Interacción genotipo ambiente en estrés térmico y producción de leche en vacas holstein en la región de Lima, Perú

A total of 352596 results of the test day milk controls (TD), as well as the climatic variables of Temperature and Relative Humidity combined in an index known as ITH, carried out in 5 stables in the Lima region, between January 2006 and December 2018, were available for this study. This database was represented by the TD of 11876 Holstein daughters of 8439 dams and 321 sires and was studied by different random regression models with the objective to estimating the genetic relationships between TD and ITH as an indicator of heat stress (HS). The results indicated that heritability (h2 ), along the ITH scale shows a slightly upward trend (h2 = 0.113±0.01 to 0.187±0.02) until reaching its highest values in the so-called thermal stress zone (ITH>=68 to ITH=77). The genetic correlations (rg) were close to the unit between adjacent or very close ITH levels and decreased as the differences between the HS intensity measured by the ITH increased, reaching results between rg = 0.562±0.09 to 0.582±0.12 between the coldest area (ITH< = 61) and the hottest (ITH > = 71). The correlations between the estimated Breeding Value (BV) in both zones was 0.607 and only 262 of the top 600 animals selected were better in both zones. These responses indicate that the results of TD should not be considered as an expression of the same trait throughout the trajectory of ITH, in other words there is environmental genotype interaction. An index was made based on all the estimates of the BV throughout ITH that allowed to identify not only the existence of genetic variation in ST but also variations in the way animals responded to the different levels of ITH. Un total de 352596 resultados de los controles periódicos de producción (TD), así como así las variables climáticas de Temperatura y Humedad Relativa combinadas en un índice conocido como ITH, realizados en 5 establos de la región de Lima, entre enero del 2006 y diciembre del 2018, estuvieron disponibles para este estudio. Esta base de datos estaba representada los TD de 11876 vacas Holstein hijas de 8439 madres y 321 sementales y fue estudiada por diferentes modelos de regresión aleatoria con el objetivo de estimar las relaciones genéticas entre TD y el ITH como indicador de estrés térmico (ST). Los resultados indicaron que la heredabilidad (h2 ), a lo largo de la escala de ITH manifiesta una tendencia ligeramente ascendente (h2 = 0,113±0,01 a 0,187±0,02) hasta alcanzar sus mayores valores en la denominada zona de estrés térmico