Effects Of Dietary Energy Source Research Articles

Effect of dietary energy source on in vitro substrate utilization and insulin sensitivity of muscle and adipose tissues of Angus and Wagyu steers

Angus (n = 8; 210 kg of BW) and 7/8 Wagyu (n = 8; 174 kg of BW) steers were used to evaluate the effects of dietary energy source on muscle and adipose tissue metabolism and insulin sensitivity. Steers were assigned to either a grain-based (corn) or hay-based (hay) diet and fed to similar final BW. At slaughter, LM and s.c. and i.m. adipose tissue samples were collected. Portions of the LM and adipose tissues were placed immediately in liquid N for later measurement of glycolytic intermediates. Fresh LM and s.c. and i.m. adipose tissues were incubated with [U-(14)C]glucose to assess glucose metabolism in vitro. All in vitro measures were in the presence of 0 or 500 ng/mL of insulin. Also, s.c. and i.m. adipose tissues were incubated with [1-(14)C]acetate to quantify lipid synthesis in vitro. Glucose-6-phosphate and fructose-6-phosphate concentrations were 12.6- and 2.4-fold greater in muscle than in s.c. and i.m. adipose tissues, respectively. Diet did not affect acetate incorporation into fatty acids (P = 0.86). Insulin did not increase conversion of glucose to CO(2), lactate, or total lipid in steers fed hay but caused an increase (per cell) of 97 to 110% in glucose conversion to CO(2), 46 to 54% in glucose conversion to lactate, and 65 to 160% in glucose conversion to total lipid content in adipose tissue from steers fed corn. On a per-cell basis, s.c. adipose tissue had 37% greater glucose oxidation than i.m. adipose (P = 0.04) and 290% greater acetate incorporation into fatty acids than i.m. adipose (P = 0.04). Insulin addition to s.c. adipose tissue from corn-fed steers failed to stimulate glucose incorporation into fatty acids, but exposing i.m. adipose tissue from corn-fed steers to insulin resulted in a 165% increase in glucose incorporation into fatty acids. These results suggest that feeding hay limited both glucose supply and tissue capacity to increase glucose utilization in response to insulin without altering acetate conversion to fatty acids. Because s.c. adipose tissue consistently utilized more acetate and oxidized more glucose than did i.m. adipose, these results suggest that hay-based diets may alter i.m. adipose tissue metabolism with less effect on s.c. adipose tissue.

Effects of dietary energy source and physical conditioning on insulin sensitivity and glucose tolerance in Standardbred horses

There is evidence that adaptation to diets rich in nonstructural carbohydrates (NSC) contributes to the development of insulin resistance in horses. To date, however, no study in horses has examined the effects of physical conditioning on diet-associated alterations in insulin sensitivity and glucose tolerance. To examine the effects of adaptation to concentrate feeds rich in NSC or fat on insulin sensitivity and glucose tolerance in horses, both in the sedentary state and after a subsequent period of physical conditioning. Fourteen mature Standardbred horses underwent both a euglycaemic-hyperinsulinaemic clamp (EHC) and oral glucose tolerance test (OGTT) after each of the following phases: Baseline - fed only forage cubes for 3 weeks; Diet horses were randomly assigned to receive either a high NSC (S) concentrate or a high fat concentrate (F) with forage cubes for 6 weeks; and Diet x Exercise - horses remained on the assigned ration and underwent a 7 week period of physical conditioning. An incremental exercise test was performed before, and after, the Diet x Exercise phase for measurement of the peak rate of oxygen consumption (VO2peak). In both diet groups, there was an approximately 10% increase in mean VO2peak after physical conditioning. The mean rate of glucose disposal (M) per unit of serum insulin (I) during the EHC [M/I ratio] in S horses was 30% lower (P<0.05) in the Diet phase when compared to Baseline, but not different from Baseline after physical conditioning. The S diet also resulted in a greater (P<0.05) OGTT insulin response (area under the insulin vs. time curve, AUC(INS)) in both Diet and Diet x Exercise phases when compared to Baseline. In F, insulin sensitivity (mean M/I ratio) and glucose tolerance were unchanged during the study. Feeding a diet rich in NSC for 6 weeks resulted in decreased insulin sensitivity and impaired glucose tolerance. Physical conditioning lessened the effects of the high NSC diet on insulin sensitivity, as evidenced by the return to baseline M/I, but did not mitigate the impaired glucose tolerance. Decreased insulin sensitivity has been implicated in the development of obesity and laminitis in horses and the present findings provide support for avoidance of concentrates with high NSC in the dietary management of horses at risk for the development of these conditions.

