Influence of Exogenous Beta-hydroxybutyrate on Metabolic Efficiency, Luteinizing Hormone, and Hypothalamic and Pituitary Gene Expression in Sheep

Four studies were conducted to determine the effect of central administration of exogenous beta-hydroxybutyrate (BHB) on circulating metabolites, luteinizing hormone (LH), and hypothalamus and pituitary differential gene expression in sheep. In three of the studies, wethers were assigned to be centrally injected into the lateral ventricle of the brain through intracerebroventricular cannulas (ICV) with a single injection of BHB solution (BHB; 12,800 μmol/L) or saline solution (CON; 0.9% NaCl). In Exp. 1, between CON and BHB treated sheep, 11 and 44 genes were differentially expressed (adj. P \u3c 0.05) within the pituitary and hypothalamus, respectively. Functional enrichment analyses revealed BHB altered expression of genes in pathways related to stimulus perception, inflammation, and cell cycle control. In Exp. 2, wethers were injected through the ICV with one of 4 treatments: 0, 400, 800, or 1,600 μmol/L of BHB solution. Serum glucose concentrations tended (P = 0.08) to decrease linearly with increasing concentrations of BHB. Amplitude of LH peaks decreased linearly (P = 0.03) with increasing concentrations of BHB. In Exp. 3, wethers were centrally injected with either 12,800 μmol/L BHB or saline. Serum glucose and insulin concentrations increased (P \u3c 0.01) with BHB injection. Injection of BHB decreased (P \u3c 0.01) circulating serum NEFA concentrations. Injection of BHB did decrease (P \u3c 0.01) mean LH concentration. Wethers injected with BHB had decreased (P \u3c 0.01) amplitudes of LH peaks. In Exp. 3, ovariectomized ewes were assigned to be fed either at BW maintenance (MAINT) or fed at a 30% feed reduction (RES). Ewes were randomly assigned to be centrally injected for 10 d with 300 μl into the lateral ventricle twice daily with one of two treatments of either BHB or saline. Serum glucose concentrations decreased (P = 0.02) with infusion of BHB. Serum NEFA concentration increased (P \u3c 0.01) with RES ewes. Luteinizing hormone exhibited a tendency (P = 0.06) for a diet × treatment interaction. Overall, elevated BHB in the brain may mimic a negative energy signal leading to alterations in serum concentrations of metabolites and LH

New Approaches for the Quantification of Metabolic and Economic Trade-Offs Related to the Health and Longevity of Individual Dairy Cows

Deutscher Titel: Neue Ansätze für die Quantifizierung metabolischer und wirtschaftlicher Zielkonflike mit Bezug zur Gesundheit und Langlebigkeit von Milchkühe

Effects of peripartum propylene glycol supplementation on nitrogen metabolism, body composition and gene expression for the major proteolytic systems in skeletal muscle in transition dairy cows

Early-lactating dairy cows mobilize body protein, primarily from skeletal muscle, to provide amino acids which are directed towards gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and our hypothesis was that its dietary inclusion could attenuate skeletal muscle wasting by reducing amino acid-driven gluconeogenesis. The major objectives of this study were to delineate the effects of pre- and post-partum PG supplementation in transition dairy cows on whole-body nitrogen (N) balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG (PG). Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress. All measurements were conducted at 3 time intervals starting at d -14 ± 5, d 15 and d 38 relative to calving. Propylene glycol had no effect (P > 0.05) on whole-body N balance, urinary 3-MH excretion, and body composition. However, N balance was lower (P 0.05) on body weight (BW), and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain (P = 0.96) and 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) (P = 0.54); however, PG supplementation down-regulated mRNA expression for µ-calpain at d 15 (P = 0.02), and tended to down-regulate mRNA expression for ubiquitin at d 15 (P = 0.07) and proteasome 26S subunit-ATPase at d 38 (P = 0.097). Relative to calving, mRNA abundance for m-calpain (P = 0.02) and µ-calpain (P = 0.005) were higher at d 15 compared to d -14 and d 38. Messenger RNA abundance for ubiquitin (P = 0.07) and 14-kDa E2 (P = 0.005) were lower at d 38 compared to d 15. In summary, these results demonstrate that up-regulation of the Ca2+-dependent and ubiquitin-mediated proteolytic pathways are the mechanisms by which skeletal muscle wasting occurs in early-lactating cows. In addition, dietary supplementation with PG may down-regulate some of these proteolytic pathways, thereby potentially attenuating undesirable skeletal muscle wasting

