Metabolizable Energy For Maintenance Research Articles

286 Impact of feeding strategies on bodyweight and body condition in mature AI boars

Abstract The objective of this experiment was to determine how varying feeding strategies for boars impacts body weight (BW), backfat depth, loin muscle depth, Knauer caliper measurements, flank to flank tape measurement, body condition score (BCS), and scrotal width and length. This experiment was conducted over two 9-wk periods. Boars were weighed and measurements were taken every 3 wk during the study. Boars (n = 28; Acuity and Topig Norvsin) from two age groups (9 and 15 mo) and two genetic lines (maternal and terminal) were used during this experiment. Boars were blocked by breed and age and randomly allocated to receive one of the three feed intake (FI) levels of a corn-soybean meal-based diet (met NRC 2012 nutrient requirements) using the NRC (2012) maintenance equation [ME for maintenance = (100*kg BW0.75) + 15 kcal for sperm production]. Treatments were: HIGH (150% of maintenance, n = 9), MAIN (100% of maintenance, n = 10), LOW (80% of maintenance, n = 9) for the first 9-wk period. During the second 9-wk period remaining HIGH and LOW boars were crossed-over to opposite treatments (HIGH-LOW, n = 9; LOW-HIGH, n = 7) and maintenance remained unchanged (MAIN-MAIN, n = 8). Data were analyzed using PROC MIXED in SAS 9.4. Boar was the experimental unit with main effects of feed intake and age, and week serving as a repeated measure. Significance was determined at P < 0.05 and a trend at 0.05 < P ≤ 0.10. Three-way interactions of FI*Age*Week were observed during the first 9-wk period. Young boars fed HIGH had a greater increase in BW (P = 0.002), caliper (P = 0.011), backfat depth (P = 0.003), BCS (P = 0.003), and scrotal width (P = 0.004) than old boars fed HIGH and young boars fed LOW had a greater reduction in these variables then old LOW boars. Boars fed LOW for the first 9-wk period had reduced scrotal length (P = 0.004), greater reduction in BW change (P < 0.001), and reduced tape change (P = 0.021) compared with HIGH and MAIN fed boars. Two-way interactions for the second 9-wk period were observed. HIGH-LOW fed boars had decreased BW (FI*Week; P < 0.001), tape (FI*Week; P = 0.019), caliper (FI*Week; P = 0.012), BCS (FI*Week; P < 0.001), and scrotal width (FI*Week; P = 0.047) while LOW-HIGH boars had increased measurements for these variables over time. Additional two-way interactions during the second 9-wk period included Tape (FI*Age; P = 0.046) and BCS (FI*Age; P = 0.028). Overall young boars had more adverse reactions to the varying feeding strategies than old boars, this included larger changes in BW and composition measures. Young and old boars fed MAIN level lost BW and condition indicating the equation for maintenance energy requirement is not accurate for modern genetics working boars. Future research is needed with varying ages and feed intakes in the boar stud to better understand the impacts of growth, development, and maintenance energy for the modern AI boar.

PSII-11 Supplementation of Non-Protein Nitrogen to a Nitrogen-Deficient Diet Increases Lysine Requirement for Nitrogen-Retention

Abstract Low protein (LP) diets have improved nutrient utilization while maintaining animal performance. Regardless, these diets may be limiting in nitrogen (N) content to meet non-essential amino acid (NEAA) requirements, potentially altering essential amino acid (EAA) utilization and requirements. Inclusion of a non-protein nitrogen (NPN) may be beneficial for improving utilization of EAA in LP diets. The objective of this study was to determine the impact of NPN in an N-deficient diet, as indicated by EAA-N:total N ratio (EAA-N:TN) on the Lys requirement for nitrogen retention (NR). A total of 90 growing barrows (initial BW of 20.4 ± 0.46 kg) were randomly assigned to 1 of 10 dietary treatments (n = 9 pigs/treatment) in 9 blocks in a 2 × 5 factorial design. Diets contained no ammonium phosphate (NAP; EAA-N:TN of 0.56) or were supplemented with 1.7% ammonium phosphate (AP; EAA-N:TN of 0.50) with graded levels of dietary lysine [Lys; 0.8%, 0.9%, 1.0%, 1.1% and 1.2% standardized ileal digestible (SID)]. Diets were corn and soybean meal-based and formulated to meet or exceed nutrient requirements according to NRC (2012). Diets were fed at 2.8 × maintenance metabolizable energy requirements in two equal meals per day. A 4-d nitrogen balance collection period was conducted following a 7-d dietary adaptation period. Urine was collected quantitatively, and fresh fecal samples were obtained daily. Nitrogen retention was determined as the difference between N intake and output (fecal and urinary). Linear breakpoint modeling with PROC NLIN was used to estimate Lys requirement. Nitrogen retention was optimized at 1.00% SID Lys (15.6 g/d NR; R2 = 0.68) in pigs fed NAP diets and 1.09% SID Lys (16.4 g/d NR; R2 = 0.61) in pigs fed AP diets. Overall, deficient dietary N reduced NR and Lys requirement, which were increased with NPN supplementation.

