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Paper-Lecture33 - A SYSTEM FOR EXPRESSING NET ENERGY...

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Unformatted text preview: A SYSTEM FOR EXPRESSING NET ENERGY REQUIREMENTS AND FEED VALUES FOR GROWING AND FINISHING BEEF CPLTTLE t}. P. LUFtJ-HEEN awn W. N. Gaansrr University of California, flaair 1 ". Y in 19:33 the authors introduced a . energy system designed for use in the _-u; and finishing phase of the beef cattle - (Lofgreen, mess, b, c]. The system -' -u the requirements for maintenance that for body weight gain and expressed _'energy value of the feed for these two -: 1.1 . Such a system of expression was am to the Nutrition Committee of the ,u: Research Council and was included _' first printing of the NRC. Bulletin of or energy terminology as an errata replacing the original terminology {Har- 9152}. For the past 4 years the suggested -u has been tested under various condi- at this station, in commercial feedlots, _'| nutrition consultants working with the 1 feeding industry and its adaptability to - has been demonstrated. It is the purw ' of this paper to present the proposed sys- in the scientific literature, describe the . n - Ital data upon which it is based, and ,- its application. The terminology used '-- is that suggested in the first revision of ' '.R.C. Bulletin on energy terms (Harris, 1')" I Development of the Method _'. partial efficiency of energy utilization hiatutenance is higher than it is for produc- ,_.- (Kleiber, 19151}. The net energy .of a 1Il'lll then vary with the level of feeding, --; higher at low levels of feeding and de— _-. I; as feed intake increases. It is obvious, - m , that a system based upon net energy weight gain does not deviate significantly from linearity. This means that the partial net energy of a feed when utilised for weight gain above maintenance can be considered to be constant. The partial net energy for main- tenance of that quantity of feed needed to maintain energy equilibrium is equal to the heat production of the fasting animal. It is therefore more nearly constant than total net energy because it depends to a large degree upon the relatively constant basal heat pro— duction {Kleiben 1953). The partial net energy of feeds for maintenance (NE...) and the partial net energy for production of weight gain {NEE}, therefore, are more nearly con- stant then is the total net energy of a feed for both maintenance and weight gain (NE...+,,]I, the latter being a weighted average of the NE... and NE... depending upon the level of feeding. It seemed logical, therefore, that a. net energy system based upon the separate expressions, NE... and NE”, would be more accurate than one based upon NE...+,, which is known to vary with feeding level. Determination of NE... Requirements. In order to measure the NE... requirement it is necessary to know the heat production of the fasting animal since this quantity of net en- ergy must be furnished to keep the animal in energy equilibrium. Classically, the heat pro- duction of the fasting animal has been con— sidered to be equal to basal metabolism and is often expressed as WWW” with heat produc- tion expressed in kcal. and W is bodyweight in kg. Measurement of basal metabolic rate on large numbers of ruminants is tedious and con- take this into consideration by listing ate net energy values for different physi- -_nr functions or incorporating efficiency _- utilisation values for these functions. ,' u..: at this institution {Lofgreen ei eh, ' ;_Garrett et at, 1964] have shown that, .n maintenance to ad iifiitam feed consump— , the partial net energy of a feed used for sequently such measurements are not normally made with large groups. It is possible to indi- rectly measure heat production (HP) at zero feed intake by deducting energy balance (EB) from metabolisable energy intake (ME) thus HPzME—EB. Metabolisablc energy is determined by de- ducting from the gross energy the energy of the feces, urine and methane, and energy re— rr.. "eat of Animal Science, Part of fire rlata used .1?