Effect of concentrate enriched with palmitic acid versus rapeseed oil on dairy performance, milk fatty acid composition, and mammary lipogenic gene expression in mid-lactation Holstein cows.

This study was performed to characterize the effect of a concentrate supplemented with free palmitic acid (4% on a DM basis; PA) or rapeseed oil (4% on a DM basis; RO) compared with a no-added-lipid control concentrate (CT) on the performance of dairy cows fed a corn silage-based diet over a 9-wk period. After a 3-wk pre-experimental period, 54 Holstein cows were randomly allocated to 3 experimental treatments to receive forage ad libitum with a fixed amount of CT, RO, or PA (8 kg/d for 2-yr-old primiparous; 10 kg/d for older cows). During the experiment, dry matter intake, milk yield and composition, fatty acid (FA) yields and FA profile, and feed efficiency were determined. At wk 9 of the experimental period, the mRNA levels of 10 genes involved in lipid metabolism in mammary tissue biopsy samples were measured. Compared with CT, RO and PA increased forage intake. Compared with CT, RO increased concentrate intake, the value being intermediate for PA. Compared with CT, RO increased milk yield (+2.0 kg/d) and decreased milk fat and protein content (-3.8 and -1.2 g/kg, respectively), whereas PA increased milk fat content (+4.1 g/kg). Compared with CT and RO treatments, PA increased milk fat yield (+179 g/d) and 3.5% fat-corrected milk and energy-corrected milk output (+2.8 and +2.3 kg/d, respectively), and thus improved feed efficiency (+7.3%). Compared with CT treatment, RO increased milk contents of the sum of >C16 FA, monounsaturated FA, polyunsaturated FA, trans FA, and n-3 FA, whereas PA decreased these FA contents (except n-3 FA) and also decreased n-6 FA. The variations in milk fat yield and content and FA secretion at wk 9 were not associated with modifications in mammary expression of 10 genes involved in major lipid pathways, except for the transcription factor PPARG1, which tended to be higher in PA versus RO treatment. This study demonstrated that PA improved milk fat yield and feed efficiency compared with RO and suggests that factors other than gene expression, such as substrate availability for mammary metabolism or other levels of regulation (transcriptional, posttranscriptional, translational or posttranslational), could play a key role in milk fat and FA responses to changes in diet composition in cows.

Individual responses of dairy cows to a 24-hour milking interval.

Some dairy farmers opt to omit one milking, either incidentally or weekly, without changing other milking times. This practice entails an extended milking interval of 24h (24h-MI), which is associated with a decrease in milk yield. This decrease varies among cows and could be partly due to factors such as stage of lactation and milk yield level. The aim of this study was to describe the average and individual responses in terms of loss and carryover effects of a 24h-MI on milk yield. The influence of factors such as parity, stage of lactation, and milk yield potential were investigated, together with response repeatability. Our trial used 292 Holstein-Friesian cows, and consisted of 3 successive periods: 1 wk of twice-daily milking (TDM) as a control, one 24h-MI, and then 13d of TDM. The number of observations per cow ranged from 1 to 9, with no more than three 24h-MI per lactation. The 24h-MI reduced milk yield by 23% (7.8 kg on average) and milk lactose content by 2.6g/kg on the 24h-MI day. Milk fat and protein content, and somatic cell score increased by 3.0 g/kg, 0.5 g/kg, and 0.4 units, respectively. No significant carryover effect was found of a 24h-MI on milk yield or milk composition 2 wk after resumption of TDM. Milk yield loss and recovery varied widely (coefficient of variation 62%), and the relationship between milk loss and milk recovery showed substantial variation (residual standard deviation 2.1 kg/d). Cows with a greater milk potential level lost more milk yield but recovered more milk, with no influence on recovery:loss ratio. Cows in early lactation recovered the lost milk yield faster. Repeatability of the responses to a 24h-MI was 44% for milk yield loss (kg/d), 57% for relative milk yield loss (%), 33% for milk yield recovery (kg/d), and 0% for milk recovery:loss ratio (%), suggesting a genetically determined ability to limit loss when one milking is omitted. To conclude, a 24h-MI caused higher milk yield losses than reported in previous studies. Stage of lactation, estimated potential milk yield level, and parity explained the cows' response to the 24h-MI, but did not account for all the individual variability.

Rapeseed or linseed in dairy cow diets over 2 consecutive lactations: effects on adipose fatty acid profile and carry-over effects on milk fat composition in subsequent early lactation.

