Estimation of energy needs in the free-ranging goat with particular reference to the assessment of its energy expenditure by the 13C-bicarbonate method

Quantifying energy expenditure in Göttingen Minipigs with the 13C-bicarbonate method under basal and drug-treated conditions

Effective treatments of obesity focusing on energy expenditure (EE) are needed. To evaluate future EE-modulating drug candidates, appropriate animal models and methods to assess EE are needed. This study aimed to evaluate the stable isotope 13C-bicarbonate method (13C-BM) for estimating EE in Göttingen minipigs under basal and drug-treated conditions. Four experiments (Expt.1-4) were conducted to assess: 1) the 13C-BM reproducibility using breath sample collection (n = 8), on two consecutive days, 2) the effect of two dose levels (5 and 10 mg/kg body weight (BW)) of the mitochondrial uncoupler dinitrophenol (DNP) in a crossover design (n = 8), 3) sampling method agreement; blood vs. exhaled air (n = 6) and 4) 13C-BM using constant isotope infusion compared with indirect calorimetry (IC) (n = 3). Results correlated significantly (p < 0.001) between days (Expt.1), with an average coefficient of variance of 5.4 ± 2.3%. Administration of 10 mg DNP/kg BW increased (p < 0.01) EE by 33.2 ± 6.4% (Expt.2). Results based on different sampling methods correlated significantly (p < 0.001) and EE increased after 10 mg DNP/kg BW (p < 0.05) in Expt.3. However, results based on blood sampling were significantly higher (p < 0.01) than those of exhaled air. No effect of DNP and significantly different EE results (p < 0.05) was observed in a limited number of animals, when constant isotope infusion and blood sampling was compared with IC (Expt.4). In conclusion, the 13C-BM is useful for investigating treatment effects on EE in minipigs. However, further validation under standardized conditions is needed to provide accurate estimates of the 13C recovery factor and respiratory quotient, both of decisive importance when using the 13C-BM.

Seasonal dynamics of cattle grazing behaviors on contrasting landforms of a fenced ranch in northern China

The number of livestock per unit area is commonly used as a proxy of grazing pressure in both experimental studies and grassland management. However, this practice ignores the impact of landform heterogeneity on the spatial distribution of grazing pressure, leading to localized patches of degraded grassland. The spatial distribution of actual grazing density thus needs to be examined. Owing to the corresponding changes in resource availability and energy consumption as livestock move across an elevation gradient, we predict that livestock will preferentially use low-land and that different temporal patterns of grazing pressure will occur in the contrasting landforms. GPS location data and a machine learning technique were used to identify the seasonal pattern and the factors driving grazing pressure on a fenced ranch. Over both low-land and sand-dune landforms, the proportion of time that livestock spent on foraging increased from 63% in July to 67% in August and 69% in September, and non-foraging behavior decreased correspondingly. In low-land, the log-transformed average foraging density significantly increased from 0.61 (i.e., total foraging behaviors in 5 days measured at 50-s intervals per 10 × 10 m grid) in July to 0.66 in August and 0.88 in September, whereas there was no significant change on sand-dunes. From July to September, the relative area of low-land foraged by cattle accounted for 31%, 35%, and 36%, respectively, and in sand-dunes the proportions increased from 45% to 47% to 51%. In low-land, the foraging density was negatively correlated with biomass (P = .07), total digestible nutrients (P < .05), and crude protein (P = .06) and positively correlated with acid detergent fiber (P < .05), whereas no such relationships were observed in sand-dunes. Our results indicate that topographic features should be considered when managing livestock, especially during periods with adverse conditions of herbage quality and quantity.

