Conjugated linoleic acid increases in milk when cows fed fish meal and extruded soybeans for an extended period of time

The objective of this study was to determine the effect of feeding a conjugated linoleic acid (CLA) stimulating diet for an extended period of time on milk cis-9, trans-11 CLA and vaccenic acid (VA) concentrations. Twenty cows (16 Holstein and 4 Brown Swiss) were divided into 2 groups (n = 10 per treatment) for a 10-wk study. Cows in group 1 were fed a traditional corn-soybean-basal diet (control), while those in group 2 were fed a blend of 0.5% fish oil from fish meal and 2% soybean oil from extruded soybeans (FMESB) to achieve higher milk fat cis-9, trans-11 CLA and VA. Diets were formulated to contain 18% CP and were composed (dry matter basis) of 50% concentrate mix, 25% corn silage, and 25% alfalfa hay. Dry matter intake was not affected by diet. Milk production increased in cows fed the FMESB diet. Milk fat and milk protein percentages decreased with the FMESB diet; however, milk fat and protein yields were not affected by treatments. Milk fat cis-9, trans-11 CLA and VA concentration (g/100 of fatty acids) and yield (g/d) were 2.5-fold greater for cows fed the FMESB diet over the 10 wk of fat supplementation. For cows fed the FMESB diet, contents of milk fat cis-9, trans-11 CLA and VA gradually increased from the first week of fat supplementation, reached the highest concentrations in wk 3, then gradually decreased during wk 4 and 5 and then remained relatively constant until wk 10. The concentration of cis-9, trans-11 CLA and VA from the control diet was relatively constant over the 10 wk of fat supplementation. Concentrations of cis-9, trans-11 CLA and VA in milk fat can be increased within a week by feeding a blend of fish meal and extruded soybeans, and that increase remains relatively constant after wk 5 of fat supplementation.     

Addition of straw to the early-lactation diet: Effects on feed intake,milk yield,and subclinical ketosis in Holstein cows

This study evaluated feed intake, milk yield, and subclinical ketosis in dairy cows in early lactation fed 2 different diets postpartum. Cows are typically offered a high-energy ration immediately after calving. We compared a conventional high-energy total mixed ration (TMR) with a transition ration that contained chopped straw. We predicted that adding chopped straw would increase dry matter intake, milk production, and indicators of energy metabolism during the first 3 wk of lactation compared to cows fed a conventional high-energy TMR. We also predicted that carryover effects would be likely for at least 2 wk after treatment ended. A total of 68 mixed-age Holstein cows were enrolled in the study 3 wk before their expected calving. All cows were managed on a single high-forage diet during the dry period. At calving, cows were allocated to 1 of the 2 diets: half to the conventional high-energy TMR (CTMR; n = 34; net energy for lactation = 1.61 Mcal/kg; neutral detergent fiber = 31.7%), and the other half to a high-forage TMR containing chopped wheat straw, equivalent to 4.27% dry matter (STMR; n = 34; net energy for lactation = 1.59 Mcal/kg; neutral detergent fiber = 33.7%) for 3 wk after calving. Cows on STMR were then shifted to CTMR for the next 2 wk to study short-term residual effects on the performance of cows. Treatments were balanced for parity, body condition score, and body weight. Feed intake was measured daily from 2 wk before to 5 wk after calving using automatic feed bins. Blood was sampled twice weekly from 2 wk before to 5 wk after calving, and β-hydroxybutyrate and glucose were measured in serum samples. Subclinical ketosis was identified using a threshold of β-hydroxybutyrate ≥1.0 mmol/L in wk 1 after calving and ≥1.2 mmol/L in wk 2 to 5 after calving. Cows were milked twice daily, and weekly samples (composite samples of morning and afternoon milkings) were analyzed to determine total solids, fat, protein, lactose, and somatic cell count. Data were analyzed in 2 separate periods: the treatment phase (wk +1, +2, and +3) and the post-treatment phase (wk +4 and +5). The addition of straw to the TMR negatively affected the dry matter intake of STMR cows during wk 2 and 3 of lactation. Daily milk yield during the first 5 wk of lactation was lower in STMR cows than in CTMR cows. Concentrations of β-hydroxybutyrate were higher in CTMR cows than in STMR cows during wk 1, but this effect was reversed during wk 2 and 3 of lactation. By 21 d in milk, STMR cows had a greater risk of developing subclinical ketosis than CTMR cows. Adding chopped wheat straw to the TMR during the first 21 d after calving lowered dry matter intake and provided no metabolic or production benefits to lactating dairy cattle.     

