Peripheral blood mononuclear cell mitochondrial enzyme activity in calves is associated with average daily gain, reproductive outcomes, lactation performance, and survival.

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 was associated with average daily gain, 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, SAS Institute Inc.). 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 average daily gain (8, 36, 52, and 110 wk), lactation performance (milk yield, fat yield, solids yield, energy-corrected milk, 305-d mature equivalent, 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 with all average daily gain and milk production outcomes (R2 ≥ 0.63 and R2 ≥ 0.45, respectively). Reproduction outcomes were correlated with body weight 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 affected 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 effect of early-life mitochondrial enzymatic activity and health indices.

Describing the distribution type of DM intake for dairy cow pens based on pen characteristics.

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.

Characterizing ruminal acidosis risk: A multiherd, multicountry study.

A multicenter observational study was conducted on early lactation Holstein cows (n = 261) from 32 herds from 3 regions (Australia, AU; California, CA; and Canada, CAN) to characterize their risk of acidosis into 3 groups (high, medium, or low) using a discriminant analysis model previously developed. Diets ranged from pasture supplemented with concentrates to total mixed ration (nonfiber carbohydrates = 17 to 47 and neutral detergent fiber = 27 to 58% of dry matter). Rumen fluid samples were collected <3 h after feeding and analyzed for pH, and ammonia, d- and l-lactate, and volatile fatty acid (VFA) concentrations. Eigenvectors were produced using cluster and discriminant analysis from a combination of rumen pH, and ammonia, d-lactate, and individual VFA concentrations and were used to calculate the probability of the risk of ruminal acidosis based on proximity to the centroid of 3 clusters. Bacterial 16S ribosomal DNA sequence data were analyzed to characterize bacteria. Individual cow milk volume, fat, protein, and somatic cell count values were obtained from the closest herd test to the rumen sampling date (median = 1 d before rumen sampling). Mixed model analyses were performed on the markers of rumen fermentation, production characteristics, and the probability of acidosis. A total of 26.1% of the cows were classified as high risk for acidosis, 26.8% as medium risk, and 47.1% as low risk. Acidosis risk differed among regions with AU (37.2%) and CA (39.2%) having similar prevalence of high-risk cows and CAN only 5.2%. The high-risk group had rumen phyla, fermentation, and production characteristics consistent with a model of acidosis that reflected a rapid rate of carbohydrate fermentation. Namely, acetate to propionate ratio (1.98 ± 0.11), concentrations of valerate (2.93 ± 0.14 mM), milk fat to protein ratio (1.11 ± 0.047), and a positive association with abundance of phylum Firmicutes. The medium-risk group contains cows that may be inappetant or that had not eaten recently or were in recovery from acidosis. The low-risk group may represent cattle that are well fed with a stable rumen and a slower rumen fermentation of carbohydrates. The high risk for acidosis group had lower diversity of bacteria than the other groups, whereas CAN had a greater diversity than AU and CA. Rumen fermentation profile, abundance of ruminal bacterial phyla, and production characteristics of early lactation dairy cattle from 3 regions were successfully categorized in 3 different acidosis risk states, with characteristics differing between acidosis risk groups. The prevalence of acidosis risk also differed between regions.

Peripheral blood mononuclear cell mitochondrial enzyme activity is associated with parity and lactation performance in early lactation Holstein dairy cows.

Mitochondria are central to metabolism and are the primary energy producers for all biosynthesis, including lactation. The objectives of this study were to determine if high- and low-producing dairy cows exhibit differences in peripheral blood mononuclear cell mitochondrial enzyme activities of citrate synthase, complex I, complex IV, and complex V during early lactation and, thus, to determine whether those differences were related to differences in lactation performance in the dairy cow. Fifty-six Holstein cows were assigned to 1 of 4 groups: (1) primiparous high, (2) primiparous low, (3) multiparous high, or (4) multiparous low. Primiparous and multiparous cows were analyzed separately. Then, cows were divided into high or low production groups for each production parameter [peak milk, average milk, energy-corrected milk (ECM), fat-corrected milk (FCM), milk lactose, milk fat, milk protein, total solids (TS), solids-not-fat, feed efficiency, and somatic cell count (SCC)]. For all data analysis, production parameters are expressed as yields (kg/d) and SCC (103 cells/mL). High and low production groups were defined by their respective mean production parameters for the 56 cows, with below average cows defined as low and above average cows defined as high. Whole blood samples were collected at one time point, approximately 70 d in milk at 0800 h, and processed for crude mitochondrial extracts from peripheral blood mononuclear cells to determine the activity rates of mitochondrial enzymes. Milk samples were collected 9 times (3 d, 3 times per d) during the week of blood collection and analyzed for major components (fat, protein, lactose, TS, and SCC). Multiparous cows had lower citrate synthase activity than primiparous cows across all production parameters. High-producing cows had greater complex I activity for peak milk, milk yield, ECM, FCM, milk fat, TS, and feed efficiency, and greater complex V activity for ECM, FCM, milk lactose, milk fat, and TS across parities. These findings imply that the most influential respiratory chain enzymes on the level of milk production are those responsible for electron transport chain initialization and ATP production.

