Abstract: The economic weights for somatic cell score (SCS) were calculated using profit functions. Economic data were collected in the Latxa [Lacho] breed. Three aspects were considered: bulk tank milk payment, veterinary treatments due to high SCS and culling. All of them are nonlinear profit functions. Milk payment was based on the sum of the log-normal distributions of somatic cell count, and veterinary treatments on the probability of subclinical mastitis, which is inferred when individual SCS surpass some threshold. Both functions lead to non-standard distributions. The derivatives of the profit function were computed numerically. Culling was computed by assuming that a conceptual trait culled by mastitis (CBM) is genetically correlated to SCS. The economic weight considers the increase in the breeding value of CBM correlated to an increase in the breeding value of SCS, assuming genetic correlations ranging from 0-0.9. The relevance of the economic weights for selection purposes was checked by the estimation of genetic gains for milk yield and SCS under several scenarios of genetic parameters and economic weights. The overall economic weights for SCS range from -2.6--9.5 Euro per point of SCS, with an average of -4 Euro per point of SCS, depending on the expected average SCS of the flock. The economic weight was higher around the thresholds for payment policies. Economic weights did not change greatly with other assumptions. The estimated genetic gains with economic weights of 0.83 Euro per litre of milk yield and -4 Euro per point of SCS, assuming a genetic correlation of -0.30, were 3.85 litre and -0.031 SCS per year, with an associated increase in profit of 3.32 Euro. This represents a very small increase in profit (about 1%) relative to selecting only for milk yield. Other situations (increased economic weights, different genetic correlations) produced similar genetic gains and changes in profit. A desired-gains index reduced the increase in profit by 3%, although it could be greater depending on the genetic parameters. In conclusion, the inclusion of SCS in dairy sheep breeding programmes is of low economic relevance and recommended only if recording is inexpensive or for animal welfare concerns.
Abstract: Economic weights were estimated in two breeds (Latxa [Lacho] and Manchega) using economic and technical data collected from 41 Latxa and 12 Manchega dairy sheep flocks in Spain. The traits considered were fertility (lambing per year), prolificacy (number of lambs), milk yield (litres) and longevity (as productive life, in years). A linear function was used, relating these traits to the different costs in the flock. The variable costs involved in the profit function were feed and labour. From this function, economic weights were obtained. Labour was considered to be a constraint in the Latxa breed. Moreover, farm profits were unusually high, which probably means that some costs were not included according to the economic theory. For that reason, a rescaling procedure was applied constraining total labour time at the farm. Genetic gains were estimated with the resulting economic weights to test if they give any practical difference. Milk yield only as selection criterion was also considered. The medians of the estimated economic weights for fertility, prolificacy, milk yield and longevity were 138.60 Euro per lambing, 40.00 Euro per lamb, 1.18 Euro per litre, 1.66 Euro per year and 137.66 Euro per lambing, 34.17 Euro per lamb, 0.73 Euro per litre, 2.16 Euro per year under the linear approach in the Latxa and Manchega breeds, respectively. Most differences between breeds can be related to differences in production systems. As for the genetic gains, they were very similar for all economic weights, except when only milk yield was considered, where a correlated decrease in fertility led to a strong decrease in profit. In conclusion, the estimates are robust for practical purposes and that breeding programmes should consider inclusion of fertility. More research is needed to include other traits such as somatic cell score, milk composition and udder traits.
Abstract: Milk yield is the main selection objective and the most economically important trait of the Manchega sheep breeding program. The milk price at market depends on several factors, as fat and protein contents or somatic cell score. In this work, the economic weights of fat and protein yield, and fat and protein content were estimated in order to calculate the economic importance of these traits. Profit was described as the difference between incomes minus costs. The price of each trait was the reference milk price at market, since it was given as function of fat and protein contents. Costs of production for fat and protein was estimated in function of the energy requirements to produce 1 kg of fat and protein in milk. Economic weights were 7.18 and 7.59 euro/kg for fat and protein yields and 7.92 and 8.40 euro/percent for fat and protein contents. Highest energy requirements for fat production lead to a lower economic weight for that trait. Since milk yield of Manchega sheep is greater than 100 litres per lactation, improve fat and protein contents is more profitable as is showed by the economic weights.