During early lactation, milk fatty acid (FA) composition is influenced by diet, animal genetics, and the high availability of preformed FA from body-fat mobilization. Long-term prepartum dietary oilseed supplementation could, therefore, modify milk FA composition postpartum in the subsequent lactation through changes in adipose tissue (AT) FA profile. To test this hypothesis, measurements were made in 19 Holstein cows fed grass-based diets containing no additional lipid (control, CTL; n=4) or supplemented with extruded linseeds (EL; n=4), cold-pressed fat-rich rapeseed meal (FRM; n=6), or whole unprocessed rapeseeds (WR; n=5) over 2 consecutive lactations (yr 1 and 2) and 2 dry periods. Oilseed supplements were withdrawn from the diets 23 d before the calving of yr 3, following the end of the previous experimental periods in yr 1 to 2. Thereafter, all cows received a total mixed ration composed of grass silage, grass hay, and concentrates (forage:concentrate ratio of 70:30 on a dry-matter basis). Cows previously fed EL and WR had a lower milk fat content (6.32% for CTL and FRM vs. 5.46% for EL and WR) and yield (1.90kg/d for CTL and FRM vs. 1.61kg/d for EL and WR) during the first week of lactation. Treatment effects on milk fat content and yield did not persist into lactation wk 3 and 7. Whatever the week, EL and WR increased concentration of FA in milk synthesized de novo (i.e., carbon number ≤15; 17.1g/100g of FA for CTL and FRM vs. 22.2g/100g of FA for EL and WR) and decreased concentration and secretion of preformed FA (i.e., carbon number ≥17; 56.1g/100g of FA for CTL and FRM vs. 49.9g/100g of FA for EL and WR). Alterations in milk FA composition may be explained by the lower availability of mobilized FA for uptake by the mammary gland, as indicated by the lower plasma nonesterified FA concentrations for EL and WR compared with CTL and FRM. Prepartum EL feeding increased AT and milk concentration of 18:3n-3 (0.96 vs. 0.79g/100g of milk FA for EL and the other groups, respectively) and intermediates of ruminal 18:3n-3 biohydrogenation. In contrast, FRM increased AT and milk concentration of ruminal cis-9 18:1 biohydrogenation intermediates. However, EL and FRM supplements resulted in a similar profile of 18-carbon FA isomers in AT (yr 2) and milk (yr 3, 4-10 wk after removing oilseeds from the diet). In conclusion, results confirm that long-term feeding of oilseed supplements alter AT FA composition and may influence milk FA composition during periods of extensive body-fat mobilization such as early lactation.

Effects of body condition score at calving on indicators of fat and protein mobilization of periparturient Holstein-Friesian cows.

The objective was to study the effects of body condition score (BCS) at calving on dairy performance, indicators of fat and protein mobilization, and metabolic and hormonal profiles during the periparturient period of Holstein-Friesian cows. Twenty-eight multiparous cows were classed according to their BCS (0 to 5 scale) before calving as low (BCS ≤ 2.5; n=9), medium (2.75 ≤ BCS ≤ 3.5; n=10), and high (BCS ≥ 3.75; n=9), corresponding to a mean of 2.33, 3.13, and 4.17 points of BCS, and preceding calving intervals of 362, 433, and 640 d, respectively. Cows received the same diets based on preserved grass to allow ad libitum feed intake throughout the study, and lactation diet contained 30% of concentrate (dry-matter basis). Measurements and sampling were performed between wk -4 and 7 relative to calving. No significant effects were observed of BCS group on dry matter intake (kg/d), milk yield, BCS loss, plasma glucose, and insulin concentrations. The high-BCS group had the lowest postpartum energy balance and the greatest plasma concentrations of leptin prepartum, nonesterified fatty acids and ß-hydroxybutyrate postpartum, insulin-like growth factor 1, and milk fat content. Milk fat yield was greater for the high- than the low-BCS group (1,681 vs. 1,417 g/d). Low-BCS cows had the greatest concentration of medium-chain fatty acids (e.g., sum of 10:0 to 15:0, and 16:0), and the lowest concentration and secretion of preformed fatty acids (e.g., cis-9 18:1) in milk fat. Milk protein secretion was lowest in the low-BCS group, averaging 924, 1,051, and 1,009 g/d for low-, medium-, and high-BCS groups, respectively. Plasma 3-methylhistidine was greater in wk 1 and 2 postpartum compared with other time points, indicating mobilization of muscle protein. Plasma creatinine tended to be lower and the 3-methylhistidine: creatinine ratio was greater in low- compared with medium- and high-BCS cows, suggesting less muscle mass but more intense mobilization of muscle protein in lean cows. High-BCS cows were metabolically challenged during early lactation due to intense mobilization of body fat. Conversely, limited availability of body fat in low-BCS cows was associated with increased plasma indicators of body protein mobilization during the first weeks of lactation, and lower milk protein secretion. These results should be confirmed using an experimental approach where calving BCS variation would be controlled by design.

