Interaction of DGAT1 polymorphism, parity, and acetate supplementation on feeding behavior, milk synthesis, and plasma metabolites.

Acetate supplementation increases milk fat production, but interactions with animal-related factors have not been investigated. The objective of this study was to characterize the interaction of acetate supplementation with parity and genetic potential for milk fat synthesis including the DGAT1 K232A polymorphism (AA and KA genotypes). In total, 47 primiparous and 49 multiparous lactating cows were used in 2 blocks in a crossover design. The basal diet was formulated to have a low risk of biohydrogenation-induced milk fat depression and had 32.8% and 32.0% neutral detergent fiber and 21.7% and 23.6% starch [all on a dry matter (DM) basis] in block 1 and 2, respectively. The control treatment received the basal diet, and the acetate supplementation treatment included anhydrous sodium acetate supplemented to the basal diet at 3.2% and 3.1% of DM of the diet for block 1 and 2, respectively (targeting 10 mol/d of acetate). The DGAT1 genotype frequency of the experimental cows was 45% AA and 51% KA, with 4% cows with either a KK or unimputable genotype. Acetate supplementation increased DM intake (DMI) in KA multiparous cows, but acetate did not change DMI in AA multiparous or primiparous cows of either genotype. Acetate supplementation increased the frequency of meals by 8% and decreased the length of each meal by ∼5 min compared with control. There was no effect of acetate on milk yield. Acetate supplementation increased milk fat yield and concentration by 117 g/d and 0.31 percentage units, respectively, regardless of DGAT1 polymorphism or parity. The increase in milk fat yield was mostly due to an increase in yield of 16C mixed-sourced fatty acids, suggesting that acetate supplementation drives mammary de novo synthesis toward completion. Response to acetate supplementation was not related to genomic predicted transmitting ability of milk fat concentration and yield or to pretrial milk fat percent and yield, suggesting that acetate increases milk fat production regardless of genetic potential for milk fat yield and level of milk fat synthesis. Interestingly, analyzing the temporal effect on the interaction between treatment and DGAT1 polymorphism on milk fat yield suggested that DGAT1 polymorphism may affect the short-term response to acetate supplementation during the first ≤7 d on treatment. Acetate supplementation also increased plasma ß-hydroxybutyrate concentration and decreased plasma glucose concentration. In conclusion, acetate supplementation consistently increased milk fat synthesis regardless of parity or genetic potential for milk fat synthesis.

Serum metabolomics assessment of etiological processes predisposing ketosis in water buffalo during early lactation.

Metabolic disorders as ketosis are manifestations of the animal's inability to manage the increase in energy requirement during early lactation. Generally, buffaloes show a different response to higher metabolic demands than other ruminants with a lower incidence of metabolic problems, although ketosis is one of the major diseases that may decrease the productivity in buffaloes. The aim of this study was to characterize the metabolic profile of Mediterranean buffaloes (MB) associated with 2 different levels of ß-hydroxybutyrate (BHB). Sixty-two MB within 50 days in milk (DIM) were enrolled and divided into 2 groups according to serum BHB concentration: healthy group (37 MB; BHB <0.70 mmol/L; body condition score: 5.00; parity: 3.78; and DIM: 30.70) and group at risk of hyperketonemia (25 MB; BHB ≥0.70 mmol/L; body condition score: 4.50; parity: 3.76; and DIM: 33.20). The statistical analysis was conducted by one-way ANOVA and unpaired 2-sample Wilcoxon tests. Fifty-seven metabolites were identified and among them, 12 were significant or tended to be significant. These metabolites were related to different metabolic changes such as mobilization of body resources, ruminal fermentations, urea cycle, thyroid hormone synthesis, inflammation, and oxidative stress status. These findings are suggestive of metabolic changes related to subclinical ketosis status that should be further investigated to better characterize this disease in the MB.

Effect of the timing of sodium acetate infusion on the daily rhythms of milk synthesis and plasma metabolites and hormones in Holstein cows.

Dairy cows have a daily pattern of feed intake which influences ruminal fermentation and nutrient absorption. Milk synthesis also exhibits a daily rhythm and is altered by the timing of feed availability. Nutrients can regulate physiological rhythms, but it is unclear which specific nutrients affect the rhythms of milk synthesis in the cow. The objective of this study was to determine the effect of the timing of acetate infusion on the daily rhythms of feed intake, milk synthesis, milk fatty acids, plasma insulin and metabolites, and core body temperature. Ten lactating ruminally cannulated Holstein cows (127 ± 24.6 d in milk; mean ± standard deviation) were arranged in a 3 × 3 Latin square design. Treatments were ruminal infusions of 600 g/d of acetate either continuously throughout the day (CON) or over 8 h/d during the day (day treatment, DT; 0900 to 1700 h) or the night (night treatment, NT; 2100 to 0500 h). Experimental periods were 14 d with a 7-d washout between periods. Cows were milked every 6 h during the final 7 d of each experimental period to determine the daily pattern of milk synthesis. Blood samples were taken to represent every 4 h across the day and plasma glucose, insulin, ß-hydroxybutyrate, urea nitrogen, and acetate concentration were measured. An intravaginal temperature logger was used to measure core body temperature. Data were analyzed with cosinor-based rhythmometry to test the fit of a cosine function with a period of 24 h and to determine the acrophase (time at peak) and amplitude (peak to mean) of each rhythm. Milk yield fit a daily rhythm for all treatments and DT and NT phase-delayed the rhythm and DT increased the robustness of the rhythm. Milk protein concentration fit a daily rhythm for all treatments and DT increased robustness, whereas NT phase-delayed the rhythm. Plasma acetate concentration also fit a daily rhythm in all treatments. Plasma acetate peaked at ∼1600 h in CON and DT and at 0053 h in NT, reflecting the timing of treatment infusions. There was a daily rhythm in plasma ß-hydroxybutyrate that reflected the plasma acetate rhythm. Core body temperature fit a rhythm for all treatments, but the amplitude of the rhythm was smaller than previously observed. In conclusion, the timing of acetate infusion influences peripheral rhythms of milk synthesis and plasma metabolites.

