Effects of altering the ratio of dietary n-6 to n-3 fatty acids on spontaneous luteolysis in lactating dairy cows.

Objectives were to evaluate the effects of altering the dietary ratio of omega-6 (n-6) to omega-3 (n-3) fatty acids on the profile of fatty acids and expression of genes related to the prostaglandin biosynthesis on endometrial tissue, uterine secretion of PGF2α, and timing of spontaneous luteolysis in dairy cows. Multiparous lactating Holstein cows (n = 45) were blocked based on milk yield and, within each block, assigned randomly to 1 of 3 dietary treatments at 14 d postpartum for 90 d. Diets were supplemented with a mixture of Ca salts of fish, safflower, and palm oils to create 3 different ratios of n-6 to n-3 fatty acids, namely R4, R5, and R6, which resulted in 3.9, 4.9, and 5.9 parts of n-6 to 1 part of n-3 fatty acids, respectively. Blood was sampled every 2 h from d 16 to 23 of the estrous cycle and assayed for concentrations of progesterone and the PGF2α metabolite 13,14-dihydro-15-keto-PGF2α (PGFM). In a subsequent estrous cycle, endometrial tissue was collected for biopsy on d 8 and endometrial fatty acids profile and gene expression were quantified. The proportion of arachidonic acid of the endometrial fatty acids increased as the dietary ratio n-6 to n-3 fatty acids increased (R4 = 9.05, R5 = 11.64, and R6 = 13.41%). On the other hand, proportions of eicosapentaenoic (R4 = 2.85, R5 = 2.14, and R6 = 2.02%) and docosahexaenoic (R4 = 3.30, R5 = 1.57, and R6 = 1.08%) decreased as the ratio of n-6 to n-3 fatty acids in the diet increased. Increasing the ratio of dietary n-6 to n-3 fatty acids increased mRNA expression of estrogen receptor 1, oxytocin receptor, cyclooxygenase 2, prostaglandin E and F synthases, and steroidogenic acute regulatory protein in endometrium, but decreased expression of peroxisome proliferator-activated receptor gamma and insulin-like growth factor-1. The changes in endometrium gene expression caused by dietary treatments were associated with changes in the ratio of n-6 to n-3 fatty acids in the endometrium. As the ratio increased from R4 to R6, the number of PGFM pulses (R4 = 5.6, R5 = 4.3, and R6 = 3.8 ± 0.6 pulses; least squares means ± standard error of the means) decreased, but the amplitude of the greatest PGFM pulse increased (R4 = 226, R5 = 267, and R6 = 369 ± 38 pg/mL). Luteolysis by d 23 of the estrous cycle was observed in 79.6% of the cows (R4 = 11/14; R5 = 13/15; and R6 = 11/15) and day of spontaneous luteolysis did not differ among treatments (R4 = 20.8; R5 = 21.1; and R6 = 21.0 ± 0.4). Three pulses of PGFM was the best predictor of luteolysis in dairy cows. Collectively, supplying the same quantity of fatty acids in the diet of lactating dairy cows, but altering the ratio of n-6 to n-3 fatty acids, influenced the endometrial fatty acids profile and gene expression and altered the pattern of prostaglandin synthesis; however, the changes were not sufficient to alter the length of the estrous cycle.

Effects of oral calcium supplementation on productive and reproductive performance in Holstein cows.