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.

Heritability of beef cow metabolizable energy for maintenance.

Most of the metabolizable energy that a cow uses during a production year is for maintenance; however, less is known about the heritability of maintenance compared to other traits that can be measured directly. Feed intake is a heritable trait in the mature cow and most of the feed consumed is used for maintenance. We hypothesized that maintenance energy was a heritable trait. Individual feed intake was measured for 84 or 85 d on 5 yr old pregnant cows (N = 887) from a pedigreed population of cattle that represent prominent breeds in the United States. Phenotypic mean (± SD) values were 654 ± 68 kg for cow body weight, 0.21 ± 0.24 kg/d for average daily gain, and 175 ± 17 d for midpoint fetal age. Dry matter intake averaged (± SD) 10.84 ± 1.41 kg/d. Metabolizable energy for maintenance was estimated by subtracting the metabolizable energy used for conceptus growth and tissue accretion from metabolizable energy intake. Metabolizable energy for maintenance averaged (± SD) 139 ± 18 ME kcal/d/BW kg0.75 and had a heritability of 0.31 ± 0.11. Cows have a moderate heritability for maintenance suggesting an opportunity for selection.

274 Effects of Feeding Levels in Early Gestation on PIC Camborough Sows and Litter Performance

Abstract Our objective was to determine the effects of increasing feeding levels for PIC Camborough sows during early gestation on sow and litter performance. A total of 636 sows (PIC Camborough) were randomly assigned at weaning to 1 of 4 treatments that were balanced for weight and caliper scores within parity categories. Treatments consisted of feeding sows with daily feed allowances to meet 85, 115, 145, or 175% of the NRC (2012) maintenance metabolizable energy (MEm) requirement calculated as MEm, kcal/d = 100 × (body weight, kg)0.75. A common corn-soybean meal-distillers dried grains with solubles-based diet with 3,092 kcal of ME/kg and 0.64% standardized ileal digestible lysine was used. Treatments were applied from d 6 to 35 of gestation, after which sows were moved to gestation pens and fed according to body condition through an electronic sow feeder until moved to the farrowing room. Sow was the experimental unit and data were analyzed using generalized linear mixed models with the lmer and glmer functions of R. On average, females were ideal condition at weaning across treatment as determined by the caliper scores. Average feed allowances were 1.6, 2.1, 2.6, and 3.2 kg/day for the 85, 115, 145, and 175% treatments, respectively. Increasing feed allowances reduced (linear, P< 0.05) body weight loss (-13.8, -10.3, -4.7 and -0.5 kg, respectively) and increased caliper score gain (-0.43, -0.03, 0.64, 0.76 units, respectively) from weaning to d 35 of gestation. There was no evidence for treatment effects on farrowing rate, total born, stillborn rate, average litter weight, piglet throughput, or subsequent reproductive performance. In summary, increasing feed allowances to meet 85 to 175% of the MEm requirements during early gestation on Camborough sows resulted in a reduction in body weight loss and an improvement in caliper gain until d 35 of gestation without evidence of impact in reproductive performance.

257 Effect of the Essential Amino Acid-Nitrogen to Total Nitrogen Ratio on Lysine Requirement for Nitrogen Retention in Growing Pigs

Abstract Low-protein (LP) diets may become limiting in nitrogen (N), affecting utilization of essential amino acids (EAA) for nitrogen retention (NR). The objective of the present study was to determine the effect of the EAA-N to total N ratio (EAA-N:TN) on lysine (Lys) requirement for NR. A total of 80 growing barrows (21.5±0.89 kg initial BW) were randomly assigned to 1 of 10 dietary treatments (n=8 pigs/treatment) in 8 blocks in a 2 × 5 factorial arrangement with factors of EAA-N:TN (low vs. high) and Lys content (0.82, 0.92, 1.02, 1.12, and 1.22% standardized ileal digestible [SID] Lys). Diets were formulated to meet EAA requirements with the low ratio diet (LR; 16.8% crude protein) having an ideal EAA-N:TN of 0.48 and the high ratio diet (HR; 15.5% crude protein) formulated to be limiting in NEAA with an EAA-N:TN of 0.55. Diets were fed at 2.8 × maintenance metabolizable energy requirements. After a 7-d dietary adaptation, a 4-d N-balance period was conducted where fresh fecal samples were collected daily and quantitative urine samples were collected over a 24-h period. Nitrogen-balance was determined as the difference between N intake minus fecal and urinary N output. Data were analyzed using a MIXED model with fixed effects of ratio, Lys, and their interactions, and block as a random effect. Lysine requirement based on two-phase linear or quadratic modeling was estimated using PROC NLIN. Nitrogen retention increased linearly with increasing Lys levels regardless of ratio (P< 0.01). Quadratic modelling estimated the Lys requirement to maximize NR at 17.83 g/d in pigs fed HR diets at 1.21% SID (R2 = 0.53; P< 0.05), but no breakpoint was achieved for pigs fed LR diets, which showed a linear response (R2 = 0.79; P< 0.05). These results suggest that NR is limited by NEAA or TN in HR diets.

