Digestible Energy Basis Research Articles

Mammary gland metabolite utilization in response to exogenous glucose or long-chain fatty acids at low and high metabolizable protein levels

We investigated mammary gland metabolism in lactating dairy cattle in response to energy from glucogenic (glucose; GG) or lipogenic (palm olein; LG) substrates at low (LMP) and high (HMP) metabolizable protein levels. According to a 6 × 6 Latin square design, 6 rumen-fistulated second-lactation Holstein-Friesian dairy cows (97 ± 13 d in milk) were abomasally infused with saline (LMP-C); isoenergetic infusions (digestible energy basis) of 1,319 g/d glucose (LMP-GG), 676 g/d palm olein (LMP-LG), or 844 g/d essential AA (EAA; HMP-C); or isoenergetic infusions of 1,319 g/d glucose + 844 g/d EAA (HMP-GG) or 676 g/d palm olein + 844 g/d EAA (HMP-LG). Each experimental period consisted of 5 d of continuous infusion followed by 2 d of rest. A total mixed ration (42% corn silage, 31% grass silage, and 27% concentrate on a dry matter basis) formulated to meet 100 and 83% of net energy and metabolizable protein requirements, respectively, was fed at 90% of ad libitum intake by individual cow. Arterial and venous blood samples were collected on d 5 of each period. Infusing GG or LG at the HMP level did not affect milk yield or composition differently than at the LMP level. Neither GG nor LG infusion stimulated milk protein or lactose yield, but fat yield tended to decrease with GG and tended to increase with LG. Infusion of GG increased arterial plasma concentrations of glucose and insulin and decreased concentrations of β-hydroxybutyrate (BHB), nonesterified fatty acids, long-chain fatty acids (LCFA), total AA, EAA, and group 2 AA. Infusion of LG increased arterial triacylglycerides (TAG) and LCFA but did not affect EAA concentrations. Compared with the LMP level, the HMP level increased arterial concentrations of BHB, urea, and all EAA groups and decreased the concentration of total non-EAA. Mammary plasma flow increased with GG and was not affected by LG or protein level. Uptake and clearance of total EAA and group 2 AA were affected or tended to be affected by GG × AA interactions, with their uptakes being lower and their clearances higher with GG, but only at the LMP level. Infusion of LG did not affect uptake or clearance of any AA group. The HMP level increased uptake and decreased clearance of all EAA groups and decreased non-EAA uptake. Infusion of GG tended to increase mammary glucose uptake, and tended to decrease BHB uptake only at the LMP level. Infusion of LG increased mammary uptake of TAG and LCFA and increased or tended to increase clearance of TAG and LCFA. We suspect GG increased mammary plasma flow to maintain intramammary energy and AA balance and stimulated lipogenesis in adipose, accounting for depressed arterial BHB and group 2 AA concentrations. Mammary glucose uptake did not cover estimated requirements for lactose and fat synthesis at the HMP level, except during HMP-GG infusion. Results of this study illustrate flexibility in mammary metabolite utilization when absorptive supply of glucogenic, lipogenic, and aminogenic substrate is increased.

Energy and nitrogen partitioning in dairy cows at low or high metabolizable protein levels is affected differently by postrumen glucogenic and lipogenic substrates

This study tested the effects of energy from glucogenic (glucose; GG) or lipogenic (palm olein; LG) substrates at low (LMP) and high (HMP) metabolizable protein levels on whole-body energy and N partitioning of dairy cattle. Six rumen-fistulated, second-lactation Holstein-Friesian dairy cows (97 ± 13 d in milk) were randomly assigned to a 6 × 6 Latin square design in which each experimental period consisted of 5 d of continuous abomasal infusion followed by 2 d of rest. A total mixed ration consisting of 42% corn silage, 31% grass silage, and 27% concentrate (dry matter basis) was formulated to meet 100 and 83% of net energy and metabolizable protein requirements, respectively, and was fed at 90% of ad libitum intake by individual cow. Abomasal infusion treatments were saline (LMP-C), isoenergetic infusions (digestible energy basis) of 1,319 g/d of glucose (LMP-GG), 676 g/d of palm olein (LMP-LG; major fatty acid constituents are palmitic, oleic, and linoleic acid), or 844 g/d of essential AA (HMP-C), or isoenergetic infusions of 1,319 g/d of glucose + 844 g/d of essential AA (HMP-GG) or 676 g/d of palm olein + 844 g/d of essential AA (HMP-LG). The experiment was conducted in climate respiration chambers to determine energy and N balance in conjunction with milk production and composition, nutrient digestibility, and plasma constituents. Infusion of GG and LG decreased dry matter intake, but total gross energy intake from the diet plus infusions was not affected by GG or LG. Furthermore, GG or LG did not affect total milk, protein, or lactose yields. Infusing GG or LG at the HMP level did not affect milk production differently than at the LMP level. Infusion of GG stimulated energy retention in body tissue, increased plasma glucose and insulin concentrations, decreased lipogenic metabolites in plasma, and decreased milk fat yield and milk energy output. Nitrogen intake decreased and milk N efficiency increased in response to GG, and N retention was not affected. Infusion of LG tended to increase metabolizable energy intake, increased milk fat yield and milk energy output, increased plasma triacylglycerides and long-chain fatty acid concentrations, and had no effect on energy retention. Infusion of LG decreased N intake but did not affect milk N efficiency or N retention. Compared with the LMP level, the HMP level increased dry matter intake, gross and metabolizable energy intake, and total milk, fat, protein, and lactose yields. Milk energy output increased at the HMP level, and protein level did not affect total energy retention. Heat production increased at the HMP level, but only when GG and LG were infused. The HMP level increased N intake, milk N output, and plasma urea concentration, tended to increase N retention, and decreased milk N efficiency. Regardless of protein level, GG promoted energy retention and improved milk N efficiency, but not through increased milk protein yield. Infusion of LG partitioned extra energy intake into milk and had no effect on milk N efficiency.

