Tirne spent eating

Cows spent less time eating

(P

c 0.01) (Figure 2.2) under 16-8 conditions than under 8-0 conditions during 1000- 1200h and 1800-2000h observation periods. Proportions of tirne spent eating for the 1000- 1200h period were 0.16 ^k 0.03 for 16-8 cows, and 0.36

*

0.04 for 8-0 cows. In the 1800-2000h observation period, cows under 16-8 conditions averaged a proportion of 0.33 0.03, while cows under 8-0 conditions averaged a proportion of 0.46

*

0.03.

During the 2000-2200h and the 0000-0200h observation periods, 16-8 cows spent more time eating (P < 0.01) than while under 8-0 treatment. The proportion of time spent eating for experimental cows was 0.11

*

^{0.02, while} cows under control treatment averaged a proportion of 0.04

*

0.01 for this variable at the 2000-2200h observation period. For the 0000-0200h period, proportions of time spent eating were 0.21

*

0.02 and 0.08 0.02 in the same order as above.

2 . 4 2.3.5 T h e v e n t ruminating

Cows spent more time ruminating (Figure 2.3) (P -: 0.01) under 16-8 conditions than under 8-0 conditions during 1000- 1200h and 1800-2000h observation periods. In the 1000-1200h observation period, proportions of time spent ruminating in 16-8 cows were 0.32 0.04, while cows under 8-0 conditions averaged 0.16 ^k 0.04, In the 1800-2000h observation period, cows under 16-4 conditions averaged a proportion of 0.18 ^k 0.03 for ruminating, while cows under control conditions averaged a proportion of 0.07

*

0.02 for the same variable.

During the 2000-2200h observation penod, 16-8 cows spent less time rurninating (P < 0.01) than while under 8-0 treatment. The proportions of time observed were 0.35

*

^{0.04 for}

experimental cows and 0.59

*

0.04 for control cows.

2.4.3 Open-field test

When cows under control conditions were submitted to an open-field test, they spent more time immobile (P < 0.05) than cows under experirnental conditions in phase 1 (Table 2.3).

During phase 2, no differences were found between treatments for any variable. In phase 3, the only significant difference found between treatments was the number of defecations (P < 0.05).

TABLE 2.3 FREQUENCY AND TIME SPENT BY COWS IN DfFFERENT POSTURES A i D BEHAVIOURS DURING OPEN- FIELD TEST

VARIABLE Phase I Phase 2 Phase 3

Cohenzo~ 1 E.YPER[?YE~TAL 1 C O ~ O L 2 E.YPE~ENTAL 2 C O ~ O L 3 E Y P E ~ E ? ~ T A L 3

8-0 AFD 16-0 AFD 8-0 AFD 8 4 AFD 8-0 AFD 16-41 AFD

Mw,'r(*S.E. h k x ~ i S . E . MEAN*S.E. MEAV*S.E M~mf S.E. ME.^* S.E.

W B a E 546316.6' 536.6+j.ja 544.W7.6 537.9k12.6 534.1110.3 945 -8k4.2

2.5 Discussion

No differences were found on a 24-h basis in feeding behaviour (eating and mminating) between treatments in any of the three phases under study. This finding is consistent with data found in the cornplementary part of this study (Borderas et al., 1999) where feed intake and milk production were measured and no differences were found either. Proportions of time spent eating and mminating (Table 2) are consistent with those found in literature (Fraser, 1980; Dürst et al., 1993; Vasilatos and Wangsness, 1980) and are considered as normal values for dairy cows.

Although we expected an increase in feed intake arnong cows, it seems that the first feeding frequency, recornmended to f m e r s by the AFD manufacturer, gives cows enough time ⁽⁸ hrs) to satisfy their nutritional and physiological requirements, since diet composition

hrs) to satisfy their nutritional and physiological requirernents, since diet composition remained the same for al1 treatments. Vasilatos and Wangsness (1980) evaluated the feeding behaviour of ad libitum-fed lactating dairy cows, and they found that animals spent on average 253.6 midday eating. Dürst et al. (1993) have reported a value of 450 min for the slowest eating cow.

During phase 1, cows under 8-0 conditions spent more tirne eating than under 16-0 conditions in two observation periods of the day. In the 0600-0800h obsemation period, the difference between treatments was around 7%, and during the 1400-1600h observation period the difference was around 17%. These cows also spent more time immobile than those under 16-0 conditions during the 1200-1400h observation period (difference of 9%). Cows under 16-0 conditions ruminated more in the 1400-1600h (difference of 8%) and 2000-220011 (difference of 18%) observation periods, also showing an increase in the amount of time they spent immobile (difference of 6% ) for this same observation period. Cows with food available for only 8 hours spent more time consuming during certain time periods. Time periods where a significant increase in time spent eating was observed coincided with the sunrise and sunset feeding peaks mentioned in the literature (Ray and Roubicek, 1971 ; Ruckebusch and Bueno.

1978 ; Wilson and Flynn, 1979 ; Vasilatos and Wangsness, 1980 ; Gonyou and Stricklin, 198 1). as 0600-0800h and 1400- 1600h observation periods corresponded respectively to surrise and to the period immediately pnor to sunset at this season of the year in Quebec.

These intake peaks were not merely due to the passage of the

AFD,

since its schedule also coincided with other observation periods. Wilson and Flynn (1 979) mentioned that in winter.

cows compensate for the reduction of daylight hours by eating more food around midnight.