“ accumulated in studies which Iwere conducted as .Weslern Regional Research ProJcct W EH, flange --.. Nutrition. T93 194 tained is determined by a comparative slaugh— ter method. In fed animals, HP“ is made up of basal metabolism, heat increment and heat produced by activity. At zero feed intake, however, heat increment is zero and the com- ponents of HP are basal metabolism and heat of activity which can he considered to be equal to the net energy required for maintenance or NEm. If HP is measured at various levels of feeding it is possible to estimate HP at zero feed intake by extrapolation. Data from five comparative slaughter trials were used to ob— tain an estimate of heat production at zero feed intake and thus an estimate of the NE... requirements. The studies involved a total of 212111 feeder cattle varying in initial weight from approximately 2.11:} to 31.10 kg. In four of the trials, the cattle were individually fed their respective diets while they were group- fed in the fifth trial. The five diets used varied from 2 to 112112151?- roughage and were fed at two or three levels of intake from maintenance to ad team. In one trial a 25}?- roughage diet LDFGREEN AND GARRETT was fed at three levels of intake, one approxi mating maintenance, one at ed ffoftam int and a third at an intermediate level. A seoo trial involved a lflflffii- roughage diet fed maintenance, intermediate and ed Hid-tam levels. In these two trials, tbree replicates of six animals each were fed at each of the three levels of intake {Lofgrcen at at, 19153}. In a third study a 211% roughage diet was fed at maintenance and ed iihitum to a group of eight animals at each level of feeding (Lof- green and Dtagaki, 19:50}. A fourth trial in- volved the feeding of a 25??- roughage diet at three levels of intake with three replicates of eight animals each at each level of feeding (Garrett, 191351 while in the fifth experiment a 41213}? roughage diet was fed at two levels to two replicates of six animals each [Lofgreen ct 131., 19152). In each case energy retention was measured by the comparative slaughter method (Mfgreen, 1964) and heat production calculated by deducting energy retained from metabolizable energy intake. Table 1 presents TABLE 1. RESULTS 0F FIVE COMPARATIVE SLACGHTER TRIALS Metabolit- Daily able energy Ene rgy Heat Kind of No. of Level oi Mean empty wt. intake relained prodneed ration animals Sex feeding W‘”“hu- gain {:1 (ME) {EB} {HP} 5'53 run-15113113 kg EC31._.-'It'i.fi.}' DC! “rental!- If: Heifers Low 51.9 —-.D4- 121 —1 122 ti Heifers LEW 53.12 —.04 142 -—1 1-13 6 Heifers Low 53. it t}. D? 142 CI 142 1‘1 Heifers Medium Eel-.1] D . 24 IUS 11" 131 11310 d Heifers Medium I54. 2 El. 25 193 1d 131‘ El Heifers Medium 6.1 .2 0 . 23 194 15 1'19 5 Heifers Art fiti. 155.9 D. 6:1 21:10 44 2411 IS Heifers rid fifi. 51.5 {1.5"} 3131 42 25"? IIS Heifers Ad 11:11. I56 . H 0. 62 .102 311 2154 If: Steers Lew I54 . 1 -'— . D? IUD —T 1111' to e Steers Act as. 19.0 o . 64 204 .11 1 is s Steers Low I50. I [1.0-1 1.33 1 132 H Steers Low 154.1 {1.20 125 .1 122 3 Steers Low 15.1.6 11.113 125 5 1213 3 Steers Medium as _ .1 o. is 194 23 1'11 23' 8 Stee- rs Medium 20.11 [1. 1.1 136 18 163 3 Steers Medium 159 . 1' U. :19 19D 26 16-1- 3 Steers Ad iii}. 111.3 1 .32 3.15 he 26'] S Steers Ad Eb. W . 5 1 .33 iii? '23 2.11 B Steers Adfliti. 15.5 1.14 264 59 205 3 Steers Low 15 . '1' 131.30 141 '5' 134 20 3 Steel‘s 211511111. 33.15 1.01 2111-1 55 209 I5 Heifers Low (11.2 £1.11] 116 9 1111' fr Heifers Low ISLE: 0.16 1.11 14 11? d Heifers Low 6.1. i" U .119 1.14 3 126 fi Heifers Medium 1131 . .1 U. 1'1} 202 4? 155 2 ti Heifers Medium 1161.6 [1.53 196 .i'? 159 d Heifers Medium I53 . 9 t}. 51' 109 40 15? fr Heifers Ad Hit. 1'3 . .1 1.1311 258 22 186 I33 Heifers :trf riff). '25 ..i 1.11 212 '15 19? fi Heifers .‘irfit'b. -TI'.‘-.1 1.14- 269 12 191' SYSTEM FOR NET ENERG‘J:r REQUIREMENTS 30D 23's 2’95 EEHPDIHTISTHEMEAHDFEIDEB 250 ANIMALS . 