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The objectives were to determine the effects of nicotinic acid (NA) on blood metabolites (experiment 1) and whether successive doses of NA could induce sustained reductions of plasma nonesterified fatty acids (NEFA; experiment 2) in feed-restricted, nonlactating Holstein cows. Experiment 1 was a single 4 x 4 Latin square with 1-wk periods. Each period consisted of 2.5 d of feed restriction to increase plasma NEFA and 4.5 d of ad libitum feeding. Treatments were abomasal administration of 0, 6, 30, or 60 mg of NA/kg of body weight (BW), given as a single bolus 48 h after initiation of feed restriction. Plasma NEFA concentration decreased from 546 µEq/L to 208 ± 141 µEq/L at 1 h after the infusion of 6 mg of NA/kg of BW, and to less than 100 ± 148 µEq/L at 3 h after the abomasal infusion of the 2 highest doses of NA. A rebound occurred after the initial decrease of plasma NEFA concentration. The rebound lasted up to 9 h for the 30-mg dose of NA, and up to 6 h for the 6-mg dose. Experiment 2 was a randomized complete block design with 3 treatments and 6 cows. Starting at 48 h of feed restriction, cows received 9 hourly abomasal infusions of 0, 6, or 10 mg of NA/kg of BW. Plasma NEFA concentrations decreased from 553 µEq/L ± 24 immediately before the initiation of treatments to <100 µEq/L during hourly infusions of 6 or 10 mg of NA/kg. Data suggest that the maximal antilipolytic response was achieved with the lowest dose of NA. A rebound of NEFA started 2 to 3 h after NA infusions were terminated. In both experiments, the NEFA rebound period coincided with increases in insulin and no change or increased glucose concentrations, suggesting a state of insulin resistance induced by elevated NEFA. This model for reducing plasma NEFA concentration by abomasal infusions of NA can be used to study the metabolic ramifications of elevated vs. reduced NEFA concentrations. The data demonstrate potential benefits and pitfalls of using NA to regulate plasma NEFA and prevent lipid-related metabolic disorders. [ABSTRACT FROM AUTHOR]

Sixty-five Holstein cows were used to evaluate management schemes involving altered dry period (DP) lengths on subsequent milk production, energy balance (EB), and metabolic variables. Cows were assigned to one of 3 treatments: traditional 56-d DP (fed a low-energy diet from -56 to -29 d and a moderate energy diet from -28 d to parturition; T), 28-d DP (continuously fed a high energy diet; S), and no planned DP (continuously fed a high energy diet; N). Prepartum DM intake (DMI), measured from 56 d prepartum through parturition, was lower for cows on the T treatment than for cows on the S treatment and was higher for cows on the N treatment than for cows on the S treatment. There were no differences in prepartum plasma glucose, and β-hydroxybutryric acid; there was a treatment by time interaction for prepartum plasma nonesterified fatty acid (NEFA). There was no difference in prepartum liver triglyceride (TG); postpartum liver TG was decreased for cows on the N treatment compared with cows on the S treatment, but was similar for cows on the T and S treatments. Postpartum NEFA was similar between cows on the T and S treatments, but was greater for cows on the S treatment than for cows on the N treatment. Postpartum glucose was greater for cows on the N treatment compared with cows on the S treatment and tended to be greater for cows on the S treatment than for cows on the T treatment. There was no difference in postpartum solids-corrected milk (SCM) production or DMI by cows on the T vs. S treatment. However, there was a tendency toward lower postpartum SCM production by cows on the N vs. S treatment and a tendency for greater postpartum DMI by cows on the N vs. S treatment. Postpartum EB was greater for cows on the S vs. T treatment and the N vs. S treatment. In general, T and S management schemes had similar effects on DMI, SCM, and metabolic variables in the first 70 d of the subsequent lactation. Eliminating the DP improved energy and metabolic status. [ABSTRACT FROM AUTHOR]

The objective was to determine the effects of linoleic acid and different isomers of conjugated linoleic acid (CLA) at different concentrations on hepatic lipid and glucose metabolism in the bovine. Monolayer cultures of hepatocytes obtained from 7- to 10-d-old Holstein bull calves were exposed to treatments from 16 to 64 h after plating. The treatments included 1.0 mM palmitic acid plus either 0.1 or 1.0 mM of cis-9, cis-12 linoleic acid, cis-9, trans-11 CLA, or trans-10, cis-12 CLA. Metabolism of palmitic acid to cellular triacylglycerol (TAG) was decreased when media contained cis-9, trans-11 compared with trans-10, cis-12 CLA. Total cellular TAG content was increased for the CLA isomers compared to cis-9, cis-12 linoleic acid. Both CLA isomers increased palmitic acid incorporation into phospholipids, cholesterol, and media triacylglycerol compared with cis-9, cis-12 linoleic acid at a concentration of 1.0 mM. Increasing the concentration of treatment fatty acids from 0.1 to 1.0 mM decreased oxidation of palmitic acid to acid-soluble products, but no effects of fatty acids were observed. There was no treatment effect on rates of gluconeogenesis from propionic acid. Overall, CLA isomers elicited changes in palmitic acid metabolism to cellular and media triacylglycerol, and cellular phospholipids and cholesterol, but had little or no effect on other measured pathways of lipid metabolism or gluconeogenesis in bovine hepatocytes. [ABSTRACT FROM AUTHOR]

Deals with a study which determined the long-term effects of specific long chain fatty acids on hepatic lipid and glucose metabolism in monolayer cultures of bovine hepatocytes. Primary end-products of fatty acid oxidation; Glucose formation from propionic acid; Influence of fatty acids on lipid and glucose metabolism in monolayer cultures of bovine hepatocytes.

Liver biopsies are commonly used to obtain tissue to determine hepatic lipid content in ruminants, particularly the dairy cow. The location of the biopsy is unknown and it is assumed that the sample is representative of the entire organ. This study investigated the distribution of lipid in the caudate, left, right, and quadrate lobes of goat livers having normal or elevated lipid content. Goats that experienced negative energy balance for 4 days had significantly greater hepatic total lipids, primarily due to a 4-fold increase in triglycerides, than goats in positive energy balance. Triglyceride concentrations were similar among lobes within energy balance groups. Within the positive energy balance treatment, the caudate lobe had a significantly greater total lipid concentration than the other lobes, which had a similar lipid concentration. Total lipid concentrations were similar among lobes obtained from goats in negative energy balance. Zusammenfassung Lipidverteilung in der Leber bei Milchziegen mit positiver und negativer Energiebilanz Zur Bestimmung des Lipidgehalts der Leber wird bei Wiederkäuern, insbesondere bei der Milchkuh, die Leberbiopsie zur Gewebsgewinnung herangezogen. Die Lokalisation der Biopsie ist dabei unbekannt, jedoch wird angenommen, daß die Probe für das gesamte Organ repräsentativ ist. In der vorliegenden Studie wurde der Lipidgehalt im caudalen, linken, rechten und quadratischen Lappen von Ziegenlebern mit normalem und erhöhtem Lipidgehalt untersucht. Bei Ziegen mit 4 Tage dauernder negativer Energiebilanz war der Gesamtlipidgehalt der Leber signifikant höher als bei Ziegen mit positiver Energiebilanz. Dies war hauptsächlich auf eine 4fache Erhöhung des Triglyceridgehalts zurückzuführen. Der Triglyceridgehalt war in den einzelnen Leberlappen der beiden Gruppen jeweils ähnlich. Bei positiver Energiebilanz wies der caudale Leberlappen einen signifikant höheren Gesamtlipidgehalt auf als die anderen Leberlappen, deren Lipidgehalt ähnlich war. Bei negativer Energiebilanz war der Gesamtlipidgehalt aller Leberlappen ähnlich. [ABSTRACT FROM AUTHOR]

Studies net uptake of nonesterified long chain fatty acids by the perfused caudate lobe of the caprine liver of goats. Method of the study; Results and discussion; Conclusion.