Effects of feed restriction on milk production and metabolism in mid-lactation dairy cows

Availability of glucose precursors and a proper interorgan coordination during the metabolic cascade of adaptations occurring during periods of lower DMI, are the vital importance to achieve a successful transition from late gestation to lactation. The aim of the study was to determine metabolic responses to a short-term period of negative energy balance induced by feed restriction (FR) and the effect of abomasal supplementation of different amino acids (AA) or glucose. Seven multiparous Holstein cows (93 ± 15 DIM) were randomly assigned to 7 treatments in a 7 × 4 incomplete Latin square design. In 6 treatments, daily DMI was restricted to provide 60% of energy requirements during 5 d; the 7th treatment consisted of ad libitum (AL) intake. Feed was provided once daily at 0900 h. Effects of FR (AL vs RC), day, time within day, and interactions were evaluated with ANOVA using the MIXED procedure of SAS. Evaluating the effect of FR, milk yield (P < 0.01), milk protein concentration (P = 0.03) and yield (P < 0.01), and lactose yield (P < 0.01) were lower for RC, whereas milk fat (P < 0.01) and urea N concentrations were higher (P < 0.01). Treatment RC induced lower plasma insulin (P = 0.01) and glucose (P = 0.04) concentrations, with quadratic (P < 0.01 for both) decreasing trends reaching nadir on d 3. Concentration of NEFA was higher (P < 0.01) and increased quadratically (P < 0.01) with its maximum on d 3 during FR. Serum BHBA increased linearly (P = 0.04) for RC (RC x d; P = 0.16) with its peak at d 4. Catabolism of amino acids (AA) increased early during FR as indicated by plasma urea N increasing (P < 0.01) quadratically (P < 0.01), with its peak on d 2 and decreasing afterward. Accounting for all the amino-N circulating in form of urea or eliminated in milk as MUN, the decrease in concentration of all the AA in circulation analyzed here was not sufficient for the amount of urea synthetized. Therefore, it seems probable that body tissue protein was rapidly mobilized, to produce the energy required to support the higher ECM especially through milk fat and lactose. Plasma 3-methylhistidine increased linearly (P < 0.01) denoting protein tissue mobilization of contractile fibers. A group of AA (Glu, Val, Leu, Tyr, Phe, Ser, His, Thr, Asn, Ala, Pro, Met) decreased in a quadratic manner with the nadir at d 2 and 3, while Asp, Trp and Ile decreased linearly. Concentrations of other AA increased (Gln, Gly, Cys) or did not vary (Lys, Arg) during FR. Plasma AA concentrations decreased after feed delivery in both diets, coinciding with the increase of insulin, except for Glu that increased in all treatments and Gln that increased after feeding only during FR. Metabolic adaptations to low insulin during FR seemed to select catabolism of AA as the first energy source before later relying more on fatty acids. Based on responses of plasma AA and insulin to feeding, protein synthesis in tissues likely remained sensitive to insulin within day

THE EFFECTS OF NUTRITIONALLY‐MODULATED PREPARTUM BCS ON PRE‐ AND POSTPARTUM METABOLIC RESPONSES, \u3cem\u3eIN VITRO\u3c/em\u3e LIPID METABOLISM AND PERFORMANCE OF MULTIPAROUS BEEF COWS

