Importance of adaptation and genotype × environment interactions in tropical beef breeding systems

Abstract

This paper examines the relative importance of productive and adaptive traits in beef breeding systems based on Bos taurus and tropically adapted breeds across temperate and (sub)tropical environments. In the (sub)tropics, differences that exist between breeds in temperate environments are masked by the effects of environmental stressors. Hence in tropical environments, breeds are best categorised into breed types to compare their performance across environments. Because of the presence of environmental stressors, there are more sources of genetic variation in tropical breeding programmes. It is therefore necessary to examine the genetic basis of productive and adaptive traits for breeding programmes in those environments. This paper reviews the heritabilities and genetic relationships between economically important productive and adaptive traits relevant to (sub)tropical breeding programmes. It is concluded that it is possible to simultaneously genetically improve productive and adaptive traits in tropically adapted breeds of beef cattle grazed in tropical environments without serious detrimental consequences for either adaptation or production. However, breed-specific parameters are required for genetic evaluations. The paper also reviews the magnitude of genotype 3 environment (G 3 E) interactions impacting on production and adaptation of cattle, where 'genotype' is defined as breed (within a crossbreeding system), sire within breed (in a within-breed selection programme) or associations between economically important traits and single nucleotide polymorphisms (SNPs -within a marker-assisted selection programme). It is concluded that re-ranking of breeds across environments is best managed by the use of the breed type(s) best suited to the particular production environment. Re-ranking of sires across environments is apparent in poorly adapted breed types across extreme tropical and temperate environments or where breeding animals are selected in a temperate environment for use in the (sub)tropics. However, G 3 E interactions are unlikely to be of major importance in tropically adapted beef cattle grazed in either temperate or (sub)tropical environments, although sex 3 environment interactions may provide new opportunities for differentially selecting to simultaneously improve steer performance in benign environments and female performance in harsher environments. Early evidence suggests that re-ranking of SNPs occurs across temperate and tropical environments, although their magnitude is still to be confirmed in well-designed experiments. The major limitation to genetic improvement of beef cattle over the next decade is likely to be a deficiency of large numbers of accurately recorded phenotypes for most productive and adaptive traits and, in particular, for difficult-to-measure adaptive traits such as resistance to disease and environmental stressors.

Boosting the productivity and profitability of northern Australian beef enterprises: Exploring innovation options using simulation modelling and systems analysis

“…Growth rates are moderately heritable (Burrow, 2001(Burrow, , 2012 indicating that there is good opportunity to achieve reasonable production gains through genetic improvement. However, heritability relating to weight is higher than that relating to weight gain, and especially post-weaning (Davis, 1993).…”

Effect of Atmospheric Pressure on Semen Parameters in Bull Sires of Modern Selection on the Day of Collection

“…The adverse effects of environmental stress can occur at the genetic level. The precise identification of environmental factors affecting semen quality is important for improving bull reproductive function [4][5][6]. Morphofunctional abnormalities of the reproductive organs in cattle in a sharply continental climate reduce the reproductive capacity [7].…”

Characterization of lactation curves in Siboney cattle using nonlinear mixed models

“…In tropical systems, feeding is largely based on grazing of forage grasses, occasionally complemented by forage legumes (37) . Factors involved in the environment level include prevalence of internal and external parasites, stress caused by high temperatures and rainfall, and forage quality and availability (1,38) . In the present results, the Wood model had the best fit for characterizing the lactation curve in Siboney cattle at 240 d. The curve was one of continuous increase with a peak production of 7.71 kg at 40 d and a cumulative total production of 1,653 kg.…”

“…En el contexto del animal, la variabilidad en los niveles productivos se puede atribuir al genotipo, en función de la proporción de genes BI y BT que constituyen al individuo (35,36) ; en el contexto de tecnología, la producción de leche es afectada por la interacción del becerro con la vaca y por el manejo del amamantamiento de la cría (18) . La alimentación en los sistemas tropicales se fundamenta en pastoreo de gramíneas forrajeras, y en algunas ocasiones se complementa con leguminosas forrajeras (37) ; sin embargo, los efectos del ambiente se caracterizan por la prevalencia de parásitos internos y externos, temperaturas y niveles de humedad altos que repercuten en estrés del animal; así como en la calidad y disponibilidad del forraje (1,38) . En bovinos Siboney, el modelo de Wood fue el que mejor se ajustó para caracterizar la curva de lactancia a 240 días; presentando una curva continuamente incrementando, con una producción máxima de 7.71 kg a los 40 días, así como una producción total acumulada de 1,653 kg.…”