Utilization Of Metabolizable Energy Research Articles

Utilization of energy for growth in lambs of the breed german merino landsheep

Based on energy deposition and energy intake the utilization of energy for fat and protein deposition and the mean energy utilization for growth as well as the energy requirement for maintenance were estimated in this study. Fifty-four male and 54 female lambs were fed at three feeding levels and slaughtered at various body weights (BW): 18, 30, 45, and 55 kg. Based on the method of the comparative slaughter technique the total body of each animal was analysed. From the data of empty-body gain, fat, protein and energy deposition in the different fattening periods was calculated. The utilization of metabolizable energy for growth and maintenance was estimated by a multiple linear regression model. In this regression model, a utilization of energy for fat deposition of 71% and for protein deposition of 30% was determined (R2 = 0.869). The requirement for maintenance was 520 kJ·kg BW − 0.75·d − 1. A slightly higher requirement for maintenance was determined for female lambs. The study indicated that the used regression model can be recommended to estimate the utilization of energy and the requirement for maintenance in growing lambs.

Effect of Protein Sources with Different Rumen Degradability in a Diet on the Efficiency of Utilization of Metabolizable Energy by Calves

Abstract. To evaluate the effect of dietary protein of diverse rumen degradability on the efficiency of metabolizable energy (ME) utilization by calves at the growth and maintenance levels of feeding. A total of 54 energy balance trials were conducted using 18 Holstein castrated male calves given four diets containing soybean meal (SBM), cottonseed meal (CSM), heated soybean meal (HSBM) and corn gluten meal (CGM) as a main source of protein. The trials were carried out at the ages of 13 weeks for the growth (G) level of feeding and 15 weeks for maintenance (M) followed by the 24-h measurement of fasting (F) heat production after 3-day fasting. The dg values were 0.657, 0.543, 0.463 and 0.413 for SBM, CSM, HSBM and CGM, respectively. The regression analyses of energy retention (ER, kJ/W0.75) on the intake of ME (IME, kJ/W0.75) above the maintenance level revealed no significant differences among diets and gave a following pooled equation: ER = 0.56(±0.04)IME – 311, r = 0.897 (P<0.01). The below M level resulted in the following two distinct equations for the diet with a higher dg of protein source and that of a lower dg: ER = 0.77(±0.02)IME – 403, r = 0.994 (P<0.01) for SBM + CSM. ER = 0.60(±0.03)IME – 350, r = 0.982 (P<0.01) for HSBM + CGM. We concluded that ME utilization for maintenance may be influenced by the protein sources of different dg, but not for growth.

Growth and feed conversion of Boran ( Bos indicus) and Holstein×Boran heifers during three physiological states receiving different levels of a tropical diet

Forty-eight heifers of two genotypes, Boran ( Bos indicus) and Holstein×Boran, were allocated to three feeding levels equivalent to 1.0, 1.2 and 1.4 times calculated metabolisable energy requirements for maintenance (ME m). The experiment started at the onset of reproductive activity, when the Boran and crossbred heifers were 4.4 and 2.2 years old, respectively. The response to feeding level was investigated in three physiological states: (i) puberty and growth (87 days), (ii) work and growth (94 days, 51 days thereof with work), and (iii) pregnancy and recovery from work (115 days). Neither genotype nor feeding level had effects on nutrient digestibility, digesta passage rate and reproductive performance. Daily gains and feed conversion efficiency were higher in well-fed heifers ( P<0.001 and P<0.01). Estimated ME m was 0.54 MJ/kg metabolic weight ( W 0.75) in both genotypes during puberty and growth. Imposing work required additional 0.20 and 0.10 MJ ME/kg W 0.75 in Boran and crossbreds, respectively. Recovery from work, associated with early pregnancy, apparently reduced ME m to 0.30 MJ/kg W 0.75. This could be explained as a result of compensatory growth. The efficiency of utilisation of metabolisable energy for growth (0.28) did not differ ( P>0.1) between genotypes and physiological states.

