Use Of Metabolizable Energy Research Articles

Maintenance Energy Requirement of Broilers and the Impact of Ambient Temperatures

Eight broiler weight groups, housed in metabolic chambers, were exposed to 3-5 ambient temperatures (AT) such that AT exposure fell below, near and above the projected thermoneutral (TN) zone. Birds were fed 0, 5, and 10% of body weight (W), or allowed to consume food ad libitum, to vary energy consumption. Energy needs for body weight homeostasis, efficiency of metabolizable energy (ME) use for maintenance and the exponent needed to convert live body weight to metabolic weight was estimated. Energy (Kcal W-1 d-1) and oxygen (l W-1 d-1) needs for body weight homeostasis declined curvilinearly as body weight increased from 0.042 kg to 2.44 kg. Such needs were impacted by AT. The efficiency of ME use to support maintenance energy need varied in a cubic fashion with bird mass. The estimated zone of thermoneutrality, at body weight homeostasis, was inversely related to W (kg), expressed as: TN (ºC) = 31.896 – 0.4625∙W (R2 = 0.99). Under metabolic basal rate (MBR) conditions, the TN zone was curvilinearly related to weight as: TNMBR = 32.6466 − (94.4603∙W) − (0.7660∙W2) (R2 = 0.99). The exponent, to linearize live body weight with heat production (HP) of birds fed to W homeostasis, was determined to be 0.758 with all birds strictly housed at TN. Further, the exponent to linearize HP of birds under MBR (fasted) conditions was estimated to be 0.679. Equations relating chick energy and oxygen consumption need with body weight and AT, metabolizable energy for gain homeostasis (MEmg), metabolizable energy for retained energy homeostasis (MEmr), metabolizable energy for protein homeostasis (MEmp), and metabolizable energy for fat homeostasis (MEmf) are presented.

Determination of maintenance energy requirement and responses of dry ewes to dietary inclusion of lucerne versus concentrate meal

An accurate value for metabolizable energy (ME) requirement for maintenance (MEm) is essential to enable sheep husbandry practice to reach its potential. The objectives of the study were to use calorimetry chamber data of dry ewes (Hu × thin-tail Han F1 crossbred) to develop updated MEm, examine effects of substituting concentrate feed with lucerne hay on energy partitioning, and explore the relationships between energy utilization and fasting heat production (FHP). Data were collected from three experiments. In Exps. 1, 2a and 2b, lucerne hay was used to replace concentrates in three levels (0:40%, 15:25% and 30:10%), with diets containing 60% maize stover (Exp. 1), fresh rye forage (Exp. 2a) or dry rye forage (Exp. 2b). Within each experiment, diets were isoenergetic (digestible energy, DE) and isonitrogenous. Exp. 3 aimed at evaluating effects of three BW levels on nutrient utilization of dry ewes offered diets containing 60% maize stover, 15% lucerne hay and 25% concentrates. Energy metabolism data were measured using the respiration calorimeter chamber technique in all three experiments, followed by the measurement of FHP in Exps. 1, 2b and 3. The MEm derived from the linear regression between energy balance (EB) and ME intake was 0.440 MJ/kg BW0.75. The average FHP was 0.326 MJ/kg BW0.75. The fasting metabolism, net energy requirement for maintenance (NEm) and MEm were estimated to be 0.336, 0.359 and 0.511 MJ/kg BW0.75, respectively, through adjustment of FHP using fasting urinary energy output, activity allowance and efficiency of ME use for maintenance. The FHP was negatively correlated to EB/metabolic BW, ME/gross energy (GE), ME/DE, EB/GE intake and EB/ME intake, while positively correlated to HP/GE intake, HP/ME intake and CH4-E/GE intake. Compared to zero lucerne hay diet, the 15% lucerne hay intake decreased HP (MJ/d), and had no negative effects on EB (MJ/d) or energy utilization efficiencies. The results indicate that nutrient requirement standards currently used across the world are likely to underestimate MEm for dry ewes, and the selection of low FHP ewes for breeding has the potential to improve sheep production efficiency.

351 Awardee Talk: How retained energy and protein affects the determination of energy and protein requirements for growth

Abstract The understanding of how nutrition influences the body composition of growing animals has fascinated researchers for centuries. It involves the expertise of scientists with different areas of knowledge, encompassing the composition of the diet and its nutritive value to the fermentation and digestion of substrates to the absorption and metabolism of nutrients, and finally, to the deposition of fat, protein, and minerals in body tissues. The comparative slaughter technique is the preferred method to assess the body composition of growing and finishing animals. However, the methodological procedures are labor-intensive, expensive, and time-consuming, facilitating the incidence of errors and inconsistencies of the measurements that are collected, including the initial animal’s body composition. First, retained fat and protein (RP) are used to compute retained energy (RE). Then, RP and RE are used to compute protein and energy requirements for growth. Heat production, calculated from the metabolizable energy (ME) intake for animals at maintenance, is used to compute maintenance requirements. Three areas of concern exist for this approach: 1) the efficiencies of possible mobilization of fat and protein tissues during the feeding period are unaccounted for, especially for the animals fed near the maintenance level of intake; 2) the correlation between observed and predicted RP when using predicted RE is higher than when using observed RE (0.939 vs. 0.679); and 3) the disconnection when predicting partial efficiency of use of ME for growth using the proportion of RE deposited as protein — carcass approach — versus using the concentration of ME of the diet — diet approach. These concerns raised questions about the interdependency between predicted RP and RE and the existence of internal offsetting errors that may prevent overall adequacy in predicting energy and protein requirements of beef cattle.

