A large outbreak of the Kappa mutation of COVID-19 in Cork, Ireland, April-May 2021.

BACKGROUND: In May 2021, the B.1.617 variant of SARS-CoV-2 emerged in Ireland, and both Delta and Kappa sub-lineages were initially deemed variants of concern (VOCs) on a precautionary basis. We describe a large outbreak of SARS-CoV-2 B.1.617.1 (Kappa mutation) linked to a private gathering among third level students in Cork, Ireland. METHODS: Surveillance data were available from the Health Service Executive COVID Care Tracker. The epidemiological sequence of infection for each new case in this outbreak was tracked and whole genome sequencing was requested on all linked cases. Enhanced public health control measures were implemented by the Department of Public Health HSE-South to contain onward spread of VOCs, including retrospective contact tracing, lengthy isolation and quarantine periods for cases and close contacts. Extensive surveillance efforts were used to describe and control onward transmission. RESULTS: There were 146 confirmed SARS-CoV-2 cases linked to the outbreak. All sequenced cases (53/146; 36%) confirmed Kappa mutation. The median age was 21 years (range 17-65). The majority (88%) had symptoms of SARS-CoV-2 infection. There were 407 close contacts; the median was 3 per case (range 0-14). There were no known hospitalisations, ICU admissions or deaths. Vaccination data was unavailable, but the outbreak pre-dated routine availability of COVID-19 vaccines among younger adults in Ireland. CONCLUSION: Enhanced public health control measures for new and emerging variants of SARS-CoV-2 may be burdensome for cases and close contacts. The overall public health benefit of enhanced controls may only become apparent when evidence on disease transmissibility and severity becomes more complete.

Supplementation of urea to a basal pasture diet fed to dairy cows to model N-partitioning relationships.

The main objective of this study was to investigate whether altering dietary crude protein (CP) through the supplementation of urea to a basal pasture diet fed to dairy cows accurately modeled N-partitioning relationships. To test this, we first needed to establish safe tolerance levels for urea in this setting. Fifteen multiparous, rumen-fistulated, mid-lactation Holstein-Friesian dairy cows were offered spring pasture (~20 kg of dry matter/cow per day) and allocated to 1 of 3 urea supplementation treatments: low N [0 g/d urea; 21% total dietary CP of dry matter (DM)], medium N (350 g/d urea; 26% total dietary CP of DM), or high N (690 g/d urea; 31% total dietary CP of DM), in a completely randomized design. The amount of urea provided daily increased gradually for all cows over a 21-d period, with target urea supplementation reached by d 21. Milk yield decreased linearly at a rate of 2.35 kg/100 g of urea intake when urea supplementation exceeded 350 g/d for 4 d (~2% of DM intake). Cows from the low- and medium-N treatments subsequently entered metabolism stalls from d 25 to 31 to collect urine, feces, and milk for total N collection. Estimated urinary N output (g/d) increased linearly with N intake (g/d), and the slope of the relationship (slope = 0.86; R2 = 0.82) was consistent with international published results. Because of the consistency of our results with previously documented relationships, our findings indicate that supplementation of urea to a basal pasture diet is a suitable technique for modeling different N intakes from pasture diets to evaluate urinary N mitigation strategies. Urea supplementation, however, should not exceed ~2% of DM intake.

Comparison of respiratory virus shedding by conventional and molecular testing methods in patients with haematological malignancy.

