Consensus recommendations on calf- and herd-level passive immunity in dairy calves in the United States.

Passive immunity in calves is evaluated or quantified by measuring serum or plasma IgG or serum total protein within the first 7 d of age. While these measurements inform about circulating concentrations of this important protein, they are also a proxy for evaluating all of the additional benefits of colostral ingestion. The current individual calf standard for categorizing dairy calves with successful passive transfer or failure of passive transfer of immunity are based on serum IgG concentrations of ≥10 and <10 g/L, respectively. This cutoff was based on higher mortality rates in calves with serum IgG <10 g/L. Mortality rates have decreased since 1991, but the percentage of calves with morbidity events has not changed over the same time period. Almost 90% of calves sampled in the USDA National Animal Health Monitoring System's Dairy 2014 study had successful passive immunity based on the dichotomous standard. Based on these observations, a group of calf experts were assembled to evaluate current data and determine if changes to the passive immunity standards were necessary to reduce morbidity and possibly mortality. In addition to the USDA National Animal Health Monitoring System's Dairy 2014 study, other peer-reviewed publications and personal experience were used to identify and evaluate potential standards. Four options were evaluated based on the observed statistical differences between categories. The proposed standard includes 4 serum IgG categories: excellent, good, fair, and poor with serum IgG levels of ≥25.0, 18.0-24.9, 10.0-17.9, and <10 g/L, respectively. At the herd level, we propose an achievable standard of >40, 30, 20, and <10% of calves in the excellent, good, fair, and poor categories, respectively. Because serum IgG concentrations are not practical for on-farm implementation, we provide corresponding serum total protein and %Brix values for use on farm. With one-third of heifer calves in 2014 already meeting the goal of ≥25 g/L serum IgG at 24 h of life, this achievable standard will require more refinement of colostrum management programs on many dairy farms. Implementation of the proposed standard should further reduce the risk of both mortality and morbidity in preweaned dairy calves, improving overall calf health and welfare.

Proposed dairy calf birth certificate data and death loss categorization scheme.

The majority of dairy heifer calves in the United States are destined to be dairy replacements. However, many dairy heifer and bull calves die before 6 mo of age. Of these calves, about 6% (more than 500,000 calves) die at birth or shortly after (i.e., currently termed "stillbirth"). An additional 6% of dairy heifers die during the preweaning period. Death loss in dairy calves is primarily due to stillbirths, failure to adapt to extrauterine life, and infectious disease processes. The reasons for preweaning heifer calf deaths caused by infectious diseases are generally categorized based on easily recognizable clinical signs such as digestive disease/scours or respiratory disease. Most causes of calf death can be mitigated by appropriate preventive care or well-tailored treatments, meaning that the typical death loss percentage could be decreased with better management. Producers could gather information on the circumstances near birth and at death if they had appropriate guidance on what details to record and monitor. This paper provides recommendations on data to collect at the time of birth (i.e., calf birth certificate data). The recording of these critical pieces of information is valuable in evaluating trends over time in morbidity and mortality events in dairy calves. Ideally, necropsy examination would substantially improve the identification of cause of death, but even without necropsy, attribution of cause of death can be improved by more carefully defining death loss categories in on-farm record systems. We propose a death loss categorization scheme that more clearly delineates causes of death. Recommendations are provided for additional data to be collected at the time of death. Recording and analyzing birth certificate and death loss data will allow producers and veterinarians to better evaluate associations between calf risk factors and death, with the goal of reducing dairy calf mortality.

Fatty acid intake alters growth and immunity in milk-fed calves.