Phosphorus digestibility and metabolisable energy concentrations of contemporary wheat, barley, rye and triticale genotypes fed to growing pigs

ABSTRACT This study was conducted to determine apparent total tract digestibility (ATTD) of phosphorus (P) and metabolisable energy (ME) concentrations for pigs of 32 different genotypes (n = 8 per grain species) of barley, rye, triticale and wheat. All genotypes were grown at the same location under the same field conditions and were fed to growing castrated crossbred pigs (initial body weight: 31.1 ± 6.95 kg) using a series of duplicate 3 × 3 Latin square designs. A basal ration, which was deficient in P, and 32 experimental rations containing 400 g/kg DM of the basal ration and 600 g/kg DM of the corresponding cereal grain were mixed. Pigs were kept in metabolism crates and the total collection method was used for separate faeces and urine collections with 7-d adaptation and 7-d collection periods. The mean ATTD of P was greater (p < 0.05) for wheat than for triticale, rye or barley (59.4%, 50.4%, 44.9% and 44.4%, respectively, for the mean of each grain species). Within-grain species differences (p < 0.05) among genotypes were obtained for ATTD of P of barley and triticale. The concentrations of ME of triticale and wheat were higher (p < 0.05) than that of barley and rye (16.1 and 16.2 vs. 14.9 and 14.8 MJ ME/kg DM, respectively). Differences in ME concentration among genotypes within a grain species (p < 0.05) were found for barley, triticale and wheat. No differences were found for rye. Compared to literature data the present study showed, in part, considerable differences in ATTD of P and ME concentration. These results should be taken into account for accurate pig ration formulation with regard to minimised P output and efficient use of ME. No significant relationships were detected between ATTD of P and phytic acid concentration or phytase activity in the grain genotypes in this study.

Between-cow variation in the components of feed efficiency

A meta-analysis based on an individual-cow data set was conducted to investigate between-cow variations in the components and measurements of feed efficiency (FE) and to explore the associations among these components. Data were taken from 31 chamber studies, consisting of a total of 841 cow/period observations. The experimental diets were based on grass or corn silages, fresh grass, or a mixture of fresh grass and straw, with cereal grains or by-products as energy supplements, and soybean or canola meal as protein supplements. The average forage-to-concentrate ratio across all diets on a dry matter basis was 56:44. Variance component and repeatability estimates of FE measurements and components were determined using diet, period, and cow within experiment as random effects in mixed procedures of SAS (SAS Institute Inc., Cary, NC). The between-cow coefficient of variation (CV) in gross energy intake (GE; CV = 0.10) and milk energy (El) output as a proportion of GE (El/GE; CV = 0.084) were the largest among all component traits. Similarly, the highest repeatability estimates (≥0.50) were observed for these 2 components. However, the between-cow CV in digestibility (DE/GE), metabolizability [metabolizable energy (ME)/GE], methane yield (CH4E/GE), proportional urinary energy output (UE/GE), and heat production (HP/GE), as well as the efficiency of ME use for lactation (kl), were rather small. The least repeatable component of FE was UE/GE. For FE measurements, the between-cow CV in residual energy-corrected milk (RECM) was larger than for residual feed intake (RFI), suggesting a greater possibility for genetic gain in RECM than in RFI. A high DE/GE was associated with increased CH4E/GE (r = 0.24), HP/GE (r = 0.12), ME/GE (r = 0. 91), energy balance as a proportion of GE (EB/GE; r = 0.35), and kl (r = 0.10). However, no correlation between DE/GE and GE intake or UE/GE was observed. Increased proportional milk energy adjusted to zero energy balance (El(0)/GE) was associated with increases in DE/GE, ME/GE, EB/GE, and kl but decreases in UE/GE, CH4E/GE, and HP/GE, with no effect on GE intake. In conclusion, several mechanisms are involved in the observed differences in FE among dairy cows, and reducing CH4E yield (CH4E/GE) may inadvertently result in reduced GE digestibility. However, the selection of dairy cows with improved energy utilization efficiencies offers an effective approach to lower enteric CH4 emissions.

