Oleic acid abomasal infusion limits lipolysis and improves insulin sensitivity in adipose tissue from periparturient dairy cows

Excessive adipose tissue (AT) lipolysis around parturition in dairy cows is associated with impaired AT insulin sensitivity and increased incidence of metabolic diseases. Supplementing cows with oleic acid (OA) reduces circulating biomarkers of lipolysis and improves energy balance. Nevertheless, it is unclear if OA alters lipid trafficking in AT. In the liver and skeletal muscle, OA improves mitochondrial function and promotes lipid droplet formation by activating perilipin 5 (PLIN5) and peroxisome proliferator-activated receptor α (PPARα). However, it is unknown if this mechanism occurs in AT. The objective of this study was to determine the effect of OA on AT lipolysis, systemic and AT insulin sensitivity, and AT mitochondrial function in periparturient dairy cows. Twelve rumen-cannulated Holstein cows were infused abomasally following parturition with ethanol (CON) or OA (60 g/d) for 14 d. Subcutaneous AT samples were collected at 11 ± 3.6 d before calving (-12 d), and 6 ± 1.0 d (7 d) and 13 ± 1.4 d (14 d) after parturition. An intravenous glucose tolerance test was performed on d 14. Adipocyte morphometry was performed on hematoxylin and eosin-stained AT sections. The antilipolytic effect of insulin (1 μg/L) was evaluated using an ex vivo explant culture following lipolysis stimulation. PLIN5 and PPARα transcription and translation were determined by real-time quantitative PCR and capillary electrophoresis, respectively. RNA sequencing was used to evaluate the transcriptomic profile of mitochondrial gene networks. In CON cows, postpartum lipolysis increased the percentage of smaller (<3,000 µm²) adipocytes at 14 d compared with -12 d. However, OA limited adipocyte size reduction at 14 d. Likewise, OA decreased lipolysis plasma markers nonesterified free fatty acids and β-hydroxybutyrate at 5 and 7 d. Over the 14-d period, compared with CON, OA increased the concentration of plasma insulin and decreased plasma glucose. During the glucose tolerance test, OA decreased circulating glucose concentration (at 10, 20, 30, 40 min) and the glucose clearance rate. Moreover, OA increased insulin at 10 and 20 min and tended to increase it at 30 min. Following lipolysis stimulation, OA improved the antilipolytic effect of insulin in the AT at 14 d. PLIN5 and PPARA gene expression decreased postpartum regardless of treatment. However, OA increased PLIN5 protein expression at 14 d and increased PPARA at 7 and 14 d. Immunohistochemical analysis of AT and RNA sequencing data showed that OA increased the number of mitochondria and improved mitochondrial function. However, OA had no effect on production and digestibility. Our results demonstrate that OA limits AT lipolysis, improves systemic and AT insulin sensitivity, and is associated with markers of mitochondrial function supporting a shift to lipogenesis in AT of periparturient dairy cows.

The Influence of Energy Balance, Lipolysis and Ketogenesis on Metabolic Adaptation in Cows Milked Twice and Three Times Daily

Increasing milk production requires increasing milking frequency (MF) from two times daily (2X) to three (3X) or more. High milk production leads to negative energy balance (NEB) and homeorhesis, characterized by lipolysis, ketogenesis, and endocrinological changes. The relationship among energy balance (EB), lipolysis, and ketogenesis with endocrine and metabolic parameters in blood of cows milked 2X and 3X daily was studied. Holstein Friesian cows milked 2X (n = 45) and 3X (n = 45) were analyzed, with approximately 50% of cows in each group in positive EB (PEB) and 50% in NEB. After determining EB, blood samples were collected from all cows and blood serum was analyzed for non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), glucose (GLU), cholesterol (CHOL), triglycerides (TGC), total bilirubin (TBIL), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), calcium (Ca), inorganic phosphate (P), total protein (TPROT), albumin (ALB), urea, insulin (INS), T3, T4, and cortisol (CORT), and the RQUICKIBHB index of insulin resistance was calculated. Cows milked 3X in NEB represent a special cluster that partially overlaps with cows milked 2X in NEB and has no contact points with cows in PEB. Cows milked 3X had higher levels of NEFA, BHB, AST, GGT, TBIL, and CORT and lower levels of GLU, Ca, INS, and T4. Cows milked 3X in NEB had higher levels of NEFA, BHB, AST, GGT, TBIL, and CORT and lower levels of GLU, CHOL, TGC, TPROT, P, INS, RQUICKIBHB, and T3 compared with cows milked 2X in NEB and cows in PEB. In cows milked 3X, lipolysis and ketogenesis were much more prominent, and EB levels were lower, implying a pronounced shift in homeorhesis. Metabolic and endocrinology parameters were determined mainly by the values of EB, NEFA, and BHB in cows milked 3X in NEB compared with other categories of cows. The results confirm the peculiarity of metabolic adaptation in cows with increased MF, characterized not only by differences in the concentration of metabolites but also in their interactions.

