Nucleus Breeding Research Articles

Breeding systems for genetic improvement of dairy goats in smallholder production systems in Kenya

A deterministic simulation model was used to test the hypothesis that utilization of untested juvenile bucks could be an alternative to old buck strategy in dissemination of superior genetic materials in dairy goats breeding program. We compared the genetic and economic gains realised when the untested juvenile and old bucks were used to disseminate genetic materials in a two-tier closed and open nucleus breeding systems. In the untested juvenile buck strategy, 95 and 70% of nucleus and commercial does, respectively, were mated to the untested juvenile bucks. In the old buck strategy, all the females in the nucleus and 70% of commercial does were mated by old bucks from the nucleus. In the open nucleus system, 20% of the does born in the commercial sector were recruited into the nucleus to produce nucleus does of does. Utilization of untested juvenile bucks realised 5.92 and 7.30% more annual returns and profitability per doe, respectively compared to old buck strategy. The old buck strategy, however, outperformed untested juvenile buck strategy by 23.37 and 14.85% in total annual genetic gain in closed and open nucleus breeding systems, respectively. Comparison between closed and open nucleus breeding systems demonstrated that open nucleus systems are superior to closed nucleus systems both in genetic and economic response. These findings therefore demonstrate that untested juvenile bucks could be an alternative to old buck strategy when economic viability of the breeding program is the main focus. There is, however, need to strike a balance between economic and genetic gains in the breeding program.

Defining a breeding objective for Nile tilapia that takes into account the diversity of smallholder production systems.

In general, livestock and fish farming systems in developing countries tend to be highly diverse in terms of agro-ecological conditions and market orientation. There are no studies that have investigated if and how this diversity translates to varying preferences for breeding objective traits. This is particularly important for breeding programmes that are organized on a national level (e.g. government-supported nucleus breeding programmes). The aim of this study was to investigate whether Nile tilapia farmers with diverse production systems and economic constraints have different preferences for breeding objective traits. The second objective was to derive a consensus breeding goal, using weighted goal programming that could be used for a national breeding programme for Nile tilapia. A survey was conducted among 100 smallholder Nile tilapia farmers in Kenya to obtain preference values for traits of economic importance, by using multiple pairwise comparisons. Individual and group preference values were estimated using analytical hierarchy process. Low-income farmers preferred harvest weight, while medium- and high-income farmers preferred growth rate and survival. Grouping farmers according to market objective (fingerling production or fattening) showed that fingerling producers preferred growth rate and survival, while fattening farmers preferred harvest weight, height and thickness. Weighted goal programming was used to obtain consensus preference values, and these were used to derive desired gains for a breeding goal of a national breeding programme that takes into account the diversity of smallholder production systems.

Phenotypic characterization, management and performance of Belahi cattle

Belahi cattle are medium sized dual utility migratory breed maintained and primarily conserved by Gujjar community in India. The average first lactation milk yield recorded was about 1,071 kg with average daily milk yield and peak yield of 3.45 and 5.5 kg, respectively which is higher than the national average of indigenous cattle. Milk constitutes traits were estimated in pooled milk as 14.38% total solids, 5.25% fat, 3.45% protein and 5.20% lactose, indicating good quality of the milk. However, planned efforts for their genetic improvement are needed to improve gains. Our findings suggests that Belahi cattle has a good milk potential on low input, dual purpose utility, has high socioeconomic relevance and can immensely contribute to the livelihood security of Gujjar pastoralists of the sub Himalayan region. We recommend that these herds should be associated with Progeny Testing program/Open Nucleus Breeding System to explore their full milking potential. Further we recommend, long pending, strong policy support for such migratory groups, as they immensely contribute in economy of the state and in conservation of indigenous cattle genetic resources.