The Nutritive Value of Cocoa Shell in Ruminants

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The Influence of Different Fiber and Starch Types on Nutrient Balance and Energy Metabolism in Growing Pigs

A repeated 4×4 Latin square design was conducted with eight ileal cannulated castrates to examine the effect of source of starch and fiber on nutrient balance and energy metabolism. Pigs were fed on one of the four experimental diets: Control diet (C) mainly based on cooked rice; and diets P, S and W with the inclusion of either raw potato starch, sugar beet pulp or wheat bran supplementation, respectively. With the exception of an increased (p 0.05) in the ratio of metabolizable energy (ME)/digestible energy, the utilization of ME for fat deposition and for protein deposition, energy loss as hydrogen and urinary energy were found between diets. The efficiency of utilization of ME for maintenance was lower (p 0.05) by addition of potato starch. In comparison with diets C and P, a lowered ileal or fecal digestibility of energy with diets S and W was observed (p 0.05). An increased (p<0.05) proportion of NSP excreted in feces was seen by the supplementation of wheat bran. Higher NSP intake caused an increased daily amount of NSP in the ileum, but the ileal NSP proportion as a percentage of NSP intake was unaffected by diets. Feeding potato starch resulted in increased daily amount of starch measured in the ileum and the proportion of ileal starch as a percentage of starch intake, while no significant influence on fecal starch was found. Higher (p<0.05) daily amount of fecal starch and the proportion of fecal starch as a percentage of starch intake were found with fiber sources supplementation compared with diets C and P. By increasing the dietary NSP content the fecal amount of starch increased (p<0.01). (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 2 : 263-270)

A dynamic model of metabolizable energy utilization in growing and mature cattle. I. Metabolizable energy utilization for maintenance and support metabolism

Models to predict heat production attributable to maintenance and support metabolism in growing and mature cattle were developed on the basis of three concepts. The first concept is that animals fed fixed amounts of the same diet achieve weight equilibrium over an extended feeding period, and that the ME consumed at weight equilibrium is the maintenance requirement. The second concept is that a part of the heat production resulting from ME consumed above the maintenance requirement is associated with an elevation of vital functions (support metabolism), and this heat production can be modeled as a function of the level of feeding. The third concept is that previous levels of nutrition affect current estimates of heat production, and that this impact can be modeled as a delayed response in heat production associated with support metabolism. Experimental data on feed consumption showed that maintenance requirements varied in simple proportion to BW, not only for different breeds of mature cattle at BW equilibrium, but also for calves and growing steers held at BW stasis. Experimental data in which different breeds of cattle achieved weight equilibrium when fed fixed amounts of a specific diet were used to estimate breed parameters associated with maintenance for 21 breeds of cattle and 15 biological types of crossbred cattle. Level of feeding was estimated as a multiple of the maintenance intake and used to model heat production associated with support metabolism. Other experimental data on growing cattle were used to estimate breed parameters for predicting heat production associated with support metabolism for 21 breeds of cattle and 15 biological types of crossbred cattle. A distributed lag function was used to model the delayed response in heat production associated with support metabolism with changes in plane of nutrition. The models were tested by simulating experimental data for three breeds of weaned steers finished on high-energy diets. Results for the total heat production associated with maintenance and support metabolism expressed on a unit BW basis showed a similar response with stage of maturity when compared with other experimental data.

A dynamic model of metabolizable energy utilization in growing and mature cattle. II. Metabolizable energy utilization for gain.

Component models were developed to predict the net efficiency of ME utilization for gain in cattle and to predict daily gain using recovered energy as the input. These models were integrated into a single model to predict daily gain from ME available for gain. One component model predicts the net efficiency of ME utilization for gain using constant partial net efficiencies of 0.2 and 0.75 for ME retention as protein and fat, respectively. This model predicts net efficiency of ME utilization for gain as a function of the ratio of the energy recovered in protein to the total energy recovered. The other component model predicts daily gain as a function of recovered energy and is represented by a system of ordinary differential equations that are numerically integrated on a daily basis. This model was developed by reformulating the equations in a published body composition model that uses daily gain to predict composition of gain since recovered energy is a function of gain and composition of gain. The equations in the two component models interact in that net efficiency is used to predict recovered energy from ME for gain, and in turn, recovered energy is used to predict gain in empty BW, which determines net efficiency through composition of gain. The numeric integration procedure provides an iterative solution for net efficiency. Simulated response of net efficiency for Hereford x Angus steers at 400 kg of empty BW decreased from 0.57 to 0.52 on diets with ME densities of 3.1 and 2.6 Mcal/kg of DM, and restricting the lower-quality diet to 75% of ad libitum intake resulted in a simulated net efficiency of 0.47. These responses in net efficiency were shown to be a result of composition of gain, with leaner gains resulting in lower net efficiencies.

