Associations of a liver health index with health, milk yield, and reproductive performance in dairy herds in the northeastern United States.

The objective was to evaluate a liver health index (LHI) by evaluating its association with negative health events, milk yield, and risk of pregnancy within 150 d in milk (DIM). In a retrospective cohort study, an LHI was calculated based on plasma albumin, cholesterol, and bilirubin concentrations for 265 primiparous and 611 multiparous cows 3 to 12 DIM enrolled across 72 farms in the northeastern United States. Mixed effects linear regression models were used to evaluate if (1) metritis (MET), (2) displaced abomasum (DA), (3) clinical ketosis (CK), (4) one or more of the 3 disorders (MET, DA, or CK), (5) 2 or more of the 3 disorders (MET, DA, or CK), or (6) culling within 30 DIM was associated with LHI. Mixed effects linear regression models were used to evaluate if LHI was associated with 305-d mature equivalent milk at the fourth test day (ME305; mean ± standard deviation: 114 ± 13 DIM) and a Cox proportional hazards model was used to evaluate if LHI was associated with pregnancy within 150 DIM. Cows that were diagnosed with MET, DA, CK, one or more of the disorders, 2 or more of the disorders, or were culled within 30 DIM had a lower LHI than cows that were not diagnosed with a disorder or culled. A 1-unit increase in LHI was associated with a 154 ± 38 kg increase in ME305 and a 8% increased risk of pregnancy within 150 DIM [hazard ratio (95% confidence interval): 1.08 (1.03 to 1.14)] for multiparous cows; however, we did not identify a relationship between LHI and ME305 or pregnancy within 150 DIM for primiparous cows. These results suggest that the LHI is associated with health, milk yield, and pregnancy within 150 DIM for multiparous cows and health for primiparous cows; therefore, the LHI can be used as a tool to evaluate transition cow success.

Rumen effects of monensin in dry cow diets varying in energy density.

Controversy has existed as to whether monensin will provide equal or differential benefits in a higher-energy, lower-roughage close-up diet versus a higher-roughage, lower-energy diet. Our objective was to determine the rumen effects of a controlled-energy, high-fiber diet balanced to meet but not greatly exceed energy requirements during the dry period or a traditional 2-group approach of higher-energy close-up diet. The effects of added monensin in each diet type were determined. Multiparous Holstein cows (n = 17) were fitted surgically with ruminal cannulas. During the first 4 wk of the dry period, all cows were fed a controlled-energy, high-fiber diet (CE) as a total mixed ration for ad libitum intake. During the last 3 wk before calving, half of the cows were switched to a higher-energy, close-up diet until calving (CU), whereas the other half continued to receive the CE diet. Within each dietary group, half of the cows received monensin (MON) supplementation in the diet (24.2 g/t of total dry matter) and half did not (CON). After calving, all cows received the same lactation diet containing monensin (15.4 g/t of dietary dry matter). At 14 d prepartum, dry matter intake was not different across treatments. The weight of rumen contents was greater for cows fed CE. Rumen liquid dilution rate, solids passage rate, pH, total volatile fatty acid (VFA) concentrations, molar proportions of acetate and propionate, and papillae length did not differ among diets. Butyrate percentage tended to be greater for cows fed CE. Postpartum, dry matter intake, mass of rumen contents, solids passage rate, pH, total VFA concentration, molar percentages of propionate and butyrate, and papillae length did not differ among treatments. Liquid dilution rate (16.6, 10.7, 16.0, and 18.2%/h for CE + CON, CE + MON, CU + CON, and CU + MON, respectively) was affected by a diet × monensin interaction. Cows on the CE + CON diet had a greater ruminal proportion of acetate than did cows fed CU + CON, whereas cows fed monensin on either diet were intermediate (diet × monensin interaction). Addition of MON to the CU diet decreased the proportion of propionate (diet × monensin interaction). Cows fed CE had greater mass of rumen contents before parturtition but the high inclusion of wheat straw in the CE diet did not negatively affect rumen papillae length. Monensin inclusion differentially affected liquid passage rate and VFA concentrations.