The objectives of this experiment were to determine the effects of oral Ca supplementation on milk yield, body condition, pregnancy per artificial insemination (P/AI), and days to pregnancy in Holstein cows considered to be of low (LRM; no calving assistance, live singleton without retained placenta) or high (HRM; at least one of the following: dystocia, twins, stillbirth, retained placenta, or vulvo-vaginal laceration) risk of developing metritis. The hypotheses were that oral Ca supplementation during the early postpartum period would reduce the loss of body condition and improve lactation performance and reproduction. Four hundred fifty Holstein cows were blocked by parity as primiparous cows (n=174) or multiparous cows (n=276). Within parity, a cow considered at HRM was matched with a cow of LRM and the pair was randomly assigned to control (no Ca supplementation), 86g of Ca on d 0 and 1 postpartum (CaS1), or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Body condition was scored at calving and 32 d postpartum and estrous cyclicity was evaluated at 38 and 52 d postpartum. Milk yield was recorded daily. Multiparous cows were classified as above or below the mean 305-d mature equivalent milk yield based on production in the previous lactation. Reproductive performance was evaluated for the first 210 d postpartum. Body condition did not differ among treatments, and cows lost on average 0.44 units of body condition in the first month of lactation. Calcium supplementation did not affect milk yield in the first 5 mo postpartum. For multiparous cows, Ca supplementation was beneficial to milk yield in the first 30 DIM in cows of greater production potential, but detrimental to multiparous cows with below average production potential. Calcium supplementation to primiparous cows reduced P/AI at first (control=55.8, CaS1=31.5, CaS4=37.0%) and all artificial inseminations (control=48.5, CaS1=34.6, CaS4=38.5%); however, Ca supplementation to multiparous cows improved P/AI at the first (control=32.1, CaS1=38.6, CaS4=41.3%) and all artificial inseminations (control=28.1, CaS1=35.3, CaS4=40.5%). These responses in P/AI to Ca supplementation resulted in extended median days to pregnancy (control=75, CaS1=100, CaS4=94 d) and smaller proportion of pregnant cows (control=89.3, CaS1=83.9, CaS4=83.9%) in primiparous cows, but shorter days to pregnancy (control=115, CaS1=94, CaS4=94 d) and increased proportion of pregnant cows in multiparous cows (control=67.0, CaS1=77.2, CaS4=74.3%). Risk of metritis depressed most measures of reproduction evaluated in the experiment. Results indicate that responses to oral Ca supplementation are conditional on parity and production potential of cows. Oral Ca supplementation was detrimental to reproduction in primiparous cows. On the other hand, Ca supplementation benefited reproduction in multiparous cows and milk yield in the cohort of multiparous cows of greater production potential.

Effects of oral calcium supplementation on mineral and acid-base status, energy metabolites, and health of postpartum dairy cows.

Two experiments were conducted to characterize blood concentrations of minerals and acid-base status after oral dosing of Ca salts and to determine the effects of oral Ca on mineral and metabolic status and incidence diseases. The hypotheses were that administration of oral Ca as CaCl2 and CaSO4 maintains blood total Ca (tCa) concentrations ≥2.125 mM and reduces the incidence of diseases in early lactation. In experiment 1, 18 Holstein cows on the day of calving were assigned to receive a single dose of 0, 43, or 86g of Ca as an oral bolus. Blood was sampled before and after treatments to characterize acid-base status and concentrations of minerals. In experiment 2, 450 Holstein cows considered of low (LRM; normal calving) or high risk (HRM; dystocia, twins, stillbirth, retained placenta, vulvo-vaginal laceration, or a combination of these) of metritis (primiparous-LRM=84; primiparous-HRM=84; multiparous-LRM=138; multiparous-HRM=138) on the day of calving were blocked by parity and then randomly assigned to control, no Ca supplementation; 86g of Ca on d 0 and 1 postpartum (CaS1); or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Blood was sampled before and 30 min after treatment on d 0, and 30 min after treatments on d 1 to 4, and d 7 and 10 for determination of concentrations of minerals and metabolites and blood acid-base responses. Disease incidence was evaluated for the first 30 DIM. Concentrations of ionized Ca (iCa) increased for 2h in cows supplemented with 43g of Ca and fewer than 8h in cows supplemented with 86g of Ca. The changes in iCa concentrations from pretreatment to 30 min after 86g of Ca supplemented on d 0 were 0.11±0.03 mM in multiparous cows and 0.25±0.03 mM in primiparous cows. Oral Ca reduced the incidence of subclinical hypocalcemia (SCH; tCa <2.125mM) in the first 4 d in the experiment (control=69.3%; CaS1=57.5%; CaS4=34.2%). Calcium supplementation decreased the prevalence of SCH on d 0 and 1 postpartum in all cows. Stopping oral Ca in CaS1 on d 1 postpartum, however, caused a rebound in SCH on d 2 to 4 postpartum in primiparous cows. Oral Ca increased the incidence of metritis (control=22.7%; CaS1=34.8%; CaS4=32.8%), primarily because of an increase in LRM primiparous cows (control=17.9%; CaS1=35.7%; CaS4=42.9%). Oral Ca increased morbidity in primiparous cows (control=38.1%; CaS1=61.8%; CaS4=60.3%) but had no effect on multiparous cows (control=38.2%; CaS1=35.1%; CaS4=30.1%). Large doses of oral Ca as salts of chloride and sulfate in the first days postpartum should be avoided in primiparous cows and used only in cows at risk of clinical hypocalcemia.

