Modelling energy utilisation in broiler breeder hens

1. The objective of this study was to determine a metabolisable energy (ME) requirement model for broiler breeder hens. The influence of temperature on ME requirements for maintenance was determined in experiments conducted in three environmental rooms with temperatures kept constant at 13, 21 and 30 degrees C using a comparative slaughter technique. The energy requirements for weight gain were determined based upon body energy content and efficiency of energy utilisation for weight gain. The energy requirements for egg production were determined on the basis of egg energy content and efficiency of energy deposition in the eggs. 2. The following model was developed using these results: ME = kgW0.75(806.53-26.45T + 0.50T2) + 31.90G + 10.04EM, where kgW0.75 is body weight (kg) raised to the power 0.75, T is temperature ( degrees C), G is weight gain (g) and EM is egg mass (g). 3. A feeding trial was conducted using 400 Hubbard Hi-Yield broiler breeder hens and 40 Peterson males from 31 to 46 weeks of age in order to compare use of the model with a recommended feeding programme for this strain of bird. The application of the model in breeder hens provided good productive and reproductive performance and better results in feed and energy conversion than in hens fed according to strain recommendation. In conclusion, the model evaluated predicted an ME intake which matched breeder hens' requirements.     

Energy metabolism of groups of broiler breeders in open-circuit respiration chambers

Energy metabolism of broiler breeders housed in groups was measured in large open-circuit respiration chambers. The design, function and calibration of the chambers are described. Each of the three chambers has a capacity for 24 pullets or adult layers, or 16 adult broiler breeders. Control of ventilation rate is by calibrated choked-flow nozzles. Before experiments were started the system was assessed by CO2 infusion and recovery and ethanol combustion studies. Percentage CO2 recoveries were greater than 98 of infused and the mean (+/- SD) quotient of CO2 produced to O2 consumed from the combusion of ethanol was 0.67 (+/- 0.02). Forty-eight broiler breeder hens in lay were placed in the respiration chambers (16 per chamber) and fed at different rates from around maintenance to about twice this value. The energy required for maintenance (MEm) was 365 kJ/kgW0.75 d and the efficiency of utilisation of metabolisable energy (ME) for production (kp) was 0.70. Starvation heat production was about 350 kJ/kgW0.75 d and was shown to affect the derived values of the energetic parameters when included in the relationship between retained energy and metabolisable energy intake. Published results were recalculated and found to support this.     

Effects of diet type and metabolizable energy intake on tympanic temperature of steers fed during summer and winter seasons

A summer study and a winter study were conducted using an incomplete factorial structure in a complete randomized design. Within season, the factors studied were 1) type of diet, which included 2 levels of ME, classified as either concentrate (3.04 Mcal of ME/kg) or roughage (2.63 Mcal of ME/kg) diets, and 2) daily ME intakes (MEI) of 11, 18, and 25 Mcal of ME/d for the roughage diets and 18, 25, and 32 Mcal of ME/d for the concentrate diets. In Exp. 1 (summer study), 30 steers (5 steers/treatment combination) were used to collect tympanic temperatures (TT). In Exp. 2 (winter study), 24 steers (4 steers/treatment combination) were used to collect TT. Mean TT was 0.3°C greater for summer than winter (38.9 vs. 38.6°C, respectively; P < 0.05). Steers fed diets based on concentrate tended to display greater TT than steers fed diets based on roughage. Season × diet × hour interactions were found for TT (P = 0.01). In the winter, greater TT (P < 0.05) were found from 0900 to 1400 h when an equal amount of MEI was derived from a concentrate-based vs. roughage-based diet. In cattle fed roughage-based diets during the summer, TT = 38.63 + 0.0114?MEI, whereas for cattle fed concentrate-based diets, TT = 38.69 + 0.0114?MEI. During the winter, for cattle fed a roughage-based diet, TT = 37.65 + 0.0856?MEI - 0.0018?MEI(2), whereas for cattle fed a concentrate-based diet, TT = 35.37 + 0.2635?MEI - 0.0051?MEI(2). In summary, results demonstrate that increases in the energy of the diet resulted in increases in TT. However, the response was dependent on season of the year, with a linear response in TT for summer and a quadratic response during winter.     