Respiratory viruses (RV) are a leading cause of infection-related morbidity and mortality for patients undergoing treatment for cancer. This analysis compared duration of RV shedding as detected by culture and PCR among patients in a high-risk oncology setting (adult patients with haematological malignancy and/or stem cell transplant and all paediatric oncology patients) and determined risk factors for extended shedding. RV infections due to influenza virus, parainfluenza virus (PIV), human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) from two study periods-January 2009-September 2011 (culture-based testing) and September 2011-April 2013 (PCR-based testing)-were reviewed retrospectively. Data were collected from patients in whom re-testing for viral clearance was carried out within 5-30 days after the most recent test. During the study period 456 patients were diagnosed with RV infection, 265 by PCR and 191 by culture. The median range for duration of shedding (days) by culture and PCR, respectively, were as follows-influenza virus: 13 days (5-38 days) versus 14 days (5-58 days), p 0.5; RSV: 11 days (5-35 days) versus 16 days (5-50 days), p 0.001; PIV: 9 days (5-41 days) versus 17 days (5-45 days), p ≤0.0001; HMPV 10.5 days (5-29 days) versus 14 days (5-42 days), p 0.2. In multivariable analysis, age and underlying disease or transplant were not independently associated with extended shedding regardless of testing method. In high-risk oncology settings for respiratory illness due to RSV and PIV, the virus is detectable by PCR for a longer period of time than by culture and extended shedding is observed.

Technical note: Nitrogen isotopic fractionation can be used to predict nitrogen-use efficiency in dairy cows fed temperate pasture.

The objective of this study was to investigate the relationship between nitrogen isotopic fractionation (δ(15)N) and nitrogen-use efficiency (milk nitrogen/nitrogen intake; NUE) in pasture-fed dairy cows supplemented with increasing levels of urea to mimic high rumen degradable protein pastures in spring. Fifteen cows were randomly assigned to freshly cut pasture and either supplemented with 0, 250, or 336 g urea/d. Feed, milk, and plasma were analyzed for δ(15)N, milk and plasma for urea nitrogen concentration, and plasma for ammonia concentration. Treatment effects were tested using ANOVA and relationships between variables were established by linear regression. Lower dry matter intake (P = 0.002) and milk yield (P = 0.002) occurred with the highest urea supplementation (336 g urea/d) compared with the other two treatments. There was a strong linear relationship between milk δ(15)N - feed δ(15)N and NUE: [NUE (%) = 58.9 - 10.17 × milk δ(15)N - feed δ(15)N (‰) (r(2) = 0.83, P < 0.001, SE = 1.67)] and between plasma δ(15)N - feed δ(15)N and NUE: [NUE (%) = 52.4 - 8.61 × plasma δ(15)N - feed δ(15)N (‰) (r(2) = 0.85, P < 0.001, SE = 1.56)] . This study confirmed the potential use of δ(15)N to predict NUE in cows consuming different levels of rumen degradable protein.

Carbohydrate supplements and their effects on pasture dry matter intake, feeding behavior, and blood factors associated with intake regulation.

Supplementary feeds are offered to grazing dairy cows to increase dry matter (DM) and metabolizable energy (ME) intakes; however, offering feed supplements reduces pasture DM intake, a phenomenon known as substitution. The objective of the study was to investigate changes in blood factors associated with intake regulation in monogastric species in pasture-fed dairy cows supplemented with either a starch- or nonforage fiber-based concentrate. Fifteen multiparous Friesian × Jersey cross cows were assigned to 1 of 3 treatments at calving. Measurements were undertaken in wk 8 of lactation. Treatments were pasture only, pasture plus a starch-based concentrate (3.5 kg of DM/cow per day; STA), and pasture plus a nonforage fiber-based concentrate (4.4 kg of DM/cow per day). Pelleted concentrates were fed at an isoenergetic rate in 2 equal portions at a.m. and p.m. milkings. Measurements were undertaken to investigate differences in pasture DM intake, feeding behavior, and profiles of blood factors for 4h after a.m. and p.m. milkings, the periods of intensive feeding in grazing cows. Supplementing cows with STA concentrate reduced pasture DM intake to a greater extent than the fiber concentrate, although time spent eating did not differ between treatments. The blood factor response to feeding differed between the a.m. and p.m. feeding events. Blood factors associated with a preprandial or fasted state were elevated prefeeding in the a.m. and declined following feeding, whereas satiety factors increased. In comparison, the blood factor response to feeding in the p.m. differed, with responses to feeding delayed for most factors. Plasma ghrelin concentration increased during the p.m. feeding event, despite the consumption of feed and the positive energy state remaining from the previous a.m. feeding, indicating that environmental factors (e.g., sunset) supersede physiological cues in regulating feeding behavior. The greater reduction in pasture DM intake for the STA treatment in the p.m. may be related to the level of hunger or satiety before the feeding event and not solely to the consumption of supplement. Data indicate that neuroendocrine factors are, at least in part, responsible for the substitution of pasture for supplementary feeds.

