Effects of changes in diet energy density and milking frequency and a single injection of cabergoline at dry-off on feeding behavior and rumination time in dairy cows

Effects of feed energy density, daily milking frequency, and a single injection of cabergoline on behavior and welfare in dairy cows at dry-off

Drying off dairy cows may challenge animal welfare due to high milk yields. A total of 111 loose-housed Holstein cows yielding >15 kg/d of milk were included in a 2 × 2 × 2 factorial design during dry-off to investigate the effects of reduced feeding level (normal vs. reduced energy density), reduced milking frequency (twice vs. once daily), and administration of a dopamine agonist (saline i.m. injection vs. cabergoline i.m. injection) on behavior in the home pen. During the 7 d before dry-off, cows were fed and milked according to 1 of the 4 feeding level and milking frequency combinations. Within 3 h after the last milking, cows were injected i.m. with 5 mL of either saline or a dopamine agonist (5.6 mg of cabergoline; Velactis, Ceva Santé Animale, Libourne, France; labeled for use only with abrupt dry-off, i.e., no preceding reduction in feeding level or milking frequency before last milking). Cows' behavior during d -1, 0, and +1 relative to the last milking was recorded via video and leg-attached sensors. Cows on the reduced energy density diet spent more time feeding and showed more attempts to feed from other cows' bins on d -1. Throughout the period of observations, cows on the reduced diet spent a lower percentage of lying time with their head raised, a higher percentage of lying time with their legs bent, and less time standing in a vigilant posture than did cows on the normal lactation diet. Reducing the daily milking frequency from 2 to 1 did not result in any clear behavioral signs of discomfort. On d 0, cows injected with cabergoline lay down longer but had their head raised for a shorter percentage of time while lying, compared with cows injected with saline. Cows injected with cabergoline also spent less time feeding than cows injected with saline on d 0, and reduced the time spent drinking from d -1 to d 0. Finally, fewer cabergoline-injected cows used the brush for self-grooming, and, among cows that did use the brush, the cows injected with cabergoline reduced the time spent using the brush from d -1 to d 0. In conclusion, cows injected with cabergoline showed several behavioral changes compared with control cows injected with saline. The behavioral changes shown by cows injected with cabergoline may be indicative of malaise during the first 24 h after injection, raising concern for animal welfare. No behavioral evidence for reduced udder pain in cows injected with cabergoline compared with control cows injected with saline was found. Drying off by reducing the energy density of the diet caused behavioral changes indicative of hunger before dry-off, whereas reducing the milking frequency had no clear effects on behavior.

Effects of feeding level, milking frequency, and single injection of cabergoline on blood metabolites, hormones, and minerals around dry-off in dairy cows

This study aimed to investigate the effect of the different dry-off strategies based on reducing feeding level (normal vs. reduced energy density), reducing milking frequency (twice vs. once daily), and administration of a dopamine agonist after last milking (i.e. saline vs. cabergoline injection) on blood metabolites, hormones, and minerals around dry-off. In this experiment, 119 Holstein dairy cows were used in a 2 × 2 × 2 factorial arrangement. In the last week before dry-off, cows were allocated to 1 of the 4 possible dry-off strategies based on feeding level and milking frequency. Within 3 h after last milking, cows were injected with either saline or a D₂ dopamine agonist (cabergoline; Velactis, Ceva Santé Animale, Libourne, France; labeled for use only with abrupt dry-off, e.g., no preceding reduction in feeding level or milking frequency before last milking). After dry-off, all cows were fed the same dry cow diet and data collection continued for a week. Blood samples were collected from the coccygeal vein on d -9, -6, -5, -2, 1, 2, 5, and 7 relative to dry-off. Additionally, blood was sampled at 0, 3, and 6 h relative to injection of either cabergoline or saline, equivalent to d 0.125, 0.250, and 0.375 relative to last milking (dry-off). The reduced feeding level before dry-off caused reduced glucose and insulin concentrations as well as increased free fatty acid concentrations, particularly when reduced feeding level was combined with milking the cows 2× daily. The intramuscular injection of cabergoline caused the expected reduction in circulating prolactin concentrations. In addition, dopamine-agonist cabergoline induced an atypical simultaneous pattern of plasma metabolites (i.e., increased glucose and free fatty acid concentrations), hormones (i.e., reduced insulin and increased cortisol concentrations), and minerals (i.e., reduced calcium concentration), indicating that normal metabolic and mineral homeostatic regulations were hindered after the injection of ergot alkaloid cabergoline. In conclusion, reducing milking frequency seems the best management strategy to reduce milk production at dry-off among those tested in this study.

Effects of feeding level and milking frequency on behavior of dairy cows before dry-off

Drying-off may challenge the welfare of especially high-yielding dairy cows. In this study, 119 loose-housed Holstein cows yielding ≥20 kg milk/d were enrolled in a 2 × 2 factorial design aiming to investigate effects of changes in diet energy density and daily milking frequency on behavior. The last 7 d before the dry-off day, cows were milked either twice or once daily, and were fed either a lactation diet or the same diet diluted with 30% barley straw, both offered in individual bins for ad libitum intake. All cows were fitted with sensors to record lying time and activity, and data from 109 of these cows were used together with behavioral observations obtained from video recordings of 52 of the cows. Data from activity sensors and video recordings were obtained during 24 h on d -6, -3, and -1 relative to the dry-off day (i.e., the day of the last milking). Across all days of observation, cows milked once daily spent more time feeding (149 vs. 130 min/d) than cows milked twice daily. Cows on the reduced diet and milked twice daily had a shorter lying time compared with cows on the normal diet and milked twice (759 vs. 837 min/d), whereas lying times of cows on the remaining 2 treatments were intermediate. Among cows on the lactation diet, reduced milking frequency increased time spent perching (from 11.1 to 28.7 min/d). Cows fed the energy-reduced diet spent more time feeding (154 vs. 124 min/d), showed more attempts to feed from unassigned feed bins (31.7 vs. 15.4 attempts daily), and spent less time using a mechanical brush (6.5 vs. 9.2 min/d) than cows fed the lactation diet. These results show that several aspects of cows' behavior, including main activities such as lying and feeding, but also behaviors of low resilience such as brush use, and to some extent more subtle and complex behaviors such as perching and attempts to feed from unassigned feed bins, are sensitive to management changes typically applied during the days before dry-off. The behavioral effects of the reduced feed energy level support earlier findings suggesting that qualitative feed restriction renders cows hungry. The effects of the reduced milking frequency on behavior were generally less pronounced, but 2 noteworthy interactions between milking frequency and diet were seen. First, cows milked twice daily and fed the energy-reduced diet spent less time lying, which is possibly related to increased energy demand and hunger. Second, cows milked once daily and fed the lactation diet spent more time perching, which may be related to udder discomfort. However, these more complex findings warrant further study. Taken together, the results of this study show that a dry-off procedure involving reduced energy supply induces behavioral changes indicating a higher degree of compromised welfare compared with reduced milking frequency.