Abstract
The objective of this study was to determine the association between the proportion of particles greater than 19 mm in a total mixed ration fed to dairy cattle and their fecal score. Over a 22 day period, random feed samples were collected twice a day from a one-side barn and assessed for particle size using the Pennsylvania State Particle Separator. In addition, at each feeding sampling, the same barn was inspected and fresh feces were scored on a four point scale. Multiple regression models were developed to associate the proportion of particles >19 mm with fecal scores at one, two and three days after that specific particle evaluation. Results of this observational study showed a significant relationship between particle size and fecal scores two days later. The results demonstrated a cubic polynomial effect: Fecal scores improved with increasing of the proportion of particle size >19 mm at a low proportion of large particles, then it was maintained constant at intermediate proportion (10-15%) of large particles and finally increased again with a high proportion (up to 17%) of particle >19 mm.
Highlights
Fiber is not very well defined as a nutrient requirement for dairy cattle
While the NRC (2001) recommends minimum values for Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF), there is no recommendations for type of fiber and particle size or physically effective NDF
The objective of this study was to evaluate the association between the proportion of particle size >19 mm in a lactating dairy cattle Total Mixed Ratio (TMR) and a proposed fecal score from cows eating that particular diet under commercial settings in a Florida dairy farm, USA, during a period of one month
Summary
Fiber is not very well defined as a nutrient requirement for dairy cattle. While the NRC (2001) recommends minimum values for Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF), there is no recommendations for type of fiber (e.g. forage NDF) and particle size or physically effective NDF (peNDF). No less than 28% of a Total Mixed Ratio (TMR) should be in the form of NDF This is further confounded by the source of NDF; the minimum total NDF required increases as the proportion of the NDF provided by forage decreases (NRC, 2001). For this reason, a diet that seems to provide adequate NDF may be deficient if long particles are lacking (Grant, 1997; Suarez-Mena et al, 2013). Finding an optimal balance between physically effective fiber and readily degradable carbohydrates in the diet is difficult but crucial for maintaining proper rumen metabolism, and for maintaining a stable metabolic health status and enhancing the productivity of dairy cattle (Zebeli et al, 2012)
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