QTLs associated with dry matter intake,metabolic mid-test weight,growth and feed efficiency have little overlap across 4 beef cattle studies

Background

The identification of genetic markers associated with complex traits that are expensive to record such as feed intake or feed efficiency would allow these traits to be included in selection programs. To identify large-effect QTL, we performed a series of genome-wide association studies and functional analyses using 50 K and 770 K SNP genotypes scored in 5,133 animals from 4 independent beef cattle populations (Cycle VII, Angus, Hereford and Simmental × Angus) with phenotypes for average daily gain, dry matter intake, metabolic mid-test body weight and residual feed intake.

Results

A total of 5, 6, 11 and 10 significant QTL (defined as 1-Mb genome windows with Bonferroni-corrected P-value <0.05) were identified for average daily gain, dry matter intake, metabolic mid-test body weight and residual feed intake, respectively. The identified QTL were population-specific and had little overlap across the 4 populations. The pleiotropic or closely linked QTL on BTA 7 at 23 Mb identified in the Angus population harbours a promising candidate gene ACSL6 (acyl-CoA synthetase long-chain family member 6), and was the largest effect QTL associated with dry matter intake and mid-test body weight explaining 10.39% and 14.25% of the additive genetic variance, respectively. Pleiotropic or closely linked QTL associated with average daily gain and mid-test body weight were detected on BTA 6 at 38 Mb and BTA 7 at 93 Mb confirming previous reports. No QTL for residual feed intake explained more than 2.5% of the additive genetic variance in any population. Marker-based estimates of heritability ranged from 0.21 to 0.49 for residual feed intake across the 4 populations.

Conclusions

This GWAS study, which is the largest performed for feed efficiency and its component traits in beef cattle to date, identified several large-effect QTL that cumulatively explained a significant percentage of additive genetic variance within each population. Differences in the QTL identified among the different populations may be due to differences in power to detect QTL, environmental variation, or differences in the genetic architecture of trait variation among breeds. These results enhance our understanding of the biology of growth, feed intake and utilisation in beef cattle.     

Genetic parameters for feed efficiency in Romane rams and responses to single-generation selection

Feeding costs represent one of the highest expenditures in animal production systems. Breeding efficient animals that express their growth potential while eating less is therefore a major objective for breeders. We estimated the genetic parameters for feed intake, feed efficiency traits (residual feed intake (RFI) and feed conversion ratio (FCR)), growth and body composition traits in the Romane meat sheep breed. In these traits, selection responses to single-generation divergent selection on RFI were evaluated. From 2009 to 2016, a total of 951 male lambs were tested for 8 weeks starting from 3 months of age. They were weighed at the beginning and at the end of the testing period. Backfat thickness and muscle depth were recorded at the end of the testing period through ultrasound measurements. Feed intake was continuously recorded over the testing period using the automatic concentrate feeders. The heritability of RFI was estimated at 0.45 ± 0.08, which was higher than the heritability of FCR (0.30 ± 0.08). No significant genetic correlations were observed between RFI and growth traits. A favourable low negative genetic correlation was estimated between RFI and muscle depth (−0.30 ± 0.15), though additional data are needed to confirm these results. The selection of low RFI sires based on their breeding values led to the production of lambs eating significantly less concentrate (3% decrease in the average daily feed intake), but with the same growth as lambs from sires selected based on high RFI breeding values. We concluded that in meat sheep, RFI is a heritable trait that is genetically independent of post-weaning growth and body composition traits. A one-generation divergent selection based on RFI breeding values highlighted that substantial gains in feeding costs can be expected in selection schemes for meat sheep breeds.     

Identifying the limitations for growth in low performing piglets from birth until 10 weeks of age

