Reproductive Performance Of Heifers Research Articles

A randomized trial on the effects of heat abatement during the pre-weaning phase on growth and reproductive performance of heifers and health, reproductive and productive performances of cows

Evaluation of heat stress abatement for pre-weaned dairy calves is a rare endeavor. We aimed to assess the impacts of cooling the environment of pre-weaned calves through ceiling fans on their performance after weaning and during their first lactation. We randomly assigned female Holstein calves to one of two treatment at birth (day 0): individual frame-wire hutches in a non-cooled barn ("SH", n = 125) and individual frame-wire hutches in a barn equipped with ceiling fans ("SHF", n = 101). Calves were housed under the same barn, with treatments applied in three alternating sections. Ceiling fans (2.1 m in diameter) were positioned 4.1 m from the ground and 7.6 m apart (center-to-center). Shade cloths were used to separate the sections designated for the SH and SHF treatments. Post-weaning, heifers were commingled. We recorded body weight (BW) and average daily gain (ADG) at weaning, 5, 7, and 10 mo of age. Pregnancy to first artificial insemination (P/1AI), hazard of pregnancy, and the hazard of commencing the first lactation are reported. Body weight at first calving, P/1AI, hazard of pregnancy, and milk yield in the first lactation are reported. No differences in BW (5 mo: SH = 162.9 ± 1.6 kg vs. SHF = 162.3 ± 1.6 kg; 7 mo: SH = 200.8 ± 2.2 kg vs. SHF = 201.1 ± 2.3 kg; 10 mo: SH = 300.5 ± 2.6 kg vs. SHF = 300.0 ± 2.8 kg) and ADG (SH = 0.94 ± 0.02 kg/d, SHF = 0.94 ± 0.02 kg/d) from 5 to 10 mo of age were detected. Treatment did not affect P/1AI (SH = 53.5 %, SHF = 45.9 %) and hazard of pregnancy [SH = referent, SHF – adjusted hazard ratio (AHR) = 0.87 (95 % CI = 0.65, 1.18)], but heifers in the SHF treatment were less likely to initiate the first lactation (76.2 % vs. 86.4 %). Body weight at calving (SH = 612.4 ± 5.3 kg, SHF = 618.2 ± 5.9 kg) and milk yield (SH = 39.0 ± 0.48 kg/d, SHF = 38.3 ± 0.57 kg/d) were not different, but the SHF treatment resulted in lower P/1AI (38.4 % vs. 51.4 %) and hazard of pregnancy (AHR = 0.68, 95 % CI = 0.49, 0.93) and fewer cows starting their second lactation (57.4 % vs. 72.8 %). In our experiment, providing cooling through ceiling fans during the pre-weaning phase had a negative impact on the reproductive performance of Holstein cows during their first lactation.

Development and evaluation of a multiplex polymerase chain reaction in real-time for differential diagnosis of Moraxella-induced keratoconjunctivitis in livestock.

Infectious bovine keratoconjunctivitis (IBK) is a prevalent ocular disease that affects livestock, leading to substantial economic losses due to reduced production and culling of infected animals. Moraxella spp. is common bacterial pathogens that can cause keratoconjunctivitis in livestock. Therefore, rapid and accurate diagnosis is crucial for effective treatment and disease control. This study aimed to develop a multiplex real-time polymerase chain reaction (mRT-PCR) assay for the detection and differentiation of Moraxella bovoculi, Moraxella ovis, and Moraxella bovis. Three reference strains of Moraxella as positive controls and 36 lacrimal swab samples collected from cattle were used to evaluate the developed mRT-PCR assay DNA extraction that was performed using the RIBO-sorb DNA/RNA extraction kit. Primers and probes were designed using the SpeciesPrimer pipeline. The annealing temperature, primer and probe concentrations, and sensitivity and specificity of the assay were optimized. An mRT-PCR assay was developed to detect pathogens associated with IBK in cattle on the basis of optimized parameters. The specificity and sensitivity of this assay were confirmed using samples containing individual pathogens (O - M. ovis, B - M. bovis, and BO - M. bovoculi), combinations of two pathogens (O-B, B-BO, and O-BO), and when the DNA of all three pathogens was present in a single reaction (O-B-BO). The analytical sensitivity of mRT-PCR for detecting M. ovis and M. bovoculi DNA was 21 copies or 50 fg per reaction, whereas that for M. bovis was 210 copies or 500 fg per reaction. In addition, this assay has been tested on samples isolated from the affected eyes of cattle in the Akmola region of the Republic of Kazakhstan. For the first time in the Republic of Kazakhstan, the proposed mRT-PCR assay for the simultaneous detection of three Moraxella spp. pathogens has been developed. This assay exhibits the required specificity and high sensitivity for m RT-PCR, facilitating the timely implementation of effective measures for disease control and the prevention of economic losses. These losses are linked to a reduction in livestock breeding value, a reduction in meat and milk production, a reduction in the reproductive performance of heifers, resulting in fewer offspring, as well as costs related to the treatment of affected animals.

