Higher Digestible Energy Research Articles

Transcriptomic Profiling of Spleen in Grass-Fed and Grain-Fed Angus Cattle

The grass-fed cattle obtain nutrients directly from pastures containing limited assimilable energy but abundant amount of fiber; by contrast, grain-fed steers receive a diet that is comprised mainly of grains and serves as an efficient source of high-digestible energy. Besides energy, these two types of diet differ in a large number of nutritional components. Additionally, animals maintained on rich-energy regimen are more likely to develop metabolic disorders and infectious diseases than pasture raised individuals. Thus, we hypothesize that spleen–a relevant immune organ–may function differently under disparate regimes. The objective of this study was to find the differentially expressed genes in the spleen of grass-fed and grain-fed steers, and furtherly explore the potential involved biopathways. Through RNA sequencing (RNA-Seq), we detected 123 differentially expressed genes. Based on these genes, we performed an Ingenuity Pathway Analysis (IPA) and identified 9 significant molecular networks and 13 enriched biological pathways. Two of the pathways, Nur77 signaling in T lymphocytes and calcium-induced T lymphocyte apoptosis which are immune related, contain a pair of genes HLA-DRA and NR4A1 with dramatically altered expression level. Collectively, our results provided valuable insights into understanding the molecular mechanism of spleen under varied feeding regimens.

Ruminal Transcriptomic Analysis of Grass-Fed and Grain-Fed Angus Beef Cattle.

Beef represents a major diet component and one of the major sources of protein in human. The beef industry in the United States is currently undergoing changes and is facing increased demands especially for natural grass-fed beef. The grass-fed beef obtained their nutrients directly from pastures, which contained limited assimilable energy but abundant amount of fiber. On the contrary, the grain-fed steers received a grain-based regime that served as an efficient source of high-digestible energy. Lately, ruminant animals have been accused to be a substantial contributor for the green house effect. Therefore, the concerns from environmentalism, animal welfare and public health have driven consumers to choose grass-fed beef. Rumen is one of the key workshops to digest forage constituting a critical step to supply enough nutrients for animals’ growth and production. We hypothesize that rumen may function differently in grass- and grain-fed regimes. The objective of this study was to find the differentially expressed genes in the ruminal wall of grass-fed and grain-fed steers, and then explore the potential biopathways. In this study, the RNA Sequencing (RNA-Seq) method was used to measure the gene expression level in the ruminal wall. The total number of reads per sample ranged from 24,697,373 to 36,714,704. The analysis detected 342 differentially expressed genes between ruminal wall samples of animals raised under different regimens. The Fisher’s exact test performed in the Ingenuity Pathway Analysis (IPA) software found 16 significant molecular networks. Additionally, 13 significantly enriched pathways were identified, most of which were related to cell development and biosynthesis. Our analysis demonstrated that most of the pathways enriched with the differentially expressed genes were related to cell development and biosynthesis. Our results provided valuable insights into the molecular mechanisms resulting in the phenotype difference between grass-fed and grain-fed cattle.

Towards integrated biorefinery from dried distillers grains: Evaluation of feed application for Co-products

In this paper, we presented an integrated C5-based biorefinery concept to produce C5-platform of biofuels and biochemicals using corn fiber from Dried Distillers Grains (DDG). The process utilizes a selective hydrolysis process to generate a xylose-rich hydrolyzate stream and two co-product streams: fine fraction generated during mechanical pretreatment of DDG using Mesh 20 sieve and residual fiber after hydrolysis. Utilization of these two co-product streams is critical to the success of the biorefinery. This paper discusses how the two streams are generated, their composition, and their potential value in animal feed applications. Composition analysis of the first co-product stream showed that it is enriched in proteins compared to original DDG (11% higher crude protein content; 36% higher lysine content). The second co-product stream has 113% higher fat content compared to original DDG, as well as 15% higher total digestible nutrients, and 15% higher digestible energy. The results of this study suggest that these co-product side streams can be potentially applied as additives in animal feed, allowing for cost-effective utilization of DDG for bio-products without negatively impacting feed markets associated with DDG.

