Ruminant Nutrition I: Fat

Transcription

1 Ruminant Nutrition I: Fat 105 Saturated fat supplemented in the form of triglycerides decreased digestibility and reduced performance of dairy cows as compared to calcium salt of fatty acids. A. Oyebade* 1,2, L. Lifshitz 1, H. Lehrer 1, S. Jacoby 1, Y. Portnick 1, and U. Moallem 1, 1 Department of Ruminant Science, ARO, Volcani Center, Rishon LeZion, Israel, 2 Department of Animal Science, University of Jerusalem, Rehovot, Israel. Several forms of protected fats are common in dairy cow rations. The objectives of this study were to determine the effects of supplementation of saturated fatty acid (SFA; 70 80% C16 and 5 10% C18) in the form of triglycerides (TG), as compared with calcium salt of free fatty acids (CSFA; contained 44% C16, 40% C18:1 and 9.5% C18:2), on milk and milk solids yields, efficiency and digestibility. Twenty-eight multiparous cows were fed a basal diet supplemented either with (on DM basis): (i) SFA - 1.2% SFA (~350 g/cow/d), or (ii) CSFA - 1.4% CSFA (~440 g/cow/d). The supplements were balanced according to fat content (SFA 99% fat vs. CSFA 84% fat). Data were analyzed using the PROC MIXED model of SAS. Milk yield of the SFA cows was 3% lower (46.2 vs kg/d; P < 0.001), and fat corrected milk (4%) was 4.5% lower than in CSFA cows. No difference in milk-fat content was observed, but milk-protein content was higher in the SFA cows. No differences in DMI or efficiency calculations between groups were observed. The ruminal ph and ammonia concentrations were similar between groups, while acetate concentrations and acetate:propionate ratio were greater for the CSFA cows. The apparent total track digestibility of all dietary components was lower in the SFA than CSFA cows: DM % and 62.0% (P < 0.001); fat % and 70.5% (P < 0.001); NDF % and 47.8% (P < 0.02), respectively. SFA did not depress milk protein, which would seem an important advantage of the SFA over CSFA. Because supplements in the diet were balanced for their fat content, the lower yields observed in the SFA cows could be due to probable overestimation of the energy value of the SFA supplement>, which resulted in lower inclusion level of fat (and energy) in the SFA than CSFA diet. The lower digestibility of all dietary components as observed for the SFA, is probably due to the effects of the degree of saturation and the form of the SFA (highly saturated TG). This leads to the conclusion that although the SFA supplement in the form of TG contains 99% fat comparing to 84% in the CSFA, the net energy for lactation value for SFA might be similar or lower than that of CSFA, mainly because of lower digestibility. Key Words: calcium salt of free fatty acids (CSFA), saturated fat 106 Effect of supplementation of pasture-based diet on ω-3 and ω-6 fatty acid profile of sheep milk. A. Cabiddu*, A. Margherita, M. Decandia, and G. Molle, Agris, Loc. Bonassai, Olmedo, Sassari Italy. The aim of this study was to evaluate the effect of supplements on ω-3 and ω-6 (omega-3 and omega-6) fatty acid profile of grazing ewes. Fortyeight dairy sheep (DIM , BCS , BW kg, and milk yield ml) were randomly assigned to the following dietary groups: only pasture (PAS), nonfat enriched supplementation (NFS, sheep, supplemented with 900 g of cereal based concentrate with 3.01% EE DM basis), moderate linolenic acid (ALA) supplementation (C183M, sheep supplemented with 900 g of linseed based concentrate with 6.01% EE DM basis) and high ALA supplementation (C183H, supplemented with 900 g of linseed based concentrate with 10.35% EE DM basis). All sheep grazed an Italian ryegrass paddock with an allocation of 22 h/d (PAS) or 3 h/d (all supplemented groups). Fatty acid methyl esters from milk fat were measured on one occasion using base-catalyzed methanolysis. ANCOVA model with orthogonal contrast was used to test the effect of dietary treatment (Treat). Contrasts were performed to test the effect of supplementation level (SUPP), FAT enrichment and ALA level in the fat enriched concentrate (ALAL) on ω-3 and ω-6 milk FA profile. Overall treatment affected total ω-3, EPA, DHA, and total ω-6 content (P < 0.05). Pasture supplementation affected (P < 0.05) total ω-3 and LNA content without effects on EPA and DHA Table 1 (Abstr. 