Macropods, feral goats, sheep and cattle: 1. Equivalency in how much they eat

The extent to which goats and cattle eat equivalent amounts of forage as sheep has been based on their maintenance energy requirements (MERs) relative to a 50kg wether or dry ewe, known as a dry sheep equivalent (DSE). As such, a 50kg goat was considered 1 DSE and a 450kg steer as 7–8 DSE. In comparison, the DSE of macropods has been based on their basal metabolic rate (BMR) or energy expenditure of grazing (EEg) relative to those of sheep, with a 50kg macropod thought to be 0.7 and 0.45 DSE respectively. Based on published energy requirements of goats, macropods and cattle relative to sheep, their DSE values are estimated to be 1.2, 1.0 and 7.6 respectively. However, relative energy requirements may not be the same as relative dry matter intakes (DMIs), due to differences in forage quality, the structure of digestive tracts and selective foraging capabilities. Allometric equations that predict DMI were developed from published liveweights and intakes of sheep, goats, macropods and cattle. Given DMIs when fed high-quality forage, a 50kg goat was 1 DSE, a 50kg macropod was 0.7 DSE and a 450kg steer was 7.6 DSE. Their DMIs were depressed by 35–50% when fed low-quality forage, but a goat remained as 1 DSE, macropods increased to 1.0 DSE and cattle increased to 8.3 DSE. The capacity of macropods to maintain relatively higher DMIs of low-quality forage than sheep is probably due of their faster digesta passage rates and more expandable stomachs. These DMIs of animals provided ad-libitum quantities of similar forages in small pens are likely to differ from their DMIs when selectively grazing heterogeneous rangeland pastures. Under these conditions, sheep select higher-quality diets than cattle, and kangaroos select higher-quality diets than sheep, which increase the relative DMIs of the smaller herbivores. For this reason, a 50kg macropod is likely to be 1 DSE and consume twice as much forage than previously assumed.

Effect of lemon leaves on energy and C-N balances, methane emission, and milk performance in Murciano-Granadina dairy goats

The objective of this experiment was to find out the effect of lemon leaves on energy and C-N balances, methane emission, and milk performance in dairy goats. Lemon leaves were used to replace alfalfa as forage in a diet for Murciano-Granadina goats. Ten Murciano-Granadina dairy goats (44.1 ± 4.47 kg of BW) in late lactation (185 ± 7.2 d) were selected in a crossover design experiment, where each goat received 2 treatments in 2 periods. One group was fed a mixed ration with 450 g of pelleted alfalfa per kilogram of DM (ALF diet) and, the other group replaced alfalfa with 450 g of pelleted lemon leaves per kilogram DM (LEM diet). The concentrate was pelleted, being the same for the two groups (forage to concentrate ratio was 45/55). The goats were allocated to individual metabolism cages. After 14 d of adaptation, feed intake, total fecal and urine output, and milk yield were recorded daily over a 5-d period. Then, gas exchange measurements were recorded individually by an open-circuit indirect calorimetry system using a head box. Higher dietary lipids in LEM diet reduced DMI (200 g/d) and energy intake (251 kJ/kg of BW0.75), although no differences between treatments were observed for ME intake (998 kJ/kg of BW0.75, on average) and oxidation of nutrients (64% and 25% for carbohydrates and fat oxidation, respectively, on heat production from oxidation basis). Greater (P < 0.05) milk fat values for C18:2n6t and CLA 9c11t + 9t11c were found in LEM compared with ALF diet. Goats fed LEM diet produced significantly fewer CH4 emissions than ALF diet (18%). Likewise, the use of lemon leaves as forage reduced the amount of CH4 in 2.7 g/kg of milk. Results suggest that lemon leaves are effective in reducing CH4 emission without detrimental effect on milk yield.

Effect of rice bran as a replacement for oat grain in energy and nitrogen balance, methane emissions, and milk performance of Murciano-Granadina goats

The objective of this experiment was to study the effects of substituting oat grain with rice bran on energy, nitrogen and carbon balance, methane emissions, and milk performance in dairy goats. Ten Murciano-Granadina dairy goats in late lactation (46.1 ± 3.07 kg) were assigned to 2 treatments in a crossover design, where each goat received both treatments in 2 periods. One group of 5 goats was fed a mixed ration with 379 g of oat grain/kg of dry matter (O diet) and the other group of 5 goats was fed a diet that replaced oat grain with 379 g/kg dry matter of rice bran (RB diet). Diets were formulated to be isoenergetic and isoproteic, so bypass fat was added to reach the same amount of energy in both diets. The goats were allocated to individual metabolism cages. After 14 d of adaptation, feed intake, total fecal and urine outputs, and milk yield were recorded daily over a 5-d period. Then, gas exchange measurements were recorded individually by a mobile open-circuit indirect calorimetry system using a head box. Dry matter intake was different for both diets [1.83 ± 0.11 vs. 1.61 ± 0.08 (means ± SD), for O and RB, respectively]. Metabolizable energy intake and heat production were not significantly different between diets, with average values of 1,254 [standard error of the mean (SEM) = 110.0] and 640 (SEM = 21.0) kJ/kg of BW(0.75), respectively. Significant differences were found in milk fat content (5.3 and 6.9%, SEM = 0.36; for O and RB, respectively) and milk fatty acids: medium-chain fatty acids (17.17 vs. 12.90 g/100g, SEM = 0.969; for O and RB, respectively) and monounsaturated fatty acids (20.63 vs. 28.29 g/100g, SEM = 1.973; for O and RB, respectively). Enteric CH4 emission was lower for the RB diet (23.2 vs. 30.1g/d, SEM = 2.14; for O and RB, respectively), probably because of the higher lipid content in RB diets than O diets (11.7 vs. 4.1%, respectively). Lactating goats utilized RB without detrimental effects on energy metabolism. Higher milk fat and lower CH4 emissions were observed with the RB diet compared with the O diet.