The association between insemination eligibility and reproductive performance of nulliparous heifers on subsequent body weight and milk production of primiparous Holstein cows

The objective of this retrospective cohort study was to determine the association between insemination eligibility and reproductive performance of nulliparous heifers with subsequent body weight (BW) at 30 d in milk (DIM) and milk production at wk 4, 8, and 12 of lactation of primiparous cows. The final data set included 1,849 primiparous Holstein cows from a commercial dairy herd. Data extracted from a commercial dairy herd management software program included parent average predicted transmitting abilities (PTA), bovine respiratory disease (BRD) incidence, pregnancies per artificial insemination (P/AI) at first insemination as nulliparous heifers, BW at 30 DIM, percent mature body weight (%MBW), and mean weekly milk production at wk 4, 8, and 12 of lactation. Heifers were eligible for first insemination at 380 d of age and were detected in estrus and artificially inseminated with sexed semen. Quartiles based on BW at 30 DIM and %MBW were created in ascending order as follows: Q1 (lightest; n = 462), Q2 (light-moderate; n = 456), Q3 (moderate; n = 472), and Q4 (heaviest; n = 459). Only Q3 and Q4 cows achieved ≥85% MBW postcalving based on the herd MBW of 686.2 kg. The incidence of BRD during heifer development was greatest for Q1 cows, and Q1 cows had fewer days on feed as heifers than Q4 cows, resulting in a shorter growth period to achieve ≥85% MBW postcalving. Overall, Q1 cows had a greater PTA for daughter pregnancy rate and heifer conception rate than Q4 cows, which was associated with approximately 26 percentage points more P/AI at first insemination as heifers for Q1 than for Q4 cows. Finally, Q1 cows yielded approximately 5 kg per cow/d less milk than Q4 cows. Thus, insemination eligibility and reproductive performance of heifers, calfhood BRD incidence, and genetic potential for reproductive performance were associated with BW at 30 DIM and milk production at wk 4, 8, and 12 of lactation of primiparous cows.

Review: Gestational and postnatal nutritional effects on the neuroendocrine control of puberty and subsequent reproductive performance in heifers.

Pubertal attainment is an intricate biological process that involves maturation of the reproductive neuroendocrine axis and increased pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone. Nutrition is a critical environmental factor controlling the timing of puberty attainment. Nutrient restriction during early postnatal development delays puberty, whereas increased feed intake and adiposity during this period hasten pubertal maturation by imprinting the hypothalamus. Moreover, the dam's nutrition during gestation can program the neuroendocrine system in the developing fetus and has the potential to advance or delay puberty in the offspring. Leptin, a hormone produced primarily by adipose cells, plays an important role in communicating energy status to the brain and regulating sexual maturation. Leptin's regulation of GnRH release is mediated by an upstream neuronal network since GnRH neurons do not contain the leptin receptor. Two groups of neurons located in the arcuate nucleus of the hypothalamus that express neuropeptide Y (NPY), an orexigenic peptide, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide, are central elements of the neural circuitry that relay inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Moreover, KNDy neurons, neurons in the arcuate nucleus that co-express kisspeptin, neurokinin B (NKB), and dynorphin, also play a role in the metabolic regulation of puberty. Our studies in beef heifers demonstrate that increased rates of BW gain during early postweaning (4-9 mo of age) result in reduced expression of NPY mRNA, increased expression of proopiomelanocortin and kisspeptin receptor mRNA, reduced NPY inhibitory inputs to GnRH neurons, and increased excitatory αMSH inputs to KNDy neurons. Finally, our most recent data demonstrate that nutrition of the cow during the last two trimesters of gestation can also induce transcriptional and structural changes in hypothalamic neurocircuitries in the heifer progeny that likely persist long-term after birth. Managerial approaches, such as supplementation of the dam during gestation (fetal programming), creep feeding, early weaning, and stair-step nutritional regimens have been developed to exploit brain plasticity and advance pubertal maturation in heifers.