Genotype by environment interaction for harvest weight, growth rate and shape between monosex and mixed sex Nile tilapia (Oreochromis niloticus)

In Kenya, Nile tilapia (Oreochromis niloticus) is mostly grown in ponds. To avoid excessive reproduction and stunted growth, fingerlings are treated with methyl-testosterone to make all-male populations (monosex). For a national breeding programme that aims to provide genetically improved broodstock to hatcheries that supply monosex fry to smallholder pond farmers, it is important to assess the genetic correlation (rg) for traits between the mixed sex breeding candidates from the breeding nucleus and monosex production fish. The purpose of the study was to estimate genetic parameters for harvest weight (HW), daily growth coefficient (DGC) and body shape and investigate genotype by environment interaction (G×E) for these traits between mixed sex and monosex populations. Forty-eight sires and 76 dams from the F2 generation of a local O. niloticus strain, kept at Sagana Aquaculture Research Station, Kenya were used to produce 76 full-sib families. Mixed sex fry (3days old) from each full sib family were divided into two groups of 50 individuals each. One group (monosex) was fed a diet treated with methyl-testosterone to induce sex reversal while the other group (mixed sex) was reared on a control diet. After hapa rearing, tagging and weighing, fish were randomly divided and stocked in six earthen ponds, three for mixed sex and three for monosex fish. After 5months, fish were harvested, photographed and weighed. Genetic parameter estimates for HW, DGC, and shape were obtained on 2105 fish. Heritability estimates for HW, DGC and shape were 0.21±0.03, 0.26±0.04 and 0.12±0.03 for mixed sex respectively. Genetic correlations for HW between monosex and mixed sex was 0.74±0.14, suggesting low G×E. The corresponding rg for DGC and shape were lower; 0.59±0.10, and −0.19±0.11, respectively, denoting the presence of G×E. It is concluded that G×E between the mixed sex nucleus and monosex production fish is important, and that a breeding programme for Nile tilapia needs to include production performance from monosex siblings. Statement of relevanceFirst study that reports estimates for Genotype by treatment interaction between hormone treated monosex Nile tilapia and mixed sex Nile tilapia, and discusses the consequences for nucleus breeding programmes.

Performance of Seven Tree Breeding Strategies Under Conditions of Inbreeding Depression.

In the domestication and breeding of tree species that suffer from inbreeding depression (ID), the long-term performance of different breeding strategies is poorly known. Therefore, seven tree breeding strategies including single population, subline, selfing, and nucleus breeding were simulated using a multi-locus model with additive, partial, and complete dominance allele effects, and with intermediate, U-shaped, and major allele distributions. The strategies were compared for genetic gain, inbreeding accumulation, capacity to show ID, the frequencies and fixations of unfavorable alleles, and genetic variances in breeding and production populations. Measured by genetic gain of production population, the nucleus breeding and the single breeding population with mass selection strategies were equal or superior to subline and single breeding population with within-family selection strategies in all simulated scenarios, in spite of their higher inbreeding coefficients. Inbreeding and cross-breeding effectively decreased ID and could in some scenarios produce genetic gains during the first few generations. However, in all scenarios, considerable fixation of unfavorable alleles rendered the purging performance of selfing and cross-breeding strategies ineffective, and resulted in substantial inferiority in comparison to the other strategies in the long-term.

Can genetic diversity be maintained across multiple mass selection lines of Sydney rock oyster, Saccostrea glomerata despite loss within each?

