Physiological responses of mature Quarter Horses to reining training when fed conventional and fat-supplemented diets

An initial experiment (Experiment I) was conducted utilizing five mature Quarter Horses to establish baseline physiological responses to typical reining training. In an initial standardized exercise test (SET) which simulated reining horse maneuvers, heart rate and plasma lactate concentration indicated that galloping circles, spinning and stopping were anaerobic maneuvers (203 beats/min and 8.86 mmol/L, respectively). However, lactate concentrations declined before the end of the SET. The values were used to modify the SET to a degree of difficulty that would elicit significant anaerobiosis, thus maintaining elevated lactate concentrations throughout the SET.In a subsequent experiment (Experiment II), ten mature Quarter Horses were exercised by reining horse training in a crossover experiment. Horses were fed a control (C) and a 10% fat-supplemented (F) concentrate with bermuda grass hay in a 65:35 ratio. Heart rate (HR), respiration rate (RR), rectal temperature (RT) and venous blood samples were taken prior to, during and following recovery from a modified SET which simulated reining horse maneuvers but was more demanding than the previous SET. Heart rates and plasma lactate concentrations indicated that all maneuvers, except loping circles elicited anaerobiosis (208 beats/min and 11.8 mmol/L, respectively; peak values on d 0). Plasma glucose concentration fell while loping circles from resting concentrations of 104.3 mg/dl to 79.2 mg/dl increased throughout the remainder of the SET to 89.7 mg/dl and returned to resting concentrations by 30 min of recovery. Respiration rate, packed cell volume (PCV), rectal temperature and total serum non-esterified fatty acid concentration (NEFA) increased throughout the SET and peaked between the end of exercise and after 10 min of recovery (128 breaths/min; 51%; 39.9°C and .871 mEq/L, respectively).Diet composition had no consistent effects on physiological responses, but there were training effects. Heart rate and plasma lactate were lower on day 28 than on day 0 (P<.05) while plasma glucose, NEFA and PCV were not affected by training. Respiration rate and rectal temperature reflected ambient conditions.     

Digestible energy requirements of Mexican donkeys fed oat straw and maize stover

The limited availability of food, together with the constraints that traditional management systems impose on the natural foraging behaviour of donkeys, often results in severe under-nutrition. Few studies have been conducted into the digestibility of different forages and little information exists on nutritional requirements of donkeys. In order to measure digestible energy requirements of donkeys under tropical conditions, an experiment was carried out at the Centre for Research in Agricultural Science (CICA) and the Faculty of Veterinary Medicine of the Universidad Aut6noma del Estado de México located in the Toluca valley, Central Mexico. Thirty-two donkeys of a body condition typical for Central Mexico were divided into four groups of 8 animals each according to their sex and live weight: group 1 (G1) comprised male donkeys below the average body weight (102+/-5 kg); group 2 (G2) comprised male donkeys of average body weight (121.5+/-4 kg); group 3 (G3) comprised female donkeys below average weight (111.8 +/- 5 kg); and group 4 (G4) comprised female donkeys of average weight (127.6 +/- 5 kg). A diet of oat straw or maize stover and 15% alfalfa hay was offered to meet exact maintenance requirements. The donkeys were monitored for 13 months. The live weight of all animals was recorded daily in order to monitor whether maintenance requirements were being met. Mean daily digestible energy (DE) requirements were measured during the winter, spring, summer and autumn of 2003-2004. Digestible energy requirements of all four sex and liveweight groups were significantly (p > 0.05) higher during the spring than during the other seasons of the year (13.5, 18.0, 10.4 and 14.3 MJ DE per day during winter, spring, summer and autumn, respectively). Predicted DE requirements of donkeys with a live weight range betweenn 90 and 150 kg using the data from the present study were less than those predicted using scaled-down horse feeding standards.     

Energy utilization and blood traits of ponies fed fat-supplemented diets

The digestibility and heat production values for three fats of different origin were determined. Four pony geldings (225 kg) were used in a study consisting of four successive digestion trials utilizing a 4 X 4 Latin square design. The four dietary treatments were basal alone and supplemented with 15% corn oil, blended fat or inedible tallow. The blended fat was composed of a mixture of animal and vegetable fats. A 7-d preliminary period preceded a 7-d total fecal collection period for each trial. Heat production values were obtained by indirect calorimetry and calculated from oxygen consumption data. Fat supplementation increased (P less than .05) dietary metabolizable energy from a basal value of 3,224 kcal.kg intake-1.d-1 to a mean value of 3,984 kcal.kg intake-1.d-1 for the three fat diets. No difference in heat production was observed among the diets, averaging 2,883 kcal.kg intake-1.d-1. Fats increased (P less than .05) the energy balance (metabolizable energy-heat production) approximately 88% over the basal. Corn oil and blended fat produced the greatest energy balance of the fats. Utilization of energy in fats, calculated by difference, was not different, but tended to be highest in blended fat and lowest in the corn oil. Apparent fatty acid digestibility increased (P less than .05) with the addition of fat to the basal, partially due to the dilution of endogenous fecal fat, but digestion coefficients were not different (P greater than .40) among the high fat diets.     