Effects of diet forage proportion on maintenance energy requirement and the efficiency of metabolizable energy use for lactation by lactating dairy cows

The objective of the present study was to examine the effect of dietary forage proportion (FP) on metabolizable energy (ME) requirement for maintenance (MEm) and the efficiency of ME use for lactation (kl) in lactating dairy cows. Data used were derived from 32 calorimetric chamber experiments undertaken at our institute between 1992 and 2010, including data from 818 Holstein-Friesian cows (HF), 50 Norwegian Red cows, and 62 crossbred cows (Jersey × HF or Norwegian Red × HF). Animals were offered forage-only rations (n=66) or forage and concentrate rations (n=864) with FP ranging from 18 to 100% (dry matter basis). The effect of FP was evaluated by dividing the whole data set into 4 groups according to the FP ranges, categorized as FP <30%, FP=30 to 59%, FP=60 to 99%, and FP=100%. The MEm for individual cows was calculated from heat production minus energy losses from inefficiencies of ME use for lactation, energy retention and pregnancy, and kl was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. Increasing FP significantly reduced ME intake and milk energy output, although the differences between the 2 low FP groups were not significant. However, increasing FP significantly increased the ratio of heat production over ME intake and MEm (MJ/kg0.75), with the exception that the increases did not reach significance in heat production/ME intake between FP <30% and FP=30 to 59%, or in MEm between FP=60 to 99% and FP=100%. However, the FP had no significant effect on the kl values, which were similar among the 4 groups of cows. The effect of FP was also evaluated using the linear mixed regression technique relating El(0) to ME intake. The results demonstrated that with a common regression coefficient (slope), the regression constants (intercepts) taken as net energy requirement for maintenance significantly increased with increasing FP. However, the increase between the 2 high FP groups did not research significance. It is concluded that increasing diet FP had no effects on kl but significantly increased maintenance energy requirement (MJ/kg0.75). These results indicate that using the current energy feeding systems to ration dairy cows managed under low input systems may underestimate their nutrient requirements, because the majority of feeding systems adopted globally do not differentiate the maintenance energy requirements between low and high forage input systems.

Energy Value of Cassava Products in Broiler Chicken Diets with or without Enzyme Supplementation.

This study investigated the metabolizable energy (ME) intake, net energy of production (NEp), heat production (HP), efficiencies of ME use for energy, lipid and protein retention as well as the performance of broiler chickens fed diets based on cassava chips or pellets with or without supplementation with an enzyme product containing xylanase, amylase, protease and phytase. The two products, cassava chips and pellets, were analysed for nutrient composition prior to feed formulation. The cassava chips and pellets contained 2.2% and 2.1% crude protein; 1.2% and 1.5% crude fat; and 75.1% and 67.8% starch, respectively. Lysine and methionine were 0.077%, 0.075%, and 0.017%, 0.020% protein material, respectively, while calculated ME was 12.6 and 11.7 MJ/kg, respectively. Feed intake to day 21 was lower (p<0.01) on the diet containing cassava chips compared to diets with cassava pellets. Enzyme supplementation increased (p<0.01) feed intake on all diets. Live weight at day 21 was significantly (p<0.01) reduced on the diet based on cassava chips compared to pellets, but an improvement (p<0.01) was noticed with the enzyme supplementation. Metabolizable energy intake was reduced (p<0.01) by both cassava chips and pellets, but was increased (p<0.01) on all diets by enzyme supplementation. The NEp was higher (p<0.01) in the maize-based diets than the diets containing cassava. Enzyme supplementation improved (p<0.01) NEp in all the diets. Heat production was highest (p<0.01) on diets containing cassava pellets than on cassava chips. It is possible to use cassava pellets in diets for broiler chickens at a level close to 50% of the diet to reduce cost of production, and the nutritive value of such diets can be improved through supplementation of enzyme products containing carbohydrases, protease, and phytase.

Effects of increasing rates of molasses supplementation and forage quality on the productivity of steers

This study consisted of several experiments that investigated the feed intakes, and growth rates of steers fed low-quality Angleton grass (Dichanthium aristatum) supplemented with urea and sulfur (dry matter (DM) digestibility, 45%) and medium-quality Rhodes grass (Chloris gayana) (DM digestibility, 58%) when fed either alone or with molasses mixtures (MM, molasses plus nitrogen and phosphorus). Some digestion characteristics of the basal forage diets were also measured. Addition of MM at 1.2 times calculated maintenance energy requirements (M) was associated with about a four-fold increase in microbial crude protein production and a 42% decrease in neutral detergent fibre digestibility. In the first growth experiment, MM at 0M, 0.45M, 0.90M and 1.35M was offered and mostly consumed before forage was offered ad libitum. The initial mean weight of the steers was 240 kg. Consumed MM comprised 0%, 21%, 38% and 50% of the total DM intake for Angleton grass and 0%, 19%, 33% and 41% for Rhodes grass. The corresponding mean liveweight (LW) gains were 0.06, 0.31, 0.73 and 0.83 kg/day for steers fed Angleton grass and 0.61, 0.90, 1.02 and 1.13 kg/day for steers fed Rhodes grass. In a second experiment, MM was offered to steers (initially 370 kg) at the same time as forage. Offered MM comprised 0, 0.40, 0.80 and 1.20M of the calculated metabolisable energy (ME) requirements for maintenance. Consumed MM comprised 0%, 20%, 36% and 48% of the total DM intake for Angleton grass diets and 0%, 18%, 28% and 32% for Rhodes grass diets. The corresponding mean LW gains were –0.09, 0.36, 0.58 and 0.70 kg/day for Angleton grass diets and 0.63, 0.67, 0.80 and 0.94 kg/day for Rhodes grass diets. The method of presentation of the MM had only minor effects on the amounts and proportions of forage and the MM consumed and on the LW gains of the steers, expressed as g/kg0.75 LW per day to allow for differences in initial LW between experiments. Using modifications to the scheme of SCA (1990) to predict maintenance energy requirements, a value for efficiency of use of ME for growth was calculated from growth rates of steers fed Rhodes grass. When MM with an assumed content of 11 MJ ME/ kg DM was added to the forage diets, the calculated ME content of forage decreased with increased MM content, consistent with depression of fibre digestion. The relationships for the separate experiments indicated that at 50% MM in the diet, the magnitudes of the depression in the calculated ME content of the forages were 20–37% for Rhodes grass and 18–33% for Angleton grass.