A dynamic model of metabolizable energy utilization in growing and mature cattle. III. Model evaluation.

Component models of heat production identified in a proposed system of partitioning ME intake and a dynamic systems model that predicts gain in empty BW in cattle resulting from a known intake of ME were evaluated. Evaluations were done in four main areas: 1) net efficiency of ME utilization for gain, 2) relationship between recovered energy and ME intake, 3) predicting gain in empty BW from recovered energy, and 4) predicting gain in empty BW from ME intake. An analysis of published data showed that the net partial efficiencies of ME utilization for protein and fat gain were approximately 0.2 and 0.75, respectively, and that the net efficiency of ME utilization for gain could be estimated using these net partial efficiencies and the fraction of recovered energy that is contained in protein. Analyses of published sheep and cattle experimental data showed a significant linear relationship between recovered energy and ME intake, with no evidence for a nonlinear relationship. Growth and body composition of Hereford x Angus steers simulated from weaning to slaughter showed that over the finishing period, 20.8% of ME intake was recovered in gain. These results were similar to observed data and comparable to feedlot data of 26.5% for a shorter finishing period with a higher-quality diet. The component model to predict gain in empty BW from recovered energy was evaluated with growth and body composition data of five steer genotypes on two levels of nutrition. Linear regression of observed on predicted values for empty BW resulted in an intercept and slope that were not different (P < 0.05) from 0 and 1, respectively. Evaluations of the dynamic systems model to predict gain in empty BW using ME intake as the input showed close agreement between predicted and observed final empty BW for steers that were finished on high-energy diets, and the model accurately predicted growth patterns for Angus, Charolais, and Simmental reproducing females from 10 mo to 7 yr of age.

Body chemical composition and efficiency of energy and nutrient utilization by growing pre-ruminant Saanen goat kids

AbstractAn experiment involving a feeding trial and a comparative slaughter was conducted to assess the body chemical composition and patterns of nutrient utilization in pre-ruminant Saanen goat kids. Thirty male kids weighing about 6 kg were divided into five equal groups, one of which was slaughtered as the reference group (G0). The remainder were randomly assigned to four feeding levels of 250, 290, 330 and 370 g goats’ milk per kg M0·75 per day and named as groups GI, GII, GIII and GIV, respectively up to about 15 kg live weight, after which they were slaughtered. Mean milk consumption per unit live-weight gain (LWG) (kg/kg), and daily LWG (g/day), for GI, GII, GIII, GIV respectively were: 13·5 and 110; 10·5 and 160; 10·2 and 180; and 10·3 and 200. Empty body weight (EBW) as a proportion of final live weight was 0·95 in the reference animals, and ranged from 0·80 to 0·88 in the treatment groups. The dry matter (DM) concentration in the empty body of kids increased as their age advanced, from 277 g/kg EBW (G0) to between 308 and 326 g/kg EBW (GI to GIV). The protein and fat concentration of LWGs increased with the level of feeding from GI (142 g crude protein (CP) and 75·5 g fat per kg LWG) to GIV (155 g CP and 109 g fat per kg LWG). Regression of energy retention (ER) on metabolizable energy (ME) intake resulted in an efficiency of ME utilization for body retention (k) of 0·72(± 006). ME requirement for maintenance was estimated as 458 kJ/kg M0·75 per day. Efficiency of nitrogen (N) utilization for growth and N requirement for maintenance were estimated as 0·66(±011) and 0·47 g/kg M0·75 per day, respectively.

