Net Energy Requirements Research Articles

Evaluating the Net Energy Requirements for Maintenance Based on Indirect Calorimetry and Heart Rate Monitoring in Gestating Sows

The objectives of this study were (1) to determine the net energy requirements for the maintenance of gestating sows based on indirect calorimetry, and (2) to explore the feasibility of predicting the net energy requirements for the maintenance of gestating sows based on daily heart rate monitoring. In Exp. 1, six Landrace × Yorkshire crossbred reproductive sows with an initial body weight of 229.5 ± 14.9 kg at d 56 of gestation were randomly assigned to six diverse energy feeding levels using a 6 × 6 Latin square design. The experimental diet was formulated using corn, soybean meal, and wheat bran as major ingredients, and the six feeding levels were set as 1.2, 1.4, 1.6, 1.8, 2.0, and 2.2 times metabolizable energy for maintenance (100 kcal ME/kg BW0.75·d−1), respectively. The animal trial lasted for six periods with 9 days per period, encompassing 5 days of adaptation, 3 days of calorimetry in fed state, and 1 day of calorimetry in fasting state. In Exp. 2, six Landrace × Yorkshire crossbred pregnant sows with an initial body weight of 232.5 ± 12.5 kg at d 64 were fed a corn–soybean meal diet. All sows were tested in a respiratory calorimetry chamber for a 4 day calorimetry test. The heat production of the gestation sows was measured every 5 min using indirect calorimetry, and the heart rate of the gestating sows was recorded every minute using a belt-shape monitor. The results showed that the net energy requirements for the maintenance of gestating sows significant increased as the gestational stage progressed (p < 0.05), and a linear regression model revealed the average net energy requirement for the maintenance of gestating sows was 410 kJ/BW0.75 d−1 during late gestation (days 70–110). Moreover, the average heart rate of the gestating sows was 84 bpm, and the mathematical model developed to predict the net energy requirements for the maintenance of gestating sows was NEm(kcal/h)=19901+exp⁡[136−HR(bpm)43]. In conclusion, the average net energy requirement for the maintenance of sows during late gestation was 410 kJ/BW0.75 d−1, and the utilization of the heart rate monitoring method was found to provide a relevant, accurate prediction for the net energy requirements of sows.

Estimating net energy requirements of male Djallonke sheep

Context Energy requirements in sheep can vary significantly due to various factors, including age, breed, sex and environmental conditions. Genetic selection and crossbreeding further contribute to this variability. Although guidelines from the US and UK national research councils are commonly used for formulating sheep diets, they may not adequately account for the unique characteristics of sheep in Africa. Aims The study aimed to estimate the net maintenance energy requirement of male Djallonke sheep. This estimation will provide a basis for comparing the energy requirements of Djallonke sheep with national recommendations and recent estimates for other sheep breeds. Methods Sixteen entire male Djallonke sheep were selected and grouped by weight. They were then randomly allocated to four treatment groups in a 4 × 4 Latin square design. The sheep were fed to achieve intake levels ranging from 1 to 1.75 multiples of their maintenance energy requirement. Gas exchange data were collected using the GreenFeed system over a 3-day period at the conclusion of each treatment period. Heat production was calculated using the established Brouwer’s equation. A linear regression equation was developed to relate heat production to metabolisable energy intake scaled by metabolic bodyweight to calculate the net energy for maintenance. Key results The estimated net energy for maintenance for male Djallonke sheep was determined to be 0.354 MJ/kg BW0.75. This estimation indicated that the energy requirements of male Djallonke sheep exceeded the recommendations provided by the US National Research Council and the UK Agricultural and Food Research Council. However, it closely aligned with an updated estimate of 0.358 MJ/kg BW0.75. Conclusions Based on the study’s findings, male Djallonke sheep have higher energy requirements for maintenance than what is commonly recommended by existing guidelines. Therefore, it is advisable to update ration formulation software for male Djallonke sheep to better reflect their actual energy requirements for maintenance. Implications These results have practical implications for the formulation of diets and feeding management practices for male Djallonke sheep. Adhering to updated energy requirement estimates can help improve the efficiency and productivity of sheep production in the context of Djallonke sheep farming.