The effect of dietary rumen-protected trans-10,cis-12 conjugated linoleic acid or a milk fat-depressing diet on energy metabolism,inflammation, and oxidative stress of dairy cows in early lactation

The objective of this study was to determine the effects of milk fat depression induced by supplementing conjugated linoleic acid (CLA; trans-10,cis-12 and cis-9,trans-11 CLA) or feeding a higher starch and oil-containing diet (HSO) on metabolic changes in dairy cows after calving. The main hypothesis was that the 2 strategies to decrease milk fat yield could have different effects on performance, energy balance (EB), and inflammatory status in early lactation. Thirty-three Nordic Red dairy cows were used in a randomized block design from 1 to 112 d of lactation and fed one of the following treatments: control (CON), CLA-supplemented diet, or HSO diet. Dry matter intake and milk yield were measured daily whereas milk composition was measured weekly throughout the experiment. Nutrient digestibility, EB, and plasma hormones and metabolites were measured at 3, 7, 11, and 15 wk of lactation in respiration chambers. The HSO diet led to lower intakes of dry matter, neutral detergent fiber, and gross energy compared with CON and CLA diets. The CLA diet and especially the HSO diet resulted in lower energy-corrected milk yield during the first 7 wk of lactation than those fed CON. The EB was numerically higher for HSO and CLA diets compared with CON at wk 3 and 7. Plasma glucose concentration was higher by the CLA diet at wk 3 and by the HSO diet from wk 3 to 15 compared with CON. Plasma nonesterified fatty acids were higher at wk 3 in the CON group (indicating more lipid mobilization) but decreased thereafter to similar levels with the other groups. The HSO-fed cows had higher plasma ceruloplasmin, paraoxonase, and total bilirubin concentrations in the entire experiment and showed the highest levels of reactive oxygen metabolites. These results suggest an increased inflammatory and oxidative stress state in the HSO cows and probably different regulation of the innate immune system. This study provides evidence that milk fat depression induced by feeding HSO (as well as CLA) decreased milk fat secretion and improved EB compared with CON in early lactation. The increase in plasma glucose and paraoxonase levels with the HSO diet may imply a better ability of the liver to cope with the metabolic demand after parturition. However, the negative effect of HSO on feed intake, and the indication of increased inflammatory and oxidative stress warrant further studies before the HSO feeding strategy could be supported as an alternative to improve EB in early lactation.     

Production and metabolic responses of periparturient Holstein cows to dietary conjugated linoleic acid and trans-octadecenoic acids

Thirty-eight multiparous Holstein cows were utilized in a completely randomized design to examine the effect of feeding calcium salts of conjugated linoleic acid (CLA) and trans-octadecenoic acids (trans-C18:1) on animal performance and lipid and glucose metabolism during the transition to lactation. Dietary treatments were initiated approximately 28 d prior to expected calving dates and continued through d 49 postpartum. Prepartum treatments consisted of 1) a basal diet (Control), 2) basal diet + 150 g/d of CLA mix (CLA), and 3) basal diet + 150 g/d of trans-C18:1 mix (TRANS). Amounts of calcium salts of CLA and trans-C18:1 mixes were adjusted to 225 g/d during the 49-d postpartum treatment period. All diets were offered as a total mixed ration. Prepartum fat supplementation had no detectable effects on dry matter intake, body weight, or body condition score. After parturition, cows in the TRANS group consumed less dry matter at wk 4, 5, and 6 of lactation than did cows in the control group. Cows fed the trans-C18:1 supplement were in a more severe negative energy balance than those fed the control diet at 1 wk of lactation. Periparturient fat supplementation had no detectable effects on milk yield during wk 1 to 7 of lactation. Milk fat was not affected during wk 1 to 4, but was reduced after wk 4 of lactation by dietary CLA. Feeding calcium salts of CLA decreased short- to medium-chain fatty acid (C4 to C14) concentrations and increased both linoleic and linolenic acid concentrations in milk fat. Concentrations of nonesterified fatty acids and beta-hydroxybutyric acid in blood were greater in cows fed the CLA-supplemented diet than in those fed the control diet at 1 wk of lactation. In spite of small numerical tendencies, hepatic lipid and triacylglycerol concentrations did not vary significantly among dietary treatments. Periparturient fat supplementation had no detectable effects on plasma glucose and insulin concentrations. Steady-state concentrations of hepatic mRNA encoding pyruvate carboxylase and phosphoenolpyruvate carboxykinase were greater for the TRANS treatment group than the control and CLA groups. Results indicate that dietary CLA and trans-C18:1 fatty acids may affect lipid and glucose metabolism in early postpartum Holstein cows through distinct mechanisms.     

