Fibroblast growth factor-21 (FGF21) administration to early-lactating dairy cows. II. Pharmacokinetics, whole-animal performance, and lipid metabolism

Dairy cows cope with severe energy insufficiency in early lactation by engaging in intense and sustained mobilization of fatty acids from adipose tissue. An unwanted side effect of this adaptation is excessive lipid accumulation in the liver, which in turn impairs hepatic functions. Mice experiencing increased hepatic fatty acid flux are protected from this condition through coordinated actions of the newly described hormone fibroblast growth factor-21 (FGF21) on liver and adipose tissue. The possibility of an analogous role for FGF21 in dairy cows is suggested by its rapid increase in plasma levels around parturition followed by chronically elevated levels in the first few weeks of lactation. To test this hypothesis, dairy cows were randomly assigned on d 12.6 ± 2.2 (± standard error) of lactation to receive either an excipient (control; n = 6) or recombinant human FGF21 (n = 7), first as an FGF21 bolus of 3 mg/kg of body weight (BW) followed 2 d later by a constant i.v. infusion of FGF21 at a rate of 6.3 mg/kg of metabolic BW for 9 consecutive days. After bolus administration, human FGF21 circulated with a half-life of 194 min, and its constant infusion increased total plasma concentration 117-fold over levels in excipient-infused cows. The FGF21 treatment had no effect on voluntary feed intake, milk yield, milk energy output, or net energy balance measured over the 9-d infusion or on final BW. Plasma fatty acids circulated at lower concentrations in the FGF21 group than in the control group for the 8-h period following bolus administration, but this reduction was not significant during the period of constant i.v. infusion. Treatment with FGF21 caused a 50% reduction in triglyceride content in liver biopsies taken at the end of the constant i.v. infusion without altering the mRNA abundance of key genes involved in the transport, acyl coenzyme A activation, or oxidation of fatty acids. In contrast, FGF21 treatment ablated the recovery of plasma insulin-like growth factor-1 seen in control cows during the 9-d i.v. infusion period despite a tendency for higher plasma growth hormone. This effect was associated with increased hepatic mRNA abundance of the intracellular inhibitor of growth hormone receptor trafficking, LEPROT. Overall, these data confirm the ability of FGF21 to reduce lipid accumulation in bovine liver and suggest the possibility that FGF21 does so by attenuating the hepatic influx of adipose tissue-derived fatty acids.

Fibroblast growth factor-21 (FGF21) administration to early-lactating dairy cows. I. Effects on signaling and indices of insulin action

Modern dairy cows rely on hormonally driven mechanisms to coordinate the metabolic adaptations needed to meet the energy and nutrient deficits of early lactation. In the case of glucose, dairy cows cope with its scarcity during early lactation via reduced plasma concentrations of insulin and the insulin sensitizing hormone adiponectin and increased insulin resistance. Reduced insulin action promotes diversion of available glucose to the mammary gland but increases susceptibility to diseases if excessive. In earlier work, we reported that the insulin sensitizing hormone fibroblast growth factor-21 (FGF21) is increased in periparturient dairy cows and identified liver and adipose tissue as possible targets. These observations raised the possibility that FGF21 acts directly on these tissues to limit the insulin resistance of early lactation. To test this hypothesis, dairy cows were randomly assigned on d 12.6 ± 2.2 (± standard error) of lactation to receive either excipient (n = 6) or recombinant human FGF21 (n = 7), first as an FGF21 bolus of 3 mg/kg of body weight, followed 2 d later by a constant i.v. infusion of FGF21 at the rate of 6.3 mg/kg of metabolic body weight for 9 consecutive days. Biopsies of liver and adipose tissue were collected during the bolus phase of the experiment and used to analyze FGF21 signaling by Western blotting and expression of its receptor components by quantitative PCR. Bolus FGF21 administration caused a 4-fold increase in p44/42 MAPK (ERK1/2) activation in adipose tissue but had no effect on AKT and signal transducer and activator of transcription-3 (STAT3) signaling. The liver expressed negligible levels of the preferred FGF21 receptor FGFR1c and failed to mount any FGF21 signaling response. The FGF21 administered as a bolus had no effect on plasma glucose or insulin and did not stimulate an acute release of adiponectin from adipose tissue. Similarly, FGF21 infusion had no effect on plasma levels of glucose or insulin measured over the 9-d infusion or on glucose disposal during an i.v. glucose tolerance test performed on d 8 of infusion. Finally, the chronic FGF21 infusion had no effect on indices of adiponectin production, including plasma adiponectin and adipose tissue mRNA abundance of adiponectin and the endoplasmic reticulum chaperones ERO1A and DSBA-L involved in the assembly of adiponectin into multimeric complexes. These data show that human FGF21 does not act as an insulin sensitizer during the energy and glucose deficit of early lactation but do not rule out such a role in other physiological states.