Effects of mannan-oligosaccharide and Bacillus subtilis supplementation to preweaning Holstein dairy heifers on body weight gain, diarrhea, and shedding of fecal pathogens.

The objective of this clinical trial was to evaluate the effectiveness of probiotic, prebiotic, and synbiotic supplementation on average daily weight gain (ADG), duration of diarrhea, age at incidence of diarrhea, fecal shedding of Cryptosporidium oocysts, enteric pathogens, and the odds of pneumonia in preweaning dairy heifer calves on a commercial dairy. Feeding prebiotics and probiotics may improve health and production of calves. Hence, healthy Holstein heifer calves (n = 1,801) from a large California dairy were enrolled at 4 to 12 h of age and remained in this study until weaning at 60 d of age. Calves were block randomized to 1 of 4 treatments: (1) control, (2) yeast culture enriched with mannan-oligosaccharide (prebiotic), (3) Bacillus subtilis (probiotic), and (4) combination of both products (synbiotic), which were fed in milk twice daily from enrollment until weaning. Serum total protein at enrollment and body weight at 7, 42, and 56 d of age were measured. Fecal consistency was assessed daily for the entire preweaning period. A subgroup of 200 calves had fecal samples collected at 7, 14, 21, and 42 d for microbial culture and enumeration of Cryptosporidium oocysts by direct fluorescent antibody staining. Synbiotic-treated calves had 19 g increased ADG compared with control calves for overall ADG, from 7 to 56 d. From 42 to 56 d, prebiotic-treated calves had 85 g greater ADG and synbiotic-treated calves had 78 g greater ADG than control calves. There was no difference in duration of the first diarrhea episode, hazard of diarrhea, or odds of pneumonia per calf with treatment. Probiotic-treated calves had 100 times lower fecal shedding of Cryptosporidium oocysts at 14 d and prebiotic-treated calves had fewer Escherichia coli and pathogenic E. coli at 42 d compared with control calves. Although there were no effects on duration of diarrhea or pneumonia incidence, greater ADG in the late preweaning period may reflect treatment effects on enteric pathogens during the rearing process. The decreased shedding of Cryptosporidium should reduce infectious pressure, environmental contamination, and public health risks from Cryptosporidium. Our findings suggest ADG and potential health benefits for calves fed prebiotics, probiotics, and synbiotics and can help the dairy industry make informed decisions on the use of these products in dairy production.

Effects of in-feed enzymes on milk production and components, reproduction, and health in dairy cows.

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.

The effects of relative gain and age on peripheral blood mononuclear cell mitochondrial enzyme activity in preweaned Holstein and Jersey calves.

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.

Liver mitochondrial oxygen consumption and efficiency of milk production in lactating Holstein cows supplemented with copper, manganese and zinc.

The objective of this study was to examine the relationship between mitochondrial proton leak and feed efficiency with supplementation of different levels of Cu, Mn and Zn (Bioplex, Alltech) at levels above Nutrient Requirements of Dairy Cattle (NRC, 2001). Milk yield and composition, mineral excretion in milk and faeces, feed efficiency and liver mitochondrial proton leak were measured in 60 Holstein dairy cows at approximately 70 days in milk on a commercial dairy. Treatments reflect total Cu, Mn and Zn intake/day and are as follows: (i) High: 444 mg/day Cu, 3492 mg/day Mn, 2234 mg/day Zn; (ii) Med: 436 mg/day Cu, 3002 mg/day Mn, 2047 mg/day Zn; (iii) Low: 420 mg/day Cu, 2764 mg/day Mn, 2186 mg/day Zn; (iv) LowMn: 391 mg/day Cu, 2617 mg/day Mn, 1849 mg/day Zn; and (v) Control: 264 mg/day Cu, 2850 mg/day Mn, 1593 mg/day Zn. Proton leak-dependent respiration was lowest in Control (p < .10). However, measures of efficiency were greatest in Med and least in High (p < .10). Therefore, measures of efficiency did not reflect efficiency due to low proton leak and there appears to be an upper limit to beneficial supplementation of Cu, Mn and Zn.