152 Effects of Feeding Levels in Early Gestation on PIC Terminal Sows and Litter Performance

Abstract Our objective was to determine the effects of increasing feeding levels for terminal line sows during early gestation on sow and litter performance. A total of 615 PIC L65 (213.3 kg ± 1.51) parity 1 to 3 sows were randomly assigned at weaning to 1 of 4 treatments within parity in a randomized complete block design with body weight blocks. Treatments consisted of feeding sows with daily feed allowances to meet 85, 100, 120, or 150% of the NRC (2012) maintenance metabolizable energy (MEm) requirement calculated as MEm, kcal/d = 100×(body weight, kg)0.75. A common corn-soybean meal-wheat-based diet with 3,018 kcal of ME/kg and 0.63% standardized ileal digestible lysine was used. Treatments were applied from d 5 to 30 of gestation, after which they were fed according to body condition until moved to the farrowing room. Sow was the experimental unit and data were analyzed using generalized linear mixed models with the lmer and glmer functions of R. Average caliper score at weaning was 14.4 across treatments and average feed allowances were 1.6, 1.8, 2.2, and 2.8 kg/d for the 85, 100, 120, and 150% treatments, respectively. Increasing feed allowances increased (linear, P < 0.001) weight change (-1.9, 2.3, 4.9 and 7.9 kg, respectively) and caliper score change (0.0, 0.2, 0.7, 0.7 units, respectively) from weaning to d 30 of gestation. There was no evidence for treatment effects on farrowing rate, caliper score at farrowing, total born, stillborn rate, average piglet birth weight, or piglet throughput. In summary, increasing feed allowances to meet 85 to 150% of the MEm requirements during early gestation on terminal line sows resulted in increased weight and caliper change without impact in performance. Body weight seems to be more sensitive to changes in feeding levels than caliper scores up to d 30 of gestation.

153 Effects of Feeding Levels in Early Gestation on PIC Maternal Line Sows and Litter Performance

Abstract Our objective was to determine the effects of increasing feeding levels for maternal line sows during early gestation on sow and litter performance. A total of 969 PIC L02 (199.6 kg ± 1.88) parity 1 to 6 sows were randomly assigned at weaning to 1 of 4 treatments within parity category in a randomized complete block design with body weight blocks. Treatments consisted of feeding sows with daily feed allowances to meet 100, 125, 150, or 175% of the NRC (2012) maintenance metabolizable energy (MEm) requirement calculated as MEm, kcal/d = 100×(body weight, kg)0.75. A common corn-soybean meal-wheat-based diet with 3,056 kcal of ME/kg and 0.60% standardized ileal digestible lysine was used. Treatments were applied from d 5 to 30 of gestation, after which they were fed according to body condition until moved to the farrowing room. Sow was the experimental unit and data were analyzed using generalized linear mixed models with the lmer and glmer functions of R. Average caliper score at weaning was 12.2 across treatments and average feed allowances were 1.8, 2.3, 2.7, and 3.2 kg/d for the 100, 125, 150, and 175 treatments, respectively. Increasing feed allowances increased (linear, P < 0.05) weight change (3.0, 6.5, 8.5 and 10.5 kg, respectively) and caliper score change (1.0, 1.2, 1.4, 1.5 units, respectively) from weaning to d 30 of gestation. There was no evidence for treatment effects on farrowing rate, caliper score at farrowing, total born, stillborn rate, average piglet birth weight, or piglet throughput. In summary, increasing feed allowances to meet 100 to 175% of the MEm requirements during early gestation on maternal line sows resulted in increased weight and caliper change without impact in performance. Body weight seems to be more sensitive to changes in feeding levels than caliper scores up to d 30 of gestation.

PSV-6 Effects of Boron Supplementation on Apparent Digestibility and Retention of Nutrients in Growing Pigs

