Estimation of genetic and phenotypic relationships between age at first calving and productive performance in Iranian Holsteins

Genetic parameters for milk yield and reproductive traits in Honduran Holstein cattle

The aim of this study was to estimate the (co)variance components and genetic parameters for milk yield adjusted to 305d (MY305), calving-to-conception interval (CCI), number of services per conception (NSC) and calving interval (CI) of Honduran Holstein cows, by fitting a bivariate animal model using Maximum Restricted Likelihood procedures. Model included the fixed effects of calving number, the contemporary calving group (farm-season-year of calving and the cow age as covariate). The estimated means and standard deviations for MY, CCI, NSC and CI were, 5098.60 ± 1564.32 kg, 168.27 ± 104.71 days, 2.46 ± 1.69 services, and 448.73 ± 109.16 days, respectively; and their estimated heritabilities were 0.21 ± 0.05, 0.03 ± 0.028, 0.02 ± 0.024 and 0.06 ± 0.04, respectively. The genetic correlations between MY305 and CCI, NSC and CI were positive and antagonist, with values of 0.64 ± 0.52, 0.99 ± 0.56, and 0.32 ± 0.24 respectively. Even though moderate to low heritability was estimated for MY305, systematic selection for milk yield, with a reduction in reproductive efficiency, if considered as the only selection criterion is important to be considered. By including reproductive traits and considering permanent environment effects into the breeding program, might yield a slow, but constant and permanent improvement over time.

Relationship between Milk Protein Polymorphism and Selected Cows' Reproductive Indices

This research sought to determine the effect of selected milk protein polymorphisms on the reproduction parameters of 598 black and white Polish Holstein-Friesian cattle. The analyzed genes were kappa-casein (CSN3) and beta-lactoglobulin (BLG). The following reproductive indexes were selected: the age at first calving, the interpregnancy period, the calving interval, and the insemination index. The influence of the identified genotypes on the course of parturition in cows was also analyzed. Source data were collected for each cow from the beginning of the herd life and reproduction to its culling from the herd or the end of its third lactation. Data on the age at first calving, the amount of semen portions for artificial insemination (insemination index), the interpregnancy period, and the calving interval for each cow were also collected. A contingency analysis was performed through contingency tables using a Pearson's chi-squared test for each CSN3 and BLG genotype. The results show that the BB genotype of the kappa-casein gene was associated with the most favorable values of reproductive indicators. In the case of the calving interval, the values were significantly more favorable than those of other genotypes (p ≤ 0.05). No effect of beta-lactoglobulin polymorphism on the analyzed reproductive indices was observed. On the other hand, in the case of the interpregnancy period, significant statistical differences were obtained between the AA and BB genotypes. The analyzed kappa-casein and beta-lactoglobulin genotypes did not significantly influence the course of parturition in cows. To conclude, the genotype polymorphism BB CSN3 is the most favorable for the performance of the cows in the examined herd.

Association between age at first calving, first lactation traits and lifetime productivity in Murrah buffaloes

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Somatic cell counts, reproduction indicators, and technical efficiency in milk production: A stochastic frontier analysis for Spanish dairy farms

Health and reproductive conditions affect milk yields in dairy cows and may lead to differences in technical efficiency across farms. To investigate this, we created a novel panel data set of 197 dairy farms in northern Spain observed over the period 2006-2014 by combining information from 2 different sources and including data on production variables, somatic cell count, and reproduction indicators, as well as a genetic index. We used these data to estimate a stochastic production frontier where the somatic cell count, age at first calving, and calving interval are included as determinants of technical efficiency. Higher somatic cell count, greater age at first calving, and longer calving intervals were found to decrease technical efficiency, translating into significant losses in profits which we quantify through a simulation exercise. We also quantified the effect of genetic selection on profits, taking into account not only its direct effect on productivity but also its indirect effect through reduced technical efficiency due to the effect of genetic selection on the health and reproduction variables.