Comparison of maintenance energy requirement and energetic efficiency between lactating Holstein-Friesian and other groups of dairy cows

The objectives of the present study were to investigate the effects of cow group on energy expenditure and utilization efficiency. Data used were collated from 32 calorimetric chamber experiments undertaken from 1992 to 2010, with 823 observations from lactating Holstein-Friesian (HF) cows and 112 observations from other groups of lactating cows including Norwegian (n=50), Jersey × HF (n=46), and Norwegian × HF (n=16) cows. The metabolizable energy (ME) requirement for maintenance (MEm) for individual cows was calculated from heat production (HP) minus energy losses from inefficiencies of ME use for lactation, energy retention, and pregnancy. The efficiency of ME use for lactation (kl) was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. The effects of cow groups were first evaluated using Norwegian cows against HF crossbred cows (F1 hybrid, Jersey × HF and Norwegian × HF). The results indicated no significant difference between the 2 groups in terms of energy digestibility, ratio of ME intake over gross energy intake, MEm (MJ per kg of metabolic body weight, MJ/kg0.75), or kl. Consequently, their data were combined (categorized as non-HF cows) and used to compare with those of HF cows. Again, we detected no significant difference in energy digestibility, ratio of ME intake over gross energy intake, MEm (MJ/kg0.75), or kl between non-HF and HF cows. The effects were further evaluated using linear regression to examine whether any significant differences existed between HF and non-HF cows in terms of relationships between ME intake and energetic parameters. With a common constant, no significant difference was observed between the 2 groups of cows in coefficients in each set of relationships between ME intake (MJ/kg0.75) and MEm (MJ/kg0.75), El(0) (MJ/kg0.75), HP (MJ/kg0.75), MEm:ME intake, El(0):ME intake, or HP:ME intake. However, MEm values (MJ/kg0.75) were positively related to ME intake (MJ/kg0.75), irrespective of cow group. We concluded, therefore, that cow groups evaluated in the present study had no significant effects on energy expenditure or energetic efficiency. However, the maintenance energy requirement (MJ/kg0.75) was not constant (as adopted in the majority of energy rationing systems across the world) but increased with increasing feed intake.

Protein and energy requirements of castrated male Saanen goats

A comparative slaughter trial was conducted to determine the energy and protein requirements for growth of castrated male Saanen goats weighing from 20 to 35kg body weight (BW). Regarding maintenance requirements, 36 castrated male Saanen goats with an initial BW of 20.7±0.5kg, and aged 3.3±0.6 months, were used. Nine animals were randomly chosen and slaughtered at the beginning of the experimental phase (BW of 21.0±0.4kg), representing the baseline (BL) group. The 27 remaining castrated male goats were pair-fed into nine groups (blocks) of three animals each, fed either ad libitum or restricted to 30 or 60% of ad libitum intake. A group was slaughtered when the animal fed ad libitum reached 35kg BW. Regarding requirements for gain, 27 castrated male Saanen goats were fed ad libitum and nine were slaughtered at 21.0±0.4kg BW, nine at 27.7±0.5kg BW and nine at 35.1±0.3kg BW. The BL and ad libitum-fed animals used to determine maintenance requirements were also used to estimate gain requirements. The net energy (NE) requirement for maintenance was 261.5kJ/kg0.75 BW. The metabolizable energy (ME) requirement for maintenance was 404.2kJ/kg0.75 BW; therefore, the partial efficiency of use of ME for NE was 0.65. The minimal endogenous N losses were 262±48.4mgN/kg0.75 empty BW (EBW), corresponding to a net protein requirement for maintenance of 1.39±0.257g/kg0.75 BW. The net energy for gain increased by approximately 40% (from 12 to 17MJ/kg EBW gain) and the net protein for gain slightly decreased by 3% (from 166 to 160g/kg EBW gain) as the BW increased from 20 to 35kg. Our study contributes to the improvement of goat nutrition because it provides estimates of the protein and energy requirements of castrated male Saanen goats.

