Relationships between body condition,body condition loss,and serum metabolites during the transition period in primiparous and multiparous cows

In the transition period from late gestation to early lactation, dairy cows undergo tremendous metabolic changes. Insulin is a relevant antilipolytic factor. Decreasing serum concentrations of insulin and glucose, increasing serum concentrations of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB), and changes in body condition score (BCS) reflect the negative energy balance around calving. This study investigated peripartum metabolic adaptation in 359 primiparous and 235 multiparous German Holstein cows from a commercial dairy herd under field conditions. Body condition score was recorded and blood samples were taken 10 to 1 d prepartum, 2 to 4 d postpartum, and 12 to 20 d postpartum. Generalized mixed models and generalized estimation equations were applied to assess associations between prepartum BCS; BCS changes during the transition period; insulin, glucose, NEFA, and BHB serum concentrations; and milk yield, which was taken from an electronic milk meter from d 6 of lactation. Serum insulin concentrations of multiparous postpartum cows were lower compared with prepartum, and compared with primiparous cows. In general, primiparous cows had lower postpartum NEFA and BHB concentrations than multiparous cows. In primiparous cows, we identified a positive association between prepartum BCS and prepartum serum insulin concentration. Prepartum obese multiparous cows, but not primiparous cows, were characterized by higher postpartum serum NEFA and BHB concentrations and lower milk yield than other cows in the same parity class. Primiparous cows with a smaller degree of BCS loss during the transition period had higher postpartum insulin and lower NEFA concentrations and lower milk yield than other primiparous cows. In conclusion, primiparous cows had less lipolysis and lower milk yield than multiparous cows, associated with higher insulin concentrations. Avoiding high body condition loss during the transition period is a main factor in preventing peripartal metabolic imbalances of glucose and fat metabolism.     

Complementary hepatic metabolomics and proteomics reveal the adaptive mechanisms of dairy cows to the transition period

The transition period from late pregnancy to early lactation is a vital time of the lifecycle of dairy cows due to the marked metabolic challenges. Besides, the liver is the pivot point of metabolism in cattle. Nevertheless, the hepatic physiological molecular adaptation during the transition period has not been elucidated, especially from the metabolomics and proteomics view. Therefore, the present study aims to investigate the hepatic metabolic alterations in transition cows by using integrative metabolomics and proteomics methods. Gas chromatography quadrupole-time-of-flight mass spectrometry-based metabolomics and data-independent acquisition-based quantitative proteomics methods were used to analyze liver tissues collected from 8 healthy multiparous Holstein dairy cows 21 d before and after calving. In total, 44 metabolites and 250 proteins were identified as differentially expressed from 233 metabolites and 3,539 proteins detected from the liver biopsies during the transition period. Complementary functional analysis of different metabolites and proteins indicated the upregulated gluconeogenesis, tricarboxylic acid cycles, AA degradation, fatty acid oxidation, AMP-activated protein kinase signaling pathway, peroxisome proliferator-activated receptor signaling pathway, and ribosome proteins in postpartum dairy cows. In terms of the metabolites and proteins, glucose-6-phosphate, fructose-6-phosphate, carnitine palmitoyltransferase 1A, and phosphoenolpyruvate carboxykinase played a significant role in these pathways. The upregulated oxidative status may be accompanied by the pathways mentioned above. In addition, the upregulated glucagon and insulin signaling pathways also indicated the significant requirement for glucose in postpartum dairy cows. These outcomes, from the view of global metabolites and proteins, may present a better comprehension of the biology of the transition period, which can be helpful in further developing nutritional regulation strategies targeting the liver to help cows overcome this metabolically challenging time.     

