In this study, we tested the overall hypothesis that CC expansion and early embryo development would be improved by including follicular fluid (FF) from small or large follicles in the oocyte maturation medium. In the first experiment, FF aspirated from bovine abattoir ovaries was added to the maturation medium at 0, 25, 50, 75 or 100%. Images of individual COCs were captured at 0, 6, 12 and 19 hours (h) of the maturation period and analyzed to calculate change in the total area over time. Cumulus cell expansion was greatest in COCs matured in 75% and 50% FF, and these differences were detectable at 12 (75% FF only) and 19 h (50% and 75% FF) of maturation. The improvement in CC expansion was greatest when FF from small follicles was used. Treatments for the subsequent experiments were selected based upon the results of the first experiment. Oocyte nuclear maturation rates were observed after supplementing the maturation medium with 0 or 75% FF and maturing for 19 h. The rate of nuclear maturation as determined by the presence or absence of the first polar body was similar between control (0% FF) and treated (75% FF) groups. In the final experiment, COCs were matured in 0%, 50% or 75% FF in preparation for IVF. Duration of the maturation period (12, 19 or 22 h) and size of the follicles from which FF was collected (small or large) also varied. In general, FF supplementation at 50% did not affect the zygotes' developmental potential (neither increased nor decreased). Supplementation of maturation medium with 75% FF from small follicles consistently reduced measures of embryo development while 75% FF from large follicles yielded mixed results. It is concluded that FF supplementation improves CC expansion, but the greater CC expansion does not benefit subsequent embryo development. Notably, however, the 50% FF treatment did not reduce blastocyst rates, indicating that FF can be included in maturation media at concentrations of 50% or less with no detriment to IVF outcomes.

Although laboratory procedures for in vitro bovine embryo production have improved immensely, developmental capacity following fertilization is still limited, especially in comparison to in vivo-produced embryos. In vivo, the maturing oocyte is enclosed in the ovarian follicle and surrounded by its cumulus cells and follicular fluid. Hormones and other components of the follicular fluid change dynamically as the follicle develops and approaches ovulation. The importance of the in vivo follicular microenvironment for oocyte developmental competence has not been well defined, however. Therefore, the objective of this study was to investigate the impact of follicle size and relative estradiol and progesterone concentrations on cumulus cell expansion and early embryo development following follicular fluid exposure during maturation in vitro. All experiments and replicates contained a standard formulation control maturation medium (cOMM). Follicular fluid was collected via needle aspiration from small (2-5 mm diameter) and large (10-20 mm diameter) follicles and pooled according to size. The follicular fluid was added to a hormone-free base medium (eOMM) as follows: supplemented with 75% untreated large follicular fluid (LFF75), 75% untreated small follicular fluid (SFF75), 75% charcoal-stripped large follicular fluid (csLFF75), 75% charcoal-stripped small follicular fluid (csSFF75). Progesterone and/or estradiol were added to the charcoal-stripped follicular fluid treatments based on average concentrations found in fluid from pooled large or pooled small follicles. These six treatment media were formulated using eOMM as a base with the following designations and additions: 75% charcoal-stripped large follicular fluid + 37 ng/ml estradiol (csLFF+E2), 75% charcoal-stripped small follicular fluid + 23 ng/ml estradiol (csSFF+E2), 75% charcoal-stripped large follicular fluid + 160 ng/ml progesterone (csLFF+P4), 75% charcoal-stripped small follicular fluid + 140 ng/ml progesterone (csSFF+P4), 75% charcoal-stripped large follicular fluid + 37 ng/ml estradiol + 160 ng/ml progesterone (csLFF+E2+P4), or 75% charcoal-stripped small follicular fluid + 23 ng/ml estradiol + 140 ng/ml progesterone (csSFF+E2+P4). Cumulus expansion in the csSFF75 maturation medium was less than that of its untreated counterpart (SFF75), while cumulus cell expansion was similar for LFF75 and csLFF75. The addition of estradiol to the follicular fluid treatments was beneficial and improved cumulus cell expansion to values similar to cOMM, while progesterone alone had no effect. The greatest cumulus cell expansion was observed when both estradiol and progesterone were added to the follicular fluid treatments. Cleavage rates were generally reduced by follicular fluid treatments, with the exception being csSFF+P4 which had a cleavage rate similar to oocytes matured in cOMM. Blastocyst rates for LFF75 and csLFF75 were similar to cOMM, while SFF75 and csSFF75 reduced blastocyst rates. Interestingly, the follicular fluid treatments with added progesterone either maintained or improved blastocyst rates such that csLFF+P4 and csSFF+P4 were similar to cOMM. The same could not be said for any of the treatments containing estradiol, whether alone or in combination with progesterone. Taken together, these results suggest a dichotomous relationship between estradiol and progesterone during maturation. Estradiol supports cumulus cell expansion while progesterone concentrations during oocyte maturation are more important for subsequent embryo development.