This study assesses the genetic diversity of four different hatchery bred lines of Sydney rock oyster, Saccosstrea glomerata (SRO) after three, five and seven generations of mass selection using microsatellite DNA markers and mitochondrial cytochrome C oxidase subunit 1 sequences (COX1). This was achieved using seven newly developed microsatellite markers, along with three published loci. Considering the same number of samples in each line, the number of different alleles in each of the four hatchery lines ranged from 49 to 70 alleles from 10 loci, which was approximate 50% less than the 120 alleles found in the samples from the wild population. However, if we pool all our four hatchery lines together, then their total number of alleles was not significantly different from the wild population. Similar to the patterns found for the DNA microsatellite alleles, mtDNA haplotype numbers were considerably lower in each of the hatchery lines than in the samples from the wild population. Again, pooling the hatchery lines gave a total haplotype number not statistically significantly different from that in the samples from the wild. Considering together the DNA microsatellite alleles and the mtDNA haplotypes, we conclude that there was a substantial loss of genetic diversity within all lines separately over generations of mass selection, and that such mass selection was not sustainable in the long term. However, importantly, these data indicate that for oysters, if multiple independent mass selection lines are kept, then their combined genetic diversity may approach that of the ancestral line or wild population even after many generations of mass selection. These results for oysters, finding preservation of diversity among lines yet loss within them, are similar to recent findings for multiple banana shrimp lines; considering both species together it suggests that one relatively simple option suitable for some farms and industry to maintain genetic diversity during mass selection over many generations of selection is to subdivide their breeding nucleus and keep multiple different and independent lines over generations. It remains to be tested if this approach is general across many aquaculture species and circumstances. Statement of relevanceThis paper attempts to falsify the published hypothesis set out by Knibb et al., 2014 that “the use of multiple lines under some circumstances may be a hedge against loss of diversity” using a second independent example, namely Sydney rock oysters.The data of this paper do not refute the generality of the above hypothesis of Knibb et al., 2014 that splitting mass selection lines into multiple sublines preserves genetic variation.

Genetic parameters and response to selection of harvest body weight of the Chinese shrimp Fenneropenaeus chinensis after five generations of multi-trait selection

Genetic parameters and predicted and realized selection responses were estimated for harvest body weight of Chinese shrimp (Fenneropenaeus chinensis) after five generations of multi-trait selection. The body weights of 15,201 tagged shrimp representing 460 full-sib families in 6 generations were recorded at harvest. Heritability estimates for body weight showed large variation in magnitude (0.00±0.00-0.36±0.07) when analyzing data from each generation separately. When data from all generations (G0-G5) were included in analysis, the heritability estimate for body weight was 0.18. While, G0 was more affected by environmental conditions than the other generation in this study, when data from G0 was excluded, the heritability was 0.21. The common environment effect estimate was 0.08 when all data included and 0.06 when G1-G5 included. The females were significantly larger than the males at harvest (P<0.05). The genetic correlation of the harvest body weight between sexes was similar within and across generations, indicating that body weight in male and female shrimp is likely controlled by the same genes. Breeding candidates in the base population (G0) were selected according to their individual breeding values for growth. In later generations (G1-G5), candidates were selected according to a selection index including breeding values for growth, survival time after WSSV infection and pond survival. The response to selection for harvest body weight was estimated by two methods (the realized and predicted responses). The realized response was estimated from the differences in the least square means of body weight between the selection and control populations. The predicted response was obtained from the differences in the mean breeding values between generations. The accumulated realized response was 18.60% after performing five selections. The accumulated predicted responses estimated using two sets of genetic parameters obtained from within and across generation datasets were 6.43% and 6.50%, respectively. The results are discussed in a practical context of developing selective breeding programs for Chinese shrimp, and it is indicated that the selective breeding program has generated effective genetic improvement after five generations of selection. The future direction of the genetic improvement program is discussed. Statement of relevanceChinese shrimp, Fenneropenaeus chinensis, is one of the most valuable mariculture species in China. The Yellow Sea Fisheries Research Institute (Qingdao, China) initiated a multi-trait selective breeding program for Chinese shrimp in 2004, based on a combined family and within (inter) family selection scheme to improve growth, survival time after WSSV infection and pond survival. A new selected breed named “Huanghai No. 2” (registration no. GS01-002-2008) was approved in 2008. This program provided significant economic and social benefits. However, only limited results regarding this program have been reported, which involved genetic parameters of harvest body weight and genetic correlations among different traits using only one year data, a smaller subset of the current study.Growth is one of the most desirable economic traits in aquaculture. Good growth is important for efficient production and contributes to more profitable and sustainable development. Currently, the selective breeding program for F. chinensis is ongoing and the breeding nucleus was divided into different lines after performing five selections. In this paper, we will focus on the results related to genetic evaluation for the harvest body weights from G0 to G5. We will present more reliable estimates of phenotypic and genetic parameters, calculate the response to selection after performing five selections and discuss the longer term implications of the findings from a genetic improvement viewpoint.