106). Adjusted least squares means of ω-3 and ω-6 fatty acids Treatment Contrast Fatty acid PAS NFS C183M C183H Treat Supp Fat ALAL Tot ω-3 (mg/g fat) * * * NS C18:3c9c12c15 (% ω-3) NS NS NS NS C18:2t11c15 (% ω-3) NS NS NS NS DPA (% ω-3) * NS * NS C18:2c9c15 (% ω-3) NS NS NS NS EPA (% ω-3) * NS * NS DHA (% ω-3) * NS NS * Tot ω6 (mg/g fat) * NS * NS C18:2c9c12 (% ω-6) * * * NS C18:2c9t12t8c12 (% ω-6) NS NS * NS CLA t10c12 (% ω-6) * NS * NS C20:3c8c11c14 (% ω-6) * NS * NS C18:2t9c12 (% ω-6) * * NS * C20:4 c5c8c11c14 (% ω-6) NS NS NS NS C18:2t9t12 (% ω-6) * NS NS * *P 0.05; NS = P >

2 (Table 1). The ω-3 FA profile was mainly represented by ALA whereas in ω-6 the main components were LNA and C18:2c9t12t8c12. Key Words: dairy sheep, grazing, milk 107 Milk production responses to altering the dietary ratio of palmitic and oleic acids varies with production level in dairy cattle. M. M. Western*, J. de Souza, and A. L. Lock, Michigan State University, East Lansing, MI. We evaluated the effects of altering the dietary ratio of palmitic (C16:0) and oleic (cis-9 C18:1) acids on production responses of cows with a wide range of milk production (32 to 65 kg/d) in a crossover design experiment with a covariate period. Thirty-two multiparous Holstein cows (144 ± 94 DIM) were assigned randomly within level of milk yield to treatment sequence. Treatments were diets supplemented with FA blends (1.5% of diet DM) that provided 80% C16:0 + 10% C18:1 (PA) and 60% C16:0 + 30% C18:1 (PA+OA). The corn silage and alfalfabased diets contained 20.0% forage NDF, 28.5% starch and 17.1% CP. Treatment periods were 21 d with the final 5 d used for data and sample collection. The statistical model included the random effect of cow, the fixed effect of treatment, period, preliminary milk yield (PMY), and 2-way interactions. Linear effects for the interaction between PMY and treatments were added to evaluate responses to treatment by level of milk yield. There were no effects of treatments on DMI (P = 0.34), milk yield (P = 0.38), ECM (P = 0.35), BW (P = 0.74), or BW change (P = 0.54). Compared with PA+OA, PA increased fat yield (1.92 vs kg/d, P < 0.01) and protein yield (1.61 vs kg/d, P = 0.03). PA also increased the yield of de novo (448 vs. 428 g/d, P < 0.05) and mixed (749 vs. 669 g/d, P < 0.01) milk FA and decreased the yield of preformed FA (605 vs. 627 g/d, P < 0.05) compared with PA+OA. Interactions were detected between treatment and PMY for DMI and ECM (linear interaction both P < 0.05), and a tendency for milk yield (linear interaction P = 0.12); lower-producing cows (less than 45 kg/d) had increased DMI and ECM on the PA diet whereas higher-producing cows (over 55 kg/d) had increased DMI and ECM on PA+OA. A linear interaction was also detected between treatment and PMY for mixed milk FA yield (linear interaction both P < 0.10) and a tendency for de novo milk FA yield (linear interaction P < 0.15). Our results demonstrate that production responses (DMI, milk yield, and ECM) of high-producing cows was better with a fat supplement containing more C18:1, while lower-producing cows responded better to a supplement containing more C16:0. Key Words: production level, palmitic acid, oleic acid 108 Effects of altering the ratio of stearic and oleic acids in supplemental fat blends