Feeding amount affects the sorting behavior of lactating dairy cows

Abstract

The objective of this study was to determine whether feed sorting behavior in dairy cattle is influenced by the amount of feed provided. Six lactating Holstein cows, individually fed a total mixed ration once daily, were exposed to two treatments in a crossover design with 7-d periods. The treatments were: (1) lower feed amount (LFA; target 10% orts), and (2) higher feed amount (HFA; target 20% orts). Dry matter intake (DMI) was monitored daily for each animal. On the final 4 d of each treatment period, fresh feed and orts were sampled for particle size analysis. The particle size separator had three screens (19, 8, 1.18 mm) and a bottom pan, resulting in four fractions (long, medium, short, fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Actual orts percentage averaged 11.5% for the LFA and 18.0% for the HFA treatments. When on the HFA cows sorted for the medium particles to a greater extent than on the LFA (103.0 vs. 101.1%). Further, when on the HFA treatment cows sorted against short particles to a greater extent than on the LFA (95.2 vs. 98.6%). Despite greater sorting on the HFA treatment, the concentrations of neutral detergent fiber (NDF; 29.6%) and starch (27.1%) in the feed consumed were similar between treatments. Given this, and that DMI was greater on the HFA treatment compared with the LFA treatment (29.7 vs. 26.5 kg d-1), greater intakes of NDF (8.7 vs. 7.8 kg d-1) and starch (8.0 vs. 7.2 kg d-1) were also observed on the HFA treatment. The results suggest that, despite causing greater feed sorting, increasing the feeding amount for lactating dairy cows promoted higher DMI and did not prevent the consumption of a ration balanced to meet their nutritional requirements.Key words: Feeding amount, sorting behavior, dairy cow