This work explored whether supplementing recombinant human interleukin-6 (IL6), interleukin-11 (IL11), or leukemia inhibitory factor (LIF) improves IVP bovine embryo development, morphology, and cryosurvivability. Embryos were treated from day 5 to 8 post-fertilization with either the carrier only (control) or 100 ng/mL of IL6, IL11, or LIF. Blastocyst formation and stage were determined on day 7 and 8. A subset of day 8 blastocysts was processed for immunofluorescence to count trophectoderm (TE) and inner cell mass (ICM) cell numbers and another subset was slow frozen and stored in liquid nitrogen until thawing. No differences in the blastocyst rate or blastocyst stage of development were detected. Increases in ICM cell numbers were observed for IL6 and LIF but not the IL11 treatment. None of the cytokine treatments applied before freezing affected post-thaw survival, TE or ICM cell number, or cell death 24 h after thawing. In conclusion, supplementing IL6 and LIF improves ICM cell numbers in non-frozen blastocysts, but there was no evidence that any of these cytokine treatments contain cryoprotective properties in bovine embryos.

It is not yet understood why cows that exhibit estrus and ovulate are more likely to become pregnant than those that ovulate but do not exhibit estrus during a fixed-time artificial insemination (FTAI) protocol. The objective of this work was to determine whether the follicular fluid from cows that exhibit estrus contributes to the increased likelihood of pregnancy. Lactating crossbred cows were subjected to an FTAI estrous synchronization protocol. Estrous behavior was observed and recorded prior to transvaginal follicle aspiration from cows that did (estrus, n = 7) or did not exhibit estrus (non-estrus, n = 6). Follicular fluid (25%) was then added to in vitro maturation media for the maturation of oocytes (n = 1489) from slaughterhouse ovaries. Cleavage rates were not affected by the estrous status of the cows from which the follicular fluid was collected. Blastocyst rates, however, were greater following maturation in the presence of follicular fluid from estrus cows compared to non-estrus cows (p ≤ 0.01). This difference in blastocyst rates was not related to blastocyst cell numbers (inner cell mass, trophoblast, and total), as they did not differ between estrus and non-estrus animals. This study demonstrates that the follicular fluid, and thus, the follicular environment just prior to ovulation does indeed contribute to improved pregnancy rates following FTAI.

Heat-stressed lactating dairy cattle exhibit unique metabolic symptoms, many of which are undoubtedly involved in heat-induced subfertility. Because of its known systemic effects, we hypothesized that γ-aminobutyric acid (GABA) participates in the regulation of insulin and progesterone during heat stress. Multiparous lactating Holstein cows (n = 6) were studied during four experimental periods: (1) thermoneutral (TN; d 1–5), (2) TN + hyperinsulinemic–hypoglycemic clamp (d 6–10), (3) heat stress (HS; d 16–20), and (4) HS + euglycemic clamp (d 21–25). Blood samples were collected once daily via coccygeal venipuncture into heparinized evacuated tubes. Analysis of GABA concentrations from all four treatment periods yielded no differences. In direct comparison to TN concentrations, plasma GABA tended to decrease during the HS period (16.57 ± 2.64 vs. 13.87 ± 2.28 ng/mL, respectively, p = 0.06). Both milk production and plasma insulin were moderately correlated with plasma GABA (r = 0.35, p < 0.01; r = −0.32, p < 0.01). Plasma progesterone was correlated with plasma GABA concentrations during TN but not HS periods. These results are the first to indicate that peripheral GABA could be involved in the regulation of factors known to affect production and reproduction during heat stress. More research is needed to determine its precise role(s).