ENERGY EXPENDITURE AND ITS COMPONENTS IN FREE-LIVING ARABIAN BABBLERS (TURDOIDES SQUAMICEPS)

We determined the energy budget of the Arabian babbler (Turdoides squamiceps; Timaliidae), including the efficiency of energy use, using published data on resting metabolic rate (RMR), existence energy (EE), and field metabolic rate (FMR) of this desert passerine. Resting metabolic rate of the babblers was 0.65 kJ g-1 d-1 and EE was 1.10 kJ g-1 d-1. Therefore, RMR was approximately 59% of existence energy, and the efficiency of utilization of metabolizable energy for maintenance was 0.59. The heat increment of feeding (HIF) for maintenance for a diet of insects was 0.41, that is, 41% of the metabolizable energy consumed was used for food utilization. FMRs in summer and winter were similar and averaged 1.65 kJ g-1 d-1,breeding was 2.02 kJ g-1 d-1. The difference between either summer or winter FMR and EE in non-breeding babblers, 0.55 kJ g-1 d-1, was due to activity, mainly foraging, and may have included thermoregulatory costs in free-living birds. Breeding babblers required 0.37 kJ g-1 d-1 more than non-...

Energy Utilization of Growing Chicks in Various Nutritional Conditions

For the last two decades, energy utilization of growing chicks has been studied more and more. This paper focuses on the energy utilization estimated by the metabolizable energy (ME) values and the efficiency at which ME is used for growth of chicks under various nutritional environment. Degree of saturation of dietary fats is responsible for nitrogen-corrected apparent metabolizable energy (AMEn) of fats. The effect of dietary fat sources on heat production depends on the kind of unsaturated fatty acids as well as the degree of saturation. Medium chain triglyceride shows lower AME and net energy than long chain triglyceride. Phytase as feed additives increases the AME values of the diet along with improvement of the phosphorous utilization. Ostriches have higher ability to metabolize the energy of fiber-rich foodstuffs than fowls. Their higher ability seems to be associated with fermentation of fiber in the hindgut. Proportions of macronutrients in the diets have influenced not only the gain of body protein and energy but also the oxidative phosphorylation of the chicken liver. Essential amino acids deficiency reduces ME/GE (energy metabolizability) little, if any. Growing chicks respond to a deficiency of single essential amino acids with the reduction of energy retained as protein and increased energy retained as fat. Thus, energy retention is proportional to ME intake despite deficiency, and efficiency of ME utilization is not affected by deficiency of amino acids. Effect of oral administration of clenbuterol, a beta-adrenergic agonist, on the utilization of ME varies with the dose of the agents. Although the heat production related to eating behavior has been estimated less than 5% of ME, tube-feeding diets decreases HI by about 30%.

Milk Production, Nutrient Utilization, and Endocrine Responses to Increased Postruminal Lysine and Methionine Supply in Dairy Cows

The effect of increased postruminal supply of lysine and methionine was investigated in a production trial involving 64 dairy cows in early lactation. Within each of two basal rations, based on either corn silage or grass silage, rations were either naturally deficient in lysine or fortified with 24g of lysine in a rumen-protected form and naturally deficient in methionine or fortified with 12g of methionine in a rumen-protected form. The data were analyzed separately for the four lysine and the four methionine treatment groups. Milk production, body weight gain, and plasma concentrations of insulin-like growth factor-I, bovine somatotropin, insulin, glucose, nonesterified fatty acids, and urea were monitored over a 12-wk period. Supplementation with protected methionine led to increases in milk fat and protein contents of 2.4 and 1.8 g/kg of milk, respectively. Supplementation with protected lysine or methionine numerically increased protein yield comparable to values reported in the literature, but the treatment effects were not statistically significant. Efficiency of utilization of absorbed amino acids for milk protein synthesis and efficiency of utilization of metabolizable energy for milk production were not significantly altered in response to increased postruminal lysine and methionine flow, but a numerically increased efficiency of utilization of total amino acids was observed. No significant effect of lysine or methionine supplementation was observed on endocrine parameters nor on plasma metabolite concentrations. However, across treatment groups, high milk yield was correlated with low plasma insulin-like growth factor-I concentrations (r = −0.44) and partially with low plasma nonesterified fatty acids concentration and insulin levels (r = −0.26), while body weight gain was negatively correlated (r = −0.33) with elevated plasma bovine somatotropin concentrations.

The effect of dietary protein content and feeding level on the rate of protein deposition and energy utilization in growing Iberian pigs from 15 to 50 kg body weight.