Effects of heat stress and insulin sensitizers on pig adipose tissue

Heat stress (HS) negatively impacts several swine production variables, including carcass fat quality and quantity. Pigs reared in HS have more adipose tissue than energetically predicted, explainable, in part, by HS-induced hyperinsulinemia. Study objectives were to evaluate insulin's role in altering fat characteristics during HS via feeding insulin-sensitizing compounds. Forty crossbred barrows (113 ± 9 kg BW) were randomly assigned to one of five environment by diet treatments: 1) thermoneutral (TN) fed ad libitum (TNAL), 2) TN and pair-fed (TNPF), 3) HS fed ad libitum (HSAL), 4) HS fed ad libitum with sterculic oil (SO) supplementation (HSSO; 13 g/d), and 5) HS fed ad libitum with dietary chromium (Cr) supplementation (HSCr; 0.5 mg/d; Kemin Industries, Des Moines, IA). The study consisted of three experimental periods (P). During P0 (2 d), all pigs were exposed to TN conditions (23 ± 3 °C, 68 ± 10% RH) and fed ad libitum. During P1 (7 d), all pigs received their respective dietary supplements, were maintained in TN conditions, and fed ad libitum. During P2 (21 d), HSAL, HSSO, and HSCr pigs were fed ad libitum and exposed to cyclical HS conditions (28 to 33 °C, 58 ± 10% RH). The TNAL and TNPF pigs remained in TN conditions and were fed ad libitum or pair-fed to their HSAL counterparts. Rectal temperature (TR), respiration rate (RR), and skin temperature (TS) were obtained daily at 0600 and 1800 h. At 1800 h, HS exposed pigs had increased TR, RR, and TS relative to TNAL controls (1.13 °C, 48 bpm, and 3.51 °C, respectively; P < 0.01). During wk 2 and 3 of P2, HSSO pigs had increased 1800 h TR relative to HSAL and HSCr (~0.40 and ~0.42 °C, respectively; P ≤ 0.05). Heat stress decreased ADFI and ADG compared to TNAL pigs (2.24 vs. 3.28 and 0.63 vs. 1.09 kg/d, respectively; P < 0.01) and neither variable was affected by SO or Cr supplementation. Heat stress increased or tended to increase moisture content of abdominal (7.7 vs. 5.9%; P = 0.07) and inner s.c. (11.4 vs. 9.8%; P < 0.05) adipose depots compared to TNAL controls. Interestingly, TNPF pigs also had increased adipose tissue moisture content and this was most pronounced in the outer s.c. depot (15.0 vs. 12.2%; P < 0.01) compared to TNAL pigs. Heat stress had little or no effect on fatty acid composition of abdominal, inner, and outer s.c. adipose tissue depots. In summary, the negative effects of HS on fat quality do not appear to be fatty acid composition related, but may be explained by increased adipose tissue moisture content.