Invited review: reduced milking frequency: milk production and management implications.

Most dairy cows throughout the world are milked twice daily. In intensive dairying systems, however, it is not uncommon to increase milking frequency to between 3 and 6 times daily to increase milk production. Reducing milking frequency is much less common; however, once-daily milking of dairy cows, practiced either strategically during certain parts of the lactation or for the entire lactation, is not uncommon in key dairying countries where less emphasis is placed on milk production per cow. The practice fits well with more extensive dairy production systems, particularly those based on grazed pasture. A feature of once-daily milking is that it reduces milk yield by approximately 22%, depending on stage of lactation, breed, and parity, and it may adversely affect lactation length and persistency. However, it can offer several positive farm management options, especially related to labor requirements and farm working expenses. In addition, it may provide a tool to better manage the metabolism and energy balance of cows during early lactation or during periods of pasture deficit, and it may help to improve reproductive performance and animal health and welfare. Once-daily milking, representing one extreme of the mammary function spectrum, has attracted considerable research interest over the years. Consequently, substantial scientific information is available on its effects on mammary function, at both the physiological and molecular levels. This review focuses instead on the management of the cow milked once daily, covering the production response in relation to breed, stage of lactation, and parity, and its effect on energy status, reproduction, health and welfare, as well as on milk composition and processability.

Rapeseed or linseed supplements in grass-based diets: effects on milk fatty acid composition of Holstein cows over two consecutive lactations.

Persistency of changes in milk fatty acid (FA) composition to 4 different oilseed supplements rich in cis-9 18:1 or 18:3n-3 was determined over 2 consecutive lactations in 58 and 35 Holstein cows during the first and second years, respectively. During the initial 5 wk of the study, all experimental cows were fed the same diet. Thereafter, cows received 1 of 5 treatments for 2 consecutive lactations, including the prepartum period. Treatments comprised the basal diet with no additional lipid, or supplements of extruded linseeds (EL), extruded rapeseeds (ER), cold-pressed fat-rich rapeseed meal (FRM), or whole unprocessed rapeseeds (WR). Oilseeds were offered to provide between 2.5 to 3.0% of additional oil in diet dry matter. During indoor periods, cows received a mixture (3:1, wt/wt) of grass silage and grass hay, whereas cows were at pasture during outdoor periods. Over the entire study, oilseed supplements decreased the concentration of milk FA synthesized de novo and increased 18:0 and cis-9 18:1 content, with a ranking of treatment responses (highest to lowest) of FRM, EL, ER, and WR. Irrespective of period, both EL and FRM increased total milk trans FA content, whereas WR resulted in lower concentrations in milk from grazing cows. Relative to rapeseed, EL resulted in higher increases in milk cis-12,cis-15,trans-12 to -16 18:1, nonconjugated trans 18:2 (especially ∆11,15), and 18:3n-3. In contrast, rapeseed supplements resulted in a greater enrichment of cis-11 18:1, trans-4 to -9 18:1, and cis 20:1 than EL. Changes in milk FA composition to oilseeds were of greater magnitude during indoor than outdoor periods, where oilseed supplements often decreased cis-9,trans-11 conjugated linoleic acid content. During the second indoor period, both EL and ER resulted in higher total trans FA content, trans-10 18:1 in particular, than during the first indoor period, consistent with an interaction between dietary starch content and oilseed supplement. Overall, the extent of changes in milk FA composition were related to the nature (rapeseed or linseed) and form of oilseed (extruded, cold-pressed fat-rich meal or whole unprocessed), and their interactions with the composition of the basal diet (grass silage and hay or pasture; or dietary starch content). Milk FA responses were stable within each period and repeatable over both outdoor feeding periods, with extent of changes being comparable to reports from relatively short-term (1- to 3-mo) studies.

Rapeseed or linseed supplements in grass-based diets: effects on dairy performance of Holstein cows over 2 consecutive lactations.