Effect of source and frequency of rumen-protected protein supplementation on mammary gland amino acid metabolism and nitrogen balance of dairy cattle

The AA profile of MP affects mammary gland metabolism and milk N efficiency of dairy cattle. Further, the frequency of dietary protein supplementation may influence N partitioning leading to reduced N excretion. This study investigated the effect of source and frequency of rumen-protected (RP) protein supplementation on apparent total-tract digestibility, milk production, mammary gland AA metabolism, and N balance of dairy cattle. Twenty-eight Holstein-Friesian cows (2.3 ± 0.9 lactations; 93 ± 27 DIM; mean ± SD) were used in a randomized complete block design and fed a basal TMR consisting of 41% corn silage, 32% grass silage, and 27% concentrate (DM basis) and formulated to meet 100% and 95% of net energy and MP requirements, respectively. Cows were adapted to the basal TMR in a freestall barn for 7 d, moved to individual tiestalls for 13 d of adaptation to dietary treatments, and then moved into climate respiration chambers for a 4-d measurement period. Treatments consisted of the basal TMR (CON; 159 g CP/kg DM) or the basal TMR including 1 of 3 iso-MP supplements: (1) 315-g mixture of RP soybean meal and RP rapeseed meal fed daily (ST-RPSR), (2) 384-g mixture of RP His, RP Lys, and RP Met fed daily (ST-RPAA), and (3) 768-g mixture of RP His, RP Lys, and RP Met fed every other day (OS-RPAA). The basal TMR with the addition of treatment supplements was designed to deliver 100% of required MP over a 48-h period. The mixture of His, Lys, and Met was formulated to deliver digestible AA in amounts relative to their concentration in casein. Compared with ST-RPSR, ST-RPAA increased milk protein and fat concentration, increased the arterial concentration of total His, Lys, and Met (HLM), decreased mammary clearance of HLM, and increased clearance of Phe, Leu, and Tyr (tendency for Leu and Tyr). Rumen-protected protein source did not affect N balance, but the marginal use efficiency (efficiency of transfer of RP protein supplement into milk protein) of ST-RPAA (67%) was higher than that of ST-RPSR (17%). Milk protein concentration decreased with OS-RPAA compared with ST-RPAA. Arterial concentration of HLM increased on the nonsupplemented day compared with the supplemented day with OS-RPAA, and there was no difference in arterial HLM concentration across days with ST-RPAA. Mammary uptake of HLM tended to increase on the nonsupplemented day compared with the supplemented day with OS-RPAA. Supplementation frequency of RP AA did not affect N balance or overall milk N efficiency, but the marginal use efficiency of OS-RPAA (49%) was lower compared with ST-RPAA. Overall, mammary glands responded to an increased supply of His, Lys, and Met by reducing efflux of other EAA when RP His, RP Lys, and RP Met were supplemented compared with RP plant proteins. Mammary glands increased sequestration of EAA (primarily HLM) on the nonsupplemented day with OS-RPAA, but supplementing RP AA according to a 24-h oscillating pattern did not increase N efficiency over static supplementation.

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.

Effect of supplementing zilpaterol hydrochloride during different periods on energetics, growth performance, carcass traits and fatty acid profile in meat of finishing lambs

To determine the effect of adding β2 agonist zilpaterol hydrochloride during different periods on growth performance, dietary energetic, carcass traits and fatty acid profile, forty male lambs Pelibuey × Katahdin (37.70 ± 0.83 kg) were blocked by body weight and randomly assigned to pens. Treatments consisted in: 1) control, no zilpaterol supplementation, 2) zilpaterol supplementation for 20 d (ZIL20), 3) zilpaterol supplementation for 30 d (ZIL30), and 4) zilpaterol supplementation for 40 d (ZIL40). Compared with control treatment, zilpaterol supplementation increased final live weight (FLW) (3.5 %; P = 0.0563), average daily gain (ADG, 14.8 %; P = 0.0598) and gain:feed ratio (10.3 %; P = 0.0324). As well as hot carcass weight (6.1 %; P = 0.0064), dress out percentage (2.6 %; P = 0.0139) and Longissimus dorsi muscle area (13.7 %; P = 0.0015). Compared to control group, zilpaterol increased (P = 0.0413) observed vs. expected dietary of NEm (net energy requirements for maintenance) and NEg (net energy requirements for growth) (5.7 and 8.1 %, respectively). Twenty days of zilpaterol treatment improved FLW (4.4 %, P = 0.0566) and tended to improve ADG (17.4 %, P = 0.0718) when compared to control group. Only intramuscular fat showed a positive linear effect (P = 0.0006) in stearic fatty acids proportion and negative linear effect (P = 0.0585) in araquidonic fatty acid proportion. We conclude that zilpaterol hydrochloride improved variables of growth performance, energy retention and carcass traits with noticeable effects from 20 d of zilpaterol supplementation.