The aim of the present study was to determine the effect of supplementing milk replacer (MR) with NeoTec4 (Provimi North America, Brookville, OH), a commercially available blend of butyric acid, coconut oil, and flax oil, on calf growth, efficiency, and indices of immune function. In trial 1a, 48 male Holstein calves were fed either a control MR that contained only animal fat or the same MR with NeoTec4 (treatment) along with free-choice starter. The MR (28.7% crude protein, 15.6% fat) was fed at an average of 1 kg of dry matter (DM)/d. In trial 1b, weaned calves from trial 1a were all fed dry starter for 28 d without NeoTec4 (phase 1), and then half the calves were fed NeoTec4 for 28 d (phase 2). In trial 2, 40 male Holstein calves were fed a control MR with lard, coconut oil, and soy lecithin or the same MR supplemented with NeoTec4 (treatment). The MR (22.8% crude protein, 18.9% fat) was fed at an average of 1 kg of DM/d; no starter was fed. In trial 1a, NeoTec4 improved average daily gain, feed intake, and feed efficiency, reduced the number of days that calves experienced scours, and reduced the medical treatments for clostridium sickness. In trials 1a and 2, NeoTec4 altered the inflammatory response to vaccination with Pasteurella at 5 wk of age and to challenge with Salmonella toxin at less than 2 wk of age (fed NeoTec4 for 6 d), as observed by reduced hyperthermia and hypophagia, and altered the tumor necrosis factor-α response. In addition, NeoTec4 enhanced the response in IL-4 and globular protein estimates postchallenge and enhanced titers for bovine viral diarrhea and respiratory parainfluenza-3. Postchallenge serum concentrations of albumin were lower and urea nitrogen concentrations were greater in control calves than in calves fed NeoTec4. In trial 1b, performance did not differ during the first 28 d when no calves received NeoTec4, but calves receiving NeoTec4 in the second 28 d had greater average daily gain and feed efficiency. We conclude that supplementation of MR with NeoTec4 alters some immune and inflammatory responses, including increasing titers to bovine viral diarrhea and respiratory parainfluenza-3 vaccinations, reduces scours, reduces medical treatments for clostridium sickness, and improves growth rates and feed efficiency.

Insulin sensitivity and responsiveness of portal-drained viscera, liver, hindquarters, and whole body of beef steers weighing 275 or 490 kilograms.

Our objective was to quantify effects of age, weight, and body composition on responsiveness (Rmax or Rmin) and sensitivity (ED50) of several parameters of glucose metabolism to insulin in growing beef steers. Steers ate equal-sized meals every 2 h; the diet contained 62% concentrate and sustained 1 kg ADG. Treatments were euglycemic clamps at 10, 20, 40, 80, 160, and 320 mU.h-1.kg BW-1 of insulin infused into a mesenteric vein of seven younger (275 kg BW) and seven older (490 kg BW) steers. Most steers received three of the six treatments; two extra steers were added to compensate for missing data. Steers had blood vessel catheters and ultrasound flow probes that allowed measurement of net uptake or release of glucose and insulin by portal-drained viscera (PDV), liver, and hindquarters (HQ). Steady-state glucose infusion rate (SSGIR) was intrajugular glucose infused during treatments to maintain euglycemia. Within age groups, Rmax or Rmin and ED50 were estimated by nonlinear regression of glucose flux on arterial plasma insulin concentrations. Steers were killed after sampling, tissues were weighted, and HQ content of fat and protein was determined. Those data were used to predict tissue weights and HQ composition at the time of the euglycemic clamps. Predicted EBW (243 vs 444 kg), liver (4.24 vs 6.19 kg), and HQ (73 vs 122 kg) were heavier for older than for younger steers. Fat in HQ was higher for older than for younger steers (173 vs 134 g/kg), but protein was similar (198 g/kg). The ED50 (mU of insulin/L of plasma) for SSGIR (237 +/- 65 vs 113 +/- 22), liver glucose release (89 +/- 22 vs 44 +/- 11), total glucose entry (418 +/- 184 vs 125 +/- 20), and HQ glucose uptake (488 +/- 151 vs 243 +/- 78) was higher for older than for younger steers. The Rmax (mmol glucose.h-1.kg tissue-1) for SSGIR (2.68 +/- .22 vs 2.09 +/- .23) and HQ (3.08 +/- .33 vs 2.46 +/- .30) was higher for younger than for older steers. Liver glucose release decreased in response to insulin; Rmin (mmol glucose.h-1.kg liver-1) was higher for younger (36.0 +/- 6.9) than for older (24.7 +/- 3.2) steers. We conclude that as steers grew older, heavier, and fatter, their peripheral tissues and liver became less sensitive and less responsive to insulin.

