Metabolizable Energy Requirements Research Articles

Energy requirements of growing small ruminants raised for meat production in contrasting climatic regions: a meta-analysis

Abstract The objective of this meta-regression was to evaluate the influence of ruminant species, sex, and climatic regions on the metabolizable energy (ME) requirements for maintenance (MEm) and weight gain (MEg) in growing small ruminants raised for meat production across different climatic regions. Data included 655 and 337 treatment means from 173 and 99 studies on sheep and goats, respectively. Metabolizable energy intake (MEI; MJ/kg^0.75) was regressed against average daily gain (ADG; g/kg^0.75), with the study included as a random effect. The analysis found that MEm was not affected by species (P = 0.50), but MEg (MJ/g ADG) was significantly different between species (P = 0.02), with sheep requiring 0.032 (± 0.002) and goats 0.026 (± 0.002) MJ/g ADG. Sex did not affect MEm in either species (P ≥ 0.32). However, in goats, intact males had a greater MEg (P = 0.02) than females (0.030 ± 0.003 vs. 0.013 ± 0.006 MJ/g ADG). MEm was lower (P = 0.03) in small ruminants raised in subtropical regions (0.497 ± 0.046 MJ/kg^0.75) compared to those in semi-arid (0.600 ± 0.038 MJ/kg^0.75) and tended to be lower than those in arid regions (0.529 ± 0.050 MJ/kg^0.75). However, these differences disappeared when adjusting for maturity, diet composition, digestibility, or altitude. MEg was significantly higher (P < 0.05) in animals raised in arid regions (0.032 ± 0.006 MJ/g ADG) compared to those in Mediterranean (0.009 ± 0.004 MJ/g ADG) or semi-arid regions (0.009 ± 0.004 MJ/g ADG) after adjusting for diet composition and digestibility. Similarly, ruminants in Mediterranean regions had lower MEg (0.019 ± 0.004 and 0.009 ± 0.004 MJ/g ADG) than those in tropical regions (0.033 ± 0.002 and 0.024 ± 0.002 MJ/g ADG), respectively after adjusting for maturity, diet composition, and digestibility. MEg in semi-arid regions was consistently lower than in tropical regions, regardless of the covariates tested. For predictive purposes, the global model exhibited the best accuracy (CCC = 0.57 and RSR = 0.79), comparable to the model derived specifically for the tropical region (CCC = 0.58 and RSR = 0.80). This meta-analysis provides a comprehensive evaluation of species-specific differences in ME requirements in small ruminants while recognizing the challenges posed by confounding effects and climatic variability inherent in global datasets. The analysis suggests that animals raised in tropical conditions may have lower MEm than current feeding systems that use data from temperate climates.

Effect of medium-chain fatty acids supplementation on feed intake, rumen fermentation, blood profile, and milk production of dairy cows in the transition period.

Medium-chain fatty acids (MCFAs) are rapidly utilized by the liver as an energy source. However, the effects of feeding MCFAs to dairy cows during the transition period and the subsequent effect on postpartum performance is not well clear. Therefore, this study was to evaluate the effects of MCFAs supplementation on feed intake, rumen fermentation, blood profile, and milk production in dairy cows during their transition period. Twenty-one multiparity Holstein cows were randomly assigned to 2 dietary groups: one group received a diet supplemented with MCFAs calcium salts (MCFA-Ca) from 3 weeks relative to expected parturition to 5 weeks postpartum (MCFA; n = 10), and the other group received the same diet without supplements (control; n = 11). MCFA-Ca containing 80% caprylic acid and 20% capric acid were added to the mixed diet at 1.5% dry matter. During the close-up period (from 3 weeks relative to expected parturition until parturition), cows were fed a TMR with restricted intake to provide 100% of the metabolic energy requirement. Subsequently, the cows were fed a TMR ad libitum from parturition to 5 weeks postpartum. The dry matter intake and body weight did not differ throughout the experimental period between groups. Rumen fermentation and protozoa counts remained unaffected during the experimental period. Supplementation of MCFA had no effect on the plasma concentrations of nonesterified fatty acids and total ketone bodies in cows throughout the experimental period. On the other hand, postpartum plasma glucagon concentration was higher in the MCFA group than in the control group, and milk yield tended to increase in the MCFA group. In conclusion, our results suggested that MCFA-Ca supplementation enhances the catabolic state by affecting pancreatic hormone secretion, resulting in an increase in milk yield during the fresh period without an excessive negative energy balance in dairy cows.

Relationships between paddock-level pasture mass and cow data derived from GPS and behavior-monitoring on-animal sensors in rotationally grazed dairy systems.