Effects of injectable trace mineral supplementation in lactating dairy cows with elevated somatic cell counts.

Objectives of this clinical trial were to evaluate the effects of injectable trace mineral supplementation (ITMS) on somatic cell count (SCC), linear score (LS), milk yield, milk fat and protein contents, subclinical mastitis cure, and incidence of clinical mastitis in cows with elevated SCC. Holstein cows from a commercial dairy farm in New York were evaluated for subclinical mastitis, defined as SCC ≥200×10(3) cells/mL on the test day preceding enrollment. Cows with a history of treatment for clinical mastitis in the current lactation and those pregnant for more than 150d were not eligible for enrollment. Cows fitting inclusion criteria were randomly allocated to 1 of 2 treatment groups. Cows assigned to ITMS (n=306) received 1 subcutaneous injection containing zinc (300mg), manganese (50mg), selenium (25mg), and copper (75mg) at enrollment (d 0). Control cows (CTRL; n=314) received 1 subcutaneous injection of sterile saline solution. Following treatment, visual assessment of milk was performed daily, and cows with abnormal milk (i.e., presence of flakes, clots, or serous milk) were diagnosed with clinical mastitis (CM). Chronic clinical mastitis was defined as cows with 3 or more cases of CM. Milk yield, milk fat and protein contents, SCC, and LS were evaluated once monthly. Additionally, randomly selected animals were sampled to test serum concentrations of selected minerals on d0 and 30 (n=30 cows/treatment). Treatment did not affect serum concentrations of calcium, magnesium, phosphorus, potassium, copper, iron, manganese, selenium, and zinc on d30. Injectable supplementation with trace minerals did not improve overall cure of subclinical mastitis (CTRL=42.8 vs. ITMS=46.5%), although a tendency was observed in cows with 3 or more lactations (CTRL=27.1 vs. ITMS=40.0%). Supplementation did not reduce treatment incidence of CM (CTRL=48.2 vs. ITMS=41.7%); however, it tended to reduce the proportion of cows diagnosed with chronic CM (CTRL=16.9 vs. ITMS=12.0%), particularly among first-lactation cows (CTRL=18.4 vs. ITMS=7.6%). Cure of subclinical mastitis was associated with higher serum concentrations of phosphorus and selenium on d30. Supplementing trace minerals to cows with elevated SCC had no effect on milk yield, milk fat and protein contents, SCC, and LS.

Progesterone supplementation to lactating dairy cows without a corpus luteum at initiation of the Ovsynch protocol.

The objectives were to determine the effect of progesterone supplementation on fertility responses in lactating dairy cows without corpora lutea (CL) at initiation of the timed artificial insemination (AI) program. Holstein cows from 5 commercial dairy farms were subjected to the Ovsynch-56 protocol (d -10 GnRH, d -3 PGF2α, d -0.7 GnRH, d 0 AI). Ovaries were scanned by ultrasonography on d -10. Within farm, cows without CL were blocked by pen and assigned randomly to remain as nonsupplemented controls (CON; n = 652) or to receive 2 controlled internal drug-release (CIDR) inserts containing 1.38 g of progesterone each from d -10 to -3 (2CIDR; n = 642). Cows with CL were randomly selected within pen and used as positive controls as cows in diestrus at the initiation of the Ovsynch protocol (DIEST; n = 640). Signs of estrus were detected beginning on d -9 based on removal of tail chalk, and cows in estrus received AI on the same day. Blood samples from subsets of cows on d -10, -9, -7, -5, -3, and 0 (n = 109) and on d 6, 13, and 19 (n = 156) were analyzed for progesterone concentrations. Pregnancy was diagnosed on d 32 and 60 after AI. The average progesterone concentration during the timed AI program was lowest for CON, intermediate for 2CIDR, and highest for DIEST (0.92, 2.77, and 4.93 ng/mL, respectively). The proportions of cows that ovulated in response to the first GnRH (63.6, 61.1, and 47.2%, respectively) and that had a new CL on d -3 at PGF2α injection (72.4, 67.9, and 47.4%, respectively) were greater for CON and 2CIDR compared with DIEST, respectively. The diameter of the ovulatory follicle and the proportion of cows that ovulated in response to the second GnRH did not differ among treatments. A greater proportion of CON and 2CIDR cows were detected in estrus at AI compared with DIEST cows (35.8, 39.6, and 30.6%, respectively). Pregnancy per AI was less for CON compared with 2CIDR and DIEST on d 32 (31.3, 42.2, and 38.4%, respectively) and d 60 after AI (28.9, 37.2, and 33.9%, respectively), indicating that progesterone supplementation reestablished fertility in cows lacking a CL similar to that of cows in diestrus at the initiation of the timed AI program. Treatment did not affect pregnancy loss between d 32 and 60 of gestation. Pregnancy from a subset of cows with plasma progesterone concentrations indicated that a minimum concentration of 2.0 ng/mL was needed to optimize fertility. A single ultrasound examination effectively identified a low-fertility cohort of cows based on the absence of CL at the first GnRH injection of the Ovsynch protocol. Supplementation with 2 CIDR inserts increased progesterone in plasma by an additional 1.85 ng/mL compared with CON, resulting in concentrations of 2.77 ng/mL during development of the ovulatory follicle, which restored fertility in dairy cows lacking CL to a level similar to that of cows in diestrus.