Increased BCS at calving due to nutritional manipulation during the prepartum period resulted in greater mobilization of body fat after calving, regardless of plane of nutrition during the last 60 d of gestation. Although fatter cows were shown to have greater mobilization of reserves during the postpartum period, they maintained greater BCS at all points from calving to weaning compared to cows calving with fewer reserves at calving. A unique finding of this experiment was that the variation in BCS at calving was positively associated with BCS loss for cows fed to accrete BC during the prepartum period but was not associated with BCS loss for cows fed at maintenance levels during gestation. This finding suggests a threshold response in which BCS loss postpartum is only related to BCS at calving of 6.5 or greater. Progeny of fatter cows were heavier at d 40 and 84, but no treatment differences existed at weaning. The relationship between BCS at calving and calf BW at d 40 differed by treatment. This suggests a threshold response in which calf BW is positively related to increases in BCS up to 5.75. At BCS ≥ 5.75 calf weights were greater than at lower BCS levels but were unrelated to incremental changes in BCS. Altering dietary energy level during mid and late gestation altered the net lipolytic rate of beef cows and altered the timing of changes in tissue sensitivity and total lipolysis. Basal release of NEFA did not change for cows on a maintenance diet, but increased significantly for fatter cows prior to calving, whereas basal glycerol was unaffected by treatment. The stimulated release of glycerol was also unaffected by treatment, but increased across all periods. The ratio of stimulated glycerol and NEFA release to basal release of glycerol and NEFA indicate that the AT of HI cows has a delayed response to the increase in sensitivity to lipolytic stimulants that is associated with homeorhetic adaptations; however, at 7 d after calving, no differences were observed for net or total lipolytic capacity of the tissue. Providing mature beef cows ad libitum access to a high‐energy diet alters pre‐calving sensitivity of AT, but after calving and when animals are receiving a common diet, no differences in lipolysis were observed. Thus, BCS (4.91 to 6.56), as manipulated by diet, does not appear to impair lipolytic function and regulation in beef cows as observed in dairy cows

Untersuchungen zum Einsatz von konjugierten Linolsäuren (CLA) und Vitamin E, sowie deren Wechselwirkungen, als Interventionsmaßnahme zur Verminderung einer ketotischen Stoffwechselbelastung und des oxidativen Stresses bei peripartalen Milchkühen - [kumulative Dissertation]

Die Energiebilanz der Milchkuh in der peripartalen Phase ist negativ. Die Kühe mobilisieren Körperfett. Diese Mobilisierung führt zu hohen Konzentrationen an unveresterten Fettsäuren (NEFA) und Betahydroxybutyrat (BHB). Trans-10, cis-12 konjugierte Linolsäure (CLA) kann den Milchfettgehalt reduzieren und die Energiebilanz positiv beeinflussen. Vitamin E (Vit. E) ist ein Antioxidans und über die Empfehlung hinausgehende Supplementierung könnte dazu beitragen, den durch die Abkalbung und die hohen NEFA- und BHB-Konzentrationen verursachten oxidativen Stress zu vermindern. In diesem Versuch sollten die Einflüsse einzelner und kombinierter Supplementierung mit CLA und Vit. E auf den Energiestoffwechsel, die Laktationsleistung, das Milchfettprofil sowie das Immunsystem der peripartalen Milchkuh untersucht werden. Ergebnisse zeigen, dass die Supplementierung die Lipomobilisierung nicht beeinflusste. Die Reduktion des Milchfettgehalts und der -menge fiel in der Gruppe, die die kombinierte Supplementierung erhielt, geringer aus. Der Serumstatus des Vit. E blieb ebenso wie die Immunfunktion durch die Supplementierungen unbeeinflusst.Energy balance of the dairy cow in the transition period is negative. Cows mobilize adipose tissue, which results in high concentrations of non-esterified fatty acids (NEFA) as well as betahydroxybutyrate (BHB). The trans-10, cis-12 isomer of conjugated linoleic acid (CLA) is capable to reduce milk fat content and thereby possibly reduce the negative energy balance. Vitamin E (Vit. E) is an antioxidant and supplementation above the recommendation might counteract the oxidative stress caused by parturition and high NEFA- and BHB-concentrations in serum. This trial aimed to clarify the influences of single and combined supplementations of CLA and Vit. E on the energy metabolism, lactation performance, milk fatty acid profile and immune system of dairy cows during the transition period. Results show that supplementations did not affect lipomobilisation. Reduction of milk fat content and yield in cows supplemented with the combination of CLA + Vit. E was less distinct. Serum status of Vit. E remained unaffected by either treatment. Results suggest that both supplementations did not improve the immune function.vorgelegt von Stephanie Schäfer

