Effect of controlling future rate of inbreeding on expected genetic gain and genetic variability in small livestock populations

Context In the present study we assessed the use of average relationship as a means to control future rates of inbreeding in small cattle closed nucleus and its effect on genetic gain for milk yield as a means of managing genetic variability in livestock improvement programs. Aim The aim was to strike an ideal balance between genetic gain and loss of genetic variability for Sahiwal population. Methods A total of 8452 milk yield records of Sahiwal cows from National Sahiwal Stud, Kenya, were used to estimate breeding values and 19315 records used to estimate average relatedness of all individuals. The estimated breeding values and genetic relationships were then used to optimise individual genetic contributions between the best two males and the top 210 females in 2000–2008-year group, as well as between the best four, six and eight males and top, 420, 630 and 840 females based on estimated breeding values for lactation milk yield. Weights on genetic merit and average relationship considered in this study were (1, 0), (1, −300), (1, −500), (1, −1000) and (0, −1). Key results When the best sires were selected and used for mating disregarding average relationship with their mates i.e. (0, –1), genetic gain of up to 213 kg was realised accompanied by a rate of inbreeding per generation of 4%. Restricting average relationship alone i.e. (0, –1), resulted in a future rate of inbreeding of 1.6% and average merit of 154 when top two sires were used for breeding. At the same restriction level but using eight top sires, the rate of inbreeding per generation was 0.9% accompanied by an average merit of 128.2 kg. Controlling average relationship between mates resulted in increased genetic variability i.e. lower rate of inbreeding though average merit declined. Conclusion A rate of inbreeding per generation of <1% is required for a population to maintain its long-term viability. For this level to be attained, the size of the breeding population should be increased from the current two sires vs 210 dams to eight sires vs 840 dams. Implications Practical implications for closed nucleus programs such as the Sahiwal program in Kenya should include expanding the nucleus to comprise other institutional and privately-owned herds.

Characterization of indigenous chicken production systems in Rwanda

Characterization of indigenous chicken (IC) production systems in Rwanda was conducted from November 2015 to January 2016 with the aim of understanding socio-economic characteristics, management of IC, production parameters, feed resources, and constraints faced by farmers rearing IC. A survey involving 206 households was carried out in 5 districts with the highest populations of IC using structured questionnaires. Data were analyzed using SAS software. The results showed that the majority of respondents (62.4%) were males and 37.6% were females. The majority of respondents (83.6%) had formal education. All family members were involved in the chicken husbandry practices. However, women (78%) were highly responsible for IC management activities. The family size averaged 5 persons (ranging 2 to 13) per household. Land was privately owned by farmers (84%) with a mean holding of 0.87 ha per household. The production system was mainly extensive with minimum provision of supplementary feeds. Chickens were being housed in separate houses at night and mating was uncontrolled. Breeding and replacement stocks were mainly sourced from the hatching of eggs using broody hens (60.68% of respondents). There were no vaccination programs, and ecto- and endo-parasites control was done when need arose. Egg production, income generation, meat production, and production of breeding stock were the main reasons of keeping IC. The first 3 main challenges facing IC production were diseases outbreaks, lack of investment capital, and predators. Others challenges, such as feed shortage, thieves, fluctuation of market price, lack of information on poultry rearing, and lack of chicken houses, also were mentioned. The IC production constraints mentioned need urgent mitigation measures to sustain utilization of IC against the changing climatic and economic conditions. Therefore, individual, public institution, and non-governmental organization efforts are required to develop sustainable breeding objectives directed to functions of IC and production challenges faced in the systems.

Farmers' breeding practices and traits of economic importance for indigenous chicken in RWANDA