Effect of dietary energy source on energy balance, production, metabolic disorders and reproduction in lactating dairy cattle

The pathway for oxidation of energy involves a balanced oxidation of C2 and C3 compounds. During early lactation in dairy cattle this C2/C3 ratio is out of balance, due to a high availability of lipogenic (C2) products and a low availability of glycogenic (C3) products relative of the C2 and C3 products required for milk production. This review compares studies which manipulated dietary energy source and shows that dietary energy source can affect the balance of the C2/C3 ratio, as indicated by plasma NEFA, beta-hydroxybutyrate (BHBA) and glucose levels. It is shown that glycogenic nutrients increase glucose and insulin concentrations and decrease NEFA and BHBA plasma levels. Extra lipogenic nutrients elevate NEFA and BHBA and decrease plasma glucose concentrations. Lipogenic nutrients generally increase milk fat percentage and decrease milk protein percentage, suggesting a surplus of C2 compounds. The inverse is the case for feeding extra glycogenic nutrients, implying reduced deamination and oxidation of glycogenic amino acids. Feeding extra glycogenic nutrients improved the energy balance (EB), in contrast to ambiguous results of lipogenic nutrients on EB. Moreover, glycogenic feed may reduce the severity of ketosis and fatty liver, but increased the incidence of (sub)clinical acidosis. Since studies are scarce, it seems difficult to draw conclusions on the effects of dietary energy source on reproduction. However, lipogenic nutrients decrease glucose and increase NEFA and BHBA plasma levels. High plasma NEFA and BHBA and low plasma glucose levels are associated with decreased reproductive performance, which might imply the C2/C3 compound balance to be important for reproductive function.

The effect of dietary energy source on serum concentration of insulin-like growth factor-I growth hormone, insulin, glucose, and fat metabolites in weanling horses.

Feeding diets high in soluble carbohydrates to growing horses has been implicated in the development of orthopedic diseases; as a result, substitution of dietary fat for soluble carbohydrates has received attention. Because IGF-I is integral to growth and cartilage development and because it is influenced by nutrition, we evaluated the effect of dietary fat substitution on metabolic endpoints and circulating GH and IGF-I in growing horses. Twelve Quarter Horse weanlings, four female and eight male, 151 to 226 d old, were blocked by sex and age and assigned to two treatment groups. Group one (CARB; n = six) was fed a concentrate containing 2.21% fat and 33.9% starch; group two (FAT; n = six) was fed a concentrate containing 10.3% fat and 24.0% starch. Both concentrates contained 3.0 Mcal/kg of DE and 16% CP. Brome hay also was fed. Diets were fed at 0800 and 1600 for 60 d. On d 0, 30, and 60, blood samples were obtained via a jugular catheter from 1 h before until 5 h after the morning feeding. Serum was analyzed for glucose, insulin, GH, IGF-I, NEFA, and total cholesterol (CHOL). Neither ADG (0.85 +/- 0.04 and 0.84 +/- 0.04 kg) nor concentrate DMI (4.04 +/- 0.12 and 4.03 +/- 0.12 kg/d) differed between treatments. There were consistent increases in glucose and insulin in response to feeding on d 0, 30, and 60 for both groups. On d 30, the glucose response to feeding was less (P = 0.07) over time in FAT vs. CARB; however, there were no significant treatment x time effects on d 0 or 60. On d 60, the insulin response to feeding was less (P < 0.05) over time in FAT compared with CARB; however, there was no treatment x time effect on d 0 or 30. Serum CHOL concentrations did not differ between groups on d 0. Horses in the FAT group had increased CHOL concentrations on d 30 and 60 compared with CARB (P < 0.01). Although treatment x time interactions were noted for GH on d 30 and 60 (P < 0.05), only transient and inconsistent differences in the secretory profiles between CARB and FAT treatments were evident at those sampling times. Serum NEFA and IGF-I did not differ between treatments on d 0, 30, or 60. These results suggest that dietary energy source, at least at the level used in this study, did not affect foal growth performance or serum IGF-I and NEFA concentrations. Fat substitution increased serum CHOL and variably affected serum GH, glucose, and insulin concentrations in response to feeding.