Energy partitioning and substrate oxidation by Guirra ewes fed soy hulls and corn gluten feed blend as a replacement for barley grain

The aim of this experiment was to study the effect of substituting barley grain by soy hulls and corn gluten feed blend on energy partitioning, substrate oxidation, carbon and nitrogen balance in sheep. The experiment was conducted in a crossover design with 12 dry and non-pregnant adult Guirra ewes (57.5±1.9kg of BW) in each group, and sheep were fed two dairy treatments in two 27 d periods. The ewes were fed with two different mixed diets; one group was fed a mixed diet with 365g/kg of dry matter (DM) of barley grain (BRL diet) and the other diet (SHGF diet) replaced barley with soy hulls (271g/kgDM) and gluten feed (93g/kgDM). Six sheep per group were used to determine apparent total tract digestibility (10 d adaptation plus 5 digestibility and balance of nutrients), gas exchange (12d), oxidation of nutrients and carbon and nitrogen balance. The average values of metabolisable energy (ME) intake, heat production (HP) and retention of energy (RE) were 498, 436 and 62kJ/kg 0.75 of body weight (BW), respectively, with no differences between diets. The estimated value of ME for maintenance was 391kJ/kg 0.75 BW. The efficiency of use of ME for maintenance (km) was 0.64 and the nutritive value of the diets was 7.6MJ of net energy/kg DM, on average. Most of the HP derived from oxidation of fat (0.48) for the fibrous diet, and from oxidation of carbohydrates (0.63) for the starchy diet, with no differences in total tissue energy recovered (67kJ/kg 0.75 BW). This fibrous by-product was utilised by the ewes with no detrimental effect on energy metabolism and resulted in a similar positive energy balance to that of a traditional cereal based diet. The economic advantages and sustainability of this choice should be evaluated.

Metabolisable energy requirements for maintenance and gain of liveweight of Bali cattle (Bos javanicus)

A series of liveweight gain (LWG), feed and water intake and digestibility experiments were conducted across eastern Indonesia. Thirty-six datasets of LWG, feed and water intake, and diet characteristics were used to determine the nutritional requirements of growing Bali cattle fed a wide range of diets that varied in crude protein content and apparent dry matter digestibility. Regression of average daily LWG against estimated metabolisable energy (ME) intake was conducted, and the ME requirements for maintenance of liveweight (LW, 0 kg/day) and LWG were determined. It was estimated that the ME required to maintain LW of this class of Bali cattle, across the range of diets evaluated, was 0.47 MJ ME/kg LW0.75.day and that 34 MJ ME was required for each kg LWG, or 29 g LWG/MJ ME. The relationship between estimated ME intake and LWG was not affected by the crude protein content of the diet. The data demonstrate that ME requirements for maintenance of LW of Bali cattle are comparable with values for other cattle species, but that this class of Bali cattle is generally less efficient in the use of ME for LWG across the range of diets evaluated.

Feedlot performance, feed efficiency reranking, carcass traits, body composition, energy requirements, meat quality and calpain system activity in Nellore steers with low and high residual feed intake

The aim was to evaluate growth, carcass traits, feed efficiency reranking, body composition, calpain system activity and meat quality in Nellore steers that were phenotypically ranked for high and low residual feed intake (RFI). Seventy-two Nellore steers (16–21 month-old, 334±19kg BW) had free access to a feedlot diet for 70d (feeding period 1, P1). Daily dry matter intake (DMI), body weight gain (ADG) and ultrasound carcass traits were measured individually. The 12 lowest and the 12 highest RFI steers were classed as low- and high-RFI groups and were fed for a second feeding period (feeding period 2, P2). Spearman's rank correlation was performed for RFI and gain-to-feed ratio (G:F) measured over P1 and P2. The carcass traits, meat quality and calpain system activity were evaluated at slaughter, and body composition was determined. In P1, low-RFI steers had greater G:F (0.159 vs. 0.134; P<0.001), lower DMI (9.30 vs. 11.1kg/d; P<0.0001), lower RFI (−0.80 vs. 0.85kg/d; P<0.0001), and tended to have lower rates of rump fat gain (4.48 vs. 6.05mm; P=0.06), but no differences were observed for ADG, BW, and other traits measured by ultrasound (P>0.05). In P2, no differences between RFI classes were observed for G:F and DMI as a percentage of BW (P>0.05), and small differences were observed for DMI (8.25 vs. 8.99kg/d, P<0.05) and RFI (−0.28 vs. +0.29kg/d, P=0.06). The ranking correlations for RFI and G:F measured consecutively in P1 and P2 were low to moderate (r=0.11–0.40). Low-RFI steers had lower requirements of metabolizable energy (ME) for maintenance (131 vs. 160Mcal/kg EBW0.75d−1, P<0.05), but no differences were observed for fat and protein gain, retained energy and efficiency of ME use for gain (P>0.05). No differences between low- and high-RFI steers were observed for carcass traits at slaughter; however, low-RFI steers had 8.1kg less gastrointestinal fat than high-RFI steers. There were no RFI effects on meat shear force and the activities of μ-calpain, m-calpain and calpastatin (P>0.05). High-RFI steers had greater MFI in 1d aged LM (53.9 vs. 40.8, P<0.05). The variation in feed efficiency between high- and low-RFI Nellore steers is related to differences in energy requirements and deposition of fat on internal organs. The ranking for feed efficiency is altered as cattle become older. The selection for improved RFI in Nellore cattle may reduce feed requirements for beef production without affecting meat tenderness and enzymatic activity of the calpain system.

