Abstract:An economic selection index was developed for Beefmaster cattle in a general-purpose production system in which bulls are mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Genetic parameters were obtained from the literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit fu… Show more
“…Most EV for the CW is negative, according to several studies (Wolfová et al, 2005;Ochsner et al, 2017;Simões et al, 2020). Larger animals are not always the most suitable and profitable to production systems, due to the high energy required for their maintenance and the consequent increased feeding costs.…”
Section: Discussionmentioning
confidence: 99%
“…Although CW and WW are usually reciprocally antagonistic in relation to selection objectives, i.e., it is ideal to increase WW without raising CW, as the correlation assumed between them is not equal to the unit, it is possible to have progress in both traits simultaneously in a balanced way in the selection index (Ochsner et al, 2017). The selection for the direct effect of WW is relevant in the production of beef cattle because it represents the individual growth capacity.…”
Section: Discussionmentioning
confidence: 99%
“…Several studies include WW as a selection objective (MacNeil et al, 1994;Wolfová et al, 2005;Bittencourt et al, 2006;Matjuda et al, 2014;Ochsner et al, 2017). The RE weighting is variable, according to the systems adopted and the final product.…”
Section: Discussionmentioning
confidence: 99%
“…Some authors have argued for the use of long-run production costs and product prices in the construction of breeding objectives (e.g., Ochsner et al, 2017;Barron Lopez, 2013) rather than the use of one of the values from a single point in time as was done in this study. Because CW and STAY impact the inputs and outputs and were major contributors to the breeding objectives, the sensitivity of their economic values to changes in prices was evaluated in this study.…”
The objective was to develop selection indexes for Nellore cattle raised in full-cycle production system in the Brazilian Pantanal. The resulting offspring are retained as replacements or sold at two years of age. Preliminary analyses explored effects of scale on economic values (EV). However, given the available data, these effects were very small. Presented herein are results from a simulated system consisting of 5,000 cows with all animals maintained on pasture as is typical in Pantanal. The EV were determined by approximating the partial derivatives of the profit function, changing one trait at a time, by one unit, while keeping the other traits constant. Traits in the breeding objective were mature cow weight, direct and maternal weaning weight, postweaning average daily gain, subcutaneous fat depth, longissimus muscle area, and stayability. Economic values were calculated on the basis of number of animals (per head), number of animal units, and arroba of carcasss weight. Regardless of the basis, maternal weaning weight and subcutaneous fat depth made negligible contributions to the breeding objective. Proportions of variation in the breeding objectives (per head, per animal unit, per arroba) explained by cow weight, direct weaning weight, postweaning average daily gain, stayability, and longissimus muscle area were:
“…Most EV for the CW is negative, according to several studies (Wolfová et al, 2005;Ochsner et al, 2017;Simões et al, 2020). Larger animals are not always the most suitable and profitable to production systems, due to the high energy required for their maintenance and the consequent increased feeding costs.…”
Section: Discussionmentioning
confidence: 99%
“…Although CW and WW are usually reciprocally antagonistic in relation to selection objectives, i.e., it is ideal to increase WW without raising CW, as the correlation assumed between them is not equal to the unit, it is possible to have progress in both traits simultaneously in a balanced way in the selection index (Ochsner et al, 2017). The selection for the direct effect of WW is relevant in the production of beef cattle because it represents the individual growth capacity.…”
Section: Discussionmentioning
confidence: 99%
“…Several studies include WW as a selection objective (MacNeil et al, 1994;Wolfová et al, 2005;Bittencourt et al, 2006;Matjuda et al, 2014;Ochsner et al, 2017). The RE weighting is variable, according to the systems adopted and the final product.…”
Section: Discussionmentioning
confidence: 99%
“…Some authors have argued for the use of long-run production costs and product prices in the construction of breeding objectives (e.g., Ochsner et al, 2017;Barron Lopez, 2013) rather than the use of one of the values from a single point in time as was done in this study. Because CW and STAY impact the inputs and outputs and were major contributors to the breeding objectives, the sensitivity of their economic values to changes in prices was evaluated in this study.…”
The objective was to develop selection indexes for Nellore cattle raised in full-cycle production system in the Brazilian Pantanal. The resulting offspring are retained as replacements or sold at two years of age. Preliminary analyses explored effects of scale on economic values (EV). However, given the available data, these effects were very small. Presented herein are results from a simulated system consisting of 5,000 cows with all animals maintained on pasture as is typical in Pantanal. The EV were determined by approximating the partial derivatives of the profit function, changing one trait at a time, by one unit, while keeping the other traits constant. Traits in the breeding objective were mature cow weight, direct and maternal weaning weight, postweaning average daily gain, subcutaneous fat depth, longissimus muscle area, and stayability. Economic values were calculated on the basis of number of animals (per head), number of animal units, and arroba of carcasss weight. Regardless of the basis, maternal weaning weight and subcutaneous fat depth made negligible contributions to the breeding objective. Proportions of variation in the breeding objectives (per head, per animal unit, per arroba) explained by cow weight, direct weaning weight, postweaning average daily gain, stayability, and longissimus muscle area were:
“…Ochsner et al [44, 45] outlined procedures on how to develop a maternal economic selection index ($M) given EPD information. These procedures were followed based on selection objective weightings described by MacNeil [46].…”
Background
Recessive loss-of-function (LOF) alleles at genes which are essential for life, can result in early embryonic mortality. Cattle producers can use the LOF carrier status of individual animals to make selection and mate allocation decisions.
Methods
Two beef cattle breeding strategies i.e. (1) selection against LOF carriers as parents and (2) simultaneous selection and mate allocation to avoid the occurrence of homozygous offspring in three scenarios, which differed in number and frequency of LOF alleles were evaluated using the mate selection program, MateSel. Scenarios included (a) seven loci with high-frequency LOF alleles, (b) 76 loci with low-frequency LOF alleles, and (c) 50 loci with random high- and low-frequency LOF alleles. In addition, any savings resulting from the information obtained by varying the percentage (0–100%) of the herd genotyped, together with segregation analysis to cover ungenotyped animals, were calculated to determine (1) which percentage optimized net profit for a fixed cost of genotyping ($30/test), and (2) the breakeven cost for genotyping.
Results
With full knowledge of the LOF alleles carried by selection candidates, the most profitable breeding strategy was always simultaneous selection and mate allocation to avoid homozygous affected offspring (
aa
) as compared to indiscriminate selection against carrier parents (
Aa
). The breakeven value of genotyping depended on the number of loci modeled, the LOF allele frequencies, and the mating/selection strategies used. Genotyping was most valuable when it was used to avoid otherwise high levels of embryonic mortalities. As the number of essential loci with LOF alleles increased, especially when some were present at relatively high minor allele frequencies, embryonic losses increased, and profit was maximized by genotyping 10 to 20% of a herd and using that information to reduce these losses.
Conclusions
Genotyping 100% of the herd was never the most profitable outcome in any scenario; however, genotyping some proportion of the herd, together with segregation analysis to cover ungenotyped animals, maximized overall profit in scenarios with large numbers of loci with LOF alleles. As more LOF alleles are identified, such a mate selection software will likely be required to optimally select and allocate matings to balance the rate of genetic gain, embryonic losses, and inbreeding.
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