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, β-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 β-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.

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, β-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 β-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 β-oxidation enzymes in preweaned dairy calves. However, lower rumen pH may be related to the upregulation of these enzymes.

Annual rhythms of milk and milk fat and protein production in dairy cattle in the United States

An annual pattern of milk composition has been well recognized in dairy cattle, with the highest milk fat and protein concentration observed during the winter and lowest occurring in the summer; however, rhythms of milk yield and composition have not been well quantified. Cosinor rhythmometry is commonly used to model repeating daily and annual rhythms and allows determination of the amplitude (peak to mean), acrophase (time at peak), and period (time between peaks) of the rhythm. The objective of this study was to use cosinor rhythmometry to characterize the annual rhythms of milk yield and milk fat and protein concentration and yield using both national milk market and cow-level data. First, 10 yr of monthly average milk butterfat and protein concentration for each Federal Milk Marketing Order were obtained from the US Department of Agriculture Agricultural Marketing Service database. Fat and protein concentration fit a cosine function with a 12-mo period in all milk markets. We noted an interaction between milk marketing order and milk fat and protein concentration. The acrophase (time at peak) of the fat concentration rhythm ranged from December 4 to January 19 in all regions, whereas the rhythm of protein concentration peaked between December 27 and January 6. The amplitude (peak to mean) of the annual rhythm ranged from 0.07 to 0.14 percentage points for milk fat and from 0.08 to 0.12 percentage points for milk protein. The amplitude of the milk fat rhythm generally was lower in southern markets and higher in northern markets. Second, the annual rhythm of milk yield and milk fat and protein yield and concentration were analyzed in monthly test day data from 1,684 cows from 11 tiestall herds in Pennsylvania. Fat and protein concentration fit an annual rhythm in all herds, whereas milk and milk fat and protein yield only fit rhythms in 8 of the 11 herds. On average, milk yield peaked in April, fat and protein yield peaked in February, fat concentration peaked in January, and protein concentration peaked in December. Amplitudes of milk, fat, and protein yield averaged 0.82 kg, 55.3 g, and 30.4 g, respectively. Milk fat and protein concentration had average amplitudes of 0.12 and 0.07, respectively, similar to the results of the milk market data. Generally, milk yield and milk components fit annual rhythm regardless of parity or diacylglycerol O-acyltransferase 1 (DGAT1) K232A polymorphism, with only cows of the low-frequency AA genotype (5.2% of total cows) failing to fit rhythm of milk yield. In conclusion, the yearly rhythms of milk yield and fat and protein concentration and yield consistently occur regardless of region, herd, parity, or DGAT1 genotype and supports generation by a conserved endogenous annual rhythm.

The effects of source and concentration of dietary fiber, starch, and fatty acids on the daily patterns of feed intake, rumination, and rumen pH in dairy cows

The daily patterns of feed intake and rumination influence rumen fermentation, rumen pH, and timing of absorbed nutrients in the dairy cow, but the effects of diet composition on these patterns are not well characterized. Data from 3 previously published experiments were examined to determine the influence of dietary starch, fiber, and fatty acids (FA) on daily patterns of intake, rumination, and rumen pH. Dietary neutral detergent fiber (NDF) and starch were investigated in 2 experiments, each with duplicated 4 × 4 Latin square designs with a 2 × 2 factorial arrangement of treatments in cows fed cows 1×/d at 1200 and 1400 h, respectively. To investigate fiber content and digestibility in the first experiment, brown midrib or isogenic conventional corn silage were fed in low- and high-NDF diets (29 and 38%, respectively). To investigate starch source and concentration in the second experiment, ground high-moisture corn or dry ground corn were fed in low- and high-starch diets (21 and 32%, respectively). Effect of fat concentration and saturation was investigated in the third experiment using a replicated 4 × 4 Latin square design that fed cows 1×/d at 0900 h; treatments included a control diet with no added fat and 2.5% added saturated FA, unsaturated FA, or a mixture of the saturated and unsaturated FA. In the first 2 experiments, intake followed a similar daily pattern regardless of starch and NDF concentration or digestibility. Rumination displayed a treatment by time interaction for both NDF and starch concentration, with high-fiber, low-starch diets causing greater rumination overnight but not midday. High-starch diets decreased total daily rumen pH equally across the day, but did not change the daily pattern. Type of corn silage did not affect the daily patterns of rumination or rumen pH, but pH was reduced throughout the day in brown midrib diets. In the third experiment, no interactions between fatty acid supplement and time of day were observed for intake, rumination, or rumen pH. Within all experiments, rumination fit or tended to fit a 24-h rhythm regardless of diet, with the amplitude of the rumination being reduced in low-starch diets and diets containing saturated FA or a mixture of saturated and unsaturated FA. Overall, intake, rumination, and rumen pH follow a daily pattern that was minimally modified by dietary fiber and starch type and level or fat level and fatty acid profile.

