Breeding programs for smallholder sheep farming systems: I. Evaluation of alternative designs of breeding schemes

Village‐ and central nucleus‐based schemes were simulated and evaluated for their relative bio‐economic efficiencies, using Ethiopia's Menz sheep as example. The schemes were: village‐based 2‐tier (Scheme‐1) and 1‐tier (Scheme‐2) cooperative village breeding schemes, dispersed village‐based nuclei scheme (Scheme‐3), conventional 2‐tier central nucleus‐based scheme (Scheme‐4), and schemes linking a central nucleus and village multiplier nuclei with selection in central nucleus (Scheme‐5) or in both central and village nuclei (Scheme‐6). Among village‐based schemes, Scheme‐1 gave the highest genetic progress, while Scheme‐2 was economically the most efficient with genetic gain in the breeding objective of Birr 5.6 and a profit of Birr 37.2/ewe/year. The central nucleus schemes were more efficient than the village schemes. Scheme‐4 was the most efficient with genetic gain in the breeding objective of Birr 13.5 and a profit of Birr 71.2, but is operationally more difficult as it requires a very large central nucleus. The choice between village and central nucleus‐based schemes would depend on local conditions (availability of infrastructure, logistics and technical knowhow and support). Linking central nucleus with village‐based nuclei (Scheme‐6) would be a feasible option to overcome the operational difficulties of the conventional central nucleus scheme. If a village‐based breeding program is envisaged as should be the 1st step in most low‐input systems, then Scheme‐2 is the most efficient. To scale out to an entire Menz breed level, Scheme‐3 would be recommended.     

Optimal village breeding schemes under smallholder sheep farming systems

Despite challenges in the implementation of livestock genetic improvement programs in developing regions, including centralized nucleus breeding schemes, these programs can contribute to the improvement of the livelihood of smallholder farmers. In this paper, we present a community- or village-based breeding scheme in which breeding activities are carried out by communities of smallholder farmers. We evaluated genetic responses and the rate of inbreeding from alternative village sheep breeding schemes that were based on a survey of existing flock structure and breeding management in a sheep-barley system in Ethiopia. This survey showed that individual flock sizes were small, and that the majority of farmers practiced mixed grazing and uncontrolled mating of their flocks in communal grazing lands within villages. Here we evaluated within-village schemes (selection across flocks within a village) and across-village schemes (selection across villages) at different intensities of ram selection (i.e. proportions of rams selected, P). Our results showed that under within-village schemes, intensity of selection could not be increased (i.e. P could not be decreased below 0.149) when the rate of inbreeding was constrained to an acceptable level of 0.01, resulting in low genetic gain. The most optimal scheme was found to be across-village selection with at least three villages cooperating and P = 0.05. Our results also indicated that genetic gain from village breeding schemes with mass selection and BLUP selection is comparable. Village breeding schemes can make a significant contribution to the genetic improvement of livestock in Ethiopia and other developing countries.     

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.     

Design of a village breeding programme for a llama population in the High Andes of Bolivia

No national breeding programme for llamas is in place in Bolivia. Initiatives for genetic improvement are rarely found and are usually carried out by NGOs working in rural development or improvement of livestock production or research stations. Farmers in the Province of Ayopaya in the District of Cochabamba have formed a breeders’ organization with the aim of improving fibre production. In this study, a detailed outline of a breeding programme with a focus on organizational and technical details is described. Facing constraints like illiteracy of farmers, bad infrastructure and lack of finances, a simple breeding programme is set up. The breeding goal is a higher fleece weight while keeping the fleece quality at the current high level. Greasy fleece weight and fibre diameter are identified as main selection criteria. Mass selection of males is carried out. Selected males are either exchanged between farmers and used in the herds or are kept during the mating season in a central mating station owned by the breeders’ organization. Model calculations were carried out with the program zplan , which is based on a deterministic approach. zplan evaluates the genetic and economic efficiency of breeding strategies considering one cycle of selection. Scenarios with only intra-herd use, using only the central mating station or combinations of those were compared in terms of expected genetic gain and expected increase of inbreeding. Fastest genetic progress is achieved when the males are kept in a central mating station as the selection intensity is on a high level. Rates of inbreeding vary between 0.08 and 0.32% per generation.     

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.     

Evaluation of Egyptian sheep production systems: II. Breeding objectives for purebred and composite breeds

Objectives for this study were to estimate relative economic weights for performance traits for two native and two composite sheep breeds under two management systems in Egypt. Breeds studied were Rahmani (R), Ossimi (O), 3/4R-1/4Finnish Landrace (RFR), and 3/4O-1/4Finn (OFO); OFO and RFR were composite breeds. Management systems were one mating season per year (1M) and three mating seasons per 2 yr (3M). A dynamic computer model was used to simulate animal performance and enterprise efficiency and profit. Input parameters for the model were obtained from published results and analyses of data collected from experimental flocks of the same genetic stocks in Egypt. Responses for two measures of life-cycle feed conversion and one measure of enterprise profit were evaluated. Life-cycle feed conversion was calculated as kilograms of TDN input per kilogram of empty body weight output (TDN/EBW) and kilograms of TDN input per kilogram of carcass lean output (TDN/CLN). Profit was measured as annual gross margin/ewe (GM/EWE). Traits evaluated were conception rate (CR), lambing rate (LR), mortality rate (MR), mature weight (MW), and milk production (MK). Based on responses to percentage changes in trait means, CR was most important for TDN/EBW, followed by LR and MR. For TDN/CLN, LR, MR, and CR were most important. For GM/EWE, CR was most important, followed by LR, MW, and MR. In the systems studied, there was little response to changes in MK. Based on changes in GM/EWE per genetic standard deviation change, LR was most important, followed by CR, MR, MW, and MK in all systems. Relative economic weights for O and OFO were similar, as were weights for R and RFR. Differences in economic weights between management systems for the same breed were not large enough to justify separate selection lines within breeds.     

