Associations between postpartum phenotypes, cow factors, genetic traits, and reproductive performance in seasonal-calving, pasture-based lactating dairy cows

Abstract

The objective of this study was to evaluate associations between corpus luteum (CL) status, uterine health, body condition score (BCS), metabolic status, parity, genetic merit for fertility traits, and reproductive performance in pasture-based dairy cows managed for seasonal reproduction. First-and second-lactation (n = 2,600) spring-calving dairy cows from 35 dairy farms located in Ireland were enrolled in the study. Farms were visited every 2 wk, and animals that were at wk 3 (range: 14-27 d in milk) and wk 7 (range: 42-55 d in milk) postpartum were examined. Body condition score was measured using a 1-to-5 scale in 0.25-point increments. Transrectal ultrasound examination was performed at wk 3 and 7 postpartum to determine presence or absence of CL and ultrasound reproductive tract score (scale of G1-G4). Blood samples were collected at each visit, and the concentrations of glucose, β-hydroxybutyrate (BHB), and fatty acids (FA) were analyzed using enzymatic colorimetry. Animals were grouped into 3 BCS categories [low (≤2.5), target (2.75-3.25), and high (≥3.5)], 2 CL categories (present or absent), 2 uterine health status categories (normal or abnormal), and 3 metabolic status categories [good (high glucose, low FA and BHB), poor (low glucose, high FA and BHB), and moderate (all other combinations)]. Fisher's exact test was used to test for associations between variables and was supplemented by logistic regression. More cows with a CL at wk 7 were served during the first 21 d of the breeding period compared with cows without a CL. Cows classified as having a uterine score of G3 or G4 at wk 3 and 7 had lower odds of pregnancy establishment during the breeding period compared with animals with a uterine score of G1 or G2. Animals with low BCS at wk 7 had lower odds of pregnancy establishment than cows with a target BCS. Cows classified as having good metabolic status at both wk 3 and wk 7 had greater odds of pregnancy establishment during the first 21 d of the breeding season than those classified as having poor metabolic status. Overall, primiparous cows had greater reproductive performance than second-parity cows. Animals in the quartiles with the best predicted transmitting ability for survival and calving interval had better reproductive performance compared with animals in the other quartiles. Cows that had better genetic merit for fertility traits and good metabolic status, achieved target BCS, and had a favorable ultrasound reproductive tract score and a CL present at wk 7 postpartum had superior reproductive performance.

Microflora in the Reproductive Tract of Cattle: A Review

“…For example, according to a recent study, exposure to these pathogenic microbes might result in reduced uterine health, which may also have a significant effect on subsequent reproductive metrics as currently reported in pasture-based Holstein-Friesian cows [57]. Likewise, findings from a current study clearly emphasize a strong association between uterine health, the status of the corpus luteum, the fertility sub-index, and reproductive function in lactating dairy cows [58]. Interestingly, it is noteworthy that a similar relationship was not observed during lactation in the dairy cow fertility sub-index, as found in another recent study by Rojas and coworkers [59].…”

Reproductive performance of early- and late-calving dairy cows artificially inseminated after ovulation synchronization and estrous resynchronization or artificially inseminated after observed estrus

“…It is likely that fewer LC cows had resumed estrous cyclicity and expression compared with EC cows. The greater pregnancy rates in the EC cows compared with the LC cows were also likely due to a greater proportion of the EC cows being at target BCS and having clear vaginal mucus at 10 d before MSD, in agreement with Rojas Canadas et al (2020). Reduced pregnancy rates in latecalving, pasture-based cows were also reported by Escalante et al (2013) andRojas Canadas et al (2020).…”

Associations between postpartum fertility phenotypes and genetic traits in seasonal-calving, pasture-based lactating dairy cows

“…Cows with an abnormal UHS at wk 3 and 7 were more likely not to have at least 1 CL at wk 3 and 7 postpartum than cows with a normal UHS. In the companion paper to the present study (Rojas Canadas et al, 2020), we reported that CL status at wk 3 was not strongly associated with subsequent reproductive performance, but that there was a favorable association at wk 7. Furthermore, we found associations between UHS at wk 3 and 7 and reproductive performance (Rojas Canadas et al, 2020).…”

“…In the companion paper to the present study (Rojas Canadas et al, 2020), we reported that CL status at wk 3 was not strongly associated with subsequent reproductive performance, but that there was a favorable association at wk 7. Furthermore, we found associations between UHS at wk 3 and 7 and reproductive performance (Rojas Canadas et al, 2020). Because of the strong association between CL status and uterine health observed in the present study, early resumption of cyclicity is a favorable phenotype for subsequent reproductive performance.…”

“…It has been reported previously that BCS at parturition, nadir BCS, BCS at AI (Hoedemaker et al, 2009;Roche et al, 2009), number of cycles before first insemination (Darwash et al, 1997), uterine health (Sheldon et al, 2009;Rojas Canadas et al, 2020), metabolic status (Lucy et al, 2014;Rojas Canadas et al, 2020), parity (Tanaka et al, 2008;Rojas Canadas et al, 2020), and genetic merit for fertility traits (Butler, 2014;Butler and Moore, 2018) are all factors that affect reproductive performance in lactating dairy cows. Nevertheless, most of the preceding studies have Rojas Canadas et al: CL STATUS, UTERINE HEALTH, BIOENERGETIC STATUS, AND GENETIC TRAITS Figure 1.…”