H.A. Rossow

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.

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.

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 states 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.

Abstract 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 80mg of zinc-free powder, 381.54mg of zinc methionine (Met) (equivalent to 80mg of zinc), or 99.69mg of zinc oxide (ZO) (equivalent to 80mg 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 40g/day during a diarrhea episode compared to a weight loss of 67g/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 zincs therapeutic effect for calf diarrhea.

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.

Computer Modeling of Obesity Links Theoretical Energetic Measures with Experimental Measures of Fuel Use for Lean and Obese Men

The goal of this research was to use a computational model of human metabolism to predict energy metabolism for lean and obese men. The model is composed of 6 state variables representing amino acids, muscle protein, visceral protein, glucose, triglycerides, and fatty acids (FAs). Differential equations represent carbohydrate, amino acid, and FA uptake and output by tissues based on ATP creation and use for both lean and obese men. Model parameterization is based on data from previous studies. Results from sensitivity analyses indicate that model predictions of resting energy expenditure (REE) and respiratory quotient (RQ) are dependent on FA and glucose oxidation rates with the highest sensitivity coefficients (0.6, 0.8 and 0.43, 0.15, respectively, for lean and obese models). Metabolizable energy (ME) is influenced by ingested energy intake with a sensitivity coefficient of 0.98, and a phosphate-to-oxygen ratio by FA oxidation rate and amino acid oxidation rate (0.32, 0.24 and 0.55, 0.65 for lean and obese models, respectively). Simulations of previously published studies showed that the model is able to predict ME ranging from 6.6 to 9.3 with 0% differences between published and model values, and RQ ranging from 0.79 to 0.86 with 1% differences between published and model values. REEs >7 MJ/d are predicted with 6% differences between published and model values. Glucose oxidation increases by ∼0.59 mol/d, RQ increases by 0.03, REE increases by 2 MJ/d, and heat production increases by 1.8 MJ/d in the obese model compared with lean model simulations. Increased FA oxidation results in higher changes in RQ and lower relative changes in REE. These results suggest that because fat mass is directly related to REE and rate of FA oxidation, body fat content could be used as a predictor of RQ.

Effects of two equine digestive aid supplements on hindgut health1

Abstract Gastrointestinal disease is the number one killer of horses. Little is known about the maintenance of microbes in the equine hindgut and how to distinguish a healthy gut in a live horse. Utilization of internal and external digestibility markers and starch fermentation has been extensively studied in ruminants and is the basis for research conducted on horses. The aims of this study were to investigate the effects of two equine feed digestive aid supplements on hindgut health (HGH) as reflected in fecal pH and digestibility and to compare and validate DM digestibility measurements through the use of internal and external markers such as chromium oxide (CR), lignin (Lig), indigestible ADF (iADF), indigestible NDF (iNDF), and indigestible lignin (iLig). Nine mature Quarter horses (six geldings, three mares) were used in a crossover design, three feeding periods of 17 d (51 d total), using three treatments: control, no feed additive (CON), Smartpak (SP; Plymouth, MA), or Platinum Performance (PP; Buellton, CA). Both SP and PP contained a strain of Lactobacillus, whereas SP further supplied mannanoligosaccharides (MOS) and fructooligosaccharides (FOS) and PP supplied Saccharomyces boulardii. Within the 17-d period, horses were offered orchard grass hay and sweet cob grain and the assigned treatment daily and four CR cookies to deliver 8 g/d of CR for the last 7 d of each period. Total feces were collected from 15 to 17 d. Feed and fecal samples were dried, ground, and sent to ANALAB (Fulton, IL) for nutrient analysis. Duplicate samples of feed and feces were placed in ruminally cannulated cows for in situ determination of iADF, iNDF, and iLig to estimate digestibility. Estimated CR fecal output, CR DMI, and DM digestibilities were evaluated using the root mean square prediction error percentage of the observed mean (RMSPE), concordance correlation coefficient (CCC), and Nash–Sutcliffe efficiency methods. Marker predictive ability tests showed iADF to have the least amount of bias with the smallest RMSPE (4%), largest CCC (0.43), and the largest amount of random bias (error of dispersion = 0.45). Supplementation of PP decreased CR DM digestibility (P < 0.02). Smartpak increased fecal pH (P < 0.09), but PP had no effect on fecal pH. Therefore, SP had a beneficial effect on HGH that is believed to be due to MOS and FOS.

Energetic efficiency and the first law: the California net energy system revisited

Models of energy utilization used in livestock production predict input:output relationships well, for all the wrong reasons. Predictive accuracy in such models is not due to fidelity to biochemistry and laws of thermodynamics, but because they were developed to predict accurately, often with little regard to biochemical consistency. Relatively static linear statistical models limit thermodynamically relevant descriptions of energy utilization, especially maintenance, in growing beef cattle and are inadequate research tools, in either ordinary least squares (OLS) or Bayesian frameworks. Metabolizable energy intake (MEI) at recovered energy (RE) = 0 (MEm) and efficiencies of ME utilization for maintenance (km) and gain (kg) were estimated for 3 independent data sets using OLS or Bayesian frameworks. Estimates of MEm differed (P < 0.05) between OLS and Bayesian estimates and were not unique, indicating model misspecification. Bayesian estimates of MEm were monotonic, positive, and nonlinear f(MEI); the range was from 6.74 to 14.8 Mcal/d. Estimates of km, the ratio of heat energy (HE) at MEI = 0 to MEm, for the 3 data sets averaged 0.590 for OLS solutions, or 0.616 for the first derivative (km, dHE/dMEI for RE = 0) of a first-order function. The first derivative (dHE/dMEI) of the OLS function was > 1.0 for MEI > 22.1 Mcal/d, counter to the laws of thermodynamics and indicated model misspecification. The Bayesian estimate of km (0.420) differed (P < 0.05) from the OLS estimate and was consistent with the efficiency of ATP synthesis. Efficiency of ME use for gain for RE > 0 (kg, OLS solutions) averaged 0.397, solutions were nonunique and single-variable OLS models were misspecified (P < 0.050) for 2 of the 3 data sets. The OLS estimate of kg differed (P < 0.05) from the estimate of kg (0.676) determined in a Bayesian framework; the latter was calculated as dRE/dMEI for RE > 0. For OLS estimates km > kg; for estimates determined in a Bayesian framework km < kg, the former is inconsistent, while the latter is consistent with the thermodynamic favorability of reactions underlying maintenance and gain. Our results show that the use of relatively fixed coefficients of maintenance in current feeding standards, mathematical descriptions of metabolic processes and concepts regarding efficiencies of energy utilization in those systems need modification to be consistent with animal biology and the laws of thermodynamics.