The evolution of hyper-prolific pig breeds has led to a higher within-litter variation in birth weight and in BW gain during the nursery phase. Based on an algorithm developed in previous research, two populations from a pool of 368 clinically healthy piglets at 6 weeks of age were selected: a low (LP) and a high (HP) performing population and their development was monitored until the end of the nursery phase (10 weeks of age). To understand the cause of the variation in growth between these populations we characterized the LP and HP piglets in terms of body morphology, behaviour, voluntary feed intake, BW gain, and apparent total tract and ileal nutrient digestibility. Piglets were housed individually and were fed a highly digestible diet. At selection, 6 weeks of age, the BW of LP and HP piglets were 6.8±0.1 and 12.2±0.1 kg, respectively. Compared with the LP piglets the HP piglets grew faster (203 g/day), ate more (275 g/day) from 6 to 10 weeks of age and were heavier at 10 weeks (30.0 v. 18.8 kg, all P<0.01). Yet, the differences in average daily gain and average daily feed intake disappeared when compared per kg BW^0.75. Assuming similar maintenance requirements per kg BW^0.75 the efficiency of feed utilization above maintenance was 0.1 g/g lower for the LP piglets (P=0.09).The gain : feed ratio was similar for both groups. LP piglets tended to take more time to touch a novel object (P=0.10), and spent more time eating (P<0.05). At 10 weeks, LP piglets had a higher body length and head circumference relative to BW (P<0.01). Relative to BW, LP had a 21% higher small intestine weight; 36% longer length, and relative to average FI, the small intestinal weight was 4 g/kg higher (both P=<0.01). Apparent total tract and ileal dry matter, N and gross energy digestibility were similar between groups (P>0.10). We concluded that the low performance of the LP piglets was due to their inability to engage compensatory gain or compensatory feed intake as efficiency of nutrient utilization and feed intake per kg BW^0.75 was unaffected. LP piglets tend to be more fearful towards novel objects. The morphological comparisons, increased body length and head circumference relative to BW imply that LP piglets have an increased priority for skeletal growth.     

Whole Genome Association Studies of Residual Feed Intake and Related Traits in the Pig

Background

Residual feed intake (RFI), a measure of feed efficiency, is the difference between observed feed intake and the expected feed requirement predicted from growth and maintenance. Pigs with low RFI have reduced feed costs without compromising their growth. Identification of genes or genetic markers associated with RFI will be useful for marker-assisted selection at an early age of animals with improved feed efficiency.

Methodology/Principal findings

Whole genome association studies (WGAS) for RFI, average daily feed intake (ADFI), average daily gain (ADG), back fat (BF) and loin muscle area (LMA) were performed on 1,400 pigs from the divergently selected ISU-RFI lines, using the Illumina PorcineSNP60 BeadChip. Various statistical methods were applied to find SNPs and genomic regions associated with the traits, including a Bayesian approach using GenSel software, and frequentist approaches such as allele frequency differences between lines, single SNP and haplotype analyses using PLINK software. Single SNP and haplotype analyses showed no significant associations (except for LMA) after genomic control and FDR. Bayesian analyses found at least 2 associations for each trait at a false positive probability of 0.5. At generation 8, the RFI selection lines mainly differed in allele frequencies for SNPs near (<0.05 Mb) genes that regulate insulin release and leptin functions. The Bayesian approach identified associations of genomic regions containing insulin release genes (e.g., GLP1R, CDKAL, SGMS1) with RFI and ADFI, of regions with energy homeostasis (e.g., MC4R, PGM1, GPR81) and muscle growth related genes (e.g., TGFB1) with ADG, and of fat metabolism genes (e.g., ACOXL, AEBP1) with BF. Specifically, a very highly significantly associated QTL for LMA on SSC7 with skeletal myogenesis genes (e.g., KLHL31) was identified for subsequent fine mapping.

Conclusions/significance

Important genomic regions associated with RFI related traits were identified for future validation studies prior to their incorporation in marker-assisted selection programs.     

Genetic and phenotypic correlations among feed efficiency,production and selected conformation traits in dairy cows

The difficulties and costs of measuring individual feed intake in dairy cattle are the primary factors limiting the genetic study of feed intake and utilisation, and hence the potential of their subsequent industry-wide applications. However, indirect selection based on heritable, easily measurable, and genetically correlated traits, such as conformation traits, may be an alternative approach to improve feed efficiency. The aim of this study was to estimate genetic and phenotypic correlations among feed intake, production, and feed efficiency traits (particularly residual feed intake; RFI) with routinely recorded conformation traits. A total of 496 repeated records from 260 Holstein dairy cows in different lactations (260, 159 and 77 from first, second and third lactation, respectively) were considered in this study. Individual daily feed intake and monthly BW and body condition scores of these animals were recorded from 5 to 305 days in milk within each lactation from June 2007 to July 2013. Milk yield and composition data of all animals within each lactation were retrieved, and the first lactation conformation traits for primiparous animals were extracted from databases. Individual RFI over 301 days was estimated using linear regression of total 301 days actual energy intake on a total of 301 days estimated traits of metabolic BW, milk production energy requirement, and empty BW change. Pair-wise bivariate animal models were used to estimate genetic and phenotypic parameters among the studied traits. Estimated heritabilities of total intake and production traits ranged from 0.27±0.07 for lactation actual energy intake to 0.45±0.08 for average body condition score over 301 days of the lactation period. RFI showed a moderate heritability estimate (0.20±0.03) and non-significant phenotypic and genetic correlations with lactation 3.5 % fat-corrected milk and average BW over lactation. Among the conformation traits, dairy strength, stature, rear attachment width, chest width and pin width had significant (P<0.05) moderate to strong genetic correlations with RFI. Combinations of these conformation traits could be used as RFI indicators in the dairy genetic improvement programmes to increase the accuracy of the genetic evaluation of feed intake and utilisation included in the index.     