Research Note: Effect of fasting time on the fasting heat production, blood metabolites, and body components of layer-type pullets

Fasting heat production (FHP) is used to assess the maintenance net energy requirement of animals. Herein, the FHP of layer-type pullets was estimated. In trial 1, 16 40-day-old Jingfen layer-type pullets were divided into 4 groups of 4 chickens and placed in 4 respiratory chambers. Pullets had free access to feed and water. After 4-d acclimatization, feed was withdrawn, and chickens were measured for FHP for 3 consecutive days. In trial 2, twenty-four 40-day-old pullets were placed in 4 respiratory calorimetry chambers, with 6 pullets per chamber. After 4-d acclimatization, one chamber was randomly selected and all pullets in the chamber was sampled at 5, 25, 50, or 65 h after feed withdrawal. The result showed that FHP declined with fasting time and reached the lowest level between 48 and 72 h. Respiratory quotient was decreased (P < 0.05) between 24 and 48 h compared with that in the first 24 h after fasting. The FHP in the light period showed a significant to decline with fasting time (P < 0.01), whereas the FHP in the dark period was decreased (P < 0.01) 24 h after fasting. Body weight, thigh mass, and abdominal fat decreased (P < 0.05) at 25 h after fasting. Serum glucose were increased (P < 0.01) and while triglycerides were significantly decreased (P < 0.01) at 50 h compared with that at 5 and 25 h time point. The result suggests that the adequate measuring period for FHP for layer-type pullets is from 24 to 48 h after fasting. The FHP of 7-wk-old layer-type pullets was 562.20 kJ/kg of BW0.75/d under a 10-h light and 14-h dark lighting regime.

Performance investigation of solar energy-aided compression-based building air conditioning strategies for variable climatic regions.

Decoupling cooling and ventilation tasks with an existing air conditioning methodology are a promising performance-enhancement technology. In this direction, different configurations of a desiccant-integrated independent ventilation element attached to a conventional cooling system are proposed in this study. This work establishes a quantitative comparative performance analysis among the different process air cooling (obtained through desiccant dehumidification) techniques for three different climates, namely, hot-dry, tropical, and Mediterranean. EnergyPlus simulations have been executed on a small-scale office building of 400-m2 area. The building constructional details and other required simulation input parameters follow benchmark standards. As the chemical dehumidification increases, the process air, i.e., supply air temperature that cannot be sent directly to the room, needs to be cooled. Three approaches for process air cooling have been considered: direct expansion (DX) cooling coil, indirect evaporative cooling (IEC), and sensible heat recovery wheel (SHRW). A solar collector assembly with a supporting heating arrangement is coupled with desiccant unit for regeneration. Outdoor air is used for regeneration in the case of the DX cooling coil and IEC, whereas return air is used in the heat recovery wheel case. Annual simulation results reveal that the SHRW-aided case performs superior than DX coil case for the pertinent climatic conditions, with 9.6 to 45.01% of annual energy savings. For the IEC, energy consumption was 1.8 to 18.38% less than that of DX coil. Also, using return air in this best-suited case reduces the net thermal energy requirement for regeneration by 14.63 to 71.65% with respect to DX coil.

Modeling energy partition patterns of growing pigs fed diets with different net energy levels based on machine learning.

The objectives of this study were to evaluate the energy partition patterns of growing pigs fed diets with different net energy (NE) levels based on machine learning methods, and to develop prediction models for the NE requirement of growing pigs. Twenty-four Duroc × Landrace × Yorkshire crossbred barrows with an initial body weight of 24.90 ± 0.46kg were randomly assigned to 3 dietary treatments, including the low NE group (2,325 kcal/kg), the medium NE group (2,475 kcal/kg), and the high NE group (2,625 kcal/kg). The total feces and urine produced from each pig during each period were collected, to calculate the NE intake, NE retained as protein (NEp), and NE retained as lipid (NEl). A total of 240 sets of data on the energy partition patterns of each pig were collected, 75% of the data in the dataset was randomly selected as the training dataset, and the remaining 25% was set as the testing dataset. Prediction models for the NE requirement of growing pigs were developed using algorithms including multiple linear regression (MR), artificial neural networks (ANN), k-nearest neighbor (KNN), and random forest (RF), and the prediction performance of these models was compared on the testing dataset. The results showed pigs in the low NE group showed a lower average daily gain, lower average daily feed intake, lower NE intake, but greater feed conversion ratio compared to pigs in the high NE group in most growth stages. In addition, pigs in the 3 treatment groups did not show a significant difference in NEp in all growth stages, while pigs in the medium and high NE groups showed greater NEl compared to pig in the low NE group in growth stages from 25 to 55kg (P < 0.05). Among the developed prediction models for NE intake, NEp, and NEl, the ANN models demonstrated the most optimal prediction performance with the smallest root mean square error (RMSE) and the largest R2, while the RF models had the worst prediction performance with the largest RMSE and the smallest R2. In conclusion, diets with varied NE concentrations within a certain range did not affect the NEp of growing pigs, and the models developed with the ANN algorithm could accurately achieve the NE requirement prediction in growing pigs.

Blending gestation and lactation diets during the transition period reduces energy mobilization by sows in late gestation, with no impact on subsequent lactation performance.