Genetic correlation between days until start of luteal activity and milk yield, energy balance, and live weights

The objective of this study was to estimate genetic correlations among fertility and measures of energy balance, dry matter intake, and live weight (change). Data from 622 first lactation cows (fed ad libitum a complete ration) included milk, fat, and protein yields; energy balance; and live weights for the first 15 wk of lactation. For a subset of the heifers (n = 329) and 91 contemporaries, progesterone values were measured in the milk twice a week and were used to determine the interval between calving and first luteal activity (CLA). To obtain correlations, a series of bivariate animal model analyses was performed. The heritabilities for CLA and energy balance were 0.16 and 0.33, respectively. Heritability for live weights were 0.48 to 0.61 and for live weight changes were 0.17 and 0.24. Genetic correlations of CLA with milk, fat, and protein yields were high and unfavorable (0.51, 0.65, and 0.48, respectively), whereas energy balance, live weight during lactation, and weight gain all had a favorable genetic correlation with CLA (range -0.40 to -0.80). When genetic variation in CLA was adjusted genetically for milk, fat, and protein yields, the correlation with feed intake became -0.49 and explained approximately half of the genetic variance in CLA. This supports that increasing genetic merit for feed intake, at a common genetic merit for yield, improved CLA. Furthermore, selection on an index including protein yield and energy balance or live weight (change) allowed 0.71 to 0.80 of the maximum response in protein yield without a negative selection effect on CLA.     

Effect of safflower oil, flaxseed oil, monensin, and vitamin E on concentration of conjugated linoleic acid in bovine milk fat

Conjugated linoleic acid (CLA) refers to a mixture of conjugated octadecadienoic acids of predominantly ruminant origin. The main isomer in bovine milk fat is the cis-9, trans-11 CLA. Interest in CLA increased after the discovery of its health-promoting properties, including potent anticarcinogenic activity. Two experiments were conducted to evaluate dietary strategies aimed at increasing the concentration of CLA in bovine milk fat. Both experiments were organized as a randomized complete block design with a repeated measures treatment structure. In Experiment 1, 28 Holstein cows received either a control diet or one of 3 treatments for a period of 2 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a dry matter (DM) basis, fed as a total mixed ration (TMR). The concentrate was partially replaced in the treatment groups with 24 ppm of monensin (MON), 6% of DM safflower oil (SAFF), or 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M). Average cis-9, trans-11 CLA levels in milk fat after 2 wk of feeding were 0.45, 0.52, 3.36, and 5.15% of total fatty acids for control, MON, SAFF, and SAFF/M, respectively. In Experiment 2, 62 Holstein cows received either a control diet or one of 5 treatment diets for a period of 9 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a DM basis, fed as a TMR. The concentrate was partially replaced in the treatment groups with 6% of DM safflower oil (SAFF), 6% of DM safflower oil plus 150 IU of vitamin E/kg of DM (SAFF/E), 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M), 6% of DM safflower oil plus 24 ppm of monensin plus 150 IU of vitamin E/kg of DM (SAFF/ME), or 6% of DM flaxseed oil plus 150 IU of vitamin E/kg of DM (FLAX/E). Average cis-9, trans-11 CLA levels during the treatment period were 0.68, 4.12, 3.48, 4.55, 4.75, and 2.80% of total fatty acids for control, SAFF, SAFF/E, SAFF/M, SAFF/ME, and FLAX/E, respectively. The combination of safflower oil with monensin was particularly effective at increasing milk fat CLA. The addition of vitamin E to the diet partially prevented the depression in milk fat associated with oilseed feeding, but had no significant effect on the concentration of CLA in milk.     