Productive performance of juvenile Patagonian red octopus (Enteroctopus megalocyathus) fed with fresh preys: are relevant the quantity of protein and energy on diets?

This study was conducted to investigate if the productive performance of Patagonian red octopus (Enteroctopus megalocyathus) is related to the quantitative contents of protein and energy of fresh diets based in marine preys. Six diets with P/E ratios of 35 (100% crab = C100), 41 (100% fish = F100), 44 (25% squid and 75% fish = S25:F75), 46 (50% squid and 50% fish = S50:F50), 48 (75% squid and 25% fish = S75:F25) and 51 (100% squid = S100) g protein MJ−1 during 83 days were evaluated in octopuses weighing 297 ± 120 g. The growth and body biochemistry of the octopuses were not affected by the diets, however, food and lipid intake were affected, with crab diet obtaining the highest intake in both cases. The higher values of dry matter digestibility were achieved in S100 and S50:F50 diets, the highest protein digestibility was obtained with S100 and C100 diets, while the highest energy digestibility was achieved by diet S75:F25 and F100. Feed efficiency varied between the diets and protein/energy ratio alone explained 82.8% of the total variance. Besides, octopus fed F100 and C100 showed the highest body protein deposition. So, although it had no significant differences in growth and survival between the different diets, the feed efficiency and nitrogen deposition changed in relation with the protein/energy ratio of fresh diets. It is discussed that is possible to maintain growth of octopuses and to improve the feed efficiency and protein deposition parameters by optimizing the P/E values of diet.

Short Communication: Energy values and apparent total tract digestibility coefficients of copra meal and palm kernel meal fed to growing pigs

Jang, Y. D. and Kim, Y. Y. 2013. Short Communication: Energy values and apparent total tract digestibility coefficients of copra meal and palm kernel meal fed to growing pigs. Can. J. Anim. Sci. 93: 517–521. To determine energy values and coefficients of apparent total tract digestibility (CATTD) of copra meal (CM) and palm kernel meal (PKM), 24 growing pigs were fed a corn–soybean meal basal diet and the basal diet replaced by 300 g kg−1 of either CM or PKM. Copra meal had higher CATTD of gross energy (12%), dry matter (DM; 13%), neutral detergent fiber (16%), acid detergent fiber (23%), and crude fiber (79%; P<0.05) than PKM. Copra meal had a slightly higher digestible energy (DE) value than PKM (14.08 vs. 13.01 MJ kg−1 DM; P=0.067), but metabolizable energy (ME; 13.33 vs. 12.83 MJ kg−1 DM), net energy (7.97 vs. 7.36 MJ kg−1 DM), and ME:DE ratio did not differ between CM and PKM. Therefore, compared with PKM, CM can be a better source of dietary energy in swine diets as evidenced by higher CATTD of energy and fiber components.