Data on breeding practices and traits of economic importance for the indigenous chicken (IC) were collected through personal interviews using structured questionnaires and direct observations of chicken management practices. The study was conducted from November 2015 to January 2016 in Rwamagana, Rulindo, Ruhango, Kicukiro and Muhanga districts of Rwanda. Data were collected and analysed through computation of indices, which represented a weighted average of all rankings of a specific trait. Spearman's non-parametric rank correlation was calculated for ranking of traits of economic importance to indicate the directional effects. The results on chicken ecotypes and their attributes showed that prolificacy, mature weight, disease tolerance, egg number and heat tolerance were highly preferred. The dwarf ecotype was most abundantly reared (38.84%) and considered to be significantly smaller and to have poorer growth rate, but to have better prolificacy than other indigenous chicken ecotypes. Selection of breeding cock and hen was based on disease tolerance, body weight at sexual maturity, body size and growth rate. In addition, for hen, mothering ability and egg fertility (Fer) were considered. Indices for the traits perceived by farmers as of primary economic importance were egg yield (0.093), disease tolerance (0.091), high growth rate (0.089), prolificacy (0.088), high body weight (0.087) and egg fertility (0.083). The most important traits considered by the marketers were body weight (BW), disease tolerance (Dtol), plumage colour (Pcol), egg yolk colour (EYC), meat quality (MQ), growth rate (GR) and egg yield (EY) whereas for consumers, meat quality, egg yolk colour, egg yield, body weight and growth rate were considered. Among traits perceived as important by farmers, a positive and significant correlation was found between BW and GR and Fer. Correlation was moderate for BW and prolificacy, drought tolerance (Drtol), Dtol and EYC. BW was negatively correlated with temperament (Temp), heat tolerance, Pcol and egg shell colour (ESC). Regarding marketers and consumers' preference rank correlation, positive and significant correlation was between BW and GR and MQ. As such, appropriate ecotypes (indigenous chicken) which have these characteristics need to be identified and utilised more based on their performance and adaption to the environment conditions to ensure efficient IC production.

Multiple criteria decision-making process to derive consensus desired genetic gains for a dairy cattle breeding objective for diverse production systems

Dairy cattle industries contribute to food and nutrition security and are a source of income for numerous households in many developing countries. Selective breeding can enhance efficiency in these industries. Developing dairy industries are characterized by diverse production and marketing systems. In this paper, we use weighted goal aggregating procedure to derive consensus trait preferences for different producer categories and processors. We based the study on the dairy industry in Kenya. The analytic hierarchy process was used to derive individual preferences for milk yield (MY), calving interval (CIN), production lifetime (PLT), mature body weight (MBW), and fat yield (FY). Results show that classical classification of production systems into large-scale and smallholder systems does not capture all differences in trait preferences. These differences became apparent when classification was based on productivity at the individual animal level, with high and low intensity producers and processors as the most important groups. High intensity producers had highest preferences for PLT and MY, whereas low intensity producers had highest preference for CIN and PLT; processors preferred MY and FY the most. The highest disagreements between the groups were observed for FY, PLT, and MY. Individual and group preferences were aggregated into consensus preferences using weighted goal programming. Desired gains were obtained as a product of consensus preferences and percentage genetic gains (G%). These were 2.42, 0.22, 2.51, 0.15, and 0.87 for MY, CIN, PLT, MBW, and FY, respectively. Consensus preferences can be used to derive a single compromise breeding objective for situations where the same genetic resources are used in diverse production and marketing circumstances.

Economic evaluation of progeny-testing and genomic selection schemes for small-sized nucleus dairy cattle breeding programs in developing countries

In developing countries minimal and erratic performance and pedigree recording impede implementation of large-sized breeding programs. Small-sized nucleus programs offer an alternative but rely on their economic performance for their viability. We investigated the economic performance of 2 alternative small-sized dairy nucleus programs [i.e., progeny testing (PT) and genomic selection (GS)] over a 20-yr investment period. The nucleus was made up of 453 male and 360 female animals distributed in 8 non-overlapping age classes. Each year 10 active sires and 100 elite dams were selected. Populations of commercial recorded cows (CRC) of sizes 12,592 and 25,184 were used to produce test daughters in PT or to create a reference population in GS, respectively. Economic performance was defined as gross margins, calculated as discounted revenues minus discounted costs following a single generation of selection. Revenues were calculated as cumulative discounted expressions (CDE, kg) × 0.32 (€/kg of milk) × 100,000 (size commercial population). Genetic superiorities, deterministically simulated using pseudo-BLUP index and CDE, were determined using gene flow. Costs were for one generation of selection. Results show that GS schemes had higher cumulated genetic gain in the commercial cow population and higher gross margins compared with PT schemes. Gross margins were between 3.2- and 5.2-fold higher for GS, depending on size of the CRC population. The increase in gross margin was mostly due to a decreased generation interval and lower running costs in GS schemes. In PT schemes many bulls are culled before selection. We therefore also compared 2 schemes in which semen was stored instead of keeping live bulls. As expected, semen storage resulted in an increase in gross margins in PT schemes, but gross margins remained lower than those of GS schemes. We conclude that implementation of small-sized GS breeding schemes can be economically viable for developing countries.