Breeding programmes for TSE resistance in British sheep. II. Assessing the impact on the prevalence and incidence of scrapie

By establishing a breeding programme for transmissible spongiform encephalopathie (TSE) resistance, there are plans to eradicate sheep TSEs from member states of the European Union (EU). In this paper, we used a simple age- and genotype-structured model to assess the impact of four breeding strategies on the prevalence and incidence of scrapie in the British sheep flock. The strategies ranged from the minimum EU requirements to compulsory implementation of the current National Scrapie Plan for Great Britain (NSP). All four strategies were predicted to reduce the prevalence and incidence of disease, though there was likely to be a delay of several years between the implementation of a breeding programme and the reduction in incidence. There were differences in the efficacy of the strategies, with the most stringent resulting in the greatest reduction in prevalence and incidence. However, the magnitude of the differences was not great, largely because all four strategies eliminated the VRQ allele, which is associated with a markedly higher risk of disease than any of the other alleles. Sensitivity analyses indicated that the model results were robust to selection bias when estimating the risk of infection; and that the efficacy of a breeding programme was unlikely to be compromised, unless the risk of infection is substantially underestimated by data on clinical disease.     

Breeding goals for the Kenya Dual Purpose goat. II. Estimation of economic values for production and functional traits

Economic values for production traits (milk yield, MY, kg; 12-month sale weight, LW, kg; consumable meat percentage, CMP) and functional traits (doe live weight, DoWT, kg; number of kids weaned, NKW; kidding frequency, KF; kidding rate, KR, %; doe weaning rate, DoWR, %; doe survival rate, DoSR, %; post-weaning survival rate, PoSR, %; pre-weaning survival rate, PrSR, % and; residual feed intake of yearlings, RFIgamma, kg and does RFId, kg) were estimated for the Kenya Dual Purpose goat (KDPG) for systems under two bases of evaluation. The production systems included smallholder low-potential (SLP), smallholder medium-potential (SMP) and smallholder high-potential (SHP), while the bases of evaluation considered were fixed flock-size and fixed feed resource. Under both bases of evaluation, economic values were highest in SMP apart from the economic values for feed intake-related traits (RFIy and RFId). In SMP, the economic values under fixed flock-size scenario were KSh 71.61 (LW), 20.90 (MY), 45.20 (CMP), 13.68 (NKW), 3.61 (KF), 6.52 (KR), 12.39 (DoWR), 22.96 (DoSR), 22.87 (PoSR), 13.18 (PrSR), -2.76 (RFIy) and -3.00 (RFId). The corresponding economic values under fixed feed resources scenario were KSh 73.28, 29.39, 45.20, 16.91, 4.76, 9.45, 13.84, 25.67, 25.15, 16.19, -2.76 and -3.00. Generally in all production systems, economic values for most traits were higher under fixed feed resource than under fixed flock-size scenario. In all systems, the economic values for most of the traits were sensitive to changes in prices of feed, milk and meat. The positive economic values for most traits under fixed flock-size scenario and fixed feed resource indicates that a unit increase in genetic merit for the traits would have a positive effect on the profitability of the systems.     

Breeding objectives for beef cattle used in different production systems: 1. Model development

A bio-economic model was developed to evaluate utilization of beef bulls in a variety of production systems. The model can simulate life-cycle production of both beef and dairy cow herds with or without an integrated feedlot system. The Markov chain approach is used to simulate herd dynamics. The herd is described in terms of animal states and possible transitions among them. Equilibrium herd structures of the integrated production systems are calculated in their stationary states. The economic efficiency of each system is a function of biological traits of animals and of management and economic parameters. The model allows estimation of marginal economic values for 16 traits separately in each system. The economic weight for each trait or direct and maternal trait component in each selection group and breed of interest is then calculated as the weighted sum of the economic values for the trait in all production systems in which the selection group has an impact. Weighting factors for each system are computed as the product of the number of discounted expressions for direct and maternal trait components transmitted in that system by the selection group and the proportion of total cows belonging to each system.     

高山草原绵羊放牧生态及消化代谢系列研究Ⅱ.放牧绵羊排尿量收集方法的新改进--纸尿裤法

利用纸尿裤法和常规法对６只甘肃高山细细毛羊成年竭羊，分别在祁连山东段高山草原７、８、１０、１月牧草生长的青草期、黄草期、葳草期共四期排尿量收集对比试验研究。实验表明，纸尿裤法收集收牧绵羊排尿量是常规法的１．６５－１．９４倍，纸尿裤法全面优于常规法，该方法的应用可以使放羯羊排尿量计量更加客观准确。     

Evaluation of Breeding Value and Selection of Bull Dams in the Danish Dairy Breeds: II. Model Calculations of the Effect of Bias on the Efficiency of Selection

Abstract

Alternative selection strategies in the bull dam path were investigated to reduce the magnitude of bias. The study's objective was to examine the effect of alternative strategies under the assumption of particular biases. Bias in the evaluation of bull dam estimated breeding values (EBVs) causes an estimated reduction of 32% in their genetic superiority, compared with the theoretical potential. Biased evaluations caused selection of too many bull dams from later lactations. Two alternative strategies were developed to account for existing bias. Results suggested that the influence of bias could be reduced. The estimated improvement in selection response was 11–13% higher than current practice. Problems with biased EBVs in conventional breeding schemes are discussed and a method to counteract bias from future breeding schemes is presented.