Energy balance and metabolic status of dairy cows : a study using metabolomics, proteomics and machine learning approaches

In early lactation, dairy cows typically experience a negative energy balance (NEB) due to the high energy requirement for milk yield and low energy intake from feed. Negative energy balance has been related to metabolic disorders, compromised health and fertility, and reduced productive lifespan. Estimation of the energy balance and metabolic status is not easy on the farm. Therefore, the aims of this thesis were to estimate energy balance and metabolic status of dairy cows using metabolomics and machine learning techniques, and to investigate the metabolic pathways related to energy metabolism of dairy cows in early lactation using metabolomics and proteomics techniques. In this thesis, on-farm cow data collected from two earlier studies (study I, 168 cows and study II, 127 cows) were used to estimate energy balance and metabolic status of cows with machine learning approach. In addition, milk and blood samples obtained from study II were analysed with metabolomics and proteomics approaches. To estimate energy balance of dairy cows, estimated performance of reduced models with either milk metabolites, or milk production traits or both ranged from 0.53 to 0.78 (adjusted R-square).Milk metabolites important in explaing negative energy balance in cows where glycine, choline and carnitine. . To estimate metabolic status of dairy cows using on-farm cow data, random forest, support vector machine, and partial least square discriminant analysis performed better than other machine learning algorithms. Based on the metabolomics results, plasma and milk metabolites altered during NEB of dairy cows in early lactation reflected the metabolism in the body or the mammary gland of dairy cows. Metabolic processes in the mammary gland during NEB were related to leakage of cell content due to mammary cell apoptosis and, to synthesis of nucleic acids and cell membrane phospholipids, protein glycosylation and an increase in one-carbon metabolic processes. The processes are related to cell renewal and proliferation. Since NEB is highly related to milk production this seem logical. Blood metabolites related to energy balance were mainly reflecting energy metabolism (mobilization of body fat, skeleton muscle, bone) increased blood flow and gluconeogenesis. Better understanding of the metabolic pathways through a metabolomics and proteomics approach does not only provide biomarkers for pathways under stress during NEB but may also allow for targeted dietary interventions when glucose and rumen protected choline are interesting candidates. In conclusion, the energy balance of dairy cows can be estimated by milk metabolites based on metabolomics study, and metabolic status can be estimated by machine learning algorithms using on-farm cow data. Moreover, energy balance of dairy cows in early lactation was related with milk and plasma metabolites which revealed metabolic pathways that allow more targeted intervention strategies

Use of Rumen Modifiers to Manipulate Ruminal Fermentation and Improve Nutrient Utilization and Lactational Performance of Dairy Cows