Transition cow nutrition and management strategies of dairy herds in the northeastern United States: Part II-Associations of metabolic- and inflammation-related analytes with health, milk yield, and reproduction.

The objectives were as follows: (1) establish cow-level thresholds for prepartum nonesterified fatty acids (NEFA) and postpartum NEFA, ß-hydroxybutyrate (BHB), and haptoglobin (Hp) concentrations associated with negative health events; (2) evaluate cow-level associations between biomarkers and 305-d mature equivalent milk at the fourth test day (ME305) and reproductive performance; and (3) identify herd-alarm levels (proportion of cows sampled above the critical threshold) for biomarkers that are associated with herd-level changes in disorder incidence (displaced abomasum and clinical ketosis), reproductive performance, and ME305. In a prospective cohort study, 1,473 cows from 72 farms were enrolled from the northeastern United States. Blood samples were collected from the same 11 to 24 cows per herd during the late-prepartum and early-postpartum periods. Whole blood was analyzed for postpartum BHB concentrations; plasma was analyzed for prepartum and postpartum NEFA and postpartum Hp concentrations. Critical thresholds for the biomarkers associated with health events for all cows were established using a receiver operating characteristic curve analysis. Poisson, linear mixed effects, and Cox proportional hazards models investigated the association of the biomarkers with health and performance. The prepartum NEFA and Hp threshold associated with culling was ≥0.17 mmol/L and 0.45 g/L, respectively. The postpartum NEFA and BHB thresholds associated with diagnosis of metritis, displaced abomasum, or clinical ketosis were ≥0.46 mmol/L and ≥0.9 mmol/L, respectively. Multiparous cows with prepartum NEFA concentration ≥0.17 mmol/L produced 479 kg less ME305. Multiparous and primiparous cows with postpartum NEFA concentration ≥0.46 mmol/L produced 280 kg less and 446 kg more ME305, respectively. Cows with BHB concentration ≥0.9 and ≥1.1 mmol/L produced 552 kg more ME305 and had a 20% decreased risk of pregnancy within 150 d in milk, respectively; however, multiparous cows with BHB concentration ≥1.5 mmol/L produced 376 kg less ME305. Cows with Hp concentration ≥0.45 g/L produced 492 kg less ME305 and had 28% decreased risk of pregnancy within 150 DIM. Cows with Hp concentration ≥0.45 g/L had 19% decreased pregnancy risk to first service (PRFS). Herds above the herd-alarm levels for prepartum NEFA had a 6.0-percentage unit increase in disorder incidence and a 6.0-percentage unit decrease in 21-d pregnancy rate (PR) for multiparous cows, a 3.9-percentage unit increase in PR and a 5.8-percentage unit increase in the probability of pregnancy for primiparous cows. Herds above the herd-alarm levels for postpartum NEFA had a 5.8- and 4.2-percentage unit increase in disorder incidence for multiparous and primiparous cows, respectively, a 789 kg decrease in ME305 for multiparous cows, and a 6.8- and 6.3-percentage unit decrease and increase in PR and PRFS for multiparous cows, respectively. Herds above the herd-alarm levels for BHB had an 8.5-percentage unit increase in disorder incidence, a 332 and 229 kg increase in ME305 for primiparous and multiparous cows, respectively, and a 3.2-, 5.2-, and 7.0-percentage unit decrease in PR, probability of pregnancy, and PRFS, respectively. Herds above the herd-alarm levels for postpartum Hp had a 5.3-percentage unit increase in disorder incidence. At the cow level and herd level, elevated biomarker concentrations were associated with an increased disorder risk and varied performance responses.

Effects of prepartum diets varying in dietary energy density and monensin on early-lactation performance in dairy cows.