Interaction of sodium acetate supplementation and dietary fiber level on feeding behavior, digestibility, milk synthesis, and plasma metabolites.

Acetate supplementation has been shown to increase milk fat yield in diets with low risk of biohydrogenation-induced milk fat depression. The interaction of acetate supplementation with specific dietary factors that modify rumen fermentation and short-chain fatty acid (FA) synthesis has not been investigated. The objective of this experiment was to determine the effect of acetate supplemented as sodium acetate at 2 dietary fiber levels. Our hypothesis was that acetate would increase milk fat production more in animals fed the low-fiber diet. Twelve lactating multiparous Holstein cows were arranged in a 4 × 4 Latin square design balanced for carryover effects with a 2 × 2 factorial arrangement of dietary fiber level and acetate supplementation with 21-d experimental periods. The high-fiber diet had 32% neutral detergent fiber and 21.8% starch, and the low-fiber diet had 29.5% neutral detergent fiber and 28.7% starch created by substitution of forages predominantly for ground corn grain. Acetate was supplemented in the diet at an average 2.8% of dry matter (DM) to provide approximately 10 mol/d of acetate as anhydrous sodium acetate. Acetate supplementation increased DM intake by 6%, with no effect on meal frequency or size. Furthermore, acetate supplementation slightly increased total-tract apparent DM digestibility and tended to increase organic matter digestibility. Acetate supplementation increased milk fat concentration and yield by 8.6 and 10.5%, respectively, but there was no interaction with dietary fiber. The increase in milk fat synthesis was associated with 46 and 85 g/d increases in the yield of de novo (<16C) and mixed source (16C) FA, respectively, with no changes in yield of preformed FA (>16C). There was a 9% increase in the concentration of milk mixed-source FA and a 7% decrease in milk preformed FA with acetate supplementation, regardless of dietary fiber level. Acetate supplementation also increased the concentrations of plasma acetate and ß-hydroxybutyrate, major metabolic substrates for mammary lipogenesis. Overall, acetate supplementation increased milk fat yield regardless of dietary fiber level through an increase mostly caused by an increase in longer-chain de novo FA, suggesting stimulation of mammary lipogenesis. The heightened mammary de novo lipogenesis was supported by an increase in the concentration of metabolic substrates in plasma.

Effect of 2-hydroxy-4-(methylthio)butanoate (HMTBa) on milk fat, rumen environment and biohydrogenation, and rumen protozoa in lactating cows fed diets with increased risk for milk fat depression.

Biohydrogenation-induced milk fat depression (MFD) is a reduction in milk fat synthesis caused by bioactive fatty acids (FA) produced during altered ruminal microbial metabolism of unsaturated FA. The methionine analog 2-hydroxy-4-(methylthio)butanoate (HMTBa) has been shown to reduce the shift to the alternate biohydrogenation pathway and maintain higher milk fat yield in high-producing cows fed diets lower in fiber and higher in unsaturated FA. The objective of this experiment was to verify the effect of HMTBa on biohydrogenation-induced MFD and investigate associated changes in rumen environment and fermentation. Twenty-two rumen cannulated high-producing Holstein cows [168 ± 66 d in milk; 42 ± 7 kg of milk/d (mean ± standard deviation)] were used in a randomized design performed in 2 blocks (1 = 14 cows, 2 = 8 cows). Treatments were control (corn carrier) and HMTBa (0.1% of diet dry matter). The experiment included a 7-d covariate period followed by 3 phases that fed diets with increasing risk of MFD. The diet during the covariate and low-risk phase (7 d) was 32% neutral detergent fiber with no additional oil. The diet during the moderate-risk phase (17 d) was 29% neutral detergent fiber with 0.75% soybean oil. Soybean oil was increased to 1.5% for the last 4 d. The statistical model included the random effect of block and time course data were analyzed with repeated measures including the random effect of cow and tested the interaction of treatment and time. There was no effect of block or interaction of block and treatment or time. There was no overall effect of treatment or treatment by time interaction for dry matter intake, milk yield, and milk protein concentration and yield. Overall, HMTBa increased milk fat percent (3.2 vs. 3.6%) and yield (1,342 vs. 1,543 g/d) and there was no interaction of treatment and dietary phase. Additionally, HMTBa decreased the concentration of trans-10 18:1 in milk fat and rumen digesta. Average total ruminal concentration of volatile FA across the day and total-tract dry matter and fiber digestibility were not affected by HMTBa, but HMTBa increased average rumen butyrate and decreased propionate concentration and increased total protozoa abundance. Additionally, HMTBa increased the fractional rate of α-linoleic acid clearance from the rumen following a bolus predominantly driven by a difference in the first 30 min. Plasma insulin was decreased by HMTBa. In conclusion, HMTBa prevented the increase in trans FA in milk fat associated with MFD through a mechanism that is independent of total volatile FA concentration, but involves modification of rumen biohydrogenation. Decreased propionate and increased butyrate and ruminal protozoa may also have functional roles in the mechanism.