Relating sensory characteristics with biochemical analyses of hays fed to horses

s / Journal of Equine Veterinary Science 33 (2013) 321-399 346 Nutrition: Oral Presentations Relating sensory characteristics with biochemical analyses of hays fed to horses S. Julliand , C. Omphalius , M. Orard , O. Parodi , C. Villot , H. Warren , and V. Julliand 4 1 Lab to Field, France, 2 AgroSupDijon, France, 3 Alltech Bioscience Centre, Ireland, 4 Uranie NCA, AgroSup Dijon, France Forages form the basis of horse diets. However in the field, forage nutritive value calculated from biochemical analyses is not commonly used. Horse people evaluate forage quality as “good” or “bad” based on their own quality indicators. The present study aimed at comparing the nutritive value of hays with their sensory characteristics using a descriptive analysis. Twenty hay buyers (equine breeders, trainers, owners and riding school proprietors) were interviewed. While trainers, owners and riding school proprietors said that they looked firstly at the origin of the hay, breeders focused on timing of harvest. All buyers looked at organoleptic qualities as the second major indicator. Among organoleptic qualities, odour and colour were the most frequent indicators mentioned.Twenty-one meadow hays originating from 12 different administrative regions of France were then collected for sensorial and biochemical analyses. For each hay, 2 kg were randomly hand-sampled from one opened bale in 10 different locations. Part was sent for biochemical analysis and part was used for sensorial analysis.The sensorial descriptive analysis was run in three separate workshops with 54 untrained subjects to sort hays by appearance, odour or texture. Subjects were asked to group hays by similarity of view, smell or touch and then to describe the groups with their own qualifying terms (with a maximum of five terms per group).Multidimensional scaling analyses were carried out in order to provide a hierarchical clustering of hays based on their description similarities and to map each group of hays in correlation with the associated description terms. Appearance was separated into four statistically distinct groups and described as “grassy-dark-green”, “mixedthin”, “heterogenic-medium”, “yellow-strawy-moldy”. Odour characteristics were also separated into four groups: “dry-smell of farm-persistent”, “sweet-pleasant”, “spicyaromatic-flowered”, “unpleasant-acid-moldy-smell of urine”. Texture characteristics were separated into three groups: “matted-long-pleasant-soft-homogeneous”, “un -pleasant-strawy”, “mix-short-lightened”.Hay digestible energy (DE) varied from 1.56 to 2.32 Mcal/kg DM and crude protein (CP) from 63 to 163 g/kg DM.The appearance “grassy-dark-green” group had a higher DE than the “yellow-strawy-moldy” group (p<0.05). Predictive energetic values for “yellow-strawy-moldy” hays were lower (p1⁄40.001) than for “grassy-dark-green” hays (1.7 versus 2.1 Mcal/kg DM, respectively).The odour “sweet-pleasant” group appeared higher than the “unpleasant-acid-moldysmell of urine” group with respect to DE (p<0.05). Predictive energetic values for hays that smell “sweetpleasant” were higher (p1⁄40.005) than for other hays (2.1 versus 1.8 Mcal/kg DM, respectively).No significant difference has been noticed for DE among the texture groups. Additionally, no significant difference in crude protein appeared among the groups.This study shows a link between appearance and odour of hays and their DE, which needs further investigation.

Influence of forage inclusion in the diet on ileal and total tract digestibility

The present investigation aimed to study the ileal and total tract digestibility of 3 forages (clover-grass, clover-grass silage, and field pea (Pisum sativum)-barley (Hordeum vulgare) silage) supplemented to a basal diet. A total of 24 pigs, adapted to eating forages by supplementing a basal feed with clover-grass silage from weaning, were fitted with a T-cannula at the terminal ileum at approximate 30 kg BW. For each of the 3 types of forage, 2 balance trials with a 4 wk interval were carried out. Two pigs in each test were fed the basal diet and 6 others were fed the basal diet plus forage throughout the whole experiment. The intake of forages was low and quite variable and on average accounted for only 10 to 12% of the DMI. Ileal digestibility of protein estimated by collection from the T-cannula was higher (P = 0.031) than the digestibility estimated by the slaughter technique indicating some separation of the digesta collected from the T-cannula. The forages had, as expected, a lower total tract DM and energy digestibility than the basal diet (P < 0.05). The fresh clover-grass had a higher energy digestibility than the 2 silages (60 vs. 48%; P < 0.05). Inclusion of 10% of GE in the diet as forage reduced (P < 0.05) the energy digestibility of the ration by 2.2% for clover-grass, 3.4% for clover-grass silage, and 5.0% for pea-barley silage. In organic slaughter pig production, the overall energy supply from these forages is limited, but they may play an important role in satiety and rooting behavior.

The Effect of a Silage Inoculant on Silage Quality, Aerobic Stability, and Meat Production on Farm Scale