Liver mitochondrial oxygen consumption and proton leak kinetics in broilers supplemented with dietary copper or zinc following coccidiosis challenge.

Mitochondrial respiration was assessed in sixteen 7-day-old broilers as a subset of a larger study assessing the effects of Cu and Zn supplementation above requirements with a coccidiosis challenge on gain/feed ratio. The birds were selected from four treatments (four birds/treatment): a control diet (Cu 15 mg/kg and Zn 60 mg/kg) + coccidiosis challenge (CC), a Cu diet with 245 mg/kg Cu from tribasic copper chloride (TBCC) + CC, a negative control diet (Cu 15 mg/kg and Zn 60 mg/kg) - CC and a Zn diet with 2000 mg/kg Zn from ZnO. The diets were composed of 49% corn, 40% soybean meal, 6.2% vegetable oil (diet dry matter = 90.62%, crude protein = 21.37%, fat = 7.7%, metabolizable energy = 12.1 MJ/day) and were fed for 14 days. Birds were dissected, and approximately one gram of liver tissue was used for mitochondrial oxygen consumption and proton leak kinetics assays. Respiratory control ratio and mitochondrial proton leak assessed by calculating rates of oxygen consumption at 175mV membrane potential were greater for the negative control group, but there were no differences in average gain/feed among treatments. In summary, broilers that did not undergo coccidiosis challenge had lower proton leak and higher respiratory control ratio. However, the impact of supplementation of Cu and Zn above requirements did not appear to prevent changes in respiratory control ratio and proton leak kinetics with coccidiosis challenge.

Partitioning of feed intake into maintenance and gain in growing beef cattle: Evaluation of conventional and Bayesian analyses.

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 th individual animal (ADFI), 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, < 0.10), and predicted ADFI differed from observed ( < 0.05); for 1 of the 3 data sets, residuals were not normally distributed ( < 0.001). Functional forms of the variables in the first model evaluated, characterizing ADFI required for maintenance ( × BW) and gain ( × 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 > 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.

Relationship between Liver Mitochondrial Respiration and Proton Leak in Low and High RFI Steers from Two Lineages of RFI Angus Bulls.

The objective of this research is to evaluate liver mitochondrial oxygen consumption and proton leak kinetics in progeny from two lineages of Angus bulls with high and low residual feed intake (RFI). Two Angus bulls were selected based on results from a genetic test for RFI and were used as sires. Eight offspring at 10-11 months of age from each sire were housed in individual pens for 70-105 days following a diet adaptation period of 14 days. Progeny of the low RFI sire had 0.57 kg/d (P = 0.05) lower average RFI than progeny of the high RFI sire. There was no difference in dry matter intake between low and high RFI steers, but low RFI steers gained more body weight (P = 0.02) and tended to have higher average daily gains (P = 0.07). State 3 and State 4 respiration, RCR, and proton leak did not differ between high and low RFI steers (P = 0.96, P = 0.81, P = 0.93, and P = 0.88, resp.). Therefore, the increase in bodyweight gain which distinguished the low RFI steers from the high RFI steers may be associated with other metabolic mechanisms that are not associated with liver mitochondrial respiration and proton leak kinetics.

Blood calcium dynamics after prophylactic treatment of subclinical hypocalcemia with oral or intravenous calcium.