Our objectives were to evaluate the effects of prepartum monensin supplementation and dry-period nutritional strategy on the postpartum productive performance of cows fed monensin during lactation. A total of 102 Holstein cows were enrolled in the experiment (32 primiparous and 70 multiparous). The study was a completely randomized design, with randomization restricted to balance for parity, body condition score, and expected calving date. A 2 × 2 factorial arrangement of prepartum treatments was used; the variables of interest were prepartum feeding strategy [controlled-energy diet throughout the dry period (CE) vs. controlled-energy diet from dry-off to 22 d before expected parturition, followed by a moderate-energy close-up diet from d 21 before expected parturition through parturition (CU)] and prepartum monensin supplementation [0 g/t (control, CON) or 24.2 g/t (MON); Rumensin; Elanco Animal Health, Greenfield, IN]. Lactation diets before and after the dry period contained monensin at 15.4 g/t. During the close-up period, cows fed CU had greater DM and NEL intakes than cows fed CE. Calf BW at birth tended to be greater for cows fed CU than for those fed CE but was not affected by MON supplementation. Diet did not affect calving difficulty score, but cows supplemented with MON had an increased calving difficulty score. We found a tendency for a MON × parity interaction for colostral IgG concentration, such that multiparous MON cows tended to have lower IgG concentration than CON cows, but colostral IgG concentration for primiparous MON and CON cows did not differ. Postpartum milk yield did not differ between diets but tended to be greater for cows supplemented with MON. Milk fat and lactose content were greater for cows fed CU than for those fed CE, and lactose content and yield were increased for cows supplemented with MON. Solids-corrected and fat-corrected milk yields were increased by MON supplementation, but were not affected by diet. Overall means for postpartum DMI did not differ by diet or MON supplementation. The CU diet decreased the concentration of nonesterified fatty acids during the close-up period but increased it postpartum. Neither diet nor monensin affected ß-hydroxybutyrate or liver composition. Overall, postpartum productive performance differed little between prepartum dietary strategies, but cows fed MON had greater energy-corrected milk production. In herds fed monensin during lactation, monensin should also be fed during the dry period.

Effect of monensin in lactating dairy cow diets at 2 starch concentrations.

The objective of this study was to determine the effects of monensin (M) supplementation on lactation performance of dairy cows fed diets of either reduced (RS) or normal (NS) starch concentrations as total mixed rations. One hundred twenty-eight Holstein and Holstein × Jersey cows (90 ± 33 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each in a randomized controlled trial. Pens were then randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments. A 4-wk covariate adjustment period preceded the treatment period, with all pens receiving NS supplemented with 18 g of monensin/t of dry matter (DM). Following the 4-wk covariate adjustment period, cows were fed their assigned treatment diets of NS with M (18 g of monensin/t), NS with 0 g of monensin/t (C), RS with M, or RS with C for 12 wk. Actual starch concentrations for the RS and NS diets were 20.4 and 26.9% (DM basis), respectively. Mean dry matter intake (DMI; 27.0 kg/d) was unaffected by the treatments. Feeding M compared with C and NS compared with RS increased milk yield by 1.3 and 1.5 kg/d per cow, respectively. Milk protein percentage and yield and lactose yield were increased and milk urea nitrogen was decreased for NS compared with RS. Feeding M increased actual and component-corrected milk feed efficiencies (component-corrected milk yield/DMI) and lactose yield and tended to increase milk urea nitrogen compared with C. Milk protein percentage was decreased for M compared with C, but milk fat percentage and yield, protein yield, and lactose percentage were unaffected by M. We observed a tendency for a starch × monensin interaction for milk feed efficiency (actual milk yield/DMI); M tended to increase efficiency more for NS than for RS. Starch and monensin had minimal effects on milk fatty acid composition and yields. Feeding RS decreased milk and protein yields, but component-corrected milk yields and feed efficiencies were similar for RS and NS. Monensin increased feed efficiency and lactation performance for both dietary starch concentrations.

