Effects of heat stress abatement on systemic and mammary inflammation in lactating dairy cows.

To examine the effects of evaporative cooling on systemic and mammary inflammation of lactating dairy cows, 30 multiparous Holstein cows (parity = 2.4, 156 d in milk) were randomly assigned to 1 of 2 treatments: cooling (CL) with fans and misters or not (NC). The experiment was divided into a 10-d baseline when all cows were cooled, followed by a 36-d environmental challenge when cooling was terminated for NC cows. The onset of environmental challenge was considered as d 1. Temperature-humidity index averaged 78.4 during the environmental challenge. Milk yield and dry matter intake (DMI) were recorded daily. Blood and milk samples were collected from a subset of cows (n = 9/treatment) on d -3, 1, 3, 7, 14, and 28 of the experiment to measure cortisol, interleukin 10 (IL10), tumor necrosis factor-α (TNF-α), haptoglobin, and lipopolysaccharide binding protein (LBP). Mammary biopsies were collected from a second subset of cows (n = 6/treatment) on d -9, 2, 10, and 36 to analyze gene expression of cytokines and haptoglobin. A subset of cows (n = 7/treatment) who were not subjected to mammary biopsy collection received a bolus of lipopolysaccharides (LPS) in the left rear quarter on d 30 of the experiment. Blood was sampled from cows and milk samples from the LPS-infused quarter were collected at -4, 0, 3, 6, 12, 24, 48, and 96 h relative to infusion, for analyses of inflammatory products. Deprivation of cooling decreased milk yield and DMI. Compared with CL cows, plasma cortisol concentration of NC cows was higher on d 1 but lower on d 28 of the experiment (cooling × time). Deprivation of cooling did not affect circulating TNF-α, IL10, haptoglobin, or LBP. Compared with CL cows, NC cows tended to have higher milk IL10 concentrations but did not show effects in TNF-α, haptoglobin, or LBP. No differences were observed in mammary tissue gene expression of TNF-α, IL10, and haptoglobin. Milk yield declined after LPS infusion but was not affected by treatment. Compared with CL cows, NC cows had greater milk somatic cell count following intramammary LPS infusion. Non-cooled cows had lower circulating TNF-α and IL10 concentrations and tended to have lower circulating haptoglobin concentrations than CL cows. Milk IL10 and TNF-⍺ concentrations were higher 3 h after LPS infusion for NC cows compared with CL cows. Additionally, NC cows tended to have higher milk haptoglobin concentration after LPS infusion than CL cows. In conclusion, deprivation of evaporative cooling had minimal effects on lactating cows' basal inflammatory status, but upregulated mammary inflammatory responses after intramammary LPS infusion.

Hormonal and immunological responses of Holstein dairy cows from late lactation to the dry period and from the dry period to early lactation.

Parturition and dry-off are challenging events for dairy cows partially due to changes in endocrine responses. The aim of this experiment was to evaluate blood concentrations of cortisol and prolactin and their effects on proliferation of peripheral blood mononuclear cells (PBMC) with or without stimulation by common immune cell mitogens (lipopolysaccharide [LPS], and concanavalin A [ConA]) of multiparous dairy cows from late lactation to the dry period and from the dry period to early lactation. Two groups of cows were enrolled: cows from late lactation to the dry period enrolled at 8 d before dry-off (LTD, n = 6, days in milk at dry-off = 332 ± 41 d) and cows from the dry period to early lactation enrolled at 7 d before expected calving date (DTL, n = 7). Blood was collected on d -8, 3, 7, and 15 relatives to dry-off for LTD cows, and on d -7, 3, 7, and 21 relatives to calving for DTL cows to analyze circulating stress hormones and to isolate PBMC. The PBMC were stimulated in vitro with prolactin (PRL), hydrocortisone (HDC), LPS, ConA, PRL + LPS, PRL + ConA, HDC+LPS, and HDC + ConA to assess proliferative responses. Plasma cortisol and PRL concentrations of LTD and DTL cows were not affected by time. Regardless of time, addition of HDC reduced PBMC proliferation stimulated by LPS, but PRL had no effect. No time effect was observed for proliferation of PBMC collected from LTD cows, but PBMC collected at 21 d after calving had higher proliferative responses to LPS and ConA than those from late dry period or early lactation. In conclusion, results from this experiment confirmed the lower PBMC proliferation during the transition period from the final week of gestation to early lactation and suggested that cows transitioning from late lactation to dry period maintained unchanged cell-mediated immune function.