High-fat, high-fructose, high-cholesterol feeding causes severe NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine

Pediatric obesity and nonalcoholic steatohepatitis (NASH) are on the rise in industrialized countries, yet our ability to mechanistically examine this relationship is limited by the lack of a suitable higher animal models. Here, we examined the effects of high-fat, high-fructose corn syrup, high-cholesterol Western-style diet (WD)-induced obesity on NASH and cecal microbiota dysbiosis in juvenile Ossabaw swine. Juvenile female Ossabaw swine (5 wk old) were fed WD (43.0% fat; 17.8% high-fructose corn syrup; 2% cholesterol) or low-fat diet (CON/lean; 10.5% fat) for 16 wk ( n = 6 each) or 36 wk ( n = 4 each). WD-fed pigs developed obesity, dyslipidemia, and systemic insulin resistance compared with CON pigs. In addition, obese WD-fed pigs developed severe NASH, with hepatic steatosis, hepatocyte ballooning, inflammatory cell infiltration, and fibrosis after 16 wk, with further exacerbation of histological inflammation and fibrosis after 36 wk of WD feeding. WD feeding also resulted in robust cecal microbiota changes including increased relative abundances of families and genera in Proteobacteria ( P < 0.05) (i.e., Enterobacteriaceae, Succinivibrionaceae, and Succinivibrio) and LPS-containing Desulfovibrionaceae and Desulfovibrio and a greater ( P < 0.05) predicted microbial metabolic function for LPS biosynthesis, LPS biosynthesis proteins, and peptidoglycan synthesis compared with CON-fed pigs. Overall, juvenile Ossabaw swine fed a high-fat, high-fructose, high-cholesterol diet develop obesity and severe microbiota dysbiosis with a proinflammatory signature and a NASH phenotype directly relevant to the pediatric/adolescent and young adult population.

Fibroblast growth factor 21 analogue LY2405319 lowers blood glucose in streptozotocin-induced insulin-deficient diabetic mice by restoring brown adipose tissue function

AIM

To investigate the effects of LY2405319, an analogue of fibroblast growth factor 21 (FGF21), on glucose homeostasis in streptozotocin (STZ)-induced insulin-deficient mice (STZ mice).

METHODS

Nine-week-old male C57BL/6J mice were administered a single intraperitoneal injection of STZ (150 mg/kg). One week later, after confirmation of hyperglycaemia, saline or LY2405319 (5 mg/kg) was injected subcutaneously daily for 4 weeks. Changes in glucose homeostasis, energy metabolism and brown adipose tissue (BAT) function were assessed.

RESULTS

The STZ mice had elevated blood glucose and reduced plasma FGF21 levels, impaired glucose uptake in the BAT, and BAT mitochondria with absent or swollen cristae and fewer lipid vacuoles. LY2405319 significantly reduced blood glucose levels and this was associated with increased BAT glucose uptake and changes in gene expression and morphology, indicating improved mitochondrial lipid metabolism in the BAT. Importantly, the ability of LY2405319 to lower blood glucose in STZ mice was compromised after removing interscapular BAT.

CONCLUSIONS

Our results show that LY2405319 reduces blood glucose levels in insulin-deficient diabetes by improving BAT metabolism. Additional studies investigating the therapeutic potential of FGF21 for the treatment of type 1 diabetes are warranted.

Diet-induced obesity alters immune cell infiltration and expression of inflammatory cytokine genes in mouse ovarian and peri-ovarian adipose depot tissues