Investigating Common Carp (Cyprinus carpio) as a Novel Feed Ingredient for Diets of Farmed Carnivorous Fish

Over 60% of natural fish stocks are either fully‐exploited or overexploited. This declining productivity has led to the rapid growth of the aquaculture industry, or the farming of fish. All fish require a certain level of protein from marine sources, most often provided in the form of fishmeal. Fishmeal is produced using species from the low end of the food chain, such as menhaden or sardine, which usually have low market value. Carnivorous species, such as salmon and trout, are particularly popular in Western markets, but also demand relatively more wild inputs than omnivores/herbivores. While species of the latter, such as carp and catfish, are popular in Asia, they maintain low commercial value in North America. Carp was thus investigated as a source of fishmeal for the growth of a carnivorous species, Rainbow Trout (Oncorhynchus mykiss). Fish were grown in three separate treatment groups, each being fed either a commercial sinking pellet, a unique pellet with commercial herring meal, or a unique pellet with carp meal. Upon determination of crude protein and energy content of the carp meal, diets were balanced on a crude protein and digestible energy basis. Pellets were made using a meat grinder. Trout were fed pellets with an increasing carp meal:herring meal ratio, and palatabilty was determined using the amount of pellets consumed (g) per mean mass of rainbow trout group (g).

Enteric Methane Conversion Factor for Dairy and Beef Cattle: Effects of Feed Digestibility and Intake Level

Abstract. The objectives of this study were to identify the sources of variations in reported methane (CH4) conversion factor (Ym) for dairy and beef cattle through a meta-analytical approach, and to specifically investigate the effects of feed digestibility and intake level on Ym, as well as the alternative expression of methane conversion factor on a digestible energy basis (Dm). Results from 89 peer-reviewed journal articles published from 1992 to 2015 were compiled, and data across studies were analyzed statistically using the MIXED procedures of SAS. For housed cattle, Ym increased significantly with forage-to-concentrate ratio of feed and was also affected by breed. For grazing cattle, Ym varied by geographic region. The observed effect of forage-to-concentrate ratio of feed for housed cattle and the effect of geographic region for grazing cattle on enteric CH4 emissions could both be related to the effect of feed digestibility. Dm was affected significantly by both energy intake level and energy digestibility of feed as well as their interaction. Higher energy digestibility of feed and higher energy intake level of cattle resulted in a lower percentage of digestible energy intake being converted to CH4. Results of this study improved estimation of CH4 conversion factor according to animal husbandry practices. Compared with the Ym approach, the use of CH4 conversion factor on a digestible energy basis can better represent the large variation among diets and the effects of different dietary emission mitigation strategies.

Ammonia and Methane Emission Factors from Cattle Operations Expressed as Losses of Dietary Nutrients or Energy

The objective of this study was to conduct a systematic review of published literature on ammonia (NH3) and enteric methane (CH4) emissions from beef and dairy cattle operations to obtain statistically representative emission factors based on dietary intakes of nutrients or energy, and to identify major causes of emission variations. NH3 emissions from lagoon or other manure storage facilities were not included in this review. The NH3 and CH4 emission rates, expressed as a percentage losses of dietary nutrients or energy, demonstrated much less variation compared with emission rates expressed in g/animal/day. Air temperature and dietary crude protein (CP) content were identified as two major factors that can affect NH3 emission rates in addition to farm type. Feed digestibility and energy intake were identified as two major factors that can affect CH4 emission rates expressed as a percentage losses of dietary energy. Generally, increasing productivity and feed efficiency represented the greatest opportunity for mitigating NH3 or CH4 emissions per unit of livestock product. Expressing CH4 loss on a digestible energy basis rather than a gross energy intake basis can better represent the large variation among diets and the effects of varying dietary emission mitigation strategies.