Impacts of feeding a Saccharomyces cerevisiae fermentation product on productive performance, and metabolic and immunological responses during a feed-restriction challenge of mid-lactation dairy cows.

Saccharomyces cerevisiae fermentation products are commonly used in dairy cattle ration to improve production efficiency and health. However, whether these benefits will persist during feed-restriction-induced negative energy balance is unknown. The objective of this experiment was to examine the effect of a Saccharomyces cerevisiae fermentation product (NT, NutriTek, Diamond V) on performance, metabolic, inflammatory, and immunological responses to a feed-restriction challenge in mid-lactation dairy cows. Sixty Holstein cows were blocked by parity, days in milk, and milk yield and then randomly assigned to 1 of the 2 supplements: NT or placebo (CTL). The supplements were mixed in total mixed ration before feeding at a rate of 19 g/d per cow. The production phase of the experiment lasted 12 wk. Intake and milk yield were recorded daily, and milk composition was measured weekly. After the production trial, a subset of cows (NT: n = 16; CTL: n = 16) were immediately enrolled in a 5-d feed-restriction challenge with 40% ad libitum intake followed by a 5-d realimentation. Milk yield and composition were measured at each milking from d -2 to 10 relative to feed restriction. Blood samples were collected on d -2, -1, 1, 2, 3, 4, 5, 6, 8, and 10 relative to the initiation of feed restriction to measure circulating metabolites, insulin, cortisol, IL-10, tumor necrosis factor-α, lipopolysaccharide binding protein, and haptoglobin. Immune function assessments, including peripheral mononuclear cell proliferation and functional assays of circulating granulocytes, were performed on d -3 and 4 of the feed restriction. No differences were observed in dry matter intake, milk yield, or concentrations or yield of components except for fat yield. An interaction of parity and treatment was observed for milk fat yield that was lower for CTL than NT in primiparous cows, but no differences were observed among treatments in milk fat yield of multiparous cows. Feed restriction successfully induced negative energy balance and its associated metabolic changes, including reduced concentrations of plasma glucose and increased nonesterified fatty acids and ß-hydroxybutyrate. Cows fed NT had a similar decrease in milk yield but had a more pronounced reduction in plasma glucose concentration and greater ß-hydroxybutyrate concentration during feed restriction than those fed CTL. Feed restriction did not induce evidence of systemic inflammation but did reduce granulocyte functional activity. Compared with CTL, feeding NT improved the reactive oxygen species production by granulocytes after stimulation by extracellular antigens. In conclusion, feeding NT increased milk fat production of first-lactation cows but did not affect overall productive performance. However, supplementation with NT improved induced granulocyte oxidative burst. This may explain the greater glucose utilization by cows fed NT rather than CTL during feed restriction.

Effects of evaporative cooling and dietary zinc source on heat shock responses and mammary gland development in lactating dairy cows during summer.