Influence of energy intake on growth and utilisation of dietary protein and energy in germ-free and conventional chicks

The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. In experiment 1 a high energy diet (HED, 14.8 kJ ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.     

Relationship of rumen fluid dilution rate to rumen fermentation and dietary characteristics of beef steers

Data from seven beef steer trials were compiled and regression analyses used to evaluate relationships among molar proportions of acetate (Ac), propionate (Pr) and butyrate (Bu), total concentration of volatile fatty acids (VFA), rumen ammonia (NH3), rumen pH, rumen fluid dilution rate (FDR), rumen fluid volume (FVOL), body weight (WT), dry matter intake (DMI) and dietary concentration and intake of crude protein (CP and CPI), acid detergent fiber (ADF and ADFI), ash (ASH and ASHI) and metabolizable energy (ME and MEI). Of the six fermentation variables, Pr (negative regression coefficient, beta) and pH (positive beta) were related (P less than .05) to FDR, but only 3 and 12% of the variation in these two variables, respectively, was explained by FDR. When FDR was described by dietary characteristics, ASHI was positively related to FDR (R2 = .16). The best two-variable model for FDR contained DMI (positive beta) and WT (negative beta) and increased R2 to .36. Fluid volume was best described by ME (positive beta; R2 = .20). The two-variable model for FVOL added ASH with a positive partial beta (R2 = .23). When fermentation variables were regressed on dietary characteristics, Ac was best described by ADF (positive beta; R2 = .71). The variable that best described Pr proportion was ADF (negative beta; R2 = .50), and addition of CP (negative beta) and MEI (positive beta) into the Pr model improved R2 to .70. Molar proportion of butyrate was related to CP (positive beta; R2 = .23), and addition of ME (positive beta) to the model improved the R2 to .31. Total VFA concentration was best described by ADFI (positive beta; R2 = .14). An R2 of .29 resulted when ME (positive beta) and CPI (negative beta) were included in the total VFA model. Rumen pH was related to ADF (positive beta; R2 = .45), and addition of CP (positive beta) to the rumen pH model increased R2 to .55. Crude protein concentration was related to ruminal NH3 level (positive beta; R2 = .42), and inclusion of ADFI (positive beta) into the model improved the R2 to .47.     

Influence of level of feed input and procedure on metabolisable energy and endogenous energy loss (EEL) with adult cockerels

1. Two experiments were performed to study the relationship between apparent metabolisable energy (AME) and true metabolisable energy (TME) values at different feed intakes. Rhode Island Red (RIR) adult cockerels were used in two bioassays, under standard conditions. 2. In the first experiment (precision feeding) the birds were not fed for 24 h and then various quantities of maize were fed. There were 6 replicates per treatment. Droppings voided during the 48 h of the experimental period were collected and assayed for gross energy and nitrogen. 3. In the second experiment, each bird was given a 3-d adaptation period, fasted for 24 h and then given maize as an admixture (conventional addition method: CAM) to the same rations as those used in the first experiment. During the 3 d of the experimental period, droppings were collected and frozen for chemical analysis. 4. The results showed that mean metabolisable energy (ME) values obtained by the precisionfeeding procedure were higher than those obtained by CAM. The endogenous energy loss (EEL) (FE m + UE e ) determined by precision feeding was lower than that given by CAM. 5. It was concluded that the method of feeding does not influence ME of maize at different feed inputs. However, differences among intercepts of the regression between ME and feed input suggest that EEL varies at different maize inputs. 6. The optimum maize quantity was approximately 35 to 40 g for adult RIR cockerels by both procedures.     

