Effects of a four-day hyperinsulinemic-euglycemic clamp in early and mid-lactation dairy cows on plasma concentrations of metabolites, hormones, and binding proteins

[The lipidosis of the liver of dairy cows: Part 1 - Role of insulin and the Growth Hormone-IGF-1 axis]

Lipidosis of the liver of dairy cows is a metabolic disease known since many years and is caused by an uptake of nonesterified fatty acids (NEFA) into the liver cells, limited metabolism of NEFA (oxidation and production of β-hydroxybutyrate), and resynthesis in relation to a low efflux as triglyceride (TG). The pathogenesis of lipidosis includes a) an augmented release of NEFA by mobilisation of adipose tissue, b) uptake of NEFA into the liver cells, c) metabolism of NEFA and d) re-synthesis of triglyceride and e) an efflux of TG as very low density lipoprotein (VLDL). The steps a-e are postpartum modified by hormones as an increase of growth hormone, a pronounced insulin resistance in combination with a decreased insulin and of IGF-1 concentrations. These hormonal changes are related to an uncoupling of the growth hormone-IGF-1-axis with enhanced lipolysis and consequences mentioned above. These alterations are associated with inflammation, oxidative and endoplasmatic stress. The metabolic and hormonal alterations are the result of the selection of dairy cows primarily for milk production without adequate food intake with the consequence of lipidosis, ketosis and further health risks (production diseases).

Effects of methionine, leucine, and insulin on circulating concentrations and mammary extraction of energy substrates and amino acids in lactating dairy cows

The aim of this experiment was to test whether insulin potentiates the effects of two abomasally infused amino acids (AA), leucine and methionine (LM), on mammary extraction efficiency of energetic and nitrogenous nutrients. Six lactating Holstein cows (155 ± 9 DIM) were ruminally-cannulated and had the right carotid artery subcutaneously transposed. Cows were fed a 20% metabolizable protein-restricted diet and abomasally infused with water (8 L/d) or AA (Met 26 g/d, Leu 70 g/d) for 8 h/d, for 7 days. On the last day of each period, cows were intravenously infused with saline (0.9% NaCl, 110 mL/h) or subjected to 8 h hyperinsulinemic clamp (IC) alongside abomasal infusions. For IC, insulin was infused at 1 µg/kg/h. Normoglycemia was maintained by varying glucose (50% w/v in water) infusion rate based on coccygeal vein glucose concentration. Carotid arterial and subcutaneous abdominal (mammary) vein blood samples were collected at 0, 1, 2, 4, and 6 h from the start of infusions. Milk weights and samples for baseline measurements of production were taken on day 5 PM, day 6 AM and PM, and day 7 AM of the experimental period. A final milk weight and sample was taken immediately after abomasal and intravenous infusions on day 7 PM for assessing the interaction between insulin and the infused AA. The experiment had an incompletely replicated Latin square design with a 2 × 2 factorial arrangement of treatments (abomasal and intravenous infusion). Baseline milk production when cows were only receiving abomasal infusions was largely unaffected by LM, but milk protein yield tended to be decreased. On day 7, LM tended to positively increase milk fat and de novo fatty acid content, and IC tended to decrease milk protein content. Both milk urea nitrogen and plasma urea nitrogen were decreased by IC. Circulating AA concentrations in plasma were decreased by both LM and IC, but mammary extraction efficiency was affected by neither. Infusion of LM had no effect on any energy metabolite analyzed. Circulating non-esterified fatty acid concentration was decreased by IC, with no effect on mammary extraction efficiency. Mammary extraction efficiency of both acetate and β-hydroxybutyrate were decreased by IC. Overall, while both circulating concentrations of energy metabolites and amino acids were decreased in response to treatments, this was not due to improved mammary extraction efficiency.

Effect of hyperketonemia on the diurnal patterns of energy-related blood metabolites in early-lactation dairy cows

Most dairy cows experience a period of energy deficit in early lactation, resulting in increased plasma concentrations of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). Our objectives were to determine (1) the diurnal variation in plasma BHB and NEFA, (2) the correlation between plasma NEFA and BHB when accounting for diurnal changes, and (3) the effect of hyperketonemia (HYK) on the diurnal pattern of blood metabolites. Jugular catheters were placed in 28 multiparous Holstein cows between 3 and 9 days in milk, and blood samples were collected every 2 h for 96 h. Cows were retrospectively classified as HYK positive (HYK; n = 13) if they had plasma BHB concentrations ≥1.2 mmol/L for ≥3 study days, or HYK negative (non-HYK; n = 15) if they had plasma BHB concentrations ≥1.2 mmol/L for ≤2 study days. Generalized linear mixed models were used to analyze concentrations of analytes over time and differences in metabolites between HYK groups. The correlation between total plasma NEFA and BHB was analyzed by calculating the area under the curve for plasma NEFA and BHB for all cows. Plasma NEFA reached a peak approximately 2 h before morning feed delivery, falling to a nadir in the late evening. Plasma BHB was at a nadir at the time of morning feed delivery, peaking 4 h later. We observed a strong positive correlation between daily plasma NEFA and BHB. Additionally, HYK cows had greater concentrations of plasma NEFA and BHB than non-HYK cows. The HYK cows also experienced a greater magnitude of change in BHB throughout the day than the non-HYK cows. Our results suggest that the time relative to feeding should be considered when analyzing plasma metabolites, as classification of energy status may change throughout a day.