Feeding increasing levels of corn gluten meal induces suboptimal muscle pigmentation of rainbow trout (Oncorhynchus mykiss)

A 24-week growth trial was conducted to evaluate the effects of feeding levels of corn gluten meal (CGM) on growth performance and pigment deposition in the muscle of rainbow trout (Oncorhynchus mykiss). Three isonitrogenous and isoenergetic (digestible energy basis) experimental diets were formulated to contain increasing levels of CGM (0%, 9% and 18%) and 50 mg kg � 1 of astaxanthin. Each diet was fed in triplicate to groups of 75 fish (initial average body weight = 549 g fish � 1 ) reared at 8.5°C. The inclusion of CGM did not significantly (P > 0.05) affect final body weight, thermal growth efficiency (TGC) or feed efficiency. Carotenoid concentration determined by liquid chromatography showed a significant (P < 0.05) linear reduction in the concentration of one astaxanthin isomer, all-trans astaxanthin and all-trans lutein in the muscle of fish in response to increasing levels of CGM. Tristimulus colour analysis of the muscle showed a significant (P < 0.05) linear reduction in a* (redness) and C*ab (chroma). Salmofan TM score showed a significant (P < 0.05) linear and quadratic reduction in response to increasing levels of CGM. In conclusion, the inclusion of CGM up to 18% does not significantly impact growth performance of rainbow trout. However, the concentration of all-trans astaxanthin as well as the expression of important colour attributes of the muscle can be negatively affected at levels exceeding 9% of CGM in the diet. More research on this topic is needed to discern the mechanism(s) behind the negative effects of dietary CGM and/or its intrinsic yellow pigments on muscle pigmentation of rainbow trout.

The protein requirement of brown trout ( Salmo trutta) fry

The protein requirement of brown trout of INRA DC 87 strain was studied by feeding diets containing graded levels of protein. These diets were formulated to be isoenergetic on a digestible energy basis and contained protein from 38 to 65%. The fish were 1.15 g triploid fry reared in stream water. Triplicates of 300 fish per replicate were used for each diet. The fish were fed for 52 days a ration which was modified every 2 weeks according to biomass, but the actual overall ration corresponded to excess feeding. Proximate analyses were performed on whole body and epaxial muscle at the end of the trial. No significant growth improvement was obtained over 53% protein, while best feed efficiency was apparently observed with 57% protein. The lower the dietary protein, the better the nitrogen utilization (estimated by protein efficiency ratio or productive protein value). Body protein content was not related to dietary protein but low protein levels resulted in higher body lipid content. Essential free amino acid contents in the muscle were plotted against the dietary protein levels and the values of the protein level corresponding to the slope changes were compared with the estimations of the dietary requirement. One free amino acid (threonine) showed a slope changing point corresponding to the values of the requirement determined with specific growth rate, while two other amino acids (arginine and valine) led to values lower than the estimated requirement. Estimations of the absolute requirements in g protein per fish per day or g protein per 100 g fish per day were not accurate because of poor control of the actual feed intake. The optimal protein level of brown trout determined under these conditions seems to exceed that of the salmonids of the genus Oncorhynchus, but it could be similar to that of Salmo salar.

Responses of Blood Glucose, Insulin and Cortisol Concentrations to Common Equine Diets

Two experiments were conducted to determine the response of blood glucose, insulin and cortisol levels to four common equine diets. Experiment 1 was designed to determine the diurnal variation of glucose and two glucoregulatory hormones, insulin and cortisol, in four fasting geldings. No diurnal variation was observed in either glucose or insulin levels during the 24-h sampling period. However, cortisol levels did exhibit a circadian rhythm, with elevated values observed in the morning and low values in the evening. Experiment 2 investigated the response of glucose, insulin, cortisol and selected amino acids to four isoenergetic equine diets. Four 2-yr-old quarter horse geldings were used in a Latin square design. Pelleted isoenergetic diets were composed as follows on a digestible energy basis: 100% alfalfa (diet A), 50% alfalfa and 50% corn (diet AC), 100% corn (diet C) and 90% corn and 10% corn oil (diet CO). A single meal was fed after an overnight fast. Blood samples were taken via a jugular catheter from 0800 to 1700 h. Analysis of variance by repeated measures and mean response area for glucose showed no difference between diets. However, postprandial peak glucose levels were elevated (P less than 0.01) over prefeeding levels in diets AC and C. Analysis of variance by repeated measures and mean response area for insulin showed differences (P less than 0.05) between diets. Cortisol showed no meal-related responses to any of the diets within its expected circadian rhythm.