The housekeeping genes GAPDH and cyclophilin are regulated by metabolic state in the liver of dairy cows

Steady-state levels of mRNA are often used to infer treatment effects on the levels of the corresponding protein. In addition, an internal standard RNA is usually measured to document specificity of treatment and to correct for intersample variation. Our objective was to evaluate whether glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and cyclophilin could be used as internal standards when studying changes in hepatic gene expression in dairy cows. Hepatic expression of GAPDH and cyclophilin was measured in 6 cows in late pregnancy (28 d prepartum) and early lactation (10 d postpartum). Each gene displayed 2- to 3-fold higher expression in early lactation than in late pregnancy. Next, we determined whether negative energy balance alone or in combination with exogenous growth hormone could mimic the effects of early lactation. Late-lactating cows were fed 120% of predicted energy requirements or 33% of maintenance requirements. During each feeding period, cows were administered excipient or bovine somatotropin in a single-reversal design with 4-d periods separated by a 2-d interval. Underfeeding increased hepatic expression of GAPDH and cyclophilin by 1- to 2-fold, whereas bovine somatotropin had no effect. Finally, the effects of insulin were studied by performing hyperinsulinemic-euglycemic clamps in late pregnancy (28 d prepartum) and early lactation (28 d postpartum). Hyperinsulinemia reduced GAPDH expression in both states, and cyclophilin expression in early lactation. In conclusion, GAPDH and cyclophilin are regulated in the liver of dairy cows and should not be used to standardize hepatic gene expression in studies involving the transition period, undernutrition, and sustained changes in plasma insulin.     

Effect of hormonal and energy-related factors on plasma adiponectin in transition dairy cows

In transition dairy cows, plasma levels of the insulin-sensitizing hormone adiponectin fall to a nadir at parturition and recover in early lactation. The transition period is also characterized by rapid changes in metabolic and hormonal factors implicated in other species as positive regulators of adiponectin production (i.e., negative energy balance, lipid mobilization) and others as negative regulators (i.e., reduced leptin and insulin and increased growth hormone and plasma fatty acids). To assess the role of onset of negative energy balance and lipid mobilization after parturition, dairy cows were either milked thrice daily (lactating) or never milked (nonlactating) for up to 4 wk after parturition. Plasma adiponectin was 21% higher across time in nonlactating than lactating cows. Moreover, nonlactating cows recovered plasma adiponectin at similar rates as lactating cows even though they failed to lose body condition. Next, we assessed the ability of individual hormones to alter plasma adiponectin in transition dairy cows. In the first experiment, dairy cows received a constant 96-h intravenous infusion of either saline or recombinant human leptin starting on d 8 of lactation. In the second experiment, dairy cows were studied in late pregnancy (LP, starting on prepartum d ?31) and again in early lactation (EL, starting on d 7 postpartum) during a 66-h period of basal sampling followed by 48 h of hyperinsulinemic-euglycemia. In the third experiment, cows were studied either in LP (starting on d ?40 prepartum) or EL (starting on d 7 postpartum) during a 3-h period of basal sampling followed by 5 d of bovine somatotropin treatment. Plasma adiponectin was reduced by an average of 21% in EL relative to LP in these experiments, but neither leptin, insulin, or growth hormone treatment affected adiponectin in LP or EL. Finally, the possibility that plasma fatty acids repress plasma adiponectin was evaluated by intravenous infusion of a lipid emulsion in nonpregnant, nonlactating cows in the absence or presence of glucagon for 16 consecutive hours. The intralipid infusion increased plasma fatty acid concentration from 102 to over 570 µM within 3 h but had no effect on plasma adiponectin irrespective of presence or absence of glucagon. Overall, these data suggest that energy balance around parturition may regulate plasma adiponectin but do not support roles for lipid mobilization or sustained changes in the plasma concentration of leptin, insulin, growth hormone, or fatty acids.     

Low doses of bovine somatotropin during the transition period and early lactation improves milk yield, efficiency of production, and other physiological responses of Holstein cows