Evaluation of breeding objectives for purebred and crossbred selection schemes for adoption in indigenous chicken breeding programmes

1. The aim of the study was to evaluate the genetic and economic breeding objectives for an indigenous chicken (IC) breeding programme in Kenya. 2. A closed three-tier nucleus breeding programme with three breeding objectives and two selection schemes was simulated. The breeding objectives included IC dual-purpose (ICD) for both eggs and meat, IC layer (ICL) for eggs and IC broiler (ICB) for meat production. 3. Pure line selection scheme (PLS) for development of IC pure breeds and crossbreeding scheme (CBS) for the production of hybrids were considered. Two-and three-way crossbreeding strategies were evaluated under CBS and the impact of nucleus size on genetic gains and profitability of the breeding programme were investigated. 4. Males were the main contributors to genetic gains. The highest genetic gains for egg number (2·71 eggs) and growth traits (1·74 g average daily gain and 57·96 g live weight at 16 weeks) were realised under PLS in ICL and ICB, respectively. 5. The genetic response for age at first egg was desirable in all the breeding objectives, while that for fertility and hatchability were only favourable under ICL and PLS in ICD. Faecal egg count and immune antibody response had low, but positive gains except under PLS where the later was unfavourable. ICB was the most profitable breeding objective, followed by ICD and ICL under all the selection schemes. 6. Although PLS was superior in genetic gains and profitability and recommended in breeding programmes targeting ICL and ICB, a three line CBS should be considered in development of a dual-purpose breed. 7. Increasing the nucleus size beyond 5% of the IC population was not attractive as it resulted in declining profitability of the breeding programme.

Evaluation of basic and alternative breeding programs for Sahiwal cattle genetic resources in Kenya

The Sahiwal cattle breeding program in Kenya has been operational on an interim basis for over 45 years. However, there have been no systematic efforts undertaken to evaluate its suitability, or to examine how competitive it is compared with other alternative programs in terms of genetic and economic merit. The objective of this study was therefore to evaluate the genetic and economic success of the current basic and alternative Sahiwal cattle breeding programs in Kenya. The breeding programs examined were the current closed nucleus with two breeding strategies: a purebreeding (CNPURE) and a crossbreeding system (CNCROSS) involving Sahiwal sires and East African Zebu dams. An open nucleus with a certain proportion of pastoral-born Sahiwal bulls introduced into the nucleus herds to produce cows was simulated as an alternative breeding program. In this program only a purebreeding strategy (ONPURE) was considered. The breeding strategies were evaluated under two breeding objective scenarios that addressed traditional markets where animals are sold on body size/weight basis and the Kenya Meat Commission where payment is based on carcass characteristics. Sensitivity analyses to changes in nucleus size and gene contribution were also performed. The annual monetary genetic gain and profit per cow for all investigated breeding programs varied within breeding objectives. Closed nucleus purebreeding program was the most attractive economically but less competitive in regard to genetic superiority compared with either CNCROSS or ONPURE. Returns and profits were generally higher for the carcass characteristic basis compared with the body size/weight basis for all evaluated breeding strategies. Expansion of the nucleus size was not attractive because of the associated reduction in genetic and economic benefits. However, gradual importation of pastoral-born sires into the nucleus farms at the current nucleus proportion of 14% was both genetically and economically beneficial. The CNCROSS plays a complimentary role of facilitating the exploitation of trade-offs that exist between the Sahiwal and the locally better adapted East African Zebu, it also represents an intermediate phase in the on-going upgrading program.

Optimization of mate selection based on genotypic information with overlapping generations

The objective of this study was to develop a method to optimize the selection and mating decisions based on genotypic information with overlapping generations by applying mate selection algorithm. In this study, differential evolution algorithm was used to optimize numbers of mating between genotypes and the optimal numbers of males and females selected from each genotype over planning horizon. This method assumed a single biallelic QTL (Q and q) and was applied to a simple situation in a herd of pigs as an example. Four dominance degrees of gene: recessive, additive, complete-dominance and over-dominance were considered. For all dominance degrees, the frequency of the favourable allele in males selected for replacement increased rapidly. In contrast, the frequency of favourable allele in females selected for replacement increased more gradually. The superiorities in cumulative discounted performance (CDP) when the initial allele frequency was 0.5 over a case when the frequency was 0.05 over the planning horizon were greatly affected by dominance degrees. The CDP superiorities ranged from 24% for an over-dominant QTL to 91% for a recessive QTL.