The effects of dietary protein content and feeding level on the utilization of metabolizable energy (ME) and on the rates of gain, protein and fat deposition have been studied in seventy-two Iberian pigs growing from 15 to 50 kg body weight (BW) by means of comparative slaughter experiments. The animals were fed on six diets providing 223, 192, 175, 156, 129 and 101 g crude ideal protein ( CP)/kg DM and 14.64, 14.14, 14.37, 14.80, 15.36 and 15.53 MJ ME/kg DM respectively. Each diet was offered at three levels of feeding: 0.60, 0.80 and 0.95xad libitum intake. Protein deposition (PD) increased significantly (P<0.01) with each decrease in dietary CP content and reached a maximum value (74.0 g) when the diet providing 129 g CP/kg DM (6.86 g digestible ideal protein/MJ ME) was offered at the highest feeding level. This feeding regimen resulted in average values for live-weight gain and retained energy (RE) of 559 g/d and 10.9 MJ/d respectively. RE increased significantly (P<0.001) from 480 to 626 kJ/kg BW0.75 with each decrease in dietary CP content from 192 to 129 g/kg DM. Raising the level of feed intake led to significant linear increases in PD and RE irrespective of the diet fed (P<0.001). When diets approaching an adequate supply of CP were given, the net efficiency of use of ME for growth (kw) and the maintenance energy requirements were 58.2 % and 422 kJ/kg BW0.75 per d respectively.

The effect of dietary protein content and feeding level on the rate of protein deposition and energy utilization in growing Iberian pigs from 15 to 50kg body weight

The effects of dietary protein content and feeding level on the utilization of metabolizable energy (ME) and on the rates of gain, protein and fat deposition have been studied in seventy-two Iberian pigs growing from 15 to 50 kg body weight (BW) by means of comparative slaughter experiments. The animals were fed on six diets providing 223, 192, 175, 156, 129 and 101 g crude ideal protein (N×6·25; CP)/kg DM and 14·64, 14·14, 14·37, 14·80, 15·36 and 15·53 MJ ME/kg DM respectively. Each diet was offered at three levels of feeding: 0·60, 0·80 and 0·95×ad libitum intake. Protein deposition (PD) increased significantly (P&lt;0·01) with each decrease in dietary CP content and reached a maximum value (74·0 g) when the diet providing 129 g CP/kg DM (6·86 g digestible ideal protein/MJ ME) was offered at the highest feeding level. This feeding regimen resulted in average values for live-weight gain and retained energy (RE) of 559 g/d and 10·9 MJ/d respectively. RE increased significantly (P&lt;0·001) from 480 to 626 kJ/kg BW0·75 with each decrease in dietary CP content from 192 to 129 g/kg DM. Raising the level of feed intake led to significant linear increases in PD and RE irrespective of the diet fed (P&lt;0·001). When diets approaching an adequate supply of CP were given, the net efficiency of use of ME for growth (kw) and the maintenance energy requirements were 58·2 % and 422 kJ/kg BW0·75 per d respectively.

Energy metabolism of dairy cows fed on grass

Production performance of grass-fed dairy cows is often lower than expected from the estimated energy supply. To explain the overestimation of the energy content of grass for dairy cows, data from energy balance trials from three different laboratories (Wageningen, Lelystad and Hillsborough) were collected. The trials in Wageningen and Lelystad were carried out in the 1970s and those in Hillsborough in the 1990s. Regression analyses were carried out with the complete data set as well as per laboratory to identify differences per laboratory. Average net maintenance requirements per kg 3/4 (NE m) were 0.573 MJ, whereas the efficiency of metabolizable energy utilization for lactation ( k l) was 0.777. When NE m was fixed at the presently used value of 0.293 MJ/kg 3/4, k l was 0.60. Between-laboratory NE m varied between 0.294 (Lelystad) and 0.786 MJ/kg 3/4 (Hillsborough), whereas k l varied between 0.57 (Lelystad) and 0.84 (Hillsborough). For Wageningen and Hillsborough, NE m was high, whilst k l was also high. With the intercept fixed at 0.293 MJ/kg 3/4, efficiency varied between 0.53 (Hillsborough) and 0.62 (Wageningen). The k l and NE m are interrelated. Based on these data we surmise that the maintenance requirements for grass-fed dairy cows are 10% higher than presently assumed, with no change in k l.