The objectives of this experiment were to determine whether low doses of bovine somatotropin (bST) during the transition period and early lactation period improved dry matter intake (DMI), body weight (BW), or body condition score (BCS); provoked positive changes in concentrations of somatotropin, insulin, insulin-like growth factor-I (IGF-I), glucose, nonesterified fatty acids, and Ca; or improved milk yield (MY) response without obvious adverse effects on health status. Eighty-four multiparous Holstein cows completed treatments arranged in a 2 x 3 x 2 factorial design that included prepartum and postpartum bST, dry period (30 d dry, 30 d dry + estradiol cypionate, and 60 d dry), and prepartum anionic or cationic diets. Biweekly injections of bST began at 21 +/- 3 d before expected calving date through 42 +/- 2 d postpartum (control = 0 vs. bST = 10.2 mg of bST/d; POSILAC). At 56 +/- 2 d in milk, all cows were injected with a full dose of bST (500 mg of bST/14 d; POSILAC). During the prepartum period and during the first 28 d postpartum, no differences in mean BW, BCS, or DMI were detected between the bST treatment group and the control group. During the first 10 wk of lactation, cows in the bST treatment group had greater mean MY and 3.5% fat-corrected milk yield and lower SCC than did cows in the control group. When cows received a full dose of bST, an increase in milk production through wk 21 was maintained better by cows in the bST group. Mean concentrations of somatotropin, IGF-I, and insulin differed during the overall prepartum period (d -21 to -1). During the postpartum period (d 1 to 28), cows in the bST group had greater mean concentrations of somatotropin and IGF-I in plasma. Concentrations of Ca around calving did not differ because of bST treatment. Results suggest that changes in concentrations of blood measures provoked by injections of bST during the transition period and early lactation period resulted in improved metabolic status and production of the cows without apparent positive or negative effects on calving or health.     

Effects of pre- and postfresh transition diets varying in dietary energy density on metabolic status of periparturient dairy cows

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 NE_L/kg) or high energy density diet (DH; 1.70 Mcal of NE_L/kg). After calving, half of the cows from each prepartum treatment were assigned to a low (L; 1.57 Mcal of NE_L/kg) or high energy density diet (H; 1.63 Mcal of NE_L/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.     

Changes in the expression of hepatic genes involved in cholesterol homeostasis in dairy cows in the transition period and at different stages of lactation

This study was performed to investigate changes in expression level of genes involved in hepatic cholesterol metabolism in the transition from pregnancy to lactation and during different stages of lactation in dairy cows. Therefore, relative mRNA abundances of several genes involved in various pathways of cholesterol homeostasis in liver biopsy samples of 20 dairy cows, taken in late pregnancy (3 wk prepartum) and early lactation (1, 5, and 14 wk postpartum), were determined. At 1 wk postpartum, hepatic mRNA abundances of genes involved in cholesterol synthesis (3-hydroxy-3-methylglutaryl-coenzyme A reductase, mevalonate kinase, and farnesyl diphosphate synthase), cholesterol uptake from blood (low-density lipoprotein receptor), bile acid synthesis (cholesterol-7α-hydroxylase), cholesterol efflux [ATP-binding cassette (ABC) transporter A1 and ABCG1], esterification of cholesterol (acyl-coenzyme A:cholesterol acyltransferase), and proteins involved in assembly and secretion of very low-density lipoproteins (microsomal triglyceride transfer protein, ApoB100) were increased compared with 3 wk prepartum. The mRNA abundances of most of these genes decreased after 1 wk of lactation and reached levels in 5 and 14 wk of lactation similar to those at 3 wk prepartum. Only mRNA abundances of cholesterol-7α-hydroxylase, ABC transporters, and ApoB100 remained at 5 and 14 wk postpartum at levels higher than those at 3 wk prepartum. Hepatic cholesterol abundance was highest at 1 wk postpartum and was, thereafter, decreasing to values similar to that at 3 wk prepartum. Overall, this study shows that the onset of lactation is associated with an increased expression of various genes involved in cholesterol metabolism in the liver of dairy cows, suggesting that pronounced changes in hepatic cholesterol metabolism take place in the periparturient phase.     

Effect of prepartum dietary protein level on performance of primigravid and multiparous Holstein dairy cows