Abstract An experiment was conducted to evaluate the effects of boron (B) supplemented to a corn-soybean meal diet on apparent digestibility and retention of nutrients in growing barrows. A total of 24 barrows (mean initial BW = 61.15 ± 2.45 kg) were allotted to 3 dietary treatments with 8 replicates. Dietary treatments consisted of 0, 5, and 25 mg B/kg diet as sodium tetraborate decahydrate (Na2 B4 O7∙10 H2O; 11.34% B) which were fed from weaning onward. Barrows underwent a 5-7 d adaptation period to the meal allowance and metabolism crate which was followed by a 5-d total fecal and urine collection using the marker to marker method. Barrows were fed at 2.7% of their metabolic BW (2.7 x maintenance ME needs [2.7 × 106 Kcal ME/kg BW0.75]) during the adaptation and collection periods in a gruel form (feed:water, 1:1 wt/vol). Data were analyzed using the Proc GLM procedure of SAS with the individual pig as the experimental unit. Supplemental B did not affect (P > 0.05) energy, lipid, nitrogen, calcium, or phosphorus apparent digestibility and retention. However, there was a linear increase observed in both magnesium absorption (P = 0.01; 0.24, 0.26, and 0.32 g/d, respectively) and digestibility (P = 0.04; 22.35, 23.56, and 28.49 %, respectively) to increasing B supplementation. Absolute retention of magnesium did not differ (P > 0.05; 0.13, 0.14, and 0.17 g/d, respectively). In conclusion, supplementing B at 5 and 25 mg B/kg diet resulted in an increase in magnesium absorption and digestibility with no adverse effects observed on apparent digestibility and retention of other nutrients.

Effects of heat stress on

Context Interest in studying heat stress (HS) has increased significantly due to the problems associated with increasing global warming. Heat stress has very destructive effects on the health and performance of livestock. Aims Our objective was to investigate the effects of heat stress on in vivo and in vitro ruminal metabolism in fat-tailed Iranian sheep. Methods Fourteen intact non-lactating and non-pregnant mature fat-tailed Makoei ewes (67.5 ± 2.5 kg BW) were kept indoors for 24 h/day and randomly assigned to HS (33.0–41.0°C and a temperature–humidity index (THI) of ≥83 for 24 h/day) or thermoneutral (TN; 24.5 ± 2.3°C and a THI of 66.1 ± 2.5) condition in two consecutive experimental periods. At the end of first experimental period, the animals in each group were exchanged with another group. The ewes were fed a total mixed ration two times a day, composed of lucerne hay (33%) and corn silage (1:2) to meet their maintenance metabolisable energy and protein requirements. Key results HS ewes had lower dry-matter (DM) intake than did TN ewes (P < 0.05). HS increased the in vivo DM, organic matter (OM) and neutral detergent fiber digestibility (P < 0.05), but crude protein digestibility was not affected. Total volatile fatty acid concentration and pH were not affected by HS. However, propionate molar percentage was increased and N-NH3 concentration was decreased by HS. In vitro gas production of three different tested feeds was lower in rumen fluid collected from HS than that from TN group, but DM and OM digestibility and methane emission were decreased only in the case of Orchard grass (P < 0.05). Conclusions and implications In general, HS had detrimental effects on DM intake and in vitro nutrient digestibility but increased in vivo nutrient digestibility, and changed microbial population.

Architecture of broiler breeder energy partitioning models

A robust model that estimates the ME intake over broiler breeder lifetime is essential for formulating diets with optimum nutrient levels. The experiment was conducted as a randomized controlled trial with 40 Ross 708 broiler breeder pullets reared on 1 of 10 target growth trajectories, which were designed with 2 levels of cumulative BW gain in prepubertal growth phase and 5 levels of timing of growth around puberty. This study investigated the effect of growth pattern on energy efficiency of birds and tested the effects of dividing data into daily, 4-d, weekly, 2-wk, and 3-wk periods and the inclusion of random terms associated with individual maintenance ME and ADG requirements, and age on ME partitioning model fit and predictive performance. Model [I] was: MEId = a × BWb + c × ADGp + d × ADGn + e × EM + ε, where MEId was daily ME intake (kcal/d); BW in kg; ADGp was positive ADG; ADGn was negative ADG (g/d); EM was egg mass (g/d); ε was the model residual. Models [II to IV] were nonlinear mixed models based on the model [I] with inclusion of a random term for individual maintenance requirement, age, and ADG, respectively. Model [II] – 3 wk was chosen as the most parsimonious based on lower autocorrelation bias, closer fit of the estimates to the actual data (lower model MSE and closer R2 to 1), and greater predictive performance among the models. Estimated ME partitioned to maintenance in model [II] – 3 wk was 100.47 ± 7.43 kcal/kg0.56, and the ME requirement for ADGp, ADGn, and EM were 3.49 ± 0.37; 3.16 ± 3.91; and 2.96 ± 0.13 kcal/g, respectively. Standard treatment had lower residual heat production (RHP; -0.68 kcal/kg BW0.56) than high early growth treatment (0.79 kcal/kg BW0.56), indicating greater efficiency in utilizing the ME consumed. Including random term associated with individual maintenance ME in a 3-wk chunk size provided a robust, biologically sound life-time energy partitioning model for breeders.