Efficacy Evaluation of an Organic Trace Mineral (OTM) Powder Formulation on the Reproductive Performance of Heifers

Nutritional management during gestation is essential for optimizing the efficiency andprofitability of livestock production systems. Changes in maternal nutritional status may lead to such adaptations which can permanently alter the parameters of growth, physiology, and metabolism of offspring. Supplementation of essential trace minerals to pregnant cows, which are inadequate in diet to suffice the health requirement of these animals may enhance progeny performance and their health. This study investigated the impacts of supplementing Organic Trace Mineral (OTM) powder formulation on the reproductive health of heifers. The feeding experiment was performed in the Arvind Dairy Farm, Haryana, India with two groups of 6 pregnant heifer cows each (control: T0 and experimental: T1) between January and September 2022. Both groups were fed rations adjusted with regard to body weight of animals. Group T1 fed OTM at 10 gm/animal/day for 28-days and group T0 was provided access to standard basal diet only. Experimental model investigated reproductive health of heifers for the physical and clinical parameters of estrus exhibition, duration of estrus and conception rate in comparison to controls. Significant improvement observed in the physical and clinical parameters of estrus exhibition in treatment group (T1) compared to control group (T0), higher conception rate in T1 (84%) in comparison to T0 (66%); and improvement in estrus duration in T1 (27 ± 1.53 h) as compared to the T0 (31.5 ± 2.81 h), indicating supplementation of OTM to pregnant heifers has significant influence in improving reproductive health in heifers.

Assessment of Plasma Oxidative Stress Biomarkers and Metabolic Parameters of Dairy Heifers: Relationship with Success at First Service


 First insemination success is considered as good indicator of heifer fertility to ensure renewal of dairy herds. The objective of this study was to determine the relationship between first insemination success and biomarkers of oxidative stress (OS). A total of 25 heifers were divided into two groups according to their success at first insemination: group FS+ (heifers that were pregnant at first service, n = 14) and group FS- (heifers that were not pregnant at first service, n = 11). The serum of these two groups were analyzed for malondialdehyde (MDA), glutathione S-transferase (GST), reduced glutathione (GSH), glutathione peroxidase (GPx), catalase (CAT), myeloperoxidase (MPO), nitric Oxide (NO) and superoxide dismutase (SOD) as oxidative stress biomarkers and biochemical parameters. Heifers in the group FS+ showed no significant difference in all OS parameters compared to heifers in the group FS-. The OS parameters showed almost similar values in both groups except for GST and CAT where the difference was at the limit of significance. The plasma concentration of OS biomarkers assessed in our study were not related to first service success in heifers. Further studies are needed to clarify the role of oxidative status in the reproductive performance of heifers.

A comparison of the age at first calving of contract-reared versus home-reared replacement dairy heifers

Recent rapid expansion and increased specialisation of dairy industries internationally has prompted growing interest in collaborative farming enterprises such as contract-rearing of replacement heifers. While contract-rearing provides obvious benefits to dairy farmers intending to expand their herd, it may adversely impact heifer reproductive performance as the farmer no longer manages the heifers on a day-to-day basis. Hence, the objective of this study was to determine if contract-rearing impacted heifer reproductive performance and ultimately achievement of the industry target age at first calving (AFC) of 24 months. Live weight, body condition score (BCS) and morbidity data were collected from 3908 heifers on 99 farms (54 contract-rearing dairy farms; 45 home-rearing dairy farms) on three occasions between one month of age and prior to commencement of their first breeding season; average daily gain (ADG) between farm visits was calculated. Heifer birth dates, breeds, economic breeding index (EBI), mating start dates (MSD) and calving dates were extracted from the national cattle breeding database. To assess the reproductive performance of study heifers, the outcome of interest was age at first calving (AFC). In addition to the effect of heifer rearing system, the association between pre-breeding ADG, body weight and BCS and AFC was also investigated. Descriptive and survival analysis was performed to calculate the distribution of AFC across study farms and to assess the association of rearing strategy and other variables on AFC. Results indicate that there was no difference in median AFC between home and contract-reared heifers (24.4 months). At univariate level, variables significantly associated with AFC were occurrence of pyrexia before MSD, pre-breeding ADG, body weight and BCS. However, when the frailty effect of farm was incorporated into the multivariable model, these variables were no longer significant, indicating wide variation in individual farm management practices not measured in this study. It was concluded that rearing strategy (home versus contract-rearing) did not significantly affect heifer AFC.

Effects of maternal late-gestation nutrition on dam and subsequent progeny growth and performance of beef cattle

Our objective was to evaluate the effects of forage type and supplementation level on dam and subsequent progeny growth and progeny reproductive performance in heifers. Multiparous, May-calving cows (n = 652) were managed over 6 production cycles and arranged in a 2 × 2 factorial. They were assigned to 1 of 2 forage types: subirrigated meadow (M) or upland range (R) for 116 ± 2 d, and then 1 of 2 supplementation groups: no supplement (NoSp) or 0.45 kg/d of 33% CP (DM) supplement (Sp) for 85 ± 2 d. Body weight gain was greatest for MSp cows and intermediate for MNoSp cows, followed by RSp and then RNoSp cows ( P = 0.02). Treatment-period BCS gain was increased ( P < 0.01) in Sp cows. Sex-specific differences in postnatal progeny BW through development were detected ( P ≤ 0.05). Heifer progeny increased ( P = 0.01) percent mature BW at breeding. Pregnancy rate as a primiparous cow was increased ( P = 0.02) by maternal meadow grazing. Heifer progeny’s first calf BW ( P = 0.04) and risk of dystocia was increased ( P = 0.04) by dam supplementation. These results suggest differences in maternal late-gestation diet composition due to differences in supplementation and forage specie type and growth result in altered postnatal phenotypes of both female and male progeny.