Dietary restriction in sheep: Uterine functionality in ewes with different body reserves during early gestation

The aim of this study was to characterize insulin, leptin and IGF-1 profiles after undernutrition in pregnant ewes with different initial body condition (iBCS) and to investigate embryo quality, uterine gene expression and presence and location of proteins during early gestation (day 5). Thirty-six Rasa Aragonesa ewes were divided into 2 groups with different BCS: BCS> 2.75 (high, H, n = 19) and BCS <2.25 (low, L, n = 17) and they were randomly assigned to two nutritional treatments: 1.5 maintenance (M) (control, C) or 0.5 (M) (undernourishment, U) times the daily maintenance requirements establishing four groups: high-iBCS control (HC, n = 9), high-iBCS undernourished (HU, n = 10), low-iBCS control (LC, n = 9) and low-iBCS undernourished (LU, n = 8). High-iBCS ewes presented higher concentration of IGF-1, reflecting a better metabolic status in these animals. There was a greater proportion of high-iBCS ewes presenting more than one CL (P < 0.05), and associated greater P4 plasma concentration, number of recovered embryo and a tendency for higher embryo viability rate (P = 0.13). In uterus, undernourished ewes tended to present lower P4 (P = 0.09) and higher E2 concentration (P = 0.10). Inmunostaining of uterine progesterone and estrogen receptors (PR and ERα) was not affected by iBCS and nutritional treatment. Ewes with low-iBCS tended to have more INSR mRNA, and undernourished ewes tended to have more IGFBP2 mRNA expression (P < 0.08). An interesting finding was that the uterine response to undernutrition was dependent on iBCS: a higher expression of GHR (P < 0.05) and a tendency in IGFBP5 (P = 0.09) mRNA was found in undernourished than control ewes but only in the high-iBCS group. In summary, the present study demonstrates that the endocrine response and the uterine gene expression to undernutrition depend on the initial body energy reserves (iBCS) and appears to be associated with a differential embryo quality.

Oxyntomodulin analog and exendin-4 derivative lower plasma glucose in cattle

The present study was undertaken with the aim of examining whether and how exendin-4 (1-3) fragment, ie, Ex-4 (1-3) fragment, contributes to the regulation of glucose. An analog of oxyntomodulin (OXM) ([Gly², Glu³]-OXM), a glucagon analog ([Gly², Glu³]-glucagon), and two derivatives of Ex-4 (glucandin and [Gly², Glu³]-glucandin) were synthesized by substituting with Gly², Glu³ at the N-terminuses of OXM and glucagon and/or by attaching Ex-4 (30-39) amide at the C-terminus of glucagon. Effects of these peptides on plasma insulin and glucose concentrations were investigated in cattle by conducting 3 in vivo experiments. In all 3 experiments, 0.1% BSA saline was injected as a control. In experiment 1, glucandin (amino acid sequence was glucagon [1-29]-Ex-4 [30-39] amide) and [Gly², Glu³]-glucandin were injected at the dose rates of 5 μg/kg BW in 4-mo-old Holstein steers. Results showed that glucoregulatory effects of glucandin were similar to those of glucagon. [Gly², Glu³]-glucandin stimulated insulin secretion at 2 to 10 min and lowered glucose concentrations at 15 to 75 min. Experiment 2 was carried out to better understand the glucose-lowering potency of [Gly², Glu³]-glucandin, in comparison with Ex-4 and glucagon-like peptide-1 (GLP-1), using 4.5-mo-old Holstein steers. [Gly², Glu³]-glucandin was injected at dose rates of 0.3 μg/kg BW, 1.0 μg/kg BW, 3.2 μg/kg BW, and 6.4 μg/kg BW. Ex-4 and GLP-1 were injected at dose rates of 0.3 μg/kg BW. Results showed that the insulinotropic and glucose-lowering effects of [Gly², Glu³]-glucandin were not as potent as for Ex-4 and GLP-1, and the minimum effective dose of [Gly², Glu³]-glucandin to regulate plasma glucose concentrations was 3.2 μg/kg BW. In experiment 3, [Gly², Glu³]-OXM and [Gly², Glu³]-glucagon were injected at dose rates of 5 μg/kg BW in 5-mo-old Holstein steers. Both [Gly², Glu³]-OXM and [Gly², Glu³]-glucagon increased insulin concentration. [Gly², Glu³]-OXM potently lowered plasma glucose, but [Gly², Glu³]-glucagon did not change it. In summary, our findings clearly demonstrate that Ex-4 (1-3) fragment contributes to the regulation of glucose. [Gly², Glu³]-OXM and [Gly², Glu³]-glucandin are insulinotropic and glucose-lowering peptides. It was of interest that the substitution of the first 3 amino acids of OXM with Ex-4 (1-3) could reverse the upregulation of glucose by OXM into downregulation of glucose. In lowering glycemia, [Gly², Glu³]-OXM seemed almost as effective as Ex-4, and [Gly², Glu³]-glucandin was less profound than Ex-4. These findings contributed new insights into the hormonal regulation of glucose in ruminants. The action of [Gly², Glu³]-OXM and [Gly², Glu³]-glucandin might provide an advantage in glycemic control of insulin resistance in cattle and humans.

Conjoint regulation of glucagon concentrations via plasma insulin and glucose in dairy cows

Insulin and glucagon are glucoregulatory hormones that contribute to glucose homeostasis. Plasma insulin is elevated during normoglycemia or hyperglycemia and acts as a suppressor of glucagon secretion. We have investigated if and how insulin and glucose contribute to the regulation of glucagon secretion through long term (48 h) elevated insulin concentrations during simultaneous hypoglycemia or euglycemia in mid-lactating dairy cows. Nineteen Holstein dairy cows were randomly assigned to 3 treatment groups: an intravenous insulin infusion (HypoG, n = 5) to decrease plasma glucose concentrations (2.5 mmol/L), a hyperinsulinemic-euglycemic clamp to study effects of insulin at simultaneously normal glucose concentrations (EuG, n = 6) and a 0.9% saline infusion (NaCl, n = 8). Plasma glucose was measured at 5-min intervals, and insulin and glucose infusion rates were adjusted accordingly. Area under the curve of hourly glucose, insulin, and glucagon concentrations on day 2 of infusion was evaluated by analysis of variance with treatments as fixed effect. Insulin infusion caused an increase of plasma insulin area under the curve (AUC)/h in HypoG (41.9 ± 8.1 mU/L) and EuG (57.8 ± 7.8 mU/L) compared with NaCl (13.9 ± 1.1 mU/L; P < 0.01). Induced hyperinsulinemia caused a decline of plasma glucose AUC/h to 2.3 ± 0.1 mmol/L in HypoG (P < 0.01), whereas plasma glucose AUC/h remained unchanged in EuG (3.8 ± 0.2 mmol/L) and NaCl (4.1 ± 0.1 mmol/L). Plasma glucagon AUC/h was lower in EuG (84.0 ± 6.3 pg/mL; P < 0.05) and elevated in HypoG (129.0 ± 7.0 pg/mL; P < 0.01) as compared with NaCl (106.1 ± 5.4 pg/mL). The results show that intravenous insulin infusion induces elevated glucagon concentrations during hypoglycemia, although the same insulin infusion reduces glucagon concentrations at simultaneously normal glucose concentrations. Thus, insulin does not generally have an inhibitory effect on glucagon concentrations. If simultaneously glucose is low and insulin is high, glucagon is upregulated to increase glucose availability. Therefore, insulin and glucose are conjoint regulatory factors of glucagon concentrations in dairy cows, and the plasma glucose status is the key factor to decide if its concentrations are increased or decreased. This regulatory effect can be important for the maintenance of glucose homeostasis if insulin secretion is upregulated by other factors than high glucose such as high plasma lipid and protein concentrations at simultaneously low glucose.