Effects of monensin on metabolic parameters, feeding behavior, and productivity of transition dairy cows.

The effects of monensin on transition cow metabolism may be dependent on modulation of feeding behavior, rumen pH, and expression of key metabolic genes. Multiparous Holstein cows were used to determine the effects of monensin (400mg/cow daily) on these variables. Cows were randomly assigned, based on calving date, to control or monensin treatments (n = 16 per treatment) 21 d before their expected calving date, and cows remained on treatments through 21 d postpartum. Feeding behavior and water intake data were collected daily. Liver biopsies were conducted after assessing BCS and BW on d -21, -7, 1, 7, and 21 relative to calving for analysis of triglyceride (TG) content as well as mRNA abundance of cytosolic phosphoenolpyruvate carboxykinase, carnitine palmitoyltransferase 1a, and apolipoprotein B. Blood samples were collected 21, 7, and 4 d before expected calving and 1 (day of calving), 4, 7, 14, and 21 d postpartum for nonesterified fatty acid, ß-hydroxybutyrate, glucose, insulin, and haptoglobin analyses. Ruminal pH was collected every 5 min on d 1 through 6 postpartum via a wireless indwelling probe. On d 7 postpartum, a caffeine clearance test was performed to assess liver function. Data were analyzed using mixed models with repeated measures over time. Monensin decreased mean plasma ß-hydroxybutyrate (734 vs. 616 ± 41 µM) and peak concentrations (1,076 vs. 777 ± 70 µM on d 4 postpartum). Monensin also decreased time between meals prepartum (143 vs. 126 ± 5.0 min) and postpartum (88.8 vs. 81.4 ± 2.9 min), which was likely related to a smaller ruminal pH standard deviation in the first day after cows changed to a lactation ration (0.31 vs. 0.26 ± 0.015). Monensin also increased liver mRNA abundance of carnitine palmitoyltransferase 1a (0.10 vs. 0.15 ± 0.002 arbitrary units), which corresponded to a slower rate of liver TG accumulation from d -7 to +7 (412 vs. 128 ± 83 mg of TG/g of protein over this time period). No significant effects of monensin supplementation were observed on milk production, liver cytosolic phosphoenolpyruvate carboxykinase, apolipoprotein B, plasma nonesterified fatty acid, glucose, insulin, or haptoglobin. No effects on disease incidence were detected, but sample size was small for detecting such effects. Overall, results confirm that the effects of monensin on transition cows extend beyond altered propionate flux.

Effect of dietary fat blend enriched in oleic or linoleic acid and monensin supplementation on dairy cattle performance, milk fatty acid profiles, and milk fat depression.

The effect of feeding increasing levels of oleic and linoleic acid both independently and together, with or without monensin, on milk fat depression was evaluated. Fifty-six Holstein cows were blocked by parity and then were divided by milk production into 2 groups (high or low) of 14 cows each within each parity block. A cow pair of 1 high and 1 low production cow within each parity block was fed in a single electronic feeding gate. Gates (n = 28) were considered the experimental unit and were assigned to monensin (17.5 g/t of dry matter) or control as the main plot (n = 14 each). The 7 cow pairs in each of the fixed effect groups were further assigned to a sequence of fat blend diets as split plot. Seven fat blend treatments in the split plot 7 × 7 Latin square were no added fat (no fat) and diets with increasing levels of oleic or linoleic acid: low C18:1 + low C18:2 (LOLL); low C18:1 + medium C18:2 (LOML); low C18:1 + high C18:2 (LOHL); medium C18:1 + low C18:2 (MOLL); medium C18:1+medium C18:2 (MOML); and high C18:1+low C18:2 (HOLL). Monensin feeding did not affect milk yield or concentration and yield of milk fat. Feeding monensin decreased the proportion of C <16, increased the proportion of total C18, increased the proportion and yield of trans-10 C18:1, and increased the proportion of trans-10,cis-12 conjugated linoleic acid in milk fatty acids (FA). As dietary C18:1 or C18:2 increased beyond the concentration present in LOLL, milk fat concentration, milk fat yield, and proportion and yield of milk C <16 all decreased, and the proportion and yield of milk trans-10 C18:1 increased. A quadratic effect on milk fat concentration and yield was noticed for C18:2 feeding, but not for C18:1 feeding. When dietary contents of total FA and FA other than C18:1 and C18:2 were similar, C18:2-rich diets decreased milk fat concentration and yield compared with C18:1-rich diets (LOML vs. MOLL, and LOHL vs. HOLL), indicating that C18:2 is more potent than C18:1 for depressing milk fat. Increasing dietary FA content from no fat to LOLL, which increased primarily C18:1 and C18:2 with small increases in C18:0 and C16:0, decreased the secretion of C <16 but increased total C18 secretion in milk. This suggests that biohydrogenation intermediates act to decrease mammary FA synthesis at low levels of added C18:1 and C18:2. No significant monensin × fat interactions were detected for the milk composition parameters analyzed; however, a monensin × fat interaction was found for milk fat trans-10 C18:1 proportion.