Efficient Boar Semen Production and Genetic Contribution: The Impact of Low-Dose Artificial Insemination on Fertility.

Diluting semen from high fertile breeding boars, and by that inseminating many sows, is the core business for artificial insemination (AI) companies worldwide. Knowledge about fertility results is the reason by which an AI company can lower the concentration of a dose. Efficient use of AI boars with high genetic merit by decreasing the number of sperm cells per insemination dose is important to maximize dissemination of the genetic progress made in the breeding nucleus. However, a potential decrease in fertility performance in the field should be weighed against the added value of improved genetics and, in general, is not tolerated in commercial production. This overview provides some important aspects that influence the impact of low-dose AI on fertility: (i) the importance of monitoring field fertility, (ii) the need for accurate and precise semen assessment, (iii) the parameters that are taken into account, (iv) the application of information from genetic and genomic selection and (v) the optimization when using different AI techniques. Efficient semen production, processing and insemination in combination with increasing use of genetic and genomic applications result in maximum impact of genetic trend.

Assessment of institutional capacities of the Gambia Indigenous Livestock Multipliers’ Associations

SummaryThis exploratory study aims to understand and improve the performance of Gambia Indigenous Livestock Multipliers’ Associations (GILMA – Fulladu and Saloum) as a way of enabling them to better respond to the challenges faced in fulfilling their institutional responsibilities. Using participatory institutional diagnosis, the GILMA members and experts were able to examine their associations and to stimulate collective reflection as a means of making the associations more efficient and effective. The findings of this diagnosis showed that functioning of both GILMAs was closely linked to the operations of their technical partners. This resulted to GILMAs which clearly lack defined vision and mission. Main issues to address include capacity development of GILMA's executive committee in terms of institutional management, group facilitation, participatory planning, effective strategies for partnership and ownership. Overall, this study developed pathways for revitalizing GILMAs into vibrant and self-sustaining indigenous ruminant livestock multipliers’ associations that can effectively carry out specific roles and responsibilities within the three-tier Open Nucleus Breeding Scheme of the International Trypanotolerance Centre.

Genotype by Environment Interaction for Growth in Atlantic Cod (Gadus morhua L.) in Four Farms of Norway

We studied genotype by environment interaction (G × E) for body weight (BW) of Atlantic cod (Gadus morhua L.) from the National cod breeding program in Norway. Records of 13,811 fish in a nucleus farm (NUC) and two test farms (PENorth, PESouth) in year-class (YC) 2007, and for 9149 fish in NUC and one test farm in YC 2010 were available. Heterogeneity of variances and heritabilities ( ) were estimated using a univariate animal model with environmental effects common to full-sibs (full-model). Genetic correlations ( ) between farms were estimated using a multivariate full-model and a reduced-model (without ) for each YC. Heterogeneity of was observed in both YC 2007 (0.10 to 0.16) and YC 2010 (0.08 to 0.26). The estimates of between NUC and test farms were relatively high for both models (0.81 ± 0.19 to 0.96 ± 0.17) and (0.81 ± 0.08 to 0.86 ± 0.04), suggesting low re-ranking of genotypes. Strong re-ranking of genotypes between PESouth and PENorth may be less important because most cod producers are situated close to the breeding nucleus. In conclusion, G × E between NUC and test farms were low and at present there is no need for separate breeding programs for BW in cod.