The objective was to investigate the effect of different fatty acids (FA) on the gene expression of ApoB100, ApoE, and microsomal triglyceride transfer protein (MTP), which are involved in the VLDL synthesis and secretion by bovine hepatocytes. Hepatocytes were isolated from three 7 to 10 d old male Holstein calves, cultured in monolayer, and treated for 48 h (from 20 to 68 h after seeding) with either no FA added (control) or 0.1, 0.2 and 1.0 mM of C16:0, C18:0, C18:1, C18:2, C18:3, C20:5, C22:6, or a physiological FA mix (NEFA; 15% C18:0, 30% C16:0, 45% C18:1, 5% C16:1, and 5% C18:2). Gene expression was quantified by Real-Time PCR, using ubiquitin as internal control. Data were analyzed by the Mixed Procedure of SAS using a model with fixed effect of treatment and random effect of calf. Contrasts were 1) linear and 2) quadratic concentration effects of single FA treatments; 3) 1inear and 4) quadratic concentration of NEFA treatment (positive control); 5) saturated and mono-unsaturated vs. polyunsaturated (PUFA); 6) C18 PUFA vs. long chain PUFA; 7) omega-6 vs. omega-3; 8) C20:5 vs. C22:6. Increasing the length and degree of unsaturation of FA down-regulated gene expression of ApoB and MTP (contrasts 5, 6, 7; P < 0.05) and ApoE (contrasts 6, 7, 8; P < 0.01). Increasing the concentration of single FA down-regulated gene expression of ApoE and MTP (contrast 1; P < 0.05), but not of ApoB. Increasing NEFA concentration up-regulated gene expression of ApoB100 (contrast 3; P < 0.01), ApoE (contrasts 3, 4; P < 0.05) and MTP (contrast 4; P < 0.001). These results show that FA modulate the gene expression of proteins involved in VLDL metabolism. Additionally, concentration effects of the NEFA and single FA treatments differed; for most single FA treatments, increasing concentration down-regulated gene expression while increasing the concentration of NEFA mix, which reflects the FA profile in vivo, up-regulated gene expression. [ABSTRACT FROM AUTHOR]

In a previous study (Gumen et al., 2005; JDS 88:2401), although cows with a reduced dry period appeared to have improved reproduction, too few cows were evaluated to provide reliable data. Cows (n=772) in a commercial dairy herd were used in a randomized design to evaluate the effect of dry period duration on days to first ovulation, days to first AI, first service conception rate, days open, and percentage of cows pregnant at 150 DIM. Lactating cows analyzed for reproduction received a 55 (C; n=342) or 34 d (S; n=353) dry period. Cows that did not reach 45 DIM or more were classified as do not breed were removed from the study. Dry C cows were fed a low-energy diet until 34 d before their expected calving date and then all cows (C and S) were fed a moderate-energy transition diet until calving. Beginning two weeks postpartum, weekly blood samples were collected and analyzed for progesterone. Cows received AI based on removed tail-chalk after 45 DIM followed by Ovsynch and timed AI (37% of the first AIs) after 80 DIM if not previously inseminated. There was a treatment by week interaction (P < 0.01) for body condition score with C greater than S at wk 3 prepartum (3.76 ± 0.02 vs 3.21 ± 0.02). Based on survival analysis, S cows had fewer (P < 0.01) days to first ovulation (median days = 35 vs 43 d) as determined by serum progesterone >1.0 ng/ml. Survival analysis showed a tendency (P = 0.09) for S cows to have fewer days to first service (median days = 67 vs 72 d); however, first service conception rate did not differ between treatments (29.8 vs 32.0%). The proportion of cows pregnant at 150 DIM was greater (P < 0.05) for S (51.8%) than for C (43.9%) cows. Survival analysis indicated a treatment effect for days open (median = 166 vs 130 for C vs S cows). Thus, decreasing the duration of the dry period from 55 to 34 d improved reproductive efficiency based on fewer days open and more cows pregnant at 150 DIM. [ABSTRACT FROM AUTHOR]

Previous research has implicated linseed oil in altering lipid metabolism of dairy cattle when infused intravenously as lipid emulsion. The objective was to determine the effects of abomasal linseed oil (LO) infusion on liver triglyceride (TG) accumulation and subcutaneous adipose tissue lipolysis during fatty liver induction. Eight nonpregnant, nonlactating Holstein cows were randomly assigned to treatments in a replicated 4 x 4 Latin square design. Treatments included abomasal infusion of water (W), tallow (T), LO, or half tallow plus half LO (LOT) at a rate of 0.56 g/kg BW per day for 4 d. Daily treatments were administered directly into the abomasum, divided into 6 doses and administered every 4 h. Infusion of treatments was concurrent with a 4 d fast. Cows were fed ad libitum for 24 d between periods of fasting and lipid infusion. T contained 43% C18:1, 24% C16:0 and 14% C18:0. LO contained 51% C18:3, and 17% C18:2. For most parameters, contrasts were: W vs. LO + LOT + T (effect of lipid), LO vs. T (linear effect of LO), and LOT vs. LO + T (nonlinear dose effect of LO). For measurement of blood fatty acid composition, differences among treatment means were determined using the PDIFF procedure of PROC MIXED. Infusion of linseed oil (LO or LOT) increased α-linolenic acid (g/100 g fatty acid) in serum (P < 0.05) but not in the nonesterified fatty acid (NEFA) fraction of plasma. Treatments had no effect on plasma NEFA concentrations. Infusion of LO increased total serum fatty acid concentration (nonlinear dose effect; P = 0.06). Abomasal infusion of lipid significantly increased isoproterenol stimulated lipolysis by subcutaneous adipose tissue explants in vitro. Liver TG content increased 4.8, 4.9, 2.3 and 2.3 μg TG/ μg of DNA during the fast for W, LO, LOT and T, respectively; infusion of lipid decreased liver TG accumulation (P = 0.06) when compared to W, but this was due to T (LO vs. T; P = 0.03). Abomasal LO infusion failed to reduce liver TG accumulation, plasma NEFA concentration or alter subcutaneous adipose tissue lipolysis. [ABSTRACT FROM AUTHOR]

Recent experiments to examine the effects of dry period length on subsequent lactation have employed insufficient cows to determine effects on health disorders. This study was conducted on a large commercial dairy herd to evaluate the effect of dry period length on milk production, milk components, colostrum quality, and incidences of mastitis and metabolic disorders. Dry cows (n=772) were randomly assigned to receive a dry period of 55 (C; n=382) or 34 d (S; n=390). Dry cows on C were fed a low-energy diet until 34 d prior to expected calving and then all cows were fed a moderate-energy transition diet. Milk yield was recorded every 15 d through 150 DIM and milk was sampled every 30 d through 100 DIM to analyze milk components. Cows on C produced more milk than cows on S (P < 0.0001; 43.8 vs. 41.8 kg/d). Cows in their 3rd or greater lactation produced more milk than cows in their 2nd lactation (P < 0.0001; 41.5 vs. 44.1 kg/d). There was no treatment by time or treatment by parity interaction for milk yield. Fat percent was affected by treatment (P < 0.05; C = 3.35 vs. S = 3.48) and parity (P < 0.05; 3.36 vs. 3.47 for 2nd and 3rd and greater lactation, respectively). Fat yield was not affected by treatment, but there was a parity effect (P < 0.0001; 1.40 vs. 1.53 kg/d for 2nd and 3rd and greater lactation, respectively). Protein percent was affected by treatment (P < 0.0001; C= 2.69 vs. S = 2.82) and parity (P < 0.0001; 2.82 vs. 2.70 for 2nd and 3rd and greater lactation, respectively). Protein yield was not different for treatment, but was for parity (P < 0.05; 1.17 vs. 1.20 kg/d for 2nd and 3rd and greater lactation, respectively). IgG concentration in colostrum was not affected by treatment. The incidences of mastitis, displaced abomasum, ketosis, metritis and retained placenta did not differ between treatments. There appears to be no effect of shortening the dry period from 55 to 34 d on health. [ABSTRACT FROM AUTHOR]