Genetic and economic evaluation of a basic breeding programme for Kenya Boran cattle

The objective of this study is to describe the present organisational structure of Boran cattle breeding and develop a model breeding programme using a deterministic approach under the current structure of the Boran Cattle Breeders Society. A breeding unit of 13,000 cows supplying bulls to a commercial population of 39,000 cows was assumed. Selection criteria used were growth and reproduction traits while breeding objective traits targeted were growth, carcass, reproduction, survival, milk yield and feed intake traits. Higher selection intensity was possible for breeding sires resulting in higher genetic gains compared to dams even though selection accuracies were generally low. Annual genetic gains were positive except for dressing percentage, cow survival rate, and age at first calving. However, a reduction of age at first calving by 9.5 days obtained a return of Ksh 49.76. The overall monetary genetic gain obtained was Ksh 84.89 with a profit per cow per year of Ksh 377.98. The basic breeding programme could be expanded to accommodate a larger population of Boran cattle. The implications of the results are also discussed.

Genetic and phenotypic parameters and annual trends for growth and fertility traits of Charolais and Hereford beef cattle breeds in Kenya

This study estimated genetic and phenotypic parameters and annual trends for growth and fertility traits of Charolais and Hereford cattle in Kenya. Traits considered were birth weight (BW, kg), pre-weaning average daily gain (ADG, kg/day) and weaning weight (WW, kg); calving interval (CI, days) and age at first calving (AFC, days). Direct heritability estimates for growth traits were 0.36 and 0.21; 0.25 and 0.10; 0.23 and 0.13 for BW, ADG and WW in Charolais and Hereford, respectively. Maternal heritability estimates were 0.11 and 0.01; 0.18 and 0.00; 0.17 and 0.17 for BW, ADG and WW in Charolais and Hereford, respectively. Direct-maternal genetic correlations ranged between -0.46 and 1.00; -0.51 and -1.00; -0.47 and -0.39 for BW, ADG and WW in Charolais and Hereford, respectively. Genetic correlations ranged from -0.99 to unity and -1.00 to unity for growth and fertility traits respectively. Prospects for improvement of growth and fertility traits exist.

Effect of parental genotypes and paternal heterosis on litter traits in crossbred goats

The effect of parental genotype and paternal heterosis on litter size (LS), total litter birth weight (TLW) and average litter birth weight (ALW) was analysed utilizing data from a crossbreeding programme involving the exotic German Fawn goats and local Katjang goats in Malaysia. In this study, these traits were regarded as traits of the litter to consider the effect of service sire genotype. The results revealed that LS was significantly influenced by the genotype of sire. The genotypes of sire and dam had significant effects on TLW and ALW. Estimates of crossbreeding parameter showed significant and negative influence of paternal heterosis on TLW and ALW while there was no significant effect of paternal heterosis on LS. The results of this study stress the need to reconsider the use of local males in the tropics.

Analysis of production objectives and breeding practices of dairy goats in Kenya

Production objectives and breeding practices of smallholder households participating in dairy goat breeding projects were analysed in relation to their ability to bring about sustainable genetic improvement in the dairy goat flocks in Kenya. A stratified survey involving 311 goat keepers in 4 project sites was used. This employed both qualitative and quantitative research methods to get a holistic view of dairy goats, and take into account the full array of contributions of dairy goats to the smallholder households. Milk production and sales of breeding stock were high priority functions for the objective to create a financial buffer. The breeding objective traits that farmers perceived as being of primary importance were milk yield, growth rate, body size, fertility and disease tolerance. There were logical trade-offs in the choice of these traits by farmers. Female dairy goats were mainly culled due to old age, poor fertility, small body size and poor health. Farmers did not place a large significance on unsatisfactory milk performance when culling female goats, mainly due to the very small production size and the high demand existing for breeding animals. Factors affecting milk yield and flock size presented satisfied a P<0.1 significance level. The performance levels of dairy goats were mainly influenced by breeding strategies and the resource availability at the farm level. The optimisation of genotype x environment interactions remains the biggest challenge given the objectives set by the farmer.

Genetic and economic evaluation of Japanese Black (Wagyu) cattle breeding schemes

Deterministic simulation was used to evaluate 10 breeding schemes for genetic gain and profitability and in the context of maximizing returns from investment in Japanese Black cattle breeding. A breeding objective that integrated the cow-calf and feedlot segments was considered. Ten breeding schemes that differed in the records available for use as selection criteria were defined. The schemes ranged from one that used carcass traits currently available to Japanese Black cattle breeders (Scheme 1) to one that also included linear measurements and male and female reproduction traits (Scheme 10). The latter scheme represented the highest level of performance recording. In all breeding schemes, sires were chosen from the proportion selected during the first selection stage (performance testing), modeling a two-stage selection process. The effect on genetic gain and profitability of varying test capacity and number of progeny per sire and of ultrasound scanning of live animals was examined for all breeding schemes. Breeding schemes that selected young bulls during performance testing based on additional individual traits and information on carcass traits from their relatives generated additional genetic gain and profitability. Increasing test capacity resulted in an increase in genetic gain in all schemes. Profitability was optimal in Scheme 2 (a scheme similar to Scheme 1, but selection of young bulls also was based on information on carcass traits from their relatives) to 10 when 900 to 1,000 places were available for performance testing. Similarly, as the number of progeny used in the selection of sires increased, genetic gain first increased sharply and then gradually in all schemes. Profit was optimal across all breeding schemes when sires were selected based on information from 150 to 200 progeny. Additional genetic gain and profitability were generated in each breeding scheme with ultrasound scanning of live animals for carcass traits. Ultrasound scanning of live animals was more important than the addition of any other traits in the selection criteria. These results may be used to provide guidance to Japanese Black cattle breeders.

