Feedbunk sorting characteristics by dairy heifers offered total mixed rations diluted with low-energy forages

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin

Submitted to: Popular Publication
Publication Type: Popular Publication
Publication Acceptance Date: 8/1/2018
Publication Date: 8/10/2018
Citation: Coblentz, W.K., Akins, M.S. 2018. Feedbunk sorting characteristics by dairy heifers offered total mixed rations diluted with low-energy forages. Popular Publication. pp. 14-16.

Interpretive Summary:

Technical Abstract: Use of corn silage in the diets of pregnant dairy heifers offered for ad libitum intake can be problematic, primarily because corn silage exceeds the energy requirement for this class of livestock. Furthermore, the concentration of structural plant fiber (NDF) is too low, and does not serve the co-equally important function of limiting voluntary intake through the normal process of gut fill. One remedy for this problem is to dilute total mixed rations (TMR) with low-energy forages that increase the NDF concentration within the diet, but also reduce energy density (TDN) and voluntary intake. While this approach is effective in controlling weight gains, inclusion of low-energy forages can result in aggressive efforts by heifers to sort and discriminate against these often less-desirable forages. Potentially, this can be a problem if small or passive animals can’t reach the feedbunk until after substantial sorting has occurred. Two studies conducted recently by USDA-ARS and University of Wisconsin scientists at the Marshfield Agricultural Research Station have evaluated the sorting behaviors exhibited by pregnant dairy heifers offered a TMR comprised of corn silage and alfalfa haylage, but diluted with a variety of low-energy forages. Heifers will discriminate against some low-energy forages, such as chopped wheat straw and corn fodder. Sorting can be most severe against long or poorly processed feed particles, thereby causing a declining trend in energy density for feed remaining in the bunk throughout the day. While this has the potential to affect heifer growth performance, this has not been observed in our studies, most likely because feed is disbursed daily, and fed to minimal (< 3%) refusals. The feeding approach used for these trials requires a higher standard of management, and it should not be inferred from these results that sorting behaviors or other compromised forms of animal care do not affect heifer growth performance.