Application of overall dynamic body acceleration as a proxy for estimating the energy expenditure of grazing farm animals: relationship with heart rate

Estimating the energy expenditure of farm animals at pasture is important for efficient animal management. In recent years, an alternative technique for estimating energy expenditure by measuring body acceleration has been widely performed in wildlife and human studies, but the availability of the technique in farm animals has not yet been examined. In the present study, we tested the potential use of an acceleration index, overall dynamic body acceleration (ODBA), as a new proxy for estimating the energy expenditure of grazing farm animals (cattle, goats and sheep) at pasture with the simultaneous evaluation of a conventional proxy, heart rate. Body accelerations in three axes and heart rate for cows (n = 8, two breeds), goats (n = 6) and sheep (n = 5) were recorded, and the effect of ODBA calculated from the body accelerations on heart rate was analyzed. In addition, the effects of the two other activity indices, the number of steps and vectorial dynamic body acceleration (VeDBA), on heart rate were also investigated. The results of the comparison among three activity indices indicated that ODBA was the best predictor for heart rate. Although the relationship between ODBA and heart rate was different between the groups of species and breeds and between individuals (P<0.01), the difference could be explained by different body weights; a common equation could be established by correcting the body weights (M: kg): heart rate (beats/min) = 147.263∙M^-0.141 + 889.640∙M^-0.179∙ODBA (g). Combining this equation with the previously reported energy expenditure per heartbeat, we estimated the energy expenditure of the tested animals, and the results indicated that ODBA is a good proxy for estimating the energy expenditure of grazing farm animals across species and breeds. The utility and simplicity of the procedure with acceleration loggers could make the accelerometry technique a worthwhile option in field research and commercial farm use.

Effect of replacing dietary corn with beet pulp on energy partitioning, substrate oxidation and methane production in lactating dairy goats

The objective of this experiment was to study the effect of substitution of corn by beet pulp on energy partitioning, substrate oxidation, nitrogen and carbon balance and milk performance in dairy goats during late lactation. Twelve multiparous lactating Murciano-Granadina goats were fed two diets. Six goats were fed a mixed ration with 310 g/kg DM of ground corn (diet CORN) and in the other diet the corn was substituted with 302 g/kg DM of beet pulp (diet BP) in a cross-over design. No significant differences between diets were observed for milk production (1.36 kg/day, on average) and differences were found for milk fat (5.39 and 4.21% for BP and CORN, respectively). The metabolisable energy intake was higher (P < 0.05) in the CORN diet than BP (1320 vs 1044 kJ/kg0.75 BW, respectively). The difference in methane emissions between treatments was significant (P < 0.05) with values of 92 vs 61 kJ/kg0.75 BW for BP and CORN, respectively, indicating that greater levels of starch in diet reduce methane production. Replacing corn with BP reduced significantly the energy body fat deposition (300 vs 44 kJ/kg0.75 BW for CORN and BP diets, respectively). This reduction in energy retention for the BP diet did not compromise milk yield and milk energy output.