Dysregulation of immune cells and/or altered inflammatory signaling have been implicated with reproductive dysfunction. Physiological changes leading to perturbations in the profile of immune cells and/or pro-inflammatory cytokines in or around female reproductive tissue could potentially have profound effects on ovarian function. Obesity is associated with chronic low-grade inflammation due, in part, to increased immune cell infiltration and inflammation in visceral adipose depots. This study investigated the impact of diet-induced obesity on immune cell infiltration and inflammation in peri-ovarian adipose tissue and mRNA expression of key inflammatory markers and microRNAs (miRs) in ovarian tissue. Six-week-old female C57Bl/6J mice were fed a standard chow or high-fat diet (HFD; 60% kcal fat) for approximately 7 months, at which time peri-ovarian adipose tissue and ovarian tissues were collected. Histological analysis of peri-ovarian adipose tissue from obese mice revealed increased (P < 0.05) adipocyte size and the presence of crown-like structures, the morphological presentation of infiltrating immune cells in adipose tissue, along with increases (P < 0.05) in the mRNA levels of markers of T-cells, activated macrophages, inflammatory cytokines, and chemokines. Ovarian mRNA levels of Il1b, Il6, Tnfa, p55, p75, Ccl2, Ikbkb, and Rela were higher in obese tissue (P < 0.05), with a strong trend (P = 0.06) for an increase in Nos2 and RELA protein. Additionally, ovarian miR125b and miR143 levels were decreased (P = 0.1). These data demonstrate that diet-induced obesity elevates expression of inflammatory-mediator genes in both the ovary and surrounding adipose depot, potentially negatively affecting ovarian function.

High fat diet induced obesity alters ovarian phosphatidylinositol-3 kinase signaling gene expression

Insulin regulates ovarian phosphatidylinositol-3-kinase (PI3 K) signaling, important for primordial follicle viability and growth activation. This study investigated diet-induced obesity impacts on: (1) insulin receptor (Insr) and insulin receptor substrate 1 (Irs1); (2) PI3K components (Kit ligand (Kitlg), kit (c-Kit), protein kinase B alpha (Akt1) and forkhead transcription factor subfamily 3 (Foxo3a)); (3) xenobiotic biotransformation (microsomal epoxide hydrolase (Ephx1), Cytochrome P450 isoform 2E1 (Cyp2e1), Glutathione S-transferase (Gst) isoforms mu (Gstm) and pi (Gstp)) and (4) microRNA's 184, 205, 103 and 21 gene expression. INSR, GSTM and GSTP protein levels were also measured. Obese mouse ovaries had decreased Irs1, Foxo3a, Cyp2e1, MiR-103, and MiR-21 but increased Kitlg, Akt1, and miR-184 levels relative to lean littermates. These results support that diet-induced obesity potentially impairs ovarian function through aberrant gene expression.

Sterculic oil, a natural inhibitor of SCD1, improves the metabolic state of obese OLETF rats

OBJECTIVE

Abnormal lipid metabolism and excess accumulation of lipid in non-adipose tissues are defining characteristics of obesity and its comorbidities. Expression and/or activity of stearoyl-CoA desaturase-1 (SCD1), a major regulator of lipid metabolism, is increased with obesity and the reduction/ablation of this enzyme is associated with an improved metabolic profile. Sterculic oil (SO), obtained from the seeds of the Sterculia feotida tree, contains a high concentration of cyclopropenoic fatty acids which are known inhibitors of SCD1. The purpose of this study was to determine the effects of SO supplementation on the development of obesity and insulin resistance in hyperphagic, obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

DESIGN & METHODS

Rats received either an AIN-93G diet (control) or an AIN-93G diet containing 0.5% SO for 10 weeks.

RESULTS

SO did not alter body weight or body composition. Importantly, the desaturase indices, a proxy for the activity of SCD1, were reduced in the liver and adipose tissue of SO supplemented animals. This reduction in SCD1 activity was associated with a reduction in fasting blood glucose concentrations and improved glucose tolerance. In addition, SO reduced intra-abdominal fat mass and adipocyte size and resulted in a ∼3-fold increase in GLUT1 gene expression in intra-abdominal fat. Liver triglyceride content and lipogenic gene expression were reduced by SO. Consistent with an improved metabolic phenotype, SO also improved plasma cholesterol, LDL-cholesterol, and triglyceride concentrations.

CONCLUSION

Overall, our data demonstrate an improved metabolic phenotype with SO supplementation and suggest further studies are required to better understand the therapeutic potential of SO.