Derivation of the maintenance energy requirements and efficiency of metabolizable energy utilization for dry and lactating Jersey cows

Maintenance energy is the energy required to conserve the state of an animal when no work is completed. Dietary energy must be supplied to meet maintenance requirements before milk can be produced. The objectives of the current experiment were to quantify the maintenance energy requirement of Jersey cows when lactating or dry. Energetic measures were collected on 8 Jersey cows and evaluated across 3 physiological phases and nutritional planes: lactation, dry cows fed at maintenance, and fasted dry cows. Through total collection of feces and urine as well as using headbox-style indirect calorimeters, energy balance and heat production data were measured across all phases. Lactation data were collected across four 28-d periods. Data for cows fed at maintenance were collected after 14 d and fasting heat production was measured during the last 24 h of a 96-h fast. Net energy for maintenance (NEM) requirements, and the efficiency of converting metabolizable energy (ME) into net energy were compared between lactating and dry (maintenance or fasting phase) cows. Heat production of dry cows fed at maintenance, which represents ME for maintenance, was 0.146 ± 0.0087 Mcal per unit of metabolic body weight (BW0.75, MBW). Fasting heat production, which represents NEM, was 0.102 ± 0.0071 Mcal/MBW. Energy balance was calculated as tissue energy plus milk energy. When estimated via regressing energy balance on ME intake, NEM was not different between dry and lactating cows (0.120 ± 0.32 vs. 0.103 ± 0.0052 Mcal/MBW). However, the slope of the regression of energy balance on ME intake was greater for dry compared with lactating cows (0.714 ± 0.046 vs. 0.685 ± 0.010) when evaluated with a fixed intercept. This suggests that dry cows were more efficient at converting ME into net energy and that the efficiency of utilizing ME for maintenance may be greater than for lactation. Our measurements of NEM and the slope of ME on energy balance were greater than the value used by the National Research Council (2001), which are 0.080 Mcal/MBW for NEM and approximately 0.64 for the slope. Results of this study suggest that NEM and the efficiency of converting ME into NEM of modern lactating Jersey cows are similar to recent measurements on modern Holstein cows and greater than previous measurements.

PSIV-10 The Effect of a Dacitic (rhyolitic) Tuff Breccia, a Hydrated Sodium Calcium Aluminosilicate (HSCAS), Inclusion in Corn-soybean Meal Diets on Growth Performance of Individually Housed Grower Pigs

Abstract Crossbred pigs (24 barrows and 24 gilts; BW 35.59±0.24 kg) were blocked by body weight, sex, and allotted in a randomized complete block design to 3 dietary treatments: 1) Control [CON], 2) CON+0.25%, and 3) CON+0.50% inclusion of a dacitic tuff breccia (DTB) to evaluate effects on growth performance. Diets were formulated to meet or exceed NRC (2012) requirement estimates and fed for 2 phases (d0-14=PHS_1 and d14-28=PHS_2). Diets were limit fed based on metabolic body weight (3.5 x maintenance ME needs [3.5 × 106 Kcal ME/kg BW0.75]). Pigs were weighed weekly and feed allowance adjusted accordingly. In PHS_1, a tendency for a sex difference, gilt vs. barrow, respectively, for ADG (4.92%; 0.913 vs. 0.870 kg; P=0.10) and G:F (4.14%; 0.528 vs. 0.507; P=0.06) existed. The responses to treatments 1–3, respectively, for ADG (0.877, 0.900, and 0.896 kg; linear P=0.54) and G:F (0.510, 0.522, 0.521; linear P=0.46) were numerically greater. In PHS_2, sex differences, gilt vs. barrow, respectively, for ADG (5.67%; 0.946 vs. 0.895 kg; P=0.05) and G:F (7.98%; 0.460 vs. 0.426; P< 0.01) existed. The numerical responses to treatments 1–3, respectively, for ADG (0.912, 0.944 and 0.905 kg; P=0.41) and G:F (0.439, 0.446, 0.444; linear P=0.70) continued. A tendency for a quadratic response in ADFI (P=0.06) existed because feed allowance increased with increasing weekly BW for treatments 2 and 3. Overall, sex differences, gilt vs. barrow, respectively, for ADG (5.30%; 0.929 vs. 0.882 kg; P< 0.05) and G:F (6.23%; 0.491 vs. 0.462; P< 0.01) occurred. Numerical responses to treatments 1–3, respectively, for ADG (0.895, 0.921 and 0.900 kg, P=0.32) and G:F (0.471, 0.480, 0.479; linear P=0.50) occurred. Additionally, the response to DTB appeared to be higher in barrows.

