Mitochondria are central to metabolism and are the primary energy producers for all biosynthesis. The objective of this study was to determine if the mitochondrial enzyme activity of peripheral blood mononuclear cells in heifers were associated with ADG, reproductive outcomes, first lactation milk production and survival. Twenty-three Holstein and 23 Jersey heifer calves were enrolled, and blood and body weight data were collected at 1, 2, 8, 36, 52 and 110 wk of age. Respiratory and fecal scores were recorded daily for the first 30 d of life. Milk production data were collected from herd management software through first lactation and health events were tracked to the fourth lactation on surviving animals. Mitochondrial isolation and enzyme activities for citrate synthase, complex I, complex IV, and complex V were determined using kits from Abcam. Data were analyzed using GLM and the Logistic procedure of SAS (Version 9.4). Multivariate regression analyses were conducted to determine if calf mitochondrial enzymatic activity and covariate health indices (fecal and respiratory scores, number of treatments, hematology) were associated with ADG (8, 36, 52 and 110 wk), lactation performance (milk yield, fat yield, solids yield, ECM, 305ME and relative value) and reproduction (age at first service, age at first conception, age at first calving and number of services). For Holsteins and Jerseys, mitochondrial enzyme activities and health indices were correlated to all ADG and milk production outcomes (R² ≥ 0.63, and R² ≥ 0.45, respectively). Reproduction outcomes were correlated with bodyweight gain, mitochondrial function and red blood cell traits for Holsteins and Jerseys (R² ≥ 0.47, and R² ≥ 0.55, respectively). Logistic regression analyses were performed to determine if early life enzymatic activity impacted survival outcomes in the herd. Calves below the median for complex V enzyme activity at 1 wk were more likely to be removed from the herd compared with calves above the median by lactation 1, 2, 3 and 4 (odds ratio = 4.7, 7.7, 7.0 and 6.9, respectively). Calves below the median for the difference in hematocrit from 2 to 1 wk were more likely to be removed from the herd compared with calves above the median by lactation 1, 2, 3 and 4 (odds ratio = 13, 10, 5.2 and 4.7, respectively). These findings suggest that predictions of cow performance could be improved by considering the impact of early life mitochondrial enzymatic activity and health indices.

In practice, cows are fed by pen, but a diet is formulated to the nutrient requirements of a single cow. If the DM intake (DMI) of a pen were equal for all cows, this approach would have no error, but cows are grouped into pens on pregnancy and other management factors creating a distribution of DMI. The goal of precision feeding is to meet the requirements of individual animals to increase efficiency and reduce environmental impact but is not achieved when a group is fed as if the individuals have uniform requirements and the DMI distribution is not normal. The hypothesis of this work is that the DMI of cow pens are not normally distributed and the total DMI from the best-fit distribution shape for a cow pen will have lower percentage error to the observed DMI than a prediction of a single DMI that is fed at a uniform level and assumes a normal distribution. Our objective was to describe the distribution shape of DMI by week of lactation, and for different pen types. Pens were generated by randomly assorting cows by the week of lactation from a database into different categories of pen for size and lactation period. These pens were fitted to the best distribution type, and its parameters were used to randomly generate distribution plots that predict the total DMI for each pen. A second predictive model estimated the DMI of each pen using an empirical equation of DMI that was multiplied by the number of cows in the pen to represent feeding of a uniform DMI quantity. The percentage error for the distribution shape model was significantly lower than the empirical model with pen errors being less than 1%. The beta distribution type was the most common distribution to best represent the data of pen DMI. Describing the distribution and using it to predict a total pen DMI provides accurate estimates of feed quantity for a group. Reducing error by using the distribution of DMI for feed formulation, instead of the nutrient requirements of an individual animal can provide a precision nutrition approach to group feeding.

