Growth and feed utilization in two strains of gibel carp, Carassius auratus gibelio: paternal effects in a gynogenetic fish

Gibel carp ( Carassius auratus gibelio Bloch) is a natural gynogenetic fish which requires sperm of the same or related species to activate egg development. The eggs of one gibel carp were divided into two batches. One batch was 'fertilized' with sperm from gibel carp (strain DD), and the other 'fertilized' with sperm from red common carp ( Cyprinus carpio red variety) (strain DR). The juveniles were transferred to the laboratory 36 days post-hatch. Triplicate groups of each strain were fed a formulated diet at either 3% or satiation ration for 8 weeks. At both the restricted and satiation rations, specific growth rate was significantly higher in strain DR than in strain DD. At the 3% ration, there was no significant difference in feeding rate or feed conversion efficiency between the two strains. At the satiation ration, strain DR had a significantly lower feeding rate but higher feed conversion efficiency than strain DD. At the satiation ration, strain DR had a significantly lower intake protein, but higher recovered protein than strain DD. There was no significant difference in faecal protein loss between the two strains. At the 3% ration, strain had no significant effects on intake protein, faecal protein or recovered protein. Neither faecal energy loss nor recovered energy was affected by strain or ration. At both the 3% and satiation ration, final body contents of dry matter and lipid were significantly lower in strain DR than strain DD, while there was no significant difference in protein and energy content between the two strains at either ration level. The results suggested that gibel carp 'fertilized' with sperm of common carp grew faster than those 'fertilized' with sperm of gibel carp through increased feed conversion efficiency and protein retention.     

Theoretical effects of feed composition, feed conversion and feed spillage on waste discharge in fish culture

Based on feed composition, fish composition and feed conversion, some theoretical effects of feeding on waste discharge are calculated to illustrate the appropriateness of farm effluent monitoring. The effects of feed conversion and feed spillage and feed composition on waste discharge (suspended and dissolved N, P & COD) are demonstrated. Slight variations in feed conversion at the moment of sampling, especially those evoked by feed spillage, have tremendous consequences for discharge values. It appears crucial to determine whether observed conversions are explained by inherent efficiencies of fish growth, or whether higher growth efficiencies are combined with feed spillage. Therefore, thorough knowledge of relationships between nutrient intake and growth should be applied to effluent assessment. A calculation is presented to serve as a preliminary assessment of the impacts of these variables on water quality monitoring. The concept is illustrated using measurements from a recirculation pilot eel culture system.     

Re-defining efficiency of feed use by livestock

Livestock, particularly ruminants, can eat a wider range of biomass than humans. In the drive for greater efficiency, intensive systems of livestock production have evolved to compete with humans for high-energy crops such as cereals. Feeds consumed by livestock were analysed in terms of the quantities used and efficiency of conversion of grassland, human-edible ('edible') crops and crop by-products into milk, meat and eggs, using the United Kingdom as an example of a developed livestock industry. Some 42 million tonnes of forage dry matter were consumed from 2008 to 2009 by the UK ruminant livestock population of which 0.7 was grazed pasture and 0.3 million tonnes was conserved forage. In addition, almost 13 million tonnes of raw material concentrate feeds were used in the UK animal feed industry from 2008 to 2009 of which cereal grains comprised 5.3 and soyabean meal 1.9 million tonnes. The proportion of edible feed in typical UK concentrate formulations ranged from 0.36 for milk production to 0.75 for poultry meat production. Example systems of livestock production were used to calculate feed conversion ratios (FCR - feed input per unit of fresh product). FCR for concentrate feeds was lowest for milk at 0.27 and for the meat systems ranged from 2.3 for poultry meat to 8.8 for cereal beef. Differences in FCR between systems of meat production were smaller when efficiency was calculated on an edible input/output basis, where spring-calving/grass finishing upland suckler beef and lowland lamb production were more efficient than pig and poultry meat production. With the exception of milk and upland suckler beef, FCR for edible feed protein into edible animal protein were >1.0. Edible protein/animal protein FCR of 1.0 may be possible by replacing cereal grain and soyabean meal with cereal by-products in concentrate formulations. It is concluded that by accounting for the proportions of human-edible and inedible feeds used in typical livestock production systems, a more realistic estimate of efficiency can be made for comparisons between systems.     