Milk production and energy efficiency of Holstein and Jersey-Holstein crossbred dairy cows offered diets containing grass silage

Eight Holstein and 8 Jersey-Holstein crossbred dairy cows (all primiparous) were used in a repeated 2 (genotype) × 2 (concentrate level) factorial design study involving a total of 4 periods (each of 6-wk duration), designed to examine the effect of cross-breeding on the efficiency of milk production and energy use. The 4 periods began at 5, 11, 27, and 33 wk of lactation, respectively. Animals were offered a completely mixed diet containing grass silage and concentrates, with the level of concentrate in the diet either 30 or 70% of dry matter (DM). During the final 10 d of each period, ration digestibility and energy use was measured, the latter in indirect open-circuit respiration calorimeters. No significant interaction existed between cow genotype and dietary concentrate level for feed intake, milk production, or any of the energy use parameters measured. Across the 2 genotypes, total DM intake, milk yield, and milk protein and lactose concentrations increased with increasing dietary concentrate level. Thus, cows offered the high-concentrate diet had a higher gross energy (GE) intake, and a higher energy output in feces, urine, milk as heat, and a higher metabolizable energy (ME) intake as a proportion of GE intake and as a proportion of digestible energy intake. Across the 2 levels of concentrates, the Jersey-Holstein cows had a significantly higher total DM intake and body condition score, and produced milk with higher fat, protein, and energy concentrations, compared with those of the Holstein cows. In addition, the Jersey-Holstein cows had a significantly higher GE intake and energy output in urine, methane, and milk. However, crossbreeding had no significant effect on energy digestibility or metabolizability, energy partitioning between milk and body tissue, or the efficiency of ME use for lactation. Relating ME intake to milk energy output and heat production indicated that crossbreeding did not influence ME requirement for maintenance or energy efficiencies. The energy metabolism data were also used to compare energy efficiencies between “early” (data pooled for the first 2 periods) and “late” (data pooled for the second 2 periods) stages of lactation. Stage of lactation had no effect on energy digestibility or metabolizability, whereas increasing stage of lactation increased the rate of energy partitioning into body tissue and reduced the rate of energy partitioning into milk, irrespective of cow genotype. In conclusion, crossbreeding of Holstein dams with Jersey sires had no adverse effects on the overall production efficiency of Holstein dairy cows in terms of milk production, efficiency of ME use for lactation, and energy partitioning between milk and body tissue.

Effects of stage of lactation and dietary concentrate level on energy utilization by Alpine dairy goats

Twenty-four lactating and 13 nonlactating Alpine goats were used to determine effects of stage of lactation and dietary concentrate level on energy utilization. Diets comprising 60 or 20% concentrate (60%C and 20%C, respectively) were consumed ad libitum by lactating animals and at a level of intake near maintenance by nonlactating animals. Measurement periods were d 25 to 31 (early), 87 to 94 (mid), and 176 to 183 (late) of lactation. Eleven observations were made in early and mid lactation for each diet, and 8 and 7 were made in late lactation for the 60%C and 20%C diets, respectively. Efficiency of metabolizable energy (ME) use for maintenance (66.9, 71.4, and 61.1% for early, mid, and late lactation, respectively) and the maintenance ME requirement (479, 449, and 521 kJ/kg of BW0.75 for early, mid, and late lactation, respectively) determined with nonlactating animals differed among stages of lactation. The efficiency of ME use for maintenance was similar between diets, but the maintenance requirement tended to be greater for the 60%C than for the 20%C diet (504 vs. 463 kJ/kg of BW0.75). The latter difference may have involved greater ME intake for the 60%C diet, resulting in a slightly greater difference between ME intake and total heat energy for the 60%C compared with the 20%C diet (11 vs. −8 kJ/kg of BW0.75). Intake of ME by lactating goats was greater for the 60%C than for the 20%C diet (18.6 vs. 16.3 MJ/d). Recovered energy in lactation from mobilized tissue tended to be greater for the 60%C than for the 20%C diet (8.44 vs. 6.55 MJ/d) and differed among stages of lactation (2.60, 1.59, and 1.13 MJ/d in early, mid, and late lactation, respectively). Recovered energy in tissue gain was similar among stages of lactation and between diets and was not different from 0. Efficiency of use of dietary ME for lactation differed among stages of lactation (59.5, 51.9, and 65.4% for early, mid, and late lactation, respectively) and tended to be greater for the 60%C than for the 20%C diet (64.2 vs. 54.9%). The efficiency of use of dietary ME for maintenance and lactation was similar among stages of lactation and was greater for the 60%C compared with the 20%C diet (64.3 vs. 60.9%). Predicted milk yield from National Research Council requirements was reasonably accurate. In conclusion, using data of nonlactating goats to study energy utilization for maintenance in lactation has limitations. Efficiency of energy use by lactating dairy goats consuming diets high in concentrate appears greater than that by goats consuming diets low in concentrate. Despite differences in nutrient requirement expressions, observations of this study support National Research Council recommendations of energy requirements of lactating dairy goats.