Abstract: A total of 296627 lactation records which include milk, fat, protein yields (<i>leche120</i>, <i>KgG120</i>, <i>KgP120</i>) and fat and protein content (%<i>G120</i>, %<i>P120</i>) belonging to 102 herds of Manchega sheep breed were used to estimate the genetic parameters for milk traits. Because of the high number of data available, random samplings from the initial population were carried out. A multivariate animal model with repeated measures was used to estimate variance components. The model included comparison group herd-year-season of lambing, lambing number-age at lambing, number of lambs born and the period of time between lambing and the first test-day, as fixed effects and the additive genetic and permanent environmental as random effects. Estimated heritabilities were 0.16, 0.13, 0.14, 0.09 and 0.28 and repeatabilities were 0.37, 0.31, 0.35, 0.15 and 0.41 for <i>leche120</i>, <i>KgG120</i>, <i>KgP120</i>, %<i>G120</i> and %<i>P120</i>, respectively, which were lower than those found in other dairy sheep breeds and in previous studies in Manchega breed. Results from the samples were quite similar among them and with the results obtained from univariate animal models for each single trait using all data available. No lost in precision using random samplings with a multivariate model was reported. Genetic correlations were high and positive between yields and moderately positive between %<i>G120</i> and %<i>P120</i>, and negative or null between yields and composition. Because of the economic importance of %<i>G120</i> and %<i>P120</i>, it would be interesting to include both traits in the breeding objective.
Abstract: Economic weights for fertility, prolificacy, milk yield and productive life have been calculated for several farms in the Latxa and Manchega breeds. Economic data was gathered by management support technicians (Latxa) and personal interviews (Manchega). A profit linear function was used, including variable costs of feeding and labour, and variable incomes from cheese, milk and lamb sells. Other costs and incomes, either depending on the number of animals or fixed were also considered. A rescaling procedure was also applied, constraining total labour time in the farm, because very often dairy sheep farms are very work intensive, family-managed businesses who do not use foreign workers. Medians of economic weights (linear function) were, for Gipuzkoa region in Latxa, 133.17, 1.36, 48.94, 1.42 euros for fertility (per 100% increase), prolificacy (per additional lamb), milk yield (per additional litre) and productive life (per additional year). For farm B in Manchega weights were 125.27, 0.58, 17.34 and 3.32 respectively. Differences between breeds were clear and related to production systems. Small variations were observed within breeds. Use of the rescaling procedure did not change much the results.
Abstract: The general aim for animal breeding strategies is obtain future generations that will produce more efficiently under future production circumstances. Thus, genetic improvement programs should maximize profitability, taking into account socio-economic and productive environments. In this work, a review of the different methods to estimate economic weights (the value per unit improvement in a trait) is present. Three points are considered: (1) the criteria for deciding which traits to include in aggregate genotype and selection index, (2) the definition of profit functions and its most important characteristics and main problems, and (3) the difference in economic weights obtain for different perspectives in production (unit of product, animal, producer, investor and consumer) and some approaches to obtain consistent economic values.
Abstract: A total of 2376 Manchega ewes from 53 dairy flocks, subjected to official milk control, were used to study the influence of milking day, milking shift and milking type (hand or machine milking) on milk yield, somatic cell count (SCC), milk fat and milk protein. For each ewe the data of the monthly control are recording in two consecutive days, with the same method of milk recording. Milk fat and milk protein were determined by infrared spectrophotometry (MilkoScan 4000) and SCC was determined by flow cytometry (Fossomatic 5000). The results obtained for the different variables are within the expected ranges for the Manchega ewe. Statistical analysis showed that protein percentage was the variable less affected by factors studied such as milking day and milking shifts. On the other hand, repetitivity of the different variables was acceptable, mainly for the machine milking, except for milk fat, which showed an appreciable variability.
Abstract: Economic and productive data from Latxa and Manchega flocks are presented as a previous step to obtain economics weights. This work shows that the main problems are to record economic data and the variability between breeds. Total costs in Manchega are higher than in Latxa. The pasture-base production system used in Latxa leads to a lower feed costs (51,52 Euro/ewe in Latxa and 74 Euro/ewe in Manchega). More investments in accommodation and cheese production make fixed costs increase in Latxa (97,32 Euro/ewe in Latxa and 44,40 Euro/ewe in Manchega). The different economic environments for both breeds could result in different economic weights.
Abstract: Several methods have been developed to supplement the A4 method (according to ICAR standard) in order to achieve reasonable accuracy in estimating daily yields. In the present work, Fleischman method is evaluated to predict mineral composition yields of milk in Manchega dairy sheep. When mineral concentration increases along the lactation (ash, calcium, sodium, phosphorus, magnesium, iron, zinc), estimated yields by this method are right. In the other hand, a decrease of concentration along the lactation leads to a lower estimation. This is the case of copper and potassium.