Fifty-eight multiparous Holstein cows were used in a completely randomized block design to evaluate the effects of feeding Ca salts of trans-octadecenoic fatty acids and linoleic acid on animal performance and lipid metabolism during the transition period. Three weeks before expected calving, cows were fed 1% of the diet dry matter (DM) as Ca salts of palm oil (PFA) or as Ca salts of trans-octadecenoic fatty acids and linoleic acid (TFAL). After calving and until d 28 postpartum, half of the cows from each prepartum treatment were assigned to a diet containing PFA or TFAL at 2% of dietary DM. Pre- and postpartum diets differed only in the type of supplemental fatty acids. After d 28 postpartum, all cows were fed the PFA lactation diet until d 42. Fatty acid supplementation had no effect on pre- or postpartum DM intake or milk production. Milk fat % was lower (P < 0.01) and milk fat yield tended to be lower (P < 0.15) for cows fed TFAL than for cows fed PFA prepartum (3.8 vs. 4.1%, and 1.51 vs. 1.39 kg/d, respectively). Cows fed TFAL postpartum had lower (P < 0.03) milk fat test than cows fed PFA (3.8 vs. 4.0%, respectively), but no effect of postpartum treatment was observed for milk fat yield. Prepartum plasma concentration of nonesterified fatty acids (NEFA) tended to be lower (P < 0.10) for cows fed TFAL than for cows fed PFA (369 vs. 451 μEq/L, respectively). Cows fed TFAL prepartum tended to have lower (P < 0.11) plasma NEFA concentration at d 1 postpartum than cows fed PFA prepartum (792 vs. 989 μEq/L, respectively). Postpartum treatments had no effect on plasma NEFA concentration. No effect of prepartum treatment was observed for liver triglyceride content at d 1 postpartum. Results of this study suggest that feeding Ca salts of trans-octadecenoic acids and linoleic acid during late gestation may cause milk fat depression and lower NEFA mobilization at parturition compared to feeding palm oil fatty acids. [ABSTRACT FROM AUTHOR]

The objective was to test whether abomasal infusion of linseed oil, rich in C18:3, enhances the response to glucose and insulin challenges in Holstein cows when compared to tallow. Eight non-lactating, non-gestating cows were assigned to a cross-over design, fed to meet maintenance requirements and supplemented with abomasal infusions of either linseed oil (L) or tallow (T) at a rate of 0.54 g/kg of BW per d for 5.5 d. This dose is equivalent to a 735-kg cow eating a diet containing 2.7% TG (DM basis) at 2% of BW. Feed and treatments were provided in equal doses every 8 h during the first 3 d of each period, and every 4 h thereafter. Five d after initiation of treatments, glucose tolerance tests (GTT) were performed (0.25g dextrose i.v. bolus/kg BW), followed by insulin challenges (IC; 0.1 IU insulin i.v. bolus/kg BW) 12 h later. Before GTT, plasma glucose concentration was greater for L (66 vs. 63 mg/dl; P < 0.05) and there was no difference in serum insulin (29 vs. 28 μIU/ml; P = 0.81), nor plasma NEFA (113 vs. 106 μEq/L; P = 0.41) for L and T, respectively. There was no difference in glucose clearance parameters after GTT, but insulin concentrations were lower for L during the first 40 minutes after GTT. Accordingly, the insulin response area under the curve to GTT was lower for L than T (9810 vs. 12589 μIU/ml/180 min; P < 0.01). NEFA was higher for L during GTT (108 vs. 89 μEq/L; P < 0.001), possibly due to the lower insulin response to GTT observed with L. Before IC, glucose was similar between treatments (68 vs. 66 mg/dl; P = 0.13), but NEFA was higher for L (151 vs. 90 μEq/L; P < 0.05). Glucose was similar across treatments during the 30 min of sampling period after IC, suggesting that treatments did not affect maximum responsiveness to insulin. NEFA was reduced to same extent by 30 min after IC (20% vs. 17% for L and T; P = 0.71). L had an insulin sensitizing effect compared to T, because lower insulin concentrations caused similar glucose clearance during GTT. [ABSTRACT FROM AUTHOR]

The objective was to determine effect of sampling protocol on plasma non-esterified fatty acid (NEFA) concentration. Plasma NEFA concentration is often used as a tool to assess metabolic status of dairy cows during the periparturient period. In experiment 1, 8 nonlactating, non-gestating dairy cows were blood sampled (basal), moved to an exercise lot for 15 min, returned to stanchions, and sampled immediately and at 5, 15, 30, 60 and 120 min following return. Following 15 min of exercise, cows displayed an increase in plasma NEFA concentration, peaking at 5 min (225 µEq/L) and returning to basal (84 µEq/L) by 30 min (110 µEq/L; P < 0.001). Cows were moved to box stalls overnight and 24 h after basal sample, they were locked up and sampled again. Housing cows in a box stall overnight and locking them in headlocks increased plasma NEFA concentration (184 µEq/L; P < 0.01). In a second experiment at a large freestall commercial dairy, 11 late gestation dairy cows were locked in headlocks at feeding, blood was sampled (0 min), and cows were released and allowed to finish eating and return to stalls. Cows were then herded into headlocks and sampled immediately (120 min), and at 135, 150, and 180 min. Plasma NEFA concentration was highest at initial lockup (284 µEq/L), lowest at 180 min (178 µEq/L) and intermediate at time points in between (P < 0.05). A second group of 10 late gestation dairy cows were locked in headlocks at feeding and blood sampled immediately, and at 5, 15, 30 and 60 min. Plasma NEFA concentration was highest 15 min after being placed in headlocks and lowest at 60 min (221 and 113 µEq/L, respectively; P < 0.05). At each time point, a behavior score was given (1 to 10; 1=calm; 10=extremely excited). There was a significant correlation between plasma NEFA concentration and behavior score (r=0.55 for experiment 1, r=0.31 for experiment 2; P < 0.05). In conclusion, plasma NEFA concentration was altered with different sampling protocols. [ABSTRACT FROM AUTHOR]

