Has yield plasticity already been exploited by soybean breeding programmes in Argentina?

This study focuses on the impact of genetic improvement of seed yield plasticity in soybean (Glycine max L.) in high-yielding environments (between 4000 kg ha-1 and 7000 kg ha-1) of Central Argentina. The association between seed yield and its plasticity was analysed with (i) a historical collection of 148 genotypes released to the market between 1980 and 2013 and (ii) 165 currently available commercial genotypes. The impact on seed yield of soybean breeding programmes in Argentina reveals higher genetic progress of the lowest (1.7% year-1) rather than the highest yielding genotypes (0.9% year-1). At the same time, seed yield plasticity has been exploited indirectly. Increased seed yield plasticity over time contributed to a reduction in genotypic seed yield variability (P<0.0001). Seed yield plasticity was related to seed yield in high-yielding environments (>5500 kg ha-1). Plastic genotypes showed a positive correlation with the length of the seed-filling period (r=0.5), suggesting that a longer seed-filling period could be required to maximize seed yield plasticity under high-yielding environments. To increase productivity, clarifying the value of plasticity will aid genotype selection for target environments, as well as the development of high-yielding cultivars specifically adapted to high-yielding conditions.

Parámetros Genéticos y no Genéticos para Caracteres de Crecimiento en un Rebaño Brahman Registrado / Genetic and Non-genetic Parameters for Growth Traits in a Registered Brahman Herd

Se realizó un estudio genético cuantitativo para determinar el peso al nacer (PN), peso al destete corregido a 205 d (P205) y peso a los 18 meses corregido a 548 d (P548) en un rebaño Brahman ubicado en el estado Cojedes, Venezuela, bajo un programa genético y ambiental supervisado. Se analizaron los registros de 5137 animales, nacidos durante los años 1996 a 2007. Se estimaron los componentes de (co)variancias, parámetros genéticos y no genéticos, a través de tres modelos animal univariados usando el paquete de programas MTDFREML. Todos los modelos incluyeron los efectos aleatorios: genético aditivo directo, genético aditivo materno y ambiental permanente de la madre y como efecto fijo: grupo de contemporáneos. Los valores de índices de herencia directos fueron 0,45, 0,20 y 0,34, y los índices de herencia maternos 0,02, 0,13 y 0,04 para PN, P205 y P548, respectivamente. Las correlaciones genéticas aditivas directas - maternas fueron positivas. Los estimados para las tendencias fenotípicas anuales fueron de 0,285 kg para PN, 2,045 kg para P205 y 0,503 kg para P548. Las tendencias genéticas anuales aditivas directas fueron 0,075 kg, 0,523 kg y 1,072 kg y las genéticas maternas fueron 0,0002 kg, 0,230 kg y 0,096 kg para PN, P205 y P548, respectivamente. Los resultados indican que existe suficiente variabilidad genética para crecimiento en la población evaluada, lo que favorece el programa de selección por crecimiento.

A quantitative genetic study for birth weight (BW), weaning weight corrected at 205 days (WW205), and weight at 18 months corrected at 548 days (W548), was conducted in a Brahman herd located in the State of Cojedes, Venezuela, under a supervised genetic and environmental program. The records of 5137 animals born from 1996-2007 were analyzed. Components of covariance, genetic and non-genetic parameters were estimated through three univariate animal models, using the MTDFREML set of programs. All models included random effects, such as direct genetic additive, maternal genetic additive, and permanent environmental of the dam; and as a fixed effect, the contemporary group. The direct heritability indexes were 0.45, 0.20, and 0.34; and the maternal heritability indexes were 0.02, 0.13 and 0.04 for BW, WW205 and W548, respectively. All genetic additive direct-maternal correlations were positive. The estimates for the annual phenotypic trends were 0.285 for BW, 2.045 for WW205, and 0.503 for W548; respectively. The direct additive annual trends were 0.075 kg, 0.523 kg, and 1.072 kg for BW, WW205, and W548, respectively. The results of the investigation indicate the existence of enough genetic variability for growth in the evaluated population, which favors the selection program for growth.

Relationship among blood indicators of lipomobilization and hepatic function during early lactation in high-yielding dairy cows.

Blood indicators are used as a tool to diagnose metabolic disorders. The present work was conducted to study the relationships among blood indicators of lipomobilization and hepatic function in high-yielding dairy cows. Two groups of Holstein cows were studied: 27 early lactation cows and 14 mid lactation cows from four different herds with similar husbandry characteristics in Galicia, Spain. Blood samples were obtained to measure beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), and the activity of aspartate transaminase (AST) and gamma-glutamyl transferase. Cows in early lactation had higher levels of BHB and NEFA than mid lactation cows. High lipomobilization (NEFA > 400 µmol/L) was detected in 67% and 7% of early lactation and mid lactation cows, respectively, while subclinical ketosis (BHB > 1.2 mmol/L) was detected in 41% and 28% of the early lactation and lactation cows, respectively. TG concentrations were low in all cows suffering subclinical ketosis and in 61% of the cows with high lipomobilization. During early lactation, 30% of cows suffered hepatic lipidosis as detected by levels of AST. Compromised hepatic function was observed in early lactation cows as shown by lower concentrations of glucose, total protein, and urea.