Changes in lipoprotein composition in horses fed a fat-supplemented diet

This study was designed to compare the effects of a fat-supplemented diet versus a traditional diet on the lipoprotein (LP) content in horses. In the first of two trials, eight two-year old horses were fed a basal diet, in which 80% of the digestible energy was supplied as chopped alfalfa hay. One group of four horses (fat-supplemented group, FS) was fed the remaining 20% of the digestible energy as corn oil, while the other group of four horses (control) was fed rolled corn to complete their diet. Blood samples were collected at the start of the experiment and every 2.5 weeks thereafter for 10 weeks. Total serum lipids were measured in both groups of horses and the lipoproteins were fractionated into very low density LP (VLDL), low density LP (LDL), and high density LP (HDL) using ultracentrifugation and agarose-column chromatography. Each LP fraction was measured for protein, cholesterol (CH) and triglyceride TG) content. Total serum lipids were increased in the FS group above the control (9.16 vs. 4.65 mg/ml, week 5). Serum cholesterol and triglyceride concentrations were elevated in the FS group, but were highly variable. Variations in lipid concentrations may have been due to variation in time of sampling during the day. In the second trial, four of the eight horses were used and divided into the same two groups; FS vs. control. After an initial sample, postprandial serial blood samples (1 hour intervals for 8 hours) were drawn at 2, 4 and 6 weeks. Upon examination of the data, Hour 3 post-feeding was chosen to represent postprandial LP values. In both trials, the horses were able to adapt to the added dietary fat. Maintenance of body weight and increased speed of lipid clearance from the blood by the end of each trial in the FS group support this statement. In the FS group, there was an increase in VLDL TG concentration, but not in LDL. This indicates an increase in VLDL TG clearance from the circulation, presumably by increased lipoprotein lipase (LPL) activity. Cholesterol concentrations were also increased in the FS horses in the LDL and HDL. The rise in cholesterol may be attributed to endogenous recycling of liver products such as bile salts, which aid in digestion and absorption and are cholesterol based. In addition, there were greater quantities of LDL and HOL produced in the FS horses as supported by the increased protein concentrations as well as larger peaks for the eluate from the gel filtration column.     

Storage and mobilization of muscle glycogen in exercising horses fed a fat-supplemented diet

In a switchback experiment, six mature mares were fed a control and a fat-supplemented diet while being exercised in a galloping regimen. After three weeks adaptation to each diet, horses performed an exercise test (ET) consisting of four, 600-m gallops. Muscle biopsies were obtained before and after the ET, and blood samples were taken before, during and throughout recovery from the ET. Resting glycogen concentration in the biceps femoris muscle increased (P<.05) from 15.77 mg/g wet tissue when the horses were fed the control diet to 22.89 mg/g when they were fed the fats-supplemented diet. During the ET, the amount of glycogen mobilized by the muscle increased (P<.05) from 6.99 mg/g when the horses were fed the control diet to 13.09 mg/g when they were fed the fat-supplemented diet. When the horses were fed the fat-supplemented diet, they galloped faster (P<.09), at a constant heart rate, during the last two gallops of the ET. Thus, adapting exercising horses to a fat-supplemented diet increased muscle glycogen concentrations, which appeared to enhance their performance past the anaerobic threshold.     

Energy utilization of two diets for maintenance by horses; agreement with the new French net energy system

Four Standardbred geldings were fed hay or a diet of 60% hay + 40% concentrate at 2 levels of feeding. Feces and urine were collected for 6 days. Energy balances were determined by indirect calorimetry for4 days. The metabo- lizable energy (ME) requirements for maintenance of horses were calculated as ME intake for zero energy gain. They averaged 151 + 14 and 132 + 10 kcal/kg W -Ts for the hay diet and the mixed diet, respectively. The 14% difference in efficiency of ME utilization for maintenance predicted by the new French net energy system.     