The objective was to investigate the relationship between elevated plasma nonesterified fatty acid (NEFA) concentration and insulin resistance in Holstein cows. Six nonlactating, nongestating, ruminally cannulated Holstein cows were blocked by body condition score and randomly assigned to a sequence of 2 treatments in a crossover design. Cows were offered legume and grass hay ad libitum supplemented with minerals and vitamins and were allowed free access to water and a trace mineralized salt block. Mobilization of body reserves was stimulated by withdrawing forage for 48 h before initiation of treatments. Treatments consisted of 11 hourly abomasal infusions of water (control) or nicotinic acid (NA; 6 mg/h per kg of body weight) as an antilipolytic agent. Infusions of NA decreased plasma NEFA concentration from 545 µEq/L to approximately 100 µEq/L within 2 h after initiation of treatments, and differences were maintained throughout infusions. Intravenous glucose tolerance test was performed 8 h after initiation of treatments and was followed by 3 h of blood sampling. The reduction of plasma NEFA concentration led to significantly greater glucose clearance rate (1.9 vs. 1.2%/min) and to decreased glucose half-life (37 vs. 58 min), time to reach basal concentration (81 vs. 114 min) and glucose response area under the curve during 180 min of sampling [6,942 vs. 10,085 (µIU/mL) x 180 min]. Enhanced glucose clearance was achieved when plasma NEFA was reduced by NA, despite lower insulin concentration (70.0 vs. 97.9 ± 13.4 µIU/mL) and a tendency for smaller insulin response area under the curve during 180 min of sampling [7,646 vs. 12,104 ± 2,587 (µIU/mL) x 180 min], reflecting an increased response to endogenous insulin. Based on literature, we do not expect NA to have altered glucose metabolism directly; therefore, this experiment demonstrates a cause and effect relationship between elevated NEFA and insulin resistance in Holstein cows. [ABSTRACT FROM AUTHOR]

The objective was to test whether the induction of elevated blood nonesterified fatty acids (NEFA) by i.v. infusion of a tallow emulsion altered glucose tolerance and responsiveness to insulin in Holstein cows. Six nonlactating, nongestating Holstein cows were assigned to a crossover design. One cow was excluded before initiation of the experiment because of complications from mastitis. Treatments consisted of 11-h i.v. infusions of saline (control) or a 20% (wt/vol) triacylglycerol (TG) emulsion derived from tallow (tallow) to elevate plasma NEFA. Each period consisted of two 11-h infusions (INF1 and INF2), separated by 1 d in which cows were not infused. Intravenous glucose tolerance tests (IVGTT) and insulin challenges (IC) were performed 8 h after initiation of INF1 and INF2, respectively. The infusion of treatments continued during the 3 h of sampling for IVGTT and IC. Cows were fed every 4 h at a rate to meet energy requirements for 5 d prior to each period, and every 2 h during the first 8 h of infusions. Infusion of tallow induced hyperlipidemia by increasing plasma NEFA (295 ± 9 vs. 79 ± 7 µEq/L), serum TG (41.0 ± 6 vs. 11.4 ± 4.4 mg/dL), and glycerol (0.81 ± 0.09 vs. 0.23 ± 0.1 mg/dL) concentrations during INF1. During INF2, tallow treatment increased plasma NEFA (347 vs. 139 ± 18 µEq/L), serum TG (20.8 ± 4.6 vs. 13.1 ± 2.3 mg/dL), and glycerol (0.88 ± 0.04 vs. 0.31 ± 0.02 mg/dL) concentrations. Induction of hyperlipidemia impaired glucose clearance during IVGTT, despite the greater endogenous insulin response to the glucose infusion, leading to a lower insulin sensitivity index [0.29 vs. 1.88 + 0.31 x 10-4 min-1/(µIU/mL)]. Accordingly, hyperlipidemia impaired glucose clearance during IC (1.58 vs. 2.72 %/min), reflecting lower responsiveness to insulin. These data show that induction of hyperlipidemia causes insulin resistance in Holstein cows by impairing both sensitivity and maximum responsiveness to insulin. The induction of insulin resistance by TG, NEFA, or both may increase the availability of glucogenic nutrients to the periparturient dairy cow. Yet excessive elevation of NEFA may potentially lead adipocytes to become more insulin resistant, further increasing plasma NEFA concentration and the risk of metabolic disorders. [ABSTRACT FROM AUTHOR]

The objective of these experiments was to determine effects of sampling protocol on plasma nonesterified fatty acid (NEFA) concentration. In experiment 1, 8 nonlactating, nongestating dairy cows were blood sampled from a jugular vein catheter (basal, 0 min), moved to an exercise lot for 15 min, returned to stanchions, and sampled immediately and at 5, 15, 30, 60, and 120 min following return to their stalls. Following 15 min of exercise, plasma NEFA concentration increased, peaking at 5 min (225 µEq/L) and returning to basal (84 µEq/L) by 30 min (110 µEq/L). Cows were then moved to box stalls overnight, and 24 h after the basal sample, they were locked up and sampled again. Housing cows in a box stall overnight and locking them in headlocks increased plasma NEFA concentration (184 µEq/L). In a second experiment at a large free-stall commercial dairy, 11 late-gestation nonlactating dairy cows were locked in headlocks at feeding, blood was sampled from the coccygeal artery or vein (0 min), and cows were then released and allowed to finish eating and return to their stalls. Cows were then herded to headlocks and sampled immediately at 120 min after initial sampling and at 135, 150, and 180 min. Plasma NEFA concentration was highest at initial lockup (0 rain; 284 µEq/L), lowest at 180 min (178 µEq/L), and intermediate at time points in between. A second group of 10 late-gestation nonlactating dairy cows were locked in headlocks at feeding, and blood was sampled immediately and at 5, 15, 30, and 60 min. Plasma NEFA concentration was highest 15 min after being placed in headlocks and lowest 60 min after lockup (221 and 113 txEq/ L, respectively). At each time point in experiments 1 and 2, a behavior score was given (1 to 10; 1 = calm; 10 = extremely excited). In both experiments, there was a significant correlation between the plasma NEFA concentration and behavior score. In conclusion, plasma NEFA concentration was affected by sampling protocol. [ABSTRACT FROM AUTHOR]

There has been substantial recent interest in shortening dry periods; however, the effects of this management change on reproduction have not been adequately evaluated. Holstein cows (n = 58) were assigned in a randomized block design to 1 of 3 treatments: 1) traditional (T) dry period (-56 d) in which cows were fed a low energy diet from 56 to 29 d prepartum followed by a moderate energy diet for 28 d; 2) shortened (S) dry period (∼28 d) in which cows were fed continuously a high energy diet; or 3) no planned (N) dry period in which cows were fed continuously a high energy diet. All cows received a high energy lactation diet after calving. Ovaries were evaluated by ultrasound and blood samples collected 3 times weekly beginning at d 6 or 7 postpartum until 7 d after second ovulation. Average days from calving until first detection of a 10-mm follicle were fewer in N (8.0 d) and S (8.9 d) than in T (10.5 d) cows. Time from calving to first ovulation was earlier in N (13.2 d) than in S (23.8 d) and T (31.9 d) cows. A greater percentage of follicles of the first follicular wave ovulated in N (89%; 16/18) than in T (42%; 8/19), with S (62%; 13/21) cows being intermediate. Double ovulation rate at the first ovulation was greater in T (61%) than N (16%), with S (35%) intermediate. No difference was detected in double ovulation rate at second ovulation (13/56). Number of cows with persistent corpus luteum (>30 d; 15/56) was not different among groups; however, short luteal phases were greater in N (28%; 5/18) than S (0%; 0/20) cows. Days to first artificial insemination were fewer in N (69.4 d) and S (68.0 d) than in T (75.0 d). First-service conception rate was greater in N (55%; 11/20) than in T (20%; 4/20), with S (26%; 6/23) cows being intermediate. Days open in pregnant cows were fewer in N (93.8 d) than in T (145.4 d), with S (121.2 d) cows being intermediate. Thus, shortening or eliminating the dry period leads to earlier postpartum ovulation and the result. [ABSTRACT FROM AUTHOR]