Effect of dietary energy source on the performance and perirenal fat thickness evolution of primiparous rabbit does

AbstractSeventy-four New Zealand ✕ Californian females were used to determine the influence of dietary energy source on the performance and perirenal fat thickness (PFT) change measured by ultrasound of primiparous rabbit does. Three highly concentrated diets were designed with different dietary energy sources: animal fat (diet F), vegetable oil (diet O) and cereal starch (diet S), and does were fertilized by artificial insemination after parturition (AP group) or around weaning (AW group), litters being weaned at 28 days of age. There were no significant differences in live weight and food intake of females throughout gestation, but does given diet S showed a higher increase in their PFT until 28th day than those given diets F and O (P &lt; 0·01), although all females had a similar PFT at parturition. Rabbit does given diets S and O showed a significantly higher dietary energy intake than those given diet F (P &lt; 0·01) during the first weeks of lactation, and similar thereafter until the second parturition. Milk yield and litter weight gain were significantly higher with fat-enriched diets (P &lt; 0·05), and milk composition of rabbit does given diet F showed a higher total solids content (P = 0·01), fat (P &lt; 0·001) and energy (P &lt; 0·01) than milk of does receiving diets O or S. Although pups on fat diets showed a higher weaning weight (P &lt; 0·05), dietary treatment during lactation did not have any effect on the performance of pups during the subsequent growing period. PFT always decreased during lactation for does given fat-enriched diets, while it increased for does given diet S and fertilized after parturition. Live weight of AP does was significantly higher at 21st day of lactation (P &lt; 0·01) and at weaning (P &lt; 0·001), and they showed a significantly lower food intake during the final week of lactation. The period from weaning to parturition was too short for AP does, which showed a decrease of their PFT, while AW does showed an increase of their PFT and a greater number of pups alive at birth (P &lt; 0·05). Due to the lower milk yield of rabbit does fertilized AP, their pups showed a significantly higher solid food intake (P &lt; 0·001), resulting in a similar value for the live weight of pups in both groups at weaning. The earlier promotion of solid food intake significantly affected the food intake of litters during the subsequent growing period, presenting higher values for pups coming from AP does. In conclusion, the addition of dietary fat, especially from animal origin, seems to improve the utilization of energy for milk production, while the use of a high level of starch could decrease the negative balance of primiparous rabbit does during lactation.

Effects of postweaning dietary energy source on reproductive traits in primiparous sows.

An experiment was conducted to study the effects of major dietary energy source fed from weaning to ovulation or from ovulation to d 35 of pregnancy on reproductive traits in primiparous sows. Dietary energy sources were used to manipulate the plasma insulin concentration. One hundred thirteen sows were used in a split-plot design. From weaning to ovulation sows were fed at two times maintenance either a diet with tallow (Fat) or maize starch plus dextrose (Starch) as the major energy source. From ovulation onward, sows within each dietary group were alternately reassigned to either the Fat or the Starch diet and were fed at 1.25 times maintenance. Estrus detection was performed three times a day from d 3 to 9 after weaning and sows were inseminated each day of standing estrus. On d 35 of pregnancy, the sows were slaughtered and their reproductive tracts were removed. Plasma insulin concentration was higher in sows fed the Starch-rich diet than in sows fed the Fat-rich diet on d 4 after weaning (1.30 vs 0.97 ng/mL, P = 0.08) and on d 32 of pregnancy (1.20 vs 0.51 ng/mL, P < 0.001). Plasma glucose and IGF-I concentration on d 4 after weaning and d 32 of pregnancy did not differ between sows on the two dietary energy sources. The percentage of sows exhibiting estrus within 9 d after weaning was 52 and 67% for the Fat and Starch diet before ovulation, respectively (P = 0.11), whereas the weaning-to-estrus interval was 134 vs 123 h, respectively (P = 0.12). Survival analysis showed that sows fed the Fat-rich diet had a 1.6 times higher risk to remain anestrous until d 9 after weaning than sows fed the Starch-rich diet (P = 0.04). No effect of dietary energy source, either before or after ovulation, on uterine, placental, or embryonal development on d 35 of pregnancy was found. It can be concluded that the dietary energy source provided after weaning can affect the risk of sows to remain anestrous but does not affect uterine, placental, or embryonic traits.