Data from behavior-monitoring and location (global positioning system) devices fitted to dairy cows may improve our understanding of how animal behavior and movement are associated with feed availability and quality. We hypothesized that data from behavior-monitoring and location sensors may be associated with feed availability in a paddock within a rotationally grazed dairy system. To investigate this, 100 cows were randomly assigned to one of 4 groups (n = 25 cows per group) and allocated to different target pasture allocations to meet either 80%, 100%, or 120% of their estimated ME requirements across 2 experimental periods (n = 20 d per experimental period), during late spring (experimental period 1; November 7 to November 26, 2021) and late summer (experimental period 2; February 27 to March 18, 2022). During both periods, all 4 groups were allocated 100% of ME requirements for 5 d (baseline). Then, 2 groups were under-allocated (80%), whereas the other 2 groups were over-allocated (120%) for 5 d. Subsequently, all groups returned to baseline for 5 d (100%), followed by a switch, where the under-allocated groups were over-allocated, and vice versa, for the final 5 d. Each cow was fitted with 5 devices that were commercially available in New Zealand and measured rumination, eating, grazing, and lying time, and activity. One device also determined cows' location, and these data were used to derive 3 additional behaviors: distance traveled, mean distance to herd mates, and proximity. These data were used as independent variables to build linear models with pasture mass as the response, which was estimated during the experiment using a calibrated rising plate meter. Distance traveled, standardized by pasture area allocated, was an important variable for explaining the variance in paddock-level pasture mass, alongside mean distance to herd mates and rumination time. Using location variables alone (distance traveled and distance to herd mates), adjusted R2 values were 0.38 and 0.40 for both pre- and postgrazing pasture mass (kg DM/cow), respectively. Further, including both location and behavior, model fit improved due to greater variation in pasture mass explained by these independent variables. The best linear model (adjusted R2 = 0.58) was for postgrazing pasture mass (kg DM/cow) with standardized distance traveled, distance to herd mates, and rumination time included as the independent variables. Model fit varied depending on location and behavior variables included, and devices lacking behavior data related to ingestion and mastication of feed (e.g., rumination, grazing, or eating data) were generally poorer performers. Our results demonstrate the additional value that location-based data can provide. Irrespective of this, predictive potential may be limited due to a moderate amount of variation in pasture mass explained by data from behavior-monitoring and location sensors using linear modeling approaches. Therefore, this method may not be suitably accurate to make near real-time grazing management decisions, but the results are promising as a concept.

Late-gestation maternal undernutrition induces circulatory redistribution while preserving uteroplacental function independent of fetal glycaemic state.

Programming effects of maternal undernutrition on fetal metabolic and cardiovascular systems are well elucidated, yet a detailed characterization of maternal haemodynamics is not available. This study used comprehensive cardiovascular magnetic resonance (CMR) imaging to quantify maternal haemodynamics after 29days (111-140 days) of late-gestation undernutrition (LGUN) in pregnant sheep. Control ewes received 100% of metabolizable energy requirements (MERs, n=15), whereas LGUN ewes were globally nutrient restricted to 50% MER (n=18), with a subset of fetuses undergoing continuous glucose infusion (LGUN+G, n=6/18). Ewes underwent CMR (138-140 days' gestation), and placental tissue was collected the next day. Ewes in both LGUN groups had reduced body weight and mean blood glucose concentration across gestation. Ventricular dimensions were lower in both LGUN groups. Uterine artery blood flow (QUtA) was elevated in the LGUN group compared with controls, whereas peripheral blood flow was reduced and further diminished in LGUN+G. Maternal weight change correlated with all haemodynamic parameters across all groups. Uteroplacental oxygen and glucose delivery were increased in LGUN compared to control ewes, whereas uteroplacental oxygen consumption was preserved. LGUN did not impact placental or fetal weight, and markers of brain-sparing physiology were absent. Placental expression of insulin-like growth factors (IGF-1 and IGF-2) and their receptors, glucose, fatty acid (FA) or amino acid transporters and markers of angiogenesis was not impacted. FA transporter expression was positively correlated with QUtA, and FA binding protein correlated negatively with maternal weight change. Maternal cardiovascular adaptations in response to LGUN manifest as preservation of placental growth and function, thereby preserving fetal growth. KEY POINTS: Maternal undernutrition during pregnancy alters fetal metabolic and cardiovascular physiology, but little is known about alterations in maternal haemodynamics. Late-gestation undernutrition (LGUN) and LGUN+G redirected maternal blood flow from the periphery to the uteroplacental unit, concomitantly increasing the delivery of glucose and oxygen to the uteroplacental unit. Substrate transporter expression and uteroplacental oxygen consumption were preserved in LGUN and LGUN+G, suggesting prioritization of the placenta. This study is the first to report detailed maternal haemodynamics in the setting of maternal undernutrition, where placental growth and function were maintained, ultimately preserving fetal oxygen metabolism and growth.

Feeding twin-bearing Merino ewes above the metabolisable energy requirements for maintenance during late gestation increases the duration of parturition of the first-born lamb