Fifty-three gilts and fifty-three multiparous (MP) sows were used to evaluate a blended feeding program using gestation and lactation diets during the transition period on changes in sow back fat (BF) depth and BW, blood metabolites, and litter growth performance in the subsequent lactation period. A 2 × 2 factorial experimental design was generated including the factors of parity and feeding program. The MP sows and gilts were assigned to one of two feeding programs on day 104 ± 1 of gestation: 1) 2kg/d of a standard lactation diet until farrowing when sows received step-up access to the lactation diet until ad libitum access was given on day 4 of lactation (CON) and 2) a dynamic blend of standard gestation and lactation diets that met estimated daily requirements for standardized ileal digestible Lys and net energy according to the NRC (2012) until day 4 of lactation where sows were provided ad libitum access to the lactation diet (TRAN). Litters were standardized to 13 ± 1 piglets within 24-h of birth. In gestation, ADFI was greatest for TRAN-MP sows (interaction; P < 0.05), with greater ADFI for TRAN versus CON sows (main effect; 2.95 vs. 2.13 ± 0.08kg; P < 0.05). Feeding program did not influence ADFI in lactation, but MP sows had greater ADFI versus gilts (main effect; 5.96 vs. 4.47 ± 0.28kg; P < 0.001). Immediately after farrowing, TRAN sows had greater BW and BF vs. CON sows, regardless of parity (main effect; 224.1 vs. 215.4 ± 4.1kg and 17.3 vs. 16.2 ± 0.4mm, respectively; P < 0.05). At weaning, no feeding program-related differences were observed for BW or BF, but MP sows had thicker BF compared to gilts (main effect; 14.4 vs. 13.4 ± 0.5mm; P < 0.05). The TRAN-MP sows had heavier piglets at birth compared to all other groups (interaction; P < 0.05) and MP sows had greater litter birth weight and average piglet BW at birth versus gilts (main effect; P < 0.05). No effect of feeding program was observed for piglet BW at weaning. On lactation day 1, serum beta-hydroxybutyric acid and non-esterified fatty acid concentrations were lower for TRAN compared to CON sows (main effect; 12.0 vs. 19.4 ± 7.8 mmol/L and 0.35 vs. 0.57 ± 0.10 mmol/L, respectively; P < 0.05) and serum glucose concentration was greater for TRAN compared to CON sows (main effect; 4.41 vs. 3.88 ± 0.22 mmol/L; P < 0.05), but these differences were no longer detectable at weaning. Therefore, a simple transition feeding program using a blend of a standard gestation and lactation diets reduced energy mobilization by sows in late gestation, with no impact on subsequent lactation performance.

118 Estimating the Net Energy Requirement of Piglets During the First Three Weeks Post-Weaning

Abstract Previous work has reported that piglets may be unable to increase feed intake to meet energy demands in low-energy diets, contrary to growing pigs. Indeed, poor feed intake in piglets occurs mainly during the first three weeks post-weaning. The approach, in this case, has been to increase the energy density of weaner diets to meet energy requirements even at reduced intakes. Studies estimating the net energy (NE) requirement in piglets in the immediate post-weaning period are lacking. Hence the objective of the present study was to evaluate the dietary NE required to optimize growth and feed efficiency in piglets during the first 21 d post-weaning. A total of 360 mixed-sex piglets (6.4 ± 0.24 kg) were housed with three pigs/pen and 24 pens/treatment (n = 24 pens) and were assigned to 1 of 5 dietary treatments in a dose-response arrangement for 21-d. The experimental diets were formulated to contain graded dietary NE levels (2,200, 2,300, 2,400, 2,500, and 2,600 kcal NE/kg). Diets were isonitrogenous and balanced for amino acids with a constant SID Lys/NE ratio of 1.25 across the treatments. The orthogonal polynomial contrast statement was used in a GLM model (PROC GLM, SAS studio) to determine the linear and quadratic effects of increasing dietary NE level on performance parameters. Results for the overall 21-d period indicated that, as dietary NE increased, average daily gain (ADG) increased linearly (P = 0.03). The average daily feed intake (ADFI) was not significantly (P = 0.157) affected by increasing dietary NE. The gain to feed (G:F) improved linearly as dietary NE increased (P = 0.008). Using the linear-breakpoint model (PROC NLIN), the NE estimated to maximize ADG at 305 g/day was 2,475 kcal NE/kg (P = 0.008). Similarly, for maximum G:F of 0.86 g/g, the linear breakpoint model estimated the NE requirement at 2460 kcal/kg (P = 0.02). No breakpoint was estimated for ADFI, but the model tended (P = 0.08) to show a linear increase in ADFI as NE increased. In summary, the results of this study highlight that, during the first three weeks post-weaning, feed intake of piglets may be more controlled by animal factors (e.g., gut capacity) and, to a lesser extent, energy concentration because feed intake was not affected by the dietary NE level in this study. Further, results show that ADG may be a more accurate measure of the impact of NE concentration than ADFI. In conclusion, dietary NE levels between 2,460 to 2,475 kcal/kg during the first three weeks post-weaning may be ideal to maximize growth performance, provided all other nutrients are not limiting.