Effect of dietary energy sources on rumen kinetics, feed utilization. weight gain, and physical-chemical characteristics of meat in sheep

Effect of dietary energy sources on rumen kinetics, feed utilization. weight gain, and physical-chemical characteristics of meat in sheep

Dietary energy source at two feeding levels during lactation of primiparous sows: II. Effects on periestrus hormone profiles and embryonal survival.

Our objective was to study the effects of dietary energy source (fat or starch) on periestrus hormone profiles and embryonal survival in primiparous sows. During lactation, 48 primiparous sows were fed either a starch-rich or a fat-rich diet, at either a high (44 MJ NE/d) or a low (33 MJ NE/d) feeding level. After weaning, all sows received the same amount of feed (31 MJ NE/d from weaning to estrus and 17.5 MJ NE/d from breeding to slaughter) of the same dietary energy source fed during lactation. Around estrus, blood samples were taken to analyze the preovulatory LH surge, estradiol (E2), and progesterone (P4). Sows were inseminated on each day of standing estrus. On d 35 after last insemination, all 35 pregnant sows were slaughtered and their reproductive tracts were removed. The number, weight, and length of the embryos and placentas were determined as well as the weight and length of the uterus. The LH, E2, and P4 profiles were similar for the treatment groups, except for the E2 levels at 16, 12, and 8 h before the LH surge, which were lower in the sows fed the fat-rich diet at a low level. Ovulation rate tended to be higher in sows fed the high compared to the low feeding level during lactation (18.0 vs. 16.2; P = .09), but the number of total and viable embryos as well as embryonal survival rate were not influenced by the treatments. Neither uterine length and weight nor length and weight of the embryos and placentas were affected by treatments. However, after removal of the embryo-placental units, uterine weight was greater in sows fed the high than in those fed the low feeding level during lactation (1.8 vs. 1.6 kg; P = .03). Plasma insulin concentration during lactation was not related to any of the uterine, placental, or embryo traits. Mean progesterone concentration between 24 and 250 h after the LH surge was positively correlated with embryonal survival. Differences in progesterone concentration between sows with high and low embryonal survival were evident from 172 h after the LH surge. From the present study, we conclude that altering feeding level during lactation or dietary energy source from farrowing until d 35 of subsequent pregnancy did not affect embryonic development and embryonal survival.

The effect of dietary energy source on diet digestibility and growth performance of rainbow trout

There is confusion in the literature as to the effects of carbohydrates in the diet of fishes. Warmwater, herbivorous fishes can digest more complex carbohydrates (Shiau and Chuang, 1995) while coldwater, carnivorous fish may digest glucose better. However high levels of dietary glucose may increase fat deposition in the viscera (Bergot, 1979). Furthermore, Kaushik and de Oliva-Teles (1985) reported that heat treatment of raw starch in diets for rainbow trout improved its utilisation. This study was conducted to determine the digestibility of diets containing raw wheat, extruded wheat, glucose and fish oil. The effects of these diets on growth performance and body composition of trout were also determined.

Effects of dietary energy source on plasma glucose and insulin concentration in gilts

ZusammenfassungDer Einfluß des Futterenergieträgers auf die Konzentrationen von Glucose und Insulin im Plasma von JungsauenEs wurde der Einfluß verschiedener Energieträger auf die Konzentrationen von Glucose und Insulin im Plasma von Jungsauen untersucht. Fünf Jungsauen erhielten in einem Versuch nach einem Lateinischen Quadrat drei Rationen mit 238 g/kg Maisstärke (Stärke), 178 g/kg Maisstärke + 60 g/kg Dextrose (Zucker) oder 96 g/kg Rindertalg (Fett) isoenergetisch verabreicht. Aus den Ergebnissen gehen vergleichbare präprandiale Plasma‐Glucose‐Konzentrationen für alle drei Rationen hervor. Die Glucose‐Konzentration lag 24 min. nach der Fütterung (p &lt; 0,05), bei der Zucker‐Ration höher als bei der Fett‐Ration. Die Plasma‐Insulin‐Konzentration lag in der Zucker‐Gruppe (p &lt; 0,05) höher als in der Fett‐Gruppe, für die Stärke‐Gruppe lagen die Werte zwischen der Zucker‐ und Fett‐Gruppe und unterschieden sich nicht von den anderen beiden Rationen. Das Verhältnis zwischen der postprandialen mittleren und maximalen Insulin‐ und Glucose‐Konzentration lag bei der Zucker‐ bzw. Stärke‐Ration höher als bei der Fett‐Ration. Aus den Ergebnissen läßt sich schließen, daß die Insulin‐Konzentration durch unterschiedliche Energieträger im Futter beeinflußt werden kann.