不同品种小麦生长猪消化能与代谢能预测模型的建立

本试验旨在研究不同品种小麦的理化特性及对生长猪的消化能和代谢能值,并探讨通过理化特性建立消化能与代谢能预测模型的可行性。试验选取12头初始体重相近(50.1±2.8)kg的杜×长×大三元杂交去势公猪,随机分成2组,每组6头猪,采用2个6×6拉丁方设计,试验共6期。采用直接法评定12个小麦样品的能量价值,每个小麦样品配制1种日粮,共12种日粮,小麦在日粮中所占比例为97.0%。结果表明:12个不同品种小麦的能值差异极显著(P<0.05),其中北麦4的消化能含量最低(16.40 MJ/kg DM),而龙麦30的消化能含量最高(17.01 MJ/kg DM)。北麦4的代谢能含量亦最低(15.72 MJ/kg DM),辽春10最高(16.48 MJ/kg DM)。通过回归分析,建立了以总能和理化特性为基础的小麦消化能和代谢能预测模型,推荐预测模型:DE=-829-58.4×ADF+1.1×GE(R2=0.79,RSD=24.5),DE=-1384+1.1×GE+0.65×BW(R2=0.79,RSD=24.8),ME=-2990+1.7×GE-50.2×Xylans-87.6×Ash(R2=0.88,RSD=21.1)。     

Additional data on energy requirements of young adult cats measured by indirect calorimetry

Measurements of nitrogen, carbon and energy balances were done on eight female adult cats aged approximately 1.5 years with the help of respiration chambers. The cats were fed with a marked dry food for kittens (Biomill kitten). Faeces and urine samples were collected with the help of a special cat toilet that allows the single collection of both materials. The calculated energy requirement of these eight female cats was 239.6 kJ ME/kg BW/day (R(2) = 0.98). Including the data, on 12 young male adult cats, of L?uger, (2001), an energy requirement of 238 kJ ME/kg BW/day (R(2) = 0.95) could be calculated. From these data, it can be followed that the energy requirements of young, active cats are higher than that of the older cats. The method of indirect calorimetry does not necessarily lead to lower energy requirements.     

梅花鹿季节性营养规律研究

为了研究在我国饲养模式下梅花鹿营养摄入的季节性规律,选用8只雄性成年梅花鹿,在我国传统饲养模式下,定期测定梅花鹿饲料消耗及营养物质摄入水平、鹿体重变化及营养相关血液指标变化,分析梅花鹿营养季节性规律变化。结果表明,①梅花鹿夏季干物质的采食(DMI)、代谢能摄入(MEI)和可消化蛋白质摄入(DCPI)处于一年中最高水平,分别为78~80 g/(kg0.75.d-1)、0.8 MJ/(kg0.75.d-1)和8~10 g/(kg0.75.d-1);夏季梅花鹿体重平均增加约20 kg;血清蛋白质水平较高。②梅花鹿公鹿秋季发情期干物质的DMI、MEI和DCPI为一年中最低水平,分别为41~60 g/(kg0.75.d-1)、0.36~0.56 MJ/(kg0.75.d-1)和1.14~3.0 g/(kg0.75.d-1);梅花鹿在9~10月份体重平均降低约17.5 kg,血清蛋白质水平较低,营养处于负平衡状态。③梅花鹿冬季DMI、MEI和DCPI处于一年中低谷,分别为70~75 g/(kg0.75.d-1)0、.61~0.69 MJ/(kg0.75.d-1)和3.0~3.6 g/(kg0.75.d-1),体重为一年中最低水平,平均约100 kg。④在圈养条件下梅花鹿MEI[MJ/(kg0.75.d-1)]和增重G[g/(kg0.75.d-1)]间存在显著正相关(P=0.0026),直线回归方程为G=28.482 MEI-17.78(R2=0.5771,P=0.0026,n=13),维持代谢能需要量为0.624 MJ/(kg0.75.d-1),体重每增加1 g,需要生长代谢能35.11 kJ。     

