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Selection for milk production later in lactation (changing the shape of the lactation curve) also may provide an opportunity to increase milk production during a time in an animal's life when energy allocation is possible. Keywords: Genetic Selection; Estimated Breeding Value; Milk Composition EN Genetic Selection Estimated Breeding Value Milk Composition 55 63 9 06/20/23 20230601 NES 230601 Implications Genetic selection to increase milk yield has been very successful. Milk production of domesticated dairy cows can reach 30-50 L per day or 6,000 to 12,000 Lover a lactation compared to 8-10 L per day and <1,000 L over lactation in feral cows ([85]). Milk production in cows follow a dynamic curve starting with an initial rapid increase in milk yield in early lactation (approx. 0-45 days-in-milk, [DIM]), followed by a peak (approx. 46-55 DIM), and then a slow decline in milk yield during late lactation (approx. 56-340 DIM) ([76]). Flow of data between different components of a national milk recording system, including DNA and test-day milk samples collected on farms, milk composition information produced by milk testing laboratories, standardized records computed by dairy records processing centers, and breeding values calculated by the genetic evaluation center. [Extracted from the article]

Abstract: Our objective was to detect single nucleotide polymorphisms (SNPs) associated with resistance to the salmon louse in the Saint John River aquacultural population of North American Atlantic salmon using estimated breeding values (EBVs) and 6K genotypes from the parent‐generation and lice count phenotypes from the challenged, but ungenotyped, offspring‐generation. In 2011 and 2012, we challenged recent smolts with approximately 100 copepodids each. Fish were euthanized once the lice reached the chalimus stages and lice count, sex, tank and salt water weight were recorded. We used a multiple trait model to estimate breeding values for the parent‐generation using their own fresh water weights and the salt water weights and lice counts of the offspring‐generation. Salmon lice count heritability for untransformed and transformed data was 0.17 and 0.29 respectively. Two different genome‐wide association study methods were compared: (i) forward multiple linear regression and (ii) a mixed linear model using principal components to correct for population stratification as implemented in the egscore function of GenABEL. The two methods detected different SNPs located on different chromosomes. The multiple regression method incorporated 70 SNPs found on chromosomes 2, 7, 9, 12, 14, 15, 21, 22, 1p/23, 24. Many SNPs entered into the forward multiple regression are likely to be false positives from not correcting for the observed population stratification and cryptic relatedness. In contrast, the mixed linear model identified only two SNPs, one on chromosome 1p/23 (6.9%) and one on chromosome 1q (6.1%) consistent with louse‐resistance being a quantitative trait. [ABSTRACT FROM AUTHOR]

The Canadian dairy industry implemented genomic selection in 2009 to improve breeding in Holstein cattle and has been applied to several other dairy cattle breeds since then. Genomic selection is an effective breeding tool that can increase the accuracy of prediction and help to select young animals using genotypic information. As well as shortening generation intervals, genomic selection has also increased the genetic gain per generation and the profitability of the industry. However, genomic selection tends to increase inbreeding, reduce the effective population size and cause a loss in genetic variation. These consequences could lead to future challenges like lower selection response. To evaluate the sustainability of current breeding practices, investigation is warranted to observe the effects of genomic selection. Therefore, the objective of this study is to compare the population structure of Canadian Holstein cattle before and after the implementation of genomic selection in 2009. Using pedigree information to identify the number of sires used for breeding at three different time points (2000, 2010 and 2020), the number of daughters per sire, and length of time sires were used were investigated. Results show that the average number of offspring per top sire (top 10%) has decreased by 50%, however the average relatedness of available sires has increased considerably. This information will add to our knowledge of the effects genomic selection has had on the Canadian dairy industry and will inform future recommendations for sustainable breeding strategies that facilitate continual genetic progress. [ABSTRACT FROM AUTHOR]

Animal breeders have exploited many technological advances for increasing genetic gain in economically and functionally important traits. The implementation of such technologies in routine breeding programs has permitted genetic gains in traditional milk, meat and egg production traits as well as, more recently, in low-heritability traits like health, fertility, and even behavior. As global demand for animal products increases, animal breeders must ensure the technologies, methods and strategies employed are sustainable, to consider the many emerging technologies that are currently being investigated in various fields, and to ensure a social license to continue producing animal products. Here we discuss the societal, ethical, environmental, and economical aspects of sustainability in the context of livestock breeding. We review a number of technologies that have helped shape livestock breeding programs in the past and present, along with those potentially forthcoming. These tools have materialized in the areas of reproduction, genotyping and sequencing, genetic modification, epigenetics, and other areas of "omics" technologies. Although many of these technologies bring encouraging opportunities for genetic improvement of livestock populations, their applications and benefits need to be weighed with their impacts on sustainability. [ABSTRACT FROM AUTHOR]