The effect of starch-, fiber-, or sugar-based supplements on nitrogen utilization in grazing dairy cows.

Nitrogen utilization in grazing cows is often low due to high concentrations of rapidly soluble and degradable protein in the pasture-based diet. Broadly, opportunities to improve N utilization lie in either reducing the amount of N consumed by the animal, or incorporating more N into milk protein. The goal of this study was to compare the relative importance of dietary N intake and productive N output for improving N utilization in grazing cows fed either starch-, fiber-, or sugar-based supplements. Also, the Cornell Net Carbohydrate and Protein System (CNCPS; Cornell University, Ithaca, NY) was evaluated as a tool to assess cow performance and improve N utilization in pasture-based systems. Eighty-five cows were randomly assigned to 1 of 5 treatments at parturition (17 cows per treatment). Treatments consisted of a pasture-only control and pasture with a starch- (St and StN), fiber- (FbN), or a sugar-based supplement. The StN and FbN treatments contained additional dietary N. Diets were formulated using the CNCPS to supply similar levels of dietary metabolizable energy, but differing levels of dietary N and metabolizable protein. Nitrogen utilization ranged from 22 to 26% across the 5 groups. Cows fed the St diet had the lowest levels of milk urea N, blood urea N, and urinary N excretion and had the highest productive N output (149 g/d). Cows fed the FbN treatment had similar productive N output (137 g/d) and consumed approximately 100g/d more dietary N than the St treatment, resulting in greater urinary N excretion. Although milk protein yield was moderately greater in the St treatment, quantitatively the difference in N intake (100g/d) had the greatest effect on N utilization and suggests that controlling dietary N intake should be the first priority when attempting to improve N utilization in grazing cows. No effect was observed of supplementing pasture-fed cattle with sugar on production or N utilization under the conditions of this experiment. Predictions of metabolizable energy and protein availability for milk yield from the CNCPS were similar to actual milk yield for all treatments. Model-predicted N utilization and excretion reflected the trends observed in the measured data and suggests that the CNCPS can be a useful tool for formulating and evaluating diets to improve N utilization in pasture-based systems.

Diurnal patterns of grazing behavior and humoral factors in supplemented dairy cows.

Offering feed supplements to grazing dairy cows results in a reduction in grazing time. However, the effect differs depending on the time of day that feeds are offered. To understand the physiological basis for this, associations among circulating factors known to be associated with intake regulation in monogastric species and grazing behavior in the dairy cow were investigated. Seventeen multiparous cows at 28 ± 5 d in milk grazed together and consumed 4.4 kg of dry matter/d of a pelleted concentrate feed supplement, equally split, at the a.m. and p.m. milking. Grazing behavior was recorded over 4 consecutive days in all 17 cows. Blood was sampled from 10 of the 17 cows every 4h over a 48-h period following the grazing behavior measurements; sampling times were staggered by 2h to provide a diurnal profile of humoral factors. Grazing profiles illustrated major grazing bouts after the a.m. and p.m. milking; however, the p.m. grazing bout was characterized as the most intensive and time spent grazing was unaffected by supplementation. Associations among proportion of cows grazing and circulating hormones and metabolites differed throughout the day. During the a.m., relationships were consistent with those reported in monogastric species, with ghrelin and nonesterified fatty acids decreasing and insulin increasing with feeding. In comparison, during the major grazing bout predusk, ghrelin concentrations increased until sunset, despite the large proportion of cows grazing, before declining; this is consistent with ghrelin stimulating the predusk grazing bout. Results indicate that humoral factors known to affect hunger and satiety in monogastric animals may also have a potential role in the physiological regulation of diurnal and feeding behavior in ruminants.