The effect of inoculation on nutrient content, fermentation, aerobic stability, and beef cattle performance for whole-plant corn silage treated with a commercial product (blend of homo- and heterofermentative lactic acid bacteria, BSM, blend of Enterococcus faecium, Lactobacillus plantarum, and Lactobacillus brevis, DSM numbers 3530, 19457, and 23231, resp.), was compared to a control treatment with no silage additives (CT). The material had a DM of 323 g/kg, crude protein, and water-soluble carbohydrate concentrations of 87.9 and 110.5 g/kg DM, respectively. BSM increased the fermentation rate with a significantly deeper pH (P < 0.01), a significant increase in the total organic acids concentration (P < 0.05), more lactic acid (P < 0.01), and numerically more acetic acid compared to CT. BSM significantly decreased the concentrations of butyric acid (P < 0.01), ethanol, and ammonia-N compared to the CT. BSM-treated silage decreased DM by 3.0 % (P < 0.01) and had a higher digestible energy and a higher metabolizable energy concentration by 2.3 (P < 0.01) and 1.00 % (P < 0.05), respectively, compared to untreated silage. Aerobic stability improved by more than 2 days in BSM silage. The DM intake of silage treated with BSM increased by 6.14 %, and improved weight gain and the feed conversion by 8.0 (P < 0.01) and 3.4%.

Characterisation of grain quality in diverse sorghum germplasm using a Rapid Visco-Analyzer and near infrared reflectance spectroscopy

Twenty-two diverse sorghum landraces, classified as normal and opaque types obtained from Ethiopia, were characterised for grain quality parameters using near infra-red spectroscopy (NIRS), chemical and Rapid Visco-Analyzer (RVA) characteristics. Protein content ranged from 77 to 182 g kg(-1), and starch content from 514 to 745 g kg(-1). The NIRS analysis indicated the pig faecal digestible energy range from 14.6 to 15.7 MJ kg(-1) as fed, and the ileal digestible energy range from 11.3 to 13.9 MJ kg(-1) as fed. The normal sorghums had higher digestible energy than the opaque sorghums, which exhibited lower RVA viscosities, and higher pasting temperatures and setback ratios. The RVA parameters were positively correlated with the starch content and negatively correlated with the protein content. The normal and opaque types formed two distinct groups based on principal component and cluster analyses. The landraces were different for the various grain quality parameters with some landraces displaying unique RVA and NIRS profiles. This study will guide utilisation of the sorghum landraces in plant improvement programs, and provides a basis for further studies into how starch and other constituents behave in and affect the properties of these landraces.

Plasma gossypol dynamics in white-tailed deer: Implications for whole cottonseed as a supplemental feed

Whole cottonseed (WCS) is a potential supplemental feed for white-tailed deer ( Odocoileus virginianus) in rangeland conditions because of its high digestible energy and protein content, moderate fiber content, and resistance to degradation in moist conditions. WCS also contains the polyphenolic secondary metabolite gossypol, which reduces palatability to non-target monogastric species but may be of concern for deer nutrition. Plasma gossypol stabilization when fed a constant dry matter intake, plasma gossypol depletion after WCS was removed from the diet, and the relationship between WCS consumption and plasma gossypol concentration was studied in 10 mature male ( N = 5) and female ( N = 5) captive white-tailed deer. Consumption of WCS by 73 free-ranging white-tailed deer (59 males, 14 females) was estimated using results of the captive study. Plasma gossypol concentrations declined exponentially and averaged 0.74 μg/mL 35 days after WCS was removed from the diet. Plasma gossypol concentration was linearly related to WCS consumption ( P < 0.001), with females having 0.35 μg/mL greater ( P = 0.04) plasma gossypol than males for a given rate of dry matter consumption. All female and 93% of male white-tailed deer captured in WCS supplemented pastures had detectable plasma gossypol. Female averaged 1.88 μg/mL of plasma gossypol and males averaged 4.84 μg/mL of plasma gossypol. Based on the captive deer data, these plasma values suggest an average WCS consumption of ∼2.6 g/kg BW/day for female free-ranging deer and ∼5.6 g/kg BW/day for male free-ranging deer. Inferentially, a large proportion of free-ranging white-tailed deer in rangeland conditions will consume WCS, with females consuming 125 g WCS/day and males consuming 428 g WCS/day. That plasma gossypol levels decrease rapidly after cottonseed is removed from the diet suggests that the long withdrawal periods often used prior to breeding season may not be needed. However, although 93% of gossypol was eliminated from the animals after a five-week withdrawal period, a small amount of gossypol can still be detected. While our preliminary data on these animals suggests that these levels are not detriment to animal health or reproduction, ranch managers may want to take a conservative approach to the feeding of WCS until these questions are answered.