Context In Australia, approximately 53% of lamb deaths are caused by dystocia. One of the main welfare concerns in the sheep industry is under- and overfeeding ewes, which may be contributing to cases of dystocia. Aims This pilot study aimed to investigate how increasing energy intake affects the duration of parturition and predictors of lamb survival. Methods On Day 100 of gestation (dG), 20 twin-bearing and 10 singleton Merino ewes were selected and allocated to three treatment groups; (1) singleton ewes fed at 1.0× maintenance levels (n = 10); (2) twin-bearing ewes fed at 1.0× maintenance levels (n = 10) or (3) twin-bearing ewes fed at 1.25× maintenance (n = 10). Ewes were housed indoors in individual pens. Urine and blood were sampled from ewes on dG 130, 140, then daily from dG 145 through to parturition, and blood was sampled at the onset of parturition and 30 min post-partum. Urine was analysed for pH and blood was analysed for metabolic parameters, mineral concentration and acid–base balance. Predictors of lamb survival from birth to 24 h consisted of weight, rectal temperature, blood glucose and lactate, and body morphology. Key results Serum calcium in late gestation and blood base excess pre-parturition were higher in Singletons 1M compared with Twins 1M (P < 0.05). The Twins 1.25M group took longer to give birth to the first-born lamb (104.4 ± 21.1 min) compared with the Twins 1M group (44.1 ± 6.6 min; P = 0.015). There were no differences in the predictors of lamb survival measures between the twin-bearing groups (P > 0.05). Conclusions Ewes from the Twins 1.25M group took significantly longer to give birth to the first-born lamb. There were no other significant findings between the twin-bearing groups, including lamb liveweight, however, lambs born to ewes from the Twins 1.25 group were numerically heavier, which may explain the increase in parturition length. Implications Feeding ewes above maintenance did not provide any production benefits to metabolic health or any other physiological parameters. Producers should avoid overfeeding ewes during late gestation.

446 A stochastic, dynamic agent-based model of swine nutrient requirements for the growing finishing production phase

Abstract Agent-based modeling (ABM) is a powerful tool that offers the flexibility to represent the stochasticity exhibited by swine systems due to individual animal nutritional requirements. ABM can also accurately mimic the biological dynamic growth performance of pigs. Addressing and simulating the biological growth dynamics enables precision nutrition and sustainable production management. To realistically replicate the nutrient requirement and growth performance of growing-finishing pigs, we developed an ABM based on the principles and equations from the eleventh Swine Nutrient Requirement Council Model. Each individual pig (agent) in the model had a starting weight of 20 kg and a fixed finishing weight of 140 kg, with a variable number of days on feed. Our model considers three sexes: gilt, barrow, and intact male. Pigs move through the farm, feed, and interact with the environment. Our model dynamically simulates the complex interactions between feed intake, metabolism, and growth processes of growing pigs, thereby being a virtual visualizable growing-finishing swine farm (Figure 1). The basic parameters of the biological growth of pigs, including the body weight, feed intake, metabolizable energy (ME) intake, maintenance ME requirements, protein deposition (Pd), lipid deposition (Ld), and probe backfat thickness (Figure 2), were modeled based on NRC equations. In addition to the above parameters, the daily amino acid, calcium (Ca), and phosphorus (P) requirements for individual pigs were calculated daily. To demonstrate ABM responsiveness to feeding strategies, ractopamine supplementation is included to evaluate the impact on protein deposition. The ABM offers more personalized nutrition management by considering unique pig growth potential and nutritional needs based on characteristics such as age and sex, which can lead to improved growth performance and feed efficiency. Besides, the ABM enables the modeling of population-level dynamics and the evaluation of different feeding scenarios to optimize growth outcomes by allocating optimized feed based on individual nutritional needs. Our ABM will be used to test different feeding management strategies and scenarios, providing valuable insights into the impact of various factors on pig nutrition and growth outcomes while minimizing both time and financial expenditures. Our ABM aims to provide a robust framework for simulating and optimizing feeding strategies and enhancing overall pig production efficiency by leveraging the comprehensive and scientifically validated guidelines provided in the NRC. To verify the accuracy and reliability of the proposed ABM, the results generated by the model were rigorously evaluated and compared with the NRC model results. The results demonstrated a highly satisfactory prediction performance by our ABM, paving the way for more real-time decisions to be made for daily feed management on growing-finishing swine operations.

Applying equineRSU and seasonal livestock correction to wider equine stud farm types

ABSTRACT To adjust for potential overestimations in the nitrogen excretion by horses within Overseer®, a revised stock unit system has been proposed (equineRSU). These equineRSU were generated and validated using a medium-sized equine farm as a model farm. The aim of this study was to test the application of the equineRSU and seasonal stock number adjustment on a more complex farming model. Livestock numbers and management data were captured prospectively for the base property (128.8 ha) of a large multi-property commercial breeding stud (3 support properties, 556 ha total area) between June 2022 and May 2023. The monthly on-farm metabolisable energy (ME) requirement and pasture demand were deterministically modelled with both a customised feed budget using livestock class and weight or using the equineRSU and monthly adjusted stock numbers. There were multiple complex movements of horses on and off the property in the different stock classes across the year, with stock management reflecting seasonal periods of high stocking density. There was good agreement (6% variance) between actual ME demand (complex feed budget) and estimated feed demand (simplistic equineRSU model) of 4,387,187 MJ vs 4,102,770 MJ. This suggests that the equineRSU could be used on complex equine farm systems within Overseer®.

