Anti-Müllerian hormone (AMH) is produced by granulosa cells of early-antral follicles found on the ovary. After production, it enters circulation and can be detected from a blood sample with an ELISA. Multiple works have found that circulating AMH is a reliable marker of the antral follicle population (AFP) of an animal as well as directly correlated to an animal's response to a superovulation protocol. Research has also found high repeatability within an animal's oestrous cycle. Further use of AMH may be valuable as a reproductive management tool, based on previous research linking productive life with circulating AMH in heifers and success to various breeding protocols by AMH concentration. The aim of this review was to summarize previous works describing basic function of AMH as well as explore recent research examining AMH as a reproductive tool and measurement of fertility in dairy animals. How to cite this article: Alward KJ, Bohlen JF. Overview of Anti-Müllerian hormone (AMH) and association with fertility in female cattle. Reprod Dom

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Graphical Abstract Summary: Ultrasonic determination of antral follicle count (AFC) is used to classify animals into high or low AFC categories. These categories have a wide range and animals classified as low on one study may be considered high by another study based on the population. Associations with high AFC cows include greater follicular vasculature, blastocyst rates, hatched blastocyst rates, 12-d embryonic cell growth and cleavage rates, along with a lower number of embryonic apoptotic cells. More high AFC cows cycled as heifers at 15 months, had a greater pregnancy rate and conception rate and progesterone concentration after breeding, and fewer days to conception. However, other studies have found that low AFC animals had greater pregnancy and conception rates and progesterone concentration after breeding compared with high AFC cows. Low AFC cows also showed greater preovulatory follicle blood flow, greater blastocyst cell number, and greater area of the corpus luteum.

Insufficient consumption of colostrum and/or intake of poor-quality colostrum reduces thriftiness and survival of dairy calves. Additionally, heat stress during gestation of primiparous Holstein cows can impact hormone synthesis, leading to decreased colostrum and milk production. Previous research has primarily focused on Holstein cows who have a larger frame compared to other breeds. It is possible heat stress may impact Jersey cow colostrum production differently. Therefore, the objective of this research was to determine the relationship between temperature-humidity index (THI) and colostrum volume and quality in Jersey cows. Colostrum data was collected from Jersey cows (n = 75) from three farms and compared to the average THI values during the dry period. Colostrum data included volume, Brix score, fat, true protein (TP), solids non-fat (SNF), lactose, somatic cell count (SCC), and urea. Daily air temperature and humidity records were determined via local weather stations and used to calculate THI values. These values were averaged for the far-off and close-up periods. The data were analyzed separately for each farm using linear regression models in R version 1.3.1073. Covariates included season, dry period length, date of colostrum collection, and parity. Close-up and far-off THI tended to predict an increased volume (β=0.3656; P = 0.0724) and somatic cell count (β=82.07; P = 0.0964) for Farm 1. Far-off THI was a significant predictor for Brix for Farm 2 (β=0.2482; P ≤ 0.01) and Farm 3 (β=-0.1762; P ≤ 0.01) and increased Brix score in Farm 2 but decreased it in Farm 3. THI was not a significant predictor for any other colostrum values. Based on these results, we suggest that an increased THI during the far-off period potentially increases Brix score without compromising other values. However, more research is needed to further investigate the effects of the close-up period on volume and of covariates on other values.

Understanding the composition and structure of the fecal microbial community may provide insight into bacterial adaptation to dietary changes in cattle. The aim of this study was to determine relationships among the fecal microbiome, residual feed intake (RFI) and residual net energy intake (REI) with diets varying in crude protein (CP). Four Holstein lactating cows (806 ± 38 kg of BW) were randomly assigned to one of two treatments (LOW: 13.2% and BASE:16.6% CP) in a crossover design (2 periods of 18 d each). Cows were 260 ± 62 days in milk (DIM) and averaged 26.5 ± 12.0 kg milk yield (MY). Diets were formulated to meet animal needs. Individual feed intake measured by a Calan Gate system was used to calculate daily dry matter intake (DMI). BW, MY and milk components were also measured daily. A linear mixed model with repeated measurements over time was used to evaluate diet effect on DMI, MY, RFI and REI in SAS. Individual fecal samples were collected at the end of each period and extracted DNA was subject to 16S rRNA gene deep amplicon sequencing. Operational Taxonomic Units (OTU) were obtained using ≥97% similarity (SILVA database) and microbial community structure was assessed using alpha and beta diversity measures. No significant differences in phenotypic variables evaluated were observed between treatments or periods. We identified 927 concordant OTU among all cows, with 505 novel OTU identified in BASE cows and 403 in LOW cows. Microbial community structure was similar between treatments and feed efficiency measures. One OTU class, Erysipelotrichi, increased in abundance (P = 0.014) in BASE compared to LOW treatment. Findings reflect previous literature in which Erysipelotrichi was associated with high energy or high fat diets. Although no differences were observed in the phenotypic measurements between treatments, metagenomics analyses indicated differences in specific fecal microbial abundance.