Short communication: immediate and deferred milk production responses to concentrate supplements in cows grazing fresh pasture.

The objective of this study was to determine the increase in milk production from supplementation that occurred after supplementation ceased. This portion of the total response (i.e., the deferred response), although accepted, is generally not accounted for in short-term component research projects, but it is important in determining the economic impact of supplementary feeding. Fifty-nine multiparous Holstein-Friesian dairy cows were offered a generous allowance of spring pasture [>45 kg of dry matter (DM)/cow per day) and were supplemented with 0, 3, or 6 kg (DM)/d of pelleted concentrate (half of the allowance at each milking event) in a complete randomized design. Treatments were imposed for the first 12 wk of lactation. Treatments were balanced for cow age (5.4 ± 1.68 yr), calving date (July 27 ± 26.0 d), and genetic merit for milk component yield. During the period of supplementation, milk yield and the yield of milk components increased (1.19 kg of milk, 0.032 kg of fat, 0.048 kg of protein, and 0.058 kg of lactose/kg of concentrate DM consumed), but neither body condition score nor body weight was affected. After concentrate supplementation ceased and cows returned to a common diet of fresh pasture, milk and milk component yields remained greater for 3 wk in the cows previously supplemented. During this 3-wk period, cows that previously received 3 and 6 kg of concentrate DM per day produced an additional 2.3 and 4.5 kg of milk/d, 0.10 and 0.14 kg of fat/d, 0.10 and 0.14 kg of protein/d, and 0.10 and 0.19 kg of lactose/d, respectively, relative to unsupplemented cows. This is equivalent to an additional 0.19 kg of milk, 0.006 kg of fat, 0.006 kg of protein, and 0.008 kg of lactose per 1 kg of concentrate DM previously consumed, which would not be accounted for in the immediate response. As a result of this deferred response to supplements, the total milk production benefit to concentrate supplements is between 7% (lactose yield) and 32% (fat yield) greater than the marginal response measured during the component experiment. Recommendations to dairy producers based on component feeding studies must be revised to include this deferred response.

Carbapenemase-producing Enterobacteriaceae in Irish critical care units: results of a pilot prevalence survey, June 2011.

The epidemiology of carbapenemase-producing Enterobacteriaceae (CPE) in Ireland is changing, with an increase in the number of reported cases in late 2010 and early 2011. Reported cases were predominantly linked to critical care units. In June 2011, a four-week national pilot survey took place in 40 Irish critical care units (37 adult and three paediatric) to examine the prevalence of rectal carriage of CPE and inform national CPE screening guidelines. A total of 760 screening swabs were taken over the study period, and CPE were not detected in any of the participating critical care units.

Timing of supplementation alters grazing behavior and milk production response in dairy cows.

Offering feed supplements to grazing dairy cows results in substitution of pasture; however, previous data indicate that the time at which concentrate supplements are offered might affect the level of substitution. These data indicated that cows grazed more intensely presunset, regardless of the amount of supplement offered. It was, therefore, hypothesized that substitution rate would be less, and response to supplement greater if cows received their supplement at the p.m. rather than the a.m. milking. Forty-eight multiparous, nonpregnant, Holstein-Friesian cows, approximately 60 d in milk, were randomly allocated to 1 of 3 treatments in an incomplete crossover arrangement. Treatments were pasture only, pasture + 3 kg of concentrate supplement dry matter (DM) offered during the a.m. milking (AM-SUP), and pasture + 3 kg of concentrate supplement DM offered during the p.m. milking (PM-SUP). Time spent grazing and calculated pasture DM intake did not differ between the AM-SUP and PM-SUP cows. However, a tendency (0.18 kg of milk/kg of concentrate DM) was observed for an increased marginal milk response (kg of milk/kg of DM supplement) for the AM-SUP cows when compared with PM-SUP cows. Irrespective of when supplements were offered, supplementation reduced total grazing time by a similar amount, and the reduction in time spent grazing was evident throughout the day. Cows in the PM-SUP group ruminated for longer and cows in the AM-SUP group spent more time idle compared with the pasture only groups. Cows in the AM-SUP group grazed for less time during the major a.m. grazing bout following a.m. milking compared with PM-SUP cows; in comparison, the major p.m. grazing bout following p.m. milking was unaffected by supplementation. The results indicated possible improvements in marginal milk response to supplements from altering the timing of delivery.