225 § E HID HID lED new HEAT emanate. HEAL. {wfif 8 90 it So too TDITAL = 203 I5|iiiI Lee as =I.sa5r + domes ME = 0.9? 5,... = oozes 2130 25B 3'00 356 mar merssootaate easier INTAKE. muwfif Figure 1. Determination of fasting heat production. a summary of the results of the five trials and figure I shows the relationship between heat production and metaboliaable energy intake. In describing this relationship a logarithmic equation was used since extrapolation to zero energy intake results in a more realistic esti- mate of fasting heat production. Over the range from maintenance to ad fibitnm feed consumption, however, the relationship does not differ significantly from linearity. The equation describing this relationship is Log HP:1.3351+fl.flDtooIth where HP and ME are in kcal. per film-"mg. The log of the heat produced by the fasting animal, therefore, is equal to LESSI-t-DDZQS. The antilogs of these limits are '12 and 32, indicating that the heat production of fasting beef cattle probably lies between H and 32 ltcal. per 1 ”mm with the mean value being i‘? kcal. The average NE... requirement for these cattle, therefore, can he considered to be equal to i”? kcal. per urn-75..., Since it is normally more convenient to express energy require- ments of cattle in megcal, the NE... require— ment can be Expressed N HJJJ:U.D??1lt-m'w (l l' where NE... is in megcal. per day and W is bodyweight in kg, In order to compare the NE,“ requirements of steers and heifers, data were examined from two comparative slaughter experiments in which steers and heifers were fed the same rliets. In one trial, 64 steers divided into eight- steer replicates were compared to 64 heifers, with each sex being fed a 25?; roughage diet at a restricted and ed fibitflm feed allowance. 1'96 In the second trial 54 steers were compared with a like number of heifers. Three six-animal replicates of each sex were fed at a low, me- dium and as] seem feed allowance (Garrett at at, 1964]. The results of the two studies are shown in table 2. Since the proportion of roughage to concentrate was not the same at all levels of feeding these data do not permit an accurate estimate of the true heat produc- tion at zero intake as was done with the data in table I. They do, however, permit a direct comparison of the two sexes to determine if there is a difference in the heat produced at no feed intake and thus a difference in the maintenance requirement. The relationship of heat production and metabolizahle energy in- take for the steers and heifers is compared in figure 2. The points of origin of the two re- LDFGREEN AND GARRETT greasion equations are not significantly differ- ent, indicating that the heat produced by fast- ing steers and heifers is not different and thus the energy requirement for maintenance per unit of W675“, is not different. It appEars, therefore, that the energy expended for main- tenance for both steers and heifers can be estimated by equation 1 and is equal to 0.01? megcal. per W"-”kg_ Determination of NE... Values of Lee Re- fine. That quantity of feed intake per unit of WG-75“ required to maintain the animal in energy equilibrium will have a NE... equal to the heat produced at no feed intake or 0.02? megcal. The feed intake required to maintain energy equilibrium can be measured rather simply from the relationship of heat pro- ' duced to metabolizable energy intake. If a TABLE 2. COMPARISDN 0F STEERS AND HELFERS FED THE SAME RATIflN Kind of No. of LeVEI of ration animals Sex feeding 6T;- roughage 3 Steers Low 3 Steers Low 8 Steers Low 5 Steers. Low 25 3 Steers Ar! Eff). S Steers Ad H6. 3 Steers Ad 6'6. 3 Steers aid as, 6 Steers Low 40 6 Stet rs Low 6 Steers LOW ti Steers Medium 2.1 6 Steers Medium 6 Steers Medium 6 Steers Ari iii}. 30 6 Steers Ad lib. 6 Steers Ari Hill. 3 Heifers Low it Heifers Low 8 Heifers Low E! Heifers Low 25 E Heifers Ad £26. 3 Heifers Ad Hit. it Heifers Ad Eff}. B Heifers Ad H6. 6 Heifers LOW 40 6 Heifers Low 6 Heife rs Low 6 Heifers Medium 2.! 6 Heifers Medium 6 Heifers Medium 6 Heifers Ad 156. 