Implementation of a cashmere goat breeding program amongst nomads in Southern Iran

A breeding program to improve income from Raeini cashmere herds run by nomads in Southern Iran was implemented. Eight nomads agreed on improving fleece weight, body weight and down yield while reducing cashmere fibre diameter of white coated goats. Economic weights were calculated to define a breeding objective. Each nomad established a breeding nucleus selecting visually his best 40 does and two bucks from about 250 goats. Nomads used different systems to ensure separate mating of nucleus and general herd animals. Nomads were also able to identify the progeny of each buck. Nucleus progenies were recorded for weaning weight and fleece weight. Fleece samples were collected for analyses of down yield and down fibre diameter. General herd male progeny was castrated. Formal selection indices were used to select nucleus male replacements. To construct the indices phenotypic and genetic parameters were taken from project data and published figures. Accuracy of indices ranged 0.47 to 0.66 depending on the traits included. The inferior buck based on progeny index average was replaced by the best young buck available. Other high ranked young bucks were used in the general herd. The breeding program is in its fourth cycle and favourable selection differentials were confirmed for selected bucks in all traits of interests, in particular for down weight and down diameter, 62g and −0.5μm, respectively. The expected benefit of the program is about 4.0 USD accumulating per goat and per year. Fleece testing is an issue since the region lacks a fleece testing service. If fleece sampling is discontinued the expected benefit reduces to about 2.8 USD per goat and per year. Circular use of bucks to control inbreeding and participation of additional nomad families are planned for the future. This experience shows that a participatory breeding program can be successfully implemented under nomadic conditions through intensive collaboration of nomad herders, regional extension officers and scientists.

Can the Global Adoption of Genetically Improved Farmed Fish Increase Beyond 10%, and How?

The annual production from global aquaculture has increased rapidly from 2.6 million tons or 3.9% of the total supply of fish, shellfish and mollusks in 1970, to 66.7 million tons or 42.2% in 2012, while capture fisheries have more or less leveled out at about 90 million tons per year since the turn of the century. Consequently, the future seafood supply is likely to depend on a further increase of aquaculture production. Unlike terrestrial animal farming, less than 10% of the aquaculture production comes from domesticated and selectively bred farm stocks. This situation has substantial consequences in terms of poorer resource efficiency, poorer product quality and poorer animal welfare. The history of biological and technical challenges when establishing selective breeding programs for aquaculture is discussed, and it is concluded that most aquaculture species may now be domesticated and improved by selection. However, the adoption of selective breeding in aquaculture is progressing slowly. This paper reports on a study carried out in 2012 to identify key issues to address in promoting the development of genetically improved aquaculture stocks. The study involved semi structured interviews of 34 respondents from different sectors of the aquaculture society in East and Southeast Asia, where 76% of the global aquaculture production is located. Based on the interviews and literature review, three key factors are identified: (i) long-term public commitment is often needed for financial support of the breeding nucleus operation (at least during the first five to ten generations of selection); (ii) training at all levels (from government officers and university staff to breeding nucleus and hatchery operators, as well as farmers); and (iii) development of appropriate business models for benefit sharing between the breeding, multiplier and grow-out operators (whether being public, cooperative or private operations). The public support should be invested in efforts of selective breeding on the most important and highest volume species, which may not be a priority for investment by private breeders due to, for instance, long generation intervals and delays in return to investment.

Survival analysis of genetic and non-genetic factors influencing ewe longevity and lamb survival of Ethiopian sheep breeds