on fatty acid digestibility and production responses of dairy cows. C. M. Prom* and A. L. Lock, Michigan State University, East Lansing, MI. The objective of our study was to determine the effects of altering the ratio of stearic (SA) and oleic (OA) acids in supplement fat blends on fatty acid (FA) digestibility and production responses of dairy cows. Eight multiparous Holstein cows (157 DIM ± 33) were randomly assigned to treatment sequence in a replicated 4 4 Latin square design with 14-d periods. The treatments were a non-fa supplemented control diet (CON), and 3 diets incorporating 1.5% DM FA supplement blends containing 50% SA and 10% OA (50:10), 40% SA and 20% OA (40:20), or 30% SA and 30% OA (30:30). FA blends were balanced to contain ~30% palmitic, 5% linoleic, and < 0.5% linolenic acids. FA supplements replaced soyhulls in the CON diet. The statistical model contained the random effect of cow within square and the fixed effects of period, treatment, and their interaction. Pre-planned contrasts included CON vs. fat supplementation and the linear and quadratic effects of increasing OA. Results in the text are presented in the following order: CON, 50:10, 40:20, and 30:30. There was no effect of treatment on DMI (P = 0.91). Compared with CON, FA treatments increased milk yield (43.0, 44.7, 45.7, 45.2 kg/d; P < 0.01), ECM (43.4, 45.5, 45.8, 44.9 kg/d; P = 0.02), and fat yield (1.49, 1.58, 1.58, 1.55 kg/d; P = 0.01) and tended to increase milk protein yield (P = 0.10). Compared with CON, FA treatments had no effect on the yield of de novo milk FA (P = 0.35), decreased mixed milk FA (P = 0.04), and increased preformed milk FA (P < 0.01). The increase in preformed FA yield was predominantly due to FA treatments increasing the yield of OA in milk (218, 250, 264, 264 g/d; P < 0.01) compared with CON. Increasing OA did not affect milk yield (P = 0.63), milk fat yield (P = 0.33), or milk protein yield (P = 0.61). Increasing OA in FA treatments linearly decreased the yield of de novo (416, 420, 411, 391 g/d; P = 0.03) and mixed (534, 573, 560, 544; P = 0.05) milk FA, but did not affect the yield of preformed FA (440, 493, 510, 514; P = 0.12). In summary, feeding FA supplements containing SA and OA increased milk yield, ECM, fat yield, and preformed FA in milk compared with a no added fat control diet. Key Words: fat supplementation, oleic acid, stearic acid 109 Effect of dietary supplementation of acetate on milk fat synthesis in lactating dairy cows. N. L. Urrutia* 1,2, R. Bomberger 1, and K. J. Harvatine 1, 1 The Pennsylvania State University, University Park, PA, 2 Instituto de Investigaciones Agropecuarias, Osorno, Region de Los Lagos, Chile. Acetate is a major source of energy and substrate for milk fat synthesis in the dairy cow. We recently reported a linear increase in milk fat synthesis and greater than a 30% net transfer of acetate to milk fat with ruminal infusion of neutralized acetate. The objective of the current study was to investigate the ability of acetate mixed in a TMR to increase milk fat synthesis. Additionally, infusion of acetate results in an increase in plasma β-hydroxybutyrate so the effect of butyrate on milk fat was also investigated. Twelve multiparous lactating Holstein cows were randomly assigned to treatments in a 3 3 Latin square design with 14 d periods including 7 d of treatment and 7 d washout. Cows were fed ad libitum with a low risk diet for milk fat depression (33% NDF, 24% starch, 4.5% ether extract, 17.3% CP) and treatments were mixed into the basal diet. Treatments were on a dry matter basis: 3.1% NaHCO3 (control), 2.7% sodium acetate, and 2.4% calcium butyrate (carbon equivalent to acetate treatment). Data were analyzed by repeated measures and the model included the random effect