Body development in sows, feed intake and maternal capacity. Part 1: performance, pre-breeding and lactation feed intake traits of primiparous sows

This study examined the genetic and phenotypic associations between finisher performance, pre-breeding body condition of the gilt, subsequent lactation feed intake and survival of the primiparous sow to farrow in the second parity. Complete data were available on ~2200 sows, along with additional cohort and historical performance data. Genetic variation was observed for average lactation feed intake (heritability: 0.18 ± 0.04), with a significant proportion of observed variation in average intake attributable to variation in lactation length. Weight and body condition (fatness) at finishing were very highly correlated genetically (0.89 ± 0.03 and 0.90 ± 0.02) and moderately correlated phenotypically (0.58 ± 0.01 and 0.58 ± 0.01) with weight and body condition before mating. Estimates of genetic (r(g)) and phenotypic (r(p)) correlations between feed intake recorded at finishing and average lactation feed intake (LADI) were moderate (r(g) = 0.26 ± 0.16 and 0.42 ± 0.22) and low (r(p) = 0.07 ± 0.02 and 0.08 ± 0.03), with r(g) dependent on the models and data subsets used for lactation intake. Non-unity genetic correlations imply that different genetic control mechanisms regulate feed intake during growth and lactation. Moderate genetic correlations between lactation feed intake with live weight (TWT) or growth rate (TADG) recorded at selection and live weight before mating (0.42 ± 0.11, 0.42 ± 0.11 and 0.37 ± 0.15) were considerably higher than the corresponding phenotypic correlations for LADI with TADG or 29WT (0.09 ± 0.02 and 0.08 ± 0.02). Correlations between fatness at selection (TFAT) or mating (29FT) and LADI were negative but not significantly different from 0. Overall, these data suggest that there is exploitable genetic variation for feed intake during lactation, and that selection is possible if lactation feed intakes are recorded. However, genetic correlations suggest that early growth seems to be related to lactation feed intake capacity. There was generally no strong evidence that selection for lean growth potential in dam lines will substantially diminish sow lactation intake capacity as a correlated response.     

Water requirements of beef production can be reduced by genetic selection

Growing concerns regarding sustainability in agriculture include the availability of drinking water, which is putting pressure on livestock production, especially the beef sector, for more efficient practices. Thus, genetic parameters were estimated for traits related to water intake and water use efficiency in Senepol cattle. Senepol females (n = 925) and males (n = 191) were evaluated in performance tests carried out from 2014 to 2019. Daily dry matter intake (DMI) and water intake (WI) were recorded by electronic feed and water bunks (Intergado Ltd.). Other traits assessed included average daily gain (ADG); mid-test metabolic BW (BW^0.75); residual water intake based on ADG (RWI_ADG), estimated as the residual of the linear regression equation of WI on ADG and BW^0.75; residual water intake based on DMI (RWI_DMI), estimated as the residual of the linear regression equation of WI on DMI and BW^0.75 (RWI_DMI); water conversion ratio (= WI/ADG); gross water efficiency (GWE = ADG/WI); residual feed intake estimated as the residual of the linear regression equation of DMI on ADG and BW^0.75 (RFI); feed conversion ratio (= DMI/ADG) and gross feed efficiency. Genetic (co)variances were estimated with bivariate analyses. The heritabilities for WI, RWI_ADG and RWI_DMI were 0.38, 0.36 and 0.33, respectively. Water conversion ratio, RWI_ADG and RWI_DMI showed positive genetic and phenotypic correlations with WI, whereas GWE was negatively correlated with WI, suggesting that traits related to water use efficiency may be useful to identify cattle with reduced WI. Water intake showed positive genetic (r = 0.79) and phenotypic (r = 0.60) correlations with DMI, suggesting the use of WI to estimate DMI in future studies. Both RWI_ADG and RWI_DMI were genetically correlated with RFI (0.67 and 0.57, respectively) and ADG (0.49 and 0.44, respectively), showing that RWI is positively associated with feed efficiency, but has an antagonistic relationship with growth. This antagonism, however, may be managed using selection indexes. Genetic improvement of water use efficiency in Senepol cattle is possible through selection and may reduce the water requirements of beef production systems.     