Survival analysis applying proportional hazards models was used to investigate genetic and non-genetic factors affecting ewe longevity and lamb survival of sheep in Ethiopia. Data were obtained from an on-station closed nucleus breeding program of Menz sheep and an on-farm Awassi×Menz sheep crossbreeding project. A total of 695 ewes and 1890 lambs born from the nucleus population of Menz sheep were used for the analysis of ewe productive life and lamb survival to yearling age respectively. In addition, 5530 lamb records of purebred local and crossbreds with proportions of ~25–50% Awassi, collected from three locations were used for the analysis of lamb survival from birth to weaning age. The effects of year, ewe parity and litter weight at weaning were significant (p<0.05) for ewe productive life. On-station lamb survival to yearling was affected by year and breeding value of yearling weight of the lamb, indicating that faster growing animals had substantially higher survival rates. Animal model heritability estimates for lamb mortality ranged from 0.02 to 0.10. While there was a strong genetic trend for growth rate, as evidenced by estimated breeding values for different birth years, estimated breeding values for lamb survival were variable across years with decreasing trend. These results indicate no antagonism between growth rate and survival under conditions prevailing in the nucleus system. Routine genetic evaluation for survival is suggested. Under farmer conditions, the effects of year, season, sex and location effects were significant (p<0.05) on lamb survival to weaning age whereas breed composition (local versus crossbred) of dam as well as of the lamb were not significant. This seems to indicate that crossbreeding of local animals with Awassi sheep does not have an adverse effect on the survival of lambs under farmer conditions typical for the Ethiopian highland regions included in this study.

Genetic variation within and between subpopulations of the Australian Merino breed

Genetic variation within and between Australian Merino subpopulations was estimated from a large breeding nucleus in which up to 8500 progeny from over 300 sires were recorded at eight sites across Australia. Subpopulations were defined as genetic groups using the Westell–Quaas model in which base animals with unknown pedigree were allocated to groups based on their flock of origin if there were sufficient ‘expressions’ for the flock, or to one of four broad sheep-type groups otherwise (Ultra/Superfine, Fine/Fine-medium, Medium/Strong, or unknown). Linear models including genetic groups and additive genetic breeding values as random effects were used to estimate variance components for 12 traits: yearling greasy and clean fleece weight (ygfw and ycfw), yearling mean and coefficient of variation of fibre diameter (yfd and ydcv), yearling staple length and staple strength (ysl and yss), yearling fibre curvature (ycuv), yearling body wrinkle (ybdwr), post-weaning weight (pwt), muscle (pemd) and fat depth (pfat), and post-weaning worm egg count (pwec). For the majority of traits, the genetic group variance ranged from approximately equal to two times larger than the additive genetic (within group) variance. The exceptions were pfat and ydcv where the genetic group to additive variance ratios were 0.58 and 0.22, respectively, and pwec and yss where there was no variation between genetic groups. Genetic group correlations between traits were generally the same sign as corresponding additive genetic correlations, but were stronger in magnitude (either more positive or more negative). These large differences between genetic groups have long been exploited by Merino ram breeders, to the extent that the animals in the present study represent a significantly admixed population of the founding groups. The relativities observed between genetic group and additive genetic variance components in this study can be used to refine the models used to estimate breeding values for the Australian Merino industry.

Inbreeding Effects on Body Weight at Harvest Size and Grow‐out Survival Rate in a Genetic Selected Population of Pacific White Shrimp Penaeus (Litopenaeus) vannamei

AbstractThe objective of this study was to investigate the effect of inbreeding on body weight (BW) at harvest size (130 d of age) and grow‐out survival rate (SR) (65–130 d of age) in a nucleus breeding population of Penaeus (Litopenaeus) vannamei. An experiment was designed to generate inbred families the product of sibling matings, as well as groups of families with different inbreeding coefficients in three successive generations. The families came from a broodstock line selected for growth and survival. Inbreeding coefficients varied between 0 and 60.4%. A total of 16,361 shrimp from 320 families were produced. Data were analyzed using mixed linear model methodology and restricted maximum likelihood methods. Estimated change on BW per 10% increase on the inbreeding coefficient was −2.19 ± 0.41% (P &lt;0.001) relative to the mean of non‐inbred shrimp predicted from the model (19.63 g). Regression coefficient for grow‐out SR on inbreeding was not significant. Estimated change in SR per 10% increase on the inbreeding coefficient was −0.009 ± 0.006% (P = 0.108) relative to the mean of non‐inbred shrimp predicted from the model (81.72%). It is important to control inbreeding level in breeding programs.