Exposing Holstein dry cows to short-day (SD) photoperiod of 8 hours per day can improve milk production post-calving by 3.2 kg per day, compared to cows exposed to long-day (LD) photoperiod of 16 hours per day during the same period. To date, no studies have evaluated the effect of altered photoperiod during the dry period on milk production in Jersey cows. Our objective was to study the effect of LD and SD during the dry period on milk production in both breeds. Holstein and Jersey cows (n=33) dried off 60 days prior to their due date were exposed to either SD (n=9 Holstein, n=8 Jersey) or LD (n=8 Holstein, n=8 Jersey) at 18.3 °C until calving. After calving, cows returned to ambient photoperiod and milk data was collected for 15 weeks. Lactation number, replicate, dry period feed intake and days of treatment were recorded. Data were analyzed using PROC MIXED in SAS 9.4. Overall average milk production differed by breed (P< 0.01), with Holsteins producing more (72.9 ± 6.2 kgs) than Jerseys (66.1 ± 7.3 kgs). Treatment differed (P=0.02) with SD cows producing more milk (71.0 ± 6.9 kgs) than LD cows (68.1 ± 6.7 kgs). Treatment and breed interaction significantly differed. Long-day Holsteins produced 73.9 kgs ± 6.2 kgs which was not different (P >0.10) from SD Holsteins (72.1 ± 6.4 kgs). Neither LD nor SD Holsteins differed significantly (P=0.16, P=0.60) from SD Jerseys which produced 70.0 ± 7.4 kgs. Long-day Jerseys averaged the least milk at 62.3 ± 7.3 kgs which was significantly different from all other groups (P< 0.01). This data suggests Jerseys’ milk production responds similarly to previous reported Holstein data. Factors causing the unexpected Holstein data could be elevated temperature-humidity index values post-calving, despite industry standard heat abatement.

The objective of this study was to examine the impact of a bovine respiratory disease complex (BRDC) vaccine with a temperature‐sensitive modified live vaccine (MLV) infectious bovine rhinotracheitis (IBR) component on oestrous cycle parameters and the follicular pool. Twenty‐four Holstein heifers (12.4 ± 0.5 months) previously calfhood vaccinated with an IBR MLV component were enrolled in two replicates (Spring; n = 10 and Fall; n = 14) and were blocked by pre‐vaccination bovine viral diarrhoea (BVD) serum neutralizing (SN) titres. Upon enrolment, heifers were oestrous synchronized with sampling beginning at detected oestrus. At their second heat, heifers were vaccinated with a BRDC calfhood vaccine with a MLV (MLV; n = 12) or killed (K; n = 12) IBR component and sampled for two additional cycles. Serum samples for oestrogen (E2) and progesterone (P4) as well as ultrasound data of ovarian structures were collected every other day. Serum samples for anti‐Müllerian hormone (AMH) were collected at oestrus and mid‐cycle for each cycle, and serum for titres was collected prior to and following vaccination. Data were analysed with the PROC MIXED and GLM procedures of SAS. There was no difference in pre‐ or post‐vaccination titres between MLV and K heifers (p > .5). Vaccination had no impact on P4 concentrations, P4 area under the curve, luteal tissue area, peak E2 production or oestrous cycle length (p > .05). Cycle number did impact AMH concentration (p < .05). In MLV heifers, AMH concentration was highest in cycle 1 (p < .05) while cycles 2 and 3 did not differ (p > .05). This was also true for the K heifers in the Fall replicate (p < .05). Within cycle 2, AMH concentrations were numerically lower between vaccine types (K = 308.22 ± 33.3 pg/ml, MLV = 181.13 ± 32.9 pg/ml; p > .05). Although no differences were seen in overall cycle parameters, differences in AMH concentrations may indicate a reduction of the follicular pool following vaccination and requires further investigation.

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