Effect of trans-10, cis-12 conjugated linoleic acid on performance, adipose depot weights, and liver weight in early-lactation dairy cows

In feeding practice, conjugated linoleic acid (CLA) supplements are used to decrease milk fat excretion in early-lactation dairy cows to save energy to counteract the physiological negative energy balance. The present study was conducted to examine the effects of CLA on energy metabolism, changes in liver weight, and the weight of different adipose depots during early lactation. Primiparous lactating German Holstein cows (n = 25) were divided into 5 groups and each group contained 5 animals. The experiment started 21 d prepartum and continued until 105 d in milk (DIM). Cows were slaughtered at 1, 42, and 105 DIM. The experiment was divided into a prepartum period (21 d prepartum until calving), period 1 (1 until 42 DIM), and period 2 (>42 until 105 DIM). In the prepartum period, all animals were housed together and fed the same diet with no CLA supplementation. At 1 DIM, an initial group, with no CLA supplementation, was slaughtered. The 20 remaining cows were assigned to 2 diets. One group received 100 g/d of a control fat supplement (CON; n = 10) and the other group 100 g/d of a CLA supplement (CLA; n = 10) from 1 DIM until slaughter. Five cows of each feeding group were slaughtered after 42 DIM and the remaining animals after 105 DIM. The CLA supplement contained approximately 10% each of trans-10, cis-12 CLA and cis-9, trans-11 CLA. During the slaughter process the empty body weight was recorded and the omental, mesenteric, retroperitoneal, and s.c. adipose depots, as well as the liver, were dissected and weighed. The CLA treatment decreased milk fat content in period 1 (14.1%). In period 2, milk fat content (25.4%) and yield (17.1%) were lower in the CLA group. No effect of CLA on milk yield was observed. The net energy intake, milk energy output, and the calculated energy balance remained unchanged by CLA supplementation. No effect of CLA on the weights of liver, omental, mesenteric, or s.c. adipose depots was observed when related to empty body weight. Liver weight increased with DIM, whereas the retroperitoneal adipose depot weight decreased at the same time. Compared with the initial group, the retroperitoneal adipose depot weight for control animals slaughtered after 42 DIM was decreased (47.7%); however, for the CLA group slaughtered after 42 DIM, a trend to a lower retroperitoneal adipose depot weight (34.0%) was observed. This suggests a CLA-induced deceleration of mobilization of the retroperitoneal adipose depot during the first 42 DIM.     

Increasing amounts of conjugated linoleic acid progressively reduces milk fat synthesis immediately postpartum

Mixed conjugated linoleic acid (CLA) isomers decrease milk fat synthesis during established lactation, but their ability to cause milk fat depression (MFD) immediately postpartum remains unclear. Multiparous Holstein cows (n = 19) were randomly assigned to 1 of 4 doses of rumen-protected (RP) CLA supplements (0, 200, 400, and 600 g/d); each dose provided equal amounts of fatty acids by replacing and balancing treatments with an RP supplement of palm fatty acid distallate. Doses provided a total of 468 g fatty acids/d and 0, 62, 125, or 187 g of mixed CLA isomers/d, respectively. The CLA supplement contained a variety of CLA isomers: 5.4% trans-8, cis-10; 6.3% cis-9, trans-11; 7.9% trans-10, cis-12; and 8.2% cis-11, trans-13 CLA. Each group received treatments from approximately -10 to 21 d relative to calving. To improve palatability and ensure complete consumption, doses were mixed with equal amounts of steam-flaked corn and dried molasses; one-half the supplement was fed at 0600 h, and the remaining supplement was fed at 1800 h. Milk yield and individual feed intake were recorded daily, and milk samples were obtained from each cow every 2nd day (at both milkings) starting on d 1 postpartum. There were no differences in dry matter intake (17.1 kg/d), milk yield (34.2 kg/d), protein content (3.74%), lactose content (4.61%), or yield of milk protein or lactose. The CLA supplementation decreased overall milk fat content in a dose-responsive manner (4.57, 3.97, 3.32, and 3.10, respectively), and milk fat yield displayed the same progressive decline. The dose-dependent decrease in milk fat content was evident during wk 1 and became highly significant during wk 2 and 3. The milk fat yield response pattern was similar, and by d 21, the highest RP-CLA supplement decreased milk fat content and yield by 49 and 56%, respectively. These data clearly indicate RP-CLA can markedly (40 to 50%) induce MFD immediately postpartum without negatively affecting other production parameters.     

Blood immunometabolic indices and polymorphonuclear neutrophil function in peripartum dairy cows are altered by level of dietary energy prepartum