Cow/calf preweaning efficiency of Nellore and Bos taurus x Bos indicus crosses

The objectives of this study were to determine if percentage Bos taurus (0 or 50%) of the cow had an effect on ME requirements and milk production, and to compare cow/calf efficiency among 3 mating systems. Metabolizable energy requirements were estimated during a feeding trial that encompassed a gestation and lactation feeding trial for each of 2 groups of cows. Cows were 0 or 50% Bos taurus (100 or 50% Nellore) breed type: Nellore cows (NL; n = 10) mated to Nellore bulls, NL cows (n = 9) mated to Angus bulls, Angus x Nellore (ANL; n = 10) and Simmental x Nellore (SNL; n = 10) cows mated to Canchim (5/8 Charolais 3/8 Zebu) bulls. Cows were individually fed a total mixed diet that contained 11.3% CP and 2.23 Mcal of ME/kg of DM. At 14-d intervals, cows and calves were weighed and the amount of DM was adjusted to keep shrunk BW and BCS of cows constant. Beginning at 38 d of age, corn silage was available to calves ad libitum. Milk production at 42, 98, 126, and 180 d postpartum was measured using the weigh-suckle-weigh technique. At 190 d of age, calves were slaughtered and body composition estimated using 9-10-11th-rib section to obtain energy deposition. Regression of BW change on daily ME intake (MEI) was used to estimate MEI at zero BW change. Increase in percentage Bos taurus had a significant effect on daily ME requirements (Mcal/d) during pregnancy (P < 0.01) and lactation (P < 0.01). Percentage Bos taurus had a positive linear effect on maintenance requirements of pregnant (P = 0.07) and lactating (P < 0.01) cows; during pregnancy, the ME requirements were 91 and 86% of those in lactation (131 +/- 3.5 vs. 145 +/- 3.4 Mcal x kg(-0.75) x d(-1)) for the 0 and 50% B. taurus groups, respectively. The 50% B. taurus cows, ANL and SNL, suckling crossbred calves had greater total MEI (4,319 +/- 61 Mcal; P < 0.01) than 0% B. taurus cows suckling NL (3,484 +/- 86 Mcal) or ANL calves (3,600 +/- 91 Mcal). The 0% B. taurus cows suckling ANL calves were more efficient (45.3 +/- 1.6 g/Mcal; P = 0.03) than straightbred NL (35.1 +/- 1.5 g/Mcal) and ANL or SNL pairs (41.0 +/- 1.0 g/Mcal). Under the conditions of this study, crossbreeding improved cow/ calf efficiency and showed an advantage for cows that have lower energy requirements.     

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.     

Quantitative review of the effects of environmental temperature on food intake, egg output and energy balance in laying pullets

1. Data from 30 published experiments have been analysed to examine the relationships between environmental temperature and the long-term, adapted responses of laying pullets, measured as metabolisable energy intake, egg output and body weight change. Heat production was also estimated indirectly from the other three variables. 2. The majority of experiments employed White Leghorns, but there were 8 large trials in which brown crossbred pullets had been compared directly with White Leghorns. These trials were used to estimate differences in energy intake and heat output between brown and white birds. 3. A total of over 26,000 birds was involved in the analysis. Individual trials varied in scale from 9 birds to 2,280 birds per treatment and in duration from 8 to 61 weeks. The constant temperatures investigated ranged from 10 degrees C to 34 degrees C, but there were no data for brown pullets beyond 30 degrees C. 4. The relationship between temperature and metabolisable energy intake is curvilinear, with food intake declining more steeply as ambient temperature approaches body temperature. Adapted heat production per bird is also a curvilinear function of temperature, tending towards a value of zero when extrapolated to the point at which ambient temperature equals normal body temperature. However no satisfactory data are available for fully adapted responses in the range 34 to 42 degrees C because egg production declines continuously when these temperatures are maintained for long periods. 5. When energy intake and heat output are expressed as functions of metabolic body size (kg 0.75) they can be represented as linear functions of temperature within the range 15 to 30 degrees C, but the slope must change outside this range. 6. It is calculated that the energy available for production is at a maximum at 23 degrees C for brown birds and at 24 degrees C for White Leghorns. Gross energetic efficiency is at a maximum at 30 degrees C, but egg output is reduced at this temperature. The optimum operating temperature for laying houses will depend upon the local cost of modifying ambient temperature and on the cost of supplying diets of appropriate protein content.     

