Anne Boudon

In dairy cows, early lactation is a period prone to oxidative stress, inflammation and health problems. Our objective was to investigate the effects of the nutritional supplementation of early lactating cows with plant extracts or vitamin E on physiological and immunological status. Forty-five Holstein cows were divided into three groups: control group (n = 15), vitamin E group (n = 16) (3,000 IU/d for 3 weeks before and 1,000 IU/d after calving), and plant extract group (n = 14) (10 g/d only after calving). Their redox and immune status were monitored during the first 12 weeks of lactation, every four week. In week 12, plasma malondialdehyde levels in plasma were lower in the vitamin E and plant extract groups than in the control group. The vitamin E and plant extract groups had lower ex vivo plasma CCL4, IL6 and IL8 cytokine levels, lower proportions of blood regulatory neutrophils, and less ROS production by blood neutrophils than the control group. In terms of immune response, vitamin E and plant extracts down-regulated the gene expression of FABP3 in the milk mammary epithelial cells of multiparous cows. Therefore, supplementation with either vitamin E or plant extracts could prevent systemic hyper-inflammation and improve the immune response during early lactation.

Background: Early lactation is a period at risk for mastitis. Our objective was to investigate the influence of nutritional vitamin E and plant extracts on redox and immune status at the systemic and local mammary levels during an inflammatory challenge in dairy cows. Thirty-six Holstein cows were placed in three groups: a ‘control’ group (n = 11) unsupplemented; a ‘vitamin E’ group (n = 13), supplemented with 3000 IU/d for 4 weeks before calving and 1000 IU/d for 4 weeks after calving; and a ‘plant extracts’ group (n = 14) supplemented with 10 g/d for 4 weeks before and after calving. Lipopolysaccharide (LPS) from Escherichia coli was infused into a one-udder quarter of the cows 5 weeks after calving. Blood and milk samples were collected before and 4, 7, 9, 28, and 76 h after the LPS infusion. Results: In the plant extract group, antioxidant gene ( NQO1 ), superoxide dismutase activity 4 hours after the LPS challenge and total antioxidant capacity were increased compared to the control group. In the vitamin E group, expression of the antioxidant gene ( SOD3 ) and glutathione peroxidase activity were more elevated than in the control group. Systemic immunity appeared to be reduced by antioxidant supplementations, with a higher migration of classical neutrophils in the plant extract group and less ROS production of neutrophils in the vitamin E group. However, immune capacities were increased at the local level in classical neutrophils (ROS production and phagocytosis) in both the plant extract and vitamin E groups. Following the LPS infusion, supplementation did not reveal any differences in terms of rectal temperature, milk yield or milk cell counts, but it did have a positive effect on mammary epithelium integrity (lower milk Na ⁺ :K ⁺ ratio and higher OCLN gene expression). In addition, the plant extracts stimulated the synthesis of milk constituents, with higher milk protein gene expressions ( LALBA , CSN3 , CSN1S1 ) and a tendency towards a higher lactose content in milk. Conclusion: The LPS challenge showed that vitamin E or plant extracts enhanced the local inflammatory response while preserving systemic antioxidant capacities, integrity of the mammary gland and the composition of milk, and thus possibly contributing to preventing mammary infection in early lactating dairy cows.

Summary: Relations were studied among the major osmotic agents (lactose, Na, K, Cl, and protein) in milk from dairy cows with somatic cell count (SCC) below 200,000 cells/mL of milk and fed a diet with a constant composition. The results revealed that the lactose content and the primary osmotic agent differed between primiparous and multiparous cows and varied mainly at the onset of lactation for each, whereas milk osmolarity did not change. Other osmotic agents varied throughout lactation, and some differed between parities. At the onset of lactation, a low lactose content was associated with lower Cl and K contents for multiparous cows but not for primiparous cows. During the rest of lactation, the profile of osmotic agents followed similar dynamics over the days in milk (DIM) for both parities.