FEEDING RYEGRASS HAY TO GROWING RABBITS, A NOTE

Digestibility of ryegrass hay (18% crude protein and 18.9% crude fibre) was determined with 11 three-way crossbred New Zealand x Californian growing rabbits, using a 95% ryegrass diet +2% animal fat and 3% amino-acids, vitamins and minerals. Amino acids composition of diet and of the ryegrass was given. With the same diet, twenty-eight rabbits were used from 42 to 70 days of age to study the growth performance and carcass parameters. The ryegrass hay used in the present work showed high digestible energy (10.3 MJ kg1 DM) and digestible protein (119 g kg1 DM) contents. Average daily gain, feed intake and live weight at 70 days were 36.7 g day1, 111 g DM day-1 and 2042 g, respectively. Sex did not affect any of the carcass values. Weights of full gastrointestinal tract, liver and kidney fat were 504, 73 and 6.9 g. In conclusion, growth rate, feed conversion ratio (3.02 g g-1 DM) and dressing percentage (53.3%) were satisfactory when this high forage diet was used.

Year rather than farming system influences protein utilization and energy value of vegetables when measured in a rat model

The aim of the study was to measure protein utilization and energy value of dried apple, carrot, kale, pea, and potato prepared for human consumption and grown in 2 consecutive years with 3 different farming systems: (1) low input of fertilizer without pesticides (LIminusP), (2) low input of fertilizers and high input of pesticides (LIplusP), (3) and high input of fertilizers and high input of pesticides (HIplusP). In addition, the study goal was to verify the nutritional values, taking into consideration the physiologic state. In experiment 1, the nutritive values, including protein digestibility-corrected amino acid score, were determined in single ingredients in trials with young rats (3-4 weeks) as recommended by the Food and Agriculture Organization of the United Nations/World Health Organization for all age groups. A second experiment was carried out with adult rats to assess the usefulness of digestibility values to predict the digestibility and nutritive value of mixed diets and study the age aspect. Each plant material was included in the diet with protein-free basal mixtures or casein to contain 10% dietary protein. The results showed that variations in protein utilization and energy value determined on single ingredients between cultivation strategies were inconsistent and smaller than between harvest years. Overall, dietary crude fiber was negatively correlated with energy digestibility. The energy value of apple, kale, and pea was lower than expected from literature values. A mixture of plant ingredients fed to adult rats showed lower protein digestibility and higher energy digestibility than predicted. The protein digestibility data obtained using young rats in the calculation of protein digestibility-corrected amino acid score overestimates protein digestibility and quality and underestimates energy value for mature rats. The present study provides new data on protein utilization and energy digestibility of some typical plant foods that may contribute new information for databases on food quality. Growing year but not cultivation system influenced the protein quality and energy value of the vegetables and fruit typical for human consumption.

APPARENT DIGESTIBILITY OF SELECTED FEED INGREDIENTS IN DIETS FOR MUD CRAB (Scylla paramamosain)

Cultured mud crabs (Scylla spp.) are commonly fed with ‘trash’ fish. Insufficient supply, high cost and variable quality of ‘trash’ fish has lead to a need to develop costeffective and environmentally friendly formulated diets. This study was conducted to determine quality of selected feed ingredients as protein sources in mud crab diets based on their nutrient composition and digestibility coefficients for dry matter (ADMD), crude protein, lipid and energy. The digestibility coefficients for ADMD ranged from 82.46% to 89.20%. Animal-based feedstuffs such as shrimp head, tiny shrimp and squid liver meal had higher ADMD values than fish meal. Of the plant-based feedstuffs, soy bean meal had the highest ADMD values (89.20%) and corn gluten had the lowest (82.46%). Corn gluten had the lowest protein digestibility (78.81%) and soy bean meal had the highest (96.05%). The lowest energy digestibility (71.13%) was obtained in corn gluten meal. Soy bean meal had a higher energy digestibility value (98.48%) than fish meal (85.95%). All animal meal sources had similar energy digestibility values (85.86%—92.09%).