Cows in this study could not achieve this when they were under 8-0 conditions because no food was available at midnight.

The arnount of time that cows under 8-0 conditions spent eating in the 0600-0800h and 1400- 1600h observation penods (difference of 24% between control and expenmental conditions) was probably dedicated to ruminating by cows under 16-0 conditions since the increment in ruminating time for these cows at the sarne observation periods was around 26%. WhiIe cows under 16-0 conditions spent more time immobile (difference of 6%) dunng the 1800-2000h

observation period, cows under 8-0 treatment spent almost the same time immobile (difference of 9%) but at another observation period (1200- MOOh period). Since no significant differences for eating, ruminating, or immobility were observed on a 24 h basis, it seems that differences in feeding frequency (Le. food availability for 8 hours vs 16 hours) changed the behavioural patterns of cows but not the total time spent in each activity.

In the

znd

phase, cows under the 8-4 treatment, that means cows fed during day and night.

spent more ~ i m z niminating (diEiirsnie of 15?;), âiid lyiiig doux (diEc;cncc of !S?$) than cows under the 8-0 treatment during the 0600-0800h period. They also spent more time eating during the 1600-1 800h period (difference of 10%) and spent more time immobile during the 1000-1200h and the 1400-1600h periods (difference of 7% and 10%. respectively), and less time immobile during the 0200-0400h observation period (difference of 23%). During this phase, the cows under 8-4 treatment had 4 hours of AFD at night. The passage of

AFD

at night could be the reason for remaining less immobile during the 0200-0400h observation period.

The cows possibly tried to compensate for this difference by remaining immobile longer during the 1000- 1200h and the 1400- 16OOh observation periods and possibly by spending more tirne lying down at suruise (0600-0800h observation period). Wierenga and Hopster (1990) measured the amount of time that cows spend lying down, and they have found that when cows spend less time lying down dunng one night, they tend to compensate this absence by spending more time lying down the day after. The cows under 8-4 conditions tended to spend 13 % more time eating than under 8-0 conditions during the 0200-0400h observation period, and dthough this difference was not significant, it could have influenced the increased time they spent mminating during the 0600-0800h observation period.

During phase 3, the AFD ran continuously (24h) when cows were under expei-imental treatment. While under 8-0 conditions, the cows spent more time immobile (difference of 8%) and lying down (difference of 10%) than under 16-8 conditions on a 24h basis. When analyzing these variables by 2-h perîods, the cows under 16-8 conditions spent less time immobile than under the 8-0 treatment in the 0200-0400h penod (difference of 30%). The cows under control conditions Iay down more during periods 2000-2200h (difference of 6%), 0200-0400h (difference of 30%), and 0400-0600h (difference of 18%), than the cows under 16-8 conditions. These differences show that cows under 16-8 treatment did not rest as much

as under control treatment, and they also changed this pattern by spending more time lying d o m (diff'erence of 21%) during period 3 (1000-1200h) in order to compensate for the reduced resting time durhg the night. The cows also spent more time standing (difference of 9%) during the 0600-0800h observation period in the 8-0 situation compared to the 16-8 situation. The cows under these conditions probably lay down more in order to compensate for differences in resting time at night. Metz (1995) suggested that cows aim to achieve a rather fixed amount of time lying d o m , and that their well-being must seriously be impaired when lying time is restncted for several hours.

Cows fed frequently during day and night (16-8 treatment) spent more time eating and less time mrninating during the 2000-2200h observation period. They also spent more tirne eating during the 0000-0200h period. In contrast, the cows under 8-0 conditions spent more time eating and less time ~ m i n a t i n g during the 1000-1200h and 1800-2000h periods, probably to compensate for the reduced overall availability of food. As there were no significant differences for eating or mrninating on a 24h basis, these results show, as in the previous phases, that cows changed their intake patterns according to AFD schedule, but not the total time spent eating.

Open-field data are contradictory. Durhg phase 1, cows under 16-0 conditions moved more than under 8-0 conditions. Kilgour (1975) suggested that, in open-field tests for farm ruminants, the most emotional animal has the highest ambulation scores, since a ruminant is presumed to be adapted to eat rapidly and then to move to shelter to avoid predators. Results obtained in phase 1 could suggea that cows showed more distress to novelty under experimental conditions. For phase 2, no differences were found between treatrnents for any variable. For phase 3, the cows defecated more under 8-0 conditions than under 16-8 conditions. Cattle defecation responses are considered as an autonomic response to fear or distress (Kilgour, 1975; Fraser, 1980). As no other measures of stress were taken (i-e. cortisol levels, heart rate, etc.), it is dificult to confirm that these differences are related to the treatrnents. Anyway, differences were rather mal1 and other factors may have influenced the results. For exarnple, leading the cows to the arena was sometimes dificult because of the f m ' s layout.

2.6 Conclusion

The main conclusion is that the increase in feeding fiequency did not increase the time spent eating or the food intake on a 24-h basis, but it did change the behavioural patterns of intake.

The 24-h AFD continuous feeding practice could have some influence on the time that cows

Dans le document COMPORTEMENT DES VACHES LAITIÈRES. de l'université Lavai. Département des sciences animales UNIVERSITÉ LAVAL (Page 51-56)