Trans-9, Cis-11 Conjugated Linoleic Acid Reduces Milk Fat Synthesis in Lactating Dairy Cows

Under certain dietary situations, rumen biohydrogenation results in the production of unique fatty acids that inhibit milk fat synthesis. The first of these to be identified was trans-10, cis-12 conjugated linoleic acid (CLA), but others are postulated to contribute to diet-induced milk fat depression (MFD). Our objective was to examine the potential role of trans-9, cis-11 CLA in the regulation of milk fat. In a preliminary study, we used gas-liquid and high-performance liquid chromatography techniques to examine milk fat samples from a diet-induced MFD study and found that an increase in trans-9, cis-11 CLA corresponded to the decrease in milk fat yield. We investigated this further using a CLA enrichment of 9, 11 isomers to examine the biological effect of trans-9, cis-11 CLA on milk fat synthesis. Four rumen-fistulated Holstein cows were randomly assigned in a 4 x 4 Latin square experiment involving 5-d treatment periods and abomasal infusion of 1) ethanol (control), 2) a 9, 11 CLA mix (containing 32% trans-9, cis-11, 29% cis-9, trans-11, and 17% trans-9, trans-11), 3) a trans-9, trans-11 CLA supplement, and 4) a trans-10, cis-12 CLA supplement (positive control). The trans-9, trans-11 CLA and trans-10, cis-12 CLA supplements were of high purity (>90%), and all supplements were infused at a rate to provide 5 g/d of the CLA isomer of interest. Milk yield and dry matter intake did not differ among treatments. Compared with the control treatment, milk fat yield was reduced by 15% for the 9, 11 CLA mixture and by 27% for the trans-10, cis-12 CLA treatment. We also found that trans-9, trans-11 CLA had no effect on milk fat yield, and previous research has shown that milk fat yield is unaltered when cows are infused with cis-9, trans-11 CLA. When all treatments were considered, results suggested that trans-9, cis-11 was the CLA isomer in the 9, 11 CLA mix responsible for the reduction in milk fat synthesis, although the magnitude was less than that observed for trans-10, cis-12 CLA. Interestingly, trans-9, trans-11 CLA altered the milk fat desaturase index, further demonstrating that alterations in desaturase can occur independently of effects on milk fat synthesis. Overall, our investigations identified that an increase in milk fat content of trans-9, cis-11 CLA was associated with diet-induced MFD and provided evidence of a role for this isomer in MFD based on the 15% reduction in milk fat yield with abomasal infusion of a CLA enrichment that supplied 5 g/d of trans-9, cis-11 CLA.

Trans-10, Trans-12 Conjugated Linoleic Acid Does Not Affect Milk Fat Yield but Reduces Δ9-Desaturase Index in Dairy Cows

Trans-10, cis-12 conjugated linoleic acid (CLA) is a potent inhibitor of milk fat synthesis, and the magnitude of milk fat depression is often correlated with the fat content of this isomer. However, the trans-10, cis-12 CLA content does not always correspond to the extent of milk fat depression, and in some instances, an increase in the milk fat content of trans-10, trans-12 CLA has been observed. We synthesized trans-10, trans-12 CLA (>90% purity) and investigated its effect on milk fat synthesis and incorporation into plasma lipids. Three rumen-fistulated Holstein cows were randomly assigned in a 3 x 3 Latin square experiment. Treatments were a 4-d abomasal infusion of 1) ethanol (control), 2) a trans-10, cis-12 CLA supplement (positive control), and 3) a trans-10, trans-12 CLA supplement; 5 g/d of the CLA isomer of interest was provided. Milk yield, dry matter intake, and milk protein were unaffected by treatment. Treatment with trans-10, trans-12 CLA had no effect on milk fat yield, whereas treatment with trans-10, cis-12 CLA reduced milk fat yield by 28%. Incorporation of CLA was greatest for the plasma triglyceride fraction, and the milk fat content was subsequently elevated within the respective treatment groups. The milk fatty acid composition indicated that delta9-desaturase was reduced significantly for both CLA treatments, but the reduction was greater for the treatment with trans-10, trans-12 CLA. Overall, abomasal infusion of trans-10, trans-12 CLA and trans-10, cis-12 CLA altered the desaturase ratios, but only trans-10, cis-12 CLA reduced milk fat synthesis.