Indirect genetic effects on the relationships between production and feeding behaviour traits in growing Duroc pigs

Performance and feeding behaviour traits in growing pigs could be affected by social interaction effects when animals are raised in group. So, properly knowing the genetic correlations between direct and social interaction effects among performance and feeding behaviour traits could improve the accuracy of the genetic evaluations. Our aim was to explore the role of feeding behaviour traits (FBT) and indirect genetic effects (IGEs) in the genetic evaluations of growing pigs. Thus, genetic parameters were estimated for production traits (PT): average daily gain, average daily feed consumption, feed conversion ratio and backfat thickness; as well as for FBT: average daily feeding rate, average daily feeding frequency, average daily occupation time and average daily time between consecutive visits. Traits were recorded in 1144 Duroc pigs during the fattening period. Two bivariate models were fitted: classic animal model and an animal model fitting IGE. Estimations were done following Bayesian procedures. Heritability estimates obtained with classic animal model for all studied traits were medium-high. The additional heritable variation captured by IGE supposed that the ratios of total genetic variance to phenotypic variance (T²) were higher than the heritability estimates obtained with the classic model, except for occupation time trait, when a lower value (0.20 ± 0.19) was estimated. This is due to a high and negative correlation between IGE and direct genetic effects (DGEs) of this particular trait (−0.78 ± 0.27). Results from classic animal model do not evidence a clear role of FBT to improve the accuracy of breeding value predictions for PT; only average daily feeding rate seems to show a positive correlation (around 0.50 to 0.60) with average daily gain, average daily feed consumption and backfat thickness. However, when IGE model was fitted, the number of estimates of genetic correlations between FBT and PT showing a relevant magnitude increased, generally for the correlations between IGE of FBT and DGE of PT; or particularly for the correlations between IGE of average daily feeding frequency, and the IGE of all the PT, except average daily gain. Thus, in evaluations using the animal model with IGE fitted, the inclusion of FBT could aid the improvement of the accuracy of breeding value predictions for PT. This is a consequence of the improved genetic relationships between traits that can be fitted when considering such models.     

Impact of a high-fibre diet on genetic parameters of production traits in growing pigs

The use of diets with increased fibre content from alternative feedstuffs less digestible for pigs is a solution considered to limit the impact of increased feed costs on pig production. This study aimed at determining the impact of an alternative diet on genetic parameters for growth, feed efficiency, carcass composition and meat quality traits. A total of 783 Large White pigs were fed a high-fibre (HF) diet and 880 of their sibs were fed a conventional (CO) cereal-based diet. Individual daily feed intake, average daily gain, feed conversion ratio and residual feed intake were recorded as well as lean meat percentage (LMP), carcass yield (CY) and meat quality traits. Pigs fed the CO diet had better performances for growth and feed efficiency than pigs fed the HF diet. They also had lower LMP and higher CY. In addition, pigs fed the CO diet had lower loin percentage and ham percentage and higher backfat percentage. No differences were observed in meat quality traits between diets, except for a* and b* values. For all traits, the genetic variances and heritability were not different between diets. Genetic correlations for traits between diets ranged between 0.80 ± 0.13 and 0.99 ± not estimable, and none were significantly different from 0.99, except for LMP. Thus, traits in both diets were considered as mainly affected by similar sets of genes in the two diets. A genetic correlation lower than 0.80 would justify redesigning the breeding scheme; however, some genetic correlations did not differ significantly from 0.80 either. Therefore, larger populations are needed for a more definitive answer regarding the design of the breeding scheme. To further evaluate selection strategies, a production index was computed within diets for the 29 sires with estimated breeding value reliability higher than 0.35. The rank correlation between indices estimated in the CO and in the HF diet was 0.72. Altogether, we concluded that limited interaction between feed and genetics could be evidenced, and based on these results there is no need to change pig selection schemes to adapt to the future increased use of alternative feedstuffs in production farms.     