Phytol supplementation alters plasma concentrations of formate, amino acids, and lipid metabolites in sheep

The phytol moiety in chlorophyll molecules acts as an agonist of peroxisome proliferator-activated receptor-α in monogastric animals. The current study aimed to clarify the effects of dietary supplementation with phytol on the plasma concentrations of formate and amino acids related to one-carbon (1C) donors and its effects on lipid metabolism in sheep. Four mature sheep were fed with a mixed ration (metabolizable energy, 10.7 MJ/kg DM; CP, 150 g/kg DM) comprising barley, rice bran, soybean meal, and oat hay at 1.5 times maintenance metabolizable energy for three consecutive 14-day experimental periods. The first and third periods served as controls without phytol supplementation, while in the second period, phytol was added to the mixed ration at 12 g/kg of dietary DM per day. In each period, feces, urine, and jugular blood samples were collected. Dry matter intake in relation to metabolic BW was slightly lower (P < 0.01) in the first period than the second and third periods but did not differ between the latter two periods. Dry matter digestibility was slightly reduced (P = 0.05) by the phytol treatment. Nitrogen (N) intake and retention showed similar trends to DM intake, but urinary N was unchanged among the periods. Plasma cholesterol and phospholipid concentrations decreased during the phytol treatment period, while triglyceride concentration increased (P < 0.05). In the phytol treatment period, the plasma concentrations of serine and glycine (1C donors) increased, but the glutamate level decreased (P < 0.01). Plasma concentrations of formate and methionine increased (P < 0.01) from the first control period to the phytol supplementation period, but homocysteine and cysteine (intermediate and by-product of the methionine cycle) levels were unchanged among the treatment periods. In conclusion, dietary phytol affects lipid metabolism as well as amino acid metabolism and 1C donors in sheep. These effects may be associated with the activity of phytol as an agonist of the nuclear receptors, although this needs further investigation.

222 Partitioning of retained energy between protein and fat gain, and heat of product formation and support metabolism in growing beef cattle

Abstract Multiple linear regression inaccurately computes the efficiency of energy use for protein and fat gain. The objective was to quantify efficiency of metabolizable energy use for protein and fat gain along with heats of product formation and support metabolism. A literature search was performed to compile data (31 studies, 214 treatment means) on metabolizable energy intake (MEI) and composition of empty body gain in growing steers and heifers. Data analyses were performed using R statistical package for mixed models with study as random variable. Linear regression of MEI on energy gain (EG; P &amp;lt; 0.001; R2 = 0.627) resulted in an estimate of metabolizable energy for maintenance (MEm) of 156 kcal/kg.75 and efficiency of ME use for gain of 0.518. Linear regression of MEI on EG as protein and fat (P &amp;lt; 0.001; R2 = 0.623) resulted in an estimate of MEm of 149 kcal/kg.75, and efficiency of protein (kp) and fat (kf) gain of 0.274 and 0.585, respectively, resulting in an overall efficiency of EG of 0.520. Nonlinear regression model (EG = kg*(MEI-MEm)) resulted in an estimate of MEm of 103 kcal/kg.75 and efficiency of EG of 0.342. The heat of product formation was assumed to be 0.48 (1 – 0.52) and the heat of support metabolism (HiEv) 0.18 (0.52 – 0.34). Multivariate regression was used to fit simultaneous models for EG as protein (EGp = (kp+HiEvp)*k*MEA) and fat (EGf = (kf+(0.18-HiEvp))*(1-k)*MEA). Estimates (P &amp;lt; 0.001) of kp and kf were 0.12 ± 0.01 and 0.63 ± 0.02, and HiEvp and proportion of ME available for protein gain (k) were 0.11 ± 0.01 and 0.75 ± 0.01, respectively. The heat of product formation and support metabolism for protein were 0.77 and 0.11, and fat were 0.30 and 0.07, respectively. In conclusion, efficiency of ME use for protein was lesser than for fat gain, and heat of support metabolism was greater for protein than fat gain.

279 Evaluation of the NRC (2012) model in estimating standard maintenance metabolizable energy requirement of PIC sows during mid-gestation

Abstract The objective was to evaluate the NRC (2012) model in predicting standard maintenance metabolizable energy (MEm) of PIC sows during mid-gestation. A total of 201 PIC Camborough sows (parity 1 to 10) were randomly assigned to 1 of 4 treatments in a complete randomized design between day 36 and 46 post-breeding. Treatments consisted of feeding sows with daily feed allowances to meet 80, 90, 100 or 110% of MEm calculated as MEm, kcal/day = 100 × (body weight)0.75. A common corn-soybean meal-based diet with 3,302 kcal of ME/kg and 0.61% standardized ileal digestible lysine was fed for 28 days. Sow body weight (BW) and sow body condition caliper score (CS) were captured at day 0, 14 and 28. Data were analyzed with PROC GLM of SAS with sow as experimental unit. Average sow parity and feed allowance were 4.2 and 1.79 kg/day, respectively. Average sow BW and sow CS at day 0, 14 and 28 were 234, 233 and 242 kg and 14.9, 14.9 and 14.8, respectively. Increasing feed allowances to meet 80 to 110% of MEm requirement increased (linear, P&amp;lt; 0.01) average daily gain (ADG; 0.100, 0.259, 0.417 and 0.440 kg/d, respectively). The estimated regression equation was ADG, kg/day = -0.83 + 1.193 × MEm, estimating the MEm to maintain BW was below 80% of NRC (2012) estimate. Caliper score change (CSC) increased (linear, P&amp;lt; 0.01) with increasing feed allowances to meet 80 to 110% of MEm requirement (-0.78, -0.26, 0.13, and 0.35, respectively). The estimated regression equation was CSC = -3.73 + 3.78 × MEm, estimating the MEm to maintain CS at 98.7% of NRC (2012) estimate. In summary, results showed that the MEm to maintain BW and CS for PIC sows during mid-gestation was below 80% and at 98.7%, respectively, of NRC (2012) estimated requirement.