Overall hypothesis in a series of lactation studies reported in this dissertation was that supplementing different rumen modifiers would have consistent responses on ruminal fermentation and lactational performance under optimal ruminal fermentative conditions. First experiment investigated the influence magnesium exchanged zeolite on ruminal fermentation and lactational performance. Intake of dry matter (DM), milk yield, milk fat concentration, and feed efficiency were not affected. Milk protein concentration tended (P = 0.15) to be higher for the zeolite total mixed ration (TMR). Ruminal pH tended to increase (P = 0.11) by feeding the sodium bicarbonate or the zeolite. A second lactation experiment determined the influence of quebracho condensed tannin extract (CTE) on ruminal fermentation and lactational performance. Supplementing CTE decreased intakes of DM and nutrients regardless of forage level thereby increasing feed efficiency. Milk yield and components were not affected. Milk urea N (MUN) and total VFA concentration decreased by supplementing CTE. Cows fed CTE had decreased ruminal ammonia-N and MUN concentrations, indicating that less ruminal N was lost as ammonia. A third lactation trial assessed whole safflower seeds (SS) on ruminal fermentation, lactational performance, and milk fatty acids. Feeding the Nutrasaff SS TMR (NSST) decreased intake of neutral detergent fiber. Digestibilities of nutrients, milk yield and components, ruminal pH, ruminal VFA, and ammonia-N were similar. Ruminal C16:0 fatty acid (FA) concentration increased with the cottonseed TMR (CST), while C18:1 cis-9 and C18:2 n-6 tended (P = 0.10 and P = 0.09, respectively) to increase with SS supplementation. Supplementing SS decreased milk C16:0 concentration, whereas it increased C18:1 cis-9 and C18:1 trans-9. Milk C18:1 trans-11 FA and cis-9, trans-11 conjugated linoleic acid increased and tended (P = 0.07) to increase with feeding the NSST. Feeding zeolite would cost-effectively replace sodium bicarbonate as a ruminal buffer, whereas CTE may change the route of N excretion, having less excretion into urine, but more into feces. Whole SS can be an effective fat supplement to lactating dairy cows without negative impacts on lactational performance and milk FA. These studies demonstrate that the three rumen modifiers can positively manipulate ruminal fermentation

Supplementation and Reproductive Strategies for Beef Females as Part of a May-Calving Herd in the Nebraska Sandhills

The objective of these 4 studies was to evaluate the effects of management decisions on reproductive performance of beef females. Experiment 1 evaluated the efficacy of a novel s.c. prostaglandin F2a injection on estrus synchronization and pregnancy success in yearling beef heifers. Heifers receiving a 2 mL s.c. injection of Lutalyse HighCon had similar estrus response and pregnancy rates compared to 5 mL Lutalyse i.m. within 2 different estrus synchronization programs. In experiment 2, May-calving heifers and primiparous cows were allotted to receive either no supplementation or supplement (0.45 or 0.91 kg/d per animal, heifers or primiparous cows, respectively) throughout the breeding season. Although supplementation increased BW, pregnancy rates were not impacted. In experiment 3, May-calving females were allotted to graze either sub-irrigated meadow or upland range throughout the breeding season. No differences in pregnancy rate were detected, despite differences in BW and BCS gain over the breeding season. Finally, experiment 4 examined the effects of varying levels of late gestation nutrition on dam and subsequent progeny performance. Multiparous, May-calving dams were allotted to graze either meadow or range forage and then to receive either no supplement or 0.45 kg/d per cow of a 33% CP supplement during late gestation. Prepartum meadow grazing tended to increase dam rebreed pregnancy rates. Heifer progeny had increased rebreed pregnancy rates as a primiparous cow, and steer progeny had increased marbling score if their dam grazed meadow. Dam supplementation increased BW of progeny over 2 generations. In summary, these experiments demonstrate the following findings: 1) a higher concentrate s.c. injection of prostaglandin F2a is effective in synchronizing estrus of beef heifers, 2) supplementation or differing forage type during the breeding season of a May-calving herd does not impact reproductive response, and 3) differences in late gestation nutrition of a May-calving herd results in altered progeny growth and performance. Advisors: Richard N. Funston and Jennifer R. Woo

Impact d'un supplément combiné d'acide folique et de vitamine B₁₂ en période prépartum et en début de la lactation chez la vache laitière