Nutritional management of hyperlipaemia in a jenny: a brief report

An adult jenny (5-years-old, non-pregnant) was presented to the Veterinary Teaching Hospital (VTH) of the University of Sassari, with a recent history of appetite loss, extreme underweight condition and reluctance to move. On physical inspection, emaciation [body condition score, BCS: 3/9], muscular waste [muscular condition score, MCS: 1/5], loose/running faeces [faecal score, FS: 2/8], and a general state of mild dehydration were found. Blood analyses outlined a general undernourishment condition [circulating albumins, ALB: 17.6 g/L (21.6–31.6 g/L)] with underlying systemic inflammatory profile and moderate increase in circulating enzymes to explore liver function [aspartate amino-transferase, AST: 657 u/L (279–430 u/L); alanine amino-transferase ALT: 60 u/L (5–14 u/L); gamma-glutamyl-transferase, γ-GT: 87 IU/L (14–69 IU/L); total bilirubin close to the upper limit, TB: 0.20 mg/dL(0.07–0.21 mg/dL)]and hyperlipaemia [TG: 8.70 mmol/L (0.60–2.87 mmol/L)], following fat depots mobilisation, with total cholesterol closed to the lower limit of the physiological range. Hyper-phosphataemia was linked to haemolytic anaemia [P:1.81 mmol/L (0.77–1.39 mmol/L) and red blood cells, RBC: 4.14 1012/L (4.40–7.10 1012)] aligned with the TB to the upper limit. On ultrasound abdominal imaging, enlarged and hyper-echogenic liver was observed. Based on the clinical evaluation, a condition of hepatic lipidosis was diagnosed, requiring dedicated nutritional treatment to solve the extreme emaciation along with the metabolic disorder in support of medical therapy. A two-step feeding protocol was planned to support treatments aiming at immediate re-hydration (Ringer lactate solution 2 ml/kg/8 h). The nutritional objectives were meant at first to restart the voluntary feed intake. Gradual increasing energy provision through a palatable hay-based diet was planned to cover one fourth of daily metabolizable energy requirement calculated on the expected metabolic weight, adjusted according to the daily intake of feed and clinical condition. At the conclusion of this first 7-day phase, circulating blood parameters were closer to the reference values and the BCS moved from 3 to 4 out of 9. Bowel motility was restored, and faecal score improved (4/8). In the second phase, allowance to pasture and a combination diet with compound mixed feed were designed. Within four weeks of starting the nutritional plan, blood parameters were re-established to reference values. The gradual feed provision calculated in this two-phase approach proved successful in support of the overall clinical improvement observed after four weeks of treatment, in a severely undernourished jenny with compromised liver functions.

Simulation of the nutritional requirements and energy balance of adult cows in a northern temperate grassland.

The forage-livestock balance is an important component of natural grassland management, and realizing a balance between the nutrient energy demand of domestic animals and the energy supply of grasslands is the core challenge in forage-livestock management. This study was performed at the Xieertala Ranch in Hulunbuir City, Inner Mongolia. Using the GRAZPLAN and GrazFeed models, we examined the forage-livestock energy balance during different grazing periods and physiological stages of livestock growth under natural grazing conditions. Data on pasture conditions, climatic factors, supplemental feeding, and livestock characteristics, were used to analyze the metabolizable energy (ME), metabolizable energy for maintenance (MEm), and total metabolizable energy intake (MEItotal) of grazing livestock. The results showed that the energy balance between forage and animals differed for adult cows at different physiological stages. In the early lactation period, although the MEItotal was greater than MEm, it did not meet the requirement for ME. MEItotal was greater than ME during mid-lactation, but there was still an energy imbalance in the early and late lactation periods. In the late lactation period, MEItotal could meet ME requirements from April-September. Adult gestational lactating cows with or without calves were unable to meet their ME requirement, especially in the dry period, even though MEItotal was greater than MEm. Adult cows at different physiological stages exhibited differences in daily forage intake and rumen microbial crude protein (MCP) metabolism, and the forage intake by nonpregnant cows decreased as follows: early lactation > mid-lactation > late lactation, pregnant cows' lactation > dry period. For the degradation, digestion and synthesis of rumen MCP, early-lactation cows were similar to those in the mid-lactation group, but both were higher than those in the late-lactation group, while pregnant cows had greater degradation, digestion, and synthesis of MCP in the lactation period relative to the dry period. For lactating cows, especially those with calves, grazing energy requirements, methane emission metabolism and heat production were highest in August, with increased energy expenditure in winter. Overall, grazing energy, methane emissions and heat production by dry cows were low. In the context of global climate change and grassland degradation, managers must adopt different strategies according to the physiological stages of livestock to ensure a forage-livestock balance and the sustainable utilization and development of grasslands.

PSI-15 Effect of feeding intact protein from soybean meal instead of crystalline amino acids on energy and nitrogen balance by growing pigs