The Effect of Dietary Energy Source During Mid to Late Lactation on Liver Triglyceride and Lactation Performance of Dairy Cows

Control [1.61 Mcal of net energy for lactation (NEL)/kg of dry matter (DM)], high grain (1.70 Mcal of NEL/kg of DM), or high fat [1.70 Mcal of NEL/ kg of DM with 2.3% tallow (DM basis)] diets were fed to 43 cows (150±3.1 d in milk) during mid to late lactation to determine effects on performance characteristics, metabolic parameters, or both during mid to late lactation, the dry period, and the first 100 d of the next lactation. All cows received identical diets during the dry period and during early lactation. Increasing the energy density of the diets during mid to late lactation increased DM intake (DMI), plasma nonesterified fatty acid concentration, milk production, and milk protein yield. Compared with the high grain diets, fat supplementation decreased DMI and the percentage of milk protein but increased plasma nonesterified fatty acid concentration without causing elevation of liver triglyceride at the end of mid to late lactation. Increased energy density of the diets did not affect body condition score during mid to late lactation. There were no residual effects for any of the treatments on DMI, lactation performance, or body weight in the subsequent lactation. However, energy supplementation during mid to late lactation increased liver triglyceride content after calving. Compared with high fat diets, high grain diets fed during mid to late lactation increased plasma β-hydroxybutyrate concentration in the subsequent lactation. High energy diets fed during mid to late lactation may influence lipid metabolism during the following lactation.

Effect of dietary energy source and immunological challenge on growth performance and immunological variables in growing pigs.

Forty-eight growing pigs (23 kg BW) were assigned to four treatments (n = 12) arranged as a 2 x 2 factorial. Dietary energy source (conventional [CON] vs high-oil corn [HOC]), with or without an immunological challenge (IC) regimen constituted main effects. The IC regimen consisted of injection of endotoxin (E. coli lipopolysaccharide [LPS]) and vaccination for porcine respiratory and reproductive syndrome (PRRS). Growth performance data were collected over a 5-wk period and are presented as prechallenge (d 1 to 14; d 1 was the 1st d of the study), challenge (d 15 to 21), and postchallenge (d 22 to 36) periods, and overall. Overall, the pigs fed HOC consumed less feed (P < .11) and gained more efficiently (P < .03). During the immunological challenge period, ADG was depressed 21% and feed intake 15% (P < .01). The IC resulted in lower (P < .01) serum alpha-1-acid glycoprotein (AGP) concentrations on d 22, and the magnitude of the reduction was greater in the pigs fed the CON diet (energy source x immune challenge, P < .10). Serum AGP concentrations remained lower (P < .08) in challenged pigs on d 36. Immunoreactive prostaglandin concentrations were higher (55%, P < .08) in the pigs fed HOC immediately following the IC period (d 22). The data reported herein indicate that the performance of pigs fed HOC is satisfactory, and that feeding HOC does not compromise growth performance during or after an immunological challenge.

Effects of dietary energy source and level on performance of newly arrived feedlot calves.

Three experiments were conducted with Simmental x Angus crossbred steers to determine the effects of energy source and level on performance of newly arrived feedlot calves. In trial 1, 68 steers (initial BW 215 +/- 9.4 kg) were used in a 2 x 3 factorial experiment to determine the effects of receiving diet and previous creep feed on performance. Diets were composed primarily of either corn silage, corn silage + alfalfa pellets + dry corn, or dry corn + alfalfa pellets. For the 41-d trial, calves fed the corn silage-based diet had greater (P < .05) ADG and feed efficiencies than calves fed the other two diets. In Trial 2, 60 steers (initial BW 212 +/- 4.6 kg) were used in a 28-d completely randomized design experiment to determine the effects of 16% CP receiving diets containing 70, 75, 80 or 85% concentrate on performance. There were no differences (P > .10) in ADG or feed efficiency due to dietary concentrate level. In Trial 3, 77 steers (initial BW 226.3 +/- 3.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of dietary concentrate and protein levels on performance during a 28-d receiving period. The factors were concentrate level (70 vs 85% concentrate) and protein level (12.5%, 16%, or phase-fed at 23%, 17%, 14%, and 12.5% during wk 1, 2, 3, and 4, respectively). During wk 1, calves fed the 85% concentrate diet had greater (P < .01) DMI, ADG, and feed efficiency compared with 70% concentrate. Calves fed the 16% CP and phase-fed protein diets had greater (P < .01) DMI, ADG, and greater (P < .02) feed efficiency than calves fed the 12.5% CP diets. Receiving diets containing at least 16% CP and > 70% concentrates are beneficial to calves during the first week after feedlot arrival.