Metabolizable energy value of meat and bone meal for pigs

Metabolizable energy and N-corrected ME (MEn) values of 12 samples of meat and bone meal (MBM) were determined using 288 barrows with an average BW of 35 +/- 3.1 kg. For each of 12 MBM samples, diets were formulated by substituting 0, 50, or 100 g/kg MBM (as-fed basis) in a basal 170 g of CP/kg corn-soybean meal diet; corn and soybean meal were adjusted at the same ratio to account for the substitution. Each diet was fed to eight barrows in individual metabolism crates in metabolism studies that used a 5-d acclimation, which was followed by a 5-d period of total, but separate, collection of feces and urine. The GE, CP, crude fat (CF), ash, Ca, and P contents of the MBM samples, per kilogram (DM basis), ranged from 3,493 to 4,732 kcal, 496.7 to 619.1 g, 91.1 to 151.2 g, 200.3 to 381.9 g, 54.3 to 145.8 g, and 25.6 to 61.7 g, respectively. For each of the 12 MBM samples, MBM intake and MBM contribution to ME and MEn increased linearly (P < 0.05) with increasing level of MBM in the diets. The ME and MEn content of each of the MBM samples was calculated from the slope of the regression of MBM contribution (in kilocalories) to ME and MEn intake, respectively, against quantity (in kilograms) of MBM intake. The ME and MEn of the 12 MBM samples ranged from 1,569 to 3,308 kcal/kg DM and 1,474 to 3,361 kcal/kg DM, respectively. The variation in ME was described by the regression equation: ME = 6,982 + 0.283 GE (kcal/kg) - 6.26 CP (g/kg) - 3.75 CF (g/kg) + 129.47 P (g/kg) - 54.91 Ca (g/kg) - 6.57 ash (g/kg), with an R2 of 0.612 and SD of 376. For MEn, the corresponding equation was: MEn = 3,937 + 1.089 GE (kcal/kg) - 8.74 CP (g/kg) + 3.58 CF (g/kg) + 60.89 P (g/kg) - 15.92 Ca (g/kg) - 9.57 ash (g/kg), with an R2 of 0.811 and SD of 314. Simpler regression equations describing variation in ME or MEn were 9,254 - 7.41 CP (g/kg) - 9.41 ash (g/kg), with R2 of 0.504 and SD of 278; or 12,504 - 10.71 CP (g/kg) - 13.44 ash (g/kg), with R2 of 0.723 and SD of 249. Pearson correlation analysis indicated that the variations in ME and MEn of the MBM samples were not related to any of the major chemical components. The results indicated that variation in each of the chemical components of MBM alone is not the sole determinant of ME or MEn content of MBM, but that the interactions among these components influence energy use in MBM for pigs.     

Comparing efficiency of metabolizable energy utilization by rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) using factorial and multivariate approaches