Relationship of molecular breeding value for beef tenderness with heifer traits through weaning of their first calf

Polymorphisms in μ-calpain (CAPN1) that beneficially associate with beef tenderness are reported to antagonistically associate with calving day in beef heifers and post-partum interval to estrus in beef cows. We, therefore, hypothesized that a molecular breeding value for slice shear force, calculated based on CAPN1 and calpastatin (CAST) genotypes, would demonstrate an antagonistic relationship between genomically predicted slice shear force and ordinal calving date in replacement beef heifers. A secondary objective of this study was to evaluate the association of a polymorphism in diacylglycerol O-acyltransferase (DGAT1) with reproductive traits in beef heifers. One hundred eighty-seven MARC III heifers (¼ Angus, ¼ Hereford, ¼ Red Poll, and ¼ Pinzgauer) that had been selectively bred to increase the frequency of these polymorphisms were submitted for monthly ultrasound exams beginning at 333 d of age and continuing until the start of breeding to determine pubertal status. At the last exam before breeding, all antral follicles were counted, and the length and height of each ovary was measured to determine if genomic selection for slice shear force associated with ovarian follicle number. Calving date, calf gender, and calf birth weight were recorded at parturition. Regression analysis of the molecular breeding value for slice shear force of the heifers on ordinal calving date indicated no association between genomic prediction of tenderness and calving date (P = 0.16); however, there was a tendency for age at puberty to be delayed in heifers as genetic merit for tenderness improved (P = 0.09). The results of the present study indicate that within experimental precision, selecting for tenderness using genomic predictions had minimal or no antagonistic association with reproductive performance in heifers. Further analysis of reproductive performance as cows is needed within this population but applying these genetic markers to select for tenderness in steers does not antagonize reproductive traits influencing conception or first calf birth date and birth weight in replacement beef heifers.

Impact of trace mineral source on beef replacement heifer growth, reproductive development, and biomarkers of maternal recognition of pregnancy and embryo survival.

Trace minerals are known to play important roles in early embryo development. The study objective was to determine effects of trace mineral source on heifer reproductive performance. Beef heifers (n = 129) were randomly assigned to one of two treatments. From weaning through breeding, all heifers were individually fed a basal diet supplemented with cobalt (Co), copper (Cu), manganese (Mn), and zinc (Zn) either from organic sources (COMP; Cu, Mn, and Zn amino acid complexes and Co glucoheptonate; Availa-4, Zinpro Corporation, Eden Prairie, MN) or inorganic sources (INORG; Cu, Mn, and Zn hydroxychlorides; Intellibond C, M, and Z, Micronutrients, Indianapolis, IN) and Co as CoSO4. Blood samples and a reproductive tract score (RTS) were collected to determine pubertal status. All animals were synchronized and artificially inseminated. Pregnancy status was determined by lymphocyte gene expression, circulating concentrations of pregnancy-associated glycoproteins (PAGs), and by transrectal ultrasonography after artificial insemination. Embryonic loss was defined as when a previously pregnant animal was subsequently diagnosed not pregnant. Data were analyzed using the MIXED procedure in SAS. Puberty (P = 0.44), pelvic area (P = 0.74), RTS (P = 0.49), and estrus expression (P = 0.82) were not influenced by treatment. There was no effect of treatment (P = 0.37) or treatment by time (P = 0.19) on pregnancy, but there was a tendency (P = 0.13) for decreased embryonic loss among COMP heifers (27 ± 6%) compared to INORG heifers (38 ± 6%). There was a treatment by pregnancy status by time interaction (P < 0.01) on circulating PAG concentrations with PAG concentrations tending (P = 0.08) to be greater on day 25 among heifers in the COMP treatment compared to heifers in the INORG group. In summary, source of trace mineral did not affect puberty, RTS, pelvic area, or overall pregnancy success, but feeding complexed trace minerals tended to increase circulating PAG concentrations and embryo survival.

