Modifying the NRC weight gain model to estimate daily gain for stockers grazing bermudagrass in the southern United States

The energy requirements, feed intake, and performance of grazing animals vary daily due to changes in weather conditions, forage nutritive values, and plant and animal maturity throughout the grazing season. Hence, realistic simulations of daily animal performance can be made only by the models that can address these changes. Given the dearth of simple, user-friendly models of this kind, especially for pastures, we developed a daily gain model for large-frame stockers grazing bermudagrass [Cynodon dactylon (L.) Pers.], a widely-used warm-season perennial grass in the southern United States. For model development, we first assembled some of the classic works in forage-beef modeling in the last 50 years into the National Research Council (NRC, 1984) weight gain model. Then, we tested it using the average daily gain (ADG) data obtained from several locations in the southern United States. The evaluation results showed that the performance of the NRC model was poor as it consistently underpredicted ADG throughout the grazing season. To improve the predictive accuracy of the NRC model to make it perform under bermudagrass grazing conditions, we made an adjustment on the model by adding the daily departures of the modeled values from the data trendline. Subsequently, we tested the revised model against an independent set of ADG data obtained from eight research locations in the region involving about 4,800 animals, using 30 years (1991-2020) of daily weather data. The values of the various measures of fit used, namely the Willmott index of 0.92, the modeling efficiency of 0.75, the R 2 of 0.76, the root mean square error of 0.13 kg d -1, and the prediction error relative to the mean observed data of 24% demonstrated that the revised model mimicked the pattern of observed ADG data satisfactorily. Unlike the original model, the revised model predicted more closely the ADG value throughout the grazing season. The revised model may be useful to accurately reflect the impacts of daily weather conditions, forage nutritive values, seasonality, and plant and animal maturity on animal performance.

Parenting Behavior and Adolescent Affect: Bidirectionality and the Role of Gender

Parents play an important role in adolescent mental health. Yet, research is inconclusive regarding the influence of adolescent affect on parenting behavior. This study examined the bidirectionality between five parenting behaviors and adolescent depressive symptoms—conceptualized by the tripartite model as low positive affect and high negative affect—while investigating gender differences. Adolescents ( N = 193) from a Southern United States high school reported their parent’s parenting behavior and their affect twice over a year. Linear regression results revealed relations between parenting behaviors and adolescent affect in both directions. However, when examining the relation between specific parenting behaviors (e.g., involvement) and adolescent affect (e.g., negative affect), results showed unidirectional effects only. Furthermore, significant gender differences emerged. These findings underline the importance of considering the relation between parenting behavior and adolescent affect as bidirectional and with differential associations depending on the parenting behavior and adolescent affect and gender.

[IN1341] Stem Borers (Lepidoptera: Crambidae) in Florida Rice

Three stem borers, the sugarcane borer, Diatraea saccharalis (F.), rice stalk borer, Chilo plejadellus Zincken, and Mexican rice borer, Eoreuma loftini (Dyar), infest rice in the southern United States. They occur in Florida, with the Mexican rice borer being an invasive species recently introduced into the state. This publication briefly describes stem borers and sampling methods and reports results of the first extensive survey conducted to measure their occurrence in Florida rice.