A Conjugated Linoleic Acid Supplement Containing trans-10, cis-12 Reduces Milk Fat Synthesis in Lactating Sheep

The efficacy of conjugated linoleic acid (CLA) supplements containing trans-10, cis-12 for reducing milk fat synthesis has been well documented in dairy cows, but studies with other ruminant species are less convincing, and there have been no investigations of this in sheep. Therefore, the current study was designed to determine whether trans-10, cis-12 CLA would inhibit milk fat synthesis in sheep. Twenty multiparous ewes in early lactation were paired and randomly allocated to 2 treatments: grass hay plus concentrate either unsupplemented (control) or supplemented with lipid-encapsulated CLA to provide 2.4 g/d of trans-10, cis-12 CLA. The CLA dose was based on published responses of dairy cows extrapolated to ewes on a metabolic body weight basis. The experimental design was a 2-period crossover with 10-d treatment periods separated by a 10-d interval. Compared with the control, CLA supplementation reduced milk fat content from 6.4 to 4.9% and reduced fat yield from 95 to 80 g/d. The CLA treatment also increased milk yield from 1,471 to 1,611 g/d and increased protein yield from 68 to 73 g/d. Milk protein content and DMI were unaffected by treatment. The reduction in milk fat yield was due to decreases in both de novo fatty acid synthesis and uptake of preformed fatty acids. Milk fat content of trans-10, cis-12 CLA was < 0.01 and 0.12 g/100 g of fatty acids for the control and CLA treatments, respectively. The transfer efficiency of trans-10, cis-12 CLA from the dietary supplement into milk fat was 3.8%. Results of the present study demonstrate that a CLA supplement containing trans-10, cis-12 CLA reduces milk fat synthesis in lactating sheep in a manner similar to dairy cows when fed at an equivalent dose (metabolic body weight basis). Furthermore, the nutrients spared by the reduction in milk fat coincided with an increase in milk and milk protein yield.

Milk fat synthesis is unaffected by abomasal infusion of the conjugated diene 18∶3 isomers cis-6, trans-10, cis-12 and cis-6, trans-8, cis-12

It has been previously established that trans-10,cis-12 CLA is a potent inhibitor of milk fat synthesis. Although the mechanism of this action is not completely understood, it has been speculated that eicosanoid-like metabolites of this isomer formed by the activity of tissue desaturases may be responsible for its activity. The objective of this study was to investigate the effects of an enrichment containing an 18:3 conjugated diene, produced in the metabolism of trans-10,cis-12 CLA, on milk fat synthesis. Three rumen-fistulated Holstein cows (210+/-8 d in milk) were randomly assigned in a 3 x 3 Latin square experiment. Treatments were (i) control, (ii) trans-10,cis-12 CLA supplement (2.1 g/d; positive control), (iii) enrichment providing two conjugated diene 18:3 isomers (2.6 g/d of cis-6,trans-10,cis-12 and 4.0 g/d of cis-6,trans-8,cis-12) and trans-10,cis-12 CLA (2.1 g/d). Treatments were abomasally infused for 5 d at 4-h intervals, and there was a 7-d interval between periods. Milk yield, dry matter intake, and milk protein yield were unaffected by treatments. In contrast, the trans-10,cis-12 CLA supplement reduced milk fat yield by 27%, whereas the supplement enriched with conjugated diene 18:3 isomers (treatment iii) had no effect on milk fat yield beyond that attributable to its trans-10,cis-12 CLA content. The transfer efficiency of trans-10,cis-12 CLA into milk fat was 25 and 24% for treatments ii and iii, respectively. At the same time, the abomasally infused conjugated diene 18:3 isomers were transferred to milk fat with an efficiency of 33 and 41% for cis-6,trans-10,cis-12 and cis-6,trans-8,cis-12 18:3, respectively. Overall, short-term abomasal infusion of the conjugated diene 18:3 isomers had no effect on milk fat synthesis, thereby offering no support for an involvement of metabolites of trans-10,cis-12 CLA in the regulation of milk fat synthesis.