Genotype-by-environment interaction in Holstein heifer fertility traits using single-step genomic reaction norm models

BackgroundThe effect of heat stress on livestock production is a worldwide issue. Animal performance is influenced by exposure to harsh environmental conditions potentially causing genotype-by-environment interactions (G × E), especially in highproducing animals. In this context, the main objectives of this study were to (1) detect the time periods in which heifer fertility traits are more sensitive to the exposure to high environmental temperature and/or humidity, (2) investigate G × E due to heat stress in heifer fertility traits, and, (3) identify genomic regions associated with heifer fertility and heat tolerance in Holstein cattle.ResultsPhenotypic records for three heifer fertility traits (i.e., age at first calving, interval from first to last service, and conception rate at the first service) were collected, from 2005 to 2018, for 56,998 Holstein heifers raised in 15 herds in the Beijing area (China). By integrating environmental data, including hourly air temperature and relative humidity, the critical periods in which the heifers are more sensitive to heat stress were located in more than 30 days before the first service for age at first calving and interval from first to last service, or 10 days before and less than 60 days after the first service for conception rate. Using reaction norm models, significant G × E was detected for all three traits regarding both environmental gradients, proportion of days exceeding heat threshold, and minimum temperature-humidity index. Through single-step genome-wide association studies, PLAG1, AMHR2, SP1, KRT8, KRT18, MLH1, and EOMES were suggested as candidate genes for heifer fertility. The genes HCRTR1, AGRP, PC, and GUCY1B1 are strong candidates for association with heat tolerance.ConclusionsThe critical periods in which the reproductive performance of heifers is more sensitive to heat stress are trait-dependent. Thus, detailed analysis should be conducted to determine this particular period for other fertility traits. The considerable magnitude of G × E and sire re-ranking indicates the necessity to consider G × E in dairy cattle breeding schemes. This will enable selection of more heat-tolerant animals with high reproductive efficiency under harsh climatic conditions. Lastly, the candidate genes identified to be linked with response to heat stress provide a better understanding of the underlying biological mechanisms of heat tolerance in dairy cattle.

PSIV-26 Effects of extended-release eprinomectin on heifer growth and reproductive performance while grazed on endophyte-infected tall fescue or housed in drylot

Abstract The objective was to assess the effects of an extended-release eprinomectin (LongRange) on beef heifer reproductive performance when grazed on endophyte-infected tall fescue or housed on drylot. In a split-plot design, fall-born, Angus × Simmental heifers (n = 153) were stratified by BW and divided into 6 groups. Groups were randomly assigned environmental treatments: grazed endophyte-infected tall fescue (pasture) or maintained in drylot and fed alfalfa hay. Within a group, heifers were randomly assigned to LongRange (LR) or saline (control). Heifers were dewormed with oral fenbendazole (SafeGuard) to minimize parasite load before trial initiation. On d 140 and final pregnancy check, body weight (BW) and body condition score (BCS) were collected; BW was also collected at time of artificial insemination (AI). Hair coat score (HCS), fecal egg count (FEC), packed cell volume (PCV), and respiration rates (RR) were collected on d 140. Data were analyzed using the MIXED procedure of SAS. Environment × treatment effects for BW were detected (P ≤ 0.01) at d 140 and at overall pregnancy confirmation; LR increased BW to a greater magnitude in pasture than in drylot heifers. At breeding, LR increased (P = 0.01) heifer BW compared to control. On d 140, LR increased (P = 0.01) heifer BCS compared to control. On d 140, pasture heifers tended (P = 0.08) to have greater RR than drylot heifers. Heifer AI pregnancy rates were not affected (P ≥ 0.21) by treatments. Environment × treatment effects for overall pregnancy were detected (P = 0.03); LR increased overall pregnancy rate in pasture compared to drylot heifers and LR tended to increase overall pregnancy rate compared with control in pasture heifers. In conclusion, LongRange increased BW to a greater extent in pasture than in drylot and tended to increase heifer final pregnancy rate compared to control on pasture.

404 Beef heifer development: Managing nutrition to optimize fertility

Abstract Beef cattle longevity can be tied to reproductive performance. Developing heifers that will thrive in their environment, under specific management systems, is crucial for today’s producers. Management decisions influencing heifer fertility are numerous; however, the most commonly discussed and studied revolves around nutrition. The objectives of this presentation are to review our understanding of the influence of nutrition on beef heifer fertility and identify potential mechanisms which may improve heifer fertility and beef producer profitability. Also, we will identify management decisions that may impact body weight gain or efficiency of weight gain, thus impacting fertility. Management strategies delaying heifer growth patterns pre- or post-weaning have been reported to alter heifer reproductive performance. Additionally, developing heifers on native range compared to in the dry lot or confinement settings may alter growth rates/patterns, thus affecting the heifer’s ability to become pregnant, or maintain that pregnancy. Supplementing heifers with specific nutrient profiles has also been reported to improve pregnancy rates compared with non-supplemented or control animals. Previously, it was believed heifers are born with a finite number of follicles within their ovaries, and the depletion of the ovarian reserve occurs at a constant rate. Recent research has challenged this, reporting heifers developed on a stair-step growth program had an increased number of primordial follicles compared to constant gain developed heifers. Additionally, development system (native range vs. dry lot) appears to impact ovarian function. Continued research increasing our understanding of mechanisms involved in improving heifer fertility are warranted. These efforts will aid in identifying management strategies that will optimize animal reproductive performance.