Phytoremediation of Anaerobic Digester Effluent for Water Purification and Production of Animal Feed

The application of phytoremediation for purification of an anaerobically treated dairy manure and production of forage crops was investigated. Four crops (two cereals and two grasses) were examined for their ability to grow hydroponically and to remove pollutants (nutrients) from dairy wastewater. The preliminary experiments showed that timothygrass and orchardgrass did not perform well as aquatic plants. Only 24 and 29% of the seeds germinated after 19-21 days giving a crop yield of 21 and 19 t ha-1 for timotygrass and orchardgrass, respectively. Wheat and barley grow very well as aquatic plants with a seed germination of 83 and 73 (in 7 days) and a crop yield of 106 and 86 t ha-1 for wheat and barley, respectively. The effect of light duration, seeding rate, wastewater application rate and fungicidal treatment on the wheat crop yield and pollution potential reduction were studied. The results indicated that with this system, a wheat forage crop could be produced in 21 days from germination to harvest. A treatment combination of wastewater application rate of 900 mL day-1, a seeding rate of 400 g and a light duration of 12 hrs gave the best results for crop yield (3.81 kg of wheat tray-1). Based on thirteen harvests per year, a total possible yield of 3300 t ha-1 per year can be achieved with the system. This is more than 102 times grater than the yield obtainable from a filed grown conventional forage of 245 t ha-1 per year. Wheat had a superior nutritional value (higher digestible energy, higher carbohydrates, fat, protein and mineral contents and less crude fiber) compared to the other field forage crops. It also contained higher macro and micro nutrients (Sodium, Magnesium, Manganese, Iron, Copper, Boron, Selenium, Iodine and Cobalt) than field forage crops. Removal efficiencies of 72.4, 88.6 and 60.8 % can be achieved for the total solids, Chemical Oxygen Demand (COD) and ammonium nitrogen, respectively. A nitrate nitrogen concentration of 7.1 mg L-1 was also found in the effluent from the hydroponic system. This is below the Canadian Environmental and Health Guidelines of 10 mg L-1.

Energy content and digestibility of brine shrimp ( Artemia franciscana) and other prey items of eared grebes ( Podiceps nigricollis) on the Great Salt Lake, Utah

We measured the gross energy of brine shrimp ( Artemia franciscana), brine shrimp cysts, brine flies ( Ephydra spp.), brine fly larva, and corixids ( Trichocorixa verticalis) from the Great Salt Lake (GSL). We estimated the apparent and true digestible energy in eared grebes ( Podiceps nigricollis) for these prey items through feeding trials. We found no difference in energy concentration (kJ/g) between any of the invertebrates except for brine fly larva. Invertebrates from the GSL have a relatively high mean energy concentration ranging from 18.8 kJ/g to 23.9 kJ/g. Eared grebes are able to use 82.2–94.9% of the dry mass and 87.4–89.7% of the gross energy (true digestibility) content of their prey items. The high energy content and digestibility partially explain how an eared grebe can successfully forage on such small prey items on the GSL. In contrast, brine shrimp cysts had a high-energy concentration (23.5 kJ/g), but had the lowest amount of true digestible energy (34% of dry mass and 51% of energy), which helps explain why grebes are rarely observed foraging on them.

Consequences for body composition at farrowing and nutrient partitioning during lactation of a choice-feeding regime during rearing and pregnancy in gilts of different genotypes