Genetic parameters for performance,feed efficiency,and carcass traits in Senepol heifers

Improving feed efficiency is a key breeding goal in the beef cattle industry. In this study, we estimated the genetic parameters for feed efficiency and carcass traits in Senepol cattle raised in tropical regions. Various indicators of feed efficiency [gain to feed ratio (G:F), feed conversion ratio (FCR), residual weight gain (RG), residual intake and body weight gain (RIG), and residual feed intake (RFI)] as well as growth [final BW, average daily gain (ADG), and DM intake (DMI)], and carcass [rib-eye area (REA), backfat thickness (BF), intramuscular fat score, and carcass conformation score] traits were included in the study. After data editing, records from 1 393 heifers obtained between 2009 and 2018 were used for the analyses. We fitted an animal model that included contemporary group (animals from the same farm that were evaluated in the same test season) as the fixed effect, and a linear effect of animal age at the beginning of the test as a covariate; in addition to random direct additive genetic and residual effects. The (co)variance components were estimated by Bayesian inference in uni- and bivariate analyses. Our results showed that feed efficiency indicators derived from residual variables such as RG, RIG, and RFI can be improved through genetic selection (h² = 0.14 ± 0.06, 0.13 ± 0.06, and 0.20 ± 0.08, respectively). Variables calculated as ratios such as G:F and FCR were more influenced by environmental factors (h² = 0.08 ± 0.05 and 0.09 ± 0.05), and were, therefore, less suitable for use in breeding programs. The traits with the greatest and impact on genetic progress in feed efficiency were ADG, REA, and BF. The traits with the greatest and least impact on growth and carcass traits were RG and RFI, respectively. Selection for feed efficiency will result in distinct overall effects on the growth and carcass traits of Senepol heifers. Direct selection for lower RFI may reduce DMI and increase carcass fatness at the finishing stage, but it might also result in reduced growth and muscle deposition. Residual BW gain is associated with the highest weight gain and zero impact on REA and BF, however, it is linked to higher feed consumption. Thus, the most suitable feed efficiency indicator was RIG, as it promoted the greatest decrease in feed intake concomitant with faster growth, with a similar impact on carcass traits when compared to the other feed efficiency indicators.     

Effects of feed restriction on growth performance,lipid mobilization,and gene expression in rose spotted snapper (Lutjanus guttatus)

The effects of feed deprivation were evaluated for 1 week and 2 weeks in Lutjanus guttatus juveniles. A significant reduction in body mass was observed in both feed deprivation schemes, as well as in hepatosomatic, viscerosomatic and mesenteric fat indexes. The composition of fasted fish was characterized by a decrease in lipid content; the liver displayed an intense reduction of lipid reserves in both fasted groups, and increased expression of the lysosomal acid lipase. 1 week after re-feeding, both experimental groups showed an increase in specific growth rate, feed intake and feed conversion ratio. A recovery in hepatic lipid reserves was observed, and the expression of the lysosomal acid lipase decreased, although lipid content in both groups was still significantly lower than in control groups. Hepatic expression of the growth hormone receptor decreased after fasting, and remained low even after the fish were fed, whereas the expression of insulin-like growth factor 1 and 2 increased after fasting and decreased in both groups when fish were fed again. Altogether, these results showed a partial compensatory growth response in L. guttatus juveniles after fasting, with enhanced growth rates and improved feed efficiency. Fish used stored lipid reserves as the main energy source, and the expression of growth-related and lipid mobilization marker genes in the liver showed similar patterns in both fasting schemes. Based on the results, we suggest as much as 1-week fasting intervals during grow-out programmes to reduce visceral fat and increase growth rate in this species.

     

The genetic parameters of feed efficiency and its component traits in the turkey (Meleagris gallopavo)

Residual feed intake (RFI) and feed conversion ratio (FCR) can be incorporated into a breeding program as traits to select for feed efficiency. Alternatively, the direct measures used to calculate RFI and FCR can be analyzed to determine the underlying variation in the traits that impact overall efficiency. These constituent traits can then be appropriately weighted in an index to achieve genetic gain. To investigate feed efficiency in the turkey, feed intake and weight gain were measured on male primary breeder line turkeys housed in individual feeding cages from 15 to 19 weeks of age. The FCR and RFI showed moderate heritability values of 0.16 and 0.21, respectively. Feed intake, body weight, and weight gain were also moderately heritable (0.25, 0.35, and 0.18, respectively). Weight gain was negatively correlated to feed conversion ratio and was not genetically correlated to RFI. Body weight had a small and positive genetic correlation to RFI (0.09) and FCR (0.12). Feed intake was positively genetically correlated to RFI (0.62); however, there was no genetic correlation between feed intake and FCR. These estimates of heritability and the genetic correlations can be used in the development of an index to improve feed efficiency and reduce the cost of production.     