Heat-stressed lactating dairy cattle exhibit unique metabolic symptoms; many of which are undoubtedly involved in heat-induced subfertility. Because of its known systemic effects, we hypothesized that γ-aminobutyric acid (GABA) participates in the regulation of insulin and progesterone during heat stress. Multiparous lactating Holstein cows (n=6) were studied during four experimental periods: 1) thermoneutral (TN; d 1-5), 2) TN + hyperinsulinemic-hypoglycemic clamp (d 6-10), 3) heat stress (HS; d 16-20), and 4) HS + euglycemic clamp (d 21-25). Blood samples were collected once daily via coccygeal venipuncture into heparinized evacuated tubes. Analysis of GABA concentrations from all four treatment periods yielded no differences. In direct comparison to TN concentrations, plasma GABA tended to be decreased during HS (16.57±2.64 vs 13.87±2.28 ng/ml, respectively, P = 0.06). Both milk production and plasma insulin were moderately correlated with plasma GABA (r=0.35, P<0.01; r = -0.32, P<0.01). Plasma progesterone was correlated with plasma GABA concentrations during TN but not HS. These results are the first to indicate that peripheral GABA could be involved in regulating aspects of production and reproduction during heat stress. More research is needed to determine its precise role(s).

This work explored whether a well-characterized recombinant human interleukin-6 (hIL6) protein will influence in vitro produced (IVP) bovine embryo development and survival after cryopreservation. Cumulus oocyte complexes were collected from abattoir derived ovaries, matured for 24 h, and fertilized using pooled semen from Holstein bulls. Embryos were treated with 0, 25, 50, or 100 ng/mL hIL6 on day 5 post-fertilization. An increase in ICM cell numbers was observed in each hIL6 treatment, with the lowest hIL6 treatment having the same magnitude of response as the middle and highest hIL6 concentration. No effects on TE cell numbers were observed. The second study involved cryopreserving (via slow freezing) of hIL6-treated blastocysts, then examining post-thaw blastocyst survival by incubating for 24 h in the absence of hIL6 treatments. Blastocyst re-expansion and hatching rates were unaffected by any of the IL6 treatments, however, increases in both ICM and TE cell numbers were detected at 24 h post-thawing in blastocysts exposed to 100 ng/mL hIL6 but not lower concentrations before freezing. A reduction in the percentage of TUNEL-positive TE cells was observed after thawing in blastocysts exposed to 25, 50 and 100 ng/mL hIL6 before cryopreservation. No treatment-dependent changes in TUNEL-positive ICM cells were observed. In summary, hIL6 supplementation improves ICM cell numbers in bovine blastocysts to a degree that is commensurate with what has been observed when using bovine recombinant IL6. This positive effect of hIL6 on ICM cell numbers is maintained after freezing and thawing, and a novel improvement in post-thaw TE cell numbers occur in hIL6 treated embryos. This positive effect on TE cell numbers is attributed, at least in part, to an hIL6-dependent reduction in TE cell apoptosis.