Cows experience some degree of negative energy balance and immunosuppression around parturition, making them vulnerable to metabolic and infectious diseases. The effect of prepartum feeding of diets to meet (control, 1.34 Mcal/kg of dry matter) or exceed (overfed, 1.62 Mcal/kg of dry matter) dietary energy requirements was evaluated during the entire dry period (～45 d) on blood polymorphonuclear neutrophil function, blood metabolic and inflammatory indices, and milk production in Holstein cows. By design, dry matter intake in the overfed group (n=9) exceeded energy requirements during the prepartum period (-4 to -1 wk relative to parturition), resulting in greater energy balance when compared with the control group (n=10). Overfed cows were in more negative energy balance during wk 1 after calving than controls. No differences were observed in dry matter intake, milk yield, and milk composition between diets. Although nonesterified fatty acid concentration pre- (0.138 mEq/L) and postpartum (0.421 mEq/L) was not different between diets, blood insulin concentration was greater in overfed cows prepartum (16.7 μIU/mL) compared with controls pre- and postpartum (～3.25 μIU/mL). Among metabolic indicators, concentrations of urea (4.63 vs. 6.38 mmol/L), creatinine (100 vs. 118 μmol/L), and triacylglycerol (4.0 vs. 8.57 mg/dL) in overfed cows were lower prepartum than controls. Glucose was greater pre- (4.24 vs. 4.00 mmol/L) and postpartum (3.49 vs. 3.30 mmol/L) compared with control cows. Among liver function indicators, the concentration of bilirubin increased by 2 to 6 fold postpartum in control and overfed cows. Phagocytosis capacity of polymorphonuclear neutrophils was lower prepartum in overfed cows (32.7% vs. 46.5%); phagocytosis in the control group remained constant postpartum (50%) but it increased at d 7 in the overfed group to levels similar to controls (48.4%). Regardless of prepartum diet, parturition was characterized by an increase in nonesterified fatty acid and liver triacylglycerol, as well as blood indices of inflammation (ceruloplasmin and haptoglobin), oxidative stress (reactive oxygen metabolites), and liver injury (glutamic oxaloacetic transaminase). Concentrations of the antioxidant and anti-inflammatory compounds vitamin A, vitamin E, and β-carotene decreased after calving. For vitamin A, the decrease was observed in overfed cows (47.3 vs. 27.5 μg/100 mL). Overall, overfeeding energy and higher energy status prepartum led to the surge of insulin and had a transient effect on metabolism postpartum.     

Metabolism and lactation performance in dairy cows fed a diet containing rumen-protected fat during the last twelve weeks of gestation

Effects of dietary fat supplementation prepartum on liver lipids and metabolism in dairy cows are contradictory. Thus, we examined in 18 German Holstein cows (half-sib; first lactation 305-d milk yield >9,000 kg) whether dietary fat:carbohydrate ratio during the last trimester of gestation affects lipid metabolism and milk yield. The diets were formulated to be isoenergetic and isonitrogenous but differed in rumen-protected fat (FD; 28 and 46.5 g/kg of dry matter during far-off and close-up dry period; mainly C16:0 and C18:1) and starch concentration [carbohydrate diet (CD); 2.3 times as much starch as FD]. Diets were given ad libitum starting 12 wk before expected parturition. After parturition all cows were fed a single lactation diet ad libitum for 14 wk. With the FD treatment, dry matter intake was depressed prepartum, milk yield during first 4 wk of lactation was lower (36.9 vs. 41.0 kg/d), and postpartum energy balance during this period was more negative. During the first 4 wk, cows in the FD group had lower lactose percentage and yield but higher milk fat, whereas milk protein and fat yield as well as energy-corrected milk did not differ. Between wk 5 and 14, milk fat and milk protein percentage was lower in CD than in FD. Milk fat C14:0 was lower and C16:1 was higher in the FD group. For FD cows, plasma triacylglycerol, nonesterified fatty acids, and cholesterol concentrations were higher prepartum, whereas plasma β-hydroxybutyrate and glucose concentrations were lower. During the first 10 d after parturition, plasma triacylglycerol concentration was higher in FD, and prepartum plasma glucose and cholesterol differences persisted during the first 14 wk of lactation. Irrespective of prepartum nutrient composition, concentrations of plasma leptin and subcutaneous fat leptin mRNA decreased between −10 d to +10 d relative to parturition, and liver lipids and glycogen reached maximum and minimal values, respectively, 10 d after parturition. Acetyl-coenzyme A carboxylase α mRNA abundance in subcutaneous fat decreased between −10 d to +1 d relative to parturition by 97%, whereas it was generally much lower in the liver and remained at a low level until wk 14 of lactation. In conclusion, feeding a diet containing rumen-protected fat during late lactation and dry period until calving negatively affected dry matter intake, energy balance, and milk yield during subsequent lactation, did not change acetyl-coenzyme A carboxylase α mRNA abundance in subcutaneous fat, and was not beneficial for liver lipid accumulation.     