Effects of herbage allowance of native grasslands in purebred and crossbred beef cows: metabolic, endocrine and hepatic gene expression profiles through the gestation-lactation cycle

Our objective was to evaluate the metabolic, endocrine and hepatic mRNA profiles through the gestation-lactation cycle in purebred (PU: Angus and Hereford) and crossbred (CR: reciprocal F1 crosses) mutliparous beef cows (n=32), grazing on two herbage allowances of native pastures (2.5 v. 4 kg dry matter/kg BW; LO v. HI) and their associations with cow's productive performance (calf birth weight, milk production and commencement of luteal activity). Cow BW, body condition score (BCS) and blood samples were collected monthly, starting at -165 days relative to calving (days), and every 2 weeks after calving until +60 days of lactation. Liver biopsies were collected at -165, -75, -45, -15±10, and +15 and +60±3 days. Metabolic, endocrine and hepatic gene expression profiles, and calf birth weight, milk yield and postpartum commencement of luteal activity were evaluated. Overall, the most pronounced changes in metabolic, endocrine and hepatic gene expression occurred during winter gestation (-165 to -45 days), when all cows experienced the onset of a negative energy balance (decreased BCS, glucose and insulin, and increased non-esterified fatty acid concentrations, P<0.008). Concentrations of insulin and IGF-I were greater (P<0.037) in HI than in LO cows. However, serum IGF-I concentrations and hepatic growth hormone receptor (GHR) and IGF1 mRNA decreased (P<0.05) during the winter gestation period only in HI cows. Although IGF-I concentrations decreased (P<0.05) during the early postpartum (-15 v.+15 days) for all cows, the typical molecular mechanism that control the uncoupling of the growth hormone-IGF1 axis during the transition period of the dairy cattle (reduced hepatic GHR1A and IGF-I mRNA) was not observed in this study. The hepatic mRNA expression of key transcripts involved in gluconeogenesis and fatty-acid oxidation were upregulated (P<0.05) during winter gestation (from -165 to -45, -15 or +15 days, depending on the cow groups). Particularly, acyl-CoA oxidase-1 mRNA was greater for CR than for PU cows during winter gestation (-75 and -45 days), and fibroblast growth factor-21 mRNA was downregulated (P<0.01) only for HI cows during the transition (-15 v. 15 days) and lactation period (+15 to +60 days, P<0.01). These results, together with the greater BCS, estimated energy intake, increased milk yield and shorter commencement of luteal activity in HI than in LO, and in CR than in PU cows (P<0.018), would indicate that HI and CR cows were able to adapt more efficiently to changes in nutrient and energy supply through the gestation-lactation cycle.

Improving Productive and Reproductive Performance of Holstein Dairy Cows through Dry Period Management

To determine the effects of dry period (DP) length on milk yield, milk composition, some blood metabolites, complete blood count (CBC), body weight and score and follicular status, twenty five primiparous and multiparous Holstein cows were assigned to a completely randomized design with DP-60 (n = 13) and DP-20 (n = 12) dry period lengths. Cows in the DP-60 produced more milk, protein, SNF, serum non-esterified fatty acids (NEFA) and beta hydroxyl butyrate acid (BHBA) compared with cows in DP-20 (p≤0.05). Serum glucose, blood urea nitrogen (BUN), urea, and glutamic oxaloacetic transaminase (GOT) were all similar among the treatments. Body Condition Score (BCS), body weight (BW), complete blood count (CBC) and health problems were similar between the treatments. Diameter of the first dominant follicle and diameter of the dominant follicle on d 14 were different among the treatments. Thus, results of this study showed that reducing the dry period length to DP-20 had a negative effect on milk production, milk composition and reproductive performance in Holstein dairy cows.

Effects of an evaporative cooling system on plasma cortisol, IGF-I, and milk production in dairy cows in a tropical environment

Access to an evaporative cooling system can increase production in dairy cows because of improved thermal comfort. This study aimed to evaluate the impact of ambient temperature on thermoregulation, plasma cortisol, insulin-like growth factor 1 (IGF-I), and productive status, and to determine the efficiency of an evaporative cooling system on physiological responses under different weather patterns. A total of 28 Holstein cows were divided into two groups, one with and the other without access to a cooling system with fans and mist in the free stall. The parameters were analyzed during morning (0700 hours) and afternoon milking (1430 hours) under five different weather patterns throughout the year (fall, winter, spring, dry summer, and rainy summer). Rectal temperature (RT), body surface temperature (BS), base of tail temperature (TT), and respiratory frequency (RF) were lower in the morning (P < 0.01). The cooling system did not affect RT, and both the groups had values below 38.56 over the year (P = 0.11). Cortisol and IGF-I may have been influenced by the seasons, in opposite ways. Cortisol concentrations were higher in winter (P < 0.05) and IGF-I was higher during spring-summer (P < 0.05). The air temperature and the temperature humidity index showed positive moderate correlations to RT, BS, TT, and RF (P < 0.001). The ambient temperature was found to have a positive correlation with the physiological variables, independent of the cooling system, but cooled animals exhibited higher milk production during spring and summer (P < 0.01).