Effects of altering the ratio of dietary n-6 to n-3 fatty acids on performance and inflammatory responses to a lipopolysaccharide challenge in lactating Holstein cows.

The study was designed to evaluate the effects of altering the ratio between n-6 and n-3 fatty acids (FA) in the diet and the intake of these FA by lactating dairy cows on lactation performance and inflammatory acute phase responses to a challenge with lipopolysaccharide (LPS). Multiparous Holstein cows (n=45) were blocked based on milk yield from d 6 to d 10 postpartum and, within each block, assigned randomly to 1 of 3 dietary treatments at 14d postpartum; treatments lasted for 90d. Diets were supplemented with a mixture of Ca salts of fish, safflower, and palm oils to create 3 different ratios of n-6 to n-3 FA; namely, 3.9, 4.9, or 5.9 parts of n-6 to 1 part of n-3 FA (R4, R5, and R6, respectively). During the first 5 wk of the study, blood was sampled weekly and analyzed for concentrations of metabolites and hormones. On d 75 postpartum, cows received an infusion of 10µg of LPS into one quarter of the mammary gland to evaluate inflammatory acute phase responses. Altering the ratio of dietary n-6 to n-3 FA was reflected in changes in the FA composition of plasma and milk fat. Reducing the ratio of n-6 to n-3 FA from R6 to R4 increased dry matter intake (24.7, 24.6, and 26.1±0.5kg/d for R6, R5, and R4, respectively), with concurrent increases in yields of 3.5% fat-corrected milk (43.4, 45.4, and 48.0±0.8kg/d), milk fat (1.53, 1.60, and 1.71±0.03kg/d), milk true protein (1.24, 1.28, and 1.32±0.02kg/d), and milk lactose (2.12, 2.19, and 2.29±0.04kg/d). After the LPS challenge, concentrations of IL-6 in plasma increased as the ratio of n-6 to n-3 FA increased (112.5, 353.4, and 365.1±86.6pg/mL for R4, R5, and R6, respectively). Elevations of body temperature and somatic cell count were greater for cows fed R5 compared with those fed R4 or R6 (41.3, 40.8, and 40.8±0.2°C; 4.33, 3.68, and 3.58±0.25×10(6)/mL, for R5, R4, and R6, respectively). Haptoglobin concentration was greatest at 24h after LPS challenge for cows fed R6. Phagocytosis and oxidative burst by neutrophils collected from circulation were unaffected by dietary treatment in the first 48h after intramammary LPS infusion. In conclusion, supplying the same quantity of FA in the diet of early lactation dairy cows but altering the ratio of the polyunsaturated FA of the n-6 to n-3 families influenced lactation performance and inflammatory responses to an LPS challenge.

Effect of supplementing fat to pregnant nonlactating cows on colostral fatty acid profile and passive immunity of the newborn calf.