A study was conducted to compare utilization of ME for growth vs. maintenance in rainbow trout and Atlantic salmon. Fish were hand-fed to satiation one of four isoenergetic diets (DE = 20 MJ/kg, as-fed basis) with different digestible protein (DP) to DE ratios (24, 22, 20, and 18 g/MJ). Intake of ME (kJ/d), energy deposited as protein (PD, kJ/d), and energy deposited as lipid (LD, kJ/d) were determined by a comparative slaughter technique. Data were analyzed by a factorial approach or by multivariate analysis of PD and LD on ME. Maintenance energy requirements (ME(m)) and efficiency of ME utilization for PD (k(p)) and LD (k(f)) were estimated with both approaches. For the multivariate analysis, an additional parameter, the fraction of ME intake above maintenance used for PD (X) was defined as linear function of BW, with slope (d) and intercept (c) estimated simultaneously with the above parameters. Estimates were highly dependent on the approach and assumptions used. The ME(m) and k(p) values were higher and less accurate with the factorial approach than with multivariate analysis. The factorial approach estimated unrealistic k(f) values (k(f) > 1). With the multivariate analysis, ME(m) did not differ between species (20 kJ x d(-1) x kg(-0.8)). On the other hand, k(p) was significantly higher (e.g., 0.52 +/- 0.06 vs. 0.43 +/- 0.06; P < 0.05) for salmon than for trout and independent of diet, but k(f) was 0.81 (+/-0.13) regardless of species or diet. The ME intake above ME(m) used for PD (c) was higher in salmon than trout (57 vs. 55%; P < 0.05). The change in partitioning of ME for PD due to the change in BW was negative for trout (d = -0.18), but positive for salmon (d = 0.16). The d values agreed well with the increase of LD:PD ratio with BW for trout and the decrease of LD:PD with BW for salmon, which may have been related to the maturation status of this fish and the associated loss of body lipid observed by maturing salmon. In conclusion, ME(m) and cost of LD were similar for rainbow trout and Atlantic salmon, but the cost of PD was lower for salmon than for trout.     

Energy metabolism in lactating beef heifers

To obtain measurements of energy balance in lactating beef cows, respiration calorimetry and digestion trials were conducted using seven lactating (613 kg BW) and three nonlactating (598 kg BW) Hereford x Angus heifers fed a pelleted 75% alfalfa:25% concentrate diet. Five measurements of energy balance were obtained at 6- to 7-wk intervals beginning 6 to 10 wk postpartum in lactating heifers and at 6-wk intervals in nonlactating heifers. Milk yield was measured using a combination of weigh-suckle-weigh and machine milking to adapt heifers to milking by machine without the use of oxytocin. Heifers were milked only by machine during measurements of energy balance. Weekly milk yield averages ranged from 8.2 kg/d at wk 5 postpartum to 3.2 kg/d at wk 32 postpartum. When scaled to BW(.75), the regression of NE1 on ME intake and the regression of ME intake on NE1 were remarkably similar to previously published regressions for measurements obtained from lactating Holstein-Friesian cows. The average daily maintenance energy requirement from these regressions was 503 kJ ME/kg BW(.75), a value similar to the average value reported previously for lactating Holstein-Friesian cows (488 kJ/kg (BW.75)). This is in contrast to numerous published comparisons of the maintenance requirements of cattle breed types in the nonlactating state and current NRC standards for estimating maintenance energy requirements of beef and dairy cattle. The results of the present study suggest that when expressed on the basis of BW(.75) the efficiency of utilization of incremental ME above maintenance for milk and tissue energy (i.e., NE1) is similar among lactating Hereford x Angus heifers and lactating Holstein-Friesian cows. The breeds differ in terms of their propensity for milk yield and the resulting partition of ME between milk synthesis and tissue energy retention.     