Eficiência de utilização da energia metabolizável para mantença e ganho de peso e exigências de energia metabolizável e de nutrientes digestíveis totais de bovinos F1 Limousin x Nelore não-castrados

Foram utilizados 50 novilhos F1 Limousin x Nelore inteiros, alocados em dez tratamentos, com cinco níveis de concentrado (25; 37,5; 50; 62,5; e 75%) e duas formas de balanceamento protéico da dieta (uma isoprotéica com 12% de proteína bruta [PB] e outra variando proteína com energia). O consumo de matéria seca (MS) necessário para manter o equilíbrio de energia foi calculado dividindo-se o consumo de energia metabolizável (EM) necessário para mantença (112,89 kcal/PCVZ0,75), pela concentração de EM (kcal/kg de MS) da dieta, em cada tratamento. A concentração de energia líquida (EL) para mantença de cada ração foi obtida dividindo-se a produção de calor em jejum, 76,36 kcal/kgPCVZ0,75, pelo consumo de MS para manter o equilíbrio de energia, expresso em g de MS/kg PCVZ0,75. A concentração de EL para ganho foi calculada dividindo-se a energia retida por dia, em kcal/kg PCVZ0,75, pelo consumo de MS acima das necessidades de mantença, expresso em g MS/kg PCVZ0,75. As eficiências de utilização da EM para mantença (k m) e ganho de peso (k f) foram estimadas a partir da relação entre os teores de energia líquida, para mantença ou ganho, respectivamente, em função da EM da dieta, e a k f também foi estimada como o coeficiente de regressão linear entre a energia retida e o consumo de EM, juntamente com os dados relativos aos animais designados de mantença. A eficiência de utilização da EM para mantença foi calculada em 0,68 e a eficiência de utilização da EM para ganho, em 0,52; 0,50; 0,55; 0,60; e 0,50, respectivamente, para as dietas com 1,93; 2,09; 2,28; 2,42; e 2,70 Mcal de EM/kg de MS, obtidas para os níveis de 25; 37,5; 50; 62,5; e 75% de concentrado. As exigências de EM, ED e NDT para mantença, calculadas, foram 112,3 e 137,0 kcal/kg PCVZ0,75 e 31,1 g/kg PCVZ0,75, respectivamente.

Effect of Concentrate Crude Protein Level on Grass Silage Intake, Milk Yield and Nutrient Utilisation by Dairy Cows in Early Lactation

Twenty-one multiparous dairy cows were fed concentrates containing three levels (119, 154 and 191g/kg DM) of crude protein (CP) during the first ten weeks of lactation. Part of the grain and molassed sugar beat pulp was substituted with 0% (RSM0), 15% (RSM15) or 30% (RSM30) rapeseed meal. Wilted grass silage was fed ad libitum after calving. The average response between RSM0 and RSM15 was +1.66kg milk/d per percentage unit change in concentrate CP content. No further response occurred between RSM15 and RSM30. The positive effect of RSM inclusion was seen throughout the experimental period and was associated with increased plasma non esterified fatty acids (NEFA) and decreased plasma insulin concentration one week after calving, and higher efficiency of metabolisable energy utilisation for milk production. Digestibility of the diet remained unaffected. Milk and plasma urea tended to increase with RSM30 indicating excessive supply of rumen degradable protein. Because of the limited potential of cows to compensate for a deficit in feed protein supply by mobilising tissue protein, a substantial milk yield response can be achieved with a moderate level of protein supplementation during early lactation.

Leaf content of straw diets influences supplementation responses by sheep

Young sheep were offered separated barley straw fractions consisting predominantly of either leaf or stem components, either without or with one of the three supplements. Supplements consisted of urea and sodium sulfate (N/S), cereal grain mixed with urea and sodium sulfate (Bar/N) or fishmeal (FM) as a protein meal expected to provide digestible rumen-undegraded protein (DUP). Voluntary intake of stem-rich straw was only 29.7 g/kg W 0.75 per day. Although intake of this stem-rich straw was not changed ( P>0.05) by provision of any supplement, estimated metabolizable energy (ME) intake was increased up to 70% due to increases in diet digestibility and total DM intake. When no supplements were provided the voluntary intake of leaf-rich straw was similar to that of stem-rich straw. N/S and FM supplements increased intake of leaf-rich straw and of estimated ME by up to 112%, while Bar/N supplement did not change straw intake and increased estimated ME intake by 74%. All supplements increased ( P<0.05, P<0.01 or P<0.001) liveweight (LW) change, feed conversion efficiency (FCE), nitrogen (N) retention and wool growth. However, the responses to the N/S and FM supplements were much greater with the leaf-rich than the stem-rich straw. LW change and wool growth was increased more by the FM supplement than could be attributed to the increased ME intake, suggesting an increase in the efficiency of utilization of ME when this supplement was provided. In conclusion, the experiment demonstrated that responses to supplements by young sheep offered cereal straw are dependent on the morphological composition of the straw.