The objective was to determine the effects of intravenous infusion of triacylglycerol (TAG) emulsions derived from different lipid sources on energy metabolism during a 4-d fast. Six nonpregnant, nonlactating multiparous Holstein cows were randomly assigned to treatments in a replicated 3 x 3 Latin Square design. Treatments included intravenous infusion of tallow, linseed oil, or fish oil emulsions at a rate of 0.54 g of TAG/kg of body weight per day; infusions were concurrent with a 4-d fast. The emulsions were administered for 20 to 30 min every 4 h throughout the 4-d fast. Cows were fed ad libitum for 24 d between the fast/infusion periods. Infusion of tallow, linseed oil, or fish oil emulsions increased plasma concentrations of palmitic acid, linolenic acid, and eicosapentaenoic and docosahexaenoic acids, respectively. Infusion of linseed oil emulsion decreased plasma TAG concentrations compared with tallow and fish oil treatments, which were similar. Infusion of the tallow emulsion resulted in the highest concentrations of plasma nonesterified fatty acid (NEFA), insulin, and glucose, whereas the infusion derived from linseed oil had the lowest NEFA and β-hydroxybutyric acid concentrations. The different TAG emulsions had no effect on total or peroxisomal oxidation of [1-14C]oleic acid in liver homogenates. Liver TAG content increased 12.0, 7.8, and 14.1 µ/µg of DNA during the fast for tallow, linseed oil, and fish oil treatments, respectively; linseed oil was different from fish oil and tended to be different from tallow. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effect of including alfalfa preserved either as silage or long-stem or chopped hay on DMI and milk fat production of dairy cows fed corn silage-based diets with supplemental tallow (T). Fifteen Holstein cows that averaged 117 DIM were used in a replicated 5 x 5 Latin square design with 21-d periods. Treatments (DM basis) were: l) 50% corn silage:50% concentrate without T (CS); 2) 50% corn silage:50% concentrate with 2% T (CST); 3) 25% corn silage:25% short-cut alfalfa hay:50% concentrate with 2% T SAHT); 4) 25% corn silage:25% long-cut alfalfa hay:50% concentrate with 2% T (LAHT); and 5) 25% corn silage:25% alfalfa silage:50% concentrate with 2% T (AST). Cows were allowed ad libitum consumption of a TMR fed 4 times daily. Diets averaged 16.4% CP and 30.3% NDF. Including 2% T in diets with corn silage as the sole forage source decreased DMI and milk fat percentage and yield. Replacing part of corn silage with alfalfa in diets with 2% T increased milk fat percentage and yield. The milk fat of cows fed CST was higher in traps-10 C18:1 than that of cows fed diets with alfalfa. No effect of alfalfa preservation method or hay particle length was observed on DMI and milk production. The milk fat percentage and yield were lower, and the proportion of traps-10 C 18:1 in milk fat was higher for cows fed LAHT than for cows fed SAHT. Alfalfa preservation method had no effect on milk fat yield. Ruminal pH was higher for cows fed alfalfa in the diets, and it was higher for cows fed LAHT than SAHT. Feeding alfalfa silage or chopped hay appears to be more beneficial than long hay in sustaining milk fat production when 2% T is fed with diets high in corn silage. These results support the role of traps fatty acids in milk fat depression. [ABSTRACT FROM AUTHOR]

The objectives were to assess the use of nicotinic acid (NA) to chronically (i.e., 74 h) manipulate plasma nonesterified fatty acid (NEFA) concentrations in partially feed-restricted lactating cows, determine whether the reduction of plasma NEFA altered responses to i.v. glucose tolerance test (ivGTT) and whether NA would attenuate an acute lipolytic stimuli of a β-agonist challenge (ivBAC). Eight lactating dairy cows [244 ± 31 d in milk; 696 ± 63 kg of body weight (BW)] were blocked by breed and body condition score (3.2 ± 0.4) and randomly assigned to a sequence of 2 treatments in a crossover design. Treatments were 74-h continuous abomasal infusion of NA solution (3 mg/h per kg of BW) as an antilipolytic agent to decrease plasma NEFA concentrations or the same volume of water (200 mL/h), concomitant with partial feed restriction. From 0 to 74 h of each experimental period, cows were feed-restricted to 33% of the ad libitum intake recorded during the prior 5 d. An ivGTT (0.25 g/kg of BW of glucose i.v.) and an ivBAC (4 nmol/kg of BW of isoproterenol hydrochloride, i.v.) were performed at 48 and 72 h, respectively. Intake was 24.1, 8.2, 8.0, and 8.0 kg of dry matter/d before restriction, on d 1, 2 and 3, respectively. Nicotinic acid decreased plasma NEFA and increased insulin and glucose concentrations during feed restriction. Nicotinic acid also led to greater glucose and insulin response areas under the curve during ivGTT [glucose: 6,562 vs. 5,056 (mg/dL)×180 min; insulin: 6,042 vs. 2,502 (μIU/mL)×180 min] and ivBAC [glucose: 535 vs. 240 (mg/dL)×120 min; insulin: 1,283 vs. 222 (μIU/mL)×120 min], and enhanced NEFA area under the curve during ivBAC [45,521 vs. 22,862 (μEq/L)×120 min]. Milk, fat, and protein yields (29.1, 1.2, and 0.93 kg on d-2, respectively) decreased to 17.9, 0.81, and 0.56 kg for control, and 11.5, 0.54, and 0.39 kg for NA on d 3, respectively. Nicotinic acid may have decreased production by inhibiting the supply of NEFA for energy and milk fat synthesis. Milk urea nitrogen was increased by NA on d 2 (12.8 vs. 19.1 mg/dL) and d 3 (11.6 vs. 17.8 mg/dL), probably due to a greater reliance on mobilized amino acids. Somatic cell count was increased by NA on d 3 (187 vs. 848 ×1,000 cells/mL). Patterns of glucose and insulin concentration observed during 74 h of NA infusion reflect a state of insulin resistance, which contrasts with shorterterm responses in nonlactating cows. Data suggest that long-term supraphysiological infusion of NA affected intermediary metabolism beyond antilipolysis and did not inhibit acute lipolytic stimuli of ivBAC. [ABSTRACT FROM AUTHOR]

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤2.50) versus higher (≥2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos by d 7 after AI in cows that lost more BW from the first to third week postpartum. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of a rumen-protected niacin product (RPN; 65% nicotinic acid; NiaShure, Balchem Corp., New Hampton, NY) on lipid metabolism, oxidative stress, and performance of transition dairy cows. Thirty nonlactating multiparous Holstein cows in late gestation were paired according to expected calving date and randomly assigned to 12 g/ cow per day of RPN product or to an unsupplemented control (CON) diet. Treatment diets were fed from 21 d before expected calving through 21 d after parturition. Blood samples were taken on d -21, -14, -7, 1, 7, 14, and 21 relative to calving for plasma nonesterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, and superoxide dismutase (SOD) analyses. Liver samples were taken by biopsy on d 1 and 21 relative to calving for triglyceride (TG) analysis. Data were analyzed for a randomized complete block design with repeated measures. Pre- and postpartum dry matter intake, milk yield, and protein were unaffected by treatment. Milk fat percentage (5.08 vs. 4.44%) and somatic cell score (3.93 vs. 2.48) were reduced for RPN. Treatment x time interactions were observed for energy-corrected milk (ECM) and fat-corrected milk (FCM) yields; RPN reduced ECM and FCM yields by 8.5 and 8.9 kg/ cow per day, respectively, in the first week of lactation. Although body weight and condition score decreased during the experimental period, no differences due to treatment were observed. However, calculated postpartum energy balance tended to be improved for RPN because of the reduction in ECM yield. Time and treatment x time effects were observed for plasma NEFA. On d 1 postpartum, NEFA reached 1,138 ± 80 µEq/L for CON compared with 698 ± 80 µEq/L for RPN. Cows supplemented with RPN tended to have lower plasma NEFA concentrations than CON cows on d 7 and 14 postpartum. Plasma BHBA, glucose, and SOD and liver TG concentrations were unaffected by treatment. In conclusion, supplementation with 12 g/cow per day of the RPN product provided a bioavailable source of niacin that modified lipid metabolism but did not affect milk yield over the first 3 wk of lactation or oxidative stress of transition dairy cows. [ABSTRACT FROM AUTHOR]

