Effects of anion supplementation to low-potassium prepartum diets on macromineral status and performance of periparturient dairy cows.

Data from multiparous Holstein cows (n = 43) were used to determine whether supplementation of anions to low-potassium (K) prepartum diets would improve periparturient energy and macromineral status and affect performance during the postpartum period. Beginning 21 d before expected parturition, cows were fed a control diet (1.29% K; +10 mEq/100 g; n = 21) or a low dietary cation-anion difference (DCAD) diet (1.29% K; -15 mEq/100 g; n = 22) with anions provided through a combination of sulfate from calcium sulfate dihydrate (0.40% S total ration) and chloride (1.17% Cl total ration) from SoyChlor 16-7 (West Central, Ralston, IA). All cows were fed the same postpartum diet from parturition through 63 d postpartum. Feeding anions decreased overall urine pH (8.17 vs. 6.70) during the prepartum period. Overall, peripartum concentrations of plasma Ca, P, and Mg were similar between treatments; however, concentrations of plasma Ca tended to be increased during the first 24 h postcalving in cows fed the low DCAD diet. Overall, concentrations of plasma P tended to be increased by feeding the anionic diet prepartum; this effect was more pronounced during the immediate peripartal period. Anionic supplementation did not affect incidence of clinical (<5 mg/dL) and subclinical (5 to 8 mg/dL) hypocalcemia, clinical hypophosphatemia (<2 mg/dL), or clinical (<1.1 mg/dL) and subclinical (1.1 to 1.8 mg/dL) hypomagnesemia. Nevertheless, subclinical hypophosphatemia (2 to 4 mg/dL) tended to be decreased at 16 h postcalving and was decreased at d 2 postpartum for cows fed the anionic diet prepartum. Anion supplementation decreased prepartum dry matter intake (15.6 vs. 14.4 kg/d), but did not affect postpartum dry matter intake (22.4 vs. 23.0 kg/d), milk yield (46.5 vs. 46.1 kg/d), or content and yield of milk fat and true protein. Plasma concentrations of energy-related metabolites (glucose, nonesterified fatty acids, beta-hydroxybutyrate) were similar for both groups during the prepartum and postpartum periods. Glucose rate of appearance was determined by continuous infusion of 6,6-dideuterated glucose in a subset of cows between 6 and 10 d prepartum (control, n = 12; low DCAD, n = 9) and 7 and 10 d postpartum (control, n = 9; low DCAD, n = 8) periods. Glucose rate of appearance was not affected by treatment during the prepartum or postpartum periods. Overall, anion supplementation of low K diets improved P status during the early postpartum period, but did not affect aspects of energy metabolism or periparturient performance.

Adipose tissue lipogenic gene networks due to lipid feeding and milk fat depression in lactating cows.

Dietary lipid supplements have been extensively evaluated for their effects on mammary tissue mRNA abundance, including the classical lipogenic genes ACACA, SCD, FASN, and the transcription regulators SREBF1, THRSP, and PPARG. Novel gene isoforms with key regulatory roles in triacylglycerol synthesis have been recently identified including LPIN1 and AGPAT6. Transcriptional networks (i.e., genes whose mRNA expression is regulated by a transcription factor or nuclear receptor) coordinate adipogenesis and lipid filling in nonruminant adipose tissue. To investigate whether long-term milk fat depression affects adipogenic networks in subcutaneous adipose tissue, we characterized mRNA expression via quantitative PCR of 20 genes in cows fed saturated and polyunsaturated lipid for 3 wk. Adipose tissue from cows fed a control diet, control with fish (10 g/kg of dry matter) and soybean oil (25 g/kg of dry matter) (FSO), or control with saturated lipid (35 g/kg, EB100; Energy Booster 100, Milk Specialties, Dundee, IL) was biopsied after 21 d of feeding. Milk production did not differ across treatments (averaged 32 kg +/- 2.8 kg/d during the 21 d) but dry matter intake (DMI) decreased in cows fed FSO versus controls (averaged 18 vs. 22 kg/d during the 21 d). Despite the decrease in DMI, FSO resulted in similar energy intake as EB100 during the last 2 wk of the study. Cows fed FSO had a gradual decline in milk fat and energy yield leading to an overall 25% decrease in milk fat yield during the study (averaged 0.90 vs. 1.2 kg/d) compared with control or EB100. Thus, during the 21-d study, FSO led to a gradual increase in intake energy available for adipose tissue deposition. Relative mRNA expression of LPL and SCD as well as ADFP (coding for a protein involved in lipid droplet formation) and LPIN1 (coding for a protein involved in diacylglycerol synthesis/transcriptional regulation) was upregulated with FSO relative to other diets. Expression of the transcription regulator THRSP tended to be greater in cows fed FSO. Overall, results suggest that long-term milk fat depression caused by feeding FSO provided additional energy as well as long-chain fatty acids that, coupled with upregulation of a subset of adipogenic genes in subcutaneous adipose tissue, might have resulted in greater tissue lipid deposition.

Long-chain fatty acid effects on peroxisome proliferator-activated receptor-alpha-regulated genes in Madin-Darby bovine kidney cells: optimization of culture conditions using palmitate.

Studying long-chain fatty acid (LCFA) effects on gene network expression in bovine cells could provide useful information for future practical applications. An optimized in vitro system that does not require tissue collection or cell isolation could fill a niche in the study of PPARalpha activity in ruminants. Specific aims were to optimize culture conditions in Madin-Darby bovine kidney (MDBK) cells to achieve maximal mRNA expression of known peroxisome proliferator-activated receptor-alpha (PPARalpha) target genes using palmitate (16:0) as a representative LCFA. Variables included length of incubation time, use of albumin-bound (4:1 molar proportion) 16:0 (A16:0), or addition of insulin. A first time-course experiment tested culturing cells in Dulbecco's modified Eagle's medium with 150 microM PPAR ligand Wy-14643 (WY) and A16:0. A second experiment tested the effects of albumin and insulin using 150 microM of 16:0 without albumin or insulin (-Alb/-Ins), 16:0 without albumin plus 5 mg/L of bovine insulin (-Alb/+Ins), A16:0 without insulin (+Alb/-Ins), or a control. A third experiment was a preliminary metabolic characterization of cells and assessed intracellular lipid droplet formation after treatment with 150 microM of 16:0 or an ethanol control. For all experiments, cells were harvested at 0, 6, 12, 18, and 24 h posttreatment. In experiments 1 and 2, mRNA expression was assessed by quantitative PCR of selected PPARalpha target genes as well as PPARalpha coactivators (ACOX1, CPT1A, ACADVL, ACSL1, PPARA, PPARGC1A, LPIN1). In experiment 1, there was a linear increase in mRNA expression of CPT1A (approximately 500%) and ACSL1 (50 to 200%) by 6 h of incubation with both WY and A16:0. The LPIN1 mRNA increased by >100% by 6 h only with A16:0. Further, there was a linear increase in expression of PPARA (approximately 100%) with A16:0 through 24 h of incubation. In experiment 2, insulin increased, and coupling LCFA with albumin tended to delay the response in expression of CPT1A and ACSL1 to 16:0. Data indicated a toxic effect of 150 microM free 16:0 as assessed by cell counts after 12 h of incubation. In experiment 3, MDBK cells appeared to use glucose and AA as energy sources and were able to secrete triglycerides. In addition, MDBK cells cultured with 150 microM of 16:0 had a substantial uptake of LCFA and synthesized intracellular lipid droplets. Overall, results indicated that a 6-h incubation with free LCFA and addition of insulin was suitable to detect marked effects on mRNA expression of PPARalpha target genes in MDBK cells.