ENERGY BALANCE UNDER RESTRICTED FEEDING IN RUMINANTS

Forty-eight adult local desert non-pregnant and non-lactating females, age 4-5 yrs.; Barki sheep (n= 16 and average body weight 34.53 ±1.56 kg), Balady goats (n= 16 and average body weight 31.11 ± 1.63 kg), and Shami goats (n=16 and average body weight 28.08±0.92 kg) were used to study effects of long-term restricted feeding regime on body weight changes and balance of energy and protein. Animals of each species were allocated to two levels of feed intake; control feeding treatment (CON) where animals fed a diet at a level of feeding to meet approximately the metabolizable energy for maintenance requirement (MEm), while those on the other dietary treatment was fed almost 50% of these quantities on a BW basis, termed as the restricted treatment (restricted; RES). Alfalfa hay and concentrate feed mixture (50:50% as DM basis) were given based on requirement recommendations. The results could be summarized as follows: 1-Comparison between Balady goats (BG) and Sheep (SH): The ADG was not affected (P<0.05) by animal species (BG vs. SH), however, it was affected (P<0.01) by feed intake level where the RES animal group showed a negative ADG (-65.6 g/d) compared with the CON group that achieved positive ADG (36.4 g/d). Both of SH and BG had similar negative energy balance (EB) values (67.0 vs. 61.4 KJ/ kg0.75/d, for BG and SH respectively). Nitrogen balance (NB) was greater (P<0.01) for SH (107.64 mg/kg0.75/d ) vs. BG (89.47 mg/kg0.75/d) and was greater (P<0.01) for animals fed on CON intake (251.47 vs. 208.55 mg/kg0.75/d, respectively) than those fed on RES intake (-36.18 vs. -29.62 mg/kg0.75/d, respectively), which gave a negative NB. 2.Comparison between Balady goats (BG)and Shami goats (SG): The ADG was not affected (P< 0.05) by animal species (BG vs. SG) being corresponding values 45.1 and 40.6 g/d respectively. However, ADG was affected (P< 0.001) by feed intake level where the RES animal group showed a negative ADG (-55.6 g/d) compared with the CON group that achieved positive ADG (30.1 g/d). Under CON intake, EB was an insignificant decrease in SG compared to BG. However, under RES intake both BG and SG had a negative energy balance (kJ/kg0.75/day) and it was lower (P<0.01) in SG than that in BG. Animals fed on the CON intake level had a greater (P<0.01) value for EB compared to those fed on RES intake and the latter gave a negative balance. Nitrogen balance (NB, mg/kg0.75/day) was a trend to be greater (P<0.10) for SG vs. BG. Also, animals under the CON intake level captured more nitrogen than their counterparts, which lost a large amount of nitrogen. Also, the retention N was increased (P<0.01) in SG than BG under the CON intake level, however, all breeds were lost N under the RES intake level especially in SG (-76.37) followed by BG (-29.62). It could be concluded that with hot conditions, sheep may have an advantage in a decreased Metabolizable energy for maintenance (MEm) requirement and reduction in heat production of a magnitude adequate to maintain body weight. There is a similar rate of using the energy between sheep and goats with moderate or limited nutrition planes. It is clear that Balady goats are better than Shami goats in their ability to reduce the energy expenditure via reducing the rate of metabolism when they were fed on restricted intake.

Feeding behavior, water intake, and energy and protein requirements of young Nellore bulls with different residual feed intakes.