Effects of stage of lactation and level of feed intake on energy utilization by Alpine dairy goats

Thirty-six lactating Alpine does were used to determine effects of stage of lactation and level of feed intake on energy utilization. Twelve does were assigned to measurement periods in early, mid, and late lactation (wk 5, 13, and 27, respectively). For 6 does of each group, after ad libitum consumption of a 60% concentrate diet, feed intake was restricted to near the metabolizable energy (ME) requirement for maintenance (MEm) for 8 d followed by fasting for 4 d. For other does, fasting immediately followed ad libitum consumption. Intake of ME was similar among stages of lactation with ad libitum intake (22.1, 22.1, and 19.8kJ/d in early, mid, and late lactation, respectively). The efficiency of ME use for maintenance determined with does fed near MEm averaged 81%. Fasting heat energy was greater for ad libitum consumption than for near MEm consumption [368 vs. 326kJ/kg of body weight (BW)0.75] and was numerically lowest among stages in late lactation with near MEm intake (334, 350, and 295kJ/kg of BW0.75 in early, mid, and late lactation, respectively) and ad libitum consumption (386, 384, and 333kJ/kg of BW0.75 in early, mid, and late lactation, respectively). The efficiency of use of dietary ME for lactation was greater for consumption near MEm than for consumption ad libitum (67.9 vs. 58.6%) and with ad libitum consumption tended to decrease with advancing stage of lactation (63.9, 57.3, and 54.5% for early, mid, and late lactation, respectively). Estimated MEm was greater for ad libitum intake than for near MEm intake and was lowest during late lactation (429, 432, and 358kJ/kg of BW0.75 for near MEm intake and 494, 471, and 399kJ/kg of BW0.75 for ad libitum intake in early, mid, and late lactation, respectively). However, because of increasing BW as the experiment progressed, MEm (MJ/d) was similar among stages of lactation with both levels of intake. The efficiency of ME use for maintenance and lactation was similar among stages of lactation and greater with near MEm intake than ad libitum intake (77.1 vs. 67.7%). In conclusion, the MEm requirement (kJ/kg of BW0.75) of does in late lactation was less than in early and mid lactation. A marked effect of restricted feed intake subsequent to ad libitum consumption on estimates of efficiency of energy use for maintenance and lactation was observed compared with use of nonlactating animals. Level of feed intake can have substantial effect on estimates of energy utilization by lactating dairy goats.

Mitigation of enteric methane emissions through improving efficiency of energy utilization and productivity in lactating dairy cows

The data set used in the present study was obtained from 20 energy metabolism studies involving 579 lactating dairy cows (511 Holstein-Friesian, 36 Norwegian Red, and 32 Jersey-Holstein crossbreds) varying in genetic merit, lactation number, stage of lactation, and live weight. These cows were offered diets based on grass silage (n=550) or fresh grass (n=29), and their energy intake and outputs, including methane energy (CH4-E), were measured in indirect open-circuit respiration calorimeter chambers. The objective was to use these data to evaluate relationships between CH4-E output and a range of factors in animal production and energetic efficiency in lactating dairy cows under normal feeding regimens. The CH4-E as a proportion of milk energy output (El), El adjusted to zero energy balance (El(0)), or intakes of gross energy (GE), digestible energy (DE), or metabolizable energy (ME) was significantly related to a wide range of variables associated with milk production (El and El(0)) and energy parameters (energy intake, metabolizability, partitioning, and utilization efficiencies). Three sets of linear relationships were developed with experimental effects removed. The CH4-E/GE intake (r2=0.50–0.62) and CH4-E/El (r2=0.41–0.68) were reduced with increasing feeding level, El/metabolic body weight (MBW; kg0.75), El(0)/MBW, GE intake/MBW, DE intake/MBW, and ME intake/MBW. Increasing dietary ME/DE decreased CH4-E/El (r2=0.46) and CH4-E/GE intake (r2=0.72). Dietary ME concentration and ME/GE were also negatively related to CH4-E/GE intake (r2=0.47). However, increasing heat production/ME intake increased CH4-E as a proportion of El (r2=0.41), El(0) (r2=0.67) and energy intake (GE, DE, and ME; r2=0.62 and 0.70). These proportional CH4-E variables were reduced with increasing ratios of El/ME intake and El(0)/ME intake and efficiency of ME use for lactation (r2=0.49–0.70). Fitting CH4-E/El or CH4-E/El(0) against these energetic efficiencies in quadratic rather than linear relationships significantly increased r2 values (0.49–0.67 vs. 0.59–0.87). In conclusion, CH4-E as a proportion of energy intake (GE, DE, and ME) and milk production (El and El(0)) can be reduced by increasing milk yield and energetic efficiency of milk production or by reducing energy expenditure for maintenance. The selection of dairy cows with high energy utilization efficiencies and milk productivity offers an effective approach to reducing enteric CH4 emission rates.