Prepartum dietary energy intake affects metabolism and health during the periparturient period in primiparous and multiparous Holstein cows

An experiment was conducted to determine the effect of prepartum plane of energy intake on metabolic profiles related to lipid metabolism and health in blood and liver. Primiparous (n=24) and multiparous (n=23) Holsteins were randomly assigned by expected date of parturition to 1 of 3 prepartum energy intakes. A high energy diet [1.62 Mcal of net energy for lactation (NE(L))/kg; 15% crude protein] was fed for either ad libitum intake or restricted intake to supply 150% (OVR) or 80% (RES) of energy requirements for dry cows in late gestation. To limit energy intake to 100% of National Research Council requirements at ad libitum intake, chopped wheat straw was included as 31.8% of dry matter for a control diet (CON; 1.21 Mcal of NE(L)/kg of dry matter; 14.2% crude protein). Regardless of parity group, OVR cows had greater concentrations of glucose, insulin, and leptin in blood prepartum compared with either CON or RES cows; however, dietary effects did not carry over to the postpartum period. Prepartum nonesterified fatty acids (NEFA) were lower in OVR cows compared with either CON or RES cows. Postpartum, however, OVR cows had evidence of greater mobilization of triacylglycerol (TAG) from adipose tissue as NEFA were higher than in CON or RES cows, especially within the first 10 d postpartum. Prepartum β-hydroxybutyrate (BHBA) was not affected by diet before parturition; however, within the first 10 d postpartum, OVR cows had greater BHBA than CON or RES cows. Prepartum diet did not affect liver composition prepartum; however, OVR cows had greater total lipid and TAG concentrations and lower glycogen postpartum than CON or RES cows. Frequency of ketosis and displaced abomasum was greater for OVR cows compared with CON or RES cows postpartum. Controlling or restricting prepartum energy intake yielded metabolic results that were strikingly similar both prepartum and postpartum, independent of parity group. The use of a bulky diet controlled prepartum energy intake in multiparous and primiparous cows, improved metabolic status postpartum, and reduced the incidence of health problems. When metabolic profiles are considered collectively, cows overfed energy prepartum exhibited an "overnutrition syndrome" with characteristics of clinical symptoms displayed by diabetic or obese nonruminant subjects. This syndrome likely contributed to metabolic dysfunction postpartum.

Hepatic gene expression in multiparous Holstein cows treated with bovine somatotropin and fed n-3 fatty acids in early lactation

Multiparous cows were fed supplemental dietary fat and treated with bST to assess effects of n-3 fatty acid supply, bovine somatotropin (bST), and stage of lactation on hepatic gene expression. Cows were blocked by expected calving date and previous milk yield and assigned randomly to treatment. Supplemental dietary fat was provided from calving as either whole high-oil sunflower seeds (SS; 10% of dietary dry matter; n-6/n-3 ratio of 4.6) as a source of linoleic acid or a mixture of Alifet-High Energy and Alifet-Repro (AF; 3.5 and 1.5% of dietary dry matter, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids. Cows were treated with 0 (SSN, AFN) or 500 (SSY, AFY) mg of bST every 10 d from 12 to 70 d in milk (DIM) and at 14-d intervals thereafter. Liver biopsies were collected on -12, 10, 24, and 136 DIM for gene expression analysis. Growth hormone receptor (GHR), insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP3), hepatic nuclear factor 4alpha (HNF4alpha), fibroblast growth factor-21 (FGF-21), and peroxisome proliferator-activated receptor alpha (PPARalpha) were the target genes and hypoxanthine phosphoribosyltransferase (HPRT) was used as an endogenous control gene. Expression was measured by quantitative real-time reverse transcription-PCR analyses of 4 samples from each of 32 cows (8 complete blocks). Amounts of hepatic HPRT mRNA were not affected by bST or diet but were increased by approximately 3.8% in early lactation (3.42, 3.52, 3.54, and 3.41 x 10(4) message copies for -12, 10, 24, and 136 DIM, respectively). This small change had little detectable impact on the ability of HPRT to serve as an internal control gene. Amounts of hepatic GHR, IGF-I, and IGFBP3 mRNA were reduced by 1.5 to 2-fold after calving. Expression of GHR and IGF-I increased and IGFBP3 tended to increase within 12 d (by 24 DIM) of bST administration. These effects of bST persisted through 136 DIM. Hepatic HNF4alpha mRNA was not altered by DIM or any of the treatments. Abundance of PPARalpha mRNA was unchanged through 24 DIM but increased by 136 DIM. There was a trend for an interaction of bST, diet, and DIM on PPARalpha mRNA abundance from 24 to 136 DIM because the amount of PPARalpha mRNA increased in SSN, SSY, and AFN cows but was not altered in AFY cows. The amount of FGF-21 mRNA increased markedly in early lactation but, like HNF4alpha mRNA, was not affected by bST, diet, or their interactions. These results indicate 1) that bST induced increases in hepatic expression of GHR, IGF-I, and IGFBP3 when cows were in negative energy balance in early lactation, 2) there was no effect of reduced dietary n-6/n-3 content on hepatic gene expression, and 3) there was support for a potential homeorhetic role of hepatic FGF-21 via uncoupling the somatotropin-IGF-axis in early lactation.

Interrelations between glucose-induced insulin response, metabolic indicators, and time of first ovulation in high-yielding dairy cows

High-yielding dairy cows are more susceptible to metabolic and reproductive disorders than low-yielding cows. Insulin plays a pivotal role in the development of both problems. In the present study, we aimed to assess the glucose-induced insulin responses of dairy cows at different time points relative to calving and to relate this to the metabolic status and the time of first ovulation. Twenty-three healthy, multiparous Holstein-Friesian cows with a high genetic merit for milk yield were studied from 14 d prepartum to 42 d postpartum. Intravenous glucose tolerance tests were performed on -14, 14, and 42 d relative to calving to evaluate the plasma insulin and glucose responses to a glucose load, as estimated by the peak concentration, the area under the curve (AUC), and the clearance rates of insulin and glucose. Blood samples were obtained at 3-d intervals and analyzed for glucose, insulin, and nonesterified fatty acids (NEFA). The time of first ovulation was defined by transrectal ultrasonography and plasma progesterone analysis. Glucose-induced insulin AUC and peak concentration decreased and glucose clearance increased during lactation compared with the dry period. Plasma NEFA concentrations were negatively related to insulin AUC and peak concentrations. Fourteen cows ovulated within 42 d postpartum, and the remaining 9 cows suffered from delayed resumption of ovarian function. Survival analysis demonstrated that cows with lower NEFA concentrations during the dry period tended to have earlier resumption of ovarian activity. In conclusion, our data suggest a decreased plasma insulin response to glucose postpartum in high-yielding dairy cows, possibly contributing to metabolic stress during the early postpartum period. It is hypothesized that NEFA impair glucose-induced insulin secretion in dairy cows. Additionally, our results suggest the importance of lipolysis during the transition period as a risk factor for delayed ovulation.