Computer models used in ration formulation assume that nutrients supplied by a ration formulation are the same as the nutrients presented in front of the cow in the final ration. Deviations in nutrients due to feed management effects such as dry matter changes (i.e., rain), loading, mixing, and delivery errors are assumed to not affect delivery of nutrients to the cow and her resulting milk production. To estimate how feed management affects nutrients supplied to the cow and milk production, and determine if nutrients can serve as indexes of feed management practices, weekly total mixed ration samples were collected and analyzed for 4 pens (close-up cows, fresh cows, high-milk-producing, and low-milk-producing cows, if available) for 7 to 12 wk on 5 commercial California dairies. Differences among nutrient analyses from these samples and nutrients from the formulated rations were analyzed by PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Milk fat and milk protein percentages did not vary as much [coefficient of variation (CV) = 18 to 33%] as milk yield (kg; CV = 16 to 47 %) across all dairies and pens. Variability in nutrients delivered were highest for macronutrient fat (CV = 22%), lignin (CV = 15%), and ash (CV = 11%) percentages and micronutrients Fe (mg/kg; CV = 48%), Na (%; CV = 42%), and Zn (mg/kg; CV = 38%) for the milking pens across all dairies. Partitioning of the variability in random effects of nutrients delivered and intraclass correlation coefficients showed that variability in lignin percentage of TMR had the highest correlation with variability in milk yield and milk fat percentage, followed by fat and crude protein percentages. But, variability in ash, fat, and lignin percentages of total mixed ration had the highest correlation with variability in milk protein percentage. Therefore, lignin, fat, and ash may be the best indices of feed management to include effects of variability in nutrients on variability in milk yield, milk fat, and milk protein percentages in ration formulation models.

Mitochondria are central to metabolism, nutrition, and health, but many factors can influence their efficiency. The objectives of this study were to determine if the mitochondrial enzyme activities of citrate synthase, complex I, complex IV, and complex V from peripheral blood mononuclear cells in Holstein and Jersey dairy calves were affected by age or relative gain as a percent of initial weight. Twenty-three Holstein and 23 Jersey heifer calves were enrolled between 3 and 6 d of age and whole blood samples were collected via jugular venipuncture at 1, 2, and 8 wk of age. Crude mitochondrial extracts were obtained from the peripheral blood mononuclear cell fraction at each time point and subsequently assayed for enzymatic activity. Age-dependent changes in activity were observed in complex V for both breeds. In Jersey calves complex IV and citrate synthase activity differed with age. Complex I activity was greater for high relative gain Jerseys and tended to be greater for high relative gain Holstein calves. Holstein calves had greater incidence of scours compared with Jersey calves, and in both breeds scouring calves exhibited greater complex V activity compared with those without scours. These data suggest that age and immune challenge in the form of scours affect mitochondrial complex V activity. Additionally, complex I activity may serve as a marker for calf growth potential because it was influenced by relative gain and not age.

Live yeast products (LYPs) increase nutrient utilization and milk yield. The purpose of this trial was to determine if a LYP administered at 3 g/cow/d at a commercial dairy increased milk production. Cows were milked twice daily and given LYP in the total mixed ration in an OFF, ON, OFF, ON, OFF design where each ON or OFF period lasted 45 days and LYP was added during ON periods. Only data from cows with at least one Dairy Herd Improvement Association milk test each period were used in the data analyses (n = 1903). Statistics were performed using the Mixed procedure of SAS (SAS. 2015. SAS/ STAT User’s Guide: Version 9.4. Cary, NC: SAS Institute Inc.) with treatment nested within period and covariates: parity, days in milk, pen and corresponding production value in the previous control period. Overall, daily milk yield (32.3 and 33.0 kg, P =.0014) and milk protein (1.04 and 1.08 kg, P =.0006; 3.25% and 3.31%, P =.0021) for control and LYP, respectively, were greater for cows fed LYP. Therefore milk yield and milk protein yield and percentage increased with supplementation of LYP.