Optimizing the design of small-sized nucleus breeding programs for dairy cattle with minimal performance recording

Dairy cattle breeding programs in developing countries are constrained by minimal and erratic pedigree and performance recording on cows on commercial farms. Small-sized nucleus breeding programs offer a viable alternative. Deterministic simulations using selection index theory were performed to determine the optimum design for small-sized nucleus schemes for dairy cattle. The nucleus was made up of 197 bulls and 243 cows distributed in 8 non-overlapping age classes. Each year 10 sires and 100 dams were selected to produce the next generation of male and female selection candidates. Conception rates and sex ratio were fixed at 0.90 and 0.50, respectively, translating to 45 male and 45 female candidates joining the nucleus per year. Commercial recorded dams provided information for genetic evaluation of selection candidates (bulls) in the nucleus. Five strategies were defined: nucleus records only [within-nucleus dam performance (DP)], progeny records in addition to nucleus records [progeny testing (PT)], genomic information only [genomic selection (GS)], dam performance records in addition to genomic information (GS+DP), and progeny records in addition to genomic information (GS+PT). Alternative PT, GS, GS+DP, and GS+PT schemes differed in the number of progeny per sire and size of reference population. The maximum number of progeny records per sire was 30, and the maximum size of the reference population was 5,000. Results show that GS schemes had higher responses and lower accuracies compared with other strategies, with the higher response being due to shorter generation intervals. Compared with similar sized progeny-testing schemes, genomic-selection schemes would have lower accuracies but these are offset by higher responses per year, which might provide additional incentive for farmers to participate in recording.

Evaluation of productive and reproductive performance of Black Bengal goat

The present study was conducted with a view to know the productive and reproductive parameters of Black Bengal goat in a nucleus breeding flock of Bangladesh Agricultural University, and two other regions i.e., Modhupur (Tangail) and Dimla, (Nilphamari). Data were collected on a regular basis from January 2011 to January 2012. The results showed that birth weight of kids was significantly affected by type of birth (p&lt;0.01), parity of dam (p&lt;0.01) and season of birth (p&lt;0.05) in three different regions. Yearling weight was varied significantly by sex of kid (p&lt;0.01) and season of birth (p&lt;0.05) in three different regions. Daily milk production was significantly affected by type of birth (p&lt;0.01), parity of dam (p&lt;0.01) and season of birth (p&lt;0.01). Litter size and age at first conception were significantly affected by parity of dam. Kid mortality was significantly affected by season of birth (p&lt;0.01) in nucleus flock. The results indicated that sex of kid, type of birth, parity of dam and season of birth influenced the productive and reproductive parameters in nucleus flock, Modhupur and Dimla and the performance also varied between nucleus flock and field levels.DOI: http://dx.doi.org/10.3329/bjas.v43i2.20704 Bang. J. Anim. Sci. 2014. 43 (2): 104-111

Genetic co-variation between resistance against both Caligus rogercresseyi and Piscirickettsia salmonis, and body weight in Atlantic salmon (Salmo salar)