Relation between feeding behaviour and energy metabolism in pigs fed diets enriched in dietary fibre and wheat aleurone

Feed intake and its daily pattern are regulated both at a short and a long term by several control pathways, including energy balance regulation. This trial aimed to determine the effect of dietary fibre (DB) (mix of wheat, soy and sugar beet pulp fibres) and aleurone supplementation and their interaction on energy and nitrogen balances in growing pigs with ad libitum access to feed. Forty pigs (BW: 35 kg) were fed diets differing by fibre concentration (NDF concentration: 10% or 14% DM) and aleurone supplementation (0, 2 or 4 g/kg) during 3 weeks. Pigs were housed individually in a respiration chamber during the last week to record feeding behaviour and measure energy and nitrogen balances (n = 36). Glucose oxidation was studied on the 6th day with an injection of [U-¹³C] glucose and measurement of ¹³CO₂ production. There was no significant interaction between DB inclusion and aleurone supplementation on any variables characterizing feeding behaviour. Pigs had less but longer meals with high level of DB, with an increased interval between two meals without effect on daily feed intake. The meal frequency significantly decreased when aleurone supplementation increased. Total tract apparent digestibility coefficient of DM, organic matter, ash, nitrogen and gross energy decreased when pigs received high DB level. Dietary fibre level increased significantly faecal excreted nitrogen. Aleurone supplementation decreased nitrogen retention. Free access to the feed induced a great individual variability not only in feed intake level (from 784 to 2290 g/day) but also in feeding behaviour (from 5.5 to 21.5 meals per day). This variability can be linked with the importance of underlying feed intake regulation pathways and difference in energy balance and metabolism efficiency. Several profiles of metabolism efficiency can be discriminate, thanks to a clustering based on feeding behaviour and pre-prandial concentrations of metabolites and hormones. In conclusion, DB inclusion decreased meal frequency, increased average meal size, decreased total tract apparent faecal digestibility coefficient of nitrogen and gross energy. Supplementation of aleurone decreased average daily feed intake with a reduction of the meal number per day, without modification of average meal size. Aleurone supplementation decreased nitrogen retention and nutrient deposition. Independently of experimental diets, the high individual variability permitted discriminating different profiles with different metabolic strategies. Efficient pigs with a high energy retention as protein and lipid seem to be able to adapt their metabolism according to energy sources.     

A kinetic study of the natural induction of liver steatosis in Greylag Landaise geese: the role of hyperphagia

We have previously demonstrated that a sharp rise in feed intake (hyperphagia) and spontaneous liver steatosis could be experimentally induced in domestic Greylag geese by combining a short photoperiod and a sequence of feed restriction followed by ad libitum corn feeding during the fall and the winter. In this previous work, however, individual feed intake could not be recorded. The present study aimed at evaluating the relationship between level and pattern of hyperphagia and liver weight with an individual control of feed intake in individually housed (IH) geese, while comparing the performances with group housed (GH) geese. A total of 300 male geese of 19 weeks of age, were provided with corn ad libitum after an initial feed restriction period. From 21 to 23 weeks of age, the daylight duration was progressively reduced from 10 to 7 h and kept as such until the end of the experiment (week 36). In all, 30 GH and 30 IH geese were slaughtered at 19, 27, 30, 32 and 36 weeks of age. Feed intake was measured per group in GH geese and individually in IH geese. During the 1^st week of corn feeding, the average feed intake rose up to 600 g/goose per day in GH geese but not in IH geese where the feed intake rose gradually from 300 to 400 g/day. The liver weight increased from 93 g (week 19) to 497 g (week 32; P<0.05) in GH birds. In IH birds, liver weights were, on average, much lower (ranging from 220 to 268 g) than in GH birds (P<0.05). In GH and IH bird, the variability in the individual response to corn feeding was very high (liver weight c_v ranging from 63% to 83% depending on slaughter age). A close correlation between corn consumption and liver weight was evidenced in IH birds at each slaughter age (R² ranging from 0.62 to 0.79), except at 36 weeks of age where this correlation was weak (R²=0.14). The variability in the extent of liver steatosis is very high and our results in IH birds clearly point out the major role of hyperphagia, mainly at the beginning of the ad libitum corn feeding period, on the development of spontaneous liver steatosis.     

