Net Energy For Gain Research Articles

Silage or limit-fed grain growing diets for steers: I. Growth and carcass quality.

The influence of energy source (silage- [S] or grain- [G] based) on organ growth, carcass quality, and meat acceptability independent of rate of gain was examined. Sixty-four Angus steers were allotted to one of the two treatments and given ad libitum access to silage or limit-fed grain for 145 d. All steers were then given ad libitum access to a grain diet for 45, 75, or 105 d. Eight steers from each treatment were slaughtered at the end of the growing phase and at each of the termination dates. The silage-based growing diet consisted (DM basis) of 55% sorghum silage (averaged 23.6% dry matter), 22% alfalfa hay, 10.8% ground shelled corn, and 10.8% soybean meal and contained 12.8% CP. Dry matter in the grain-based diet, composed of 76.5% ground shelled corn, 5% soybean meal, 13.6% cottonseed hulls, 3.5% molasses, and .4% salt and 1% limestone, contained 12.1% CP. It was limit-fed to produce rates of gain similar to the silage diet eaten ad libitum, using net energy for gain of each diet calculated from organic matter digestibility determined in digestion trials. The finishing diet was similar to the grain growing diet except that alfalfa hay replaced the cottonseed hulls. No implants or ionophores were used. High silage moisture decreased ADG the first 45 d, so steers fed grain gained faster, but thereafter gains were similar. At the end of the growing phase, steers fed grain had heavier shrunk and empty body weights and larger livers. However, liver size was not different when adjusted for growing ADG. By 45 d with ad libitum access to the finishing diet, 75% of the carcasses from steers fed both diets graded Choice. Steers fed silage had tougher (P < .05) steaks with less flavor intensity (P < .05) at the end of the growing phase; these differences diminished after 75 d on feed. These results suggest that choice beef can be produced in only 45 d in the feedlot, but tenderness and flavor among Choice carcasses remained inferior for steers fed silage for at least 75 d on a high-grain diet.

Feeding value of wet distillers byproducts for finishing ruminants.

Yearling and calf finishing trials (replicated over 2 yr) evaluated the feeding value of wet distillers byproducts (wet distillers grains and thin stillage). An additional trial estimated the amount of thin stillage bypassing the rumen when consumed by drinking. Yearlings were 5, 10, and 20% more efficient (linear, P < .01; quadratic, P = .05), whereas calves were 2, 6, and 14% more efficient (linear, P < .01) when fed 5.2, 12.6, and 40.0% (DM basis) wet distillers byproducts, respectively, compared with cattle fed a 79% dry-rolled corn diet. Cattle fed 5.2 or 12.6% wet distillers byproducts, or the dry-rolled corn diet, received similar amounts of protein (crude or metabolizable), which exceeded the metabolizable protein requirement of all cattle. Therefore, differences in efficiency were attributed to differences in energy utilization of the diets. Wet distillers byproducts fed at 5.2, 12.6 and 40.0% contributed 80, 62, and 47% more net energy for gain than corn when fed to yearlings and 17, 33, and 29% more net energy for gain than corn when fed to calves, respectively. Wet distillers byproducts averaged 169% the energy value of corn (2.53 Mcal of NEg/kg) when fed to yearlings and 128% the energy value of corn (1.96 Mcal of NEg/kg) when fed to calves. The increased energy values cannot be explained by increased digestibility, but they may be due to a combination of factors (reduced acidosis, increased energy utilization, yeast end products, etc.) that increase the net energy content of distillers byproducts. Approximately 50% of the thin stillage consumed by drinking bypassed ruminal fermentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Net energy for gain (NE gain) of cassava tops

The digestibility, and effect on voluntary feed intake, of various forms of cassava tops were determined. For 70 days, 15 entire lambs subdivided into 3 treatment groups, were then fed a basal maintenance ration of Chloris gayana hay with or without 200 g dry matter (DM) of cassavatops hay (CTH) or cassava-tops silage (CTS). The amount of Chloris gayana hay in the treatment groups was adjusted weekly for each animal, in accordance with its weight, in order just to meet maintenance requirements. A mineral supplement was provided and water was available at all times. At the end of the trial, the animals were slaughtered and the gross energy of the carcasses, offal and blood was determined from their contents of protein and fat. The difference between the gross energy of the control animals and those on treatment gave the net energy (NE) of the cassava tops. The results of the first experiments showed that, on average, cassava tops contained 27.1% crude protein (CP), 24.6% crude fibre (CF), 5.9% ether extract (EE) and 782.5 p.p.m. HCN in the DM; hay making seemed the most efficient method of reducing HCN content. Overall, the digestibility coefficients (%) of cassava tops were: organic matter (OM), 67.2; CF, 43.5; CP, 79.5; and EE, 51.7. Feeding cassava tops together with Chloris gayana hay, which was offered to sheep as the basal diet, improved voluntary feed intake by the animals. In the NE study CTS was significantly ( P <0.05) more digestible, and resulted in intake of more metabolisable energy (ME), than CTH. In spite of this superiority, the energy in the CTH was better utilised for gain. The NE values of CTH and CTS were 2.22 and 1.67 MJ kg −1 DM, respectively. This apparent contradiction was explained in terms of thyroid malfunction as shown by the greatly enlarged thyroid glands of the animals feeding on CTS containing high HCN content. It is concluded that, for animal production purposes, CTH should be preferred over CTS.