Effect of direct and indirect selection criteria for efficiency of gain on profitability of Japanese Black cattle selection strategies1

The objective of this study was to determine the effect of use of residual feed intake (RFI) and the blood concentration of IGF-I (IGF) as selection criteria for efficiency of gain on profitability of Japanese Black cattle selection strategies with restricted test capacity. A breeding objective that integrated the cow-calf and feedlot segments was considered. Selection strategies were defined that differed in whether information on IGF and RFI during performance testing (RFIpt) was used to make selection decisions and in the number of animals measured for IGF. In all strategies, sires were selected from the proportion chosen during the first selection stage (performance testing), modeling a 2-stage selection process. The effect on genetic gain and profitability of variations in test capacity, of the genetic correlations of IGF with marbling score (MS) and RFIpt, and nonzero economic values for and, hence, inclusion of RFI of the cow and feedlot animals in the breeding objective was examined. Additional genetic gain and profitability were generated when information on IGF concentration and RFIpt in the performance-tested young bulls was included in the selection criteria. Profit per cow was optimal when measurement of IGF and RFIpt were incorporated together in the selection index. Increasing test capacity resulted in an increase in genetic gain in all strategies, and profit per cow was optimal in all strategies when 900 places were available for performance testing. Profit per cow was more sensitive to changes in the genetic correlation between IGF and MS than between IGF and RFIpt, especially when more animals were measured for IGF, or else the favorable relationship between IGF and MS had no significant effect on profit per cow. Additional genetic gain and profitability were generated in each strategy when RFI of the cow and feedlot animals were included in the breeding objective with nonzero economic values. These results may be used to provide guidance to Japanese Black cattle breeders and, in the absence of more breed-specific information, may also have application in other Japanese beef breeds.

Genetic relationships between growth and carcass traits and profitability in Japanese Brown cattle1

The objectives of this study were 1) to examine the genetic relationship between growth and carcass traits and carcass price (CaP) and profitability in Japanese Brown cattle, 2) to estimate economic values of carcass and growth traits as regression coefficients of price and profit traits on growth and carcass traits using a multiple regression model, and 3) to compare direct and indirect predictions of the genetic merit of profit obtained from multitrait analysis and selection index, respectively. Growth and carcass traits considered in this study were ADG during the feedlot period, CWT, LM area (LMA), rib thickness (RT), subcutaneous fat thickness (SFT), and marbling score (MS). Carcass price was evaluated as a price trait independent of its influence on profit. Profit traits were defined as 1) net income per year (PROF1), 2) net income per year/energy requirement (PROF2), and 3) net income per year minus feed costs (PROF3). Correlations between direct and indirect predictions were estimated based on EBV of sires and dams with progeny records. The heritability estimate for CaP was 0.41. The heritability estimates for profit traits were high and were 0.62, 0.66, and 0.60 for PROF1, PROF2, and PROF3, respectively. The genetic correlations between CaP and ADG, CWT, LMA, RT, SFT, and MS were 0.19, 0.14, 0.30, 0.38, -0.11, and 0.98, respectively. Among the profit traits, PROF1 had the greatest genetic correlations with growth and carcass traits. The correlations with ADG, CWT, LMA, RT, SFT, and MS were 0.30, 0.21, 0.24, 0.39, -0.01, and 0.69, respectively. These estimates indicate that use of profit traits as a selection criterion may promote desirable correlated responses in growth and carcass traits. The economic values for growth and carcass traits estimated relative to CaP and each profit trait differed because of the apparent differences in the description of these traits. The correlations between EBV for the same profit traits from direct and indirect predictions were high and ranged from 0.818 to 0.846 based on EBV of sires and from 0.786 to 0.798 based on EBV of dams. The strong correlations between direct and indirect predictions for profit indicate that there is no advantage to selecting directly for profit compared with an index with all of the component traits.