The objective of this study was to examine the effects of evaporative cooling and dietary supplemental Zn source on heat shock responses and mammary gland development of lactating dairy cows during summer. Seventy-two multiparous lactating Holstein cows were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement. Cows were either cooled (CL) or not cooled (NC) and fed diets supplemented with 75 mg of Zn/kg of dry matter (DM) from Zn hydroxychloride (IOZ) or 35 mg of Zn/kg of DM from Zn hydroxychloride plus 40 mg of Zn/kg of DM from Zn-Met complex (ZMC). The 168-d trial included a 12-wk baseline phase when all cows were cooled and fed respective dietary treatments, and a subsequent 12-wk environmental challenge phase when NC cows were deprived of evaporative cooling. Plasma was collected from a subset of cows (n = 24) at 1, 3, 5, 12, 26, 41, 54, 68, 81 d of the environmental challenge to measure heat shock protein (HSP) 70 concentration. Mammary biopsies were collected from another subset of cows (n = 30) at enrollment (baseline samples) and at d 7 and 56 of the environmental challenge to analyze gene expression related to heat shock response, apoptosis and anti-oxidative enzymes, and to examine apoptosis and cell proliferation using immunohistochemistry. Supplemental Zn source did not affect milk yield but NC cows produced less milk than CL cows. Supplemental Zn source had no effect on mammary gene expression of HSP27, 70, and 90 or plasma concentrations of HSP70. The NC cows had greater mammary gene expression of HSP than CL cows. Circulating HSP70 of NC cows gradually increased and was higher at 81 d of environmental challenge compared with CL cows. Relative to IOZ, ZMC cows tended to have lower total mammary cell proliferation but greater mammary apoptosis. There was a tendency of greater TNFRSF1A mRNA expression for ZMC compared with IOZ cows, which may suggest upregulated extrinsic apoptosis. At d 7 of environmental challenge, NC cows had numerically higher mammary apoptosis than CL cows although not statistically significant. The NC cows tended to have greater mRNA expression of CAT and SOD3 regardless of time, and had greater mRNA expression of GPX1 at d 56 and FAS at d 7 of the environmental challenge than CL cows. Relative to CL cows, mammary cell proliferation rate was higher for NC cows at d 56 of the environmental challenge. In conclusion, dietary source of supplemental Zn has substantial effect on mammary cell turnover in lactating dairy cows, and prolonged exposure to heat stress increases mammary cell proliferation.

Effects of milk replacer feeding levels on performance and metabolism of preweaned dairy calves during summer.

The objective of this study was to evaluate the effect of milk replacer (MR) feeding programs on performance and metabolism during summer. At 3 d of age (DOA), calves were randomly assigned to 1 of 4 dietary treatments: control [CON; 0.55 kg dry matter (DM) of a 20% crude protein (CP) and 20% fat MR per day], intermediate (IL; 0.66 kg DM of a 26% CP and 17% fat MR per day), high (HL; 0.77 kg DM of a 26% CP and 17% fat MR per day), or aggressive (AL; 0.87 kg DM of a 26% CP and 17% fat MR per day). Calves were managed similarly and housed in individual polyethylene hutches using sand as a bedding material. Because 3 calves fed the AL diet developed abomasum bloating during the first 30 DOA, the AL treatment was terminated. Milk replacer (12.5% solids) was offered twice daily until 42 DOA, when MR was fed once daily to reduce its intake by 50%. Calves were weaned at 49 DOA and remained in hutches until 56 DOA. Calf starter and water were offered ad libitum. Ambient temperature and relative humidity in and outside the hutches were assessed hourly. Starter and MR intakes were recorded daily. Respiration rate and rectal temperature were determined 3 times each week. Body weight was measured at 3, 14, 28, 42, and 56 DOA. Plasma was collected at 5, 10, 14, 28, 42, 43, 45, 47, 49, 51, and 56 DOA for analysis of glucose, ß-hydroxybutyrate, triglycerides, nonesterified fatty acids, urea nitrogen, and insulin concentrations. There were no treatment effects on starter intake, rectal temperature, or respiration rate. By 7 DOA, calves fed the IL and HL diets consumed the same amount of MR and a higher amount of MR than the CON calves. At wk 2, calves from all treatments had similar MR consumption before returning to the projected intake by design at wk 4. Calves fed the IL and HL treatments had similar body weight but were heavier than those fed the CON diet at wk 6, 7, and 8. Calves fed the IL and HL diets had similar average daily gain, which was higher than that of calves fed the CON diet. There was no difference in plasma metabolites among treatments, but insulin concentration increased as milk allowance increased. In summary, feeding an intermediate level of MR during summer improved calf growth compared with the CON diet, but a higher MR allowance did not support further improvements in calf performance.