Total serum Ca dynamics and urine pH levels were evaluated after prophylactic treatment of subclinical hypocalcemia after parturition in 33 multiparous Jersey × Holstein crossbreed cows. Cows were blocked according to their calcemic status at the time of treatment [normocalcemic (8.0-9.9 mg/dL; n = 15) or hypocalcemic (5.0-7.9 mg/dL; n = 18)] and randomly assigned to 1 of 3 treatments: control [no Ca supplementation (n = 11)]; intravenous Ca [Ca-IV (n = 11), 500 mL of 23% calcium gluconate (10.7 g of Ca and 17.5 g of boric acid as a solubilizing agent; Durvet, Blue Springs, MO)]; or oral Ca [Ca-Oral (n = 11), 1 oral bolus (Bovikalc bolus, Boehringer Ingelheim, St. Joseph, MO) containing CaCl2 and CaSO4 (43 g of Ca) 2 times 12h apart]. Total serum Ca levels were evaluated at 0, 1, 2, 4, 8, 12, 16, 20, 24, 36, and 48 h, and urine pH was evaluated at 0, 1, 12, 24, 36, and 4 8h after treatment initiation. Total serum Ca levels were higher for Ca-IV than for control and Ca-Oral cows at 1, 2, and 4h after treatment initiation, but lower than Ca-Oral cows at 20, 24, and 36 h and lower than control cows at 36 and 48 h. At 1h after treatment initiation, when serum Ca levels for Ca-IV cows peaked (11.4 mg/dL), a greater proportion of Ca-IV (n = 8) cows had total serum Ca levels >10mg/dL than control (n = 0) and Ca-Oral (n = 1) cows. At 24h after treatment initiation, when Ca-IV cows reached the total serum Ca nadir (6.4 mg/dL), a greater proportion of Ca-IV (n = 10) cows had serum Ca levels <8 mg/dL than control (n = 5) and Ca-Oral (n = 2) cows. Treatment, time, and treatment × time interaction were significant for urine pH. Mean urine pH was lower for Ca-Oral cows (6.69) than for control (7.52) and Ca-IV (7.19) cows. Urine pH levels at 1h after treatment were lower for Ca-IV cows compared with both control and Ca-Oral cows, a finding likely associated with the iatrogenic administration of boric acid added as a solubilizing agent of the intravenous Ca solution used. At 12, 24, and 36 h, urine pH levels were lower for Ca-Oral cows compared with both control and Ca-IV cows. This was expected because the oral Ca supplementation used (Bovikalc) is designed as an acidifying agent. Wide fluctuations in blood Ca were observed after prophylactic intravenous Ca supplementation. The implications for milk production and animal health, if any, of these transient changes in total serum Ca have yet to be evaluated.

Survey of beef quality assurance on California dairies.

In October 2011, a mail and online survey of California dairy personnel was conducted to assess producer familiarity with and support of the Dairy Animal Care and Quality Assurance (DACQA) program. The DACQA program addresses cattle of all ages (birth to culling) and standard practices that affect the use of dairy cattle for beef. The survey was mailed to a random sample of 1,071 California dairies (65%) stratified by county, proportional to the number of dairies in each respective county. Data from the 158 responses received (15%) showed that 90% of culled cows on California dairies were sold for beef. However, personnel on more than one-half of California dairies (56%) had no knowledge of how their herd cull cows ranked in terms of beef quality measures (body condition score, US Department of Agriculture carcass grade, and hot carcass weight). Survey results showed that a considerable proportion of California dairy personnel were aware of recommended injection practices including a preference for subcutaneous injections (45%). A drug inventory was maintained on approximately 50% of the state's dairies. Management at these dairies was twice as likely to test for drug residues compared with dairies that did not maintain a drug inventory. More information about the DACQA program was requested by more than half of California dairies.

A double-blind block randomized clinical trial on the effect of zinc as a treatment for diarrhea in neonatal Holstein calves under natural challenge conditions.

Diarrhea is the leading cause of death in neonatal calves and contributes to major economic losses. The objective of this double-blind randomized clinical trial was to evaluate the effect of oral inorganic or organic zinc supplementation as a treatment for neonatal diarrhea in calves. Seventy nine 1 to 8 day old male Holstein calves on a California calf ranch were block randomized to one of 3 treatments within 24h from their first onset of diarrhea. Calves received a daily dose of either a placebo composed of 80 mg of zinc-free powder, 381.54 mg of zinc methionine (Met) (equivalent to 80 mg of zinc), or 99.69 mg of zinc oxide (ZO) (equivalent to 80 mg of zinc) in 2L of a zinc-free oral rehydration solution (ORS). Calves were treated once daily until normal fecal consistency or for a maximum of 14 days. Upon enrollment and exit, calves were weighed, and blood, feces, and liver biopsies were collected for trace mineral analysis. Fecal samples at enrollment and exit were tested for E. coli K99, Cryptosporidium spp., rotavirus and coronavirus. Pre-treatment liver zinc concentrations for the 71 calves in the placebo, zinc Met, and ZO treatment groups were 710.6 (SEM=147.7), 852.3 (SEM=129.6), and 750.7 (SEM=202.9)mg/kg dry weight (DW), respectively. Exit liver zinc concentrations for the calves in the placebo, zinc Met, and ZO treatment groups were 728.9 (SEM=182.9), 1141.0 (SEM=423.8), and 636.8 (SEM=81.5)mg/kg dry weight, respectively. Although statistically non-significant, there were clinically important findings identified for each of zinc Met and ZO treatments. Calves treated with zinc Met gained on average 40 g/day during a diarrhea episode compared to a weight loss of 67 g/day on average in the placebo-treated calves (Power 19.9%). Calves treated with ZO had 1.4 times higher hazard of clinical cure compared to calves in the placebo group (Power 5.3%). Calves that were fecal positive to cryptosporidium spp. at enrollment and treated with zinc Met had higher odds of testing negative at exit compared to placebo calves (Odds Ratio (OR)=16.0). In contrast, calves treated with ZO tended to recover (fecal score=1) one day earlier compared to calves treated with a placebo (8.5 d vs. 9.7 d). The current trial identified clinically important findings that warrant further research to investigate zinc's therapeutic effect for calf diarrhea.