Interrelationships between negative energy balance (NEB) and IGF regulation in liver of lactating dairy cows

In dairy cows, negative energy balance (NEB) during the early post-partum period is associated with major alterations in the growth hormone-insulin-like growth factor (GH-IGF) axis. Since the liver mediates nutrient partitioning during lactation, we aimed to determine how NEB alters the endocrine regulation of the insulin-like growth factor (IGF) system by investigating the expression of IGF family members and related steroid receptors. On the second day of lactation, cows were allocated to one of two treatments designed to produce mild (MNEB) or severe NEB (SNEB). MNEB cows (n=5) were fed ad lib grass silage supplemented with concentrate and milked x1 daily and SNEB cows (n=6) were restricted in dietary intake and milked x3 daily. Energy balance (EB) status was monitored until the second week of lactation when plasma and liver samples revealed a markedly divergent metabolic profile. At this time, plasma protein and hepatic mRNA for IGF-I was reduced in SNEB cows compared with MNEB cows. Both levels of expression correlated highly when data from all animals was pooled (r=0.963; P<0.01). SNEB cows also exhibited reduced hepatic expression for transcripts encoding IGF-1R, IGF-2R, IGF binding proteins (IGFBPs) -3, -4, -5, -6, acid labile subunit, and receptors for oestrogen (ERalpha) and growth hormone (total GHR and 1A variant), while the expression of IGFBP-2 was elevated. Expression of mRNA for IGF-II, IGFBP-1 and receptors for insulin (A/B) and glucocorticoid (alpha) was unaffected by EB. Results demonstrate that SNEB affects hepatic synthesis of IGF-I, and other components known to modulate the bioavailability and stability of circulating IGF-I.

Effects of sow nutrition on maternal and foetal serum growth factors and on foetal myogenesis

The objective of this study was to examine the effect of increased maternal nutrition in early to mid gestation on changes in serum growth factors of the sow and foetuses. Furthermore, the effect of the foetal sera on in vitro proliferation and differentiation of porcine primary myoblasts was examined. Pregnant sows were either given food either in accordance to requirements (2 kg/day; C) until day 50 or 70 of gestation or given food in accordance to requirements until day 25 and then ad libitum (A) until day 50 or 70. Sows were slaughtered at the Institute's veterinary controlled slaughterhouse at day 50 or 70, respectively. Serum from sows and pools of cord-blood serum from each litter were analysed for glucose, lactate, insulin, insulin-like growth factor (IGF; IGF-1 and -2) and IGF binding proteins (IGFBPs). IGF-1 (P < 0·001) was higher in A compared with C sows, and a 28-kDa IGFBP (P < 0·05) and a 24-kDa IGFBP (P < 0·05) was higher in serum from day 70 compared with day 50 sows. There was no significant effect of food intake on growth factor concentrations in foetal serum or on serum-induced proliferation and differentiation of myoblasts. A 28 kDa IGFBP, IGFBP-2 and -3 were all higher (P < 0·06) and serum-induced proliferation (P < 0·001) and differentiation (P < 0·1) lower at day 70 than day 50. Maternal food intake did not influence the DNA and RNA concentrations and the CPK activity in the foetal longissimus dorsi muscle. The glucose concentration in the liver was higher in C than A foetuses at day 70 of gestation, but not at day 50.

In conclusion, no significant effects of maternal nutrition were found on serum growth factor concentrations in the foetuses or on serum-induced proliferation and differentiation of primary myoblasts.

Effects of Feeding Fish Meal and n-3 Fatty Acids on Milk Yield and Metabolic Responses in Early Lactating Dairy Cows

The study was designed to test the effects of feeding fish meal (FM) and specific n-3 fatty acids on milk yield and composition, dry matter intake, plasma concentrations of metabolic hormones and metabolites, and liver triglyceride accumulation in early lactating cows. From 5 to 50 d in milk (DIM), cows were fed diets that were isonitrogenous, isoenergetic, and isolipidic containing none (control), 1.25, 2.5, or 5% menhaden FM or 2.3% Ca salts of fish oil fatty acids (CaFOFA). Milk yield (48.2, 49.8, 48.6, 53.5, and 52.2 +/- 1.0 kg/d, respectively) and dry matter intake (22.7, 22.8, 23.0, 23.8, and 24.7 +/- 0.5 kg/d, respectively) differed among diets. Average daily plasma glucose concentration (53.4, 55.3, 51.1, 57.6, and 57.3 +/- 1.3 mg/dL, respectively) was also affected by diet, and plasma insulin concentration was increased by 5% FM and 2.3% Ca-FOFA. At 25 and 50 DIM, blood was collected before feeding and hourly for 11 h after feeding. Plasma glucose concentrations in cows during the day were similar among diets at 25 DIM, but differed at 50 DIM (54.6, 54.4, 52.4, 60.5, and 58.3 +/- 1.4 mg/dL for 0, 1.25, 2.5, and 5% FM or 2.3% CaFOFA, respectively). Plasma insulin was increased in cows fed 5% FM and 2.3% CaFOFA at 25 DIM and was similar among diets at 50 DIM. Dietary treatments had no significant effect on milk composition, energy balance, or on daily plasma concentrations of nonesterified fatty acids, beta-hydroxybutyrate, and urea. Plasma aspartate aminotransferase and hepatic triglyceride concentration in cows did not differ among diets at 21 DIM. Results from this experiment demonstrate that dietary supplementation with FM or n-3 polyunsaturated fatty acids in early lactating dairy cows significantly increased milk yield and DMI with no change in milk composition.