The purpose of this trial was to determine if a yeast product (YP; ProDairy, Donaghys, Christchurch, New Zealand) given in water troughs increased milk production or altered rumen pH and blood parameters. Multiparous cows (930) in a commercial herd were randomly assigned to 1 of 4 pens as they reached 30 DIM. Milk yield, fat, and protein were measured every other week for 11 wk. Two of the 4 pens received YP at the rate of 9 mL/cow per day. All 4 pens were fed the same diet (525 g/kg of DM, 186 g/kg of CP, 220 g/kg of ADF, 329 g/kg of NDF, 43.8 g/kg of fat, 188 g/kg of starch, 41.3 g/kg of lignin, and 81.9 g/kg of ash). Statistics were performed using PROC MIXED with random effects pens nested within treatment and the fixed effects of DIM, week, and parity. Average daily milk yield (43.1 and 44.8 kg, P = 0.042) for control and supplemented pens, respectively, were greater in YP pens. But milk fat (1.47 and 1.45 kg, P = 0.13) and milk protein (1.24 and 1.23 kg, P = 0.045) for control and supplemented pens, respectively, were lower in YP pens. Overall rumen pH (7.7 and 7.4, P = 0.044) and blood ketone bodies (0.73 and 0.64 mEq/L, P = 0.011) were also reduced in supplemented pens. Therefore, YP did increase milk yield and affect rumen pH and blood ketone bodies, but other conditions on the commercial dairy may have influenced the milk response to YP. Depending upon the ability of the dairy to manage a consistent water supply, the delivery of YP via water should be considered by nutritionists and managers. More research is needed to determine the influence of other factors on milk response to YP supplemented in the water supply.

Our objectives were to characterize responses in the field to a mix of fibrolytic enzymes using large commercial dairy herds and sufficient study power to evaluate milk production and reproductive responses to an enzyme treatment started during the precalving period. We hypothesized that the use of the enzyme treatment would increase milk production when provided to dairy cows precalving and for approximately 200 d of lactation. The study was conducted on 7,507 cows, in 8 replicates and 16 pens, at 3 dairies in the United States. Eight pens were randomly allocated as control pens and received no enzyme, and another 8 pens received enzyme treatment at a dose of 750 mL/t of dry matter feed. Milk production and energy-corrected milk yield were increased with the enzyme treatment by 0.70 and 0.80 kg/d, respectively, across a 5-month period. Milk fat percentage was not significantly increased by enzyme treatment, but milk fat yield was significantly increased by 0.040 kg/d, compared with controls. Milk protein yield increased 0.010 kg/d with enzyme treatment despite a small reduction of 0.020 percentage units in milk protein percentage. We found no evidence of an increase in the ln somatic cell count for the enzyme-treated cows. Body weight overall was not increased for enzyme-treated cows, but we did observe a numerical increase in dry matter intake (0.20 kg/head per day) for enzyme-treated cows. Most production responses to the enzyme treatment were influenced by dairy. Compared with controls, milk yield in enzyme-treated cows was significantly higher by 3.6 kg/d in dairy 2 and numerically higher by 0.60 and 0.20 kg/d in dairies 1 and 3, respectively. Reproduction, health, and risk of removal or death were not significantly influenced by treatment, apart from a reduced time to first breeding. Production responses to the enzyme treatment varied by dairy from substantial to minor increases, but variation among dairies was not evident in differences in dry matter intake or in partitioning of body weight among enzyme-treated and control pens and cows. It appears likely that the increase in production reflected increased digestibility of feed; however, further work is needed to identify factors influencing the variation in production responses to enzymes.