This study compared the effects of two levels of crude protein (CP) fed during late gestation on the performance, blood metabolites, and ovarian activity of Holstein cows. One-hundred and six cows (42 primigravid and 64 multiparous) 32 d before calving were divided into two groups and fed diets containing moderate (12.7% CP, 36% rumen undegradable protein, (RUP) or high (14.7% CP, 40% RUP) protein. Higher prepartum CP diet increased milk production during the first 120 d in milk (DIM), but most of that effect was detected for the primigravid cows. Primigravid cows fed the prepartum diet higher in protein produced 2.0 kg/d more milk and 3.1 kg/d more 3.5% fat-corrected milk (FCM) during early lactation. Yields of milk fat and protein in early lactation were also increased by the high prepartum CP diet fed to primigravid cows. During the complete lactation, the response to prepartum dietary protein differed between primigravid and multiparous cows. Yields of milk, 3.5% FCM, and milk fat and protein were not affected by the prepartum diet for primigravid cows, but decreased for multiparous cows fed the high protein diet. However, primigravid cows fed the high prepartum protein diet had a higher 305-d mature equivalent milk yield. Colostrum composition, blood metabolites, ovarian activity, and disease incidence were not influenced by prepartum protein. Data from this study suggest that the current prepartum protein recommendation seems to be adequate for multiparous cows, but late-gestation primigravid cows might benefit from diets with a CP content above 12.7%.     

Priming the cow for mobilization in the periparturient period: effects of supplementing the dry cow with saturated fat or linseed

High-producing dairy cows experience negative energy balance in early lactation. Dry-cow feeding management will affect the performance and metabolic status of dairy cows in the following early lactation. The present study evaluates dry-cow feeding strategies for priming lipid metabolism in the dairy cow to overcome the metabolic challenges in the following early lactation. Five weeks before expected calving, 27 cows were assigned to 1 of 3 isonitrogenous and isoenergetic dietary treatments: a low-fat control diet (dry-control); a high saturated fat diet (dry-HSF); and a high linseed diet (dry-HUF). The cows were fed the same TMR lactation diet after calving. The treatments were evaluated by performance and metabolic parameters in blood and liver. The cows fed dry-HSF and dry-HUF had significantly greater plasma nonesterified fatty acid concentrations compared with dry-control, and the dry-HUF cows had the greatest C18:3 concentrations in plasma in the prepartum period. Further, the cows fed dry-HSF and dry-HUF diets had a tendency for the greatest capacity for incomplete β-oxidation of fatty acids in the liver in wk 3 prepartum. The plasma cholesterol concentration was greatest for cows fed dry-HSF in the prepartum period compared with those fed dry-control and dry-HUF. The cows fed dry-HSF had the lowest plasma nonesterified fatty acid and liver fat concentrations in early lactation compared with the cows fed dry-control and dry-HUF. Data in the literature and the present experiment indicate that supplementing dry cows with a saturated fatty acid source is a positive strategy for priming dairy cows for body fat mobilization in the following early lactation.     

Differences in splanchnic metabolism between late gestation and early lactation dairy cows

In the transition from the pre- to postcalving state, the demands on the cow increase from support of gestation to high rates of milk production. This extra demand is met partly by increased intake but may also involve altered metabolism of major nutrients. Six multiparous Holstein cows were used to monitor changes in net fluxes of nutrients across the portal-drained viscera and liver (splanchnic tissues) between late gestation and early lactation. Blood samples were obtained simultaneously from the portal, hepatic, and subcutaneous abdominal veins and the caudal aorta 18 d before expected calving and 21 or 42 d after calving. On the day of blood sampling and the 3 d preceding sampling, cows were fed every 2 h. The precalving (1.63 Mcal of net energy for lactation/kg and 1,326 g of metabolizable protein/d) and postcalving (1.72 Mcal of net energy for lactation/kg and 2,136 g of metabolizable protein/d) diets were based on corn silage, alfalfa hay, and corn grain. Dry matter intake increased postcalving. Net splanchnic release of glucose increased postpartum because of tendencies for both increased portal absorption and net liver release. Increased removal of lactate, rather than AA, contributed to the additional hepatic gluconeogenesis. Although portal absorption of AA increased with intake at the onset of lactation, hepatic removal of total AA-N tended to decline. This clearly indicates that liver removal of AA is not linked to portal absorption. Furthermore, net liver removal relative to total liver inflow even decreased for Gly, His, Met, Phe, and Tyr. Together, these data indicate that in early lactation, metabolic priority is given to direct AA toward milk protein production rather than gluconeogenesis, in cows fed a corn-based ration.     