Evaluation of the efficiency of alternative two-tier nucleus breeding systems designed to improve meat sheep in Kenya

A deterministic approach was used to genetically and economically evaluate the efficiency of five two-tier nucleus breeding systems for meat sheep in Kenya. The nucleus breeding systems differed in terms of whether the system was closed or open, in the type of animals that were involved in the movement of genetic superiority and in the number of selection pathways in each system. These systems were compared under four alternative breeding objectives based on monetary genetic gain and profit per ewe. The first objective simulated a situation where the flock size cannot be increased due to non-feed related constraints (FLOCK). The second specifically assumed that the flock size is restricted due to limited amount of feed resources (FEED). The third and fourth objectives assumed that sheep performed only tangible roles (TR) and both tangible and intangible roles (IR) in the production system respectively. Monetary genetic gains were highest for all objectives in an open nucleus system with a certain proportion of commercial-born ewes being introduced in the nucleus while at the same time utilizing young rams from the nucleus to breed sires and dams for the nucleus and commercial sector (ONyre). Utilizing young rams in a closed nucleus system for the dissemination of superior genes resulted in higher annual monetary genetic gain than utilization of old rams. Profit per ewe was significantly higher for FLOCK and IR in ONyre. In a closed system that allowed for downward movement of dams from the nucleus to the commercial sector to breed sires and dams, profit per ewe was highest for FEED and TR. The success of a nucleus breeding system should also focus on the profitability and logistics of establishing it. The implication of these results on the choice of two-tier nucleus breeding systems for the improvement of meat sheep is discussed.

Effect of carcass price fluctuations on genetic and economic evaluation of carcass traits in Japanese Black cattle1

The objectives of this study were 1) to investigate the effect of changes in carcass market prices due to bovine spongiform encephalopathy (BSE) occurrences on estimates of genetic parameters and economic weights for carcass traits; and 2) to compare direct and indirect approaches for prediction of genetic merit of Japanese Black cattle for profitability of their progeny. The direct approach utilized estimated breeding values of carcass prices, whereas in the indirect approach, selection indices were constructed as products of economic weights and breeding values of component traits. Data were composed of 80,191 carcass records divided into 5 periods based on changes in carcass prices as a result of occurrences of BSE in Japan and the United States. The periods ranged from a period before occurrence of BSE in Japan to a period of beef import restrictions and a rise in prices. Carcass traits analyzed included HCW, LM area, rib thickness, subcutaneous fat thickness, and marbling score (MS). Price traits included carcass unit price and carcass sale price. Estimates of heritability for price traits were moderate (0.32 to 0.46) and slightly sensitive to changes in carcass market prices. Genetic correlations of HCW and LM area with price traits increased and that between MS and carcass sale price decreased with period, whereas estimates of genetic correlation between MS and carcass unit price were high in all periods (0.96 to 0.98). Economic weights for carcass traits varied with periods because carcass prices were highly sensitive to economic importance of traits. Nevertheless, correlations between within-period breeding values for price traits estimated using direct and indirect approaches were high (0.92 to 0.99). This result indicates that selection realized by direct and indirect approaches will provide very similar results. A comparison among within-approach breeding values estimated in different periods showed that the largest differences in breeding values of sires for price traits were between the periods after occurrences of BSE in Japan and in the United States. Economic effects of BSE occurrences influenced the importance of carcass traits and economic merits of price traits through a change of carcass prices from period to period, irrespective of the approach taken in determining the genetic merit of breeding animals for profitability of their progeny.

Research partnerships in relation to topics in animal breeding and genetics1

A total of 1,628 papers presented at the sixth and seventh World Congresses on Genetics Applied to Livestock Production were categorized into 20 topics according to research subjects. The aim was to determine, in relation to various topics in animal breeding and genetics, the forms of partnerships and the degree of attention given in different continents. North-North partnerships (defined as cooperation between and within developed countries) had a 68.80% representation of research papers presented, whereas North-South partnerships (cooperation between developed and developing countries) had the least representation with only 8.23% of papers. Asia contributed the most research papers in biochemical genetics, whereas Australia lead in research papers on breeding for fiber and fur. Europe contributed the most to the remaining topics, and Africa usually, but not always, contributed the least to most research topics. This study provided a useful indication of the current state of literature in animal breeding and genetics and will be useful to animal breeding and genetics researchers worldwide as they chart the way forward for research and development in the field of genetics applied to livestock production in different continents.