In vivo kinetics of oleic, linoleic, and α-linolenic acid biohydrogenation in the rumen of dairy cows.

Ruminal biohydrogenation (BH) of unsaturated fatty acids (FA) reduces absorption of essential FA and can result in formation of bioactive FA that cause milk fat depression. Rates of biohydrogenation of unsaturated FA are commonly observed using in vitro systems and are not well described in vivo. Seven ruminally cannulated cows were enrolled in a 3 × 3 Latin square design study to quantify biohydrogenation of 18:1n-9, 18:2n-6, and 18:3n-3 using a recently developed in vivo BH assay. All cows were fed a common high corn silage basal diet. Biohydrogenation was quantified using a perturbation model that consisted of a bolus dose of 200 g of an oil enriched in each unsaturated FA (oleic acid, OA = 87% 18:1n-9 sunflower oil; linoleic acid, LA = 70% 18:2n-6 safflower oil; and α-linolenic acid, ALA = 54% 18:3n-3 flaxseed oil) and 12 g of 17:0 as a marker of rumen outflow. Rumen contents were sampled before and after the bolus and enrichment of the bolused FA modeled. Using first-order kinetics to model FA disappearance, the fractional rates of disappearance of 18:1n-9 was 0.597 per hour, 18:2n-6 was 0.618 per hour, and 18:3n-3 was 0.834 per hour, similar to rates previously reported with this approach. Rumen turnover of 17:0 was 0.123 per hour, 0.065 per hour, and 0.106 per hour during the OA, LA, and ALA treatments, respectively. The extents of BH were calculated to be 82.8, 90.4, and 88.6% for 18:1n-9, 18:2n-6, and 18:3n-3, respectively. Finally, compartmental modeling was used to quantify the amount of each unsaturated FA metabolized through trans-10 and trans-11 BH pathways. The recently developed in vivo BH assay was able to predict rates of BH and provide insight into rumen metabolism of individual FA and may be useful to future investigations.

The diurnal patterns of ruminal enzymatic activity and in vitro digestibility of starch, neutral detergent fiber, and protein.

The objective of this study was to determine whether diurnal patterns in starch, neutral detergent fiber (NDF) and protein digestibilities and amylolytic, fibrolytic, and proteolytic activities exist in dairy cows. Rumen fluid was collected from 4 ruminally cannulated Holstein dairy cows before the morning feeding and subsequently every 4 h for a 24-h period. Two of the cows were restricted from feed for 8 h overnight, and the other 2 continued to receive their feed ad libitum, to isolate and quantify the effects of changes in feeding behavior at night. After 2 runs the cows were crossed over between night feeding treatments. Rumen fluid was analyzed for enzymatic activity and in vitro starch, NDF, and nitrogen digestibility. Circadian rhythm analyses of enzymatic activity and in vitro digestibility were conducted by fitting the linear form of a cosine function with a 24-h period. Patterns were observed in activity for amylase, lichenase, endoglucanase, and xylanase, with the highest activities observed at the time points subsequent to milking and feed delivery. Protease activity was unaffected by either feeding treatment or possible feeding behavior. When fitted to a cosine function, all the parameters tested followed a daily pattern that was sensitive to the overnight availability of feed, although the parameters responded differently to the feeding treatment. The patterns displayed by in vitro digestibility results of starch, NDF, and nitrogen, across the various fluid collection time points, were highly variable. The time at peak (acrophase) observed in the enzymatic analysis did not correspond to those observed in the in vitro analysis. These results suggest that different interpretations should be given to enzymatic activities and in vitro digestibility values, and the time of rumen fluid collection relative to feeding time should be considered and reported when rumen fluid is used for research or commercial purposes. Maximum digestibility appears in fact to be reached around 4 to 5 h after the main ration delivery for NDF and starch and around ration delivery for protein.

Effects of fat supplements containing different levels of palmitic and stearic acid on milk production and fatty acid digestibility in lactating dairy cows.

Fat supplements based on palmitic acid (PA) or stearic acid (SA) are expected to have different effects on milk production and nutrient metabolism in lactating dairy cows. In this study, the effects of prilled fat supplements containing different levels of PA and SA were tested in 12 high-producing multiparous cows (pretrial milk yield = 53.4 ± 8.7 kg/d; mean ± SD) arranged in a 4 × 4 Latin square design with 21-d periods. Treatments were control (CON; no supplemental fat), an enriched PA supplement (HP; 91% C16:0), an enriched SA supplement (HS; 92.5% C18:0), and a blend of PA and SA (INT) fed at 1.95% of diet dry matter. All supplements contained oleic acid at approximately 5% of fatty acids. The HP treatment decreased dry matter intake (DMI) by 1.9 kg/d and 1.1 kg/d compared with SA and CON, respectively. Milk yield was not changed by treatment, but INT increased energy-corrected milk by 2.7 kg/d compared with HS. The HP and INT treatments increased milk fat yield by 0.11 and 0.14 kg/d compared with CON, respectively. Additionally, HP decreased yield of <16 carbon fatty acids (FA; de novo synthesized) by 44 g/d and 43 g/d compared with INT and CON, respectively. The HP treatment increased 16-carbon FA (mixed source) by 155 g/d compared with CON and 64 g/d relative to INT. No effect of treatment on apparent total-tract digestibility of dry matter, organic matter, or neutral detergent fiber was detectable. The INT and HS treatments decreased total-tract digestibility of 16-carbon FA by 10.3 and 10.5 percentage units compared with HP, respectively. Total-tract digestibility of 18-carbon FA was lowest in the HS diet and highest with HP. In conclusion, supplementing PA increased milk fat yield compared with control and SA, but supplementing a mixture of PA and SA increased energy-corrected milk without decreasing intake. The FA profile of fat supplements influences their digestibility and effects on DMI and milk and milk fat synthesis.