Effects of vitamin D3 injection in close-up period on insulin resistance and energy balance in transition dairy cows

Background

Many studies in dairy cows are towards calcium homeostasis and there is a lack of knowledge about the effect of vitamin D in preventing insulin resistance and improving energy balance in the transition period of dairy cows.

Methods

The trial was conducted in a commercial dairy farm with about 1500 lactating cows in Tehran province, Iran. Twenty‐four Holstein cows had been randomly selected and divided into control and treatment groups. In the treatment group, 12 cows, received a single dose of 8,000,000 IU vitamin D3 intramuscularly and in the control group, 12 cows were injected placebo (distilled water) 2–8 days before the expected calving time. Blood samples were collected between 8 and 10 AM 2 h after feeding on 21 and 7 days before calving and 1,3,7,15 and 30 days after calving. 25(OH)vitamin D, insulin‐like growth factor 1 (IGF‐1), insulin, nonesterified fatty acid (NEFA), β‐hydroxybutyric acid (BHBA), albumin, total protein, glucose, urea, triglyceride, cholesterol and aspartate amino transferase (AST) were measured by commercially available kits. The insulin resistance index was calculated.

Results

Vitamin D3 injection significantly affected the amounts of 25(OH) vitamin D, urea, insulin and insulin resistance index (p ≤ 0.05). On the other hand, the amounts of glucose, NEFA, BHBA concentration and AST activity were higher in control group (p ≤ 0.05). Time had a significant effect on the amounts of most measured variables except IGF‐1 and insulin. There were no group and time interactions for measured variables.

Conclusion

It seems that injection of vitamin D3 in close up period influenced lipolysis potentially modifying energy metabolism and resulted in reducing insulin resistance.

Glucose, insulin, and cortisol concentrations and glucose tolerance test in Holstein cows with inactive ovaries

A total of 60 healthy (the control group) and 30 anestrous Holstein cows with inactive ovaries (the case group) from three dairy farms around Tehran were randomly selected and diagnosed to determine the concentrations of glucose, insulin, and cortisol, and the rate of the insulin resistance disorder in them. Primarily, serum samples were obtained from all animals, and the concentrations of glucose, insulin, and cortisol were measured in a laboratory. Thereupon, the glucose tolerance test (GTT) was implemented. Before the implementation of the GTT, the median of serum glucose levels (62 mg/dl), insulin (7.16 μIU/ml), and cortisol (2.5 μg/dl) was estimated in healthy cows. The median of serum glucose levels (68.5 mg/dl, p = 0.00009) was higher, and serum insulin (6.1 μIU/ml, p = 0.025) and cortisol (1.1 μg/dl, p = 0.00029) levels were lesser in the anestrous cows when estimated simultaneously. After the implementation of GTT, the median of serum glucose concentrations in one (120 mg/dl), two (73.5 mg/dl), and three (63.5 mg/dl) hours after the glucose injection was estimated in healthy cows. The findings also showed that the median of serum glucose levels was lesser in one (100 mg/dl, p = 0.015), similar in two (77.5 mg/dl, p = 0.9), and higher in three (70 mg/dl, p = 0.012) hours after the glucose injection in anestrous cows. In conclusion, higher serum glucose, lesser insulin and cortisol concentrations, and the different correlation between serum glucose and insulin levels before the GTT were detected in anestrous cows. The pattern of glucose changes also differed in anestrous cows after the GTT.

Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows

The objective for this study was to determine the effect of glucose dose and days following peak milk yield on plasma glucose, serum insulin, and plasma nonesterified fatty acids (NEFA) kinetics during an intravenous glucose tolerance test (IVGTT) in lactating dairy cattle. Six lactating Holstein dairy cows (3 primiparous and 3 multiparous) were assigned to 2 squares and received 0.092, 0.15, or 0.3 g of glucose/kg of body weight (BW) during an IVGTT at 74 and 221 d in milk (DIM), representing early (post-peak) lactation and mid lactation, respectively. Treatments were applied in a replicated Latin square design using contiguous 7-d periods within each stage of lactation. Milk production and dry matter intake were determined daily during the first 6 d of each period. The IVGTT was performed on d 7. For the IVGTT, cows were prepared with indwelling catheters in each jugular vein, and blood samples were collected at -15, -10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to the glucose infusion. Samples were analyzed for plasma glucose, serum insulin, and plasma NEFA concentrations. Increasing the glucose dose during the IVGTT increased plasma glucose area under the curve (AUC), decreased glucose half-life, and increased maximal plasma glucose concentrations in plasma during the IVGTT. Greater glucose dose during the IVGTT elevated serum insulin AUC and increased nadir NEFA concentrations. Maximal plasma glucose concentration during the IVGTT was lower, whereas maximum NEFA concentration, NEFA AUC, and NEFA clearance rate were greater at 74 than at 221 DIM. Only glucose half-life was responsive to stage of lactation × glucose dose effects during the IVGTT, and the decrease in glucose half-life with increasing glucose dose was greater at 74 than at 221 DIM. Glucose AUC was greater and NEFA AUC lower for cows at 74 than at 221 DIM. For the doses tested, a glucose dose greater than 0.092 g/kg of BW resulted in peak blood glucose concentration that exceeded the previously reported renal glucose excretion threshold of 8.3 mM. There is a need for accompanying data to determine if this is the case for the glucose doses evaluated in this experiment. Based on maximal peak glucose concentrations and effects on glucose half-life, we identify 0.092 g of glucose/kg of BW (0.46 g/kg of metabolic body weight) as the preferred dose for the IVGTT for cows at 74 and 221 DIM in this study.

Effects of auditory and visual stimuli on glucose metabolism in Holstein dairy cattle

Background

Standardization of the intravenous glucose tolerance test (ivGTT) in cattle has received little attention despite its widespread use to monitor glucose metabolism. The impact of management practices including several sensorial stimuli on test responses has not yet been described in young cattle. The objective of this study was to analyze the effects of noise exposure, and visual food stimuli in combination with physical restraint on ivGTT and insulin traits in Holstein cattle. A total of 108 ivGTT (6 tests per animal) were performed in bulls (n = 6), steers (n = 6), and heifers (n = 6) aged 312 to 344 days. The main parameters analyzed for glucose and insulin included: basal concentration (G0, Ins0), maximum concentration (GMAX, InsMAX), and final concentration at 63 min (G63, Ins63), glucose and insulin area under the curve (GAUC, InsAUC), and glucose half-life time (GHLT). Noise stimuli were induced by playing rock music at approximately 90 dB either before (NI) or immediately after glucose injection (NII). Visual food stimuli were induced by feeding the neighboring animals while the tested animal was restrained in a headlock.

Results

Almost all glucose and insulin traits were affected by gender (P< 0.05) whereas the factor with least impact on ivGTT was NI. InsMAX and InsAUC were affected (P < 0.002) by all factors analyzed. GHLT and G63 were affected by gender and noise with higher values in bulls when compared to steers and heifers. Furthermore, InsAUC and InsMAX values derived from NII significantly differed in bulls when compared to steers and heifers. Significantly higher values for G0 (P < 0.001), InsMAX (P < 0.001) and InsAUC (P = 0.001) were observed when exposed to the visual food stimulus whereas GMAX (P = 0.02) and GAUC (P = 0.04) decreased. Higher Ins63 values were observed in bulls exposed to the visual food stimulus when compared to heifers.

Conclusions

Short-term exposure to noise and visual food stimuli might lead to variations in glucose metabolism and insulin secretion which emphasizes the necessity to avoid practices involving auditory or visual stimuli prior to or during the conduction of an ivGTT.

Evaluation of glucose dose on intravenous glucose tolerance test traits in Holstein-Friesian heifers