Effect of stage of lactation and varying available energy intake on milk production, milk composition, and subsequent tissue enzymic activity

Twenty-four cows were allotted at parturition to receive one of four rations for 180 days. Rations were regular ad libitum (about 20% crude fiber), concentrate ad libitum (about 10% crude fiber), and restricted to recommended energy intake, and intermediate ration (14% crude fiber) ad libitum. Cows on concentrate consumed less dry matter, fiber and protein than intermediate and regular cows. Cows fed more forage gained more weight, had milk with higher protein and fat content, but were similar in milk production to those fed high concentrate. Fat test decreased to 4 wk in all treatments, and by 8 or 9 wk cows fed concentrate decreased to their lowest fat test. Concentrate restriction enhanced fat test beyond 8 wk. Ruminal propionate was higher and similar for both concentrate groups. Ruminal volatile fatty acids were higher, glucose slightly higher, and blood acetate lower for cows on ad libitum concentrate compared to intermediate. Mammary and adipose tissue from cows in midlactation were assayed for key enzymes of fatty acid synthesis. Activity of 6-phosphogluconate dehydrogenase tended higher for concentrate rations in adipose tissue, but mammary tissue was 21 to 28 times as active. Mammary tissue was 7 to 10 times as active as adipose tissue in fatty acid synthetase with no difference in rations.     

Effect of conjugated linoleic acid and acetate on milk fat synthesis and adipose lipogenesis in lactating dairy cows

During biohydrogenation-induced milk fat depression (MFD), nutrients are spared from milk fat synthesis and are available for other metabolic uses. Acetate is the major carbon source spared and it may increase lipid synthesis in adipose tissue during MFD. The objective of this study was to compare the effect of trans-10,cis-12 conjugated linoleic acid (CLA) and the amount of acetate spared during CLA-induced MFD on adipose tissue lipogenesis. Nine multiparous, lactating, ruminally cannulated Holstein cows (244 ± 107 d in milk; 25 ± 8.4 kg of milk/d; mean ± standard deviation) were randomly assigned to treatments in a 3 × 3 Latin square design. Experimental periods were 4 d followed by a 10-d washout. Treatments were control (CON), ruminal infusion of acetate (AC; continuous infusion of 7 mol/d adjusted to pH 6.1 with sodium hydroxide), or abomasal infusion of CLA (10 g/d of both trans-10,cis-12 CLA and cis-9,trans-11 CLA). Dry matter intake, milk yield, and milk protein yield and percentage were not affected by treatments. Compared with CON, milk fat yield decreased 23% and fat percent decreased 28% in CLA, and milk fat yield increased 20% in AC. Concentration and yield of milk de novo synthesized fatty acids (<C16) were reduced and concentration of preformed fatty acids (>C16) was increased by CLA, compared with CON. Yield of de novo synthesized fatty acids and palmitic acid was increased by AC, compared with CON. Lipogenesis capacity of adipose tissue explants was decreased 72% by CLA, but was not affected by AC. Acetate oxidation by adipose explants was not affected by treatments. Treatments had no effect on expression of key lipogenic factors, lipogenic enzymes, and leptin; however, expression of fatty acid binding protein 4 was reduced in CLA compared with CON. Additionally, hormone-sensitive lipase and perilipin 1 were decreased by CLA and acetate. Plasma glucose and glucagon concentrations were not affected by treatments; however, CLA increased nonesterified fatty acids 17.7%, β-hydroxybutyrate 16.1%, and insulin 27.8% compared with CON, and AC increased plasma β-hydroxybutyrate 18%. In conclusion, during CLA-induced MFD in low-producing cow adipose tissue was sensitive to the anti-lipogenic effects of CLA, while spared acetate did not stimulate adipose lipogenesis. However, acetate may play an important role in stimulating lipogenesis and improving energy status in the mammary gland under normal conditions.     

Effect of prepartum dietary energy on condition score, postpartum energy, nitrogen partitions, and lactation production responses