218 Simple Blending of Gestation and Lactation Diets During the Transition Period Minimizes Losses in Back Fat Depth Around Parturition for Primi and Multiparous Sows

Abstract Fifty of each primiparous and multiparous sows were used to evaluate a blending feeding program using gestation and lactation diets during the transition period on sow back fat depth (BF), blood metabolites, and litter growth performance. Sows were randomly assigned to one of two feeding programs in a 2×2 factorial design (n = 25) from 104 ± 1 days of gestation: 1) a unique daily blend of standard gestation [0.58% standardized ileal digestible (SID) lysine and 2419kcal/kg NE] and lactation diets (0.95% SID lysine and 2507kcal/kg NE) until day 5 after farrowing to meet estimated daily SID lysine and net energy requirements (NRC, 2012; TRAN) or 2) approximately 2 kg per day of a standard lactation diet until farrowing (CON). Upon farrowing, sows on the CON feeding program received step-up access to the lactation diet according to a feeding curve. Five days after farrowing, both groups received ad libitum access to the lactation diet until weaning (20.0 ± 0.3 days). Sow body weight (BW) and BFwere measured on day 104 and 110 of gestation (BW only), after farrowing, and at weaning. Fasted blood samples were collected from sows at farrowing and weaning. Litters were standardized to 13 ± 1 piglets and were not provided creep feed. During gestation, TRAN sows consumed more feed than CON sows, which was especially evident for multiparous sows (2.95 vs. 2.13 ± 0.08kg/d for TRAN vs. CON; interaction and main effect; P &amp;lt; 0.05). During lactation, average daily feed intake was not influenced by feeding program but was greater for multi versus primiparous sows (5.98 vs. 4.20 ± 0.30kg; P &amp;lt; 0.001). At all time points, BW was greater for multi versus primiparous sows, regardless of feeding program (P &amp;lt; 0.05). During the gestation period, TRAN sows tended to have greater average daily gain (1.43 vs. 1.00±0.39kg/d; P=0.061) and had less back fat loss (-0.18 vs. -0.92 ± 0.37mm; P &amp;lt; 0.05) versus CON sows, regardless of parity. Only after farrowing, TRAN sows had greater BW and BF than CON sows, regardless of parity (221.5 vs. 215.5 ± 4.1kg and 17.0 vs. 16.3 ± 0.4mm; P &amp;lt; 0.05), but at weaning there were no feeding program-related differences in BW or BF. No feeding program-related differences were observed for litter characteristics, but litter birth weight and piglet BW at weaning were greater for multi versus primiparous sows (P&amp;lt; 0.01). Only after farrowing, serum BHBA (11.9 vs. 19.4 ± 7.8mmol/L) and NEFA (0.34 vs. 0.56 ± 0.10mmol/L) concentrations were less and serum glucose concentrations (4.4 vs. 3.9 ± 0.2mmol/L) were greater for TRAN versus CON sows (P &amp;lt; 0.05), regardless of parity. Therefore, a simple transition feeding program using standard gestation and lactation diets reduced energy mobilization by multi and primiparous sows in late gestation, with no impact on subsequent lactation performance.

Energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in the semi-arid region

The purpose of this study was to estimate the carcass composition, and energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in a semi-arid region. Forty-six castrated animals, with initial body weight (BW) of 15.7 ± 0.96 kg, grazing in Caatinga were used. Six animals were slaughtered at the beginning of the experiment representing the initial carcass composition (reference animals; 16.1 ± 1.15 kg BW), while the other animals were randomly distributed in four treatments (concentrate supplementation at 0%, 0.5%, 1.0%, and 1.5% BW), with ten animals per treatment. When one of the animals of each group reached 25 kg BW, all animals in that group were slaughtered. The whole empty body was weighed, ground, homogenized, and sampled for further chemical analyses. The level of supplementation influenced dry matter intake, retained energy, and body weight gain of Canindé goats. The energy (kcal/kg) and fat (g/kg EBW) contents in the carcass of goats of 15, 20, and 25 kg were 2.29 and 86.11, 2.39 and 113.48, and 2.47 and 140.53, respectively. The minimum nitrogen losses were 188 mg N/EBW0.75. The net and metabolizable energy for maintenance were 72.11 kcal/EBW0.75/day and 2.19 g/kg EBW0.75/day, respectively. The net and metabolizable protein requirements were 2.19 and 1.88 g/kg EBW0.75, respectively. The net energy and protein requirements for weight gain ranged from 2.61 to 2.81 Mcal/kg EBW gain and 194.37–222.55 g protein/kg EBW, respectively, for animals from 15 to 25 kg BW. It is concluded that the energy and protein nutritional requirements of Canindé goats supplemented on pasture in the semi-arid region vary according to body weight.