Effects of Amide-Protected and Lipid-Encapsulated Conjugated Linoleic Acid (CLA) Supplements on Milk Fat Synthesis

The trans-10, cis-12 isomer of conjugated linoleic acid (CLA) is a potent inhibitor of milk fat synthesis; its ability to reduce milk fat output in a controlled manner as a feed supplement, has potential management applications in the dairy industry. The effectiveness of dietary supplements of trans-10, cis-12 CLA is related to the extent to which their metabolism by rumen bacteria is minimized. A number of processes have been used to manufacture "rumen-protected" feed supplements, and their efficacy can be described by the extent of protection from rumen bacteria as well as postruminal bioavailability. The objective of this study was to investigate the effects of 2 rumen-protected CLA supplements on milk fat synthesis. Using the same initial batch of CLA, supplements were manufactured by the formation of fatty acyl amide bonds or by lipid encapsulation. Three rumen fistulated Holstein cows were randomly assigned in a 3 x 3 Latin square experiment. Treatments were 1) no supplement (control), 2) amide-protected CLA supplement, and 3) lipid-encapsulated CLA supplement. Supplements were fed to provide 10 g/d of the trans-10, cis-12 CLA isomer. Over the 7-d treatment period, 21 and 22% reductions in milk fat yield were observed for the amide-protected and lipid-encapsulated supplements, respectively. Transfer of trans-10, cis-12 CLA into milk fat was also similar for the amide-protected (7.1%) and lipid-encapsulated (7.9%) supplements. Overall, the amide-protected and lipid-encapsulated CLA supplements were equally effective at reducing milk fat synthesis and had no effect on milk yield or dry matter intake.

Use of Conjugated Linoleic Acid (CLA) Enrichments to Examine the Effects of trans-8, cis-10 CLA, and cis-11, trans-13 CLA on Milk-Fat Synthesis

Conjugated linoleic acid (CLA) supplements have typically been comprised of 4 isomers (trans-8, cis-10; cis-9, trans-11; trans-10, cis-12; and cis-11, trans-13 CLA). Abomasal infusion of pure isomers has shown that trans-10, cis-12 CLA is a potent inhibitor of milk-fat synthesis, whereas cis-9, trans-11 CLA has no effect. However, there appear to be additional fatty acids that inhibit milk-fat synthesis, and the objective of this study was to investigate the effects of additional CLA isomers present in CLA supplements. Four rumen fistulated Holstein cows (141+/-8 DIM, mean+/-SE) were randomly assigned in a 4 x 4 Latin square experiment. Treatments were abomasal infusion of (1) skim milk (negative control), (2) trans-10, cis-12 CLA supplement (positive control), (3) trans-8, cis-10 CLA supplement, and (4) cis-11, trans-13 CLA supplement. Treatments 2 through 4 were targeted to provide 4 g/d of the CLA isomer of interest. The trans-8, cis-10 CLA supplement had no effect on milk-fat yield, whereas the trans-10, cis-12 CLA supplement reduced milk-fat yield by 35%. The cis-11, trans-13 CLA supplement contained some trans-10, cis-12 CLA, and when data were compared to the positive control treatment group, it was obvious that cis-11, trans-13 CLA also had no effect on milk-fat synthesis. Milk-fat content of specific CLA isomers was significantly elevated within respective treatment groups. Milk yield, DMI, and milk protein yield were unaffected by treatment. Overall, trans-10, cis-12 CLA reduced milk-fat synthesis, whereas the other major isomers present in CLA supplements (trans-8, cis-10 CLA and cis-11, trans-13 CLA) had no effect.