Effects of finishing diet sorting and digestibility on performance and feed efficiency in beef steers

The aim of this study was to test the hypotheses that differences in residual feed intake (RFI) of beef steers are related to diet sorting, diet nutrient composition, energy intake and apparent digestibility. To phenotype steers for RFI, 69 weaned Angus × Hereford steers were fed individually for 56 days. A finishing diet was fed twice daily on an ad libitum basis to maintain approximately 0.5 to 1.0 kg refusals. Diet offered and refused was measured daily, and DM intakes (DMI) were calculated by difference. Body weights were recorded at 14-day intervals following an 18-h solid feed withdrawal. The residual feed intake was determined as the residual of the regression of DMI versus mid-test metabolic BW (BW ^0.75) and average daily gain (ADG). Particle size distributions of diet and refusals were determined using the Penn State Particle Separator to quantify diet sorting. Sampling of diet, refusals and feces were repeated in four sampling periods which occurred during weeks 2, 4, 6 and 8 of the study. Particle size distributions of refusals and diet were analyzed in weeks 2, 4 and 6, and sampling for chemical analysis of refusals and feces occurred in all four periods. Indigestible neutral detergent fiber (288 h in situ) was used as an internal marker of apparent digestibility. We conclude that preference for the intakes of particles > 19 mm and 4 to 8 mm were negatively correlated to RFI and ADG, respectively. Although steers did sort to consume a different diet composition than offered, diet sorting did not impact intake energy, digestible energy or DM digestibility.     

Phenotypic and genetic relationships between growth and feed intake curves and feed efficiency and amino acid requirements in the growing pig

Improvement of feed efficiency in pigs has been achieved essentially by increasing lean growth rate, which resulted in lower feed intake (FI). The objective was to evaluate the impact of strategies for improving feed efficiency on the dynamics of FI and growth in growing pigs to revisit nutrient recommendations and strategies for feed efficiency improvement. In 2010, three BWs, at 35±2, 63±9 and 107±7 kg, and daily FI during this period were recorded in three French test stations on 379 Large White and 327 French Landrace from maternal pig populations and 215 Large White from a sire population. Individual growth and FI model parameters were obtained with the InraPorc^R software and individual nutrient requirements were computed. The model parameters were explored according to feed efficiency as measured by residual feed intake (RFI) or feed conversion ratio (FCR). Animals were separated in groups of better feed efficiency (RFI⁻ or FCR⁻), medium feed efficiency and poor feed efficiency. Second, genetic relationships between feed efficiency and model parameters were estimated. Despite similar average daily gains (ADG) during the test for all RFI groups, RFI⁻ pigs had a lower initial growth rate and a higher final growth rate compared with other pigs. The same initial growth rate was found for all FCR groups, but FCR⁻ pigs had significantly higher final growth rates than other pigs, resulting in significantly different ADG. Dynamic of FI also differed between RFI or FCR groups. The calculated digestible lysine requirements, expressed in g/MJ net energy (NE), showed the same trends for RFI or FCR groups: the average requirements for the 25% most efficient animals were 13% higher than that of the 25% least efficient animals during the whole test, reaching 0.90 to 0.95 g/MJ NE at the beginning of the test, which is slightly greater than usual feed recommendations for growing pigs. Model parameters were moderately heritable (0.30±0.13 to 0.56±0.13), except for the precocity of growth (0.06±0.08). The parameter representing the quantity of feed at 50 kg BW showed a relatively high genetic correlation with RFI (0.49±0.14), and average protein deposition between 35 and 110 kg had the highest correlation with FCR (−0.76±0.08). Thus, growth and FI dynamics may be envisaged as breeding tools to improve feed efficiency. Furthermore, improvement of feed efficiency should be envisaged jointly with new feeding strategies.     