of cow, period and sequence and the fixed effect of a covariate (d 0 of each period), treatment, time, and their interaction. Treatments were compared using a protected LSD. Feeding sodium acetate increased DMI by 2.7 kg (P < 0.05), had no effect on milk yield, and increased milk fat yield by 4.7% (P < 0.05) and concentration by 4.4% (P < 0.05) compared with control. Calcium butyrate decreased DMI by 2.3 kg, milk yield by 5%, milk fat yield by 8.8% and milk protein yield by 8.7% and concentration by 2.2%, compared with control (all P < 0.05). Sodium acetate increased concentration of 16 carbon mixed source fatty acids (FA) and myristic and palmitic acid (P < 0.05), while decreasing preformed FA, compared with control. Calcium butyrate had no effect on concentration of milk FA by source, but increased concentration of trans-10 C18:1 in milk by 18% (P < 0.05), indicating a shift in rumen biohydrogenation pathways. Our data demonstrates that milk fat yield can be increased 158

3 by feeding sodium acetate and that butyrate does not increase milk fat at equivalent levels. Key Words: acetate, butyrate, milk fat synthesis. 110 Ceramide inhibits insulin sensitivity in primary bovine adipocytes. J. E. Rico* 1,2, W. A. Myers 1,2, D. J. Laub 2, A. N. Davis 1,2, Q. Zeng 2, and J. W. McFadden 1,2, 1 Cornell University, Ithaca, NY, 2 West Virginia University, Morgantown, WV. In non-ruminants, the sphingolipid ceramide reduces insulin sensitivity by inactivating protein kinase B (AKT) within the insulin signaling pathway. We have established that ceramide accumulation develops with impaired systemic insulin action in ruminants during the transition from gestation to lactation, dietary palmitic acid supplementation, controlled nutrient restriction, or intravenous triacylglycerol infusion. We hypothesized that ceramide promotes AKT inactivation and antagonizes insulin sensitivity in primary bovine adipocytes. Stromal-vascular cells were grown from bovine subcutaneous adipose tissue explants and cultured in differentiation media. To modify ceramide supply, we treated differentiated adipocytes with an inhibitor of de novo ceramide synthesis (10 µm myriocin) or cell-permeable C2:0-ceramide (100 µm) for 18 or 2 h, respectively. Untreated controls were included for comparison. Insulin-stimulated AKT activation (i.e., Ser-473 phosphorylation) and 2-deoxy-D-[3H]-glucose (2DOG) uptake were measured using immunoblotting and radioactivity assays, respectively. Adipocyte ceramide concentrations were measured using LC/MS. Data were analyzed under a mixed model including the fixed effect of treatment and the random effect of experiment and replicate within treatment. Relative to undifferentiated adipocytes, triacylglycerol accumulation was ~7-fold greater post differentiation with visible lipid droplet formation (P < 0.01). Pronounced reductions in total ceramide, monohexosylceramide, and lactosylceramide concentrations were observed in differentiated adipocytes treated with myriocin (P < 0.01). For example, myriocin decreased C22:0 and C24:0 ceramide by ~77% (P < 0.01). The insulin-stimulated ratio of phosphorylated AKT to total AKT increased with myriocin by 190% (β-actin normalized; P < 0.05), whereas the ratio of phosphorylated AKT to total AKT decreased by 76% with C2:0-ceramide (P < 0.05). Moreover, adipocyte insulin-stimulated 2DOG uptake was decreased with C2:0-ceramide and increased with myriocin (P < 0.05). We conclude that ceramide inhibits insulin stimulated glucose uptake by downregulating AKT activation in primary bovine adipocytes. Key Words: adipocyte, ceramide, insulin signaling 111 Effects of commercially available palmitic and stearic acid-enriched supplements on nutrient digestibility and production responses of lactating dairy