Short-term increases in stocking density did not alter feeding behavior of lactating Holstein dairy cattle

Abstract Text: Increasing stocking density at key resources may have negative effects on the feeding pattern of dairy cattle. The objective of this study was to determine the impact of short-term increases in stocking density on meal duration and frequency of lactating Holstein dairy cattle. Cows (n=136) were allocated to one of four groups (n = 34), balanced for parity, DIM, and milk production. Four stocking density treatments of 100 (one cow per freestall and headlock), 113, 131, and 142% were assigned using a 4x4 Latin Square, with treatments imposed for 14-d periods. Twelve cows from each pen were selected to form focal groups, balanced by milk production (50.2 ± 1.1 kg), parity (2.2 ±0.2), DIM (162.2 ± 7.0 d), BW (700.1 ± 11.0 kg), and BCS (3.09 ± 0.05). On day 11 of each period, feeding behavior was recorded at 10-min intervals for 24 h. Meals were defined as repeated observations of eating with a maximum 20 min of not eating between observations. To evaluated diurnal effects, the 24-h of data was divided into BLOCK1 (0400 – 1200), BLOCK2 (1200 – 2000), and BLOCK3 (2000 – 0400) based on milking time. The MIXED procedure of SAS (SAS 9.3, SAS Inst., Cary, NC) was used to determine the effect of stocking density on meals per day, meals per hour, meal duration, time between meals, and meal duration 2 h before and after milking.  Stocking density did not affect the number of meals per day (P = 0.25), time between meals (P = 0.93), number of meals per hour (P = 0.71), or meal duration (P = 0.33).  However, meals were longer during BLOCK1 (38.8 ± 1.2 min) and BLOCK2 (39.7 ± 1.2 min) compared to BLOCK3 (33.8 ± 1.3 min; P < 0.01). Feed delivery occurred daily at 0430 h, with feed pushed up throughout the day. This suggests meal length decreases relative to time of feed delivery. However, meal duration increased after milking compared to before milking (29.5 ± 1.0 vs. 21.0 ± 1.0 min, respectively; P < 0.01), regardless of stocking density (P = 0.98). Short-term increases in stocking density did not impact the feeding pattern of lactating dairy cows. Future studies should investigate ways cattle compensate for increased stocking density while avoiding changes in feeding pattern.

Keywords: dairy cattle, stocking density, feeding behavior