Patterns of nutrient interchange and oxygen use among portal-drained viscera, liver, and hindquarters of beef steers from 235 to 525 kg body weight.

Our objective was to quantify changes in supply and use of nutrients and O2 by large-frame, multicatheterized beef steers as they grew from 235 to 525 kg BW. Steers consumed 5.25 to 9.87 kg DM/d of a 62% concentrate diet that provided 126 to 217 g N/d and 1 kg ADG. Steers were assigned to three groups (eight, nine, and eight steers each) that divided the BW range into thirds. Weights at first sampling for the three groups were 236, 319, and 445 kg, respectively. Each group was sampled twice. Groups were killed after the second sampling. Tissue weights and hindquarters (HQ) contents of fat, protein, and ash were measured. Blood flow, oxygen uptake, and net uptake or release of metabolites were regressed against functions of BW.75 to assess changes during growth. Blood flow in all tissues except liver and oxygen use by all tissues decreased per unit tissue weight as BW.75 and age increased. Changes with age per unit liver weight were as follows: decreased uptake of propionate and lactate, increased uptake of alpha-amino N and glutamine, decreased production of urea and glutamate, and increased production of acetate and beta-hydroxybutyrate. Glucose and urea production per unit liver weight was constant. Changes with age per unit HQ weight were as follows: increased uptake of glucose, decreased uptake of alpha-amino N and glutamate, decreased release of lactate, and increased release of glutamine. Weight of the portal-drained viscera (PDV) increased from 91 to 97 g/kg EBW as BW increased from 236 to 522 kg; PDV fat increased from 375 to 552 g/kg PDV tissues. Liver decreased from 16 to 12 g/kg EBW. Hindquarters decreased from 286 to 266 g/kg EBW; HQ protein was 200, 197, and 200 g/kg HQ tissue for Groups 1, 2, and 3, respectively. Corresponding fat was 131, 182, and 177 g/kg HQ tissue. Changes in net flux reflect changes in nutrient partitioning and tissue deposition as steers grew and aged.

Comparison of insulin infusion sites on metabolite net flux and insulin kinetics in growing euglycemic beef steers.

Four beef steers (average BW, 246 kg) were used in a split-plot design with five bovine insulin (I) infusion rates (5, 10, 20, 40, and 80 mU.kg-1.h-1) in the main plot and two infusion sites, mesenteric (M) and jugular (J) veins, in the subplot. Steers were fed a medium-energy diet at .235 Mcal of ME/kg BW.75 daily in 12 equal feedings at 2-h intervals. Catheters were placed in the mesenteric, hepatic-portal, and hepatic veins and in the abdominal aorta. Blood was sampled from the arterial, portal, and hepatic catheters at 20-min intervals for 1 h before I infusion. Glucose was infused intrajugularly to maintain euglycemia during the I infusion, with arterial glucose monitored at 10- to 15-min intervals. After at least 2.5 h, blood was again sampled at 20-min intervals for 1 h. Blood flow was determined by downstream dilution of p-aminohippurate. Arterial I concentrations (+/- SE) at the greatest I infusion rates were 183.5 +/- 10.46 (J) and 179.0 +/- 6.64 (M) microU/mL. Portal I concentration tended to be greater during M than during J infusion (e.g., J, 199.9 +/- 10.48 vs M, 225.8 +/- 8.99 microU/mL at the greatest dose). Hepatic glucose production at the larger three I doses reached a plateau near 40% of the preinfusion production rate (.57 +/- .02 mmol.kg-1.h-1 vs J, .23 +/- .029 and M, 27 +/- .037). Urea N concentration decreased, but portal uptake or hepatic release of urea N was largely unaffected by I dose or site of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of narasin in chickens and Japanese quail.