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This work explored whether supplementing selective members of the interleukin-6 (IL6) cytokine family during in vitro bovine oocyte maturation affects maturation success, cumulus–oocyte complex (COC) gene expression, fertilization success, and embryo development potential. Human recombinant proteins for IL6, IL11, and leukemia inhibitory factor (LIF) were supplemented to COCs during the maturation period, then fertilization and embryo culture commenced without further cytokine supplementation. The first study determined that none of these cytokines influenced the rate that oocytes achieved arrest at meiosis II. The second study identified that LIF and IL11 supplementation increases AREG transcript abundance. Supplementation with IL6 supplementation did not affect AREG abundance but reduced HAS2 transcript abundance. Several other transcriptional markers of oocyte competency were not affected by any of the cytokines. The third study determined that supplementing these cytokines during maturation did not influence fertilization success, but either LIF or IL11 supplementation increased blastocyst development. No effect of IL6 supplementation on subsequent blastocyst development was detected. The fourth experiment explored whether each cytokine treatment affects the post-thaw survivability of cryopreserved IVP blastocysts. None of the cytokines supplemented during oocyte maturation produced any positive effects on post-thaw blastocyst re-expansion and hatching. In conclusion, these outcomes implicate IL11 and LIF as potentially useful supplements for improving bovine oocyte competency.

Heat stress has far-reaching ramifications for agricultural production and the severity of its impact has increased alongside the growing threats of global warming. Climate change is exacerbating the already-severe consequences of seasonal heat stress and is predicted to cause additional losses in reproductive performance, milk production and overall productivity. Estimated and predicted losses are staggering, and without advancement in production practices during heat stress, these projected losses will threaten the human food supply. This is particularly concerning as the worldwide population and, thus, demand for animal products grows. As such, there is an urgent need for the development of technologies and management strategies capable of improving animal production capacity and efficiency during periods of heat stress. Reproduction is a major component of animal productivity, and subfertility during thermal stress is ultimately the result of both reproductive and whole-body physiological responses to heat stress. Improving reproductive performance during seasonal heat stress requires a thorough understanding of its effects on the reproductive system as well as other physiological systems involved in the whole-body response to elevated ambient temperature. To that end, this review will explore the reproductive repercussions of whole-body consequences of heat stress, including elevated body temperature, altered metabolism and circulating lipopolysaccharide. A comprehensive understanding of the physiological responses to heat stress is a prerequisite for improving fertility, and thus, the overall productivity of dairy cattle experiencing heat stress.

Consumption of zearalenone (ZEN) detrimentally affects tissues and systems throughout the body, and these deleterious effects are especially pronounced in swine. The objectives of this project were to determine the effects of short-term consumption of ZEN (at concentrations that could be found on-farm) on growth, carcass weight, liver weight, and reproductive tissues of pubertal gilts, and to determine if the effects are transient or persistent. Cross-bred gilts (107.25 +/- 2.69 kg) were randomly assigned to one of three feed treatments: 1) solvent only for 21 d (CON; n = 10), 2) ZEN for 7 d followed by 14 d of solvent (ZEN-7; 6 mg/d; n = 10), and 3) ZEN for 21 d (ZEN-21; 6 mg/d; n = 10). Body weights were collected at the beginning and end of the experiment (189.1 +/- 0.8 and 211.1 +/- 0.8 d of age, respectively). Carcass weights and tissues were collected at harvest. There were no treatment-based differences in growth, carcass, liver, or reproductive tissue weights. Histological analyses revealed differences based on treatment and the interaction between treatment and luteal status. The thickness of the ampullary muscularis declined with ZEN exposure (P < 0.05), while the isthmic epithelial cell height (P < 0.01) and uterine endometrial thickness (P < 0.02) increased. Interestingly, the thickness of the isthmic muscularis, uterine myometrium, and epithelial cell height only differed in the presence of a corpus luteum. Uterine epithelial cell height in the luteal phase was lowest in ZEN-7 pigs (P < 0.01). The isthmic muscularis in the luteal phase was thinner in pigs from both ZEN treatments (P < 0.01). Conversely, the luteal-stage myometrium was thicker in pigs from both ZEN treatments (P < 0.01). The discovery of these tissue-based differences during the luteal phase is particularly concerning since this corresponds with the time when embryos would be affected by the functional competency of the oviduct and uterus. The results of this work demonstrate that short-term consumption of ZEN produces microscopic, but not macroscopic alterations in reproductive organs which are likely to have negative effects on their subsequent function and that these differences persist even after ZEN consumption ceases. Taken together, these results indicate that it is insufficient to rely solely on outwardly visible symptoms as indicators of zearalenone exposure, as detrimental effects on reproductive tissues were found in the absence of phenotypic and morphologic changes. Gilts consuming zearalenone-treated feed exhibited histological changes in their reproductive tissues, even in the absence of gross morphological differences. This observation suggests that reproductive performance is affected by zearalenone consumption at concentrations that do not elicit outwardly visible symptoms. Lay Summary The mycotoxin zearalenone is a common contaminant of livestock feed. The consumption of zearalenone is particularly problematic for pigs as they are very sensitive to its effects. This study evaluated the effects of zearalenone on growth, carcass weight, liver weight, and reproductive tissues in young female pigs. Thirty pigs were split across three treatment groups. The control group was given standard feed (no zearalenone added) for 21 d, the second group received zearalenone-treated feed for 7 d followed by 14 d of standard feed, and the third group received zearalenone-treated feed for the full 21 d. Pigs receiving the treated feed exhibited no visible symptoms associated with zearalenone consumption. There were also no treatment-related differences in growth, carcass weight, liver weight, or reproductive tract weight. Histological analyses of both the oviduct and uterus revealed changes in tissue thickness that could indicate potential impairments in reproductive organ function. Changes in tissue layer thickness were especially prominent in the luteal phase. This interaction between the treatment and the presence of a corpus luteum is noteworthy because tract function during the luteal phase is imperative for fertilization and early embryonic development.