This study aimed to determine feeding behavior, water intake (WI), and energy requirements of high- and low-residual feed intake (RFI) Nellore bulls. Data were collected from 42 weaned Nellore bulls (initial body weight [BW] 260 ± 8.1 kg; age 7 ± 1.0 mo) housed in a feedlot in group pens that contained electronic feeders, waterers, and a scale connected to the waterers. The individual dry matter intake (DMI), WI, and BW were recorded daily. The indexes of average daily gain (ADG), feed efficiency (gain to feed ratio), and RFI were calculated based on the data collected. The number of feeder and waterer visits and the time spent feeding or drinking water per animal per day were recorded as feeding behavior measures. Energy requirements for maintenance and gain were calculated according to the BR-CORTE system. Low-RFI bulls had lower DMI (P < 0.01) than high-RFI bulls, and no differences (P > 0.05) were observed between the two groups regarding WI, performance, and feeding behavior measurements. The net energy requirements for maintenance, metabolizable energy for maintenance, and efficiency of metabolizable energy utilization were 63.4, 98.6 kcal/metabolic empty body weight (EBW)0.75 daily, and 64.3%, respectively, for low-RFI bulls, and 78.1, 123.9 kcal/EBW0.75 daily, and 63.0%, respectively, for high-RFI bulls. The equations obtained for net energy for gain (NEg) were: NEg (Mcal/EBW0.75) daily = 0.0528 × EBW0.75 × EBG0.5459 for low-RFI and 0.054 × EBW0.75 × EBG0.8618 for high-RFI bulls, where EBG is the empty body gain. We did not observe any difference (P > 0.05) regarding the composition of gain in terms of protein or fat deposition between the two groups. Both groups also presented similar (P > 0.05) carcass and non-carcass traits. Therefore, our study shows that low-RFI Nellore bulls eat less, grow at a similar rate, and have lower maintenance energy requirements than high-RFI bulls. We also suggest that the lower feed intake did not compromise the carcass traits of more efficient animals, which would reduce production costs and increase the competitiveness of the Brazilian beef sector on the world market.

Energy requirements for maintenance and growth of young pre-ruminant Angora goats

Abstract There is little information available on the nutrient requirements of suckling Angora kids weighing less than 10 kg which has resulted in nutrition recommendations being based on older, heavier and weaned goats. This experiment determined the energy intake of suckling Angora kids to estimate maintenance ME requirement (MEm) and ME required for growth (MEg) for 8 and 21 day old kids. Does were housed in individual pens in an outdoor feedlot from day 47 of pregnancy. Pregnant does experienced a range of controlled nutrition treatments providing a range in live weight and body condition at kidding. From 4 days postpartum treatments were: ad libitum (AL) to allow maximum ME intake resulting in doe live weight gain; or Restricted (R) to 70% of AL, resulting in doe live weight loss until week 10 of lactation. Doe milk production was determined at days 8 and 21 of lactation, and ME intake of milk, kid liveweight change and fibre growth rate were determined. ME intake (kJ/kg0.75day) was then related to daily liveweight gain (g/kg0.75day) using multiple linear regression analysis. At 8 days of age, MEm = 1199 kJ/kg0.75day and MEg = 35.6 kJ/kg0.75day (P = 0.002). At 21 days of age, MEm = 700 kJ/kg0.75day (NS) and MEg = 24.0 kJ/kg0.75day (P

Energy and protein requirements of Holstein × Gyr crossbred heifers

Nutrient requirements in cattle are dependent on physiological stage, breed and environmental conditions. In Holstein × Gyr crossbred dairy heifers, the lack of data remains a limiting factor for estimating energy and protein requirements. Thus, we aimed to estimate the energy and protein requirements of Holstein × Gyr crossbred heifers raised under tropical conditions. Twenty-two crossbred (½ Holstein × ½ Gyr) heifers with an average initial BW of 102.2 ± 3.4 kg and 3 to 4 months of age were used. To estimate requirements, the comparative slaughter technique was used: four animals were assigned to the reference group, slaughtered at the beginning of the experiment to estimate the initial empty BW (EBW) and composition of the animals that remained in the experiment. The remaining animals were randomized into three treatments based on targeted rates of BW gain: high (1.0 kg/day), low (0.5 kg/day) and close to maintenance (0.1 kg/day). At the end of the experiment, all animals were slaughtered to determine EBW, empty body gain (EBG) and body energy and protein contents. The linear regression parameters were estimated using PROC MIXED of SAS (version 9.4). Estimates of the parameters of non-linear regressions were adjusted through PROC NLIN of SAS using the Gauss–Newton method for parameter fit. The net requirements of energy for maintenance (NEm) and metabolizable energy for maintenance (MEm) were 0.303 and 0.469 MJ/EBW0.75 per day, respectively. The efficiency of use of MEm was 64.5%. The estimated equation to predict the net energy requirement for gain (NEg) was: NEg (MJ/day) = 0.299 × EBW0.75 × EBG0.601. The efficiency of use of ME for gain (kg) was 30.7%. The requirement of metabolizable protein for maintenance was 3.52 g/EBW0.75 per day. The equation to predict net protein requirement for gain (NPg) was: NPg (g/day) = 243.65 × EBW−0.091 × EBG. The efficiency of use of metabolizable protein for gain (k) was 50.8%. We observed noteworthy differences when comparing to ME and protein requirements of Holstein × Gyr crossbred heifers with other systems. In addition, we also observed differences in estimates for NEm, NEg, NPg, kg and k. Therefore, we propose that the equations generated in the present study should be used to estimate energy and protein requirements for Holstein × Gyr crossbred dairy heifers raised in tropical conditions in the post-weaning phase up to 185 kg of BW.