30 6 Heifers A of lib. 6 HEifErs :lt'i iii). Metabolis— Daily ahle ei'lerysir Energy Heat Mean empty wt. intake retained pmdueed “nus“... gain {g} {ME} {EH} {HP} kg. kcal.,r'day per W205“... 63.? 6.2? 1411 11‘ 123 63.6 0.32 156 10 146 63.6 0.31 151 21 1.10 21.4- 6.52 16‘} 25 144 30.0 1.14 22-4- 62 ' 212 30.3 1.16 226 21 205 82.5 1.32 2119 1'10 209 29.2 1.16 262 22 1910 65.5 0.1? 144- 13 131 66.3 0.18 146 1.1 1.33 69.3 0.15 146 14 1.12 24.2 0.64 200 36 16-4 69.5 0.55 196 .10 166 21.4 0.62. 203 .59 169 28.4 1.15 232 2.5 209 25.0 1.09 236 63 212 28.3 1.12 2115 '33 212 65.0 0.22 144 1.1 131 62.4 0.32 164 24 140 64.1 0.36 155 22 153 om. 0.5? 132 54 145 24.5 1.16 290 23 212 25.2 0.96 26? 63 19'} 24.9 1.21 23‘} '92 19? 22.0 1.10 223 26 262 60.4 0.20 143 12 13-6 60.1} 0.15 142 15 132 60.2 0.151 14'}I 12 1.3-iIr 65.1 {1.61 20? 41 166 66.6 0.53 203 40 16ft 66.5 0.6.1 21'.il 43 124 22.2 1.02 290 21 219 22.9 1.02 22:7 21 204 22.1 1.10 302 '24 223 SYSTEM FOR NET ENERGY REQUIREMENTS soo Tera. = 250 I—I ST EERS II- - —-n HEIFEHS 2D!) - iflfl ' I69 I a IT: D STEEREl I09 HE lFEflS: [ll‘lilL‘It HEAT PHDUUEED. HEEL. [WES 50 Cl .50 I'EifJ I50 1'9? EACH NINTH IS THE MEAN DF 6 DR 3 ANIMALS. IIB flF EACH 3E! LEE HP = I30?! + ELDOMI' ME Lfli HP = Hill“! 1- EDD”! ME 250 6er Mtrasmzaate earner lanes. seen; WEE‘E 20D 3CD " 35G Figure 2. Comparison of the heat production of steers and heifers. diet is fed at an ad iffziram. level and the heat production determined, one may use this quantity of heat produced as one point in a regression line and the heat produced at fast- ing as a second point to establish a regression of heat production on metaboliaable energy intake. From the equation describing this re— lationship, the metabolizable energy intake and quantity of feed consumed at energy equilibrium can be determined. For example. from the data in table 1 for the heifers fed 106% roughage ad fihiium, it can be calcu- lated that the mean heat production is 264 kcal. at a metaboiiaable energy intake of 298 keal. Using this as one point and if [tea]. as heat production at zero metaboliaable energy intake, the regression equation describing the linear relationship between log HP and 1'th E is Log [-1le .Efldfi—l—UDUHSME. It can be determined from this equation that energy equilibrium can he achieved at an in- take of 131 kcal. of mctabolizable energy per tt’“-”...._ since at this intake heat production is also equal to 131 keel. At a metabolizable energy content of 2.64 kcal. per gram of feed, it would require 64.;I gm. of feed to furnish 131 kcal. oi metabolizable energy, and thus energy equilibrium could be maintained on an intake of 64.2 gm. of this feed per W'Lfius. This quantity of feed has a NE... equal to the heat production at fasting or 'i'i' kcal. The NE... of this feed is tltdrefore T? kcal. in 64.2 gm. or 1.26 megcal. per kg. Determination of NE. Requirements. The NEg requirement for weight gain is simply the energy deposited in the gain. In table 3-, data are shown comparing the energy deposited by 264 steers with that deposited by an equal number of heifers at different rates of gain. in each comparison. the steers and heifers were fed the same diet. The correlation coeffi- cients between empty weight gain and energy gain were 0.9? and {1.93 for the steers and 293 LDFGREEN AND GARRETT TABLE .1. GAINS IN EMPTY BODYWEIGHT AND ENERGY 0F STEERS AND HEIFERE FED THE 5351?: RATIONS Steers Heifers Number of Daily empty Daily Daily empty Daily each sex Mean Wm“. wt. gain energy gain Mean W'lfla wt. gain energy gain kg. megtal. kg. megcal. 