Plasma metabolome alteration in dairy cows with left displaced abomasum before and after surgical correction

Left displaced abomasum (LDA) leads to substantial changes in the metabolism of dairy cows. Surgical correction of LDA can rapidly improve the health of cows; however, changes in metabolism following surgery are rarely described. To investigate the changes of plasma metabolome in cows with LDA before and after surgical correction, blood samples were collected from 10 healthy postpartum cows and 10 cows with LDA on the day of diagnosis, then again from the LDA cows 14 d after surgery. Serum nonesterified fatty acid, β-hydroxybutyric acid, cortisol and histamine concentration, and antioxidant enzyme (superoxide dismutase and glutathione peroxidase) activities were evaluated, and the metabolic profile in plasma was analyzed using ultra-high-performance liquid chromatography time-of-flight mass spectrometry. The results demonstrated that cows with LDA experienced severe negative energy balance and oxidative stress, which can be improved by surgical correction. The metabolic profile was analyzed using multidimensional and univariate statistical analyses, and different metabolites were identified. In total, 102 metabolites differed between cows with LDA and healthy cows. After surgical correction, 65 metabolites changed in cows with LDA, compared with these cows during the LDA event. Following surgical correction, AA levels tended to increase, and lipid levels tended to decrease in cows with LDA. Pathway analysis indicated marked changes in linoleic acid metabolism, Arg biosynthesis, and Gly, Ser, and Thr metabolism in cows at the onset of LDA and following surgical correction. Surgical treatment reversed the changes in AA and lipid metabolism in cows with LDA.     

The effects of dry period versus continuous lactation on metabolic status and performance in periparturient cows

It has been argued that dairy cows with a high genetic milk production potential can maintain high milk production even with total omission of the dry period. Further, when omitting the dry period, cows are believed to experience fewer metabolic changes during the transition from late gestation to early lactation compared with cows having a traditional dry period. The performance and metabolic response to omission of the dry period for cows with an expected peak milk yield higher than 45 kg/d were studied in 28 Holstein dairy cows. The cows were followed in late gestation and in the subsequent 5 wk of early lactation. Fourteen cows were milked through late gestation (CM) and another 14 dairy cows underwent a 7-wk dry period (DRY). In the early lactation period, the cows had the same dry matter (DM) intake but cows in the CM group had a 22% reduction in milk yield compared with the cows in the DRY group. At calving, the experimental groups had the same average body weight and body condition score and there were no significant differences in body weight and body condition score changes in early lactation. However, the cows in the CM group compared with the cows in the DRY group had a higher plasma concentration of glucose and insulin and a lower plasma concentration of nonesterified fatty acids and β-hydroxybutyrate in the following 5 wk of early lactation. Furthermore, the cows in the CM group had lower liver triacylglycerol concentration and higher liver glycogen concentration in the following early lactation. It is concluded that, even in dairy cows with an expected peak milk yield above 45 kg/d, omission of the dry period results in a relatively high reduction in milk yield in the following early lactation. Furthermore, these cows are in less metabolic imbalance in the following early lactation.     

Adaptations of Glucose and Long-Chain Fatty Acid Metabolism in Liver of Dairy Cows during the Periparturient Period

Tremendous metabolic and endocrine adjustments must be made as dairy cows move from late gestation to early lactation. Requirements for glucose and metabolizable energy increase two- to threefold from 21 d before to 21 d after parturition. The liver must adapt quickly to provide the increased glucose needed to support high milk production, and to process the flood of nonesterified fatty acids taken up from extensive mobilization of adipose triglycerides. While the end results of these adaptations are well known, much less is known about the cellular and molecular mechanisms underpinning hepatic adaptation to lactation. Increases in metabolic activity per gram of liver tissue, not just increased liver mass, are responsible for increased metabolism. Compared with activities present at 21 d before parturition, the capacity of liver tissue isolated at 1 d postpartum to convert alanine (an important glucogenic amino acid) to glucose increases more on a percentage basis than does gluconeogenic capacity from propionate. Likewise, hepatic abundance of mRNA for pyruvate carboxylase increases around calving, whereas mRNA for phosphoenolpyruvate carboxykinase does not. These changes in gluconeogenic enzymes suggest that amino acids from body and feed protein may be critically important sources of glucose for peripartal cows. Hepatic tissue from cows 1 d postpartum has greater rates of palmitate esterification, total and peroxisomal beta-oxidation of palmitate, and activity of mitochondrial carnitine palmitoyltransferase than hepatic tissue from the same cows 21 d prepartum. Prepartal nutrition has been shown to modulate some of these metabolic adaptations in the liver. Effects of hormones and cytokines that mediate adaptive responses to environmental and infectious stressors (or the lack of “cow comfort”) have not been investigated. Techniques of modern biochemistry promise to further our understanding of the mechanisms of metabolic adaptation during the peripartal period, and to quantify the effects of nutrition and environment during pre- and postpartum periods on hepatic glucose and lipid metabolism.     