Objective: The objective of this study was to evaluate growth and reproductive characteristics of heifers consum-ing endophyte-infected (EI) tall fescue seed in a feedlot setting with or without sodium bicarbonate supplementa-tion.Materials and Methods: A total of 48 commercial beef heifers (+/- 1.2 mo; BW = 268 +/- 24 kg) were used in an 84-d experiment. Animals were blocked by BW and as-signed to treatments. Treatments were arranged in a 2 x 2 factorial design with heifers fed either EI fescue seed with 1,320 mu g/kg total ergot alkaloid without sodium bicarbon-ate (E+B-) or with sodium bicarbonate (E+B+), or EI fescue seed with 11 mu g/kg total ergot alkaloid without sodium bicarbonate (E-B-) or with sodium bicarbonate (E-B+). Data were analyzed utilizing R statistical soft-ware (R Foundation for Statistical Computing).Results and Discussion: At d 56, there tended to be an interaction between seed type and bicarbonate supple-mentation for G:F (P = 0.084) and ADG (P = 0.071). Neither fescue seed type nor bicarbonate supplementation affected DMI at d 56 (P >= 0.739). By d 84, bicarbonate supplementation tended to decrease ADG (P = 0.087), and intake of whole seed from E+ fescue tended to de-crease DMI (P = 0.074). Prolactin concentrations tended to be lower in heifers consuming E+ when compared with heifers consuming E- on d 56 (P = 0.09). However, there was no difference in overall prolactin concentrations over the full experimental period (P > 0.05). Implications and Applications: The observations in this study failed to show any noteworthy abnormalities in growth and reproductive performance associated with feeding a whole E+ fescue seed with 1,320 mu g/kg total ergot alkaloid, and as such, there was little positive influ-ence of bicarbonate supplementation on the productive outcomes assessed. The lack of productive performance responses to endophyte-infected fescue seed or to sodium bicarbonate supplementation could be due to low power, whole-seed feeding, a corn-silage basal diet, the lack of thermal stress during the feeding period, or other experi-mental design limitations.