COMPARISON OF LOW GLUCOSINOLATE-LOW ERUCIC ACID RAPESEED MEAL (CV. TOWER), COMMERCIAL RAPESEED MEAL AND SOYBEAN MEAL AS SOURCES OF PROTEIN FOR STARTING, GROWING AND FINISHING PIGS AND YOUNG RATS

Eighty 3- to 4-wk-old crossbred pigs averaging 5.3 kg in weight at allotment were fed experimental diets during starting, growing and finishing phases to compare Tower rapeseed meal (00-RSM) and commercial rapeseed meal (C-RSM) as the sole or partial replacements for soybean meal (SBM). Barley and wheat were the main energy sources with varying amounts of animal tallow to provide isocaloric diets on a digestible energy basis. A 50/50 isonitrogenous combination of 00-RSM + SBM resulted in feed intake, daily gain and feed/gain ratio similar to results with pigs fed SBM as the sole protein supplement during the three phases. Complete substitution of SBM by 00-RSM resulted in reduction (P &lt;.05) of feed intake during the starting phase as well as lower (P &lt;.05) daily gain and inferior (P &lt;.05) feed/gain ratio during the growing phase. Partial substitution of C-RSM for SBM resulted in reduction (P &lt;.05) of feed intake during the starting and finishing phases. Complete replacement of SBM with C-RSM resulted in a depression (P &lt;.05) of daily gain during all three phases of the experiment, inferior feed/gain ratio during the starting and growing phases compared with pigs fed the other four diets and lower (P &lt;.05) feed intake during the starting and finishing phase compared with pigs fed the SBM diet. These findings were confirmed in a rat experiment. Carcass characteristics of pigs were not greatly affected by experimental treatments. A trend of lower digestibility of energy, nitrogen and amino acids was noted by complete replacement of SBM with either source of RSM in the pig and the rat experiments.

Nutritional status and intake regulation in sheep. VII.* Control of voluntary intake of three diets and the responses to intraruminal feeding

In six experiments, sheep were fed ad libitum on either chopped lucerne hay, chopped wheaten straw, or a ground, pelleted lucerne hay/barley diet. On each diet either the dietary material itself, a more highly digestible material, or sawdust was introduced per fistulam into the reticulorumen in amounts equal to c. 25% of the normal daily intake by weight. For each diet, with intraruminal additions on a single occasion only, the most accurate adjustments of oral intake on a weight or a digestible energy basis were observed when the diet itself was added. On the pellet diet, reduction of oral intake was most rapid and of greater magnitude when materials of high digestibility were introduced, though intake was also reduced when sawdust was introduced. On the chopped lucerne hay diet and on the chopped wheaten straw diet, oral intake was depressed more after the introduction of materials of lower digestibility. When pellets were introduced into animals fed on chopped wheaten straw, oral intake was at first reduced but subsequently increased, which indicated an interaction between the basal diet and the supplement. In longer-term experiments, daily introduction per fistularn of the dietary material at c. 25% of the mean daily intake resulted in a rapid decrease in oral intake of each diet. The decreases in intake, expressed as a percentage of the weight of diet added per fistulam (response index), were 95–115% (pellets), 60–80% (lucerne hay), and 76–104% (wheaten straw), and generally became greater with time. With the pellet diet, trends in intake with time showed an increasingly greater adjustment to materials of high digestibility, and an apparent accommodation or compensation for imposition of a load of indigestible material. Such compensation for indigestible material was not apparent on the two all-roughage diets. Introduction of lucerne/barley pellets into the rumen of sheep fed on chopped wheaten straw resulted in no change, or a slight increase, in straw consumption, and an overall increase in intake of digestible dry matter. In two further experiments a bladder, expanded with water to volumes of 1,2, or 3 litres, caused significant decreases in intake of both the pellet diet and the chopped wheaten straw diet, effects being more rapid and more drastic in the case of the wheaten straw diet. Although there was subsequently a partial recovery of oral intake with the pellet diet, no such apparent compensation occurred with the wheaten straw diet. The results indicate that sensitivity to indigestible material can limit the intake of roughage even though the digesta content of the reticulorumen is not at a maximum, and confirm that important relationships exist between the nutritive value of the diet or nutritional status of the animal and the ability to accommodate indigestible material. ____________________ *Part VI, Aust. J. Agric. Res., 21: 735 (1970).