Effects of energy source in the diet on reproductive hormones and insulin during lactation and subsequent estrus in multiparous sows.

Two experiments were performed. The first experiment was done to study the effects of dietary energy source on plasma insulin concentration using five gilts in a Latin square design with two diets over two periods. The diets contained either 200 g/kg of cornstarch (Starch) or soybean oil (Fat) as energy sources. Results indicate that insulin response was greater in the Starch-fed than in the Fat-fed gilts. A second experiment was performed in which 18 multiparous sows were fed one of the two experimental diets from farrowing until slaughter at d 35 of subsequent pregnancy. All sows nursed nine pigs. Blood samples were taken from a permanent jugular vein catheter every 12 min during a 12-h period on d 109 +/- 1 of pregnancy, on d 7 +/- 1, 14 +/- 1, and 21 +/- 1 of lactation, and on the day of weaning ( d 22 +/- 1). From 48 h after weaning, blood samples were taken every 4 h until 24 h after ovulation. After that, blood samples were taken at 12-h intervals until d 10 after ovulation. Differences between diets in insulin response were not significant. In Starch-fed sows, LH pulsatility at d 7 of lactation was greater (P < .05), the preovulatory LH surge was greater ( P < .05), and progesterone production was greater (P < .05) from 108 h until 256 h after the LH surge than in the Fat-fed sows. Results indicate that feeding Starch-rich diets to multiparous sows compared with Fat-rich diets, on an isocaloric basis, increases LH pulsatility during early lactation, the preovulatory LH surge, and progesterone production after the LH surge.

Effect of Dietary Energy Sources on the Utilization of Protein by &lt;i&gt;Colossoma macropomum&lt;/i&gt; Fingerlings

Effect of Dietary Energy Sources on the Utilization of Protein by &lt;i&gt;Colossoma macropomum&lt;/i&gt; Fingerlings

The effect of dietary energy source during lactation on sow milk production and piglet performance

Piglets which are heavier at weaning generally show a lower incidence of post weaning disease and mortality, superior growth rates and convert feed to gain with greater efficiency than smaller piglets. Weaning weight is largely determined by the yield and quality of milk available to the suckling piglet, and these parameters are becoming increasingly important with the large litter sizes produced by modern prolific sows.This experiment was designed to quantify milk production by sows of a modern commercial genotype and investigate possibilities for dietary manipulation of milk yield and composition as a means of increasing piglet performance.

HEPATIC UREA SYNTHESIS AND SITE AND RATE OF UREA REMOVAL FROM BLOOD OF BEEF STEERS FED ALFALFA HAY OR A HIGH CONCENTRATE DIET

Five Hereford × Angus steers, 240 ± 6 kg liveweight with chronic indwelling catheters in various sites in the splanchnic bed were used to evaluate effects of dietary energy source and nitrogen (N) level on urea synthesis and site and rate of urea removal from blood. Alfalfa hay (162 g N d−1) or a high concentrate diet (95 g N d−1) were fed at similar metabolizable energy intake (54.8 MJ d−1). Compared with the alfalfa, the high concentrate, low N diet decreased (P &lt; 0.05) blood concentrations of urea N, hepatic urea synthesis, urinary urea N excretion, transfer of urea N to poststomach tissues, and salivary transfer of urea N. Similarly, the high concentrate diet decreased net absorption of ammonia N and increased net absorption of glucose from portal-drained viscera decreased hepatic removal of ammonia N and α-amino N, and increased release of α-amino N by splanchnic tissues (P &lt; 0.01). Blood flow (dilution of para-aminohippurate) through the liver and gut was not affected (P &gt; 0.10) by diet. A greater (P &lt; 0.05) portion of urea synthesized in the liver was transferred to the gut when the high concentrate diet was fed. Site of total urea transfer to the gut (from blood plus saliva) shifted from 37% of total transfer into poststomach (alfalfa) to 75% into stomach (high concentrate diet). Increased intake of readily fermentable carbohydrate at the expense of N and fiber increased the percentage of liver urea synthesis recycled to the gut and focused that recycling into the stomach (rumen) in these steers. Key words: Bovine, energy, nitrogen, urea flux, gut, liver