cows. M. M. Western*, J. de Souza, and A. L. Lock, Michigan State University, East Lansing, MI. We evaluated the effects of commercially available fatty acid (FA) supplements enriched with palmitic (C16:0) or stearic acid (C18:0) on nutrient digestibility and production responses of dairy cows. Thirty-six multiparous Holstein cows (146 ± 84 DIM) were used in a truncated Latin square arrangement of treatments with 2 consecutive 35-d periods, with the final 5 d used for sample and data collection. Treatments were (1) control (CON; diet containing no supplemental FA); (2) C16:0-supplement (PA; 84% C16:0, 4% C18:0, 9% C18:1); and (3) C16:0 and C18:0-supplement (SA; 33% C16:0, 53% C18:0, 5% C18:1). Supplements were fed at 1.5% DM and replaced soyhulls in CON. The statistical model included the random effect of cow nested within square and the fixed effects of treatment, period, square, and their interactions. Contrasts were (1) overall effect of FA treatments [CON vs. FAT; 1/2 (PA + SA)]; and (2) effect of FA supplement (PA vs. SA). Results are presented in the following sequence: CON, PA, SA. There were no effects of treatments on DMI, BW, or BW change. Compared with CON, FAT treatments decreased total FA (76.7, 76.3, 67.6%, P < 0.01), 16-carbon FA (74.3, 69.0, 68.0%, P < 0.01), and 18-carbon FA (78.3, 82.1, 67.2%, P < 0.01) digestibility. Compared with SA, PA increased DM and NDF digestibility by 3.6 and 4.8% units, respectively (P < 0.01). PA also increased total FA and 18-carbon FA digestibility (P < 0.01) but did not alter 16-carbon FA digestibility (P = 0.55). Using a Lucas test, apparent digestibility coefficients were 0.73 and 0.62 for the PA and SA supplements, respectively. Compared with CON, FAT increased milk yield (43.1, 45.7, 44.8 kg/d, P = 0.01), tended to increase ECM (44.8, 46.4, 44.5 kg/d, P = 0.08), but did not affect yield of milk fat (1.55, 1.65, 1.52 kg/d P = 0.19) or milk protein (1.43, 1.44, 1.46 kg/d, P = 0.32). Compared with SA, PA increased ECM (P = 0.03) and milk fat yield, (P < 0.01) but had no effect on milk protein yield (P = 0.47). Our results indicate that high producing dairy cows respond better to a FA supplement enriched in C16:0 compared with a supplement enriched in C18:0, which is likely due in part to PA increasing FA and NDF digestibility compared with SA. Key Words: digestibility, palmitic acid, stearic acid 112 Impact of abomasal infusion of oleic acid on fatty acid digestibility and milk production of dairy cows. C. M. Prom* 1, J. Newbold 2, and A. L. Lock 1, 1 Michigan State University, East Lansing, MI, 2 Volac International Ltd., Orwell, Royston, United Kingdom. Our objective was to determine the impact of abomasal infusion of increasing doses of oleic acid (OA; cis-9 C18:1) on fatty acid (FA) digestibility and production responses of lactating dairy cows. Eight rumen-cannulated multiparous Holstein cows (138 ± 71 DIM) were randomly assigned to treatment sequence in a replicated 4 4 Latin square design with 18-d periods consisting of 7 d of washout and 11 d of infusion. Animals received the same diet, which contained (%DM) 27.8% NDF, 17.0% CP, 27% starch, and 3.3% FA (1.8% DM from a saturated FA supplement containing 31% C16:0 and 54% C18:0). Treatments were 0, 20, 40, or 60 g/d of OA delivered at 6-h intervals. Production and digestibility data were collected during the last 4 d of each infusion period. The statistical model contained the random effect of cow within square and the fixed effects of period, treatment, and their interaction. Results in the text are presented in the following order: 0, 20, 40, and 60 g/d. OA infusion did not affect dry matter intake (P = 0.31) or NDF digestibility (P = 0.54). OA linearly increased digestibility of total FA (61.1, 66.7, 65.8, and 67.4; P < 0.01), 