The objectives were to evaluate the effect of supplementing saturated or unsaturated long-chain fatty acids (FA) to nulliparous and parous Holstein animals (n=78) during late gestation on FA profile of colostrum and plasma of newborn calves and on production and absorption of IgG. The saturated FA supplement (SAT) was enriched in C18:0 and the unsaturated FA supplement (ESS) was enriched in the essential FA C18:2n-6. Fatty acids were supplemented at 1.7% of dietary dry matter to low-FA diets (1.9% of dietary dry matter) during the last 8 wk of gestation. Calves were fed 4 L of colostrum within 2h of birth from their own dam or from a dam fed the same treatment. Feeding fat did not affect prepartum dry matter intake, body weight change, or gestation length. Parous but not nulliparous dams tended to give birth to heavier calves if fed fat prepartum. Parous dams were less able to synthesize essential FA derivatives, as evidenced by lower desaturase indices, compared with nulliparous dams, suggesting a greater need for essential FA supplementation. The FA profile of colostrum was modified to a greater degree by prepartum fat feeding than was that of neonatal calf plasma. The placental transfer and synthesis of elongated n-3 FA (C20:5, C22:5, and C22:6) were reduced, whereas the n-6 FA (C18:2, C18:3, and C20:3) were increased in plasma of calves born from dams fed ESS rather than SAT. Supplementing unsaturated FA prepartum resulted in elevated concentrations of trans isomers of unsaturated monoene and diene FA, as well as C18:2n-6 in colostrum. Serum concentrations of IgG tended to be increased in calves born from dams fed fat compared with those not fed fat, and prepartum feeding of SAT tended to improve circulating concentrations of IgG in newborn calves above the feeding of ESS. Apparent efficiency of absorption of IgG was improved in calves born from dams fed fat, and SAT supplementation appeared more effective than supplementation with ESS. Feeding SAT prepartum may be of greater benefit based upon greater circulating IgG concentrations of calves after colostrum feeding. Feeding moderate amounts of saturated or unsaturated long-chain FA during the last 8 wk of gestation changed the FA profile of colostrum and plasma of neonates to reflect that of the supplements.

Prevalence of periparturient diseases and effects on fertility of seasonally calving grazing dairy cows supplemented with concentrates.

The objectives were to characterize the prevalence of periparturient diseases and their effects on reproductive performance of dairy cows in seasonal grazing farms. A total of 957 multiparous cows in 2 farms (555 in farm A and 402 in farm B) were evaluated and diseases characterized. At calving, dystocia, twin birth, stillbirth, and retained fetal membranes were recorded and grouped as calving problems. On d 7±3 and 14±3 postpartum, cows were evaluated for metritis and on d 28±3 for clinical endometritis based on scoring of the vaginal discharge. From parturition to 30 d after artificial insemination (AI), prevalence of mastitis, lameness, and digestive and respiratory problems were recorded. For subclinical diseases, diagnosis was based on blood samples collected from 771 cows and analyzed for concentrations of Ca, nonesterified fatty acids (NEFA), and ß-hydroxybutyrate. Cows were considered as having elevated NEFA concentration if the concentration was ≥0.70 mM, subclinical ketosis if the ß-hydroxybutyrate concentration was ≥0.96 mM, and subclinical hypocalcemia if the Ca concentration was ≤2.14 mM. Ovaries were scanned on d 35±3 and 49±3 postpartum for determination of estrous cyclicity. All cows were enrolled in a timed AI program and inseminated on the first day of the breeding season: on average, 86 d postpartum. Overall, 37.5% (359/957) of the cows presented at least 1 clinical disease and 59.0% (455/771) had at least 1 subclinical health problem. Prevalence of individual diseases was 8.5% for calving problems, 5.3% for metritis, 15.0% for clinical endometritis, 13.4% for subclinical endometritis, 15.3% for mastitis, 2.5% for respiratory problems, 4.0% for digestive problems, 3.2% for lameness, 20.0% for elevated NEFA concentration, 35.4% for subclinical ketosis, and 43.3% for subclinical hypocalcemia. Clinical and subclinical diseases had additive negative effects on reproduction, delaying resumption of estrous cyclicity and reducing pregnancy per AI (P/AI). Occurrence of multiple diseases further reduced reproductive efficiency compared with a single disease. Individually, subclinical hypocalcemia, elevated NEFA concentration, metritis, and respiratory and digestive problems reduced estrous cyclicity by d 49 postpartum. Elevated NEFA concentration, calving problem, metritis, clinical and subclinical endometritis, and digestive problems reduced P/AI on d 65 after AI. Moreover, calving problems and clinical endometritis increased the risk of pregnancy loss between gestation d 30 and 65. Serum concentrations of Ca and NEFA were negatively correlated, and both were associated with prevalence of uterine diseases. In conclusion, periparturient diseases were highly prevalent in seasonally calving grazing dairies and affected cows had delayed resumption of estrous cyclicity, reduced P/AI, and increased risk of pregnancy loss.