Thirty mature chicken hens and 60 mature Japanese quail hens were used to compare pathways of narasin excretion. Carbon-14-labeled narasin was injected into chickens (.7 microCi) and quail (.113 microCi) via cardiac puncture. Blood, sampled at varying times thereafter, and eggs and excreta collected daily for 28 days, were analyzed for 14C. Groups of six chickens and 12 quail were killed prior to [14C]narasin injection and on Days 1, 7, 14, and 28 postinjection to obtain tissue samples for 14C analysis. Blood rapidly cleared the label in both species. Less than 1% of the dose of [14C]narasin remained in blood plasma after 3 h postinjection in both chickens and quail. Label excretion peaked on Day 1 in both species, and most of the 14C was cleared via the excreta (76.7 and 93.6% of the dose for quail and chickens, respectively). Label appeared in the excreta more rapidly and cleared more quickly in quail than in chickens. After 24 h, 68 and 49% of the dose of [14C]narasin appeared in the excreta of quail and chickens, respectively. More label was recovered in the eggs of quail (4.18% of the dose) than in the eggs of chickens (1.32% of the dose). Liver, heart, fat, and ovarian tissues contained traces of radioactivity 1 day postinjection in both species. Muscle and kidney did not contain detectable amounts of label. By Day 7, all tissue had cleared 14C beyond detectable limits. The results indicate that chickens and quail metabolize [14C]narasin via similar pathways and that excretion in quail may be more rapid than in chickens.

Metabolism of decoquinate in chickens and Japanese quail.

Thirty mature chicken hens and 40 mature Japanese quail hens were used in an experiment to compare pathways of decoquinate (DQ) excretion. Labelled DQ was injected into chickens (.5 microCi via wing vein puncture) and quail (.25 microCi via cardiac puncture) on Day 0. Blood was sampled at 0, 1.5, 3, 6, 9, 12, 24, and 48 h postinjection. Eggs and excreta of chickens and quail were collected for 28 and 14 days, respectively, and analyzed for 14C. Six chickens and eight quail were sacrificed prior to 14C-DQ injection and also on Days 1, 7, 14, and 34 or 32 postinjection. Samples of liver, heart, kidney, bile, skin, fat, and muscle were analyzed for 14C. Blood rapidly cleared 14C in both species, and the half-time of 14C excretion via excreta was more rapid in quail (.37 day) than in chickens (.92 day). Little 14C was found in the eggs of quail (.32% of dose) and chickens (.17% of dose). Quail appeared to excrete peak amounts of detectable 14C 1 day earlier (Day 4) than chickens (Day 5). Liver contained the greatest concentration of 14C on Day 1 in both species. By the end of the experiment, less than 1% of the dose remained in liver or other organs. Results indicate that chickens and quail metabolize 14C-DQ at comparable rates and by similar pathways.

Comparative drug depletion in domestic animals and birds.

Decoquinate (Rhone-Poulenc Inc) and Narasin (Eli Lilly and Co) were selected as model drugs for a comparison of metabolism between major (cattle and chickens) and minor (sheep and quail) species. Decoquinate has been studied in all four species. Narasin studies are in progress in chickens and quail. More than 96% of injected 14C-decoquinate (DQ) was eliminated from blood of all species within 1 hr. Disappearance of the remaining 1 to 4% from blood was rapid for all species. Half-times for DQ appearance in excreta were all less than one day. Cumulative excretion of DQ in eggs of chickens and quail was about 1% for both species. Disappearance of DQ from tissues was essentially complete in 14 days. More than 80% of injected 14C-narasin was eliminated from blood within 1/2 hr. Disappearance of the remainder was rapid for both chickens and quail.