Comparisons of bacterial and archaeal communities in the rumen and a dual-flow continuous culture fermentation system using amplicon sequencing

Dual-flow continuous culture (CC) fermenters are commonly used to study rumen fermentation in vitro. Research using culture-based and oligonucleotide techniques has shown that certain microbial populations within fermenters may be maintained at abundances similar to those observed in vivo. In this study, bacterial and archaeal communities in the rumen of dairy cattle and in a dual-flow CC fermentation system were compared using high-throughput amplicon sequencing targeting the V4 hypervariable region of 16S rRNA. We hypothesized that the in vitro system harbored a comparable bacterial and archaeal community to that observed in the rumen. Members of the Bacteroidetes and Firmicutes made up the 2 most abundant phyla in the rumen, inoculum, and fermenters and did not differ among sample types (P > 0.10). Similarly, Prevotellaceae, the most abundant family in all 3 sample types, did not differ based on source (P = 0.80). However, beta diversity analyses revealed that bacterial and archaeal communities differed between fermenters and rumen samples (P ≤ 0.001), but fermenter bacterial and archaeal communities stabilized by day 4 of each period. While the overall bacterial and archaeal community differs between natural rumens and those detected in in vitro fermenter systems, several prominent taxa were maintained at similar relative abundances suggesting that fermenters may provide a suitable environment in which to study shifts among the predominant members of the microbial community.

Differences in in vitro hydrolysis and fermentation among and within high-fiber ingredients using a modified three-step procedure in growing pigs

In vitro DM disappearance (IVDMD) and gas production can be used to rapidly estimate apparent total tract digestibility of DM and GE in feed ingredients used in swine diets. However, the accuracy of the system in estimating ME among sources feed ingredients with high content of dietary fiber is not clear. Objectives of this study were 1) to measure IVDMD of feed ingredients with high insoluble fiber content and determine and compare in vitro gas production kinetics from fiber fermentation among wheat straw (WS; 16 sources; 69.0-83.4% NDF), soybean hulls (SBH; 16 sources; 60.9-67.7% NDF), and corn distiller's dried grains with solubles (DDGS; 16 sources; 28.8-44.0% NDF); and 2) to estimate ME contributions resulting from gas production of DDGS. Each 2-g sample was hydrolyzed for 2 h with pepsin and for a subsequent 4 h with pancreatin. Hydrolyzed residues were filtered, washed, dried, weighed, pooled within the same sample, and used for subsequent fermentation using swine fecal inocula. Volume of gas produced was recorded at 11 time points during 72 h of incubation. Parameters of gas production kinetics were calculated using a nonlinear monophasic model, and differences among ingredients were compared using a mixed model. The IVDMD from simulated gastric and small intestinal hydrolysis (IVDMDh) in DDGS (55.7%) was greater (P < 0.05) than that in SBH (19.7%), which was greater (P < 0.05) than that in WS (14.5%). In vitro DM digestibility from simulated large intestine fermentation (IVDMDf) of SBH (68.5%) was greater (P < 0.05) than that of DDGS (52.7%), which was greater than that of WS (41.8%). In vitro DM digestibility from simulated total tract digestion (IVDMDt) was greatest (P < 0.01) in DDGS (79.2%) followed by SBH (74.8%), and both were greater than that in WS (50.2%). The asymptotic gas production (mL/g substrate) was greater (P < 0.05) for SBH (293) than for DDGS (208) and WS (53). There were differences (P < 0.01) in IVDMDh among sources of WS, SBH, and DDGS, whereas IVDMDf and IVDMDt were different (P < 0.01) among sources of SBH but not among sources of DDGS or WS. There were no differences in asymptotic gas production among sources of WS, SBH, or DDGS. In conclusion, the modified 3-step procedure allowed for characterizing the variability of DM digestibility and asymptotic gas production resulting from residue fermentation among WS, SBH, and DDGS and among sources of each ingredient.