Ovum pickup and in vitro production (IVP) of bovine embryos are replacing traditional multiple ovulation embryo transfer (MOET) as the primary means for generating transferable embryos from genetically elite sires and dams. However, inefficiencies in the IVP process limit the opportunities to produce large numbers of transferable embryos. Also, the post-transfer competency of IVP embryos is inferior to embryos produced by artificial insemination or MOET. Numerous maternal, paternal, embryonic, and culture-related factors can have adverse effects on IVP success. This review will explore the various efforts made on describing how IVP embryo development and post-transfer competency may be improved by supplementing hormones, growth factors, cytokines, steroids and other bioactive factors found in the oviduct and uterus during early pregnancy. More than 40 of these factors, collectively termed as embryokines, are reviewed here. Several embryokines contain abilities to promote embryo development, including improving embryo survivability, improving blastomere cell numbers, and altering the distribution of blastomere cell types in blastocysts. A select few embryokines also can benefit pregnancy retention after IVP embryo transfer and improve neonatal calf health and performance, although very few embryokine-supplemented embryo transfer studies have been completed. Also, supplementing several embryokines at the same time holds promise for improving IVP embryo development and competency. However, more work is needed to explore the post-transfer consequences of adding these putative embryokines for any adverse outcomes, such as large offspring syndrome and poor postnatal health, and to specify the specific embryokine combinations that will best represent the ideal conditions found in the oviduct and uterus.

Somatic cells normally found in milk are generally either immune cells such as lymphocytes, monocytes and granulocytes, or mammary epithelial cells. The number and composition of somatic cells in milk can be influenced by a variety of factors, including infection and temperature-humidity index. The objective of this study was to determine the specific effects of heat stress on the cellular composition of the somatic cell population in milk. We used flow cytometry to ascertain the concentration and viability of mammary epithelial cells, T cells, monocyte/macrophage, and granulocytes in milk from cows maintained under heat stressed conditions compared to thermoneutral conditions. We found a significant 10% increase in the natural log concentration of epithelial cells in the milk of heat stressed cows compared to thermoneutral cows (9.3 vs. 8.4 ln(cells/mL, p = 0.02)). We also found a 12% decrease in the log concentration of live CD45+ cells (p = 0.04), and a 17% decrease in the log concentration of live CD45+ granulocytes (p = 0.04). No changes were found in CD3+CD45+ cells or CD14+CD45+ cells, however, we noted an unusual population of CD14+CD45− cells that showed significant increases of 10% (p = 0.03) and 12% (p = 0.01) in the log concentration of total and dead cells, respectively, under heat stressed conditions. These results suggest that heat stress influences the relative populations and viability of some somatic cells populations in milk. Increased losses of secretory epithelial cells into milk could have implications for milk production, and fewer viable immune cells could negatively impact the immunocompetence of dairy cows under heat stress.

The objective of this work was to evaluate the potential benefits of short-duration, high-dose chromium (Cr) supplementation in early postpartum dairy cows during the summer months. Multiparous, early-lactation cows (20.95 ± 0.21 d in milk) were assigned to 1 of 2 treatment groups: (1) control diet (Con; n = 10) or (2) control diet + Cr propionate (CrPro; 12 mg/head per day Cr; n = 12). Measurements of ovarian structures, respiration rates (RR), rectal temperatures (RT), and blood glucose concentrations were recorded every 3 d. Blood was also collected for analysis of plasma progesterone concentrations. Every 6 d, in conjunction with ultrasonography, endometrial cytology samples were collected via cytobrush from each cow to determine the incidences of subclinical endometritis, as determined by polymorphonuclear leukocyte (PMNL)%. No differences were detected in RR, RT, blood glucose, feed intake, milk yield, or change in body weight. The supplementation did, however, improve some reproductive parameters. At cytology sample 6, the PMNL% increased in Con cows, and was greater than the PMNL% in the CrPro group. Chromium consumption did not affect the number or size of most follicles, with the exception being the 6 to 9 mm category where the CrPro group had a greater average diameter and tended to have greater numbers of follicles in this category. While corpus luteum numbers and size did not differ between treatments, the ratio of progesterone to average corpus luteum volume was greater in the CrPro group compared with the Con group. The results from this study indicate that, whereas the short-term, high-dose supplementation strategy did not affect feed intake or milk yield, this Cr supplementation strategy could benefit reproductive performance during periods of stress.