Effects of concentrates with different contents of protected fat rich in PUFAs on the performance of lactating Granadina goats: 1. Feed intake, nutrient digestibility, N and energy utilisation for milk production

The purpose of this study was to determine whether the use of different levels of a protected fat rich in polyunsaturated fatty acids (PUFAs) in the concentrate fraction of diets for lactating goats has any effects on feed intake, nutrient digestibility, N and energy utilisation for milk production. Three groups of six Granadina goats in the middle of their second lactation were used. They were fed diets of forage (50%) and concentrate (50%). The concentrate fraction contained either 0, 9 or 12% added fat. The added fat was protected against rumen metabolism and was particularly rich in PUFAs. The total feed intakes and the forage and concentrate intakes were determined for each case as were the digestibility of nutrients and the N and energy utilisation for milk production. A tendency to decrease total feed intake as the fat level increased was observed. The concentrate fraction intake and the DM digestibility for fat addition in the concentrate at 12% was lower ( p<0.05) than that for the basal diet. Organic matter and energy digestibilities were lower ( p<0.05) for fat addition in the concentrate at 12% than those for fat addition at 9% and for the basal diet. However, fat addition in the concentrate at 9 and 12% or only at 12%, brought about an increase ( p<0.05) in fat digestibility or ADF digestibility, respectively. The ratio between N output in the milk and N ingested or N available for production for fat addition in the concentrate at 9% was higher ( p<0.05) than that for the basal diet. Finally, the ratio between energy output in the milk and metabolisable energy available for production for fat addition in the concentrate at 12%, tended to be higher than those for fat addition in the concentrate at 9% and for the basal diet. From these results, it is concluded that the use in the concentrate fraction of diets for lactating goats of the protected fat here considered, gives rise to a good digestive utilisation of the diet together with improved N and metabolisable energy utilisation for milk production.

Effects of a Nonforage Diet on Milk Production, Energy, and Nitrogen Metabolism in Dairy Goats throughout Lactation

The objective of the experiment was to compare a silage-based control diet (C) with a nonforage diet (NF) in dairy goats throughout lactation in terms of animal performance and energy utilization. Eight Saanen goats were divided into two groups and fed C or NF, a commercial blend that included sunflower meal, cassava, coconut meal, and whole cottonseeds as the main ingredients that was characterized by a small particle size and a high crude protein content. In early, mid, and late lactation (44, 100, and 219 days in milk) the goats were individually tested for dry matter intake (DMI), digestibility, milk yield and composition, milk renneting properties, rumen and plasma parameters, and nitrogen and energy utilization (open circuit respiration chambers). During early and mid lactation, the NF fed goats had a very high DMI: 2946 and 2915 g/ d, respectively. Nevertheless, milk yield was similar for the two treatments: 4369 vs. 4342 and 3882 vs. 3841 g/d for goats fed diets C and NF during the first and second periods, respectively. Milk fat content was not statistically different between the two diets. The protein content and rheological parameters of milk were similar for the two diets. Nonprotein nitrogen and urea levels in milk of goats fed NF were significantly higher than goats fed C. Ruminal ammonia and plasma urea nitrogen were also significantly increased by diet NF, due to its high protein content. Plasma glucose, ßbeta;-hydroxybutyrate, and nonesterified fatty acids and ruminal volatile fatty acids were not influenced by dietary treatment. Dietary NF significantly decreased energy digestibility (74.5 vs. 65.8%, on average for the lactation, for C and NF, respectively) and had a significantly lower metabolizability (metabolizable energy/intake energy; 66.6 vs 58.0%, on average); however, the efficiency of utilization of metabolizable energy was unaffected by the diet. In conclusion, goats were fed a nonforage diet during the entire lactation without detrimental effect on their health and productive performance.