Abstract The objective was to test the hypothesis that feeding intact protein from soybean meal (SBM) to growing pigs instead of crystalline amino acids (AA) increases nitrogen (N) retention, digestible energy (DE), and metabolizable energy (ME). A control corn-SBM diet and three diets, in which the inclusion rate of SBM was reduced and 3, 4, or 5 crystalline AA (i.e., Lys, Met, Thr, Trp, Val) were added, were formulated. The concentration of standardized ileal digestible AA was constant among diets, but crude protein was reduced as crystalline AA were added. Pigs were limit fed at 3.2 times the ME requirement for maintenance. Forty pigs (initial body weight = 20.5 kg; SD = 2.4) were allotted to the 4 diets using a randomized complete block design with 2 blocks of 20 pigs with five pigs per diet in each block. Pigs were housed in metabolism crates with pans and screens that allowed for quantitative collection of feces and urine for 4 d after 5 d of adaptation. Samples of diets, feces, and urine were analyzed for gross energy (GE) and N. The statistical model included diet as fixed effect and block as random effect, and pig was the experimental unit. Contrasts coefficients were used to determine linear and quadratic effects of reducing dietary protein. Results indicated that apparent total tract digestibility (ATTD) of dry matter (DM) decreased (quadratic, P = 0.027) and ATTD of GE tended to decrease (quadratic, P = 0.076; Table 1) as SBM inclusion was reduced in the diets. Absorbed N, retained N (g/d), and ATTD of N were decreased (linear, P < 0.001) as SBM decreased in diets, but retention of N (% of intake and % of absorbed) increased (linear, P < 0.001) as SBM decreased in diets. The DE decreased (linear, P = 0.007) as SBM decreased in diets, whereas SBM had no effect on ME. Dietary SBM also had no effect on ME to GE ratio, but ME to DE increased (linear, P = 0.008) by reducing SBM in diets. In conclusion, diets containing intact protein from SBM had greater ATTD of GE and N, and greater DE, but reduced N retention rate when compared with diets containing crystalline AA. However, daily protein retention could not be maintained when crystalline AA rather than SBM were used to furnish the digestible AA in the diets, which may have negative consequences on carcass quality.

81 Effects of udder quarter location on colostrum yield, nutrients, and immunoglobulin G in beef heifers

Abstract We hypothesized that colostrum total nutrients and immunoglobulin G (IgG) would not be affected by side of the udder, but that they would be greater in the rear versus the front half of the udder due to difference in volume of colostrum produced. Complete colostrum yield was collected individually from each quarter pre-suckling [40.5 ± 21.0 min (SD)] from fall-calving crossbred beef heifers (body weight = 472 ± 34 kg; body condition score (= 5.3 ± 0.4) that were either individually-fed 100% (control; n = 12) or 70% (nutrient restricted; n = 12) of NASEM metabolizable energy and metabolizable protein requirements from d 160 of gestation to calving. Analysis of colostrum lactose, protein, triglycerides, and free glucose was performed using colorimetric assays on a UV-visible light microplate reader. Colostrum IgG was analyzed using a commercially available ELISA kit. Quarter yield, nutrient or IgG concentration, and total nutrients or IgG were analyzed using the mixed procedure of SAS with fixed effects of udder location, nutritional plane, and their interaction in the model. Nutritional plane was not part of the current objective, but was included to account for variation in colostrum yield due to nutrient restriction, as we have previously reported. Separate statistical comparisons were made between the front and rear quarters and between the right and left quarters of the udder, with each quarter considered a sampling unit within each experimental unit (half) for both analyses. The interaction of udder location × nutritional plane did not affect (P ≥ 0.11) any variable. Nutrient restriction decreased (P ≤ 0.03) colostrum yield, total lactose, and total free glucose compared with controls. Front quarters produced less volume (P < 0.001; 36.2% of total); total lactose, protein, and free glucose (P ≤ 0.02; 34.3 to 43.3%); and total IgG (P < 0.001; 33.7%) than rear quarters. Front quarters tended to produce less (P = 0.07; 43.3%) total triglycerides than rear quarters. Lactose concentration was 10.5% greater (P = 0.05) in front compared with rear quarters, but other nutrient or IgG concentrations were not affected (P ≥ 0.18). Udder side did not affect total volume (P = 0.78), total nutrients (P ≥ 0.36), or total IgG (P = 0.79). The left side represented 50.7% of the total volume and 50.1 to 53.4% of total nutrients and IgG produced. Concentration of nutrients and IgG also were not affected (P ≥ 0.31) by udder side. In conclusion, colostrum did not differ between udder sides, but, relative to front quarters, rear quarters produced greater nutrient and IgG yield due to greater colostrum volume with minimal differences in nutrient or IgG concentrations.

PSIV-A-4 Effect of late gestational nutrient restriction on locomotor activity of beef heifers

Abstract The objective of this study was to determine the effects of nutrient restriction on locomotor behavior during late gestation. Fall-calving crossbred beef heifers were moved to 3.7 × 15.8 m partially-covered pens and individually-fed 100% (control; n = 13) or 70% (nutrient restricted; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Diets were based on chopped sorghum sudan hay fed in Calan gates and supplemented to meet targeted nutritional planes. IceQube accelerometers (iceRobotics, Edinburgh, UK) were placed on the left hind fetlock between d 158 and 168 of gestation to determine standing time, lying time, step count, number of lying bouts, and motion index. Daily behavior data were averaged for 5 distinct periods (period 1: IceQube placement to d 180 of gestation; period 2: d 181 to 201 of gestation; period 3: d 202 to 222 of gestation; period 4: d 223 to 243 of gestation; and period 5: 244 to 264 of gestation). Days in which animals were moved from their pens were excluded from the data set, resulting in an average of 17.2 ± 2.35 d per period. Data were analyzed with fixed effects of nutritional plane, period, and their interaction in the model. Maternal sire and day of treatment initiation were included as covariates. The number of lying bouts was affected (P = 0.02) by the nutritional plane × period interaction. Within period, there was no effect (P ≥ 0.20) of nutritional plane on lying bouts. Lying bouts in control heifers decreased (P = 0.008) from period 1 to 2, whereas lying bouts in nutrient restricted heifers decreased (P = 0.002) from period 1 to 2 before increasing (P = 0.02) again from period 2 to 3. Motion index and step count were affected (P ≤ 0.05) by nutritional plane, where both were greater in control heifers. Motion index and step count were affected (P < 0.001) by period, while standing time and lying time tended to be affected (P ≤ 0.09) by period. Motion index and step count decreased (P < 0.001) between periods 1 and 2 and periods 3 and 4 but increased (P ≤ 0.004) between periods 2 and 3 and periods 4 and 5. Standing time decreased (P = 0.02), while lying time increased (P = 0.02), between periods 3 and 4. These data suggest that nutrient restricted heifers may have reduced locomotor behavior in late gestation compared with control heifers. Throughout all periods of gestation, control heifers took more daily steps and had a greater motion index, suggesting that nutrient availability in late gestation may directly impact locomotor behavior of beef heifers.