Effects of the dietary protein content and the feeding level on protein and energy metabolism in Iberian pigs growing from 50 to 100 kg body weight

Nutritional requirements of the Iberian pig, a slow-growing, obese porcine breed, are not well defined and seem to differ from those of conventional or high-performing pigs. The effects of the dietary protein content and the feeding level on the utilisation of metabolisable energy (ME) and the rates of gain, protein, and fat deposition were studied with 81 Iberian castrates growing from 50 to 100 kg body weight (BW) by using the comparative slaughter technique. The animals were fed 4 diets providing 145, 120, 95, and 70 g ideal crude protein (CP) per kg dry matter (DM), and containing 13.94, 14.29, 14.56, and 14.83 MJ ME per kg DM, respectively. Three levels of feeding were evaluated: 0.60, 0.80, and 0.95 × ad libitum intake. Growth rate increased (linear and quadratic, P < 0.001) as the dietary ideal CP content decreased. It also increased with the feeding level (linear, P < 0.001; quadratic, P < 0.05). Gain:feed and gain:ME intake improved by decreasing the ideal CP content in the diet (linear, P < 0.001 and P < 0.05, respectively; quadratic P < 0.001 for both variables). Increasing the feeding level improved linearly gain:feed and gain:ME intake ( P < 0.001). Protein deposition (PD):ME intake ranged between 1.23 and 1.44 g/MJ, and it showed a tendency to reach the maximum value when the diet providing 95 g ideal CP per kg DM was fed (quadratic, P = 0.078). When this diet was offered at 0.95 × ad libitum, PD reached a maximum value of 71 g/day. This dietary treatment resulted in average values for average daily gain and retained energy (RE) of 854 g/day and 21.4 MJ/day, respectively. The average rate of gain was 19.93 g/MJ increase in ME intake, equivalent to an energy cost of 50.2 kJ ME per g gain, irrespective of the dietary ideal CP content. Also, the overall marginal efficiency of protein deposition (ΔPD:ΔME; g/MJ) was 1.34. Increasing the feeding level led to increases in PD (linear, P < 0.001) and RE (linear, P < 0.001; quadratic, P < 0.01) irrespective of the dietary ideal CP concentrations. Between 50 and 100 kg BW, the chemical composition of 1 kg gain averaged 78, 592, 28.7, and 284 g for CP, fat, ash, and water respectively. The net efficiency of use of ME for growth ( kg) and the maintenance energy requirements were 0.606 and 396 kJ/kg BW 0.75 per day, respectively. The results support earlier findings that the genotype has marked effects on protein and energy metabolism of growing pigs and underline important compositional differences of the Iberian pig compared with conventional or modern porcine genotypes.

Effects of Dairy Cow Genotype with Two Planes of Nutrition on Energy Partitioning Between Milk and Body Tissue

The data used in the present study were derived from a 2 (genotype) × 2 (plane of nutrition) factorial design production study using Holstein-Friesian (n = 32) and Norwegian (n = 32) first-lactation dairy cattle offered grass silage-based diets from 1 to 44 wk of lactation. The high nutrition diet had concentrate inclusions (g/kg of dry matter) of 600, 500, and 400 for lactation days of <101, 101 to 200, and >200, respectively, and the low nutrition diet included concentrates at 300, 200, and 100 for the same periods. Dietary metabolizable energy (ME) concentrations were measured in calorimetric chambers at lactation d 80, 160, and 240 respectively, and then applied to production data to calculate ME intake. From wk 1 to 44 of lactation, Holstein-Friesian cows had a consistently lower accumulated live weight gain and body condition score, and a consistently higher ME intake and milk energy output than Norwegian cows, irrespective of the plane of nutrition. Compared with Norwegian cows using mean data derived from the 2 planes of nutrition, Holstein-Friesian cows produced a significantly higher proportion of milk energy output over ME intake in early and mid lactation, although this increase was not significant in late lactation. In contrast, Holstein-Friesian cows partitioned a significantly lower proportion of ME intake into body tissue than Norwegian cows in early lactation, although the differences were not significant in mid or late lactation. When ME intake and energy used for maintenance, milk, and body tissue were taken into account, the efficiency of ME use for lactation was similar between the 2 genotypes offered the high or low concentrate diet during the whole lactation. It is concluded that Holstein-Friesian cows can produce more milk energy than Norwegian cows, mainly as a result of higher ME intake and because of a greater ability to partition more energy into milk and less into body tissue. The effect on energy partitioning mainly occurs in early and midlactation and is particularly evident with high concentrate diets.

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.