Effects of restricted feed intake on heat energy by different goat breeds

Sixteen Boer goat doelings, 16 Spanish doelings, and 8 Angora doelings and 8 wethers, 283, 316, and 330 d of age initially (SEM = 5.0), respectively, were used to evaluate effects of nutrient restriction on heat energy (HE). During the first and second 10-wk phases, 8 animals of each breed were fed a 50% concentrate pelletized diet at a level adequate for maintenance and moderate energy accretion (CONT). Other animals were fed approximately 50% of these amounts in phase 1 relative to initial BW, followed by the greater level of feeding in phase 2 based on initial or actual BW when greater (REST). Average daily gain was 43, -20, 16, -78, 8, and -48 g in phase 1 (SEM = 5.0) and 26, 44, 50, 65, 27, and 32 g in phase 2 (SEM = 3.5) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively. Total HE was greater for CONT vs. REST in both phases (P < 0.001), greater in phase 1 for Angora than for Boer (P < 0.01) and Spanish (P < 0.01), and greatest (P < 0.01) in phase 2 among breeds for Angora [481, 347, 430, 356, 424, and 338 kJ/kg of BW(0.75) per day in phase 1 (SEM = 11.1), and 494, 479, 445, 397, 444, and 406 kJ/kg of BW(0.75) per day in phase 2 (SEM = 11.3) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively]. Equations describing the temporal pattern of HE (kJ/kg of BW(0.75) per day), expressed as a percentage of the wk-0 value and corrected for corresponding breed × week CONT means, in phase 1 were 95.8 ± 2.43 - (8.18 ± 1.144 × week) + (0.655 ± 0.1098 × week(2)) for Angora (R(2) = 0.58), 95.3 ± 2.63 - (4.34 ± 1.237 × wk) + (0.271 ± 0.1187 × wk(2)) for Boer (R(2) = 0.41), and 97.4 ± 2.21 - (4.69 ± 1.068 × wk) + (0.282 ± 0.1021 × wk(2)) for Spanish (R(2) = 0.53). Phase 2 equations were 78.9 ± 2.22 + (8.74 ± 1.036 × wk) - (0.608 ± 0.0095 × wk(2)) for Angora (R(2) = 0.60), 77.5 ± 2.10 + (3.30 ± 0.978 × wk) - (0.153 ± 0.0942 × wk(2)) for Boer (R(2) = 0.39), and 80.6 ± 2.50 + (4.50 ± 1.165 × wk) - (0.208 ± 0.1122 × wk(2)) for Spanish (R(2) = 0.43). These equations indicate that changes in HE in response to nutrient restriction and realimentation were more rapid and of greater magnitude in Angora vs. Boer and Spanish. The temporal pattern of decline in HE by Boer and Spanish during restriction was similar, but the subsequent rise with realimentation was slower and smaller for Boer. In conclusion, most appropriate methods of predicting change in the maintenance energy requirement during and after periods of limited feed intake may differ among breeds of goats.     

Energy partitioning in growing pigs: the use of a multivariate model as an alternative for the factorial analysis.

To quantify the utilization of ME by growing pigs, a factorial analysis method is often used in which the ME intake is regressed on protein (PD) and lipid deposition (LD) rates. The approach has been criticized because there often is a strong correlation between PD and LD, which makes accurate estimation of model parameters difficult. The current study describes a nonlinear multivariate analysis procedure in which PD and LD are the result of variation in ME intake. The approach requires a hypothesis concerning the partitioning of ME intake above maintenance between PD and LD. The method was evaluated using data for growing pigs of different genotypes and sex and weighing between 20 and 107 kg that were offered a diet close to ad libitum. Energy, nitrogen, and fat balances were determined at regular intervals over the growing period. The maintenance energy requirement was expressed as a function of BW (with group-specific parameters) or as a function of muscle and visceral mass. The maintenance energy requirements ranged from 913 to 1,070 kJ ME/((kg BW).60.d) for obese castrates and boars of a synthetic line, respectively. Viscera contributed 1,558 kJ ME/ ((kg tissue).70.d) to the maintenance energy requirement, whereas muscle contributed only 555 kJ ME/ ((kg tissue).70.d). It was assumed that the proportion of ME intake (above maintenance) designated for PD declined linearly with increasing BW. At 20 kg of BW, 49% of ME intake above maintenance was designated for PD in lean genotypes, whereas this was only 34% in obese genotypes. In general, with increasing BW, less energy was designated for PD, but this relationship depended on genotype and sex. Extremely lean male genotypes maintained a constant partitioning of energy between PD and LD for all BW. The energetic efficiencies varied (depending on the model used to express the maintenance requirement) between .58 and .60 for PD and .77 and .82 for LD. Extrapolation of results suggested that animals fed at maintenance energy level would still deposit protein at the expense of body lipid. It is argued that this finding requires nonbiological efficiencies of lipid catabolism and protein synthesis and illustrates the limitation of the maintenance concept for growing animals. The multivariate analysis method proposed here circumvents many of the problems associated with the factorial regression analysis of ME intake on PD and LD. The method can be used to further refine nutritional models describing growth in pigs.     