The potential conflict between reproductive functions and the drive to deposit body protein may impair productive performance in modern gilts of lean genotype. To study the response of the gilt to this conflict, a choice-feeding experiment was carried out to measure the nutrient intake selected by breeding gilts and responses in reproductive and lactation performance. Using a 2 × 2 factorial design, gilts of two different genotypes (24 of NPD 402, expected higher body protein/lipid ratio (L) or 24 of Camborough 23, expected lower body protein/lipid ratio, (F)) were either choice-fed (C) by offering both a low (120 g crude protein (CP)/kg) and a high protein (218 g CP/kg) feed during rearing and pregnancy or fed conventionally (R) single feeds, ad libitum during rearing and restricted during pregnancy. Choice-fed gilts selected mainly the low protein feed (0.92 of total feed intake) regardless of genotype and had lower protein intakes than R gilts prior to puberty. However, in pregnancy, due to higher feed intakes, C gilts had higher dietary protein and energy intakes than R gilts. C gilts were heavier, and had greater back-fat and eye muscle depth at farrowing than R gilts, but had smaller litter sizes ( P < 0.01). During lactation, dietary treatments were reallocated so that gilts received either a low (LE, maintenance + 45 MJ/day) or a high (HE, maintenance + 67 MJ/day) digestible energy intake. Litter size was standardised within 2 days of farrowing. LE gilts had greater decreases in weight and back-fat and eye-muscle depth during lactation than HE gilts, but dietary lactation treatment had no effect on litter performance. The choice-feeding regime which resulted in heavier gilts with greater back-fat and eye-muscle depth at farrowing did not produce any advantage in terms of partitioning of nutrients towards milk production, as indicated by litter performance, irrespective of gilt genotype. F gilts had greater piglet growth rates than L gilts and also had a higher milk protein concentration. A greater number of L than F gilts failed to complete the experiment for health reasons. Treatment effects on glucose tolerance at day 13 of lactation were not significant. Choice-feeding was therefore not found to be suitable for determining nutrient requirements of modern lean-genotype gilts which would improve reproductive performance.

RELATIVE FORAGING VALUE TO LESSER SCAUP DUCKS OF NATIVE AND EXOTIC CLAMS FROM SAN FRANCISCO BAY

Invasions of exotic invertebrates have greatly altered many aquatic communities, but impacts on the foraging energetics of predators seldom have been assessed. In San Francisco Bay, California (USA), a major community change occurred with introduction of the Asian clam (Potamocorbula amurensis) in 1986. This species now greatly outnumbers the previous clam prey of a variety of sharks, rays, sturgeon, flatfish, and crabs, as well as several diving duck species for which the bay is the most important wintering area on the U.S. Pacific Coast. P. amurensis also accumulates much higher levels of some contaminants than the formerly dominant prey. Because alteration of the food base or contaminated foods on wintering areas may be factors in the population decline of scaup ducks, effects of this exotic invasion are important to assess. For Lesser Scaup (Aythya affinis), we studied effects of differences in nutrient content, digestibility, crushing resistance of shells, areal density, size, and depth in the sediments on the relative foraging value of exotic P. amurensis vs. the formerly dominant native clam Macoma balthica. P. amurensis, including shells, had higher nitrogen and energy content per clam of the same length class, and higher digestibility of energy, than M. balthica. Gut retention time did not differ between clam species, so their relative profitability for scaup was determined mainly by the intake rate of digestible nutrients during short, costly dives. For scaup foraging in an aquarium 1.8 m deep, intake rates (number of prey per second) of food items buried in sand‐filled trays increased with increasing prey density up to at least 4000 prey/m2. For items buried 3 cm deep, intake rates did not differ for prey &lt;6 mm long vs. prey 6–12 mm long; however, intake rates were much lower when prey were deeper in the sediments (6 cm vs. 3 cm). In the field, a much higher percentage of P. amurensis were in the length range most commonly eaten by Lesser Scaup (&lt;12 mm), and unlike M. balthica, almost all P. amurensis were in the top 5 cm of sediments where scaup intake rates are highest. In tensometer measurements, shells of P. amurensis were much harder to crush than shells of M. balthica, which might partly offset the apparent energetic advantages of P. amurensis. In many respects, the exotic P. amurensis appears to be a more valuable food than the native M. balthica for Lesser Scaup. However, because P. amurensis accumulates much higher levels of some contaminants, this exotic invasion increases the risk of toxicity to scaup and a range of other benthic predators.