Some studies have reported improved reproductive performance with dietary fat supplementation. This study examined effects of fatty acids with different lengths, or desaturation, or both, on metabolism of estradiol (E2) and progesterone (P4) in bovine liver slice incubations (experiments 1 and 2) and in vivo (experiment 3). In experiment 1, effects of fatty acids C16:0 (palmitic acid), C16:1 (palmitoleic acid), C18:1 (oleic acid), and C18:3 (linolenic acid) were evaluated at 30, 100, and 300 μM on P4 and E2 metabolism in vitro. In experiment 2, stearic acid (C18:0) and C18:3 were evaluated in the same incubation conditions. In experiment 1, all of the fatty acids had some significant inhibitory effect on metabolism of P4, E2, or both (300 μM C16:0 on E2; 100 μM C16:1 on E2; 300 μM C16:1 on both P4 and E2; 300 μM C18:1 on P4; and 100 and 300 μM C18:3 on both P4 and E2). In experiment 2, C18:3 (100 and 300 μM) but not C18:0 decreased P4 and E2 metabolism. Overall, the most profound increase (~60%) in half-life of P4 and E2 was observed with incubations of 300 μM C18:3 in both in vitro experiments. Based on these in vitro results, in experiment 3 linseed oil (rich in C18:3) was supplemented into the abomasum and acute effects on metabolism of E2 and P4 were evaluated. Cows (n = 4) had endogenous E2 and P4 minimized (corpus luteum regressed, follicles aspirated) before receiving continuous intravenous infusion of E2 and P4 to analyze metabolic clearance rate for these hormones during abomasal infusion of saline (control) or 70 mL of linseed oil every 4 h for 28 h. Linseed oil infusion increased C18:3 in plasma by 46%; however, metabolic clearance rate for E2 and P4 were similar for control cows compared with linseed-treated cows. Thus, in vitro experiments indicated that E2 and P4 metabolism can be inhibited by high concentrations of C18:3. Nevertheless, in vivo, linseed oil did not acutely inhibit E2 and P4 metabolism, perhaps because insufficient C18:3 concentrations (increased to ~8 μM) were achieved. Further research is needed to determine the mechanism(s) of fatty acid inhibition of P4 and E2 metabolism and to discover practical methods to mimic this effect in vivo. [ABSTRACT FROM AUTHOR]

The objective was to determine the effects of abomasal infusion of linseed oil on liver triglyceride (TG) accumulation and adipose tissue lipolysis during an experimental protocol for induction of fatty liver. Eight nonpregnant, nonlactating Holstein cows were randomly assigned to treatments in a replicated 4 x 4 Latin square design. Treatments were abomasal infusion of water (W), tallow (T), linseed oil (LO), or half linseed oil and half tallow (LOT) at a rate of 0.56 g/kg of body weight per day. Each experimental period consisted of a 4-d fast concurrent with administration of treatments into the abomasum in 6 equal doses per day (every 4 h). Cows were fed ad libitum for 24 d between periods of fasting and lipid infusion. Infusion of linseed oil (LO and LOT) increased a-linolenic acid (C18:3n-3) content in serum (12.2, 10.4, 4.2, and 4.6 g/100 g of fatty acids for LO, LOT, T, and W, respectively), but not in the nonesterified fatty acid (NEFA) fraction of plasma. Treatments had no effect on plasma NEFA concentrations. Abomasal infusion of lipid increased in vitro stimulated lipolysis in subcutaneous adipose tissue, compared with W (4,294, 3,809, 4,231, and 3,293 nmol of glycerol released x g-1 tissue x 2 h-1 for LO, LOT, T, and W, respectively), but there was no difference between fat sources. Hepatic TG accumulation over 4-d fast was 2.52, 2.60, 2.64, and 2.09 ± 0.75 μg of TG/μg of DNA for W, LO, LOT, and T, respectively, which did not differ. Abomasal infusion of LO did not reduce liver TG accumulation, plasma NEFA concentration, or alter in vitro adipose tissue lipolysis when compared with T. These results contrast with a previous study involving i.v. infusion of lipid emulsion derived from LO. Discrepancies might be explained by the use of different administration routes and a relatively modest induction of liver TG accumulation in the current experiment. [ABSTRACT FROM AUTHOR]

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results. [ABSTRACT FROM AUTHOR]

Holstein cows (n = 781) in a commercial dairy herd were used in a randomized design to evaluate 2 dry period (DP) management strategies on milk production, milk components, milk quality, colostrum quality, and incidence of metabolic disorders. Cows were randomly assigned to a traditional 55 d (T) or shortened 34 d (S) DP. Cows assigned to T were fed a low-energy diet until 34 d before expected calving at which time all cows were fed a moderate-energy transition diet until calving. Postpartum, cows assigned to T produced more milk and tended to produce more solids-corrected milk than cows on S. Treatment differences in milk and solids- corrected milk yield were accounted for by cows in their second lactation. Milk fat percentage did not differ between treatments, but milk protein percentage was greater for cows assigned to S. Colostrum quality measured as IgG concentration did not differ between management strategies. Somatic cell score and cases of mastitis were not affected by management strategy. There was a tendency for prepartum nonesterified fatty acid (NEFA) to be lower for cows assigned to T compared with S. However, postpartum, cows assigned to S had significantly lower NEFA concentrations than those assigned to T. The incidences of ketosis, retained placenta, displaced abomasum, and metritis did not differ between treatments. Postpartum energy balance, as indicated by plasma NEFA, may have been improved for cows assigned to S; there was no detectable effect on animal health. [ABSTRACT FROM AUTHOR]