The Energy Contents of Broken Rice for Lactating Dairy Cows.

This study aimed to evaluate (1) the net energy for lactation of broken rice in dairy cows and (2) the effects of broken rice substituting in diets on feed intake, nutrient energy utilization, and milk production. An energy metabolism experiment was conducted using a respiration chamber system in four multiparous Holstein crossbred cows (88.6% Holstein × 11.4% Native Thai; body weight of 438 ± 16.0 kg; 70 ± 31 days in milk) according to a 4 × 4 Latin square design with four 21-d periods. The four dietary treatments included a basal diet substitution with broken rice at 0%, 12%, 24%, and 36%. Increasing the substitution rate of broken rice in the diet resulted in unaffected feed intake, milk yield and composition, and energy balance (p > 0.05); however, a linear increase in the digestibility of dry matter, organic matter, and neutral detergent fiber (p < 0.05). The estimated net energy for lactation of broken rice was 8.68 MJ/kg. The net energy requirement for maintenance was estimated at 504 kJ/kg of metabolic body weight. Our results indicated that broken rice is a good energy-feed resource and that increasing the proportion in the diet up to 36% had no adverse effect on dairy cows' production performance.

Dose response to postruminal urea in lactating dairy cattle

Inclusion of urea in dairy cattle diets is often limited by negative effects of high levels of feed urea on dry matter intake (DMI) and efficiency of rumen N utilization. We hypothesized that supplying urea postruminally would mitigate these limitations and allow greater inclusion of urea in dairy cattle diets. Four rumen-fistulated Holstein-Friesian dairy cows (7 ± 2.1 lactations, 110 ± 30.8 d in milk; mean ± standard deviation) were randomly assigned to a 4 × 4 Latin square design to examine DMI, milk production and composition, digestibility, rumen fermentation, N balance, and plasma constituents in response to 4 levels of urea continuously infused into the abomasum (0, 163, 325, and 488 g/d). Urea doses were targeted to linearly increase the crude protein (CP) content of total DMI (diet plus infusion) by 0%, 2%, 4%, and 6% and equated to 0%, 0.7%, 1.4%, and 2.1% of expected DMI, respectively. Each 28-d infusion period consisted of a 7-d dose step-up period, 14 d of adaptation, and a 7-d measurement period. The diet was fed ad libitum as a total mixed ration [10.9% CP, 42.5% corn silage, 3.5% grass hay, 3.5% wheat straw, and 50.5% concentrate (dry matter basis)] and was formulated to meet 100%, 82%, and 53% of net energy, metabolizable protein, and rumen-degradable protein requirements, respectively. Linear, quadratic, and cubic effects of urea dose were assessed using polynomial regression assuming the fixed effect of treatment and random effects of period and cow. Dry matter intake and energy-corrected milk yield responded quadratically to urea dose, and milk urea content increased linearly with increasing urea dose. Apparent total-tract digestibility of CP increased linearly with increasing urea dose and ruminal NH3-N concentration responded quadratically to urea dose. Mean total VFA concentration was not affected by urea dose. The proportion of N intake excreted in feces decreased linearly and that excreted in urine increased linearly in response to increasing urea dose. The proportion of N intake excreted in milk increased linearly with increasing urea dose. Urinary urea excretion increased linearly with increasing urea dose. Microbial N flow responded cubically to urea dose, but the efficiency of microbial protein synthesis was not affected. Plasma urea concentration increased linearly with increasing urea dose. Regression analysis estimated that when supplemented on top of a low-CP diet, 179 g/d of postruminal urea would maximize DMI at 23.4 kg/d, corresponding to a dietary urea inclusion level of 0.8% of DMI, which is in line with the current recommendations for urea inclusion in dairy cattle diets. Overall, these results indicate that postruminal delivery of urea does not mitigate DMI depression as urea dose increases.

Energy utilization and requirement of broiler breeders during the production phase

