JDS communications最新文献

Sleep serves several essential functions in all mammals including dairy cattle. Researchers are beginning to estimate sleep in dairy cattle using a combination of physiological measurements (e.g., polysomnography) as well as changes in behavior (e.g., different resting postures). Sleep may provide unique insight into how cows and calves respond to, and cope with, their environments, as a complement to other common measurements such as lying time. Although each of the methods to assess sleep in cattle has its advantages, there remain several challenges with each approach. The objective of this narrative mini-review is to describe current methods for estimating sleep in dairy cattle, including some of the advantages and limitations with each method. We will start with describing the research to date on adult cows, followed by preweaning dairy calves. We end the review with recommendations for researchers interested in assessing sleep in dairy cattle and ideas for future areas of research.

Controlled studies have shown that heat stress abatement positively influences health, productivity, behavior, and reproductive performance of dairy cows during all stages of the lactation cycle. Based on previous findings, the present study focused on a better understanding of how seasonal changes affect the behavior of multiparous lactating dairy cows kept in typical free-stall housing with the objective to aid in the management of lactating cows exposed to variable environmental conditions. Automated monitoring devices (Nedap, the Netherlands) were used to assess behavioral activity of mature Holstein dairy cows during the “hot season” (HS; n = 19; July, August, and September) and the “cool season” (CS; n = 15; December, January, and February) under normal management conditions. Cows received a leg tag to measure daily lying time, and number of steps and standing bouts, and a neck tag to measure eating and rumination time. All cows were housed in sand-bedded freestall barns equipped with cooling systems (soakers and fans). Behavior, milk production and milk components were recorded for the first 9 wk of lactation after calving. Average temperature-humidity index (THI) was 78.2 ± 0.4 (± standard error) in the HS and 54.4 ± 0.2 in the CS. Fat-corrected milk yield was greater in the CS compared with HS during the first 5 wk of lactation. Milk protein percentage was lower in CS during the first 2 wk of lactation. In contrast with HS, milk fat percentage was greater in the CS. Compared with CS, overall, during HS cows spent less time eating, lying down, and tended to spend less time ruminating. In addition, exposure to high THI resulted in increases in standing bouts, and overall standing time in HS relative to CS. No differences in number of steps were observed between HS and CS. In summary, exposure to high THI during lactation seems to negatively affect the behavior and consequently the daily time budget of lactating Holstein cows, even under housing conditions with active cooling. A better understanding on how different seasons affect the daily time budget of lactating dairy cows may contribute to the development of more effective management strategies to decrease the negative effects of heat exposure.

When calves are reared by cows, separation can be stressful, and it is often advised to use gradual weaning to minimize this stress. In foster cow systems, one gradual weaning method is to remove the foster cows, one by one, from the cow-calf group. The response to one-by-one removal of foster cows of 32 calves housed in 5 groups was studied. Calves were fostered to a designated foster cow individually, in pairs, or in trios, at the age of 1 to 2 wk and then housed in groups of 4 to 6 foster cows and 6 to 11 calves until gradual weaning started at 3 mo of age. Calf behavior and aggression received by calves from cows were recorded using video during 18 h before any foster cow was removed, as well as 18 h before and 18 h after the designated foster cow was removed from the group. Before any foster cow was removed, the calves spent a similar amount of time sucking the designated foster cow and other cows (in total 43 ± 5 min/18 h). The total duration of sucking was similar before and after the designated foster was removed, as the duration of sucking other cows increased. The number of aggressive events received from other cows also increased. The results indicate that milk availability for the group of calves decreases as foster cows are gradually removed and that the older and heavier calves increasingly compete with the younger and lighter calves for the available milk. This weaning method may also compromise the welfare of the foster cows that are left to wean off an increasing number of calves, and this warrants further research.

Dairy calf social development and responses to novelty are influenced by social contact, but longer-term implications of early life social housing for response to novelty in weaned calves are less clear. The objective of this study was to evaluate the effects of preweaning social housing on how dairy calves respond to novel feed and objects a few days following weaning and grouping. At birth, calves were alternately assigned to either individual (IH; n = 22 calves) or pair housing (PH; n = 18 pairs; 1 focal calf enrolled/pair). Following weaning (at 53.4 ± 2.0 d; mean ± standard deviation), calves were mingled between treatments and group-housed with calves born the same week (4 to 6 calves/pen; 12 total groups). Beginning at 56.4 ± 2 d of age, calves were exposed to 2 novel feed tests (sliced carrots and chopped red apples) conducted in the home pen on consecutive days. Following novel feed tests, a subset of calves (n = 11 IH and n = 9 PH calves, from separate paired pens) was exposed to a novel object test, conducted individually in a testing arena. During novel feed tests, the latency to contact the novel feed did not differ between treatments but previously IH calves spent more time at the feed trough (6.9 vs. 4.3 min/h, IH vs. PH, standard error = 0.25). In the novel object test, latency to contact the novel object and duration of contact did not differ between previous housing treatments but previously IH calves moved around the arena more. These results suggest that preweaning social housing had some carryover effects on behavioral responses during novel feed and novel object tests a few days following weaning and grouping, potentially reflecting differences in social feeding behavior and activity in a novel space, but avoidance of the novel object and feed were not affected.

To explore the effect of lactation stage and parity on the milking order of cows, we collected milking order data of all lactating cows (n = 251) over a period of 12 wk in one commercial Swedish dairy cow herd using a herringbone milking parlor. Cows were kept in 2 housing groups (G1 and G2) and moved from G1 to G2 at approximately mid lactation. Two analyses were conducted to investigate if lactation stage (early: 2–49 d in milk, mid: 50–179 d in milk, and late ≥180 d in milk) and parity are associated with the entrance order to the parlor or a preference of entering a new milking line first. In G1 and G2, cows in first parity entered the milking parlor earlier than cows in higher parities. In addition, in G1 cows in early lactation entered the milking parlor earlier than cows in later lactation. Similar effects were observed for the preference of entering a new milking line first. No effect of mid versus late lactation could be observed in either G1 or G2. The study also found that cows tend to keep their rank within the milking order constant. The results of the study indicate that cows of presumably lower hierarchy (first parity and early lactation) leave the waiting area earlier compared with other cows. This should be considered when planning grouping strategies and preventive measures against mastitis pathogen transmission.