The objective was to study the effects of abomasal infusion of linseed oil, a source rich in n-3 C18:3, on whole-body response to insulin (experiment 1) and on insulin antilipolytic effects during feed restriction (experiment 2). In experiment 1, eight nonlactating, nongestating cows were assigned to a crossover design, fed to meet maintenance requirements, and infused abomasally with either linseed oil (LIN) or tallow (TAL) at a rate of 0.54 g/kg of body weight per d for 5.5 d. Infusions were performed every 8 h during the first 3 d of each period and every 4 h thereafter. Intravenous glucose tolerance tests (IVGTT) were performed on d 5 of each period, followed by i.v. insulin challenges (IC) 12 h later. In experiment 2, six nonlactating, nongestating cows were assigned to a replicated 3 x 3 Latin square design. The experimental protocol included a water (WTR) treatment and feeding was suspended on d 3, leading to 50 and 62 h of feed restriction before IVGTT and IC, respectively. Clearance of glucose during IVGTT and IC was not affected by treatments in either experiment. However, LIN had an insulin sensitizing effect in experiment 1, because a lower insulin concentration led to the same clearance of glucose as TAL. In experiment 1, plasma nonesterified fatty acid (NEFA) concentration was low, reflecting a postprandial state, but NEFA was greater for LIN than TAL during IVGTT (108 vs. 88 ± 4 µEq/L) and IC (133 vs. 83 ± 9 µEq/L). In experiment 2, insulin concentrations during IVGTT did not differ across treatments. Basal plasma NEFA concentration before IVGTT tended to be greater for LIN than for TAL (612 vs. 508 µEq/L). Plasma NEFA clearance rate during IVGTT was greater for LIN than for TAL (2.8 vs. 2.5%/min), leading to a shorter time to reach half NEFA concentration (25 vs. 29 min) and greater absolute value of NEFA response area under the curve [AUC; -64,150 vs. -46,402 (µEq/L) x 180 mini. Data suggest that LIN enhanced the antilipolytic effects of insulin. Yet, other factors could have been involved because plasma NEFA concentration before IVGTT was 104 µEq/L greater for LIN than TAL for unknown reasons. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate if supplementing rumen-protected choline (RPC; Reashure, Balchem Encapsulates, Slate Hill, NY) could prevent or alleviate fatty liver in dairy cattle. The first experiment evaluated the effect of supplementing RPC on hepatic triacylglycerol (TAG) accumulation during fatty liver induction. Twenty-four dry cows between 45 to 60 d prepartum were paired by body weight (BW) and body condition score (BCS) and randomly assigned to control or supplementation with 15 g of choline as RPC/d. From d 0 to 6, before treatment application, all cows were fed 1.4 kg/d of concentrate and forage ad libitum. Samples of blood and liver, obtained during the pretreatment period, were used for covariate adjustment of blood metabolites and liver composition data. During fatty liver induction (d 7 to 17), cows were fed 1.4 kg/d of concentrate with or without supplementation with RPC, and forage intake was restricted, so cows consumed 30% of the total energy requirements for pregnancy and maintenance. Supplementation with RPC during fatty liver induction did not affect plasma glucose and plasma β-hydroxybutyrate (BHBA) concentration but did decrease plasma nonesterified fatty acid (NEFA; 703 vs. 562 µEq/L, SE = 40) and liver TAG accumulation (16.7 vs. 9.3 µg/µg of DNA, SE = 2.0). In the second experiment, we evaluated the effect of supplementing RPC on the clearance of liver TAG when cows were fed ad libitum after the induction of fatty liver by feed restriction. Twenty-eight cows between 45 and 60 d prepartum were paired according to BCS and BW and assigned to treatments. Fatty liver was induced by feeding 1.4 kg/ d of concentrate (without RPC) and restricting forage intake, so cows consumed 30% of maintenance and pregnancy energy requirements for 10 d. From d 11 to 16, after feed restriction, cows were fed forage ad libitum and 1.4 kg/d of concentrate with or without RPC. Treatments were not applied during fatty liver induction; however, following feed restriction, liver for cows assigned to control and RPC treatments contained 6.8 and 12.7 µg of TAG/µg of DNA, respectively. Measurements obtained before treatment served as covariates for statistical analysis. During the depletion phase, plasma glucose, BHBA, and NEFA were not affected by treatment. Liver TAG, expressed as covariate adjusted means, was 6.0 and 4.9 µg/µg of DNA (SE = 0.4) on d 13, and 5.0 and 1.5 µg/µg of DNA (SE = 0.9) on d 16 for control and RPC, respectively. Rumen-protected choline can prevent and possibly alleviate fatty liver induced by feed restriction. [ABSTRACT FROM AUTHOR]

Forty-eight Holstein cows were used in a randomized block design to evaluate different dry period lengths and prepartum milking frequencies (MF) on subsequent milk production, milk composition, solids-corrected milk production, dry matter intake (DMI), and energy balance. Lactating cows, milked 2 times/d, began a 7-d covariate period 35 d prior to the expected calving date. Cows were milked 0 times/d (0x), 1 time/d (1x), and 4 times/d (4x) for the last 28 d of gestation. If milk production decreased to less than 0.5 kg/milking or 1 kg/d, milking via machine ceased; however, teat stimulation continued 1 or 4 times/ d according to the treatment assignment. All cows were milked 2 times/d postpartum (wk 1 to 10). Prepartum DMI tended to be greater for lx and 4x compared with 0x. Prepartum, cows milked lx produced 17% less milk than cows milked 4x (5.9 and 7.1 kg/d, respectively). There were no differences in prepartum and postpartum body condition scores, body weights, and DMI. Postpartum milk production by cows following their third or greater gestation was greater for 0x and 4x compared with 1x. Postpartum milk production by cows following their second gestation was significantly decreased with increased MF (0x vs. 1x and 4x). Regardless of parity, postpartum solids-corrected milk was greater for 0x compared with 1x and 4x. Postpartum fat yield was greater for 0x vs. 4x, with lx being intermediate. Postpartum protein yield was greater for 0x vs. 4x, whereas 0x tended to have greater protein yield than lx. Postpartum energy balance was greater for 1x and 4x relative to 0x. Continuous milking (1x and 4x) resulted in a loss of milk production in the subsequent lactation for cows following their second gestation; however, for cows following their third or greater gestation, increasing the MF from 1x to 4x in the last 28 d of gestation alleviated the loss in milk production. [ABSTRACT FROM AUTHOR]

Effects of dietary energy density during late gestation and early lactation on metabolic status of periparturient cows were studied. Four weeks before expected calving, animals were fed a low (DL; 1.58 Mcal of NEL/ kg) or high energy density diet (DH; 1.70 Mcal of NEL/ kg). After calving, half of the cows from each prepartum treatment were assigned to a low (L; 1.57 Mcal of NEL/ kg) or high energy density diet (H; 1.63 Mcal of NEL/kg) until d 20 postpartum. After d 20, all animals were fed H until d 70. Animals fed DH had a more positive energy balance during the prepartum period. Animals fed DH had higher plasma concentrations of glucose and insulin and lower concentrations of plasma nonesterified fatty acid (NEFA) on d -7 relative to calving compared with animals fed DL. No differences in blood concentrations of metabolites, insulin and liver triglycerides (TG) content were observed on d 1. Liver TG content at d 1 and 21 were more related to magnitude of change in energy intake prepartum than to energy intake in the last week of gestation. Cows fed H had higher concentrations of plasma glucose and insulin, but similar plasma NEFA during the postpartum period compared with cows fed L. Plasma concentrations of β-hydroxybutyrate (BHBA) and liver TG content on d 21 were 46 and 30% lower, respectively, for cows fed H compared with cows fed L. Interactions between prepartum and postpartum treatments indicated that negative effects of delaying higher concentrate feeding until d 21 postpartum can be partially offset by increasing concentrate in the diet before calving. Cows fed L had a higher increase in white line hemorrhage scores between prepartum and 10 wk postpartum compared with cows fed H. Energy density of prepartum diets had a minor influence on metabolic status of cows postpartum. A more favorable metabolic profile occurs when increasing the concentrate content of the diet immediately postpartum compared with delaying the increase until d 21 postpartum. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined the impact of corn silage particle length on rumen function and milk fat production of lactating dairy cows fed supplemental tallow in diets with processed high grain-yielding corn silage as the only forage source. Methodology of the study; Results and discussion on the study; Conclusions.

Compares the effects of dietary energy density during late gestation and early lactation on lactation performance and ruminal parameters of dairy cows. Prepartum performance and ruminal parameters; Parity interactions; Effects of increasing prepartum diet energy density on overall postpartum performance.