PSIV-A-7 Effects of late gestational nutrient restriction of beef heifers on small intestinal crypt depth in neonatal calves

Abstract We hypothesized that late gestational nutrient restriction would impair small intestinal development in neonatal calves, including crypt cell depth and proliferation. Fall-calving crossbred beef heifers [body weight (BW) = 466 ± 30 (SD) kg; BCS: 5.4 ± 0.5] bred to a single sire were individually-fed 100% (control; n = 10) or 70% (nutrient restricted; n = 12) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Calves were removed from their dams immediately post-calving and fed artificial colostrum and milk replacer relative to body weight until euthanasia at 48.7 ± 0.4 h of age. The gastrointestinal tract was removed, and proximal jejunum samples were dissected from each calf and immersion-fixed in 10% neutral buffered formalin. Tissues were embedded in paraffin blocks and cut into 5-µm sections that were mounted on glass slides. Slides were incubated with Ki-67 (marker of nuclear proliferation) and counterstained with Hematoxylin using an autostainer. Images were taken at 5× magnification using an upright microscope. QuPath software was used to measure crypt depth, starting at the base of the crypt region and ending at the furthest cluster of Ki-67 positive cells, perpendicular to the base of the mucosa. For each calf, 10 crypt depth measurements were taken from 4 images, resulting in 40 crypt depth measurements that were averaged. Nutritional plane was a fixed effect in the model, and maternal sire, date of study initiation, and calf sex (when P < 0.25) were considered covariates. We previously reported that calves born to nutrient restricted dams weighed less (P ≤ 0.05) at birth and 48 h than calves born to control dams. Small intestinal mass tended to be less (P = 0.11) in offspring of nutrient restricted dams but was not affected (P = 0.58) when expressed relative to body weight. Calves born to nutrient restricted dams also tended to have less (P = 0.11) small intestinal mass relative to brain weight. Maternal nutrient restriction did not affect (P = 0.95) jejunal crypt depth. Additionally, crypt depth relative to body weight was not affected (P = 0.20) by nutrient restriction. Although crypt depth was not affected, further analysis of proliferation and morphology will help to understand the relationship between maternal nutrient restriction and small intestine development in neonatal calves.

Energy requirement for primiparous Holstein × Gyr crossbred dairy cows

Our objective was to estimate the requirements of metabolizable energy (ME) and NEM of lactating and dry cows, the efficiency of ME utilization for milk production (kl) and tissue gain (kg), and the use of body energy mobilization for milk production (kt) throughout the lactation of primiparous crossbred Holstein × Gyr cows, using open-circuit respiration chambers. Twenty-nine primiparous Holstein × Gyr crossbred cows with an initial BW averaging 563 ± 40.1 kg and 2.5 ± 0.09 yr old were used throughout lactation and dry periods. The cows were kept nonpregnant throughout the study to eliminate possible confounding factors. Apparent digestibility assays, followed by calorimeter measurements, were performed 6 times throughout the lactation period. In the dry-off period, the cows were also evaluated but fed with restricted intake (DMI = 1.1% BW/d) to achieve heat production close to maintenance. After 21 d of diet adaptation, an apparent digestibility assay followed by calorimeter measurements was performed. Parameter estimates for lactation period were obtained by mixed models including lactation stage as repeated measures. For restricted feeding at dry-off and fasting period assays, the requirements were estimated by exponential regression. For whole lactation, the values of the ME requirement for maintenance (MEM) and NEM were 0.588 and 0.395 MJ/BW0.75, respectively. The efficiencies of kl, kg, and kt were 0.672, 0.771, and 0.814, respectively. However, MEM and NEM were higher in early and mid lactation than late, whereas kl was higher in early than other lactation stages. Dry and nonpregnant cows had MEM of 0.434 MJ/BW0.75 and NEM of 0.351 MJ/BW0.75 for maintenance level, and MEM of 0.396 MJ/BW0.75 and NEM of 0.345 MJ/BW0.75 for fasting metabolism level, and efficiency of ME utilization for maintenance was 0.80. Our findings confirmed that F1 crossbred Holstein × Gyr dairy cows have differences in energy requirement and efficiency throughout the lactation stages, suggesting the use of different values in each stage. The estimated values of energy requirement for maintenance and efficiencies for primiparous lactating crossbred Holstein × Gyr were similar to those reported in the literature in specific studies and requirements systems.