Associations among dairy cow body condition and welfare-associated behavioral traits.

Some evidence exists that cow body condition score (BCS) is associated with risks to animal health, and that higher BCS in extensively kept animals provides a buffer against cold conditions or other adverse weather events. Not surprisingly, measures of BCS feature in dairy cattle welfare assessment protocols. However, the degree to which BCS predicts welfare state, particularly in relation to the level of "hunger" experienced, is not well researched. The aim of this study was to examine associations between naturally arising variations in BCS in dairy cattle and time spent engaged in activities used as proxy indicators of hunger. Holstein-Friesian cows (n=113) of either North American or New Zealand ancestry were allocated to 1 of 3 levels of concentrate-feed supplementation (0, 3, or 6 kg of dry matter/d) and also offered pasture in excess of requirements. Body condition score (1 to 10 scale), pasture dry matter intake (DMI), and time budgets for grazing, ruminating, standing, and lying were recorded during early, mid, and late lactation. Body condition score varied over a wide range (2.5 to 8.5) and, within genetic strain and supplementation level, was inversely associated with pasture DMI, rate of DMI, and the proportions of time spent grazing and ruminating. In comparison, variation in BCS (within genetic strain and supplementation level) was directly associated with variations in time spent lying (in late lactation). Nevertheless, pasture DMI and time spent in the key behavioral activities were all within the normal expected limits for pasture-fed dairy cows. Thus, thin cows appeared able to achieve their nutritional requirements. Furthermore, even though thinner cows traded-off a small portion of their lying time in late lactation to forage longer, they still rested for normal periods each day. Based on these results, we found no difference in the welfare status of naturally thin and fat cows when they were offered generous pasture allowances with or without concentrate supplementation. The extent to which this pertains under conditions of persistently low feed allowances that result in reductions in BCS remains to be determined.

Genetic strain and diet effects on grazing behavior, pasture intake, and milk production.

Understanding how dairy cows adjust their grazing behavior in response to feed supplements is important for the development of management strategies that optimize profit from supplementation. New Zealand Holstein-Friesian (HF) cows have been selected for milk production on a predominantly pasture-based diet; in comparison, HF cows of North American (NA) ancestry have been selected almost exclusively for milk yield and fed diets high in nonfiber carbohydrates (NFC). We hypothesized, therefore, that supplementation would have differing effects on grazing behavior, pasture dry matter intake (DMI), and milk production in these genetic strains at peak, mid, and late lactation. A study was conducted over 2 consecutive lactations, with NA and NZ cows randomly allocated at calving to 0, 3, or 6 kg of dry matter/day concentrate plus unrestricted access to pasture. Pasture DMI, milk production, and grazing behavior were recorded at peak, mid, and late lactation. Concentrates were fed in equal amounts at morning and afternoon milking. The NA cows produced more milk and milk components, and had a greater pasture DMI, despite spending less time grazing. Declines in time spent grazing and pasture DMI were associated with increasing concentrate DMI. Grazing behavior following morning supplementation was different from that recorded following afternoon supplementation. Grazing ceased following morning supplementation before rumen fill could be a limiting factor, and the length of the grazing interval was inversely proportional to the amount of concentrate offered; these results suggest that physiological rather than physical stimuli were responsible for grazing cessation. The decrease in time spent grazing with increasing concentrate DMI is consistent with changes in neuroendocrine factors secreted in response to the presence of food in the digestive tract or with circulating products of digestion. After afternoon supplementation, sunset signaled the end of grazing irrespective of stage of lactation, timing of sunset, or supplementation status, suggesting that photoperiod influenced grazing behavior. Results confirmed changes in grazing behavior, an associated reduction in pasture DMI, and an increase in milk production when cows consume increasing amounts of concentrates. However, as the effect of supplement on grazing behavior differed between morning and afternoon supplementation, further research is required to better understand the factors controlling grazing behavior, to allow improved milk production responses to supplementary feeding.