Effect of group size on feed intake, growth and feed efficiency of juvenile perch

Feed intake, growth and feed efficiency of juvenile perch Perca fluviatilis were significantly affected by group size, with fish in groups of 12 having lower feed intake, higher growth and higher feed efficiency than solitary individuals. The same trend was seen for fish in groups of 12 compared to fish in groups of four, and for fish in groups of four compared to solitary individuals, although the differences were not always significant. The high growth and low feed efficiency for fish in groups may be caused by benefits obtained from shoaling such as reduced levels of stress.     

Identification of polymorphisms influencing feed intake and efficiency in beef cattle

Feed efficiency is an economically important trait in beef cattle. Net feed efficiency, measured as residual feed intake (RFI), is the difference between actual feed intake and the predicted feed intake required for maintenance and gain of the animal. SNPs that show associations with RFI may be useful quantitative trait nucleotides for marker-assisted selection. This study identified associations between SNPs underlying five RFI QTL on five bovine chromosomes (BTA2, 5, 10, 20 and 29) with measures of dry matter intake (DMI), RFI and feed conversion ratio (FCR) in beef cattle. Six SNPs were found to have effects on RFI (P < 0.05). The largest single SNP allele substitution effect for RFI was -0.25 kg/day located on BTA2. The combined effects of the SNPs found significant in this experiment explained 6.9% of the phenotypic variation of RFI. Not all the RFI SNPs showed associations with DMI and FCR even though these traits are highly correlated with RFI (r = 0.77 and r = 0.62 respectively). This shows that these SNPs may be affecting the underlying biological mechanisms of feed efficiency beyond feed intake control and weight gain efficiency. These SNPs can be used in marker-assisted selection but first it will be important to verify these effects in independent populations of cattle.     

Effect of a sprint training protocol on growth rate, conversion efficiency, food consumption and body composition of rainbow trout, Salmo gairdneri Richardson

Rainbow trout were sprint-trained (30 s duration) once or twice on alternate days for a period of 6 weeks. Swim speed for the first 10 s of a training bout averaged 11.4 bls for group 2 (trained once) and 10.2 bl s ⁻¹ for group 3 (trained twice). Food consumption, growth rate and conversion efficiency were measured over 2-week periods. Food consumption was 31-38% less for the trained groups than for the control group (group 1). The growth rates of control and trained fish increased gradually over the training period. The growth rate of trained fish was always significantly less (48-81%) than that of control fish. Although conversion efficiency was significantly less for group 3 at the beginning of training, no other significant differences in conversion efficiency were recorded. Maintenance rations were high in the initial period for all groups, but were lower than the initial values in the second and third periods. While condition factor was significantly lower for the trained groups, there were no differences in percent tissue protein, lipid, or moisture.     

Selection for efficiency of feed utilization in growing mice

Summary Selection was practised for improved feed efficiency (gain/feed intake) of mice on two alternative feeding regimes. In one set of lines animals were fed ad libitum, in the other set they were individually fed a fixed amount of feed (about 10% below the control ad libitum intake) which was not changed over generations. For each treatment, a pair of replicate lines (E) were selected on efficiency from 3–5 weeks of age for 8 generations and another pair (L) from 5–7 weeks for 7 generations. A control line was maintained for both E and L lines. In terminal generations mice from each line were tested on each feeding regime, and carcasses of ad libitum fed mice were analysed.The realized heritability (within families) for efficiency averaged 13%, without much variation over treatments. In the E lines efficiency increased by about 18% of the control mean and in the L lines by about 60%, although absolute changes were small, and responses were similar on the two feeding regimes. Weights at the start of test decreased in the E lines and increased in the L lines; weights at the end of test increased in both.When tested on the alternative regimes, no interactions were detected for live weights, weight gains or efficiency; selection under fixed intake led to the same increase in appetite as did that under ad libitum.There were no interactions for carcass composition. Selection for efficiency led to an increase in fatness on both selection regimes and both weight ranges.