Differential Postprandial Eating Behavior of Morning and Evening Fed Dairy Cows

Abstract Text: The objective of this experiment was to establish postprandial patterns of eating rate in once-daily fed high-producing lactating dairy cows. Eight multiparous (664 ± 62 kg body weight; 80 ± 40 days in milk; mean ± SD) lactating Holstein cows were studied in a cross-over design experiment with two 21-d periods. Cows were kept under thermoneutral conditions and offered an experimental total mixed ration (TMR) based on barley and corn grains, corn silage, and alfalfa hay, as the main starch and forage sources, at either 0800 or 2000 h. The forage to concentrate ratio on a dry matter basis was 50:50, offering for 5-10% daily orts. Feed intake was monitored continuously for the entire experiment and collected for data analysis during the third week of both periods. Statistical data analysis was conducted with Mixed Models Procedures of SAS program. Feed intake patterns were expressed every 3-h as a percentage of total daily intake. Feeding the TMR at 2000 vs. 0800 h increased eating rate shortly post-feeding (P<0.05), such that morning-fed and evening-fed cows consumed 33% and 45% of their daily TMR intake within the first 3-h post-feeding. However, within 9-h post-feeding, morning-fed (72%) and evening-fed (74%) cows ate comparable amount of their total daily intake (P>0.15). Based on individual data, some cows in the evening-fed group consumed up to 70% of their total daily intake within only 3-h post-feeding. Total daily intake, however, was similar between morning-fed (21.2 kg) and evening-fed (21.4 kg) cows (P>0.15). These results demonstrated that timing of feeding as an external modulator of circadian ruminant physiology contributes significantly to rhythmic regulation of feed intake patterns. Findings provide implications for effective farm management of high-producing cows exposed to various metabolic challenges.

Keywords: Timing of feeding, Intake pattern, Dairy cow