Genetic parameters of a random regression model for daily feed intake of performance tested French Landrace and Large White growing pigs

Daily feed intake data of 1 279 French Landrace (FL, 1 039 boars and 240 castrates) and 2 417 Large White (LW, 2 032 boars and 385 castrates) growing pigs were recorded with electronic feed dispensers in three French central testing stations from 1992–1994. Male (35 to 95 kg live body weight) or castrated (100 kg live body weight) group housed, ad libitum fed pigs were performance tested. A quadratic polynomial in days on test with fixed regressions for sex and batch, random regressions for additive genetic, pen, litter and individual permanent environmental effects was used, with two different models for the residual variance: constant in model 1 and modelled with a quadratic polynomial depending on the day on test d_m as follows in model 2: . Variance components were estimated from weekly means of daily feed intake by means of a Bayesian analysis using Gibbs sampling. Posterior means of (co)variances were calculated using 800 000 samples from four chains (200 000 each). Heritability estimates of regression coefficients were 0.30 (FL model 1), 0.21 (FL model 2), 0.14 (LW1) and 0.14 (LW2) for the intercept, 0.04 (FL1), 0.04 (FL2), 0.11 (LW1) and 0.06 (LW2) for the linear, 0.03 (FL1), 0.04 (FL2) 0.11 (LW1) and 0.06 (LW2) for the quadratic term. Heritability estimates for weekly means of daily feed intake were the lowest in week 4 (FL1: 0.11, FL2: 0.11) and week 1 (LW1: 0.09, LW2: 0.10), and the highest in week 11 (FL1: 0.25, FL2: 0.24) and week 8 (LW1: 0.19, LW2: 0.18), respectively. Genetic eigenfunctions revealed that altering the shape of the feed intake curve by selection is difficult.     

Potential use of radiography for measuring feed intake of southern rock lobster (Jasus edwardsii)

The potential of using radiography for measuring feed intake in southern rock lobster Jasus edwardsii (Hutton) was evaluated. Lobsters (14-40 g) readily consumed feeds containing radio-opaque marker (400—450 μm). Marker particles were clearly identified in the stomach 90 min after feeding enabling feed intake to be estimated. Initially low estimates (15±17%; mean±S.D.) of feed intake (expressed as percentage of gravimetric estimates) were recorded due to loss of markers prior to ingestion. Radiographic estimates improved (100±23%; mean±S.D.) when changes to pellet diameter (1.5 mm), moisture content (11%) and binding agent (alginate) were made. Thus, estimates were dependent on pellet diameter and resistance to fragmentation prior to ingestion. To test for the presence of feeding hierarchies in groups of lobsters an experiment was conducted to examine the effect of ration level (high ration: 2.0% BW day⁻¹ and low ration: 0.2% BW day⁻¹) on intra-individual (measured as coefficient of variation for feed intake: CV_C) and inter-individual variation (measured as mean share of the group meal: MSM%). There was a significant (P<0.05) negative correlation between CV_C and MSM% for the low ration treatments which indicated that small lobsters (CV_C=114±19% and MSM%=22±10%: mean±S.D.) were less successful than large lobsters (CV_C 44±11% and MSM%=41±13%: mean±S.D.) at obtaining feed. This may be indicative of the formation of feeding hierarchies.     

Breeding salmonids for feed efficiency in current fishmeal and future plant-based diet environments

The aquaculture industry is increasingly replacing fishmeal in feeds for carnivorous fish with soybean meal (SBM). This diet change presents a potential for genotype-environment (G × E) interactions. We tested whether current salmonid breeding programmes that evaluate and select within fishmeal diets also improve growth and efficiency on potential future SBM diets. A total of 1680 European whitefish from 70 families were reared with either fishmeal- or SBM-based diets in a split-family design. Individual daily gain (DG), daily feed intake (DFI) and feed efficiency (FE) were recorded. Traits displayed only weak G × E interactions as variances and heritabilities did not differ substantially between the diets, and cross-diet genetic correlations were near unity. In both diets, DFI exhibited moderate heritability and had very high genetic correlation with DG whereas FE had low heritability. Predicted genetic responses demonstrated that selection to increase DG and FE on the fishmeal diet lead to favourable responses on the SBM diet. Selection for FE based on an index including DG and DFI achieved at least double FE gain versus selection on DG alone. Therefore, current breeding programmes are improving the biological ability of salmonids to use novel plant-based diets, and aiding the aquaculture industry to reduce fishmeal use.     