Comparison of the effects of short-term feeding of sodium acetate and sodium bicarbonate on milk fat production.

Supplementation with sodium acetate (NaAcet) increases milk fat production through an apparent stimulation of de novo lipogenesis in the mammary gland. Sodium acetate increases acetate supply to the mammary gland, but it also increases dietary cation-anion difference, which can also increase milk fat yield. The objective of this study was to determine if the effect of NaAcet on milk fat production was due to an increase in acetate supply or an increase in dietary cation-anion difference. The study included 12 multiparous cows in a replicated 3 × 3 Latin square design balanced for carryover effects, with 14-d experimental periods. Treatments were a basal total mixed ration (31.8% neutral detergent fiber, 14.8% crude protein, 25.5% starch, and 4.4% fatty acids on a dry matter basis) as a no-supplement control, acetate supplemented at 3.25% of dry matter as NaAcet, and sodium bicarbonate (NaHCO3) providing an equal amount of sodium to the NaAcet treatment. The NaAcet and NaHCO3 were mixed into the basal diet before feeding. Milk samples were taken at each milking during the last 3 d of each period. Plasma samples were taken every 9 h during the last 3 d (a total of 8 times) to determine concentrations of plasma metabolites and hormones. Eating behavior was monitored during the last week of each period using an automated system. The NaAcet and NaHCO3 treatments increased milk fat concentration and yield compared to the no-supplement control. The NaAcet treatment increased milk fat production predominantly by increasing the yield of de novo and mixed-source fatty acids. The NaHCO3 treatment increased the yield of preformed and de novo fatty acids, suggesting different mechanisms for the 2 treatments. The NaAcet treatment increased plasma acetate concentration in a period of the day concurrent with the highest dry matter intake. The NaAcet treatment increased milk fat production by stimulating the production of de novo fatty acids, a mechanism consistent with previous reports, possibly by increasing acetate supply to the mammary gland. The NaHCO3 treatment increased milk fat production by increasing the production of all biological categories of fatty acids, except for odd and branched-chain fatty acids, possibly by increasing overall diet digestibility.

Determination of relationships between rumination and milk fat concentration and fatty acid profile using data from commercial rumination sensing systems.

Milk fat production is highly influenced by nutrition and rumen fermentation. Rumination is an essential part of the ruminant digestive process and can serve as an indicator of rumen fermentation. The objective of this research was to quantify variation in rumination time between and within dairy herds and test for relationships between rumination time and milk fat production and fatty acid (FA) profile as a proxy of rumen fermentation. Our hypothesis was that rumination may indicate disruptions to rumen fermentation and that cows that spent less time ruminating would have lower milk fat due to these rumen disruptions. Data were collected from 1,733 Holstein cows on 5 commercial dairy farms (4 in Pennsylvania and 1 in New York) of 200 to 700 head using 1 of 2 commercially-available rumination sensing systems, CowManager SensOor ear tags (Agis Automatisering BV) or SCR model HR-LDn neck collars (SCR Engineers). Rumination data were collected for 7 consecutive days leading up to a DHIA test, summed within day, then averaged to obtain mean daily minutes of rumination time. Milk samples from the DHIA test were analyzed for fat content by mid-infrared spectroscopy and for milk FA profile by gas chromatography. Rumination data were analyzed using multiple linear regression models. Rumination time was related to concentration of specific odd- and branched-chain and trans FA in milk but was not directly related to milk fat concentration. Rumination time also did not contribute to models predicting milk fat concentration after accounting for other cow-level variables. There was a linear relationship between trans-10 C18:1 and rumination time that was positive after accounting for the effect of farm (partial R2 of 2.97% across all data, 4.24% in SCR data, and 2.22% in CowManager data). Although rumination time was not related directly to milk fat, it was associated with differences in trans and odd- and branched-chain FA that have been demonstrated to change during subacute ruminal acidosis or biohydrogenation-induced milk fat depression, which may affect milk fat and other production variables. These associations suggest that further investigation into using rumination data from commercial systems to predict or identify the presence of these conditions is warranted.

Trans-10, cis-12 conjugated linoleic acid reduces milk fat content and lipogenic gene expression in the mammary gland of sows without altering litter performance.

Trans-10, cis-12 conjugated linoleic acid (CLA) decreases milk fat synthesis in lactating sows and involves, at least in part, the down-regulation of lipogenic genes. The objective was to evaluate the effect of CLA on milk composition and lipogenic gene expression. Twenty multiparous sows were randomly assigned to one of the two treatments for 18 d (from day 7 to day 25 of lactation): (1) control (no CLA added) and (2) 1 % of CLA mixed into the ration. CLA treatment decreased milk fat and protein content by 20 % (P = 0·004) and 11 % (P = 0·0001), respectively. However, piglet weight did not differ between treatments (P = 0·60). Dietary CLA increased the concentration of SFA in milk fat by 16 % (P < 0·0001) and decreased MUFA by 17·6 % (P < 0·0001). In the mammary gland, CLA reduced gene expression of acetyl-CoA carboxylase-α by 37 % (P = 0·003), fatty acid synthase by 64 % (P = 0·002), stearoyl-CoA desaturase 1 by 52 % (P = 0·003), lipoprotein lipase by 26 % (P = 0·03), acyl glycerol phosphate acyltransferase 6 by 15 % (P = 0·02) and diacylglycerol acyltransferase 1 by 27 % (P = 0·02), whereas the expression of fatty acid binding protein 3 was not altered by CLA treatment (P = 0·09). Mammary expression of casein-ß and α-lactalbumin was reduced by CLA by 68 % (P = 0·0004) and 62 % (P = 0·005), respectively. Additionally, CLA had no effect on the expression of lipogenic genes evaluated in adipose tissue. In summary, CLA reduced milk fat content without negatively affecting litter performance and it affected mammary expression of genes involved in all lipogenic pathways studied.