Decreased insulin response in dairy cows following a four-day fast to induce hepatic lipidosis

Negative energy balance has been implicated in the development of fatty liver, insulin resistance, and impaired health in dairy cows. A 4-d fasting model previously was reported to increase liver triglycerides more than 2.5-fold. The purpose of the present study was to evaluate insulin response in this fasting model. Nonlactating, nonpregnant Holstein cows were fasted for 4 d (6 cows) or fed continuously as control cows (4 cows). Samples were collected 5 d before fasting, during fasting, and immediately after the 4-d fast, 8 d after the fast, and 16 d after the fast. Fasted cows had greater liver triglyceride content (49.4 vs. 16.2 mg/g, wet-weight basis) at the end of the fasting period compared with control cows. Fasted cows also had increased plasma nonesterified fatty acid (NEFA) concentrations (1.24 vs. 0.21 mmol/L) and increased plasma beta-hydroxybutyrate (BHBA) concentrations at the end of the fasting period. Liver triglyceride, plasma NEFA, and plasma BHBA in fasted cows returned to prefasting concentrations by the end of the experiment. Plasma glucose concentrations were not affected by fasting. Plasma insulin concentrations were decreased (6.3 vs. 14.1 microU/mL) and insulin-stimulated blood glucose reduction was decreased (24.9 vs. 48.6%) in the fasted cows compared with control cows at the end of the fast, indicating reduced insulin response. Insulin response was negatively correlated with plasma NEFA and liver triglycerides. Decreased insulin response may be an important complication of negative energy balance and hepatic lipidosis.

The effects of dry period versus continuous lactation on metabolic status and performance in periparturient cows

It has been argued that dairy cows with a high genetic milk production potential can maintain high milk production even with total omission of the dry period. Further, when omitting the dry period, cows are believed to experience fewer metabolic changes during the transition from late gestation to early lactation compared with cows having a traditional dry period. The performance and metabolic response to omission of the dry period for cows with an expected peak milk yield higher than 45 kg/d were studied in 28 Holstein dairy cows. The cows were followed in late gestation and in the subsequent 5 wk of early lactation. Fourteen cows were milked through late gestation (CM) and another 14 dairy cows underwent a 7-wk dry period (DRY). In the early lactation period, the cows had the same dry matter (DM) intake but cows in the CM group had a 22% reduction in milk yield compared with the cows in the DRY group. At calving, the experimental groups had the same average body weight and body condition score and there were no significant differences in body weight and body condition score changes in early lactation. However, the cows in the CM group compared with the cows in the DRY group had a higher plasma concentration of glucose and insulin and a lower plasma concentration of nonesterified fatty acids and beta-hydroxybutyrate in the following 5 wk of early lactation. Furthermore, the cows in the CM group had lower liver triacylglycerol concentration and higher liver glycogen concentration in the following early lactation. It is concluded that, even in dairy cows with an expected peak milk yield above 45 kg/d, omission of the dry period results in a relatively high reduction in milk yield in the following early lactation. Furthermore, these cows are in less metabolic imbalance in the following early lactation.

Reducing or eliminating the dry period of dairy cows

This review considers the research that has been conducted recently on reducing the length of the dry period of dairy cows, with particular emphasis on the effects of eliminating the dry period altogether. Milk yield in the subsequent lactation is reduced by up to 25%, but this loss is offset to some degree by the milk produced when cows would otherwise be dry. The lower subsequent milk yield in cows continuously milked is most likely to be a consequence of changes in the mammary gland during late gestation rather than insufficient feed or body condition to maintain milk synthesis. Shortening or eliminating the dry period may result in a lower incidence of metabolic problems post-partum, and a reduced negative energy balance in early lactation due to the maintenance of dietary intake while milk yields and body condition loss are reduced. The reductions in both body condition loss and negative energy balance may have a beneficial influence on reproductive performance. However, it is concluded that more research, particularly with cows that graze pasture during lactation, together with an economic appraisal, is needed before it could be recommended that Australian dairy farmers change their current dry period practices, particularly if continuous milking was to be considered.

To what extent do variabilities in hormones, metabolites and energy intake explain variability in milk yield?

The objective of the present paper is to describe the extent to which variability in milk yield can be explained by variability in plasma hormones, metabolites and DE intake. Results from a study including 317 cows and 634 lactations were used. Detailed registration of performance was carried out on these cows and 10,809 plasma samples analyzed for selected hormones and metabolites. Univariate analysis was carried out on energy-corrected milk yield and concentrations of selected plasma hormones (insulin, growth hormone (GH) and triiodothyronine (T3)), metabolites (non-esterified fatty acids (NEFA)), glucose, beta-hydroxybutyrate (BOHB) and urea nitrogen (BUN), and digestible energy intake (DE intake) to estimate between-cow variation through lactations. Partial least square (PLS) models were subsequently run to estimate the extent to which between-cow differences in energy-corrected milk yield could be explained by between-cow differences in hormone concentrations, metabolite concentration or DE intake. The between-cow variability in energy-corrected milk yield and the hormones and metabolites were generally found to be considerable and total variance changed through lactation, particularly for GH, T3, NEFA and BOHB. In this study, the total variance was highest in third lactation cows. When analyzed separately using partial least square models, hormones, metabolites and DE intake accounted for 24, 25 and 26% of the variability in ECM, respectively. Insulin and glucose were the single most important predictors among the selected hormones and metabolites. When including both the hormones and metabolites, the model explained 36% of the between-cow variability in ECM and this figure was increased to 53% if DE intake was also included. The lack of additivity in the variability explained shows that hormones, metabolites and DE intake were correlated illustrating the integration and orchestration of metabolism and intake. Perspectives of the analysis for use in prevention of diseases and reproduction are briefly discussed.