Effect of Dietary Energy Source and Concentration on Performance of Dairy Cows During Early Lactation

Eighteen Holstein heifers were placed into groups of 3 according to projected calving date, prepartum BW, and prepartum condition score. Following parturition, animals within each group were assigned randomly to one of three diets and remained on the experiment for 45 d. Diets consisted of forage: concentrate ratios of 72:28, 53:47, or 73:27 (isocaloric to the 53:47 ratio by addition of 8% soybean oil). Diets were fed twice daily as total mixed rations. Blood, rumen fluid, and adipose tissue were sampled at −7, 5, 20, and 45 d of lactation.Performance means were, respectively: DM intake (kg/d) 13.9, 14.9, and 12.4; milk (kg/d) 24.5, 25.8, and 18.6; milk fat (%) 3.77, 3.59, and 3.62; milk protein (%) 3.03, 2.99, and 3.11; body condition score (0=thin, 5=fat) 1.53, 1.87, and 1.99; and BW (kg) 514, 523, and 505. Cows fed soybean oil had higher ruminal isoacids than those fed the other diets and higher acetate than cows on the 53:47 diet. Diets had no effect on blood metabolites or activity of adipose glycerol-P dehydrogenase (EC 1.1.1.8). The soybean oil diet reduced short-chain fatty acids and increased long-chain fatty acids in milk. Feed intake and milk production were highest for cows receiving the 53:47 diet. As expected, animals on the 72:28 diet did not consume adequate energy to maintain high production which concurrently resulted in lower body condition scores.

Endocrine adaptations of periparturient swine to alteration of dietary energy source.

Lipid compared with carbohydrate calories in the diet of peripartal sows was examined for specific metabolic effects. Blood samples from second-parity Yorkshire sows fed isocaloric-isonitrogenous diets that differed by either glucose or corn oil supplying 20% of the daily metabolizable energy intake were assayed for growth hormone (GH), insulin and prolactin (PRL) concentrations. On d 97 to 103 of gestation, serum GH levels were reduced following feed intake; the reduction was greater (P less than .05) in glucose-fed sows during the postprandial period. Insulin concentration was increased following consumption of either diet, but to a greater (P less than .05) extent in glucose-fed sows corresponding to the greater (P less than .05) blood glucose response. Basal, fasting concentrations of PRL were not affected by dietary energy source; however, thyrotropin-releasing hormone (TRH) infusion resulted in a greater (P less than .05) PRL response of fat-fed sows. Samples obtained on d 8 to 11 of lactation revealed that TRH stimulated (P less than .05) GH secretion and the response was greater (P less than .05) in fat-fed sows. Plasma insulin concentration was increased (P less than .05) following feeding, and the increase was greater (P less than .05) in glucose-fed sows. Similar to the response measured in gestating sows, TRH-induced increases in PRL was greater in fat-fed, lactating sows. Sham-nursing did not influence maternal PRL concentration compared with the immediate increase noted following natural nursing. No effect of dietary energy source on reproductive performance characteristics was noted. Results of this study have shown that dietary lipid, compared with carbohydrate, selectively increased the sensitivity of the pituitary gland to a GH and PRL secretagogue such as TRH. The beneficial effects of lipid in the diet of peripartal swine may be attributable, in part, to the effect of dietary lipid on maternal pituitary PRL synthesis and(or) release.

Abdominal Fat of Broilers as Influenced by Dietary Level of Animal Fat

In an attempt to determine the effect of dietary energy source on the quantity of abdominal fat in broilers, three levels of dietary animal fat (4, 7, and 10%) in isocaloric and iso-nitrogenous diets were fed in place of a carbohydrate energy source. Three trials were conducted. As dietary animal fat increased, the amount of abdominal fat in broilers increased under both a moderate- and a high-temperature rearing regimen. However, as dietary animal fat increased, the body weight gain in broilers tended to increase. It is possible that the benefits of increased growth outweigh the disadvantages of increased abdominal fat when dietary fat is added. Data are presented to provide the industry with figures to help in this decision.