Structural and functional connectivity changes in response to short-term neurofeedback training with motor imagery.

Recent findings have been challenging current understanding of how fast the human brain change its structural and functional connections in response to training. One powerful way to deepen the inner workings of human brain plasticity is using neurofeedback (NFB) by fMRI, a technique that allows self-induced brain plasticity by means of modulating brain activity in real time. In the present randomized, double-blind and sham-controlled study, we use NFB to train healthy individuals to reinforce brain patterns related to motor execution while performing a motor imagery task, with no overt movement. After 1 h of NFB training, participants displayed increased fractional anisotropy (FA) in the sensorimotor segment of corpus callosum and increased functional connectivity of the sensorimotor resting state network. Increased functional connectivity was also observed in the default mode network. These results were not observed in the control group, which was trained with sham feedback. To our knowledge, this is the first demonstration of white matter FA changes following a very short training schedule (<1 h). Our results suggest that NFB by fMRI can be an interesting tool to explore dynamic aspects of brain plasticity and open new venues for investigating brain plasticity in healthy individuals and in neurological conditions.

Short communication: Blood mineral and gas concentrations of calves born to cows fed prepartum diets differing in dietary cation-anion difference and calcium concentration.

Eighty-two multiparous Holstein cows were fed diets differing in dietary cation-anion difference (DCAD) and Ca concentrations in a randomized block design experiment beginning 4 wk before anticipated calving to determine the effects on colostrum yield and quality and acid-base balance and mineral status of newborn calves. Treatments were arranged as a 2 × 2 factorial to provide 2 DCAD [-22 mEq/100 g of dry matter (NEG) or -3 mEq/100 g of dry matter (NEU)] and 2 supplemental Ca concentrations (1.3 or 1.8% of dry matter). After calving, cows were milked within 2 to 8 h and colostrum yield was recorded. Calves were fed 200 g of IgG of a commercial colostrum replacer within 4 h of birth. No differences were observed in birth weight or dystocia score among treatments, which averaged 42.7 kg and 1.12, respectively. Colostrum yield was not different among treatments and averaged 8.75 kg. Colostrum quality, as measured using a Brix refractometer, was not affected by DCAD but was higher for 1.3% compared with 1.8% Ca: 21.58% and 19.87%, respectively. Colostrum IgG concentrations were higher for NEG compared with NEU and for 1.3% compared with 1.8% Ca. No differences were observed in concentrations of serum IgG, Ca, P, K, Cl, anion gap, or whole-blood pH, partial pressure of O2, or SO2 of calves among treatments. Serum Mg and lactate concentrations were higher and CO2 tended to be lower for calves born to cows fed 1.3% compared with 1.8% Ca. Interactions of DCAD and Ca were observed for serum Na and Cl, which were higher for NEU-1.3% Ca and NEG-1.8% Ca compared with NEU-1.8% Ca and NEG-1.3% Ca. Whole-blood partial pressure of CO2, and HCO3 exhibited an interaction of DCAD and Ca and tended to be lower for NEU-1.3% Ca and NEG-1.8% Ca compared with NEU-1.8% Ca and NEG-1.3% Ca. Results of this trial indicate that feeding prepartum diets with 1.8% compared with 1.3% supplemental Ca reduced colostrum quality and serum concentrations of Mg and lactate in calves immediately after birth. Feeding NEG supported higher colostrum IgG concentrations. Blood mineral concentrations and blood gas balance tended to differ, but the effects were not consistent across DCAD and Ca.

Symposium review: The influences of heat stress on bovine mammary gland function.