In vitro production of embryos (IVP) is a valuable technology to produce embryos of high genetic value. Despite advances in IVP, the efficiency of culture systems remains low. One method to increase IVP success is the early selection of oocytes or embryos that may have greater developmental potential. Here, we investigated two methods of selection, namely BCB staining and cleavage kinetics, both individually and in conjunction, for improved developmental outcomes in vitro. We hypothesized that a synergistic use of both BCB staining and cleavage kinetics would result in identification of embryos of greater developmental potential. The selection of oocytes by BCB staining does select for those oocytes with higher developmental potential, as noted by a greater blastocyst development between BCB positive (32.6%) and BCB negative (22.0%) on day 8 post-fertilization. However, the utilization of BCB staining and cleavage kinetics in tandem resulted in a complete masking of the effect observed when using BCB alone. We obtained the highest proportion of blastocyst development per selection group using cleavage kinetics alone, in which 53.1% of embryos grouped as Fast produced a blastocyst, which was significantly different from the three other groups (Fast+, Slow, not cleaved). We observed, however, that the separation of embryos by cleavage kinetics did not predict their survival to cryopreservation. In conclusion, in standard culture systems, cleavage kinetics is an effective method for the selection of embryos with increased developmental potential to develop blastocysts, however, it may not be effective to select healthy embryos for transfer following cryopreservation.

Hyperinsulinemia concurrent with hypoglycemia is one of a myriad of physiological changes typically experienced by lactating dairy cows exposed to heat stress, the consequences of which are not yet well defined or understood. Therefore, the objective of this experiment was to separate the production-related effects of hyperinsulinemia with hypoglycemia from those of a hyperthermic environment. Multiparous lactating Holstein cows (n = 23; 58 ± 4 d in milk, 3.1 ± 0.3 lactations) were housed in temperature-controlled rooms and all were subjected to 4 experimental periods as follows: (1) thermoneutral (TN; temperature-humidity index of 65.1 ± 0.2; d 1-5), (2) TN + hyperinsulinemic-hypoglycemic clamp (HHC; insulin infused at 0.3 µg/kg of BW per h, glucose infused to maintain 90 ± 10% of baseline blood glucose for 96 h; d 6-10), (3) heat stress (HS; temperature-humidity index of 72.5 ± 0.2; d 16-20), and (4) HS + euglycemic clamp (EC; glucose infused to reach 100 ± 10% of TN baseline blood glucose for 96 h; d 21-25). Cows were fed and milked twice daily. Feed refusals were collected once daily for calculation of daily dry matter intake, and milk samples were collected at the beginning and end of each period for component analyses. Circulating insulin concentrations were measured in daily blood samples, whereas glucose concentrations were measured more frequently and variably in association with clamp procedures. Rectal temperatures and respiration rates were greater during HS than TN, as expected, and states of hyperinsulinemia and hypoglycemia were successfully induced by the HHC and high ambient temperatures (HS and EC). Feed intake differed based upon thermal environment as it was similar during TN and HHC periods, and declined for HS and EC. Milk production was not entirely reflective of feed intake as it was greatest during TN, intermediate during HHC, and lowest during HS and EC. All milk components differed with the experimental period, primarily in response to the thermal environment. Interestingly, TN baseline glucose concentrations were highly correlated with the change in glucose from TN to HS, and were related to glycemic status during HS. Furthermore, although few in number, those cows that failed to become hypoglycemic during HS tended to have a greater reduction in milk yield. The work presented here addresses a critical knowledge gap by broadening our understanding of the physiological response to heat stress and the related changes in glycemic state. This broadened understanding is fundamental for the development of novel, innovative management strategies as the dairy industry is compelled to become increasingly efficient in spite of global warming.