Abstract Infectious and parasitic diseases are recognized worldwide as primary causes of economic losses in salmon production. Piscirickettsia salmonis and Caligus rogercresseyi are the main diseases affecting the Chilean salmon aquaculture. In this study, we used data from experimental challenges against P. salmonis and C. rogercresseyi in full- and half-sibs from 118 families belonging to a Salmo salar breeding nucleus. Resistance against P. salmonis (SRS) was defined as the day of death of each fish and C. rogercresseyi resistance (CAL) was measured as the parasite load. We also measured body weight (BW) in full-sibs of the tested fish. We used a multi-trait animal model to estimate (co)variance components and to calculate genetic parameters. For BW we included contemporary group (sex*tank) as factor and age as a covariate. In addition, tank was included as a factor and weight at the end of test as a covariate for SRS and CAL. The estimated heritabilities for BW, SRS and CAL were 0.4 (± 0.05), 0.18 (± 0.03) and 0.1 (± 0.03), respectively. The genetic correlations between BW–SRS, BW–CAL and SRS–CAL were − 0.19 (± 0.12), − 0.32 (± 0.14) and − 0.02 (± 0.17), respectively. The levels of genetic variation and the magnitude of the genetic correlations between resistance to P. salmonis , C. rogercresseyi and body weight found in the present study demonstrate the feasibility for the improvement of these traits simultaneously by means of selective breeding.

Selection of Black Bengal buck based on fertility and field progeny performance

This study was aimed for selection of Black Bengal bucks based on their fertility and the performance of their progeny in field condition. Data on buck were collected from a nucleus breeding flock and on progeny at field level. The traits considered were birth weight, weight at every 3-m interval up to 12 m of age. Average daily gain (g/day) on 90 progeny produced from 10 bucks and semen parameters on these bucks were collected. Heritability estimates obtained for birth weight, 3, 6, 9 and 12-m weights and average daily gain of progeny were found to be 0.41±0.08, 0.49±0.07, 0.46±0.08, 0.48±0.28, 0.50±0.09 and 0.49±0.06, respectively. The high heritability estimates of body weights indicated that there is a good opportunity for genetic improvement of this trait in a selection scheme. Heritability estimates obtained for semen volume, sperm concentration, sperm motility, sperm livability and normal sperm were 0.11±0.04, 0.25±0.07, 0.13±0.08, 0.12±0.08 and 0.06±0.03, respectively. The highest non return rate was observed in bucks of 32, 52 and 57 (66.67±6.75%). The lowest was found in buck 48 (41.67±5.65%). Among 10 bucks, first 3 top buck IDs were 52, 57 and 54 on the basis of BV at birth weight. Selection index of bucks for all traits was calculated and bucks were ranked accordingly. The highest selection index of three bucks ID were 52, 7 and 4 (1009.39, 934.595 and 865.808, respectively). It can be concluded that these top ranking three bucks can be selected and conserved for production and preservation of frozen semen for long term use.DOI: http://dx.doi.org/10.3329/bjas.v43i1.19379 Bang. J. Anim. Sci. 2014. 43 (1): 11-20

Genetic improvement of small ruminant local breeds with nucleus and inbreeding control: A simulation study

In small ruminant local breeds of Southern Europe genetic selection is often constrained by small population sizes, poor animal identification, inadequate animal performance and pedigree recording, and organizational shortcomings. Under these conditions nucleus breeding schemes can offer practical and cost effective solutions. The paper investigated genetic gain in stochastically simulated dairy small ruminant nuclei of 100, 200 and 400 females, supporting commercial populations from 500 to 5000 females. In the nucleus, a young sire selection scheme was used, with optimum contribution selection on a dairy trait, at an annual inbreeding rate of 0.3%, corresponding to a generation inbreeding rate of 0.001. Sires, both selected and not-select as sires of sires, after 1 year of use in the nucleus were utilized in the commercial population for one, or alternatively, 2 years. Annual genetic gain ranged from a minimum of 0.073 SD with 100 females nucleus supporting a commercial population of 500 females, to a maximum of 0.138 SD with a 400 females nucleus supporting a commercial population of 5000 females. Negligible differences in genetic gain were observed between nuclei and corresponding commercial populations. When sires were used for only 1 year in the commercial population, we observed 7.7 years of genetic lag with the nucleus, that increased to 8.2 years when sires were used for 2 years. Results showed that there are opportunities for selection even in populations of a few hundreds of females. Considering a specific breeds, or a specific farming area, a cost benefit analysis should be carried out to orientate the choice of nucleus size and strategy of use of sires.