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

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

Effects of prepartum dietary cation-anion difference and source of vitamin D in dairy cows: Lactation performance and energy metabolism

The objectives of this experiment were to evaluate the effects of feeding diets with 2 dietary cation-anion difference (DCAD) levels and supplemented with either cholecalciferol (CH) or calcidiol (CA) during late gestation on lactation performance and energetic metabolism in dairy cows. The hypothesis was that combining a prepartum acidogenic diet with calcidiol supplementation would benefit peripartum Ca metabolism and, thus, improve energy metabolism and lactation performance compared with cows fed an alkalogenic diet or cholecalciferol. Holstein cows at 252 d of gestation were blocked by parity (28 nulliparous and 51 parous cows) and milk yield within parous cows, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial, with 2 levels of DCAD (positive, +130, and negative, ?130 mEq/kg) and 2 sources of vitamin D, CH or CA, fed at 3 mg per 11 kg of diet dry matter (DM). The resulting treatment combinations were positive DCAD with CH (PCH), positive DCAD with CA (PCA), negative DCAD with CH (NCH), or negative DCAD with CA (NCA), which were fed for the last 21 d of gestation. After calving, cows were fed the same lactation diet. Body weight and body condition were evaluated prepartum and for the first 49 d postpartum. Blood was sampled thrice weekly prepartum, and on d 0, 1, 2, 3, and every 3 d thereafter until 30 d postpartum for quantification of hormones and metabolites. Lactation performance was evaluated for the first 49 d postpartum. Feeding a diet with negative DCAD reduced DM intake in parous cows by 2.1 kg/d, but no effect was observed in nulliparous cows. The negative DCAD reduced concentrations of glucose (positive = 4.05 vs. negative = 3.95 mM), insulin (positive = 0.57 vs. negative = 0.45 ng/mL), and insulin-like growth factor-1 (positive = 110 vs. negative = 95 ng/mL) prepartum. Treatments did not affect DM intake postpartum, but CA-supplemented cows tended to produce more colostrum (PCH = 5.86, PCA = 7.68 NCH = 6.21, NCA = 7.96 ± 1.06 kg) and produced more fat-corrected milk (PCH = 37.0, PCA = 40.1 NCH = 37.5, NCA = 41.9 ± 1.8 kg) and milk components compared with CH-supplemented cows. Feeding the negative DCAD numerically increased yield of fat-corrected milk by 1.0 kg/d in both nulliparous and 1.4 kg/d in parous cows. Minor differences were observed in postpartum concentrations of hormones and metabolites linked to energy metabolism among treatments. Results from this experiment indicate that replacing CH with CA supplemented at 3 mg/d during the prepartum period improved postpartum lactation performance in dairy cows.     

Metabolic and production responses to dietary protein and exogenous somatotropin in late gestation dairy cows.

Forty-three multiparous Holstein cows were used in a completely randomized design to evaluate the effects of protein supplementation and the use of bovine somatotropin (bST; Posilac, Monsanto Co., St. Louis, MO) in late gestation on animal metabolism and productivity in the periparturient period. Treatments were initiated 28 d prior to expected calving date and continued through parturition. Diets contained either 13.3 or 17.8% crude protein and were formulated to be similar in profile of protein fractions. Within each dietary treatment, cows were assigned to receive either 0 or 500 mg of sustained released bST once every 14 d until parturition. Following parturition, all cows were subjected to the same management and dietary treatments, and production measurements were followed until 42 d in milk. The use of bST increased plasma glucose and decreased plasma nonesterified fatty acids and beta-hydroxybutyrate prior to calving. Despite these changes in metabolism, bST did not affect concentrations of fat and triglyceride in the liver prepartum or postpartum. Feeding the 17.8% protein diet failed to stimulate glucose metabolism and tended to elevate plasma beta-hydroxybutyrate in late gestation. Cows treated with bST produced 3.3 kg/d more milk than did controls across the first 42 d of lactation; the difference was 4.6 kg/d in wk 6 of lactation. The use of bST in late gestation has considerable promise to alter cow metabolism positively. The results of these and other possible periparturient responses to somatotropin may increase milk production in early lactation.     