An Assessment of Secondary Clinical Disease, Milk Production and Quality, and the Impact on Reproduction in Holstein Heifers and Cows from a Single Large Commercial Herd Persistently Infected with Bovine Viral Diarrhea Virus Type 2.

The aim of this study was to evaluate secondary clinical disease, milk production efficiency and reproductive performance of heifers and cows persistently infected (PI) with bovine viral diarrhea virus type 2 (BVDV type 2). PI animals (n = 25) were identified using an antigen capture ELISA of ear notch samples. They were distributed into three age groups: ≤ 12 (n = 8), 13 to 24 (n = 6) and 25 to 34 (n = 11) months old. A control group of BVDV antigen ELISA negative female cattle that were age matched to the PI animals was utilized from the same herd. The PI group had a 1.29 higher odds ratio for diarrhea than controls (p = 0.001, IC95% = 1.032–1.623) and 1.615 greater chance of developing bovine respiratory disease (BRD) (p = 0.012, IC95% = 1.155–2.259). The age at first insemination (p = 0.012) and number of insemination attempts required to establish the first pregnancy (p = 0.016) were both higher for PI than controls. Milk production was higher for control cows than PI cows during most of the sampling periods. Somatic cell counts (SCC) were higher in PI cows than the controls at all sampling points across lactation (p ≤ 0.042). PI cattle had a higher incidence of disease, produced less milk, a higher SCC, and poorer reproductive performance than control cattle in this study.

Relationship of dairy heifer reproduction with survival to first calving, milk yield and culling risk in the first lactation.

ObjectiveThe aim of our study was to determine the associations of heifer reproductive performance with survival up to the first calving, first-lactation milk yield, and the probability of being culled within 50 days after first calving.MethodsData from 33 large Holstein-Friesian commercial dairy herds were gathered from the official milk recording database in Hungary. The data of heifers first inseminated between January 1, 2011 and December 31, 2014 were analyzed retrospectively, using Cox proportional hazards models, competing risks models, multivariate linear and logistic mixed-effects models.ResultsHeifers (n = 35,128) with younger age at conception were more likely to remain in the herd until calving, and each additional month in age at conception increased culling risk by 5.1%. Season of birth was related to first-lactation milk yield (MY1; n = 19,931), with cows born in autumn having the highest milk production (p<0.001). The highest MY1 was achieved by heifers that first calved between 22.00 and 25.99 months of age. Heifers that calved in autumn had the highest MY1, whereas calving in summer was related to the lowest milk production (p<0.001). The risk of culling within 50 days in milk in first lactation (n = 21,225) increased along with first calving age, e.g. heifers that first calved after 30 months of age were 5.52-times more likely to be culled compared to heifers that calved before 22 months of age (p<0.001). Calving difficulty was related to higher culling risk in early lactation (p<0.001). Heifers that required caesarean section were 24.01-times more likely to leave the herd within 50 days after first calving compared to heifers that needed no assistance (p<0.001).ConclusionReproductive performance of replacement heifers is closely linked to longevity and milk production in dairy herds.

383 Effect of trace mineral source on heifer reproductive performance

Abstract Trace minerals are known to play important roles in early embryo development. The study objective was to determine effects of trace mineral source on heifer reproductive performance. Over two years, beef heifers (n = 130) were randomly assigned to two pens and two treatments, within each pen, based on breed, age, and BW. From weaning through the breeding season, all heifers were individually fed a basal diet of grass hay, corn silage, and a supplement pellet (soybean hulls, dried distiller’s grains plus solubles, minerals, vitamins and monensin). Cobalt, Cu, Mn, and Zn were supplemented with either complexed sources (Availa-4) or inorganic sources (Cu, Mn, and Zn hydroxychlorides; Intellibond C, M, and Z) and Co as CoSO4. Blood samples were collected bi-weekly, and a reproductive tract score (RTS) was collected 30 d prior to breeding to determine pubertal status. All animals were synchronized and artificially inseminated (AI). Pregnancy status was determined by lymphocyte gene expression on d 17, 19, and 21; by circulating concentrations of pregnancy associated glycoproteins (PAGs) on d 22, 23, 24, 25, 26, 27, and 28; and by transrectal ultrasonography on d 30 and 60 after AI. Embryonic loss was defined as when a previously pregnant animal was subsequently diagnosed not pregnant. Data were analyzed using the MIXED procedure in SAS. Puberty (P = 0.44), pelvic area (P = 0.74), RTS (P = 0.49), and estrus expression (P = 0.82) were not influenced by treatment. There was no effect of treatment (P = 0.37) or treatment by time (P = 0.19) on pregnancy, but there was a weak tendency (P = 0.13) for decreased embryonic loss among heifers supplemented with complexed trace minerals (27±6%) compared to inorganic minerals (38±6%). In summary, source of trace mineral did not affect puberty, RTS, pelvic area, or overall pregnancy success, but feeding complexed trace minerals tended to increase embryo survival from d 17 to 60.