16-carbon FA (60.4, 66.7, 66.4, and 68.0; P < 0.01), and 18-carbon FA (61.3, 66.7, 65.5, and 67.1; P < 0.01). Therefore, OA linearly increased absorbed total FA (638, 705, 681, and 724; P = 0.04), 16-carbon FA (141, 157, 153, and 163; P = 0.02), and 18-carbon FA (457, 504, 484, and 516; P = 0.05). OA tended to linearly increase milk yield (P = 0.09), 3.5% fat-corrected milk (P = 0.08), and energy-corrected milk (P = 0.09). OA did not affect milk fat yield but tended to increase milk fat concentration (3.35, 3.36, 3.42, and 3.21%; quadratic P = 0.06). OA did not affect the yield of de novo or mixed milk FA but linearly increased yield of preformed FA (578, 587, 599, and 623 g/d; P = 0.04), predominantly through increased yield of OA (linear P < 0.01). OA also tended to linearly increase C4:0 yield (P = 0.09) in milk. OA increased plasma insulin concentration from 0.80 mg/l to 0.98 mg/l, but did not differ by dose (P < 0.01). In conclu 159

4 sion, OA infusion increased FA digestibility, preformed milk FA yield, and circulating insulin without negatively affecting dry matter intake. Key Words: digestibility, milk production, insulin 113 Long-term effects of olive oil and hydrogenated vegetable oil supplementation on the expression of genes related to fatty acid metabolism in adipose tissue of dairy cows. E. Vargas- Bello-Pérez* 1, N. Cancino-Padilla 1, P. Sciarresi-Arechabala 2, M. S. Morales 2, J. Romero 3, M. Bionaz 4, and J. J. Loor 5, 1 Pontificia Universidad Católica de Chile, Santiago, Chile, 2 Universidad de Chile, Santiago, Chile, 3 Instituto de Nutrición y Tecnología de los Alimentos, Santiago, Chile, 4 Oregon State University, Corvallis, OR, 5 University of Illinois, Urbana, IL. The objective of this study was to characterize the mrna expression in subcutaneous adipose tissue (AT) via RTqPCR of genes related to fatty acid (FA) synthesis and desaturation (ACACA, FADS2, FASN, SCD1); regulation of transcription (INSIG1, SCAP, SREBF1, THRSP, PPARGC1A); lipid droplet formation (PLIN2, SLC27A6); triacylglycerol synthesis (DGAT1, DGAT2, LPIN1); FA import into cells (LPL, VLDLR); and intracellular transport (ACSL1, ACSL2, FABP3, FABP4) in dairy cows supplemented with unsaturated (olive oil; OO) and saturated (hydrogenated vegetable oil; HVO) lipids. Fifteen cows averaging 189 ± 28 d in milk (average ± SD) at the beginning of the study were randomly assigned to treatment groups. During 9 wk animals were fed a control diet with no added lipid (n = 5 cows; basal diet), and fat-supplemented diets containing OO (n = 5 cows; 30 g/kg DM) and HVO (n = 5 cows; 30 g/kg DM). AT was obtained from the tail-head area at the onset of the study (P0) and after 9 wk of supplementation. Compared with control and HVO, OO increased (P < 0.05) milk yield, and reduced (P < 0.05) milk fat yield and milk somatic cell counts. Relative expression was determined using P0 as a reference condition. Relative mrna expression was determined using the Pair Wise Fixed Reallocation Randomization Test built in REST (2008) using 5000 iterations. Correction and normalization to the reference genes (GAPDH, UXH, EIF3K) were calculated using the Ct values for each sample as the input variable. OO upregulated (P < 0.05) the expression of ACACA, PLIN2, THRSP, DGAT1, LPL, and FABP4. HVO upregulated (P < 0.05) the expression of SLC27A6. Overall, OO upregulated some genes related to FA metabolism in adipose tissue whereas HVO induced upregulation on a gene related to FA import. Our results suggest that unsaturated lipid sources may have stronger lipogenic effects in bovine AT than saturated sources in long-term supplementation. This study provides further knowledge on FA metabolism in adipose tissue and data can be used to develop new strategies for a better nutritional