Effects of feeding betaine-containing liquid supplement to transition dairy cows

Betaine is a natural compound found in sugar beets that serves as a methyl donor and organic osmolyte when fed to animals. The objective was to evaluate the effect of feeding betaine-containing molasses on performance of transition dairy cows during late summer in 2 trials. In early September, cows were randomly assigned to betaine (BET) or control (CON) groups either shortly after dry off (trial 1; n = 10 per treatment) or 24 d before calving (trial 2; n = 8 per treatment) based on parity and previous mature equivalent milk yield. Cows were fed common diets supplemented either with a liquid supplement made of molasses from sugar cane and condensed beet solubles containing betaine [BET, 89.1 g/kg of dry matter (DM)] or a sugar cane molasses-based liquid supplement without betaine (CON) until 8 wk postpartum. The liquid supplements had similar nutrient contents and were fed at a rate of 1.1 and 1.4 kg DM/d for pre- and postpartum cows, respectively. Starting at their entry in the studies, cows were housed in the same freestall barn without a cooling system. After calving, all cows were housed in the same barn cooled by misters and fans and milked thrice daily. Intake was recorded daily and body weight and body condition score were assessed every 2 wk. Milk yield was recorded at each milking and composition was analyzed weekly. Blood samples were collected weekly from a subset of cows to assess concentrations of metabolites and AA. No treatment effects were apparent for DM intake and body weight in the prepartum and postpartum periods. For cows enrolled at dry off, BET supported higher milk yield (45.1 vs. 41.9 kg/d) and fat content (4.78 vs. 4.34%) and elevated plasma concentrations of nonesterified fatty acids and β-hydroxybutyrate in early lactation compared to CON. However, no differences were observed for milk yield, most milk component contents and yields, and blood metabolites between treatments for cows enrolled during the close-up period. Compared to cows in the CON group, BET cows enrolled during the far-off period tended to have lower plasma concentrations of Met, Thr, and Trp during the pre- and postpartum periods. They also had lower plasma concentrations of Lys and Phe before calving but higher plasma Gly concentration after parturition. In conclusion, feeding a betaine-containing liquid supplement from far-off through early lactation improves lactation performance but increases adipose tissue mobilization and production of ketone bodies in early lactation.     

Continuous lactation in dairy cows: effect on milk production and mammary nutrient supply and extraction

Reports over the past decade have indicated that normal lactational performance can be achieved in genetically superior and high-producing dairy cows, even when the dry period between 2 lactations is omitted. The hypothesis tested in this experiment was that normal lactogenesis I and metabolic function may be achievable in continuously milked high-yielding dairy cows as a result of the genetic selection for lactation performance and hence longevity of mammary epithelial cells. The milk production and mammary nutrient uptake in response to omission of the dry period for cows with an expected peak milk yield higher than 45 kg/d were studied in 28 Holstein dairy cows managed without bovine somatotropin. Performance and metabolic parameters were followed in late gestation and in the following early lactation. Fourteen cows were milked continuously throughout late gestation, and another 14 dairy cows experienced a 7-wk prepartum dry period. Continuous milking during the prepartum period reduced milk production in the following early lactation period by >20%. The reduced milk production could not be readily ascribed to inefficiency of the mechanisms responsible for nutrient uptake by the lactating mammary epithelial cells, nor to systemic endocrine changes. This suggests that lowered mammary nutrient uptake must have been associated with reduced mammary blood flow, metabolic activity, or both, most likely as a result of disturbed lactogenesis I prepartum or lactogenesis II postpartum triggered by as yet unknown local mechanisms. Milk protein content was elevated by 0.4 percentage units in the continuously milked cows. The underlying reason is unknown, but given the current pricing system for milk, it deserves to be further investigated.     