Meta-analysis of the relationship between milk trans-10 C18:1, milk fatty acids <16 C, and milk fat production.

The economic value of milk fat and its responsiveness to management strategies provides strong interest in maximizing milk fat production by minimizing occurrence of biohydrogenation-induced milk fat depression (BH-MFD) and maximizing de novo synthesized fatty acids (FA). Tools that allow a timely diagnosis of BH-MFD would improve nutritional management. Specific milk FA or FA categories correlate to milk fat concentration and are of interest for diagnosing the cause of changes in milk fat concentration. The objective of the current study was to characterize the relationship between milk fat concentration and trans-10 C18:1, a proxy for BH-MFD, and FA <16 carbons that originate solely from de novo lipogenesis using a meta-analysis approach that used data from the literature and unpublished Penn State experiments. Prior to the meta-analysis, the effect of FA methylation method on milk FA profile was tested to determine potential bias between papers. There was no difference between sodium methoxide, acid, and acid-base methylation methods on trans-10 C18:1 concentration, but acid methods resulted in loss of short-chain FA. The relationship between trans-10 C18:1 and milk fat percentage was investigated using a 2-component model, where one component described the fraction unresponsive to BH-MFD and the other described a responsive fraction that is exponentially related to trans-10 C18:1. The 2 fractions where characterized utilizing a Bayesian hierarchical model accounting for between-study variability. The model was defined by the function f(x, θ1, θ2, θ3) = θ1 + θ2exp(θ3), where the unresponsive θ1 fraction was 2.15 ± 0.09%, the responsive θ2 fraction was 1.55 ± 0.08%, and the exponential term θ3 was -0.503 ± 0.07 (posterior mean ± posterior standard deviation from the Bayesian hierarchical model). A Lin's concordance correlation coefficient of 0.67 suggested good agreement between observations and predictions from the Bayesian hierarchical model, computed only with the model's mean population parameters. There was a linear relationship between milk fat concentration and FA <16 C as a percentage of total FA (intercept = 2.68 ± 0.237 and slope = 0.043 ± 0.011; coefficient of determination = 0.31). The relationship between milk FA <16 C and milk fat concentration is weaker than what has been published, likely because multiple factors can reduce de novo FA without reducing milk fat and the broad range of diets present in the literature.

Annual rhythms of milk synthesis in dairy herds in 4 regions of the United States and their relationships to environmental indicators.

The annual rhythms of milk and milk component yields are not well described and are important to dairy management. Recent analysis of federal milk marketing orders in the United States observed that the amplitude and time at peak (acrophase) of the rhythms of milk fat and protein concentration differ among regions, but the rhythms of milk and milk component yields are not well described. Our objective was to determine the annual rhythms of milk and milk component production from 4 US regions at the herd level and examine potential environmental factors entraining these rhythms. Monthly Dairy Herd Improvement Association records of all available herds in Pennsylvania (PA), Minnesota (MN), Texas (TX), and Florida (FL) from the years 2003 to 2016 were obtained from Dairy Records Managements Systems. Milk yield, fat and protein yield, and fat and protein concentration were fit to the linear form of the cosine function with a 12-mo period using a linear mixed effects model. Additionally, the fit of models containing either the cosine function or environmental temperature were compared using an F-test. Milk yield and fat and protein yields and concentrations fit a cosine function in all 4 states, indicating an annual rhythm. The amplitude (peak to mean) of the rhythm of milk yield varied by state and was lower in PA (1.2 kg) and MN (1.2 kg) compared with TX (3.1 kg) and FL (3.3 kg). Fat and protein yields similarly showed greater amplitudes in the southern versus northern states. The amplitudes of the rhythms of fat and protein concentration were opposite by region, with greater amplitudes occurring in MN and PA than in TX and FL. The acrophases of milk yield and milk fat and protein yields and concentrations also varied by state, but all peaked between October and March. An annual rhythm fit the data better than changes in environmental temperature for all responses in all states, except for fat and protein concentrations in FL, which exhibited lower amplitude seasonal rhythms. The yearly pattern of milk yield closely followed the fixed yearly pattern of the day to day changes in day length, whereas the rhythms of milk fat and protein concentrations followed the yearly pattern of absolute day length. Results suggest that the region of the United States in which a herd is located affects their annual rhythms of production, with a greater yearly variation in milk, fat, and protein yields occurring in the southern United States. The consistency of annual rhythms across years and herds allowed development of regression equations to adjust expectations across the year to account for the annual rhythm.

Relationships between milk fat and rumination time recorded by commercial rumination sensing systems.