Production responses of dairy cows to dietary supplementation with conjugated linoleic acid (CLA) during the transition period and early lactation

Holstein cows (n = 30) entering second or greater lactation were fed fat supplements (90 g/d of fatty acids) consisting of Ca salts of either palm fatty acid distillate (control) or a mixture of palm fatty acid distillate and mixed isomers of conjugated linoleic acid (CLA, 30.4 g/ d) from 2 wk prepartum through 20 wk postpartum to determine whether CLA would inhibit milk fat synthesis during early lactation and, in turn, affect energy metabolism of dairy cows during the transition period and early lactation. Feeding CLA did not affect DMI or plasma concentrations of glucose, nonesterfied fatty acids, or beta-hydroxbutyrate during the prepartum period and did not affect postpartum DMI. Feeding CLA reduced milk fat content by 12.5% during early lactation; however, cows fed CLA tended to produce approximately 3 kg/d more milk during the first 20 wk of lactation. Feeding CLA tended to decrease the contribution of short- and medium-chain (C < or = 16) fatty acids to milk fat. Changes in milk yield, milk fat content, and milk fatty acid composition were not apparent until after the second week of lactation. Yield of 3.5% fat-corrected milk, milk protein content, milk protein composition, and calculated energy balance were not affected by treatment. Postpartum concentrations of glucose, nonesterfied fatty acids, and beta-hydroxbutyrate in plasma and hepatic content of glycogen and triglycerides were similar between treatments. These data imply that with CLA treatment in early lactation, dairy cows decreased milk fat synthesis and appeared to respond by partitioning more nutrients toward milk synthesis rather than improving net energy balance.

Effects of dietary supplementation of rumen-protected conjugated linoleic acid in dairy cows during established lactation

Short-term studies (< 5 d) involving abomasal infusion of a mixture of CLA isomers or pure trans-10, cis-12 CLA have demonstrated that supplements of conjugated linoleic acids (CLA) reduce milk fat synthesis during established lactation in dairy cows. Our objective was to assess longer term effects of supplementation during established lactation using a dietary supplement of rumen-protected CLA. Thirty Holstein cows were blocked by parity and received a dietary fat supplement of either Ca-salts of palm oil fatty acids (control) or a mixture of Ca-salts of palm oil fatty acids plus Ca-salts of CLA (CLA treatment). Supplements provided about 90 g/d of fatty acids and were topdressed on the TMR. The CLA supplement provided 30.4 g/d of CLA in which the predominant isomers were: trans-8, cis-10 (9.2%), cis-9, trans-11 (25.1%), trans-10, cis-12 (28.9%), and cis-11, trans-13 (16.1%). All cows were pregnant; treatments were initiated on d 79 of pregnancy (approximately 200 d prepartum) and continued for 140 d until dry off. Twenty-three cows completed the study; those receiving CLA supplement had a lower milk fat test (2.90 versus 3.80%) and a 23% reduction in milk fat yield (927 versus 1201 g/d). Intake of DM, milk yield, and the yield and content of true protein and lactose in milk were unaffected by treatment. Milk fat analysis indicated that the CLA supplement reduced the secretion of fatty acids of all chain lengths. However, effects were proportionally greater on short and medium chain fatty acids, thereby causing a shift in the milk fatty acid composition to a greater content of longer-chain fatty acids. Changes in body weight gain, body condition score, and net energy balance were not significant and imply no differences in cows fed the CLA supplement in replenishment of body reserves in late lactation. Likewise, maintenance of pregnancy, gestation length, and calf birth weight were unaffected by treatment. Overall, feeding a dietary supplement of rumen-protected CLA to pregnant cows over the last 140 d of the lactation cycle resulted in a marked reduction in milk fat content and yield, and a shift in milk fatty acid composition, but other milk components, DMI, maintenance of pregnancy, and cow well-being were unaffected.