Effect of lasalocid on feedlot performance and energy partitioning in cattle.

Two experiments were conducted to quantify the effects of lasalocid on the performance and energy partitioning of cattle fed a 90% concentrate, barley-based diet. Experiment 1 utilized 100 Hereford heifers (initial weight 308 kg) fed diets containing no added ionophore, lasalocid added at 24, 36 or 54 mg/kg dry matter (DM), or monensin added at 33 mg/kg DM. In the 98-d trial, lasalocid-fed heifers gained an average of 1.35 kg daily, whereas control heifers gained 1.24 kg (P = .12). Heifers fed lasalocid (36 or 54 mg/kg DM), monensin, and the control diet required 6.2, 6.5 and 6.9 kg DM/kg gain, respectively (P greater than .1). Ionophores had no influence on carcass quality. In Exp. 2, four steers (616 kg) were fed the control or lasalocid diet (36 mg/kg DM) at daily feeding levels of 21, 44, 67 and 89 g DM/kg body weight.75; fecal, urinary, methane and heat losses were measured by total collection and indirect calorimetry methods. The proportion of digestible energy lost as methane averaged 7.5% for steers fed the control diet and 7.1% for the steers fed lasalocid (P less than .1). Lasalocid improved (P less than .05) the metabolizable energy (ME) density of the diet by 8, 8 and 5% at the 21, 44 and 67 g DM feeding levels. There was no difference (P greater than .1) between diets in ME density at the 89 g DM feeding level. The net energy for maintenance (NEm) value of the diet was increased (P less than .05) by 10 to 21% with lasalocid, whereas the net energy for gain (NEg) value was not affected. Average heat productions of the steers were increased (P less than .05) by 7% with lasalocid. The ME requirement for maintenance was estimated at 84 and 81 kcal/kg body weight.75 from linear regressions of energy retention and ME intake above maintenance for the control and lasalocid diets, respectively. Corresponding estimates using a semilog-linear method were 90 and 92. No differences (P greater than .1) in blood concentrations of insulin, glucagon or growth hormone were observed with the ionophore treatment. It was concluded that the main method by which lasalocid improved feed conversion was by increasing the ME density of the diet.

Effects of energy intake on energetic efficiency and body composition of beef steers differing in size at maturity.

Hereford and Charolais steers were fed at three levels of feed intake (low, medium or ad libitum) to similar weights within breed groups to evaluate effects of energy intake on energetic efficiency and body composition. Two methods were employed to partition metabolizable energy intake into use for maintenance and gain. Method one used an assumed daily fasting heat production of 77 kcal/weight (W).75; method two estimated fasting heat production from the regression of log daily heat production against metabolizable energy intake (kcal/W.75). Net energy for gain (NEg) was determined in method one by regressing retained energy (kcal/W.75) against feed intake (g/W.75). For method two, the estimated maintenance requirement of feed was subtracted from total feed intake and retained energy was regressed against feed intake above maintenance to estimate NEg. Conclusions regarding feed energy utilization for maintenance and gain were the same by either method of energy partitioning. Charolais steers used feed energy less efficiently for gain than Hereford steers, and ad libitum steers used feed energy less efficiently for gain than steers at lower intakes (P less than .05). Charolais steers made leaner (P less than .05) gains than Hereford steers. Although steers consuming the lowest level of feed made gains containing a lower percentage of fat and a higher percentage of protein (P less than .05) than steers at higher intakes, body composition within a breed was not altered by level of energy intake when animals, within breeds, were slaughtered at similar end weights.