UFL1 Alleviates LPS-Induced Apoptosis by Regulating the NF-κB Signaling Pathway in Bovine Ovarian Granulosa Cells

Ubiquitin-like modifier 1 ligating enzyme 1 (UFL1) is an E3 ligase of ubiquitin fold modifier 1 (UFM1), which can act together with its target protein to inhibit the apoptosis of cells. Lipopolysaccharides (LPS) can affect the ovarian health of female animals by affecting the apoptosis of ovarian granulosa cells. The physiological function of UFL1 on the apoptosis of bovine (ovarian) granulosa cells (bGCs) remains unclear; therefore, we focused on the modulating effect of UFL1 on the regulation of LPS-induced apoptosis in ovarian granulosa cells. Our study found that UFL1 was expressed in both the nucleus and cytoplasm of bGCs. The results here demonstrated that LPS caused a significant increase in the apoptosis level of bGCs in cows, and also dramatically increased the expression of UFL1. Furthermore, we found that UFL1 depletion caused a significant increase in apoptosis (increased the expression of BAX/BCL-2 and the activity of caspase-3). Conversely, the overexpression of UFL1 relieved the LPS-induced apoptosis. In order to assess whether the inhibition of bGCs apoptosis involved in the nuclear factor-κB (NF-κB) signaling pathway resulted from UFL1, we detected the expression of NF-κB p-p65. LPS treatment resulted in a significant upregulation in the protein concentration of NF-κB p-p65, and knockdown of UFL1 further increased the phosphorylation of NF-κB p65, while UFL1 overexpression significantly inhibited the expression of NF-κB p-p65. Collectively, UFL1 could suppress LPS-induced apoptosis in cow ovarian granulosa cells, likely via the NF-κB pathway. These results identify a novel role of UFL1 in the modulation of bGC apoptosis, which may be a potential signaling target to improve the reproductive health of dairy cows.

Associations between age at first calving and subsequent lactation performance in UK Holstein and Holstein-Friesian dairy cows

Lactation records from 396,534 pedigree Holstein and Holstein-Friesian primiparous cows from 6,985 UK milk recorded herds, calving for the first time during the period between the 1^st of January 2006 and the 31^st of December 2008, were examined in order to determine the associations between age at first calving (AFC) and subsequent production, udder health, fertility and survivability parameters. Heifers were grouped by AFC into single month classes ranging from 21 to 42 months. Mixed effects multivariable regression modelling was used for data analysis. Mean and median AFC were 29.1 and 28 months respectively. Within the study, only 48,567 heifers (12.3% of the studied population) calved for the first time at 24 months of age or younger. 162,157 heifers (40.9%) were 30 months or older at their first calving. An increased AFC was associated with increased first lactation milk, fat and protein yields. The lowest predicted mean 305-day yield (6,617kgs; 95% confidence interval (CI): 6,546–6,687 kgs) was recorded for the 21 month AFC class, significantly lower than any other class. The 36 month AFC class had the highest predicted mean (7,774 kgs; 95% CI: 7,737–7,811 kgs). However, an increased AFC was also associated with increased calving interval and increased first lactation somatic cell count (SCC). Animals calving at 21 months had a predicted mean lactation SCC of 72,765 (95% CI: 68427–77378). Animals calving at 36 months of age had a predicted mean lactation SCC of 86,648 (95% CI: 84,499–88,853). Importantly, an increased AFC was also associated with decreased lifetime daily milk yield and decreased likelihood of calving for a second successive time. Animals calving at 22 months of age had a predicted mean daily lifetime milk yield of 15.24 kgs (95% CI: 15.06–15.35); animals calving at 36 months of age had a predicted mean daily lifetime milk yield of 12.83 kgs (95% CI: 12.76–12.91). Our results highlight the importance of achieving a lower age at first calving which was here associated with improved udder health, increased lifetime daily milk yield, improved reproductive performance and increased likelihood of calving for a second time.