Energy utilization of two diets for maintenance by horses; agreement with the new french net energy system

Four Standardbred geldings were fed hay or a diet of 60% hay + 40% concentrate at 2 levels of feeding. Feces and urine were collected for 6 days. Energy balances were determined by indirect calorimetry for 4 days. The metabolizable energy (ME) requirements for maintenance of horses were calculated as ME intake for zero energy gain. They averaged 151 ± 14 and 132±10 kcal/kg W^.75 for the hay diet and the mixed diet, respectively. The 14% difference in efficiency of ME utilization for maintenance predicted by the new French net energy system.     

Energy requirement for maintenance and growth of Nellore bulls and steers fed high-forage diets

Data from three comparative slaughter experiments with individually fed Nellore bulls (n = 31) and steers (n = 66) were utilized to determine their NEm and NEg requirements when fed high-forage diets. The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict NEm and NEg requirements. The Nellore bulls (Trial 1) were divided into two intake levels (ad libitum and 65% of the ad libitum). The steers (Trials 2 and 3) were allocated to three intake levels (ad libitum and 55 and 70% of the ad libitum). In both trials, there were three slaughter groups within each intake level. The three end points for the bulls were different days on treatment (100, 150, and 190 d and 130, 180, and 200 d, respectively, for older and younger animal subgroups). The steers were slaughtered when animals of the ad libitum treatment reached 400, 440, and 480 kg shrunk BW (SBW) on average for the first, second, and third group, respectively. For all body composition determinations, whole empty body components were weighed, ground, and subsampled for chemical analysis. In each of the trials, initial body composition was determined with equations developed from a baseline slaughter group, using SBW and empty BW (EBW), fat (EBF), and protein (EBP) as variables. The NEm was similar for bulls and steers; NEm averaged 77.2 kcal/ kg0.75 EBW. However, the efficiency of conversion of ME to net energy for maintenance was greater for steers than for bulls (68.8 and 65.6%, respectively), indicating that bulls had a greater ME requirement for maintenance than steers (5.4%; P < 0.05). Our analyses do not support the NRC (2000) conclusion that Nellore, a Bos indicus breed, has a lower net energy requirement for maintenance than Bos taurus breeds. An equation developed with the pooled data to predict retained energy (RE) was similar to the NRC (2000) equation. A second equation was developed to predict RE adjusted for degree of maturity (u): RE = (6.45 - 2.58/u) x EWG x e(0.469) x u), where u = current EBW/final EBW in which final EBW was 365 kg for steers and younger bulls and 456 kg for older bulls at 22% EBF, respectively.     

Energy utilisation in germ-free and conventional chicks fed diets containing sorbose

1. In experiment 1, growing conventional (CV) chicks were fed on diets containing graded amounts (0, 100, 200 and 300 g/kg diet) of sorbose from 4 to 14 d. Protein, fat and energy deposition were determined after carcase analysis. The values for growth, food efficiency, metabolisable energy (ME) and fat and energy depositions declined as the dietary sorbose content increased. 2. In experiment 2, the performances of germ-free (GF) and CV chicks fed on diets with (100 g sorbose/kg diet) or without sorbose were investigated. On both diets, body weight gain, food consumption and protein accumulation in GF chicks were significantly higher than those in CV birds. No significant differences were observed between the dietary treatment except for ME values, which were significantly lower for the sorbose diet. 3. It is suggested that dietary sorbose decreased energy utilisation, and that the microbial contribution to the utilisation of dietary sorbose was negligible in the chicken.     

Pigs receiving daily tailored diets using precision-feeding techniques have different threonine requirements than pigs fed in conventional phase-feeding systems

Background: There is large variation in amino acids requirements among pigs, hence feeding pigs individually with daily tailored diets or in groups with a single feed may require different levels of nutrients. Thus, the response to different threonine levels(70%, 85%, 100%, 115%, and 130% of the ideal threonine:lysine protein ratio of 0.65) was studied in growing pigs raised in a conventional group phase-feeding(GPF) system or fed individually using individual precision-feeding(IPF) techniques. In a 21-day trial, 110 barrows(25 ± 0.80 kg body weight) were housed in the same room and fed using electronic feeders. Five pigs per treatment were slaughtered at the end of the trial.Results: Threonine intake increased linearly for the IPF and GPF pigs(P 0.05). Lysine intake was similar across the treatments. Average daily gain, gain:feed ratio, and protein deposition were affected linearly by threonine level(P 0.05)in both feeding systems. Protein deposition in the GPF pigs was maximized at 150 g/d and a 0.65 threonine:lysine ratio, whereas protein deposition increased linearly in the IPF pigs. Plasma Met and serine levels were 11 and 7% higher, respectively, in the IPF pigs than in the GPF pigs(P 0.05). Dietary threonine increased(P 0.05)threonine concentration in the longissimus dorsi in a quadratic manner in the IPF pigs, whereas there was no effect in the GPF pigs. Longissimus dorsi collagen decreased as dietary threonine increased in the IPF and GPF pigs(P 0.10). Carcass muscle crude protein was 2% higher in the GPF pigs than in the IPF pigs(P 0.05).Conclusions: Individual pigs are able to modulate growth and the composition of growth according to threonine intake. The average amino acid ratio value that is currently used for GPF cannot be used for IPF.     