Growth rates and energy intake of hand-reared cheetah cubs (Acinonyx jubatus) in South Africa

Growth rate is an important factor in neonatal survival. The aim of this study was to determine growth rates in hand-reared cheetah cubs in South Africa fed a prescribed energy intake, calculated for growth in the domestic cat. Growth was then compared with previously published data from hand-reared cubs in North America and the relationship between growth and energy intake explored. Daily body weight (BW) gain, feed and energy intake data was collected from 18 hand-reared cheetah cubs up to 120 days of age. The average pre-weaning growth rate was 32 g/day, which is lower than reported in mother-reared cubs and hand-reared cubs in North American facilities. However, post-weaning growth increased to an average of 55 g/day. Growth was approximately linear prior to weaning, but over the entire age range it exhibited a sigmoidal shape with an asymptotic plateau averaging 57 kg. Energy intake associated with pre-weaning growth was 481 kJ ME/kg BW(0.75). Regression analysis described the relationship between metabolic BW, metabolisable energy (ME) intake, and hence daily weight gain. This relationship may be useful in predicting energy intake required to achieve growth rates in hand-reared cheetah cubs similar to those observed for their mother-reared counterparts.     

An energy response curve for a commercial white leghorn laying‐strain cross

1. Individually‐caged White Leghorn hens, 235‐d‐old, were given daily metabolisable energy (ME) intakes ranging from 707 to 1321 kj for 8 two‐week periods. Energy was the first limiting nutrient, in those cases where the differences in egg output between treatments were sufficiently large.

2. Body weight, egg number and egg weight all responded (P < 0–001) to energy intake, and as judged by regression analyses, these responses had stabilised by the fifth period.

3. For a near‐maximum egg output of 48 g/bird d, the difference between the ME requirement of the average bird and of the flock, estimated from linear and curvilinear models respectively, was 20–5%.

4. The ME requirement (Y, kj/bird d) of the average bird for egg production (E, g/bird d) and maintenance of metabolic body size (kg W°. ⁷⁵ ) corrected to an ambient temperature of 22 °C is given by the equation, Y = 440W ^0.75 + 8.96 E     

Response to Varying Dietary Energy and Protein With or Without Enzyme Supplementation on Growth and Performance of Leghorns: Growing Period

Bovans White Leghorn pullets were utilized to evaluate the use of an enzyme cocktail from 0 to 126 d of age. Dietary treatments varied in CP, ME, and enzyme (EZ) supplementation. Feed intake, BW gain, and feed conversion ratio data were gathered in addition to determining nutrient retention and digestibility during the trial. Cumulatively, feed consumption was decreased by EZ supplementation when added to a required ME diet. Body weight gains were similar across dietary treatments; however, cumulative feed conversion ratio was significantly improved with EZ supplementation. Interactions regarding nutrient retention and digestibility were numerous. Similar responses were noted for energy and protein retention values during the trial with changes in response to dietary treatments as the pullets aged. Compared with feeding an industry applicable diet (required ME/CP without EZ − $0.27/lb gain), all dietary treatments reduced production costs with significant reductions when reducing CP. Lowest feed cost ($)/lb gain and percent excreta N was feeding pullets a diet with reduced ME and CP supplemented with EZ ($0.262/lb gain; 5.19% N). Possible further reductions in ME or dietary CP, or both, with EZ supplementation may prove to be even more economical and environmentally friendly.