Growth performance and sorting characteristics of corn silage-alfalfa haylage diets with or without forage dilution offered to replacement Holstein dairy heifers

Authors: Coblentz, Wayne; ESSER, NANCY - University Of Wisconsin; HOFFMAN, PATRICK - University Of Wisconsin; AKINS, MATTHEW - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2015
Publication Date: 10/15/2015
Publication URL: http://handle.nal.usda.gov/10113/61621
Citation: Coblentz, W.K., Esser, N.M., Hoffman, P.C., Akins, M.S. 2015. Growth performance and sorting characteristics of corn silage-alfalfa haylage diets with or without forage dilution offered to replacement Holstein dairy heifers. Journal of Dairy Science. 98:8018-8034.

Interpretive Summary: Heifers consuming high-quality forage diets are susceptible to excessive weight gains and over-conditioning. One approach for controlling this problem is to dilute diets with low-energy forages, such as straw, that reduce the energy density of the diet, as well as voluntary dry matter intake by heifers. These diluting agents are often sortable by dairy heifers, which is potentially problematic with overcrowding, and may cause variable or erratic weight gains by heifers grouped in a common pen based on aggressive or passive behaviors. However, previous visual evidence has suggested that eastern gamagrass haylage may be a non-sortable alternative to straw. Four forage-based diets that included a negative control (alfalfa haylage/corn silage), as well as 3 diets diluted with low energy forages (eastern gamagrass haylage, chopped wheat straw, or chopped corn fodder) were offered for free-choice intake to Holstein heifers. All diluting agents were effective in reducing the energy density and dry matter intake from these diets. There was no sorting of physical effective fiber particles from the negative-control diet, nor was there sorting of the diet diluted with eastern gamagrass haylage. Sorting of physical effective fiber was detected for the straw diet, and sorting was much more severe for the chopped corn fodder diet. However, sorting behaviors could not be linked directly with the growth performance of heifers, and dilution with chopped straw was most effective in maintaining average daily weight gains within typical recommendations for Holstein heifers. This information is useful to dairy producers and nutritionists who are looking for alternative forages that don't cause excessive weight gain in growing heifers.

Technical Abstract: Gravid dairy heifers consuming high-quality forage diets are susceptible to excessive weight gains and over-conditioning. One approach for controlling this problem is to dilute diets with low-energy forages, such as straw, that reduce the caloric density and DMI of that diet by heifers. These diluting agents are often sortable by dairy heifers, but previous visual evidence has suggested that eastern gamagrass haylage may be a non-sortable alternative. Our objectives were: i) to compare the growth performance of dairy heifers offered a high-quality forage diet (CONTROL) with diets containing 1 of 3 diluting agents [eastern gamagrass haylage (EGG), chopped wheat straw (STRAW), or chopped corn fodder (FODDER)]; and ii) evaluate sorting behaviors of heifers offered these forage diets. Holstein heifers (n = 128) were stratified (32 heifers/block) on the basis of initial BW (heavy, 560 ± 27.7 kg; medium-heavy, 481 ± 17.7 kg; medium-light, 441 ± 22.0 kg; and light, 399 ± 14.4 kg), and then assigned to 1 of 16 identical research pens (4 pens/block; 8 heifers/pen), where each of the 4 research diets were assigned to 1 pen within each block. Diets were offered in a 118-d feeding trial with heifers crowded to 133% of capacity at the feed bunk. Inclusion of low-energy forages was effective in reducing DMI, as well as the energy density of the diet. Concentrations of physically effective fiber (pef) particles did not change during the 24-h period following feeding for either the CONTROL or EGG diets; however, this response for pef particles masked the competing (and cancelling) responses for individual large and medium particles, which heifers sorted with discrimination and preference, respectively. Sorting against pef particles was detected for STRAW, and much more severely for the FODDER diet. Sorting of forage particles by heifers could not be related to heifer performance. Compared to CONTROL (1.16 kg/d), ADG were reduced by dilution in all cases, but was virtually identical between EGG (0.98 kg/d) and FODDER (0.97 kg/d), which exhibited no sorting and extensive sorting of pef, respectively. Furthermore, ADG for STRAW was approximately 0.2 kg/d less than EGG or FODDER, despite exhibiting sorting characteristics intermediate between EGG and FODDER. Diets diluted with low-energy forages were formulated to be isonitrogenous and isocaloric; within that context, STRAW was most effective in reducing DMI and maintaining ADG within typical recommendations for Holstein heifers.