Evaluating response to selection and nutritional needs in a three‐way cross of rabbits

SummaryAn experiment was carried out to evaluate the response obtained in a three‐way cross of rabbits when the lines involved had undergone within‐line selection for litter size or postweaning daily gain. The interaction between the level of nutrition and genetic level of the crossbreds was also studied. Using frozen embryos, old (H1) and current (H2) crossbred does and young were compared contemporarily. Does were fed a standard diet or a diet having high digestible energy and protein. The difference in the number of generations between lines used to produce both crosses were: 13 or 0 for the maternal lines, and 12 for the paternal line. The traits studied in the crossbred does were: daily feed intake during gestation, during the first 3 weeks of lactation and during the last week before weaning; doe weight at mating and at kindling; litter weight at birth and at weaning; total litter size, number born alive and litter size at weaning. The recorded traits for the young were: individual weight at weaning and at 63 days; individual daily gain after weaning; daily feed intake and feed conversion index. The last two traits were recorded as averages per cage. A total of 1161 litters from 190 does were involved. Significant differences in litter‐size traits, between H1 and H2 does, were observed and were higher than the expected from the within‐line response. The doe effect was not significant for other doe traits, adjusted to a constant litter size. The estimated difference in postweaning daily gain between H1 and H2 young was significant and in favour of H2, but the value was considerably lower than expected. The effect of type of feed and the interaction with the type of doe was not significant for any doe trait. The type of feed consumed by the doe was significant for postweaning daily gain, and the interaction with the type of crossbreds was significant for this trait and for individual weight at 63 days.

Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus L.)

Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso-N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, in a dry and fresh form, was performed. Diets of treatments 1 and 2 included 20% and 40% of duckweed, respectively, in a dry form. In treatments 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40% fresh duckweed providing the same amount of dry matter and protein as in control. The specific growth rates (SGRs) of tilapia were 1.51±0.07, 1.38±0.03, 1.31±0.06, 1.44±0.02 and 1.33±0.05, in control and treatments 1–4. There was no significant difference between SGR for the control diet and the diet with 20% fresh duckweed, while the other treatment groups had significantly lower SGR. All the treatment diets provide good values for feed conversion ratios (FCRs) and protein efficiency ratio (PER). Dry matter of diets ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high PD (88.4–93.9%) and high-energy digestibility (78.1–90.7%). Dry matter of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4 respectively. Protein values were 78.4, 79.9, 77.6 and 75.9, while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4 respectively. Analysis of body composition shows that tilapia fed diets with duckweed contain significantly (P<0.05) higher phosphorus and protein content and significantly (P<0.05) lower lipid content. In contrast, tilapia fed control diet had a significant higher (P<0.05) dry matter content and lower ash content.

The influence of recombinant bovine somatotropin on dietary energy level-related growth of Holstein-Friesian bull calves.

Our objective for this study was to assess the effect of recombinant bovine somatotropin (rbST) in overcoming the biological effects attributed to live weight increase and age on growth and fat deposition in male cattle. Holstein-Friesian bull calves (n = 56; 182.2 +/- 14.7 d old) were allotted to four subtreatments in a randomized complete block with a factorial arrangement of two levels of rbST: 0 and 500 mg of Posilac, every 2 wk, and two dietary metabolizable energy (ME) concentrations: low metabolizable energy (LME) and high metabolizable energy (HME); 10 vs 11.3 MJ/kg DM, respectively. The effect of rbST treatment on daily gain was expressed mostly on the HME diets. The rbST treatment had no effect on the animals fed the LME diets before the age of 240 d was reached. Dry matter intake and the effect of rbST treatment on DM intake were inversely related to the energy concentration of the diet. The degree of fatness of the animals was significantly reduced by rbST treatment and significantly increased by energy concentration of the diet. The major effect of rbST, under the experimental conditions, in regards to adipose tissue deposition, was on the fat depots and not on the intramuscular fat. The concentration of bST, IGF-I, and insulin in the plasma was increased (P < .001) owing to rbST treatment. Lower metabolizable energy supply led to a higher (P < .001) plasma bST concentration, nonsignificantly lower plasma IGF-I and thyroid hormone concentrations, and lower (P < .001) plasma insulin concentration. A trend (P = .065) toward an increase in PUFA was found in the muscle of the rbST-treated and the HME diet animals. At a young age, when the natural growth potential is high, rbST treatment will be efficient only when a diet allowing a high digestible energy intake is provided.