Pregnancy rates and metabolic profiles in cattle treated with propylene glycol prior to embryo transfer

The objective of this study was to determine the effect of a sustained propylene glycol administration to recipients of frozen/thawed in vivo derived bovine embryos. Heifers were treated with oral propylene glycol for the last 20 days before embryo transfer (n = 142), and untreated as controls (n = 133). Progesterone, insulin, insulin-like growth factor-I, glucose, urea and triglyceride were analysed in blood on Day 0 and Day 7 of the estrous cycle corresponding to embryo transfer. The heifers were selected as recipients when showing progesterone levels <2.0 ng/ml (Day 0) and >2.5 ng/ml (Day 7), according to corpus luteum quality on Day 7 by technicians unaware of animals treated. Within treated animals, significantly more recipients were selected, and increased progesterone, corpus luteum quality, pregnancy and calving rates were recorded. Day 7 progesterone concentrations were higher in heifers treated and transferred. Propylene glycol increased insulin and insulin-like-growth factor-I, but glucose, urea and triglyceride did not vary. Furthermore, insulin-like-growth factor-I, glucose and triglyceride increased at estrous time, but urea decreased and insulin remained unaltered. Together with the sustained gain in pregnancy rates throughout the experiment (2 years), other evidences suggested that the observed effects did not rely on nutritional deficiency. Thus, propylene glycol improved pregnancy rates after embryo-transfer, and progesterone, insulin and insulin-like-growth factor-I are probably involved in this effect.

Effect of energy density in the diet and milking frequency on plasma metabolites and hormones in early lactation dairy cows

The effects of energy density in the diet [low = 0.86 SFU/kg dry matter (DM) or high = 1.06 SFU/kg DM] and daily milking frequency (two or three times) in early lactation on plasma concentrations of metabolites and hormones were evaluated in 40 Holstein dairy cows arranged in a 2 x 2 factorial block design. The four treatment combinations were L2, L3, H2 and H3, and the experimental period comprised the first 8 weeks of lactation. Plasma glucose, insulin and insulin-like growth factor (IGF)-I concentrations were on average 8 (3.43 versus 3.19 mmol/l), 114 (41.6 versus 19.4 pmol/l) and 60% (91.9 versus 57.4 ng/ml) higher, whereas beta-hydroxybutyrate (BOHB), plasma urea nitrogen (PUN) and growth hormone (GH) concentrations were on average 18 (0.73 versus 0.89 mmol/l), 14 (7.18 versus 8.35 mmol/l), and 63% (1.0 versus 2.6 ng/ml) lower for cows fed diet H than for cows fed diet L. Cows milked three times daily had a 6% (3.20 versus 3.42 mmol/l) lower plasma glucose concentration and a 19% (0.88 versus 0.74 mmol/l) higher plasma concentration of BOHB compared with cows milked two times daily. Plasma non-esterified fatty acid (NEFA) concentration was not affected by either treatment. Overall, it is concluded that increasing the daily milking frequency creates a higher metabolic imbalance in early lactation. Cows in early lactation will benefit from receiving a high energy density diet and thereby avoid a too high metabolic imbalance when mobilizing body tissue in support of milk production.

Insulin increases the abundance of the growth hormone receptor in liver and adipose tissue of periparturient dairy cows

After parturition, increased growth hormone (GH) secretion is important to preserve the metabolic homeostasis of energy-deficient dairy cows. Elevated plasma GH promotes lipid mobilization from adipose tissue, but paradoxically, is associated with depressed concentration of insulin-like growth factor-I (IGF-I), a growth factor produced in a GH-dependent fashion in liver. Primary factors regulating GH responses of liver and adipose tissue are poorly understood in periparturient dairy cows. Consistent with insulin being such a factor, its plasma concentration declined concomitantly with net energy balance (EB) and with plasma IGF-I in a group of 9 periparturient dairy cows. To test the role of insulin in regulating cellular determinants of GH responsiveness, hyperinsulinemic-euglycemic clamps were performed on 6 dairy cows in late pregnancy (28 d prepartum) before the reductions in EB, insulin, and IGF-I were initiated, and when they were completed in early lactation (10 d postpartum). Infusion of insulin nearly doubled the plasma concentration of IGF-I (P < 0.001) and hepatic levels of IGF-I mRNA during both states (P < 0.05). In liver, these responses were associated with increased abundance of the GH receptor protein (GHR; P < 0.05), whereas the abundance of intracellular mediators of GH actions (JAK2, STAT5, or STAT3) remained unaffected. Insulin also doubled GHR abundance in adipose tissue (P < 0.01), indicating that this effect is not liver specific. These results raise the possibility that insulin regulates the efficiency of GH signaling in liver and adipose tissue of dairy cows by acting as a rheostat of GHR synthesis.

The housekeeping genes GAPDH and cyclophilin are regulated by metabolic state in the liver of dairy cows

Steady-state levels of mRNA are often used to infer treatment effects on the levels of the corresponding protein. In addition, an internal standard RNA is usually measured to document specificity of treatment and to correct for intersample variation. Our objective was to evaluate whether glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and cyclophilin could be used as internal standards when studying changes in hepatic gene expression in dairy cows. Hepatic expression of GAPDH and cyclophilin was measured in 6 cows in late pregnancy (28 d prepartum) and early lactation (10 d postpartum). Each gene displayed 2- to 3-fold higher expression in early lactation than in late pregnancy. Next, we determined whether negative energy balance alone or in combination with exogenous growth hormone could mimic the effects of early lactation. Late-lactating cows were fed 120% of predicted energy requirements or 33% of maintenance requirements. During each feeding period, cows were administered excipient or bovine somatotropin in a single-reversal design with 4-d periods separated by a 2-d interval. Underfeeding increased hepatic expression of GAPDH and cyclophilin by 1- to 2-fold, whereas bovine somatotropin had no effect. Finally, the effects of insulin were studied by performing hyperinsulinemic-euglycemic clamps in late pregnancy (28 d prepartum) and early lactation (28 d postpartum). Hyperinsulinemia reduced GAPDH expression in both states, and cyclophilin expression in early lactation. In conclusion, GAPDH and cyclophilin are regulated in the liver of dairy cows and should not be used to standardize hepatic gene expression in studies involving the transition period, undernutrition, and sustained changes in plasma insulin.