Heat stress reduces cow milk yield and results in a significant economic loss for the dairy industry. During lactation, heat stress lowers milk production by 25 to 40% with half of the decrease in milk synthesis resulting from the reduced feed intake. In vitro studies indicate that primary bovine mammary epithelial cells display greater rates of programmed cell death when exposed to high ambient temperatures, which may lead to a decrease in the total number of mammary epithelial cells in the mammary gland, partially explaining the lower milk production of lactating cows under heat stress. The function of mammary cells is also altered by heat stress. In response to heat stress, mammary cells display higher gene expression of heat shock proteins, indicating a need for cytoprotection from protein aggregation and degradation. Further, heat stress results in increased gene expression without altering protein expression of mammary epithelial cell junction proteins, and does not substantially influence the integrity of mammary epithelium. These data suggest that the mammary gland strives to maintain cell-to-cell junction integrity by synthesizing more proteins to compensate for protein losses induced by heat stress. During the dry period, heat stress negatively affects mammary gland development by reducing mammary cell proliferation before parturition, resulting in a dramatic decrease in milk production in the subsequent lactation. In addition to mammary growth, the mammary gland of the heat-stressed dry cow has reduced protein expression of autophagic proteins in the early dry period, suggesting heat stress influences mammary involution. Emerging evidence also indicates that heifers born to cows that experience late-gestation heat stress have lower milk yield during their first lactation, implying that the maternal environment may alter mammary gland development of the offspring. It is not clear if this is due to a direct epigenetic modification of prenatal mammary gland development by maternal heat stress. More research is needed to elucidate the effect of heat stress on mammary gland development and function.

Effects of heat stress and dietary zinc source on performance and mammary epithelial integrity of lactating dairy cows.

Dietary Zn and heat stress alter gut integrity in monogastric animals. However, effects of Zn on mammary epithelial integrity in heat-stressed lactating dairy cows have not been studied. Multiparous lactating Holstein cows (n = 72) were randomly assigned to 1 of 4 treatments with a 2 × 2 factorial arrangement to study the effects of environment and Zn source on performance and mammary epithelial integrity. Treatments included 2 environments [cooled (CL) or not cooled (NC)] and 2 Zn sources [75 mg/kg of supplemental Zn as Zn hydroxychloride (IOZ) or 35 mg/kg of Zn hydroxychloride + 40 mg/kg of Zn-Met complex (ZMC)]. The experiment was divided into baseline and environmental challenge phases of 84 d each. All cows were cooled during the baseline phase (temperature-humidity index = 72.5), whereas NC cows were not cooled during environmental challenge (temperature-humidity index = 77.7). Mammary biopsies were collected on d 7 and 56 relative to the onset of environmental challenge to analyze gene expression of claudin 1, 4, and 8, zonula occludens 1, 2, and 3, occludin, and E-cadherin and protein expression of occludin and E-cadherin. Deprivation of cooling increased respiration rate (64.8 vs. 73.9 breaths/min) and vaginal temperature (39.03 vs. 39.94°C) and decreased dry matter intake (26.7 vs. 21.6 kg/d). Energy-corrected milk yield decreased for NC cows relative to CL cows (24.5 vs. 34.1 kg/d). An interaction between environment and Zn source occurred for milk fat content as CL cows fed ZMC had lower milk fat percentage than other groups. Relative to CL cows, NC cows had lower concentrations of lactose (4.69 vs. 4.56%) and solids-not-fat (8.46 vs. 8.32%) but a higher concentration of milk urea nitrogen (9.07 vs. 11.02 mg/mL). Compared with IOZ, cows fed ZMC had lower plasma lactose concentration during baseline and tended to have lower plasma lactose concentration during environmental challenge. Plasma lactose concentration tended to increase at 3, 5, and 41 d after the onset of environmental challenge in NC cows relative to CL cows. Treatment had no effect on milk BSA concentration. Cows fed ZMC tended to have higher gene expression of E-cadherin relative to IOZ. Compared with CL, NC cows had increased gene expression of occludin and E-cadherin and tended to have increased claudin 1 and zonula occludens 1 and 2 gene expression in the mammary gland. Protein expression of occludin and E-cadherin was unchanged. In conclusion, removing active cooling impairs lactation performance and affects gene expression of proteins involved in the mammary epithelial barrier, and feeding a portion of dietary zinc as ZMC improves the integrity of the mammary epithelium.