Objective: Our objective was to determine whether preweaned steer and heifer calves given a phytogenic starter supplement (either one containing caraway, licorice, oak bark, and vanilla that was soluble in milk, PM, or one containing caraway, licorice, oak bark, and vanilla, PC) or no phytogenic supplement, control (CTR), at a commercial calf ranch would have increased starter intake, weight gain, or rumen development. Materials and Methods: Holstein calves (124) were randomly assigned to 1 of 3 treatments, CTR, PM, or PC, at 2 d of age. Supplements PM or PC were added to individual feed buckets at each feeding at the rate of 0.25 g/kg of starter at a.m. and p.m. feedings. Calves were weighed at enrollment and at weaning, and blood samples were collected from a subset of 13 calves per treatment to assess rumen development. Weekly average DMI, milk intake, Glu, and BHB were analyzed using the Mixed procedure of SAS (v. 9.4; SAS Institute Inc., Cary, NC) Results and Discussion: Weekly average DMI (P < 0.01), BHB (P < 0.01), and Glu (P < 0.01) were different by week but not by treatment. Product PC group was numerically greater in total DMI, gain, and ADG and had faster rumen development indicated by overall greater BHB values but were not different among treatments. Implications and Applications: Addition of PM or PC to starter feed did not increase DMI, rumen development, or BW gain. But, the dose may have been too small or not fed long enough to elicit a response during the preweaning period.

The robustness of efficiency estimates depends on theoretical consistency of models from which those estimates are developed; functional forms of the variables must be globally consistent with theoretical properties regarding feed utilization for maintenance and gain in growing and finishing cattle. Model parameter estimates and their dimensions must be unique or estimates of feed utilization and gain will not reflect reality. A linear equation commonly used to estimate daily DMI by the ith individual animal (ADFIi), based on mean weight and gain during a feeding period, was evaluated to determine if that model was correctly specified and if the vector predicted ADFI differed from the vector observed ADFI. Three independently gathered data sets were evaluated using a multiple linear regression model; variability described by that model failed to capture observed variability in the data (lack of fit, P < 0.10), and predicted ADFI differed from observed (P < 0.05); for 1 of the 3 data sets, residuals were not normally distributed (P < 0.001). Functional forms of the variables in the first model evaluated, characterizing ADFI required for maintenance (b1 × BW0.75) and gain (b2 × ADG), were consistent with neither published empirical nor theoretical relationships among ADFI, BW, and ADG. Parameter estimates determined for that linear model were not BLUE. Better fits among final BW, initial BW, and ADFI were found for a first-order relationship, in which final BW was a function of initial BW and ADFI, as indicated by R2 > 0.90. The linear model and, to a lesser degree, the first nonlinear model lacked theoretical and global consistency. A second nonlinear model, which described retained energy as a function of ME intake, best fit the data, and functional forms of variables describing ME intake at maintenance and the efficiency of ME utilization for gain were consistent with theoretical estimates found in the literature. Changes in feed intake and live BW in linear and nonlinear models failed to adequately describe efficiencies of metabolic processes, which are better characterized by changes in retained energy as a function of ME intake in nonlinear models.

Objective: Our objectives were to evaluate milk production and constituent responses to changes in the diet for pens of cows over time and whether differences in response were attributable to fibrolytic enzymes and dairy. Materials and Methods: A multiherd trial used 7,507 cows in 8 control and enzyme-treated (750 mL/t of DM feed) replicates (16 pens) on 3 dairies. Feed composition and milk production and constituents by pen (n = 12) were analyzed weekly. Time-series cross-correlation estimates by pen of feed component intakes (kg/d) and milk responses were pooled to produce effect size (ES) estimates. Results and Discussion: We observed differences between treatment and control pens for soluble protein (ES = 0.249) in the same week, acid detergent–insoluble CP (ES = 0.293) and lignin (ES = 0.237) 1 wk before with milk protein percentage, and acid detergent–insoluble CP (ES = 0.276) and lignin (ES = 0.246) 1 wk before with milk protein yield. These differences are consistent with enzymes improving feed digestibility, particularly for protein and fiber fractions. Differences in production responses to intake of feed components among dairies were observed. More significant and larger differences occurred among dairies than for treatments. The dairy that increased milk production most with treatment had an estimated MP excess from the diet, whereas the least responsive had an estimated MP-deficit diet and was the highest producing. Implications and Applications: We provide evidence for variability in enzyme response and that changes in dietary feed components influence production outcomes immediately and up to 3-wk later.