Economic values for production and functional traits and assessment of their influence on genetic improvement in the Boran cattle in Kenya

Economic values for production (sale weight in steers, SWs, kg and heifers, SWh, kg; dressing percentage, DP; consumable meat percentage, CMP and milk yield, MY, kg) and functional (cow weight, CoWT, kg; cow survival rate, CoSR, %; postweaning survival rate, PSR, %; feed intake of cows, FIc, heifers, FIh and steers, FIs, kg DM) traits were estimated for six production systems utilizing the Boran breed in Kenya. The influence of the estimated economic values on genetic improvement was also assessed using different selection indices. The six production systems were described according to their sale age, levels of input and final goal, namely, short-fed medium input beef (SMB); long-fed medium input beef (LMB); short-fed high input beef (SHB); long-fed high input beef (LHB); long-fed low input dual purpose (LLD); and long-fed medium input dual purpose (LMD). Two evaluation bases were considered: fixed herd size and fixed pasture input. In the fixed herd-size situation, the economic values for production (except MY in beef systems) and functional traits (except FI in all systems) were positive meaning a unit increase in genetic merit of these traits had greater influence on revenues than costs. As expected, the economic value for MY was negative in the pure beef systems (SMB, LMB, SHB and LHB) and positive in the dual-purpose systems (LLD and LMD). When compared with the economic values estimated in the fixed herd-size situation, in the fixed pasture input situation they were lower for feed intake in the three classes of livestock and other traits related to it in all systems. These traits were CoSR, CoWR, PSR, CoWT, SWh and MY. The economic values for CoWT in LLD and LMD were negative (KSh -11.14 and -15.33 respectively). The economic values did not influence much the direction of the genetic response in each trait in the different production systems. However, the magnitude of the actual gain was dependent on the index applied. The magnitude of the economic values for production and functional traits estimated in this study suggest that genetic improvement of these traits will have a positive effect on profitability of Boran cows kept in dual-purpose systems and when herd size is restricted. In beef systems, genetic improvement of MY will have a negative effect on profitability, especially when restrictions on herd size and feed exists.

Economic values for resistance to gastrointestinal helminths in meat sheep in Kenya

Economic values for resistance to gastrointestinal (GI) helminths in meat sheep were estimated based on previously published genetic and phenotypic parameters in a selection index objectively optimizing gains on yearling weight (YW). A two-trait index of YW and faecal egg count (FEC) were considered when accounting only for tangible roles of sheep production using individual records for index calculation (scheme 1) or including individual, sire, dam and male paternal half-sib information (scheme 2). Schemes 3 and 4 were similar to schemes 1 and 2, respectively, but accounted for both tangible and intangible roles of sheep production. Economic values within each scheme were estimated for five breeding objectives as follows: (i) index response in YW equals response from single trait selection, (ii) index response in YW is maximum, (iii) the level of FEC was held constant, (iv) A predetermined response of -0.22 (x1000) eggs per gram was assumed and (v) Monetary value of response in FEC is minimum. All estimated economic values were negative, and were Kenya Shillings (KSh) -34.90 (US dollar -0.50), 0.00, -92.20 (US dollar -1.32), -153.31 (US dollar -2.19) and -47.90 (US dollar -0.68), respectively, for options 1-5 in scheme 1. In all schemes the breeding options ranked 4, 3, 5 and 1 in descending order; however, options 1 and 5 exchanged positions in schemes 2 and 4. Economic values were responsive to changes in heritability of FEC and genetic correlation between the two traits. The magnitude of the economic values reflects the importance of including resistance to GI helminths in the breeding objectives for meat sheep in different production systems.

Genotype × environment interaction effects on carcass traits in Japanese Black cattle1

The importance of genotype x environment (region or management system) interactions for carcass traits in Japanese Black cattle was investigated using both univariate and multivariate animal models. The univariate approach was used mainly to test the significance of interaction effects. The multivariate approach was used to estimate genetic correlations, which indicated the magnitude of genotype x environment (GE) interactions. The more a genetic correlation deviates from 1, the larger the interaction. From the univariate approach, the addition of genotype x environment (region or management system) interaction (co)variance components resulted in an improved fit of the model for all traits in both cases (P < 0.001). However, estimates of genetic correlation between regions obtained from the multivariate approach for hot carcass weight, LM area, rib thickness, s.c. fat thickness, and marbling score were 0.97, 0.95, 0.93, 0.97, and 0.93, respectively. The corresponding estimates between management systems were 0.84, 0.92, 0.84, 0.90, and 0.97, respectively. These results indicate that GE interaction effects on carcass traits of Japanese Black cattle may be biologically unimportant. Therefore, breeding values obtained using the multivariate method would rank sires similarly in all environments. Consequently, carcass traits measured in these two different regions or management systems can be treated as the same traits.

