Midwest 2019 Ruminant Nutrition: General
Monday, March 11th, 2019
By: Mareah Volk
Dr. Napoleon Vargas Jurado- Modeling repeated measurements of diet composition
Dr. Napoleon Vargas Jurado began his discussion by describing the importance of measuring feed intake in livestock production so that feed efficiency can be determined. Measuring feed intake can be quite difficult in grazing systems as the animal grazes throughout the day. The amount each animal consumes on pasture cannot be physically weighed the same way that diets fed in a bunk can be weighed. In grazing systems, plant-wax markers can be measured to estimate feed intake. In order to do this, an estimation of the diet composition is need. Plant-wax markers are located on the outer surface of the plant but the composition can vary from plant species.
The focus on Dr. Napoleon Vargas Jurado’s research was to develop a model that accounts for covariance among repeated measures and related animal backgrounds and genetics. In this experiment, he used four plant markers with two different species of forage (red clover and tall fescue). The plant-wax markers and the fecal samples from the cattle in this experiment were analyzed using gas chromatography. The reliability of the estimated feed intake was not improved when analyzed as a repeated measure. Although, including a relationship matrix did increase accuracy of the estimated diet composition. In this experiment, simple diets were used so extrapolation to more complex diets should be avoided at this time. At the end of his presentation, Dr. Napoleon Vargas Jurado shared that this data was within five to ten percent of the actual feed intake from the heifers used in this experiment.
Devin Broadhead- Economic Comparison of March and May Calving Systems in the Nebraska Sandhillls
Devin Broadhead concluded the Ruminant Nutrition General session by presenting his data comparing the economics of two different calving systems used in the Nebraska Sandhills. Profitability in cow-calf systems are determined as a measure of net return from the calves at weaning. When deciding between a March calving system and a May calving system, factors such as labor and weather can greatly impact the decision. In this analysis, a three year period was used for data collection and the economic impacts were based off of nine years of prices. Several factors were included in this model, such as labor, the cost of cull and replacement animals, and feed costs of these systems. Total calf costs, total pair feed costs, and the net average market return at weaning were the outputs utilized in the economic model.
In both the March and May systems, pregnancy rate was similar, however, adjusted calf weaning weight was greater for calves born in the March system compared to calves born in the May system. Over the nine years of economic data, the March system had greater feed costs as forage quality and availability was not matched with the requirements of the cows. In the March system, the need for replacement animals was reduced. The May system had greater cost for replacement animals but overall had lower feed costs. Additionally, in the May system, the market value was lower for the weaned calves. Overall, the March system was more profitable compared to the May system, however Devin Broadhead noted that this analysis only included two different treatments in each system. More research could potentially look at supplementation types and levels in these different calving systems to determine ways to maximize profitability between these systems.