Low rumination in the dairy cow is often assumed to result in reduction of saliva flow, rumen buffering, and milk fat, which is a major contributor to milk value in many pricing systems. Rumination time (RT) of individual cows can be measured with commercial rumination sensing systems, but our understanding of how daily RT (minutes per day) is related to milk fat production is limited. Our hypothesis was that between cows within a herd, greater RT would be associated with lower milk fat concentration. Data from 1,823 cows on 2 commercial dairy farms in Pennsylvania over 8 DHIA tests were analyzed for a total of 8,587 cow test-days. Rumination was measured on farm A with CowManager SensoOr ear tags (Agis Automatisering BV, Harmelen, the Netherlands) and on farm B with SCR Hi-Tag neck collars (SCR Engineers, Netanya, Israel). Rumination data were collected for 7 consecutive days leading up to each DHIA test, summed within day, and averaged across days. Data were analyzed using linear mixed models with a repeated effect of test day. Daily RT reported by commercial rumination systems varied across and within cows and was strongly influenced by a cow effect. Greater RT tended to be associated with a small decrease in milk fat concentration in farm A, but was not related to milk fat in farm B. The reason for this difference is unclear, but may be related to a potentially greater prevalence of biohydrogenation-induced milk fat depression on farm A. The significant, but small, model coefficients for milk fat and RT indicate that the relationship between these variables may not be strong enough to permit identification of cows with biohydrogenation-induced milk fat depression based on RT from commercial systems alone. Research assessing changes in rumination before, during, and after onset of altered rumen fermentation is necessary to determine whether RT could be used to identify cows with altered rumen fermentation.

Technical note: Method for improving precision of in-parlor milk meters and adjusting milk weights for stall effects.

Milk yield is a fundamental observation in most dairy experiments and is commonly determined using integrated milk meters that measure milk weight as the cow is being milked. These meters are heavily used in a harsh environment and often are not regularly calibrated, so calibration errors and mechanical problems may create artificial variation in milk weight data. Additionally, direct calibration by collection of milk in a bucket is difficult and imperfect because the use of the bucket may affect yield recorded by the milk meter. The objective of this work was to define a method to easily check parlor meter precision and adjust milk weight values for variation between individual stalls in a parlor. Because most cows are milked in a different stall at each milking, it has been proposed that stall deviations that represent the fixed effect of stall on milk weight could be statistically determined. Individual milk weights from 14 milkings across 7 d from approximately 200 cows were collected from the Penn State dairy farm, which is equipped with a double-10 herringbone parlor with an Afimilk 2000 milking system (S.A.E. Afikim, Afikim, Israel). Milk yield was measured automatically by in-line flow through milk meters (Afi 200; S.A.E. Afikim). The effect of stall on milk weight was modeled using a mixed model that included the fixed effect of stall and the random effects of day, milking time, and cow. First, stall deviations were calculated as the stall least squares means (LSM) minus the average LSM to identify malfunctioning meters requiring service (e.g., deviation exceeding 1 kg). A correction factor for each stall was then generated by dividing the LSM of each stall by the average LSM. Milk yields were then corrected by multiplying the meter weight value by the correction factor. To determine the effect of the correction, raw and corrected meter values were compared with weight of milk collected in a bucket (n = 3/stall). The corrected values had a 5% greater coefficient of determination than raw meter values (0.89 vs. 0.84) and had a lower average percent difference from the bucket milk weight compared with raw meter values (12.6% vs. 13.5%). The method was then used in 3 experiments with 121, 140, and 683 milk yield observations. In all data sets, correcting milk weights slightly improved model fit and had minimal effect on model term standard errors. However, this validation was completed in a parlor where the method was routinely used to identify stalls requiring service; the effect of stall corrections is expected to be larger in parlors without frequent monitoring. Stall deviations are expected to be due predominantly to calibration of the meter but also could be due to differences in pulsation or other stall-specific factors that result in a change in milk yield. It is important to account for these other sources of milk weight variation that are unrelated to treatment. Modeling the effect of stall is a simple, convenient, and low-cost method to monitor and improve milk meter precision and functionality and can be used to reduce artificial variation and experimental error.

Effects of high-starch or high-fat diets formulated to be isoenergetic on energy and nitrogen partitioning and utilization in lactating Jersey cows.

The objective of this study was to determine the effects of high-starch or high-fat diets formulated to be isoenergetic on energy and N partitioning and utilization of energy. Twelve multiparous Jersey cows (mean ± standard deviation; 192 ± 11 d in milk; 467 ± 47 kg) in a crossover design with 28-d periods (24-d adaptation and 4-d collection) were used to compare 2 treatment diets. Treatments were high starch (HS; 30.8% starch, 31.8% neutral detergent fiber, and 1.9% fatty acids) or high fat (HF; 16.8% starch, 41.7% neutral detergent fiber, and 4.1% fatty acids). Diets were formulated to have net energy for lactation (NEL) content of 1.55 Mcal/kg of dry matter according to the National Research Council (2001) dairy model. Nutrient composition was varied primarily by replacing corn grain in HS with a rumen-inert fat source and cottonseed hulls in HF. Gross energy content was lower for HS (4.43 vs. 4.54 ± 0.01 Mcal/kg of dry matter), whereas digestible (2.93 vs. 2.74 ± 0.035 Mcal/kg of dry matter) and metabolizable energy (2.60 vs. 2.41 ± 0.030 Mcal/kg of dry matter), and NEL (1.83 vs. 1.67 ± 0.036 Mcal/kg of dry matter) content were all greater than for HF. Tissue energy deposited as body fat tended to be greater for HS (4.70 vs. 2.14 ± 1.01 Mcal/d). For N partitioning, HS increased milk N secretion (141 vs. 131 ± 10.5 g/d) and decreased urinary N excretion (123 vs. 150 ± 6.4 g/d). Compared with HF, HS increased apparent total-tract digestibility of dry matter (66.7 vs. 61.7 ± 1.06%), organic matter (68.5 vs. 63.2 ± 0.98%), energy (66.0 vs. 60.4 ± 0.92%), and 18-carbon fatty acids (67.9 vs. 61.2 ± 1.60%). However, apparent total-tract digestibility of starch decreased for HS from 97.0 to 94.5 ± 0.48%. Compared with HF, HS tended to increase milk yield (19.7 vs. 18.9 ± 1.38 kg/d), milk protein content (4.03 vs. 3.93 ± 0.10%), milk protein yield (0.791 vs. 0.740 ± 0.050 kg/d), and milk lactose yield (0.897 vs. 0.864 ± 0.067 kg/d). In addition, HS decreased milk fat content (5.93 vs. 6.37 ± 0.15%) but did not affect milk fat yield (average of 1.19 ± 0.09 kg/d) or energy-corrected milk yield (average of 27.2 ± 1.99 kg/d). Results of the current study suggest that the HS diet had a greater metabolizable energy and NEL content, increased partitioning of N toward milk secretion and away from urinary excretion, and may have increased partitioning of energy toward tissue energy deposited as fat.