Using Net Energy for Gain and Maintenance in a Quadratic Equation to Calculate Beef Cattle Diets

Using Net Energy for Gain and Maintenance in a Quadratic Equation to Calculate Beef Cattle Diets

Effects of Diet and Energy Intake on Kinetics of Glucose Metabolism in Steers

To test the hypothesis that glucose utilization in ruminants is related to energy consumption independent of diet composition or energy content, eight Holstein steers (165–230 kg) were fed either a high grain (70% corn, 20% alfalfa, 8.8% soybean meal) or high hay (70% alfalfa, 28% corn) diet. The two diets were fed in quantities that allowed comparisons to be made either isocalorically based on calculated net energy for gain (NEg) or at identical dry matter intakes. The daily ration was divided into 12 equal portions and dispensed every 2 hours by automatic feeders to achieve steady-state conditions with respect to glucose metabolism. After adaptation to the dietary regimen, rates of glucose irreversible loss were measured following a single injection of 500 µCi of [6-3H]glucose. Glucose irreversible loss also was measured after a 7-day fast. Glucose irreversible loss was equal when both diets were fed isocalorically, was larger among steers fed the grain diet when comparisons were made at equal intakes of dry matter, and increased when the intake of either diet was increased. The increase in glucose irreversible loss with increasing energy intake showed a highly significant linear relationship over the range of intakes for both diets. It was concluded that energy intake, in contrast to diet composition, is responsible for the regulation of glucose irreversible loss.

Effect of Roughage Fraction of Cattle Manure on Digestibility and Net Energy of Feedlot Diets Fed Steers

Diets containing 0, 20, 40 or 60% (wet weight basis) of a processed manure roughage obtained from a commercial feedlot were evalulated with steers for digestibility, net energy, feedlot performance, carcass characteristics and mineral accumulation in tissues. The manure roughage stimulated feed intake and body weight gains even though it depressed metabo-lizable energy (ME) and TDN of the diets. Steers offered ad libitum 0, 20, 40 and 60% manure roughage diets over 124 days gained 1.10, 1.53, 1.58 and 1.51 kg per day, respectively. The NEm requirement of the steers was determined to be 78 kcal perW·75kg· Net energy for gain was not depressed in diets with increasing levels of manure roughage. Dressing percentage, USDA carcass grade, maturity, marbling, flavor, juiciness, tenderness and overall acceptance of the steaks were not effected by the manure roughage. There were no toxic levels or accumulation of Hg, Pb, Cd, Ni, Cu, or Fe in any of the diets or tissues (muscle, liver, kidney).

Feeding Value and Net Energy for Gain of Spent Sulfite Liquor for Beef Cattle

Eighteen Hereford steers individually housed and fed were utilized to study the effects of incorporating 8 and 12% spent sulfite liquor (SSL) into finishing rations. No significant differences in average daily gains were detected between the control and SSL groups. Feed efficiencies (kg feed/kg gain) were similar for the control and the 8% SSL group, but slightly lower for the 12% SSL treatment group. Incorporation of SSL into the rations did not affect carcass characteristics or carcass grade of the experimental animals. Net energy for gain (NEg) of SSL was determined by the difference trial procedure involving the determination of energy gained by the animals comparing initial and final body composition. The NEg of SSL, on a dry matter basis, was determined to be .74 and 1.40 Mcal per kilogram when fed at the 8 and 12% levels, respectively. The difference in the NEg value of SSL when fed at different levels in the rations was attributed to interactions of SSL with the molasses or other ingredients of the experimental rations.

Energy Requirements and Growth of Captive Lesser Scaup

Energy requirements of captive Lesser Scaup ducks (Aythya affinis) were determined from hatching to 12 weeks using a feeding trial and comparative slaughter method. Food intake was measured directly; metabolizable energy intake by a chromic oxide indicator and calorimetry; net energy for gain by comparative slaughter; and total heat production by difference. Live weight growth was measured and dry matter growth estimated from a regression of percentage dry matter on age. Food intake (dry) increased from 6.7 gm./duck/day during the 1st week to a peak of 52.5 gm. in the 5th week. Metabolizable energy intake averaged 5,575 Kcal. during the first 7 weeks, the assumed preflight period. Percentage carcass dry matter increased from 30 percent at 1 week to 45 percent at 12 weeks. A similar trend occurred in wild scaup though percentages were lower due to the lower fat content. Data are given for the proximate composition of carcasses for the first 12 weeks.

ENERGY UTILIZATION BY THE LACOMBE AND YORKSHIRE BREEDS OF PIG

A comparative slaughter trial involving 32 weanling pigs was conducted to estimate the energy requirements for maintenance and production and to compare the energetic efficiency of Lacombe and Yorkshire pigs. The coefficients of digestible energy (DE), metabolizable energy (ME), and ME/DE ratio were similar for the two breeds. The fasting heat production and energy requirements for maintenance of energy equilibrium for the Yorkshire pigs were significantly higher (P &lt; 0.01) than for the Lacombe pigs. Differences in the efficiency of utilization of ME for the function of maintenance and for production were not significant. Estimates of net energy for maintenance and net energy for gain of the corn-soybean meal diet are presented. The study suggests that these net energy values, like the DE and ME values, may be used for diet formulation without need for correction for breed. The use of the exponent 0.56 rather than 0.75 as the reference base of metabolic body size led to increased precision, as indicated by higher estimates of the coefficient of determination.