Response of Plasma Leptin Concentration to Jugular Infusion of Glucose or Lipid Is Dependent on the Stage of Lactation of Holstein Cows

In this study we investigated the hormonal and metabolite responses to isoenergetic jugular infusions of glucose or lipid in early- and late-lactation Holstein cows. Six Holstein cows were used in a replicated Latin square design with jugular infusions of either 1) control (CON; saline), 2) glucose (GLU; 50% dextrose) or 3) lipid (LIP; 20% Intralipid). Treatments did not affect dry matter intake, with the exception of a hypophagic effect of LIP in late lactation. The GLU-induced hyperglycemia and hyperinsulinemia were greater in late-lactation than in early-lactation cows. The GLU treatment did not affect plasma leptin and insulin-like growth factor-1 (IGF-1) concentrations in early-lactation cows, but it increased them in late-lactation cows. The LIP treatment did not affect plasma leptin, insulin and IGF-1 concentrations in early-lactation cows, despite a marked LIP-induced increase in plasma nonesterified fatty acid and beta-hydroxybutyrate concentrations and a reduction in growth hormone (GH) concentration. Compared with the delayed leptin response to GLU, the stimulatory effect of LIP on leptin secretion in late-lactation cows was relatively rapid and occurred in the absence of any significant changes in plasma insulin, IGF-1 or GH. We propose that insulin-mediated glucose metabolism may be involved in the stimulatory effects of glucose on leptin secretion in late-lactation animals but that the stimulatory effects of lipid are independent of insulin or IGF-1. In early-lactation animals a strong inhibitory effect of GH on leptin expression and release, in addition to low adipose reserves and/or energy balance, might override any short-term stimulatory effect of glucose or lipid on leptin secretion.

Diurnal variation and the effect of feed restriction on plasma and milk metabolites in TMR-fed dairy cows

The objective was to study the diurnal variation in metabolites in plasma and milk of dairy cows fed total mixed rations (TMR) with a low-energy (LE) or high-energy content (HE) expected to give a minor and a major diurnal variation, respectively. Further, the purpose was to quantify and compare the responses in plasma and milk parameters when cows changed from ad libitum to restrictive feeding. Eight multiparous, early-lactating Danish Holstein cows were used in a cross-over design with two consecutive 14-day periods. Blood and milk samples were collected hourly on day 11 of each period and on days 12-14 of each period, the cows were fed restrictively (65% of ad libitum dry-matter intake). The concentration of beta-hydroxybutyrate (BHB) in plasma was significantly higher in the evening for cows fed the HE TMR, than for cows fed the LE TMR. There was a significant diurnal variation in BHB in milk, with the highest concentrations between milkings and the lowest concentrations at milking. Non-esterified fatty acids (NEFA) in plasma showed significant diurnal variation that was caused by high concentrations in the morning. Plasma glucose did not show any diurnal variation. It has been argued that feeding a TMR removes diurnal changes related to feeding, which is contrary to earlier diurnal studies where concentrates have been fed twice daily. Feed restriction increased (P < 0.001) NEFA and BHB in plasma by 121 and 90%, respectively, while the glucose concentration decreased (P < 0.001) by 19%. Milk concentrations of BHB, citrate and fat increased (P < 0.001) by 163, 11 and 26%, respectively, because of feed restriction, while there were no changes in milk protein and lactose. The relatively high increase in BHB during feed restriction suggests that BHB is more advantageous as a milk indicator of metabolic status in dairy cows than citrate and fat.

Effect of energy density in the diet and milking frequency on hepatic long chain fatty acid oxidation in early lactating dairy cows

The objective of this study was to examine the effects of diet energy density (high versus low) and increased milk yield, induced by increased milking frequency (two versus three times daily), on the hepatic status of triacylglycerol (TAG) and glycogen content and hepatic long chain fatty acid (LCFA) oxidation capacity in early lactation in a 2 x 2 factorial design. Forty multiparous Danish-Holstein dairy cows were used from 8 weeks before to 8 weeks after calving. Liver biopsies and blood samples were taken in weeks -2, 2, and 7 from calving. The cows fed the high energy density diet, compared with the cows fed the low energy density diet, had an 18 and 28% higher milk production and net energy intake, respectively. Milk yield was increased by 10% when the cows were milked three times compared with twice daily. Complete (CO2 production) and incomplete (ketone body production) LCFA oxidation capacity in the liver were 35 and 32% higher, respectively, and liver TAG content was 48% lower for the cows fed the high energy density diet compared with the low energy density diet. Overall there was no effect of milking frequency on liver parameters. However, a significant interaction between diet and milking frequency showed that the cows milked three times daily and fed the low energy density diet had the lowest liver LCFA oxidation (CO2 and ketone body) capacity. Furthermore, these cows had the numerically highest liver TAG content. The results for liver LCFA metabolism are discussed in relation to the plasma concentration of metabolites and insulin. In conclusion, cows in early lactation given a high energy density diet will, in general, have a lower risk of high TAG infiltration in the liver.

Effects of hyperinsulinaemia under euglycaemic condition on liver fat metabolism in dairy cows in early and mid-lactation

The objective was to examine the effects of insulin under euglycaemic conditions on liver long chain fatty acids (LCFA) metabolism with special focus on the aetiology of hepatic lipidosis in early lactation. A 4-day hyperinsulinaemic-euglycaemic clamp (clamp) was conducted on four dairy cows starting in weeks 4 and 17 postpartum. Insulin was infused continuously (1 microg/kg BW per h) and a 50% glucose solution was infused to maintain euglycaemia. Liver biopsies were taken 6 days before, the last day of, and 5 days after the clamp, and blood samples were taken in the same period. In the liver tissue, the relative triglyceride content decreased (P < 0.01) and the glycogen content increased (P < 0.0001) in response to the clamp. Hepatic in vitro palmitate oxidation capacity was lowest during the clamp period and could be explained by a significant decrease in incomplete oxidation (ketogenesis) (P < 0.04) and a tendency to a decreased complete oxidation of palmitate (P < 0.10). Plasma non-esterified fatty acids concentration was decreased during the clamp in early lactation (P < 0.05) but there was no effect on the mid-lactation clamp. The present study shows that increased insulin under euglycaemic conditions seems to depress hepatic LCFA oxidation capacity. However, in terms of preventing hepatic lipidosis, the anti-lipolytic effect of insulin on adipose tissue, which results in decreased mobilization of and hence hepatic load with LCFA, appears more important.