Use of dry citrus pulp or soybean hulls as a replacement for corn grain in energy and nitrogen partitioning, methane emissions, and milk performance in lactating Murciano-Granadina goats

The aim of this study was to assess the effect of substitution of dietary corn grain by dry citrus pulp or soybean hulls on energy and nitrogen partitioning, substrate oxidation, methane emission, and milk performance in dairy goats during midlactation. Twelve multiparous Murciano-Granadina goats of similar body weight (41.7 ± 2.8 kg) were split in 3 groups in an incomplete crossover design. One group of 4 goats was fed a mixed ration with 605 g/kg of dry matter of corn grain (CRG), another group replaced corn grain with dry citrus pulp (CTP), and the last with soybean hulls (SYH). The goats were allocated to individual metabolism cages. After 14 d of adaptation, feed intake, total fecal and urine output, and milk yield were recorded daily over a 5-d period. Then, gas exchange measurements were recorded by a mobile open-circuit indirect calorimetry system using a head box. Dry matter intake was similar for all 3 groups (1.53 kg/d, on average). Total replacement of the concentrate with fibrous by-products increased fiber apparent digestibility. The metabolizable energy intake was significantly greater for diet CRG than SYH (1,193 vs. 1,079 kJ/kg of BW⁰·⁷⁵, respectively), CTP showed an intermediate value. The heat production was higher for the fiber diet than starchy diet (908 vs. 843 kJ/kg of BW⁰·⁷⁵ for SYH and CRG, respectively). The efficiency of use of metabolizable energy for milk production obtained by regression was 0.59. Goats fed CTP and SYH diets produced similar CH₄ emissions (34.8 g/d, on average), significantly higher compared with goats fed the CRG diet (24.7 g/d). Goats of the 3 treatments were in negative energy balance, so the oxidation of fat was greater than for carbohydrates. No significant differences were observed for milk production (1.72 kg/d), and milk fat was significantly greater for a more fibrous diet compared with a starchy diet (6.57 vs. 4.95% in SYH and CRG, respectively).

Energy partitioning and substrate oxidation by Murciano-Granadina goats during mid lactation fed soy hulls and corn gluten feed blend as a replacement for corn grain

The aim of this experiment was to study the effect of substituting corn grain by soy hulls and corn gluten feed blend on energy partitioning, substrate oxidation, and milk performance in dairy goats during mid lactation. Ten multiparous Murciano-Granadina goats in mid lactation were fed 2 isoenergetic and isoproteic diets [19.08MJ/kg of dry matter (DM) and 18.7% of CP, DM basis] in a crossover design. One group of 5 goats was fed a mixed ration with 373g of corn grain/kg of DM (CRN diet) and the other diet replaced corn grain with 373g/kg DM of fibrous by-products [soy hulls and gluten feed (SHGF) diet]: 227g of soy hulls/kg of DM and 146g of gluten feed blend/kg DM. Fat was added to the SHGF diet to make it isoenergetic. After 10d of adaptation, the feed intake, refusal, total fecal and urine output, and milk yield were recorded daily over a 5-d period. Then, gas exchange measurements were recorded by a mobile open-circuit respirometry system using a head box for 10d. Dry matter intake was similar for both diets (2.07kg/d, on average). Greater and significant values were found in the SHGF diet for ammonia N, energy in urine, and oxidation of protein. Values were significantly lower for heat production of fermentation, indicating a decrease in rumen fermentation with this diet, probably due to an excess of crude protein in the diet and lack of synchronization of the nonfiber carbohydrates with rumen-degraded protein. The metabolizable energy intake was no different between CRN and SHGF treatments, with an average value of 1,444kJ/kg of BW(0.75). Due to the positive energy balance during mid lactation in this trial, most of the heat production from oxidation of nutrients derived from carbohydrate oxidation (55%, on average), followed by oxidation of fat (29%, on average). No significant differences were observed for milk production, although milk fat was significantly greater for the SHGF diet than the CRN diet (7.0 vs. 5.4%, respectively). Despite the different starch levels and fibrous content used in these mixed diets, no significant differences for the efficiency of use of metabolizable energy for late lactation were observed (0.63, on average). An average nutritive value of 7.52MJ of net energy of lactation/kg of DM was obtained. This fibrous by-product was utilized by lactating goats without detrimental effect on energy metabolism and resulted in similar performance to grain bases diet. The economic advantages and sustainability of this choice should be evaluated.