Increasing midtarsal joint stiffness reduces triceps surae metabolic costs in walking simulations but has little effect on total stance limb metabolic cost

The human foot’s arch is thought to be beneficial for efficient gait. This study addresses the extent to which arch stiffness changes alter the metabolic energy requirements of human gait. Computational musculoskeletal simulations of steady state walking using direct collocation were performed. Across a range of foot arch stiffnesses, the metabolic cost of transport decreased by less than 1% with increasing foot arch stiffness. Increasing arch stiffness increased the metabolic efficiency of the triceps surae during push-off, but these changes were almost entirely offset by other muscle groups consuming more energy with increasing foot arch stiffness.

Effects of late gestational nutrient restriction on uterine artery blood flow, placental size, and cotyledonary mRNA expression in primiparous beef females.

Fall-calving primiparous beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were individually-fed either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to parturition. Doppler ultrasonography of both uterine arteries was conducted pre-treatment and every 21 d from days 181 to 265 of gestation. Expelled placentas were collected, and ipsilateral cotyledonary tissue was sampled to assess relative messenger ribonucleic acid (mRNA) expression. Placentas were separated into ipsilateral and contralateral sides, dissected (cotyledonary vs. intercotyledonary), and dried. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Uterine blood flow included day and nutritional plane × day as repeated measures. We previously reported that post-calving, NR dams weighed 64 kg less and were 2.0 BCS lower than CON, but calf birth weight was not affected. Maternal heart rate was less (P < 0.001) for NR dams than CON after nutritional planes began. Nutritional plane did not affect (P ≥ 0.20) uterine artery hemodynamics, but all variables were affected (P ≤ 0.04) by day. Contralateral cotyledonary and placental weight were less (P ≤ 0.04) and contralateral intercotyledonary weight and number of cotyledons tended to be less (P ≤ 0.10) for NR dams than CON, but ipsilateral and whole placental weights were not affected (P ≥ 0.13). Ipsilateral placental weight as a percentage of total placental weight was greater (P = 0.03) for NR dams than CON. Whole placental cotyledonary: intercotyledonary weight was less (P = 0.01) for NR dams than CON. Placental efficiency was not affected (P = 0.89) by nutritional plane. Cotyledonary relative mRNA expression of GLUT3 and SNAT2 was greater (P ≤ 0.05) and relative expression of GLUT1, GLUT4, and NOS3 tended to be greater (P ≤ 0.07) for NR dams than CON. Nutritional plane did not affect (P ≥ 0.13) relative mRNA expression of GLUT5, 4F2hc, CAT1, LAT1, LAT2, VEGFA, FLT1, KDR, GUCY1B3, and PAG2. Despite less contralateral placental growth, beef heifers experiencing late gestational nutrient restriction maintained uterine artery blood flow and total placental mass and had 4 nutrient transporters and 1 angiogenic factor upregulated in cotyledons, all of which likely contributed to conserving fetal growth.

Late gestational nutrient restriction in primiparous beef females: Performance and metabolic status of lactating dams and pre-weaning calves.

Fall-calving primiparous beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were individually-fed 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of estimated metabolizable energy and metabolizable protein requirements from day 160 of gestation to calving. Post-calving, all dams were individually-fed tall fescue hay supplemented to meet estimated nutrient requirements for maintenance, growth, and lactation in Calan gates until day 149 of lactation, which limited calves to milk only. From day 150 of lactation until weaning at day 243, dams and calves were group-fed in drylots. Dam BW and metabolic status were determined every 21 d, and BCS and backfat (BF) were determined every 42 d of lactation until weaning. Pre-weaning calf BW, size, and metabolic status were determined every 21 d. Data were analyzed with nutritional plane, calving date, and calf sex (when P < 0.25) as fixed effects. Circulating metabolites included day and nutritional plane × day as repeated measures. We previously reported that post-calving, NR dams were 64kg and 2.0 BCS less than CON, but calf BW and size at birth were not affected. During the first 147 d of lactation, NR dams gained more (P < 0.01) BW than CON and increased (P < 0.01) BCS, while CON decreased (P ≤ 0.01) BCS and BF. Previously, NR dams had lower (P < 0.01) circulating triglycerides on day 1 of lactation, tended to have lower (P = 0.08) triglycerides on day 21, and had lower (P ≤ 0.04) non-esterified fatty acids (NEFA) on days 21 and 243 than CON. Maternal glucose and urea N were not affected (P ≥ 0.73). At weaning, NR dams weighed 17kg less (P = 0.15), were 0.67 BCS lower (P < 0.01), and tended to have less (P = 0.06) BF. Calves born to NR dams weighed less (P = 0.02) than CON by day 42 of age and were 13% smaller (P < 0.01) at weaning. Calf girth measures diverged (P ≤ 0.05) by day 21 of age, and skeletal size measures were less (P ≤ 0.08) for calves born to NR dams at most timepoints after day 63 of age. Calves born to NR dams tended to have lower (P = 0.09) circulating urea N pre-weaning than CON, but glucose, triglycerides, and NEFA were not affected (P ≥ 0.16). In summary, first-parity beef females that were nutrient restricted during late gestation experienced compensatory growth and gained body condition during lactation but were still thinner at weaning. Nutrient restriction reduced pre-weaning calf growth, likely due to decreased milk production.