Early Diagnostics of Freemartinism in Polish Holstein-Friesian Female Calves.

Simple SummaryFreemartinism is the most common type of gender developmental disorder, resulting in infertility of heifers from multiple-sex twin pregnancies. The frequency of this syndrome is related to the frequency of multiple pregnancies, the number of which has significantly increased in dairy cattle populations (HF). Therefore, rapid diagnostics is necessary to enable early elimination of heifers with freemartinism from breeding. The aim of the study was to compare and identify the best method for early identification of freemartinism. The use of cytogenetic and molecular methods (PCR, short tandem repeats (STRs), real-time PCR) allowed us to conclude that molecular methods are more effective and guarantee fast and precise diagnosis. An additional advantage of molecular methods is the easy way to collect test material, which can be frozen, unlike blood samples for cytogenetic analysis, which must be fresh and delivered within 24 h to the laboratory, which generates further costs.Freemartinism in females born from heterosexual multiple pregnancies is characterized by the presence of XX/XY cell lines due to the formation of a shared blood system by anastomoses between fetal membranes of co–twins and leads to disturbed development of the reproductive system, including infertility. The aim of this study was to estimate the most precise and effective diagnostic method, especially useful for early identification of freemartinism in young female calves. The cytomolecular evaluation results of 24 Holstein-Friesian heifers from heterosexual twins was verified by molecular techniques: PCR, short tandem repeats (STRs), and relative quantitative PCR. The molecular analyses have been found to be a more efficient testing strategy, with a higher diagnostic success rate than karyotype evaluation. In 21 heifers, leucocyte chimerism determined by the 60, XX/60, XY karyotype was revealed—the proportion of the 60, XY male cell line in individual animals was in the range of 4–66%. In three cases, a normal karyotype 60, XX was identified, which indicates that anastomoses did not occur in 12.5% of studied twins and suggests that these potentially fertile heifers can be qualified for further breeding. The precise and early identification of freemartinism can be the basis for guidelines and selection recommendations concerning the reproductive performance of heifers born from heterosexual multiple pregnancies.

158 Long term impact of ergot alkaloids on fetal heifer development and subsequent growth and reproductive performance

Abstract Previous studies from our laboratory have demonstrated physiological differences in mid-gestation cows grazing either endophyte-infected (EI) or endophyte-free (EF) tall fescue. The objective of this study was to investigate the effects of in utero exposure (TRT) of either EI or EF on heifer growth, reproductive tract development and onset of puberty. Pregnant Angus and SimAngus cows were blocked by age, BW, and breed; and then randomly assigned to graze either EF (n = 27) or EI (n = 27) pastures. At parturition, heifer birthweight was recorded and placental tissues were collected to assess placental characteristics. Heifer BW, height, frame score were recorded at weaning. Assessment of puberty via measurement of BW, BCS, reproductive tract scores (RTS) and pelvic area (PA) started at 10 mo of age. Data were analyzed using a MIXED procedure of SAS and examined for effects of TRT, sire, and age. Statistical significance was determined at P &lt; 0.05 and a tendency at 0.05); however, there was a sire by treatment interaction for ADG during onset of puberty (P &lt; 0.05). While TRT did not affect PA or RTS (P &gt; 0.05) at 10 mo of age, sire significantly influenced RTS (P &lt; 0.05) thus impacting of onset of puberty. While consumption of EI fescue impacts cow performance, calf birthweight, and ratio of cotyledon to placenta weight, it has minimal effect on postnatal growth and development through 10 mo of age. Further studies are needed to determine the impact on heifer reproductive performance.