Glucose metabolism in dairy and beef cattle has received considerable attention because balanced blood glucose is essential for numerous processes, such as milk production and general health. The glucose tolerance test measures the ability of an organism to regulate blood glucose levels. Glucose half-life time (GHLT) has high heritability and could serve as a potential parameter to breed for metabolic resistance. However, studies focusing on identification of an adequate glucose dose have not yet been conducted in cattle. The objective of this study was to analyze the effect of 5 different glucose doses (0.5, 1, 1.5, 2, and 3 g/kg of body weight^0.75) on intravenous glucose tolerance test (ivGTT) traits and insulin responses in nongestating heifers. A total of 150 tests were performed in 30 Holstein-Friesian heifers aged 13 to 15 mo. Blood samples were obtained every 7 min after glucose injection until min 63. Glucose traits and insulin parameters included blood serum glucose and insulin concentration at min 0 (basal concentration), min 7 to 21 (peak glucose and insulin concentration), and min 63 (last sampling) relative to glucose administration, glucose and insulin area under the curve (GAUC and IAUC), and GHLT estimated between min 14 and 42. Serum glucose and insulin concentrations were measured according to the hexokinase colorimetric method and radioimmunoassay, respectively. Generalized linear mixed model was used to test for significant differences in ivGTT traits, insulin responses, and glucose elimination rates (k) over time at different glucose doses. Maximum glucose and insulin concentrations at min 63 increased with higher glucose doses. Significantly lower GHLT were obtained at increasing glucose doses, whereas GAUC and IAUC were significantly higher at increasing doses. The k values were affected by glucose dose and by time interval. Glucose dose greatly affected most ivGTT traits, insulin responses, and glucose elimination rates. Therefore, researchers should standardize their methods to achieve repeatable results and use the same time points for GHLT calculation. Higher glucose doses (≥1.5 g/kg of body weight^0.75) triggered glucose concentrations above the glucose renal threshold during the initial 42 min, whereas the lowest glucose concentration failed to induce a maximum insulin response. Further research is necessary to determine an adequate dose inducing maximum insulin responses with minimum renal glucose losses.

Adipose tissue lipolysis and remodeling during the transition period of dairy cows

Elevated concentrations of plasma fatty acids in transition dairy cows are significantly associated with increased disease susceptibility and poor lactation performance. The main source of plasma fatty acids throughout the transition period is lipolysis from adipose tissue depots. During this time, plasma fatty acids serve as a source of calories mitigating the negative energy balance prompted by copious milk synthesis and limited dry matter intake. Past research has demonstrated that lipolysis in the adipose organ is a complex process that includes not only the activation of lipolytic pathways in response to neural, hormonal, or paracrine stimuli, but also important changes in the structure and cellular distribution of the tissue in a process known as adipose tissue remodeling. This process involves an inflammatory response with immune cell migration, proliferation of the cellular components of the stromal vascular fraction, and changes in the extracellular matrix. This review summarizes current knowledge on lipolysis in dairy cattle, expands on the new field of adipose tissue remodeling, and discusses how these biological processes affect transition cow health and productivity.

Embryo production in heifers with low or high dry matter intake submitted to superovulation

This study investigated the influence of feed intake on superovulatory response and embryo production of Nelore heifers. Pubertal heifers were kept in a feedlot and were submitted to the same diets, but with different levels of feed consumption: High (1.7 M; n = 20) or Low (0.7 M; n = 19) feed intake. Heifers in the 1.7 M treatment consumed 170% (2.6% of body weight [BW] in dry matter) and the 0.7 M heifers ate 70% (1.1% of BW in dry matter) of a maintenance diet. After 7 wk on these diets, heifers were treated with eight decreasing doses of follicle-stimulating hormone (FSH) given every 12 h, totaling 133 mg Folltropin (Folltropin-V; Bioniche Animal Health, Canada) per heifer. Seven d after AI, heifers had their uteri flushed and embryos were recovered and graded according to the International Embryo Technology Society standards. Data were analyzed using the GLIMMIX procedure of SAS and results are presented as least-squares means ± SEM (P < 0.05). At the onset of the FSH treatment (Day 0 of the protocol), 1.7 M heifers had greater body condition score (BCS), BW and serum insulin concentrations than 0.7 M heifers (4.1 ± 0.1 vs. 3.0 ± 0.1; 462.5 ± 10.1 vs. 382.7 ± 10.4 kg; and 14.3 ± 1.7 vs. 3.5 ± 0.8 μIU/mL, respectively). The 0.7 M heifers had more follicles ≥6 mm at the time of the last FSH (Day 7; 47.9 ± 6.4 vs. 23.5 ± 4.3 follicles), related to a better follicle superstimulatory response to FSH. Similarly, 0.7 M heifers had more corpora lutea at the time of embryo collection (33.6 ± 1.4 vs. 15.7 ± 0.9) than the 1.7 M heifers, which resulted in greater number of recovered embryos and ova (9.9 ± 0.7 vs. 6.7 ± 0.6) and viable embryos (5.3 ± 0.5 vs. 3.8 ± 0.4), despite having similar proportions of viable embryos (∼62%). A negative correlation between circulating insulin and follicle superstimulatory response to FSH was observed (r = -0.68). Therefore, we conclude that high feed intake, for a long period of time, compromised the superovulatory response and embryo production potential of Bos indicus heifers possibly related to the elevation in circulating insulin.