Objectives were to examine the effects of feeding to alter body condition at calving on subsequent full lactation production performance and feed intake, on BW and periparturient blood traits, and on complete energy and N balances and ration digestibility during wk 6, 10, and 14 postpartum. Thirty pluriparous Holstein cows were assigned randomly to two energy intakes from wk 33 of previous lactation through the dry period to create either normal (7.2) or thin (5.8) mean body condition scores at calving (9 = fat, 1 = thin). The thin group was fed 0 kg hominy feed daily; the normal group was fed 2.7 kg daily to supplement forage DM available ad libitum during this period. When compared with the normal group, cows in the thin condition group exhibited less negative body fat balance (-206 vs. -507 g/d); similar milk yield, DM intake, N partitions, and nutrient digestibilities; and lower fat test (3.2 vs. 4.1%) during the balance measurements. Whole blood and serum traits were within normal physiological ranges. Full lactation measurements were similar between treatments except that milk fat percentage was lower and DM intake (as percentage of BW), was higher in the thin condition group. Although mean BW at calving was more (651 vs. 599 kg) for normal condition cows, condition scores and BW were not significantly different at 14 wk postpartum; BW curves indicated similar rates of recovery of weight thereafter. Cows considered underconditioned at parturition mobilized less body fat after calving, resulting in reduced milk fat concentration without significant effects on milk yield, protein, SNF, DM intake, or nutrient utilization.     

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

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

Effect of supplemental conjugated linoleic acids on heat-stressed brown swiss and holstein cows

Heat-stressed dairy cattle are bioenergetically similar to early-lactation cows in that dietary energy may be inadequate to support maximum milk and milk component synthesis. Study objectives were to evaluate whether conjugated linoleic acids- (CLA-) induced milk fat depression (MFD) during heat stress would allow for increased milk and milk component synthesis. In addition, CLA effects on production variables and its ability to induce MFD were compared between Holstein and Brown Swiss cows. Multiparous cows (n = 8, Holstein; n = 5, Brown Swiss) averaging 97 +/- 17 d in milk were used in a crossover design during the summer (mean temperature-humidity index = 75.7). Treatment periods were 21 d with a 7-d adaptation period before and between periods. During adaptation periods, all cows received a supplement of palm fatty acid distillate (242 g/d). Dietary treatment consisted of 250 g/d of CLA supplement (78.9 g/d of CLA) or 242 g/d of palm fatty acid distillate to provide equal amounts of fatty acids. The CLA supplement contained a variety of CLA isomers (3.0% trans-8, cis-10; 3.4% cis-9, trans-11; 4.5% trans-10, cis-12; and 4.8% cis-11, trans-13 CLA). Treatments were applied 2 x/d with half of the supplement top-dressed at 0600 h and the remainder top-dressed at 1800 h. There was no overall treatment effect on dry matter intake (23.9 kg/d), milk yield (40.0 kg/d), somatic cell count (305,000), protein (2.86%), or lactose content (4.51%) or yields of these milk components. Supplementation with CLA decreased overall milk fat content and yield by 26 and 30%, irrespective of breed. The reduction of milk fat content and yield was greatest on d 21 (28 and 37%, respectively). Energy availability predicted by energy balance was improved with CLA supplementation compared with controls (3.7 vs. 7.1 Mcal/d, respectively). Respiration rate (78 breaths/min) and skin temperature (35.4 degrees C) during maximum heat load were not affected by treatment. The group receiving CLA had higher total milk fat CLA concentration (9.3 vs. 4.9 mg/g). Supplementation with CLA induced MFD and altered milk fat composition similarly between breeds and improved calculated energy balance during heat stress, but had no effect on production measures under these conditions.     

Partial replacement of corn grain by hydrogenated oil in grazing dairy cows in early lactation

Thirty-six grazing dairy cows were used to determine milk production and composition, and dry matter and energy intake when corn grain was partially replaced by hydrogenated oil in the concentrate. Four additional cows, each fitted with a ruminal cannula, were used in a crossover design to evaluate effects of supplemental fat on rumen environment and pasture digestion. All cows grazed mixed pastures with an herbage allowance of 30 kg dry matter/cow per day. The control group was fed a concentrate containing corn grain (4.49 kg dry matter/cow per day) and fishmeal (0.37 kg dry matter/cow per day), whereas the other group (fat) received a concentrate containing corn grain (2.87 kg dry matter/cow per day), fishmeal (0.37 kg dry matter/cow per day) and fat (0.7 kg dry matter/cow per day). The fat was obtained by hydrogenation of vegetable oils (melting point 58 to 60 degrees C, 30.3% C16:0, 34.9% C18:0, 21.8% C18:1, 3.3% C18:2). Supplemental fat increased milk production (control = 23.7 vs. fat = 25.0 kg/cow per day), fat-corrected milk (control = 22.5 vs. fat = 24.5 kg/cow per day), milk fat content (control = 3.64% vs. fat = 3.86%) and yields of milk fat (control = 0.86 vs. fat = 0.97 kg/cow per day) and protein (control = 0.74 vs. fat = 0.78 kg/cow per day). Milk percentages of protein, lactose, casein, cholesterol, and urea nitrogen were not affected. Pasture DMI and total DMI of pasture and concentrate and estimated energy intake were unchanged. No differences in loss of body weight or body condition score were detected. Plasma concentrations of nonesterified fatty acids, somatotropin, insulin, and insulin-like growth factor were not affected by supplemental fat. Concentrations of plasma triglyceride and total cholesterol were increased by supplemented fat, and no changes in plasma glucose and urea nitrogen were observed. The acetate-to-propionate ratio was higher in rumen fluid of cows that consumed fat (fat = 3.39 vs. control = 3.27). In situ pasture NDF degradation was not affected. The partial replacement of corn grain with fat improved the productive performance of early-lactation cows grazing spring pastures. No negative effects of supplemental fat on ruminal fiber digestion were detected.     