Effect of 2-hydroxy-4-(methylthio) butanoate (HMTBa) supplementation on rumen bacterial populations in dairy cows when exposed to diets with risk for milk fat depression.

Diet-induced milk fat depression (MFD) is a condition marked by a reduction in milk fat yield experimentally achieved by increasing dietary unsaturated fatty acids and fermentable carbohydrates. 2-Hydroxy-4-(methylthio) butanoate (HMTBa) is a methionine analog observed to reduce diet-induced MFD in dairy cows. We hypothesize that the reduction in diet-induced MFD by HMTBa is due to changes in the rumen microbiota. To test this, 22 high-producing cannulated Holstein dairy cows were placed into 2 groups using a randomized block design and assigned to either control or HMTBa supplementation (0.1% of diet dry matter). All cows were then exposed to 3 different diets with a low risk (32% neutral detergent fiber, no added oil; fed d 1 to 7), a moderate risk (29% neutral detergent fiber and 0.75% soybean oil; fed d 8 to 24), or a high risk (29% neutral detergent fiber and 1.5% soybean oil; fed d 25 to 28) for diet-induced MFD. Rumen samples were collected on d 0, 14, 24, and 28, extracted for DNA, PCR-amplified for the V1-V2 region of the 16S rRNA gene, sequenced on an Illumina MiSeq (Illumina, San Diego, CA), and subjected to bacterial diversity analysis using the QIIME pipeline. The α diversity estimates (species richness and Shannon diversity) were decreased in the control group compared with the HMTBa group. Bacterial community composition also differed between control and HMTBa groups based on both weighted UniFrac (relative abundance of commonly detected bacteria) and unweighted UniFrac (presence/absence) distances. Within the HMTBa group, no differences were observed in bacterial community composition between d 0 and d 14, 24, and 28; however, in the control group, d 0 samples were different from d 14, 24, and 28. Certain bacterial genera including Dialister, Megasphaera, Lachnospira, and Sharpea were increased in the control group compared with the HMTBa group. Interestingly, these genera were positively correlated with milk fat trans-10,cis-12 conjugated linoleic acid and trans-10 C18:1, fatty acid isomers associated with biohydrogenation-induced MFD. It can be concluded that diet-induced MFD is accompanied by significant alterations in the rumen bacterial community and that HMTBa supplementation reduces these microbial perturbations.

Short communication: Relationships between physical form of oats in starter, rumen pH, and volatile fatty acids on hepatic expression of genes involved in metabolism and inflammation in dairy calves.

In early-weaning programs, dietary effects on calf rumen development have been studied extensively, but very little information is available about the effects of a solid diet on hepatic metabolism in preweaned dairy calves. The objective of this experiment was to determine the effect of physical form of oats in calf starter on the expression of key hepatic gluconeogenic, ß-oxidation, and acute phase protein genes in preweaned dairy calves. Samples were analyzed from 3 experiments that fed either ground or whole oats in calf starters. Briefly, 7 calves were slaughtered at 5 wk of age in experiment 1, 6 were slaughtered at 6 wk in experiment 2, and 7 were slaughtered at 7 wk in experiment 3, and liver tissue was collected for gene expression analysis. Calves from experiments 1 and 2 were cannulated, and their rumen pH and volatile fatty acids were measured during treatment periods. The mRNA expression of gluconeogenic enzymes pyruvate carboxylase (PC), cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PCK1 and PCK2), fatty acid oxidation enzyme carnitine palmitoyltransferase I (CPT1), and positive acute phase protein haptoglobin (HPT) was measured by real-time quantitative reverse-transcriptase PCR. Expression of HPT was greater in calves fed whole oats than in calves fed ground oats; however, PC, PCK1, PCK2, and CPT1 were not affected by the physical form of oats. All enzymes (PCK1, PCK2, HPT, and CPT1) except PC were affected by experiment; PCK1 and CPT1 had greater expression in experiment 2 than in experiments 1 and 3. Expression of PCK2 was similar in experiments 2 and 3 but greater than experiment 1. Expression of HPT was similar in experiments 1 and 2 but greater than experiment 3. The mRNA expression of enzymes PCK1, PCK2, and CPT1 differed between experiments 1 and 2 and was negatively correlated with rumen propionate and butyrate but had a positive relationship with rumen acetate. Similarly, rumen pH was different in experiments 1 and 2, averaging 5.69 in experiment 1 and 4.81 in experiment 2, and there was a negative correlation between mRNA expression of rate-limiting gluconeogenic PCK1, PCK2, and ß-oxidation CPT1 enzymes and rumen pH of calves in experiments 1 and 2. We concluded that the physical form of oats in calf starter did not affect gene expression of gluconeogenic and ß-oxidation enzymes in preweaned dairy calves. However, lower rumen pH may be related to the upregulation of these enzymes.