management in dairy cows. This study was sponsored by a research grant from FONDECYT , Chile. Key Words: fatty acid metabolism, gene expression, olive oil 114 Altering the ratio of dietary palmitic and oleic acids impacts production and metabolic responses during the immediate postpartum and carryover period in dairy cows. J. de Souza*, C. Prom, and A. L. Lock, Department of Animal Science, Michigan State University, East Lansing, MI. Fifty-six multiparous cows were used in a randomized complete block design to determine the effects of altering the ratio of dietary palmitic and oleic acids on production and metabolic responses. The treatments fed from 1 to 24 DIM were a control diet (CON; non-fa supplemented diet) and diets supplemented at 1.5% DM with FA supplements differing in the ratio of palmitic (C16:0) and oleic (C18:1) acids. FA treatment diets were 80:10 (80% C16:0+10% C18:1); 70:20 (70% C16:0+20% C18:1); and 60:30 (60% C16:0+30% C18:1). From d 25 to 60 postpartum (carryover period), all cows were offered a common diet to evaluate carryover effects. The statistical model included the random effect of block and cow, and the fixed effect of treatment, time, and its interaction. Results are presented in the following sequence: CON, 80:10, 70:20, and 60:30. During the fresh period, FA-supplemented diets increased milk yield (46.5, 48.6, 48.8 and 49.7 kg/d; P < 0.05), ECM (50.2, 54.8, 53.5 and 54.3 kg/d; P < 0.01), and milk fat yield (1.90, 2.15, 2.08 and 2.09 kg/d; P < 0.01) compared with CON. Increasing C18:1 in FA treatments decreased plasma NEFA (0.72, 0.84, 0.75, and 0.67 meq/l; quadratic, P < 0.05) and BW loss ( 1.55, 2.54, 1.63, and 1.48 kg/d; quadratic, P < 0.05), and tended to increase DMI (20.3, 20.7, 20.9, 21.8 kg/d; linear, P < 0.1) and plasma insulin (0.26, 0.27, 0.31, and 0.31 ug/l; quadratic, P < 0.1). Increasing C18:1 in FA treatments did not affect milk yield, ECM, and the yields of milk fat and protein. During the carryover period, cows that received FA-supplemented diets during the fresh period increased ECM (55.6, 59.5, 58.7, and 60.3 kg/d; P < 0.05), and milk fat yield (1.91, 2.06, 2.11, and 2.13 kg/d; P < 0.05) compared with CON. Our results indicate that feeding FA supplements containing C16:0 and C18:1 during the immediate postpartum period increased milk yield and ECM compared with a nonfat control diet. Increasing C18:1 in the FA supplement reduced BW loss and plasma NEFA and tended to increase DMI. Also, the diets fed during the immediate postpartum period had a tremendous carryover effect during early lactation, when cows were fed a common diet. Key Words: body condition, fat supplementation, postpartum 115 Changes in the omasal flow of long-chain fatty acids alters the yield of de novo and preformed milk fatty acids. J. de Souza* 1, H. Leskinen 2, K. J. Shingfield 4,2, A. L. Lock 1, and P. Huhtanen 3, 1 Department of Animal Science, Michigan State University, East Lansing, MI, 2 Animal Genomics, Green Technology, Natural Resources Institute Finland (Luke), Jokioinen, Finland, 3 Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, Umeå, Sweden, 4 Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, United Kingdom. We determined milk fatty acid (FA) yield response in relation to omasal flow of long-chain FA. Our analysis used individual observations (n = 132) in lactating Nordic Red dairy cows from 9 Latin square or switchback design studies. The yield of milk FA (g/d) was classified as: < 16C (summation of FA lower than 16-carbon, de novo FA), 16C (summation of 16-carbon FA, mixed FA), > 16C (summation of FA greater than 16-carbon, preformed FA). Mixed model regressions were developed between variables of interest taking into account experiment, period within experiment, and cow within