Estimating the magnitude and sensitivity of energy fluxes for stickleback hosts and Schistocephalus solidus parasites using the metabolic theory of ecology.

Parasites are ubiquitous, yet their effects on hosts are difficult to quantify and generalize across ecosystems. One promising metric of parasitic impact uses the metabolic theory of ecology (MTE) to calculate energy flux, an estimate of energy lost to parasites. We investigated the feasibility of using metabolic scaling rules to compare the energetic burden of parasitism among individuals. Specifically, we found substantial sensitivity of energy flux estimates to input parameters used in the MTE equation when using available data from a model host-parasite system (Gasterosteus aculeatus and Schistocephalus solidus). Using literature values, size data from parasitized wild fish, and a respirometry experiment, we estimate that a single S. solidus tapeworm may extract up to 32% of its stickleback host's baseline metabolic energy requirement, and that parasites in multiple infections may collectively extract up to 46%. The amount of energy siphoned from stickleback to tapeworms is large but did not instigate an increase in respiration rate in the current study. This emphasizes the importance of future work focusing on how parasites influence ecosystem energetics. The approach of using the MTE to calculate energy flux provides great promise as a quantitative foundation for such estimates and provides a more concrete metric of parasite impact on hosts than parasite abundance alone.

Integrative transcriptomics and proteomics profiling of Arabidopsis thaliana elucidates novel mechanisms underlying spaceflight adaptation.

Spaceflight presents a unique environment with complex stressors, including microgravity and radiation, that can influence plant physiology at molecular levels. Combining transcriptomics and proteomics approaches, this research gives insights into the coordination of transcriptome and proteome in Arabidopsis' molecular and physiological responses to Spaceflight environmental stress. Arabidopsis seedlings were germinated and grown in microgravity (µg) aboard the International Space Station (ISS) in NASA Biological Research in Canisters - Light Emitting Diode (BRIC LED) hardware, with the ground control established on Earth. At 10 days old, seedlings were frozen in RNA-later and returned to Earth. RNA-seq transcriptomics and TMT-labeled LC-MS/MS proteomic analysis of cellular fractionates from the plant tissues suggest the alteration of the photosynthetic machinery (PSII and PSI) in spaceflight, with the plant shifting photosystem core-regulatory proteins in an organ-specific manner to adapt to the microgravity environment. An overview of the ribosome, spliceosome, and proteasome activities in spaceflight revealed a significant abundance of transcripts and proteins involved in protease binding, nuclease activities, and mRNA binding in spaceflight, while those involved in tRNA binding, exoribonuclease activity, and RNA helicase activity were less abundant in spaceflight. CELLULOSE SYNTHASES (CESA1, CESA3, CESA5, CESA7) and CELLULOSE-LIKE PROTEINS (CSLE1, CSLG3), involved in cellulose deposition and TUBULIN COFACTOR B (TFCB) had reduced abundance in spaceflight. This contrasts with the increased expression of UDP-ARABINOPYRANOSE MUTASEs, involved in the biosynthesis of cell wall non-cellulosic polysaccharides, in spaceflight. Both transcripts and proteome suggested an altered polar auxin redistribution, lipid, and ionic intracellular transportation in spaceflight. Analyses also suggest an increased metabolic energy requirement for plants in Space than on Earth, hence, the activation of several shunt metabolic pathways. This study provides novel insights, based on integrated RNA and protein data, on how plants adapt to the spaceflight environment and it is a step further at achieving sustainable crop production in Space.

Great tits (Parus major) in a west European temperate forest show little seasonal variation in metabolic energy requirements

Understanding how birds annually allocate energy to cope with changing environmental conditions and physiological states is a crucial question in avian ecology. There are several hypotheses to explain species' energy allocation. One prominent hypothesis suggests higher energy expenditure in winter due to increased thermoregulatory costs. The "reallocation" hypothesis suggests no net difference in seasonal energy requirements, while the "increased demand" hypothesis predicts higher energy requirements during the breeding season. Birds are expected to adjust their mass and/or metabolic intensity in ways that are consistent with their energy requirements. Here, we look for metabolic signatures of seasonal variation in energy requirements of a resident passerine of a temperate-zone (great tit, Parus major). To do so, we measured whole-body and mass-independent basal (BMR), summit (Msum), and field (FMR) metabolic rates during late winter and during breeding in Belgian great tits. During the breeding season, birds had on average 10% higher whole-body BMR and FMR compared to winter, while their Msum decreased by 7% from winter to breeding. Mass-independent metabolic rates showed a 10% increase in BMR and a 7% decrease in Msum from winter to breeding. Whole-body BMR was correlated with Msum, but this relationship did not hold for mass-independent metabolic rates. The modest seasonal change we observed suggests that great tits in our temperature study area maintain a largely stable energy budget throughout the year, which appears mostly consistent with the reallocation hypothesis.