Tableau d'honneur de la Faculté des études supérieures et postdorales, 2014-2015Les objectifs de cette thèse étaient d’évaluer les effets d’un supplément combiné d’acide folique et de vitamine B12 sur les performances zootechniques en fermes laitières (première étude) et sur la cinétique du glucose en début de lactation (deuxième étude). Les traitements suivants ont été donnés par injections intramusculaires hebdomadaires de trois semaines avant le vêlage jusqu’à huit ou neuf semaines postpartum : pour la première étude 1) saline ou 2) acide folique et vitamine B12 et pour la deuxième étude 1) saline; 2) acide folique; 3) vitamine B12; ou 4) acide folique et vitamine B12. Pour la première étude, 805 vaches dans 15 troupeaux ont été impliquées. L’incidence de dystocie a été plus basse et la première insémination postpartum a eu lieu plus tôt pour les vaches multipares recevant le supplément que pour les vaches multipares ne le recevant pas. Le supplément n’a pas eu d’effet sur la production laitière. Toutefois, la concentration en gras du lait a diminué et celle en protéines a augmenté pour les vaches recevant le supplément. De plus, ces vaches ont perdu moins de poids corporel en début de lactation suggérant un effet du supplément sur la répartition de l’énergie. L’analyse économique a indiqué que ce supplément a été rentable pour la moitié des fermes à l’étude. Le supplément a augmenté la concentration en vitamine B12 du lait dans tous les troupeaux. Pour la deuxième étude, 24 vaches multipares ont été utilisées. Les concentrations plasmatiques de folates et de vitamine B12 des animaux témoins étaient plus élevées que ce qui a été rapporté dans la littérature. Étonnamment, le supplément d’acide folique a diminué le taux d’apparition du glucose à la neuvième semaine postpartum. L’ingestion, la concentration en glycogène hépatique et le pourcentage de glucose synthétisé provenant du propionate étaient semblables entre les traitements. Les résultats de ces études indiquent que, sous certaines circonstances, les apports d’acide folique et de vitamine B12 par la microflore du rumen semblent adéquats pour optimiser les performances des vaches. Cependant, il n’existe actuellement aucun moyen de prédire les apports en ces vitamines pour l’animal selon la ration reçue.The objectives of this thesis were to evaluate the effects of a combined supplement of folic acid and vitamin B12 on performance in commercial dairy herds (first study) and on glucose kinetic in early lactation (second study). The following treatments were given by weekly intramuscular injections from three weeks before calving until eight or nine weeks postpartum: for the first study 1) saline or 2) folic acid and vitamin B12 and for the second study 1) saline; 2) folic acid; 3) vitamin B12 or; 4) folic acid and vitamin B12. For the first study, 805 cows in 15 herds were involved. The incidence of dystocia was lower and the first breeding postpartum occurred at an earlier time for multiparous cows receiving the vitamin supplement than for multiparous cows that did not. Vitamin supplement did not affect milk production. However, milk fat concentration decreased and milk protein concentration increased for dairy cows receiving the supplement. Moreover, these cows lost less body weight in early lactation suggesting an effect of the vitamin supplement on energy partitioning. The economic analysis showed that this supplement was profitable for half of the studied herds. The vitamin supplement increased vitamin B12 concentration in milk within each herd. For the second study, 24 multiparous cows were involved. Plasma concentrations of folates and vitamin B12 from controls were higher than previously reported in the literature. Surprisingly, the folic acid supplement decreased whole-body glucose rate of appearance at week nine postpartum. However, dry matter intake, liver glycogen concentration, and percentage of glucose synthesized from propionate were similar among treatments. Results from these two studies highlighted that, under some circumstances, supplies of folic acid and vitamin B12 from ruminal microflora seem to be adequate to optimize cow performance. However, it is not possible under the actual state of knowledge to predict supplies of these vitamins for the animal according to the diet