The objectives were to determine effects of 12 hourly infusions of different quantities of nicotinic acid (NA) on plasma nonesterified fatty acid (NEFA; experiment 1) and whether longer (108 h) continuous infusions of NA could induce sustained reductions of plasma NEFA (experiment 2) in nonlactating, nongestating Holstein cows that were feed restricted. Experiment 1 was a 5×5 Latin square with 6-d periods and 9 recovery days between each period. Each period consisted of 5 d of partial feed restriction to increase plasma NEFA concentration. Treatments were abomasal infusions of 0, 0.25, 0.5, 1, or 3 mg of NA/h per kilogram of body weight (BW), infused as hourly boluses for 12 h, starting 4 d after initiation of partial feed restriction. Plasma NEFA was decreased for the highest dose: from 448 μEq/L to 138±75 μEq/L at 1 h after the first bolus of 3mg of NA/h per kilogram of BW. This initial reduction in plasma NEFA concentration was followed by an increase in concentration at 2, 3, and 4 h relative to initiation of infusions. Plasma NEFA then decreased to 243 μEq/L 6h after initiation of treatments and remained low until termination of infusions. A rebound in plasma NEFA concentration occurred at 3 and 4 h after termination of infusion for cows that received 3 mg of NA/h per kilogram of BW. Experiment 2 was a 5×5 Latin square with 7-d periods and 9 recovery days between each period. Each period consisted of 5 d of partial feed restriction to increase plasma NEFA concentration. Treatments were continuous abomasal infusion of 0, 0.5, 1, or 3 mg of free NA/h per kilogram of BW for 4.5 d starting at feed restriction or 0.5 mg of NA/h per kilogram of BW infused directly into the rumen in a form protected from microbial degradation. The ruminal administration of protected NA was initiated 2 d before abomasal infusions and initiation of feed restriction to establish steady postruminal delivery of NA by start of abomasal infusions. Plasma NEFA was approximately 70 μEq/L before initiation of feed restriction and increased to 509, 587, 442, 850, and 108 μEq/L at 4.5 d for cows that received 0, 0.5 (protected NA), 0.5 (free NA), 1, and 3 mg of NA/h per kilogram of BW, respectively. An antilipolytic response was achieved with the highest abomasal dose, which maintained plasma NEFA concentration lower than the control group. An increase in plasma NEFA concentration was observed after termination of infusions for cows that received 1 and 3 mg of NA/h per kilogram of BW. Plasma NEFA was 1,900 μEq/L at 4h after termination of infusion for cows receiving 1 mg of NA/h per kilogram of BW and 1,360 μEq/L at 5h after termination of infusion for cows receiving 3 mg of NA/h per kilogram of BW. In nongestating, nonlactating cows it is unlikely that a dose of NA exists that will reduce plasma NEFA concentration and prevent the rebound that occurs following termination of NA administration., (Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Reproductive performance of dairy cattle has been related to a wide variety of indicators of energy status, e.g., extent of negative energy balance, time of energy balance nadir, body weight loss, body condition score, and body condition score loss. Energy balance begins to decrease during the last few weeks prior to calving primarily due to a 30-35% reduction in feed intake. Cows typically remain in negative energy balance for five to seven weeks postpartum. Nutritional strategies to improve energy balance during the transition period include fat supplementation and feeding additional nonfiber carbohydrate. Unfortunately, neither approach is likely to markedly enhance energy status, although fat supplementation may increase reproductive efficiency independent of any effect on energy balance. Alternative management strategies may be required to improve fertility of dairy cows. Shortening or eliminating the dry period may improve energy status of dairy cows and increase reproductive efficiency. Shortening or eliminating the dry period may enhance dry matter intake during the transition period, decrease milk energy output, or both. A preliminary study using small animal numbers indicated that reducing dry period length to 28 or 0 days may decreases days to first ovulation, increase first service conception rate, and decrease days open. A follow-up study employing large animal numbers confirmed that reducing dry period length from 55 to 34 days can decrease days to first ovulation and decrease the percentage of anovular cows. The reduction in days open was greater for older cows than second parity cows. The reduction in days open was not related to effects of treatment on milk yield. Shortening or eliminating the dry period may be a more successful approach to improving reproductive efficiency than diet manipulation.

Sixty-five Holstein cows were used to evaluate management schemes involving altered dry period (DP) lengths on subsequent milk production, energy balance (EB), and metabolic variables. Cows were assigned to one of 3 treatments: traditional 56-d DP (fed a low-energy diet from -56 to -29 d and a moderate energy diet from -28 d to parturition; T), 28-d DP (continuously fed a high energy diet; S), and no planned DP (continuously fed a high energy diet; N). Prepartum DM intake (DMI), measured from 56 d prepartum through parturition, was lower for cows on the T treatment than for cows on the S treatment and was higher for cows on the N treatment than for cows on the S treatment. There were no differences in prepartum plasma glucose, and beta-hydroxybutryric acid; there was a treatment by time interaction for prepartum plasma nonesterified fatty acid (NEFA). There was no difference in prepartum liver triglyceride (TG); postpartum liver TG was decreased for cows on the N treatment compared with cows on the S treatment, but was similar for cows on the T and S treatments. Postpartum NEFA was similar between cows on the T and S treatments, but was greater for cows on the S treatment than for cows on the N treatment. Postpartum glucose was greater for cows on the N treatment compared with cows on the S treatment and tended to be greater for cows on the S treatment than for cows on the T treatment. There was no difference in postpartum solids-corrected milk (SCM) production or DMI by cows on the T vs. S treatment. However, there was a tendency toward lower postpartum SCM production by cows on the N vs. S treatment and a tendency for greater postpartum DMI by cows on the N vs. S treatment. Postpartum EB was greater for cows on the S vs. T treatment and the N vs. S treatment. In general, T and S management schemes had similar effects on DMI, SCM, and metabolic variables in the first 70 d of the subsequent lactation. Eliminating the DP improved energy and metabolic status.

The objectives of this study were to develop and validate a model for predicting dry matter intake (DMI) of Holsteins during the prefresh transition period. The original database (ODB) for model development was established by compiling parity, body condition score (BCS), and DMI data during the final 3 wk of gestation from 366 Holsteins fed 24 different diets that were used in eight experiments conducted at three universities. For model validation, a validation database (VDB) was established by compiling data from 333 prefresh transition Holsteins fed 25 different diets that were used in eight experiments conducted at five universities. Dry matter intake during the prefresh transition period was fitted to an exponential function: DMI(t) = a + pe(kt), where DMI(t) = DMI as a percentage of body weight (BW) at time t, a = asymptotic intercept at time--infinity, p = change in intake (kg) from the asymptotic intercept until parturition, k = rate constant influencing the shape of the curve, and t = day relative to parturition expressed as days pregnant--280. The model developed from the ODB predicted DMI of heifers in the VDB with satisfactory accuracy and precision. However, this was not true for cows, probably due to differences in BCS of cows and diets fed to cows from the two data sets. When a subset of cows was selected from each data set that had similar BCS (> 4.0) and were fed similar diets, accuracy and precision of the model predicting DMI was improved. Finally, both databases were combined to develop final models for predicting DMI of heifers and cows. Proposed models for predicting mean daily DMI of heifers and cows during the prefresh transition period were DMI(t) = 1.713-0.688e(0.344t) (R2 = 0.96) and DMI(t) = 1.979-0.756e(0.154t) (R2 = 0.97), respectively. Adjustment factors for animal and dietary factors were generated to demonstrate the plausibility of adaptive fitting of the prediction. The regression coefficients of prediction models (a, p, and k) were affected by BCS and dietary organic macronutrient concentrations.