This study aimed to evaluate energy utilization and propose models for metabolizable and net energy requirements in broiler breeders during the egg production phase. Sixty Cobb500 broiler breeders aged between 29 and 65 wk were randomly assigned to 3 feeding levels. At each age, 6 birds were adapted for 8 d to 3 levels of metabolizable energy intake (MEi), established based on the amount of feed allocated: 1) the amount of feed recommended in the guideline, 2) 25% above, and 3) 25% below. The birds were housed in respirometry chambers for 6 d (1 adaptation, 4 feeding state, 1 fasting) to measure oxygen consumption and carbon dioxide production to calculate heat production (HP) and fasting HP (FHP). Daily measurements of feed intake, egg weight, egg production, and total excreta were recorded. Variables of MEi, HP, and retained energy (RE) in the egg were calculated, while RE in the body and its partitioning into fat and protein in the egg and body were calculated from MEi, total HP (THP), and RE in the egg. Statistical analysis involved linear regression of multiple factors with MEi and age (categorical) as the independent variables. Pearson correlation analysis was conducted to investigate the relationship between visceral mass and the evaluated variables. The study proposed mixed models for developing models of energy requirements for both metabolizable (ME) and net systems (NE). The study found that FHP (average 259 ± 20.08 kJ/kg0.75*d) remained constant throughout the production cycle regardless of the MEi level (P > 0.05). The efficiency of energy utilization for depositing protein and fat in the body changed with the bird's age. The lower error model was considered to select ME requirements for maintenance, egg, and gain efficiencies, disregarding the effect of age. The efficiencies were 0.89, 0.78, and 0.80 for maintenance, gain, and egg production, respectively. The NE was unaffected by age and showed a lower error than the ME model. The NE system was found to be more accurate in expressing the energy requirements of broiler breeders.

Relationship between feed efficiency and resilience in dairy ewes subjected to acute underfeeding

Selection of dairy sheep based on production levels has caused a loss of rusticity, which might compromise their future resilience to nutritional challenges. Although refocusing breeding programs toward improved feed efficiency (FE) is expected, more-efficient ewes also seem to be more productive. As a first step to examine the relationship between FE and resilience in dairy sheep, in this study we explored the variation in the response to and the recovery from an acute nutritional challenge in high-yielding Assaf ewes phenotypically divergent for FE. First, feed intake, milk yield and composition, and body weight changes were recorded individually over a 3-wk period in a total of 40 sheep fed a total mixed ration (TMR) ad libitum. Data were used to calculate their FE index (FEI, defined as the difference between the actual and predicted intake estimated through net energy requirements for maintenance, production, and weight change). The highest and lowest FE ewes (H-FE and L-FE groups, respectively; 10 animals/group) were selected and then subjected to the nutritional challenge (i.e., withdrawing the TMR and limiting their diet only to the consumption of straw for 3 d). Afterward, sheep were fed again the TMR ad libitum. Temporal patterns of variation in performance traits, and ruminal fermentation and blood parameters were examined. A good consistency between FEI, residual feed intake, and feed conversion ratio was observed. Results supported that H-FE were more productive than L-FE sheep at similar intake level. Average time trends of milk yield generated by a piecewise model suggest that temporal patterns of variation in this trait would be related to prechallenge production level (i.e., H-FE presented quicker response and recovery than L-FE). Considering all studied traits, the overall response to and recovery from underfeeding was apparently similar or even better in H-FE than in L-FE. This would refute the initial hypothesis of a poorer resilience of more-efficient sheep to an acute underfeeding. However, the question remains whether a longer term feed restriction might impair the ability of H-FE ewes to maintain or revert to a high-production status, which would require further research.

Net Energy Value of a Cassava Chip Ration for Lactation in Holstein-Friesian Crossbred Dairy Cattle Estimated by Indirect Calorimetry.

The objectives of this research were to (1) determine the feed intake, digestibility, and energy utilization and (2) estimate the net energy value of cassava chips consumed by lactating dairy cows. Four multiparous Holstein-Friesian crossbred cows at 139 ± 33 (mean ± SD) day in milk were assigned according to a 4 × 4 Latin square design with four periods. The four treatments included a diet substituted with cassava chips on a 0%, 12%, 24%, and 36% dry matter (DM) basis in the basal diet. Indirect calorimetry with a head cage respiration system was used to determine nutrient and energy utilization. Increasing the number of cassava chips in the diet resulted in a linear increase (p < 0.05) in nutrient intake and digestibility but a linear decrease (p < 0.01) in crude protein (CP) and fiber. The enteric methane yield and intensity were not affected (p > 0.05), while energy was lost as feces and urine reduced linearly (p < 0.05). Milk yield and milk composition (protein, fat, lactose) also increased linearly (p < 0.05). The net energy requirement for the maintenance of the lactating cows was estimated as 327 kJ/kg of metabolic body weight, and the efficiency of metabolizable energy used for lactation was 0.66. The estimated net energy value of cassava chips for lactation was 8.03 MJ/kg DM.