Effect of 25-hydroxyvitamin D3 during prepartum transition and lactation on production,reproduction, and health of lactating dairy cows

We hypothesized that feeding 25-hydroxyvitamin D₃ [25-(OH)D₃] during lactation and prepartum in conjunction with negative dietary cation-anion difference diets would improve milk production, increase the probability of pregnancy, and reduce the incidence of postcalving diseases. Cows from 4 dairies with prepartum transition diets negative in dietary cation-anion difference were used in 2 randomized cohort experiments. In Experiment 1 (Exp. 1), cows were assigned to control [CON; n = 645; no 25-(OH)D₃] or treatment [TRT; n = 537; 2 mg/d of 25-(OH)D₃ from ～21 d prepartum to parturition and 1 mg/d in lactation] groups at ～21 d prepartum. Cows were monitored for weekly milk yield, milk composition every 60 d, and health and reproductive measures. In Experiment 2 (Exp. 2), cows (n = 2,064; median 147 d in milk) were assigned to 4 groups and monitored for the same measures as in Exp. 1 to the end of that lactation (L1), the subsequent transition (～21 d prepartum to parturition), and the next lactation (L2). Groups were as follows, with the amount of 25-(OH)D₃ fed (mg/d) indicated in parentheses for L1, transition, and L2, respectively: (A) control-control (CON-CON; 0–0–0), (B) treatment-treatment (TRT-TRT; 1–2–1), (C) control-treatment (CON-TRT; 0–2–1), and (D) treatment-control (TRT-CON; 1–0–0). For L1, a total of 1,032 cows entered the control groups A or C and a total of 1,032 cows in groups B or D. The number of cows in groups A to D that entered L2 was 521, 523, 273, and 248, respectively. Blood calcium, phosphorus, and 25-(OH)D₃ concentrations were measured from 17 cows/group at 5 times. In Exp. 1, TRT cows had 0.2 lower log somatic cell count than CON cows (4.21 ± 0.045 vs. 4.01 ± 0.050, respectively) and multiparous TRT cows had 41 ± 23% higher probability of pregnancy/day than multiparous CON cows, resulting in a 22-d median decrease in time to pregnancy. Primiparous TRT cows had 1.67 ± 0.40 times greater odds of mastitis/day than primiparous CON cows. In Exp. 2 TRT-TRT cows had between 16 and 29% lower probability to be bred/day than other groups. Multiparous CON-CON and TRT-CON cows had 20 ± 8% and 30 ± 17% greater probability of pregnancy, respectively, than multiparous TRT-TRT cows. Serum calcium concentrations were not affected by group, but phosphorus and 25-(OH)D₃ concentrations were highest in the TRT-TRT cows. The study provides further insights into the use of 25(OH)D₃ in transition and lactation.     

Pattern of serum protein fractions in dairy cows during different stages of gestation and lactation

In dairy cows the period of transition from late gestation to early lactation is recognized as inducing considerable metabolic adaptation. The aim of this study was to analyse modifications in serum protein values occurring during the dry and the transition period and during lactation in a group of five Holstein cows of high average milk production. For all subjects, selected on the basis of their pregnancy status, blood samples were collected at different physiological phases: dry period (-60, -30 d to calving), transition period (almost 7 d to calving, 7 d after calving), and lactation (weeks 2, 5 and 15 after calving), for a total of eight blood samples for each cow. On each blood sample total proteins and electrophoresis analysis were performed. On the data obtained, normally distributed (P<0·05, Kolmogorov-Smirnov's test), one-way Repeated Measure Analysis of Variance (ANOVA), was applied to evaluate the influence of different stages of gestation and lactation on the considered parameters. Results showed a significant effect on total proteins, α1-globulins, β-globulins, γ-globulins and albumin/globulin ratio. Most of the detected modifications were related to the transition from gestation to lactation, indicating that it is a period of great metabolic stress for cows. On the basis of the obtained results we can affirm that the pattern of serum protein fraction rn could give information about dehydration, plasma volume expansion and hepatic function occurring during the peripartum period in dairy cows.