Multiple trait model combining random regressions for daily feed intake with single measured performance traits of growing pigs

A random regression model for daily feed intake and a conventional multiple trait animal model for the four traits average daily gain on test (ADG), feed conversion ratio (FCR), carcass lean content and meat quality index were combined to analyse data from 1 449 castrated male Large White pigs performance tested in two French central testing stations in 1997. Group housed pigs fed ad libitum with electronic feed dispensers were tested from 35 to 100 kg live body weight. A quadratic polynomial in days on test was used as a regression function for weekly means of daily feed intake and to escribe its residual variance. The same fixed (batch) and random (additive genetic, pen and individual permanent environmental) effects were used for regression coefficients of feed intake and single measured traits. Variance components were estimated by means of a Bayesian analysis using Gibbs sampling. Four Gibbs chains were run for 550 000 rounds each, from which 50 000 rounds were discarded from the burn-in period. Estimates of posterior means of covariance matrices were calculated from the remaining two million samples. Low heritabilities of linear and quadratic regression coefficients and their unfavourable genetic correlations with other performance traits reveal that altering the shape of the feed intake curve by direct or indirect selection is difficult.     

Quantifying the genetic parameters of feed efficiency in juvenile Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Background

Improving feed efficiency in fish is crucial at the economic, social and environmental levels with respect to developing a more sustainable aquaculture. The important contribution of genetic improvement to achieve this goal has been hampered by the lack of accurate basic information on the genetic parameters of feed efficiency in fish. We used video assessment of feed intake on individual fish reared in groups to estimate the genetic parameters of six growth traits, feed intake, feed conversion ratio (FCR) and residual feed intake in 40 pedigreed families of the GIFT strain of Nile tilapia, Oreochromis niloticus. Feed intake and growth were measured on juvenile fish (22.4 g mean body weight) during 13 consecutive meals, representing 7 days of measurements. We used these data to estimate the FCR response to different selection criteria to assess the potential of genetics as a means of increasing FCR in tilapia.

Results

Our results demonstrate genetic control for FCR in tilapia, with a heritability estimate of 0.32?±?0.11. Response to selection estimates showed FCR could be efficiently improved by selective breeding. Due to low genetic correlations, selection for growth traits would not improve FCR. However, weight loss at fasting has a high genetic correlation with FCR (0.80?±?0.25) and a moderate heritability (0.23), and could be an easy to measure and efficient criterion to improve FCR by selective breeding in tilapia.

Conclusion

At this age, FCR is genetically determined in Nile tilapia. A selective breeding program could be possible and could help enabling the development of a more sustainable aquaculture production.

     

Interrelationship between metabolism of tritiated water, 22sodium and dry matter intake by beef cattle consuming wheat straw and poultry litter in free choice

• 1.1. Metabolism of tritiated water and ²²sodium was studied in six beef cows under Mediterranean summer conditions in order to find whether the turnover of these tracers can be used to evaluate pasture intake.
• 2.2. The diet of the cows included ad libitum access to two components which were given separately in different troughs: one was poultry litter and the other was wheat straw, to simulate the dry pasture.
• 3.3. Voluntary daily dry matter intake (111 g/kg^0.75) was unexpectedly high considering the low digestibility of the feed.
• 4.4. The assumptions of constant ratios of water intake to water turnover and of dry matter intake to water intake were confirmed. Consequently, dry matter intake was determined accurately from water turnover measurements.
• 5.5. Sodium intake was practically equal to sodium turnover and most of the sodium secreted in feces was of endogenous origin.
• 6.6. Pasture intake can be predicted from sodium turnover once the concentration in feed and water consumed is known.

     

Genetic variability in residual feed intake in rainbow trout clones and testing of indirect selection criteria (Open Access publication)

Little is known about the genetic basis of residual feed intake (RFI) variation in fish, since this trait is highly sensitive to environmental influences, and feed intake of individuals is difficult to measure accurately. The purpose of this work was (i) to assess the genetic variability of RFI estimated by an X-ray technique and (ii) to develop predictive criteria for RFI. Two predictive criteria were tested: loss of body weight during feed deprivation and compensatory growth during re-feeding. Ten heterozygous rainbow trout clones were used. Individual intake and body weight were measured three times at threeweek intervals. Then, individual body weight was recorded after two cycles of a three-week feed deprivation followed by a three-week re-feeding. The ratio of the genetic variance to the phenotypic variance was found high to moderate for growth, feed intake, and RFI (VG/VP = 0.63 ± 0.11, 0.29 ± 0.11, 0.29 ± 0.09, respectively). The index that integrates performances achieved during deprivation and re-feeding periods explained 59% of RFI variations. These results provide a basis for further studies on the origin of RFI differences and show that indirect criteria are good candidates for future selective breeding programs.