On dairy farms, milking practices can temporarily restrict cows from accessing drinking water. This study examined how different types of temporary water restriction, similar to those commonly encountered on farms, may affect the individual behavior and physiological dehydration status of cows and whether these effects could differ according to the cow's position in the social hierarchy of the group. Four treatments were applied (CTRL = free access to the drinker and feed fence, HL = 2 h of headlock at the feed fence after morning and evening milking, D2H = free access to the feed fence and no access to water for 2 h after milking, and D4H = free access to the feed fence and no access to water for 4 h after milking) to 4 groups of 10 lactating dairy cows using a 4 × 4 Latin square design. Each treatment period lasted 1 wk. The cows were housed within a freestall barn, and each group was in a pen equipped with 1 electronic drinker, 10 individual feeders, and 2 cameras. Cow social dominance hierarchies were characterized using normalized David's scores, which were calculated from video-detected replacements at each pen's drinker. During the last 4 d of each treatment period, drinking behavior was measured using interconnected drinkers, and eating, idle, and lying times were measured using accelerometers. On d 6 of each treatment period, during the morning and evening milkings, blood and then milk samples were collected to analyze bioindicators of dehydration and milk composition, respectively. The daily water intake of cows was unaffected by either social dominance or treatment type. Drinking rate and drinking bout frequency were higher during the HL, D2H, and D4H treatments than during the CTRL treatment, and drinking time was lower during the D4H treatment than during the CTRL treatment. Hourly lying time decreased at the end of the water restriction periods, that is, at 1000 h in HL, at 1100 h in D2H, and at 1200 and 1300 h in D4H, which was not observed in CTRL, which could be interpreted as a sign of cow discomfort. For blood collected before the morning milking, hematocrit levels were lower in the D4H treatment than in the HL treatment. For blood collected before the evening milking, creatinine concentrations were lower in the D4H treatment than in the D2H treatment, with a greater difference seen for dominant cows than for subordinate cows. For both milkings, milk freezing point was higher in the HL, D2H, and D4H treatments than in the CTRL treatment, indicating dilution. In contrast to the other social categories, subordinate cows made more daily visits to the drinker during the D4H treatment than during the CTRL treatment but displayed no differences in drinking bout duration or the duration of drinking interruptions within bouts in the D2H treatment compared with the CTRL treatment. Overall, cows were able to maintain their water intake despite the temporary water restrictions when they had access to the number of drinkers recommended by animal welfare guidelines. That said, their idle and lying time appeared to be disturbed.

Studies using fistulated ruminants have shed light on digestion and fermentation in the rumen and yielded tools to determine the feed efficiency of diets, limit effluents or anticipate variability in the quality of animal products. However, the ethical acceptability of such studies has been called into question. Our objective was to determine whether oral-stomach sampling (OSS) is an acceptable alternative to sampling through a ruminal cannula in characterizing the variability of rumen fluid composition induced by an acidogenic dietary challenge in dairy cows. During three four-week periods (P1, P2, P3), six rumen-fistulated cows were fed a standard diet based on supplemented corn silage (periods 1 and 3) alternating with a diet enriched with starch (period 2). Rumen juice was collected through cannulas at three locations in the rumen (reticulum, ventral sac or a mix of both) and by OSS, once per week at 0830 h, i.e. before morning feeding, and once every third week of each period at 1330 h, i.e. 4.5 hours after morning feeding. Whatever the sampling method or location, ruminal pH was lower in period 2 compared to periods 1 and 3 at 1330 h (6.21 vs. 5.57 vs. 6.12 in periods 1, 2 and 3). Ruminal pH was higher when obtained by OSS rather than cannulation, whatever the sampling location (on average, +0.44 points at 0830 h and +0.56 points at 1330 h). Mineral composition indicated a presumed dilution by saliva of OSS samples. This was also consistent with lower concentrations of volatile fatty acids. The next steps will be to analyze the associated variations in in vitro rumen fermentation parameters and microbiota composition. Implications: The use of fistulated ruminants to elucidate ruminal physiology is currently controversial in society. In order to minimise, reduce or replace these experimental models, alternatives to ruminal fistula sampling are being evaluated. Here we focus on oral stomach sampling (OSS). We show that OSS can be a satisfactory alternative to cannula sampling in the evaluation of rumen fermentation parameters, especially for the molar proportion of volatile fatty acids, rumen pH, and rumen volatile fatty acid and ammonia concentrations. We also show that OSS must be standardized to avoid salivary contamination affecting the quality of the results.

Summary: The absence of thirst is key to good welfare, but little is known about how farm management can affect the drinking behavior of dairy cows. We studied how stocking density and limited feed-access times impacted cows' drinking behavior. We expected that the effects of competition would vary depending on social status, so effects on dominant, intermediate, and subordinate cows were assessed separately. Dominants were not impacted by treatments, but intermediates and subordinates drank less water when feed was available for just part of the day. Subordinates spent less time drinking when overstocked. Some cows delayed drinking when competition increased. We conclude that competition for access to feed and water impacts drinking behavior, especially for subordinate cows.

Summary Access to sufficient drinking water is an essential part of animal welfare. It is known that rearing conditions and social dominance hierarchies can influence cow drinking behavior. Here, we explored the interaction between drinker numbers and social dominance for a group of 40 cows. When cows were given the number of drinkers specified by current official standards (1 drinker per 10 cows), dominant cows monopolized access and drank 5 L more than when drinker density was higher (1 per 3.3 cows). Furthermore, at the lower drinker density, drinking frequency and rate increased for cows of all dominance levels but particularly for subordinates; mid-subordinates shifted to off-peak drinking times. Our results illustrate that current standards for drinker numbers can lead to competition among animals, whose behavioral responses may depend on their level of social dominance. In conclusion, technical guidelines should be carefully revisited with a view to ensuring animal welfare on dairy farms.