Immunocompetence of fattening pigs fed organic versus conventional diets in organic versus conventional housing

The effect of organic or conventional feeding on the immune response of pigs was determined using organic or conventional housing in a pig fattening unit. The experimental design involved four pens of four animals per housing and diet combination (organic housing and organic nutrition; organic housing and conventional nutrition; conventional housing and organic nutrition and conventional housing and conventional nutrition). The IgM, IgA and IgG responses against intramuscularly injected bovine thyroglobulin were determined as indicators of the antigen-specific immune responsiveness. Some general health and welfare related parameters were evaluated by measuring haptoglobin concentrations at selected times; blood lactate concentration was measured at slaughter. Conventional housing led to a higher IgG response three weeks after the first immunisation. Organic housing led to lower haptoglobin and lactate concentrations at slaughter, indicating a higher stress resistance in these pigs. No major differences between the two feeding types were found. We conclude that the immune responses following either a conventional or an organic diet are comparable, whereas organic housing can increase stress resistance at slaughter compared to conventional housing.     

Protein requirements of growing pups fed practical dry-type diets containing mixed-protein sources

The protein requirement of Pointer pups fed practical diets was assessed in 3 experiments. Eight-week-old pups required 25.2% protein when fed a combination of corn gluten meal, soybean meal, and meat and bone meal for 2 weeks. However, when a poor-quality poultry by-product meal was substituted for some of the corn gluten meal and meat and bone meal, the requirement increased to 27.5%. This increased requirement was explained by decreased digestibility of the poultry by-product meal diet. Pups fed each of the diets required 18% digestible protein to maximize growth rate. Sixteen-week-old pups were more efficient at utilizing the experimental diets, requiring only 23% crude protein (17.2% digestible protein) to maximize growth rate.     

Methodologies on estimating the energy requirements for maintenance and determining the net energy contents of feed ingredients in swine: a review of recent work

In the past two decades, a considerable amount of research has focused on the determination of the digestible(DE) and metabolizable energy(ME) contents of feed ingredients fed to swine. Compared with the DE and ME systems, the net energy(NE) system is assumed to be the most accurate estimate of the energy actually available to the animal. However, published data pertaining to the measured NE content of ingredients fed to growing pigs are limited. Therefore, the Feed Data Group at the Ministry of Agricultural Feed Industry Centre(MAFIC) located at China Agricultural University has evaluated the NE content of many ingredients using indirect calorimetry. The present review summarizes the NE research works conducted at MAFIC and compares these results with those from other research groups on methodological aspect. These research projects mainly focus on estimating the energy requirements for maintenance and its impact on the determination, prediction, and validation of the NE content of several ingredients fed to swine. The estimation of maintenance energy is affected by methodology, growth stage,and previous feeding level. The fasting heat production method and the curvilinear regression method were used in MAFIC to estimate the NE requirement for maintenance. The NE contents of different feedstuffs were determined using indirect calorimetry through standard experimental procedure in MAFIC. Previously generated NE equations can also be used to predict NE in situations where calorimeters are not available. Although popular, the caloric efficiency is not a generally accepted method to validate the energy content of individual feedstuffs. In the future,more accurate and dynamic NE prediction equations aiming at specific ingredients should be established, and more practical validation approaches need to be developed.     

Metabolic utilization of energy and maintenance requirements in pregnant sows

Energy and nitrogen balances were measured in two experiments involving 32 Large-White gilts kept in respiration chambers and given a constant diet providing 27.6 MJ metabolizable energy (ME) per day (Experiment 1) or 32.7 MJ ME per day (Experiment 2). Measurements were made on the same animals at mid (Day 50–80) and late (Day 95 to farrowing) pregnancy in both experiments and also during early pregnancy (Days 30–50) in experiment 2. A total of 90 balances were performed.Advancement of pregnancy was associated with an increase in protein deposition and in heat production (67 kJ day⁻¹ for a constant metabolizable energy (ME) intake) which resulted in reduced energy and fat deposition. Maintenance requirements (420–430 kJ ME kg⁻¹ W^C.75) were constant over pregnancy. Efficiencies of ME utilization for uterine (k_u) and maternal (k_r) deposition were 40–50% and about 80%, respectively. Efficiencies for protein (k_p) and fat (k_f) deposition were 58–67% and 80–90%, respectively. Additional heat loss with advancement of pregnancy (0.53 kJ kg⁻¹ W^0.75 day ⁻¹ of pregnancy) is related to the changes in the composition (protein vs. fat) and localization (uterine vs. maternal tissues) of the energy gain and not due to extra heat production arising from the pregnancy itself.     