If validated for use in dairy cattle, interstitial continuous glucose monitors (CGMs) could be easily implemented, informative tools for research, clinical, and perhaps even on-farm applications. To evaluate their efficacy, 2 experiments were conducted, during which lactating Holstein cows were fit with indwelling jugular catheters, as well as FreeStyle Libre (FSL; Abbott) and Dexcom G6 (DexCom Inc.) CGMs secured either behind their polls, lateral to their ears, or beneath their pin bones on their upper rear legs. During the first experiment, blood (measured with a handheld glucometer) and interstitial glucose measurements were collected from 13 cows every 4 h for 96 h. In the second experiment, the same measurements were collected from 8 cows every 15 min for 6 h. At the mid-point of the sampling period (3 h), cows received a bolus dose of dextrose to facilitate comparisons across a broad range of glucose concentrations. Results from both experiments determined that functional longevity of the sensors was greatest for those sensors secured near the ear. Likewise, interstitial measurements from the ear sensors were most closely correlated with blood glucose concentrations (r = 0.82 and r = 0.71 for FSL ear and Dexcom G6 ear, respectively). Unfortunately, accuracy calculated as absolute relative error was low, at 60.7% or less. As a result of the low accuracy, even though both ear sensors detected an increase in glucose concentrations following the bolus dose, neither produced results exactly matching blood glucose measurements. The results of this work indicate that the FSL and Dexcom G6 CGMs are not currently capable of replacing blood-based glucose measurements.

The mycotoxin zearalenone (ZEN) is a common contaminant of swine feed which has been related to a wide range of reproductive anomalies in swine, such as pelvic organ prolapse, anestrous, and pseudopregnancy. New information is needed to understand how ZEN and related metabolites accumulate in swine reproductive tissues. We conducted a feeding study to track ZEN and the metabolite α-zearalenol (α-ZEL) in swine liver and reproductive tissues. Thirty pubertal gilts were randomly assigned one of three treatments, with ten pigs in each treatment group: (1) base feed with solvent for 21 days, (2) ZEN-spiked feed for seven days followed by base feed with solvent for 14 days, and (3) ZEN-spiked feed for 21 days. At the end of the trial, liver, anterior vagina, posterior vagina, cervix, uterus, ovaries, and broad ligament were collected from pigs. ZEN was found in the anterior vagina, posterior vagina, cervix, and ovaries, with significantly higher concentrations in the cervix relative to other reproductive tissues. ZEN and α-ZEL were found in liver tissue from pigs in each treatment group. Our results show that ZEN accumulates more in the cervix than other reproductive tissues. The presence of ZEN in reproductive tissues may be indicative of ZEN-related reproductive symptoms. Future work could examine how ZEN concentrations vary in reproductive tissues as a factor of the pigs age, weight, sex, or parity, to establish parameters that make pig more sensitive to ZEN.

To meet growing worldwide demands for animal products, animal production will need to increase in capacity and efficiency. Every opportunity to improve animal protein yield should be considered and explored. Developmental programming is one such opportunity that has not yet been thoroughly investigated in farm animal production. While developmental programming can be advantageous for the survival of the offspring, it is often described in conjunction with negative consequences. The known and potential causes and mechanisms are numerous, often stemming from some sort of stress experienced during the prenatal or early postnatal period. One stressor that is particularly concerning for farm animal production is heat stress. Heat stress is known to elicit adaptations associated with developmental programming in several species, but has not been investigated in dairy cattle until recently. Multiple studies have shown that heat stress experienced during the periconceptional period is generally associated with reduced milk production of resulting offspring. This could be the result of adaptations within the pre-ovulatory oocyte or early developing embryo. Interestingly, in a few select comparisons, periconceptional heat stress was associated with greater milk production. This was only observed when dairy cattle calved in the spring, and would therefore be reaching peak milk production in late spring or early summer (in heat stress). This is consistent with the match/mismatch theory associated with developmental programming, where matched prenatal/postnatal environments confer advantageous adaptations and mismatched prenatal/postnatal environments are generally detrimental to the offspring. While these studies are important additions to our growing knowledge of heat stress impacts on dairy cow production, the broader implication of developmental programming requires further investigation.