Milk fat response and milk fat and urine biomarkers of microbial nitrogen flow during supplementation with 2-hydroxy-4-(methylthio)butanoate.

2-Hydroxy-4-(methylthio)butanoate (HMTBa) is a methionine analog that has been observed to attenuate biohydrogenation (BH)-induced milk fat depression (MFD), possibly through reducing the shift to altered BH pathways. It has also been suggested that HMTBa increases microbial protein synthesis in the rumen. Our objectives were to stimulate BH-induced MFD and (1) verify HMTBa inhibition of BH-induced MFD and changes in milk fatty acids (FA) associated with altered rumen BH (i.e., trans-10 C18:1); and (2) determine the effect of HMTBa on milk fat (i.e., odd- and branched-chain FA) and urine biomarkers related to microbial N flow. Twenty-four multiparous cows (45.6 ± 8.5 kg of milk/d; mean ± standard deviation) and 12 primiparous cows (32.8 ± 3.1 kg of milk/d) were arranged in a crossover design. Treatments were unsupplemented control and HMTBa fed at 0.1% of diet dry matter intake. The experiment was 80 d and included a 10-d pretrial covariate period. Each experimental period included 2 phases that differed in risk for BH-induced MFD, including a 28-d low-risk phase (31.6% neutral detergent fiber, 21.8% starch, and no oil) and a 7-d moderate-risk phase (28.7% neutral detergent fiber, 28.1% starch, and 1.0% soybean oil). We found no interaction of treatment and parity. Milk fat yield (1.43 ± 0.51 kg/d) and milk fat trans-10 C18:1 (0.42 ± 0.08 g/100 g of FA) did not differ between treatments during the low-risk phase. However, during the moderate-risk phase, HMTBa maintained higher milk fat concentration (3.91 vs. 3.79%), tended to maintain higher milk fat yield (1.44 vs. 1.38 kg/d), and decreased milk fat trans-10 C18:1 (0.61 vs. 0.93% FA) compared with control. Additionally, HMTBa increased milk fat concentration and secretion of odd- and branched-chain FA by 5.3 and 10.2%, respectively, but urinary biomarkers of microbial N flow (i.e., purine derivatives) did not differ between treatments. However, rumen bacterial samples were not available to provide cow- or treatment-specific microbial protein-to-marker ratios, which is a critical source of variation. Additionally, transfer of odd- and branched-chain FA to milk is dependent on several factors that may affect interpretation of these biomarkers. In conclusion, HMTBa decreased absorption of alternate BH intermediates and maintained higher milk fat when feeding a diet with moderate-risk for MFD.

Diet starch concentration and starch fermentability affect energy intake and energy balance of cows in the early postpartum period.

Our objective was to evaluate the effects of diet starch concentration and fermentability on energy intake and energy balance during the early postpartum (PP) period. Fifty-two multiparous Holstein cows were used in a randomized block design experiment with a 2 × 2 factorial arrangement of treatments. Treatment rations were formulated to 22% or 28% starch concentration (LS and HS, respectively) with dry ground corn (DGC) or high moisture corn (HMC) as the primary starch source. Rations were formulated for 22% forage neutral detergent fiber (NDF) and 17% crude protein and fed from 1 to 23 d PP. Starch concentration was adjusted by altering concentrations of corn grain and soyhulls. Dry matter intake and milk yield were measured daily, and milk components, milk composition, body condition score (BCS), body weight (BW), and back fat thickness (BFT) were measured weekly. Feeds and refusals as well as fecal samples were collected, and digestibility was determined weekly. High moisture corn (HMC) decreased dry matter and net energy (NEL) intakes compared with DGC more when included in an HS diet (3.9 kg/d and 3.2 Mcal/d) than in an LS diet (0.9 kg/d and 0.6 Mcal/d). The HMC treatment decreased NDF digestibility 3.7 percentage units compared with DGC when included in the HS diet but had little effect when included in an LS diet. Compared with DGC, HMC increased weekly BW and BFT loss when included in an HS diet (-34.7 vs. -8.4 kg/wk and -0.12 vs. -0.10 cm/wk) and decreased weekly BW loss but increased weekly BFT loss when included in an LS diet (-18.9 vs. -21.4 kg/wk and -0.11 vs. -0.02 cm/wk). Weekly BCS loss increased for HMC compared with DGC (-0.33 vs. -0.23 unit/wk). High moisture corn also decreased milk NEL output compared with DGC (28.2 vs. 31 Mcal/d), but had little effect on energy balance, which was improved by HS compared with LS (-14.7 vs. -16.8 Mcal/d). Over time, concentrations of milk de novo fatty acids (<16 carbons) increased and concentration of milk preformed fatty acids (>16 carbons) decreased for all treatments, but yields of both sources as well as yield of mixed fatty acids (C16:0 plus C16:1 cis-9 and iso-C16:0) decreased over time with increased SF. Feeding HMC decreased energy intake and milk energy output, but it had little effect on energy balance during the early PP period.