Evaluation of closed adult nucleus multiple ovulation and embryo transfer and conventional progeny testing breeding schemes for milk production in tropical crossbred cattle

The potential benefits of closed adult nucleus multiple ovulation and embryo transfer (MOET) and conventional progeny testing (CNS) schemes, and the logistics of their integration into large-scale continuous production of crossbred cattle were studied by deterministic simulation. The latter was based on F1 (Bos taurus x Bos indicus) production using AI or natural mating and MOET, and continuous F2 production by mating of F1 animals. The gene flow and the cumulative discounted expressions (CDES) were also calculated. Both schemes had 8, 16, 32, or 64 dams with 2, 4, 8, 16, or 32 sires selected. In the MOET nucleus scheme (MNS), the test capacity was 1, 2, 8, or 16 offspring, and the number of matings per dam per year was 1, 2, or 4. A scheme of 8 sires with 64 dams and a test capacity of 4 female offspring per dam per year resulted in an annual genetic gain (in phenotypic standard deviation) of 0.324 and 0.081 for MNS and CNS, respectively. In the MNS, there was substantial genetic gain with a relatively small number of animals compared with a CNS. The F1 had the highest, and the F2 scheme the lowest CDES. However, a very large number of B. indicus females would be required in the F1 scheme. This scheme may not be practical under conditions in developing countries. The F2 scheme was logistically attractive because it produces its own replacements, and the number of B. taurus females required would be easy to attain. Accompanying technical and financial constraints of nucleus schemes should be addressed before applying them.

Economic evaluation of Hereford cattle breeding schemes incorporating direct and indirect measures of feed intake

A deterministic approach was used to evaluate the effect of incorporating direct and indirect measures of feed intake as additional selection criteria in breeding schemes for Hereford cattle. A 2-tier nucleus breeding scheme consisting of a nucleus and a commercial sector was assumed. Four breeding objectives specific to Australian Hereford cattle were considered. These addressed production systems that targetted 4 markets (Domestic Supermarket, 'Hereford Prime', Short-fed Export, and Long-fed Export). The breeding objectives differed especially in the feed cost involved for differing amounts of grain finishing and in the extent to which marbling is valued by the market (from none to quite a lot). The breeding schemes evaluated differed in the measures available for use as selection criteria. The schemes ranged from one that utilised growth, scanned carcass and fertility criteria currently available to Australian cattle breeders (Scheme 1) to one which also incorporated residual feed intake (RFI) and blood serum insulin-like growth factor I (IGF-1) criteria (Scheme 5). The latter scheme included selection of sires for the nucleus using a 2-stage selection process, with a proportion of bulls selected after weaning for measurement of RFI. Schemes utilising either IGF-1 or RFI or both as criteria generated additional genetic gain and profitability for each breeding objective. Profit was optimal across all the Hereford cattle breeding objectives when the top 5% of bulls was measured for RFI after being selected on an index incorporating IGF-1 and other information available on the bull and its relatives at a young age. Further increase in the proportion of bulls measured for RFI for consideration in the second selection stage resulted in a slow decline in profit per cow in the population and a flat response in genetic gain. In the absence of more breed-specific information, these results may also have application in breeds other than Herefords.

Influence of production circumstances and economic evaluation criteria on economic comparison of breeds and breed crosses

The ranking of genotypes (i.e., breeds and breed crosses) for economic performance depends on the production circumstances of the herd and the criteria for economic evaluation. In this study, the effects of evaluation criteria and production circumstance are quantified using data from the literature on six genotypes. The economic evaluation criteria measured at herd level included lifetime profit and lifetime profit expressed per day of calving interval, per day of productive lifetime, per day of total herd life, per unit of milk, and per unit of feed energy. Four production circumstances were studied; these circumstances included constraints on the output of milk and on herd use of concentrates, roughages, and both concentrates and roughages. Profit was determined based on the sale of milk, calves, cull cows, and heifers and the expenses incurred for concentrates and roughages, animal deaths, milking time, interest, and other inputs. Results indicate that production circumstances and evaluation criteria largely influence the ranking of genotypes and, therefore, the outcome of economic comparisons. The genotype that ranks the best under a certain criteria and circumstance ranks differently when these situations are altered. In economic comparisons of genotypes aimed at offering recommendations for implementation in smallholder dairy production systems in the tropics, the choice of the evaluation criteria should be determined by the limitation or constraint that characterizes the area where the genotypes are to produce or are currently producing. For example, for situations in which feed availability is limiting, genotypes should be ranked on total profit per unit of feed energy.