Bayesian estimates of genetic relationship between calving difficulty and productive and reproductive performance in Holstein cows

The objective of present study was to estimate genetic correlations between calving difficulty and productive and reproductive traits in Iranian Holsteins. Calving records from the Animal Breeding Center of Iran, collected from 1991 to 2011 and comprising 183 203 first-calving events of Holstein cows from 1470 herds were included in the dataset. Threshold animal models included direct genetic effect (Model 1) or direct and maternal genetic effects with covariance between them (Model 2) were fitted for the genetic analysis of calving difficulty. Also, linear animal models including direct genetic effect were fitted for the genetic analysis of productive and reproductive performance traits. A set of linear-threshold bivariate models was used for obtaining genetic correlation between calving difficulty and other traits. All analyses were implemented by Bayesian approach via Gibbs sampling methodology. A single Gibbs sampling chain with 300 000 rounds was generated by the TM program. Posterior mean estimates of direct heritabilities for calving difficulty were 0.056 and 0.066, obtained from different models. Also, posterior mean estimate of maternal heritability for this trait was 0.018. Estimate of correlation between direct and maternal genetic effects for calving difficulty was negative (–0.44). Posterior mean estimates of direct heritabilities for milk yield, fat yield, protein yield, days from calving to first service, days open and first calving interval were 0.257, 0.188, 0.235, 0.034, 0.042 and 0.050 respectively. The posterior means of direct genetic correlation between calving difficulty and milk yield, fat yield, protein yield, days from calving to first service, days open and first calving interval were low and equal to –0.135, 0.030, –0.067, –0.010, –0.075 and –0.074 respectively. The results of the current study indicated that exploitable genetic variation in calving difficulty, productive and reproductive traits could be applied in designing future genetic selection plans for Iranian Holsteins.

Genetic perspective of milk yield persistency in the first three lactations of Iranian buffaloes (Bubalus bubalis)

The objectives of this study were to estimate the genetic parameters and genetic trends for different measures of persistency (PM) for milk yield in Iranian buffaloes using a random regression test day model. Test day records of the first three lactations of buffaloes within 715 herds comprising 43 014, 38 941 and 33 937 records, respectively, were obtained from the Animal Breeding Center of Iran during 1992 to 2012. Legendre polynomial functions were chosen to fit the lactation curves in the framework of a random regression test day model for estimating (co)variance components. Three measures of persistency were modified based on the lactation curve conditions of buffaloes: (1) The average of estimated breeding values (EBVs) for test day milk yields from day 226 to day 270 as a deviation from the average of EBVs from day 44 to day 62 (PM1), (2) A summation of contribution for each day from day 53 to day 247 as a deviation from day 248 (PM2), (3) The difference between EBVs for day 257 and day 80 (PM3). The highest heritability estimates were observed for PM2 over the first three lactations (0·29, 0·80 and 0·42, respectively). Estimates of genetic correlations between persistency measures and milk yield varied from -0·48 to 0·29 (first lactation), from -0·12 to 0·48 (second lactation), and from -0·62 to 0·63 (third lactation). Estimate of genetic trend for first lactation PM2 was negative (-0·0088 ± 0·0043; P < 0·05). It is essential to include milk yield persistency in the breeding goal of Iranian buffaloes along with other important traits such as milk yield or reproductive traits.

Effect of dystocia on subsequent reproductive performance and functional longevity in Holstein cows

The objective of this study was to evaluate the effect of dystocia on the reproductive performance and functional longevity in Iranian Holsteins. Data consisted of 1 467 064 lactation records of 581 421 Holstein cows from 3083 herds which were collected by the Animal Breeding Center of Iran from April 1987 to February 2014. Reproduction traits in this study included interval from first to second calving, days open and days from first calving to first service. The generalized linear model was used for the statistical analysis of reproductive traits. Survival analysis was performed using the Weibull proportional hazards models to analyse the impact of dystocia on functional longevity. The incidence of dystocia had an adverse effect on the reproductive performance of dairy cows. Therefore, reproductive traits deteriorated along with increase in dystocia score (p < 0.05). The culling risk was increased along with increase in the score of dystocia (p < 0.0001). The greatest culling risk was observed in primiparous cows, small herds and low-yielding cows (p < 0.0001). Also, the lowest culling risk was found for cows calving at the youngest age (<27 months), and cows with age at first calving >33 months had the greatest risk (p < 0.0001). The results of current study indicated that dystocia had important negative effects on the reproductive performance and functional longevity in dairy cows, and it should be avoided as much as possible to provide a good perspective in the scope of economic and animal welfare issues in dairy herds.