Effects of feeding polyphenols from pomegranate extract on health, growth, nutrient digestion, and immunocompetence of calves.

Objectives were to determine effects of feeding pomegranate extract (POMx) rich in polyphenols on performance, health, nutrient digestion, and immunocompetence of calves in the first 70 d of age. Holstein calves (n=67), at 2+/-1 d of age (d 0=birth day) were randomly assigned to 0 (control), 5 (POMx5), or 10 g/d (POMx10) of pomegranate extract containing 16.9% gallic acid equivalent (GAE) to result in intakes of 0, 850 and 1,700 mg of GAE/d or an average of approximately 0, 15, and 30 mg of GAE/kg of body weight (BW) per day. All calves received colostrum during the first 24 h, pasteurized milk thereafter until 61 d of age, and grain was fed ad libitum for the first 70 d of age. Calves were housed in individual hutches, and grain intake, attitude and fecal scores, incidence and duration of health disorders, and treatments for health problems were evaluated daily. Body weight was measured on 2 consecutive days at 2, 30, and 70 d of age and averaged for each measurement. Concentrations of glucose and 3-hydroxybutyrate were measured in plasma. Nutrient digestion was measured using total fecal collection during a 3-d period. Neutrophil phagocytic and killing activities and antibody response to immunization with ovalbumin were measured. Peripheral blood mononuclear cells were cultured and cytokine production measured. Feeding POMx had no effect on intake or BW gain in the first 30 d of age, but after 30 d of age, both grain dry matter intake and BW gain decreased with increasing addition of POMx, which resulted in calves that were 1.8 and 4.3 kg lighter at 70 d of age for POMx5 and POMx10, respectively, compared with controls. Feeding POMx did not influence dry matter, organic matter, or starch digestibility, but it reduced crude protein and fat digestion. Plasma concentrations of glucose and 3-hydroxybutyrate were similar among treatments throughout the first 70 d of age. Measures of calf health such as fecal and attitude scores, risk of fever, and rectal temperature were not altered by treatments. Similarly, neutrophil phagocytic and killing activities did not differ among treatments. On the contrary, feeding POMx increased synthesis of interferon-gamma and interleukin-4 by peripheral blood mononuclear cells and improved total immunoglobulin G responses to ovalbumin vaccination. These results suggest that feeding POMx top-dressed onto the grain suppresses intake of grain and digestibility of fat and protein, likely because of the high tannin content. Nevertheless, polyphenols from POMx enhanced mitogen-induced cytokine production and response to vaccination, which might benefit immune competence of calves and potentially health. Additional studies are warranted to minimize the effect of POMx on intake and digestibility and to better understand the mechanisms by which polyphenols improve immune response of calves.

Applying nutrition and physiology to improve reproduction in dairy cattle.

The establishment and maintenance of pregnancy in lactating dairy cows is a complex biological event that is influenced by a multitude of factors, from the reproductive biology of the cow to managerial aspects of the dairy farm. It is often mentioned in the scientific literature that fertility in dairy cows has declined concurrent with major advances in milk production. Some of this decline is attributed to the negative genetic correlation between milk production and reproduction. In the United States, yearly production per cow has increased steadily at a rate of 1.3% in the last decade and it is likely that this trend will continue in the years to come. At this rate, the average cow in the United States will be producing over 14 tons of milk per year in 2050 and technologies will have to be developed to allow these cows to reproduce to maintain the sustainability of dairy production. Despite high production, it is not uncommon for dairy herds with rolling herd averages for milk yield above 11,000 kg to overcome the challenges of reproduction and obtain satisfactory reproductive performance. Among other things, those herds have been able to mitigate some of the mechanisms that suppress reproduction in dairy cows such as extended postpartum anovulatory period, poor estrous detection, low pregnancy per insemination and, to a lesser extent, the high pregnancy loss. The success of those farms comes from an integrated approach to fertility that includes adequate cow comfort, elaborated transition cow management and nutrition, aggressive postpartum health monitoring program with preventative and curative measures to mitigate the negative effects of diseases on reproduction, and a sound reproductive program that includes manipulation of the ovarian cycle to allow for increased insemination rate. More recently, introduction of fertility traits in selection programs have created new opportunities for improved reproduction without neglecting economically important production traits.