsire model. Heritability of BCS was 0.38. Heritabilities for fertility traits were low (0.01 to 0.07), but genetic standard deviations were substantial, 9 d for days to first service and calving interval, 0.25 for number of services, and 5% for first-service conception. Phenotypic correlations between fertility and yield or BCS were small (–0.15 to 0.20). Genetic correlations between yield and all fertility traits were unfavorable (0.37 to 0.74). Genetic correlations with BCS were between –0.4 and –0.6 for calving interval and days to first service. Random regression analysis (RR) showed that correlations changed with days in milk for BCS. Little agreement was found between variances and correlations from RR, and analysis including a single month (mo 1 to 10) of data for BCS, especially during early and late lactation. However, this was due to excluding data from the conventional analysis, rather than due to the polynomials used. RR and a conventional five-traits model where BCS in mo 1, 4, 7, and 10 was treated as a separate traits (plus yield or fertility) gave similar results. Thus a parsimonious random regression model gave more realistic estimates for the (co)variances than a series of bivariate analysis on subsets of the data for BCS. A higher genetic merit for yield has unfavorable effects on fertility, but the genetic correlation suggests that BCS (at some stages of lactation) might help to alleviate the unfavorable effect of selection for higher yield on fertility.

Relationship of Fertility to Milk Yield in Swedish Cattle

Data consisted of 48,830 and 21,136 records of Swedish Red and White and Swedish Black and White cattle. Fertility in virgin heifers and in first lactation cows was measured by first service pregnancy rate and number of services per pregnancy. Production trait considered was FCM produced in first 100 d of lactation. The heritabilities for fertility traits in virgin heifers and first lactation cows were about .05 in both breeds. The genetic correlations between fertility measures within parity were close to one in both breeds, suggesting that these were measures of the same trait. The genetic correlations between fertility in virgin heifer and in first lactation were about .88 for Swedish Red and White breed and between .6 and .7 for Swedish Black and White breed. The association between fertility and production in first lactation cows was antagonistic, with genetic correlations between first service pregnancy rate and milk yield of –.13 and –.32 for Swedish Red and White and Swedish Black and White breed, respectively. The association between first service pregnancy rate in virgin heifers and milk yield in first lactation was also antagonistic, with genetic correlations of –.14 and –.41 for Swedish Red and White and Swedish Black and White breed, respectively.

Relationships Between Reproduction Traits, Age and Body Weight at Calving, and Days Dry in First Lactation Ayrshires and Holsteins

Individual cow test day records collected between December 1979 and June 1986 were used to calculate measures of reproductive performance, age and weight at calving, and days dry for 7824 Ayrshire and 79,755 Holstein cows in first lactation. Separate analyses by breed were carried out according to a multiple-trail mixed model. Sixty-two Ayrshire and 369 Holstein sires were treated as random in the analyses. Ayrshires were, on average, older and lighter at calving than Holsteins, but the breeds differed little in reproduction measures and days dry. Heritabilities of fertility traits, days to first breeding, days open, and services per conception were all less than .015 in the multi-trait analyses. With the exception of body weight, heritability estimates for the other traits were less than .05. Phenotypic correlations between traits were almost identical for the two breeds, and genetic correlations tended to be similar. Exceptions involved the traits days to first breeding and services per conception, but heritabilities of these traits were close to zero (<.008) in Ayrshires. Fertility traits were positively correlated genetically. Genetic correlations between days open and both age and body weight at calving were small. The genetic correlation between age and weight at calving was −.90 and −.68 in Ayrshires and Holsteins, respectively. Genetic correlations between days dry and all traits except body weight were moderate and positive.