Energy and water use by invasive goats (Capra hircus) in an Australian rangeland, and a caution against using broad-scale allometry to predict species-specific requirements

Feral goats (Capra hircus) are ubiquitous across much of Australia's arid and semi-arid rangelands, where they compete with domestic stock, contribute to grazing pressure on fragile ecosystems, and have been implicated in the decline of several native marsupial herbivores. Understanding the success of feral goats in Australia may provide insights into management strategies for this and other invasive herbivores. It has been suggested that frugal use of energy and water contributes to the success of feral goats in Australia, but data on the energy and water use of free-ranging animals are lacking. We measured the field metabolic rate and water turnover rate of pregnant and non-pregnant feral goats in an Australian rangeland during late summer (dry season). Field metabolic rate of pregnant goats (601 ± 37 kJ kg(-0.73)d(-1)) was 1.3 times that of non-pregnant goats (456 ± 24 kJ kg(-0.73)d(-1)). The water turnover rate of pregnant goats (228 ± 18 mL kg(-0.79)d(-1)) was also 1.3 times that of non-pregnant goats (173 ± 18 kg(-0.79)d(-1)), but the difference was not significant (P=0.07). There was no significant difference in estimated dry matter digestibility between pregnant and non-pregnant goats (mean ca. 58%), blood or urine osmolality, or urine electrolyte concentrations, indicating they were probably eating similar diets and were able to maintain osmohomeostasis. Overall, the metabolic and hygric physiology of non-pregnant goats conformed statistically to the predictions for non-marine, non-reproductive placental mammals according to both conventional and phylogenetically independent analyses. That was despite the field metabolic rate and estimated dry matter intake of non-pregnant goats being only 60% of the predicted level. We suggest that general allometric analyses predict the range of adaptive possibilities for mammals, but that specific adaptations, as present in goats, result in ecologically significant departures from the average allometric curve. In the case of goats in the arid Australian rangelands, predictions from the allometric regression would overestimate their grazing pressure by about 40% with implications for the predicted impact on their local ecology.

Evaluation of the oral ¹³C-bicarbonate tracer technique for the estimation of CO₂ production and energy expenditure in dogs during rest and physical activity

For feeding of working dogs during their daily life, illness, routine jobs or sporting activities, an accurate determination of their nutritional requirements is essential to ensure their optimal health and performance. To predict the appropriate guidelines about how to feed dogs, it appears essential to determine the energy expenditure (EE) in a reliable and feasible way. In the present experiment, the non-invasive oral ¹³C-bicarbonate tracer technique (o¹³CT), i.e. collection of breath samples after oral administration of NaH¹³CO₃, was used for the estimation of CO₂ production and EE in dogs. Measurements were conducted during two days of rest, and during three days with 3 h of exercise per day. Average EE was 483 and 876 kJ kg⁻⁰·⁷⁵ d⁻¹ during rest and exercise, respectively. The o¹³CT seems appropriate to use as a minimal restrictive and non-invasive method to obtain reliable estimates of EE in dogs at different activity levels under near natural conditions.

Energy expenditure, urea kinetics, and body weight gain within a segregating resource family population

Beef and dairy cattle represent divergent metabolic types that disseminate nutrients into either meat or milk and differ in nutrient accretion. To investigate nutrient flow and turnover in an animal model combining beef and dairy cattle, a crossbred experiment has been started. An F(2) resource population was generated from Charolais (beef breed) sires and German Holstein (dairy breed) cows as P(0) founders by consistent use of embryo transfer to establish the F(1) and F(2) generations, which accordingly comprised half- and full-sib offspring. In 64 bulls of 5F(2) families, dry matter intake and growth performance were measured monthly, and carcass composition was determined after slaughtering at 18 mo of age. Energy expenditure and urea kinetics were investigated via stable isotope tracer techniques using an intravenous single bolus dose of sodium [(13)C]bicarbonate [2.5 μmol/kg of body weight (BW), 99 atom% (13)C] at 8 and 18 mo of age and of [(15)N]urea (0.28 mg/kg of BW, 99 atom% (15)N) at 8 mo of age, respectively. Insulin responses were measured via glucose tolerances tests at the age of 8 mo. The results revealed significant differences between families for growth performance, energy expenditure, and urea kinetics. In summary, low energy expenditure was associated with high average body mass gain and high insulin response. A greater urea loss was associated with reduced muscle protein in carcass. In addition, corresponding half-sib and full-sib sisters from bulls with highest growth rate indicated highest milk production. In conclusion, we have demonstrated that differences in energy expenditure and urea kinetics result in differences in average daily gain and carcass traits and vice versa in F(2) crossbred bulls with common beef and dairy genetic backgrounds.