Variation in nutrients formulated and nutrients supplied on 5 California dairies.

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.

Characterizing bovine adipocyte distribution and its relationship with carcass and meat characteristics using a finite mixture model.

The appreciation of adipose tissue complexity has initiated a new era of multifaceted investigations that continue to provide findings in adipocyte biology, but quantitative descriptions of adipocyte distribution are lacking. The first objective was to develop a finite mixture model to model adipocyte bimodal distribution and to correlate these estimates with carcass and meat characteristics. A secondary objective was to demonstrate within-animal observed variability in adipocyte cellularity. Steers were finished on a high-grain diet (n = 14) or grass (n = 16). One 12-cm thick LM steak from each steer was collected during harvest. A probability density function was developed that partitioned the cell diameter population into small and large populations and described the relative proportions of cells for each animal in these 2 distinct populations. Five parameters were estimated through the finite mixture model: the means (µ(1) and µ(2)) and SD (σ(1) and σ(2)) for the small and large adipocyte populations, respectively, and a proportion parameter (p) describing the proportion of the distribution of the smaller adipocyte populations. The proportion parameter for all animals tended to be different (P = 0.07) between groups with the grain presenting a p of 22.5 ± 12.5% and grass 16.2 ± 4.7%. The µ(2) was correlated with yield grade (YG, P = 0.04), and σ(2) with final BW, HCW, dressing percentage, YG, and quality grade score (P = 0.01). When correlating these parameters with the sensory data, µ(2) and σ(2) were correlated with tenderness (P ≤ 0.05), σ(1) and p with juiciness (P ≤ 0.05), and p with overall palatability (P = 0.01). Adipocyte cellularity variability was measured by examining the results from 5 randomly chosen steers from each group (grain and grass). In this subset, the µ(1) and p ranged from 32.1 to 46.1 µm and 1 to 27% for grass-finished steers, and ranged from 33.7 to 41.0 µm and 10 to 48% for grain-finished steers. The µ(2) and (1 - p) ranged from 75.0 to 105.1 µm and 73 to 99% for grass-finished steers, respectively, and ranged from 84.8 to 124.0 µm and 52 to 90% for grain-finished steers, respectively. The finite mixture model provides a quantitative description of the distribution of adipocytes and contributes to explaining adipocyte biology. Adipocyte cellularity variability among samples within an animal is a topic that should be further evaluated, as well as its correlation with other factors, such as gene expression and hormone secretion.

Survey of dairy housing and manure management practices in California.

In 2007, a descriptive survey was mailed to all dairies in Glenn (G) and Tulare (T) Counties to identify current and future opportunities of manure management practices on California dairies. The purpose was to provide baseline information for development of outreach curriculum and a decision support tool to quantify potential benefits of various N management options on dairy farms. Such baseline information is valuable to staff regulating dairy facilities (e.g., San Joaquin Valley Unified Air Pollution Control District and Central Valley Regional Water Quality Control Board), dairy trade association representatives, and technology vendors. Response rates for each county were similar at 29.7% (n=19; G) and 26.7% (n=88; T). Mean milking herd size averaged 570 (range 50 to 3,000) cows in G and 1,800 (range 196 to 9,286) cows in T. Survey data are reported by location due to differences between counties in herd size, housing facilities, and climate. Freestalls are common housing facilities (63.2%, G; 38.6%, T) and separated solids and corral scrapings are commonly used as bedding in freestalls (81.8% G and 79.4% T). The most common methods of manure collection were flushing and scraping (18.8%, G; 44.7%, T), only flushing (43.8%, G; 34.1%, T), or only scraping daily or less frequently than daily (37.5%, G; 20.0%, T). Most dairy farms in G (63.2%) and T (70.5%) used some method of separating solids from liquids. However, mechanical separation systems alone were used by 5.3% G and 11.4% T of dairy farms. Storage or treatment ponds were found on 95.9% of dairies. Respondents identified existing manure management practices and did not indicate any new technologies were in use or being considered for manure management. Survey results were used to describe the 2 predominant manure management pathways of manure collection, storage, treatment, and utilization. Survey results will be used to develop and disseminate targeted information on manure treatment technologies, and on-farm evaluation of implemented technologies related to anaerobic digesters, solid liquid separation, and pond additives.