experiment as random factors. Increasing palmitic acid (16:0) omasal flow (g/d) linearly increased the yield of < 16C FA [158 ± ± :0 flow, P < 0.001, R 2 = 0.68], 16C FA [207 ± ± :0 flow, P < 0.001, R 2 = 0.73], > 16C FA [333 ± ± :0 flow, P = 0.02, R 2 = 0.29], and total FA [740 ± ± :0 flow, P < 0.001, R 2 = 0.72] in milk. In contrast, increasing stearic acid (18:0) omasal flow (g/d) did not affect the yield of < 16C and 16C (P > 0.05), but quadratically increased the yield of > 16C [233 ± ± :0 flow ± :0 flow 2, P < 0.001, R 2 = 0.84] and total FA [795 ± ± :0 flow ± :0 flow 2, P < 0.01, R 2 = 0.48] in milk. For the flow of 18:0, maximum > 16C and total FA yields were achieved when 18:0 flow was 1065 and 943 g/d, respectively. Increasing oleic acid (cis-9 18:1) omasal flow 160

5 (g/d) linearly increased the yield of < 16C [246 ± ± :1 flow, P < 0.01, R 2 = 0.37] and total FA [965 ± ± :1 flow, P < 0.01, R 2 = 0.37] in milk, and did not affect 16C and > 16C (P > 0.05). Increasing linoleic acid (18:2n-6) omasal flow (g/d) linearly increased the yield of < 16C [206 ± ± :2n-6 flow, P < 0.001, R 2 = 0.96], 16C [278 ± ± :2n-6 flow, P < 0.001, R 2 = 0.63], and total FA [888 ± ± :2n-6 flow, P < 0.001, R 2 = 0.65] in milk. Our results highlight the interdependence between de novo synthesized and preformed milk FA and demonstrates that effects on de novo, mixed, and preformed milk FA synthesis are dependent upon the amount and profile of absorbed FA. Key Words: fatty acids, milk fat, meta-analysis 116 Comparison of fat supplements containing palmitic or stearic acid on intake and production in lactating dairy cows. R. Shepardson* and K. Harvatine, Penn State University, University Park, PA. Fatty acid (FA) supplements based on palmitic acid (PA) and stearic acid (SA) are commonly used to increase dietary energy density for lactating dairy cows. There is limited literature directly comparing supplements enriched in PA and SA to a blend of these FA. Our hypothesis was that PA would increase milk fat and decrease intake while SA would have no effect on intake. Treatments were (1) Control (CON; no additional fat), (2) high palmitic supplement (HP; 90.7% C16:0, 2.4% C18:0, and 5.8% cis-9 C18:1), (3) high stearic supplement (HS; 1.7% C16:0, 90.5% C18:0, and 5.9% cis-9 C18:1), and (4) a blend of PA and SA (INT; 45.7% C16:0, 46.4% C18:0, and 5.7% cis-9 C18:1). Twelve multiparous, post-peak (138.5 ± 21.0 DIM) Holstein cows were arranged in a 4 4 Latin square design with 21-d periods. Samples were collected the last 3 d of each period. The statistical model included the random effect of cow and period and the fixed effect of treatment. There were no differences between treatments for DMI (25.03 ± 2.29 kg), milk yield (39.19 ± 7.31 kg), milk protein concentration and yield, or MUN. Milk fat percent was increased 0.44 and 0.14 percentage points by HP compared with CON and SA, respectively (P = 0.03). Milk fat yield was increased by 110 g/d by HP and 140 g/d by INT compared with CON (P < 0.01). Although HP increased milk fat concentration 0.34 percentage points compared with INT, fat yield did not differ. Milk fat concentration and yield were not different between CON and SA. As expected, HP and INT increased C16 FA in milk fat and decreased both de novo and preformed FA. Preformed FA concentration was the highest in SA (both P < ). There was a trend for HP to decrease de novo FA yield (P = 0.09). The INT treatment increased preformed FA yield 60.5 and 50.4 g/d compared with CON and HP (P = 0.02). The HP and INT treatment increased yield of C16 FA and 90 g/d compared with CON, respectively. On the basis of fat yield, the 2 supplements that had greater amounts of PA had a greater response. Key Words: fatty acid supplement, milk fatty acid profile 161