A meta-analysis of energy and protein requirements for maintenance and growth of Nellore cattle

A meta-analysis was conducted to determine NE and net protein requirements of growing bulls, steers, and heifers of Nellore purebred and Nellore x Bos taurus crossbreds. A database of 16 comparative slaughter studies (n = 389 animals) was gathered to provide enough information to develop equations to predict the requirements of NE(m), NE(g), and net protein for maintenance (NP(m)) and growth (NP(g)). The data were analyzed using a random coefficients model, considering studies as random effects, and sex and castrate status (bulls, steers, and heifers; n = 262, 103, and 24, respectively) and breeds as fixed effects. There were no differences in NE(m) requirements among sex and castrate status (P = 0.73) and breeds (P = 0.82). The combined data indicated a NE(m) requirement of 75 kcal/ kg(0.75) of empty BW (EBW) with a partial efficiency of use of ME for NE(m) of 0.67. The NE(g) requirement was different (P = 0.009) among sex and castrate status and tended (P = 0.06) to be different among breeds. The equation for NE(g) requirement for bulls was 0.0514 x EBW(0.75) x EWG(1.070); for steers, it was 0.0700 x EBW(0.75) x EWG(1.070); and for heifers, it was 0.0771 x EBW(0.75) x EWG(1.070), where EWG = EBW gain (kg/d). The partial efficiency of use of ME for NE(g) was not different among sex and castrate status (P = 0.33) and breeds (P = 0.20) and averaged 0.44. There were no differences in NP(m) requirement among sex and castrate status (P = 0.59) and breeds (P = 0.92); the overall NP(m) requirement was 1.74 g of NP.kg(-0.75) of EBW.d(-1). The overall MP requirement for maintenance was 2.59 g of MP.kg(-0.75) EBW.d(-1). The NP(g) requirement (g/d) was not different among sex and castrate status (P = 0.59) and breeds (P = 0.14); the overall equation was EWG x [217 - (12.8 x RE/EWG)], where RE = retained energy (Mcal/d). The percentage of RE deposited as protein (%RE(p)) decreased exponentially as the content of RE in the gain (REc, Mcal/kg of EWG) increased. Because no study effect was observed, we pooled the data across studies and the overall equation to predict %RE(p) was 10.1 + 167e((-0.66 x REc)). Our results do not support the hypothesis that bulls have greater NE(m) requirements than steers and heifers. Likewise, no significant differences in the NP(m) requirements among bulls, steers, and heifers were detected. Nonetheless, the NE(g) requirement of steers was greater than bulls and less than heifers. Even though the %RE(p) was negatively correlated with the concentration of energy in the EWG, our findings indicated no differences in NP(g) requirement among bulls, steers, and heifers.     

Digestible and metabolizable energy of crude glycerol for growing pigs

The apparent DE and ME values of crude glycerol for growing pigs were determined in 5 experiments using crude glycerol (86.95% glycerol) from a biodiesel production facility, which used soybean oil as the initial feedstock. Dietary treatments were 0, 5, or 10% glycerol addition to basal diets in Exp. 1; 0, 5, 10, or 20% glycerol addition to basal diets in Exp. 2; and 0 and 10% crude glycerol addition to the basal diets in Exp. 3, 4, and 5. Each diet was fed twice daily to pigs in individual metabolism crates. After a 10-d adjustment period, a 5-d balance trial was conducted. During the collection period, feces and urine were collected separately after each meal and stored at 0 degrees C until analyses. The GE of each dietary treatment and samples of urine and feces from each pig were determined by isoperibol bomb calorimetry. Digestible energy of the diet was calculated by subtracting fecal energy from the GE in the feed, whereas ME was calculated by subtracting the urinary energy from DE. The DE and ME values of crude glycerol were estimated as the slope of the linear relationship between either DE or ME intake from the experimental diet and feed intake. Among all experiments, the crude glycerol (86.95% glycerol) examined in this study was shown to have a DE of 3,344 +/- 8 kcal/kg and an ME of 3,207 +/- 10 kcal/kg, thereby providing a highly available energy source for growing pigs.