Endocrine Profile and Reproductive Performance in Heifers Induced to Lactation

Background: Low reproductive efficiency has been one of the main factors that lead to dairy herd culling in the reproductive age. In multiparous animals, such inefficiency and culling can occur because of various factors and may be associated with occasional endocrine failures. To avoid revenue losses that incur due to lack of lactation, lactation is artificially induced in the animals that are not pregnant, using a defined protocol. The aim of this study was, therefore, to evaluate and compare the reproductive performance of heifers submitted to the induction protocol with that of pregnant heifers during the transition period.Materials, Methods &amp; Results: Sixty Holstein heifers, 32 ± 0.6 months of age, were divided into two groups: Control Group (Control, n = 30) comprising pregnant heifers that were accompanied since 21 days before the expected calving date until 224 days in milk (DIM) and an Induction Group (Induction, n = 30) comprising non-pregnant heifers submitted to a lactation induction protocol, accompanied from the beginning of the protocol until 224 DIM. For evaluation of the endocrine profile (progesterone and estradiol concentrations) of these animals, blood samples were collected at two periods: the pre-lactation (weeks -3, -2 and -1) and post-lactation (weeks 1 and 4). Heifers from both groups were submitted to weekly reproductive evaluations, from the beginning of lactation until 35 DIM. Uterine examinations were performed using ultrasonography and vaginoscopy to evaluate uterine content, cervical opening, and mucosal aspect. Females in good reproductive health were subjected to a hormonal protocol for timed artificial insemination (TAI). The pregnancy rate of heifers that could reproduce (Control, n = 13, and Induction, n = 20) were evaluated and inseminated until 49 DIM. Progesterone levels were similar (P &gt; 0.05) in the two groups at both pre- and post-start of lactation. Estradiol concentrations were different (P &lt; 0.01) among groups only in the pre-lactation period. Higher levels of progesterone (P = 0.06) were observed in the induced heifers (Induction Group = 1.07 ± 0.23 ng/mL and Control Group = 0.38 ± 0.28 ng/mL). Therefore, in the fourth week, induced heifers exhibited higher luteinic activity, the progesterone concentration was above 1 ng/mL in 42% of the animals, while just 12.5% of the Control heifers had it. The overall pregnancy rate was 47.75%. The pregnancy rate recorded for induced heifers and Control heifers was 40% and 55.55%, respectively.Discussion: Progesterone and estradiol evaluations were performed in the first week after the beginning of the lactation to evaluate the metabolism and physiological concentration of the hormones used during the protocol. The measurements were again performed in the fourth week to evaluate the return to cyclicity of the heifers in both groups. The high serum concentrations of estradiol attained during the induction, in the pre-lactation period, may have possible interfered with the uterine environment and follicular population of these animals. Furthermore, it is possible that the hormonal combination used has a central effect on the synthesis and release of gonadotrophins and/or an effect on the ovarian follicular population. Based on the hormonal profile evaluated, particularly the endocrine profile, and the reproductive performance of heifers, the results suggest that the protocol for induced lactation has a positive effect on fertility.

Association between pre-breeding metabolic profiles and reproductive performance in heifers and lactating dairy cows

Lactating cows and nulliparous heifers are in distinctive and unique physiological conditions when they are approaching the planned time of breeding, at approximately 60 days in milk and 13–15 months of age, respectively. This study aimed to profile the metabolic milieu in heifers (N = 14) and lactating cows (N = 15) in the weeks leading up to planned time of breeding. All cows were followed for a period of 15 weeks, from 3 weeks pre-calving to 12 weeks post-calving, while heifers were monitored for a period of 4 weeks leading up to the tentative week of breeding (pre-breeding period). For data analysis, we further divided cows into primiparous (N = 8) and multiparous (N = 7) cows owing to the significant difference in their milk yield. Assessment of reproductive performance showed that primiparous and multiparous cows tended to have lower pregnancy rates compared to heifers (P < 0.1). Plasma concentrations of β-hydroxybutyric acid were about 2-fold higher in multiparous cows than those of heifers in the week leading up to planned time of breeding (P < 0.05). Total bile acid levels during the pre-breeding period were higher in all lactating cows compared to heifers (P < 0.05) and glucose levels were lower in lactating cows (P < 0.05). Triglyceride concentrations were lowest in multiparous cows compared to both primiparous cows and nulliparous heifers (P < 0.05). In addition, lactating cows had higher concentrations of total-cholesterol and the high-density lipoprotein and low-density lipoprotein compared to heifers (P < 0.05). Conversely, concentrations of very low-density lipoprotein were lower in multiparous cows than primiparous cows and nulliparous heifers (P < 0.05). There were no differences in plasma glutathione levels, as measured by liquid chromatography-tandem mass spectrometry, between the groups, but the ferric reducing ability of plasma was higher in lactating cows compared to heifers (P < 0.05). These data establish the differences in the profile of metabolic and oxidative markers during the period approaching planned time of breeding in lactating cows compared to nulliparous heifers. As certain metabolites in the plasma have been shown to be represented in the ovarian follicular microenvironment, the unique profiles may influence reproductive performance in dairy cattle in different physiological stages.