Body and milk production traits as indicators of energy requirements and efficiency of purebred Holstein and 3-breed rotational crossbred cows from Viking Red, Montbéliarde, and Holstein sires

This study aimed to compare rotational 3-breed crossbred cows of Viking Red, Montbéliarde, and Holstein breeds with purebred Holstein cows for a range of body measurements, as well as different metrics of the cows' productivity and production efficiency. The study involved 791 cows (440 crossbreds and 351 purebreds), that were managed across 2 herds. Within each herd, crossbreds and purebreds were reared and milked together, fed the same diets, and managed as one group. The heart girth, height at withers, and body length were measured, and body condition score (BCS) was determined on all the cows on a single test day. The body weight (BW) of 225 cows were used to develop an equation to predict BW from body size traits, parity, and days in milk, which was then used to estimate the BW of all the cows. Equations from the literature were used to estimate body protein and lipid contents using the predicted BW and BCS. Evidence suggests that maintenance energy requirements may be closely related to body protein mass, and Holstein and crossbred cows may be different in body composition. Therefore, we computed the requirements of net energy for maintenance (NEM) on the basis either of the metabolic weight (NEM-MW: 0.418 MJ/kg of metabolic BW) or of the estimated body protein mass according to a coefficient (NEM-PM: 0.631 MJ/kg body protein mass) computed on the subset comprising the purebred Holstein. On the same day when body measurements were collected, individual test-day milk yield and fat and protein contents were retrieved once from the official Italian milk recording system, and milk was sampled to determine fresh cheese yield. Measures of NEM were used to scale the production traits. Statistical analyses of all variables included the fixed effects of herd, days in milk, parity, and genetic group (purebred Holstein and crossbred), and the herd × genetic group interaction. External validation of the equation predicting BW yielded a correlation coefficient of 0.94 and an average bias of -4.95 ± 36.81 kg. The crossbreds had similar predicted BW and NEM-MW compared with the Holsteins. However, NEM-PM of crossbreds was 3.8% lower than that of the Holsteins, due to their 11% greater BCS and different estimated body composition. The crossbred cows yielded 4.8% less milk and 3.4% less milk energy than the purebred Holsteins. However, the differences between genetic groups were no longer significant when the production traits were scaled on NEM-PM, suggesting that the crossbreds and purebreds have the same productive ability and efficiency per unit of body protein mass. In conclusion, measures of productivity and efficiency that combine the cows' production capability with traits related to body composition and the energy cost of production seem to be more effective criteria for comparing crossbred and purebred Holstein cows than just milk, fat, and protein yields.

Enteric methane emission estimates for the Zimbabwean Sanga cattle breeds of Tuli and Mashona

The effectiveness of methane mitigation in ruminant livestock production systems depends on the accuracy of estimating methane emission factors and providing accurate emission inventories. Following the Paris Climate agreement, it is recommended that countries adopt the Tier-2 approach for estimating enteric methane emissions from ruminants instead of the Tier-1 approach currently used by most countries. This study sought to provide base line enteric methane emission estimates for the Tuli and Mashona Sanga cattle breeds in Zimbabwe using the IPCC Tier-2 model. Using animal characterization data collected from 412 cattle from Grasslands Research Institute and 406 cattle from Makoholi Research Institute, net energy requirements were estimated. From this and the estimate for digestibility, gross energy intake and dry matter intake were estimated. Gross energy intakes and the estimated methane conversion factor were used to estimate enteric methane emissions. Mean emission factors for Tuli were 45.1, 56, 28.5, 28.4 and 20.6kg CH4/head/year for cows, bulls, heifers, steers and calves, respectively. For Mashona, they were 47.8, 51.9, 29, 29.1 and 20.7 kgCH4/head/year for cows, bulls, heifers, steers and calves, respectively. Generally, estimated Tier-2 emission factors were significantly different from the IPCC Tier-1 default emission factors. This study concluded that enteric methane emission factors estimated using the IPCC Tier-2 model offer insights into the controversial use of the default IPCC Tier-1 emission factors.

Experimental and numerical investigation of drain water heat recovery in a grease interceptor

The European Union declared wastewater as a renewable energy source in its Green Deal. To meet these targets, the scientific community has been proposing new technologies to improve energy conversion efficiency of renewable energy powered thermal systems. The present research examines heat recovery from commercial kitchen grease traps (GT) as a means of reducing the net energy requirement of commercial hot water use in food related activities. A GT was integrated with heat recovery unit and is referred to as a hybrid GT system. Two designs of thermal recovery units comprising a planar and rectangular coil type heat exchanger (HX) were assessed individually to compare their thermal recovery capabilities. The planar HX equipped GT was first experimentally investigated and subsequently examined in more detail using 3D numerical analysis. Thermal stratification was observed along the GT depth for which the rectangular HX showed greater potential for thermal recapture from the high temperature kitchen wastewater. The novel rectangular HX design was found to save 2.6 kW of thermal energy in the kitchen GT and was 48% more efficient compared to the planar HX. The proposed GT hybrid design enables more sustainable production of food via a clean auxiliary thermal back-up, reducing greenhouse gases emission released in water heating. Heat recovery from commercial kitchen GTs has been shown in this study to be technically viable with strong potential for economic viability and positive environmental impact through reducing the carbon footprint of water heating.