6 69.3 0.15 0.920 60.2 0.13 0.222 6 63.3 0.12 0.333 60.4 0.20 0.225 6 66.3 0.13 0.362 60.9 0.13 0.914 3 61.0 0.23 1.055 62.2 0.33 1.432 8 63.2 0.22 1.163 65.9 0.22 0.352 3 63.6 0.31 1.441 64.1 0.35 1.410 8 63.6 0.32 0.636 62.4 0.32 1.613 6 69.9 0.33 1.426 62.4 0.36 1.392 6 63.5 0.3.1 0.199 26.5 0.32 1.645 6 64.9 0.35 1.053 61.5 0.22 0.640 3 65.9 0.49 2.320 65.6 0.69 3.203 3 66.5 0.51 1.902 62.0 0.66 2.630 3 21.4 0.52 1.235 62.4 0.52 2.292 6 21.0 0.54 1.605 29.3 0.59 2.236 6 69.5 0.55 2.035 66.6 0.53 2.664 6 21.5 0.56 2.653 66.0 0.62 3.300 l6 21.4 0.62 2.235 66.5 0.63 2.360 6 66.5 0.64 2.514 66.1 0.60 2.300 6 24.2 0.64 2.621 65.1 0.61 2.669 6 69.5 0.20 2.643 62.3 0.65 2.430 6 20.2 0.23 2.969 65.6 0.62 2.519 6 24.3 0.33 2.230 30.2 0.24 3.532 6 24.0 0.33 4.144 66.9 0.29 3.931 6 24.0 0.34 2.319 30.2 0.21 3.301 3 69.3 0.90 3.290 20.9 1.05 4.495 6 23.0 1.09 5.304 22.9 1.02 5.126 6 22.0 1.09 4.639 33.4 1.05 5.230 6 22.0 1.10 6.160 20.2 1.13 6.315 6 23.3 1.12 5.213 22.1 1.10 5.335 3 30.0 1.14 4.960 24.5 1.16 5.311 6 23.4 1.15 5.223 22. 1.02 5.126 3 30.3 1.16 5.201 25.2 0.96 5.114 3 29.2 1.16 5.233 22.0 1.10 5.352 6 24.5 1.13 5.352 21.4 1.04 5.193 6 23.6 1.20 5.625 21.9 1.13 6.013 o 15.5 1.22 5.551 32. 1.61 5.113 3 32.5 1.32 6.60.1 24.9 1.21 6.391 heifers, respectively. In order to determine if the energy concentration in the weight gain changes as the rate of gain increases and to compare the rate of change of steers and heifers, an equation of the type YZEXI' was fitted to the data. ‘2 in this equation is the energy gain, X is the empty weight gain and a and h are constants determined from the data. This type of equation was chosen since it passee through the origin and thus gives realistic values at low rates of gain and the exponent, 15, represents the ratio of the specific rates of increase of Energy gain and weight gain. The numerical values of h for steers and heifers were 1.11 and 1.13, respec— tively, indicating that with both sexes the energy concentration in the weight gain in— creases as the rate of gain increases and that the increase is more rapid in heifers. To elimié nate the effect of body size, the relationship between energy gain in heat. per unit of 1312-75” and empty weight gain was deter- mined. The values of the exponent, is were re- duced to 1.02 and 1.02 for steers and heifers, respectively, by expressing energy gain per unit of Wit-75w, indicating that hodyweight was accoUnting for some, hut not all, of the increase in energy concentration of the weight gain as rate of gain increased. In order to oh- tain the best estimate of the relationship he- tween energy gain and weight gain, the stand- ard error of the estimate obtained from the exponential equation was compared to that of SYSTEM FOR NET ENERGY REQUIREMENTS a parabola and a parabola adjusted to pass through the origin. The standard errors of the estimate were 6.45, 5.9 and 6.0 for the three curves for steers and 5.42). 4.4 and 4.5 for heifers. Since the parabola which passes through the origin has essentially the same standard error as the unadjusted parabola it was chosen because of the more realistic val— ues obtained at low rates of gain. Figure 3 presents this relationship for steers and figure 4 for heifers. Thus for any size animal the energy stored in the weight gain or the NE... requirement can be expressed for steers NEu:i52.?2g+fi.34g3_}{utters} (2} [Hr heifers NEg: (Shillg—l— I 2455?} Hydro) {.3} where NE... is in kcal.. g is daily gain in kg. and W is bodyweight in kg. Determination of .-"t-'E_.. Vetoes of the Ration. The NE: value of a feed is equal to the energy deposited in the hodynveight gain brought about by feeding the particular feed in ques- tion. This has normally been determined by feeding the experimental diet at two levels and measuring the energy deposition brought é F99 about by the increase in feed intake between the two levels. This has classically been called the “difference trial.” Table 4 illustrates a difference trial involving the data shown in table 1 for the heifers fed 100% roughage. In this case the ad iibittim feed intake served as one level of feeding and the intake at energy Equilibrium as previously determined served as the second level. Any two levels of feeding above maintenance can he used in a difference trial but a large difference will result in a more accurate estimate of the NEg value of the ration. The NE... value of {1.5 megcal. per kg. for the lflfifit roughage diet can b...
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