Somatotropic axis and concentrate supplementation in grazing dairy cows of genetically diverse origin.

Supplementing pasture-fed dairy cows with concentrates in early lactation was hypothesized to result in an earlier postpartum recoupling of the somatotropic axis in New Zealand (NZ)-type Holstein-Friesian dairy cows than in North American (NA)-type cows. To test this hypothesis, NA (n=30) and NZ (n=30) cows were allocated to 1 of 3 supplementation strategies (0, 3, or 6 kg of dry matter concentrate/d) for the first 12 wk of lactation in a completely randomized design and a 2×3 factorial arrangement. Production traits and characteristics of the somatotropic axis were studied at phenotypic, hormonal, and gene expression levels. Milk production and plasma metabolite concentrations were measured weekly, and liver was biopsied in wk 1, 4, 8, and 12 postcalving. North American cows produced more milk and displayed a larger degree of somatotropic axis uncoupling than did NZ cows. This was evident in strain differences in body condition score, blood growth hormone, and insulin-like growth factor-1 concentrations, and hepatic expression of growth hormone receptor-1a. No strain×diet interactions were observed for any characteristic of the somatotropic axis at either the blood metabolite or gene expression level; however, blood insulin concentrations during wk 7 to 11 postpartum increased with concentrate supplementation in NZ but not NA cows. These results demonstrate that feeding supplements does not result in an earlier recoupling of the somatotropic axis; however, the greater blood insulin concentrations with concentrate feeding in NZ cows from wk 7 may result in an earlier recoupling in this genetic strain, after the period investigated in this study. Further research is required to understand differences in insulin control between these genetic strains.

Expression analysis of key somatotropic axis and liporegulatory genes in ghrelin- and obestatin-infused dairy cows.

Ghrelin, an orexigenic hormone, is the endogenous ligand for the growth hormone secretagogue receptor (GHSR). Obestatin is produced from the same precursor peptide as ghrelin, and although obestatin was initially thought to promote actions opposite to those of ghrelin, many studies have failed to confirm this hypothesis. In the current study, multiparous cows were continuously infused with ghrelin (n = 10) or obestatin (n = 10) for 8 wk and compared to an untreated group (n = 10) to examine the effects of these hormones on somatotropic and liporegulatory gene expression. The expression of key genes was measured by quantitative real-time polymerase chain reaction. Growth hormone secretagogue receptor mRNA expression was altered in ghrelin- and obestatin-infused cows in a similar manner, as expression was increased at 4 wk, however it had decreased by 8 wk. Obestatin-infused cows presented with a significant decrease in the expression of ATP-binding cassette A1 (ABCA1) in adipose tissue, suggesting changes in cholesterol transport. Liver insulin-like growth factor (IGF) binding protein-3 mRNA displayed a week-by-treatment interaction, as expression was increased in control and obestatin-infused cows; however, expression decreased in ghrelin-infused cows. Adipose expression of hormone sensitive lipase (LIPE) mRNA was not altered by treatment or time, suggesting hormone infusion is not initiating lipolysis. The expression of lipogenic genes in adipose tissue increased with time in all groups, consistent with the general lactational profile of lipogenesis in dairy cows. These data indicate that continuous infusion of ghrelin or obestatin does not alter the expression of key somatotropic or liporegulatory genes in the lactating dairy cow, although obestatin infusion may alter cholesterol transport.

Insulin resistance in divergent strains of Holstein-Friesian dairy cows offered fresh pasture and increasing amounts of concentrate in early lactation.