Dietary supplements of two doses of calcium salts of conjugated linoleic acid during the transition period and early lactation

Reduction of milk fat secretion by the use of conjugated linoleic acid (CLA) supplements may alleviate energy demands during early lactation. The objective of the present study was to evaluate lactational performance, net energy balance, and reproductive response of dairy cows supplemented with 2 doses of CLA from 2 wk before predicted calving until 9 wk postpartum. Holstein cows (n = 48) were divided into 3 treatment groups: 1) control, 2) low dose CLA treatment (CLA-1), and 3) high dose CLA treatment (CLA-2). Supplements for all treatments provided 230 g/d of fat; the control group received Ca salts of palm fatty acid distillate and the CLA groups received a mixture of Ca salts of CLA isomers and Ca salts of palm fatty acid distillate (31.6 and 63.2 g/d of CLA isomers for CLA-1 and CLA-2, respectively). Supplementation with CLA resulted in an 11 and 21% decrease in milk fat yield for CLA-1 and CLA-2, respectively. Milk production and secretion of other milk components did not differ among treatments. Milk energy output was significantly reduced with CLA-2, but net energy balance, body weight, and body condition scores were unaffected. Treatment had no effect on hepatic triglyceride concentration or plasma glucose and insulin, but nonesterified fatty acids tended to be lower for CLA-1. There were no consistent dose-related effects on reproduction variables, and no adverse effects were observed during the treatment or posttreatment period. Supplemental CLA was effective in reducing milk fat content, but it did not have a significant effect on milk yield or net energy balance.     

Effect of sources of calcium salts of fatty acids on production,nutrient digestibility,energy balance,and carryover effects of early lactation grazing dairy cows

The objective of our study was to investigate the effects of sources of calcium salts of fatty acids (FA) on production, nutrient digestibility, energy balance, and carryover effects of early lactation grazing dairy cows. Treatment diets were offered from 3 to 16 wk postpartum (the treatment period), in which all cows grazed elephantgrass (Pennisetum purpureum ‘Cameroon’) and treatments were added to a concentrate supplement. The treatments were (1) control (concentrate without supplemental fat); (2) concentrate with calcium salts of soybean FA (CSSO); and (3) concentrate with calcium salts of palm FA (CSPO). From 17 to 42 wk postpartum (the carryover period), all cows received a common diet fed as a total mixed ration. During the treatment period, CSPO increased milk yield, milk fat yield, 3.5% fat-corrected milk, energy-corrected milk, and cumulative milk yield compared with control and CSSO. Treatment CSSO increased the yield of milk but did not affect 3.5% fat-corrected milk or energy-corrected compared with control. Also, CSSO decreased milk fat yield, dry matter intake, neutral detergent fiber digestibility, and body weight and body condition loss. Compared with control, both CSSO and CSPO increased feed efficiency (3.5% fat-corrected milk:dry matter intake), and CSPO increased feed efficiency compared with CSSO. When considering energy partitioning (as % energy intake), CSPO increased energy partitioning toward milk and increased energy mobilized from body reserves compared with control and CSSO. Furthermore, CSSO tended to reduce the mobilization of energy from body reserves compared with control. In the carryover period, no differences in milk composition were observed among treatments. A treatment by time interaction was observed during the carryover period for milk yield because cows on CSPO maintained higher production compared with control and CSSO cows until 30 wk postpartum; CSSO had a lower carryover effect sustaining higher milk yield compared with control until 25 wk postpartum. In conclusion, supplementation with CSPO was an effective strategy to increase energy intake and yields of milk and milk solids and it had a greater carryover effect. Supplementation with CSSO resulted in lower mobilization of reserves and less variation in body weight and body condition throughout lactation.