Effects of prepartum 2,4-thiazolidinedione on insulin sensitivity, plasma concentrations of tumor necrosis factor-α and leptin, and adipose tissue gene expression.

Administration of peroxisome proliferator-activated receptor gamma (PPARγ) ligands, thiazolidinediones (TZD), to prepartum dairy cattle has been shown to improve dry matter intake and decrease circulating nonesterified fatty acids (NEFA) around the time of calving. The objective of this work was to elucidate mechanisms of TZD action in transition dairy cattle by investigating changes in plasma leptin, tumor necrosis factor-α (TNFα), the revised quantitative insulin sensitivity check index (RQUICKI), and adipose tissue gene expression of leptin, PPARγ, lipoprotein lipase (LPL), and fatty acid synthase (FAS). Multiparous Holstein cows (n=40) were administered 0, 2.0, or 4.0 mg of TZD/kg of body weight (BW) by intrajugular infusion once daily from 21 d before expected parturition until parturition. Plasma samples collected daily from 22 d before expected parturition through 21 d postpartum were analyzed for glucose, NEFA, and insulin. Plasma samples collected on d -14, -3, -1, 1, 3, 7, 14, and 49 relative to parturition were also analyzed for leptin and TNFα. Adipose tissue was collected on d 7 before expected parturition from a subset of cows, and gene expression was examined via quantitative real-time PCR. A tendency for a treatment by time effect on plasma leptin prepartum was observed such that values were similar on d -14 but cows receiving 2.0 mg/kg of BW of TZD tended to have lower circulating leptin as calving approached. Postpartum leptin tended to be increased linearly (2.3, 2.4, and 2.5±0.1 ng/mL for 0, 2.0, and 4.0 mg/kg treatments, respectively) in cows that received TZD prepartum. Plasma TNFα increased linearly (2.6, 3.7, and 4.0±0.1 pg/mL) in response to TZD treatment and decreased through the first week postpartum. Calculation of RQUICKI 1/[log(glucose)+log(insulin)+log(NEFA)] suggested altered insulin sensitivity in cows administered TZD that may depend on day relative to calving. Administration of TZD increased adipose tissue expression of PPARγ mRNA (11.0, 13.3, and 12.8±1.9). Administration of TZD had a quadratic effect on gene expression of leptin (16.2, 10.7, and 17.4±1.6) and no effect on LPL expression, and expression of FAS was lower for TZD-treated cows than for controls (8.2, 4.2, and 6.1±1.8, respectively). Results imply altered expression and plasma concentrations of leptin, increased plasma TNFα concentrations, and increased expression of PPARγ in adipose tissue as potential mechanisms for the effects of TZD administration on transition dairy cattle.