The objective of this study was to determine whether the physiological response to an intravenous glucose challenge would be affected by genetic strain or concentrate supplementation in grazing Holstein-Friesian cows in early lactation. North American (NA; n = 30) or New Zealand (NZ; n = 30) cows were randomly allocated to 1 of 3 feeding treatments. All cows were offered a generous pasture allowance, and 4 of the 6 groups received either 3 or 6 kg of dry matter (DM)/cow per day of concentrates. During wk 5 of lactation, all cows underwent an intravenous glucose challenge. Cows of NA origin produced more milk than NZ cows, but there was no significant strain effect on milk fat or protein yield. Milk yield and the yield of individual components increased with increasing level of concentrate eaten, but there were no significant strain x diet interactions. During wk 1 to 6, mean body weight and body condition score decreased in all treatments. Average body weight was greater in NA cows, but body condition score was greater for NZ cows. There was no strain or diet effect on the length of the postpartum anovulatory interval, with cows ovulating before 40 d postpartum on average. Glucose fractional turnover rate was greater in NZ cows compared with those of NA origin and in all cows receiving 6 kg of DM concentrates, indicating a less severe insulin resistance in those treatments. Consistent with this, the time taken to dispose of half the peak glucose concentration was less when 6 kg of DM concentrate was fed, and tended to be less in NZ than in NA cows. There was no effect of genetic strain on glucose area under the curve (AUC) at 60 or 120 min, but AUC at both time points was less in cows receiving 6 kg of DM concentrates per day. Neither genetic strain nor nutrition affected basal or peak insulin concentrations, insulin increment, or insulin AUC, and there were no strain x diet interactions for any of the glucose challenge response variables measured. In conclusion, differences in milk production between NA and NZ cows in early lactation can, at least in part, be explained by the greater degree of insulin resistance in the NA cows, and this insulin resistance can be overcome by supplementing grazing cows with 6 kg of DM concentrates.

Long-term infusions of ghrelin and obestatin in early lactation dairy cows.

Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor and a potential orexigenic agent in monogastrics and ruminants. Obestatin has been reported to have the opposite (anorexigenic) effect. Fifty one multiparous cows were randomly allocated to 1 of 3 groups (n = 17): a control group and 2 groups with cows continuously infused with 0.74 mumol/d of ghrelin (GHR group) or obestatin (OBE group) subcutaneously. Infusions began 21 d in milk, and treatments continued for 8 wk. Generalized linear models were used to determine the treatment effect on average daily and cumulative milk production and composition, and plasma ghrelin, growth hormone, insulin-like growth factor (IGF)-1, leptin, nonesterified fatty acids, and glucose. Mixed models, with cow included as a repeated effect, were used to determine if treatment effects differed by week postcalving for milk production, body weight, and body condition score (BCS; scale 1 to 10). Parity, breed, week of the year at calving, treatment, week postcalving, and the 2 wk preexperimental average of each measure (covariate) were included as fixed effects. Treatment did not affect dry matter intake. Cows infused with GHR lost more BCS (-0.71 units) over the 8-wk study period than the control (-0.23 BCS units) cows, and on average were thinner than cows in either of the other 2 treatments (0.2 BCS units). Consistent with the extra BCS loss in GHR cows, plasma IGF-1, glucose, and leptin concentrations were reduced and plasma nonesterified fatty acid concentrations were greater in GHR cows. Despite a numerical tendency for GHR cows to produce more milk (1,779 kg) than control (1,681 kg) or OBE (1,714 kg) cows during the 8-wk period, milk production differences were not statistically different. However, the timing of the numerical separation of the lactation curves coincided with the significant changes in BCS, IGF-1, and leptin. Results indicate a positive effect of ghrelin infusion on lipolysis. Further research is required to determine if the numerical increase in milk production, which coincides with the increased negative energy balance, is real.

Short communication: change in plasma ghrelin in dairy cows following an intravenous glucose challenge.

Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor and a potent orexigenic (appetite-stimulating) agent in humans and rodents, but little is known about its effect in dairy cows. Ten multiparous dairy cows 35 d in milk were subjected to an i.v. glucose challenge (300 mg of D-glucose/kg of body weight). Before infusion and at regular intervals after infusion, plasma glucose, insulin, nonesterified fatty acids (NEFA), growth hormone, epinephrine, and ghrelin concentrations were monitored. Plasma insulin rose (27.2 mU/L at 10 min) and NEFA, epinephrine, and ghrelin declined (nadir = 0.22 mmol/L, 22.2 microg/L, and 272 microg/L at 31, 13, and 22 min, respectively) after the glucose infusion. Ghrelin declined for 22 min before returning to suprabasal levels at approximately 75 min postinfusion. Sequential changes of the hormones and metabolites suggested a glucose transporter, type 2- and glucose transporter, type 4-mediated disposal of glucose, and an insulin-mediated reduction in NEFA. Ghrelin and epinephrine declined after glucose infusion and before the insulin peak, but the effect of insulin as a controlling factor in the hyperglycemic reduction in these hormones cannot be discounted. The post-nadir surge in ghrelin may be regulated by the decline in circulating concentrations of glucose and NEFA (an energy-deficit signal). The profile of change in plasma ghrelin in lactating dairy cows after a glucose challenge was similar to that in monogastric animals.

Concentrate supplementation reduces postprandial plasma ghrelin in grazing dairy cows: a possible neuroendocrine basis for reduced pasture intake in supplemented cows.

Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor, and a potent orexigenic agent in human and rodent studies. We hypothesized that ghrelin may play a role in the reduced grazing time in dairy cows receiving supplementary feeds. Fifty-eight Holstein-Friesian (HF) dairy cows of New Zealand (NZ; n = 28) and North American (NA; n = 30) ancestry were provided with unrestricted access to pasture and randomly allocated at calving to either 0, 3, or 6 kg of dry matter concentrates in a 2 x 3 factorial arrangement. Concentrates were offered in equal amounts at each milking. In peak lactation (75 and 79 +/- 19.7 d in milk), blood was sampled from all cows prior to the a.m. milking (i.e., baseline) and following 2 h of unrestricted access to fresh pasture after the a.m. milking on 2 consecutive weeks. Daily milk yield and fat, protein, and lactose concentrations were measured on the day of blood sampling. North American cows produced more milk and consumed numerically more pasture than did NZ cows, and NA cows had elevated plasma ghrelin concentrations pre- and postfeeding. A negative association between dry matter intake and postprandial ghrelin concentrations indicated that other controlling factors may be involved. Circulating ghrelin concentrations before feeding were not affected by concentrate supplementation, but increasing supplementation was associated with a linear decline in pasture intake and postprandial ghrelin concentrations. This negative association between concentrate supplementation and plasma ghrelin concentrations offers a potential neuroendocrine basis for the reduced pasture intake when supplements are offered to cows in grazing systems.

Short communication: genetic selection for milk production increases plasma ghrelin in dairy cows.

Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor and a potent orexigenic agent in human and rodent studies, but there is limited information about its effect in dairy cows. Twelve low genetic merit and 9 high genetic merit Holstein-Friesian dairy cows in peak lactation that were offered unrestricted access to fresh pasture were used to determine whether genetic selection for milk production resulted in an associated increase in plasma ghrelin concentration in grazing dairy cows. Blood samples were taken prior to the a.m. milking (i.e., baseline) and following 2 h of grazing after the a.m. milking on 2 consecutive wk during peak lactation. Milk production and dry matter intake were greater in high genetic merit cows compared with low genetic merit cows. Plasma ghrelin and growth hormone concentrations were elevated in high genetic merit cows pre- and postgrazing, and there was no significant interaction between genetic merit and time of sampling. Genetic merit did not affect the plasma nonesterified fatty acid or glucose concentration, but the plasma concentrations of metabolites and hormones measured were diminished 2 h after feeding. Data indicate an increase in plasma ghrelin associated with genetic selection for milk production, and an associated increase in dry matter intake.