The aim of this study was to evaluate the effects of long-term supplementation with different oilseeds rich in 18:1 cis-9 or 18:3n-3 fatty acids on dairy cow performance over 2 consecutive lactations. This trial involved 58 Holstein cows during the first year and 35 during the second year. During the first 5 wk of the first year, all of the cows were fed the same diet; after a 4-wk transition period, the cows received 1 of 5 treatments for 2 consecutive lactations, including the dry period. Their basal diet was supplemented or not with extruded linseeds or with different forms of rapeseeds: extruded seeds, cold-pressed fat-rich meal, or whole unprocessed seeds. Oilseed amount was calculated to provide 2.5 to 3.0% additional oil in ration dry matter. Cows were fed a grass-based diet (75% grass silage and 25% hay) during indoor periods and grazed during outdoor periods. For the first year of experimentation, oilseed supplementation had no effect on milk, fat, protein, and lactose yields, body weight, or body condition score compared with the control treatment (no oilseed supplementation). During the indoor period, extruded linseed tended to decrease dry matter intake (-1.5 kg/d), whereas all of the oilseed treatments decreased milk protein content without changing protein yield. Cold-pressed fat-rich rapeseed meal decreased milk protein content independently of the period (-0.29 and -0.19 g/100 g for indoor and outdoor periods, respectively), and whole unprocessed rapeseed increased milk fat content during the outdoor period (+0.53 g/100 g compared with the control treatment). During the second year of experimentation, the effects of oilseed supplementation during the outdoor period were similar to those observed during the first outdoor period, but the effects of oilseed supplementation differed between the 2 indoor periods. This was likely due to changes in forage quality and composition and percentage in the ration of the concentrate mixtures. Thus, the effects of oilseed supplementation depended on oilseed nature (rapeseed or linseed) and form (extruded seeds, cold-pressed fat-rich meal, or whole unprocessed seeds) in interaction with the type of basal diet (grass silage and hay or pasture) and the concentrate composition and percentage in the ration. Effects were stable during the first indoor period, repeatable between the 2 outdoor periods, and were similar to effects observed previously in short-term studies (1 to 3 mo).

Animal performance and stress at weaning when dairy cows suckle their calves for short versus long daily durations.

Calves in most dairy farms are separated from their dams either immediately or within a few hours after birth, prompting increasing concern of the society for reasons of animal welfare. The aim of this study was to identify systems to maintain cow-calf contact (CCC) that balance the benefits for calf growth and health against the negative impacts on sellable milk and stress at weaning. We tested reuniting cows and calves for 20 min before (Before-group) or 2.5 h after (After-group) morning milking (in Trial 1) or for a 9 h period between the morning and evening milkings (Half-day-group, in Trial 2). In Control-groups, calves were separated from their dam at birth and fed with artificial nipple with tank milk provided daily at 13% (Trial 1) and 14% (Trial 2) of their BW. In both trials, each practice was applied on a group of 14 dam-calf pairs (7 Holstein [Ho] and 7 Montbéliarde [Mo]). All calves were weaned at a BW of at least 100 kg. In Trial 1, the After-group was prematurely stopped when the calves were eight weeks of age as calf growth became limited (340 g/d) due to low milk intakes (2.97 kg/d). During the first eight weeks of lactation, milk yield at the parlour was 29%, 51% and 42% lower in After-, Before- and Half-day-cows respectively compared to Controls. From week 14 to 16 when all calves were separated from their dam, Before-cows still produced 25% less milk than Control-cows while Half-day-cows reached the milk yield of Control-cows within a week. There were no significant differences in milk somatic cell count and in frequency of health disorders (cows and calves) between suckling and Control-groups. Compared to Control-calves, calf growth until weaning was higher in the suckling calves in Trial 1 (861 vs 699 g/d) and similar in Trial 2 (943 vs 929 g/d). At weaning, Before- and Half-day-calves started to vocalise earlier and continued to vocalise longer than Controls. In conclusion, the best compromise between cow milk yield and calf growth is a long period of CCC (9 h) between the morning and evening milkings. Still abrupt weaning stresses both cows and calves even if CCC has been restricted before separation.

Strategies for keeping dairy cows and calves together - a cross-sectional survey study.

Although it is still most common to rear dairy calves separately from adult cattle, the interest in prolonged contact between dairy calves and lactating cows during early life is increasing. Previous research has documented positive effects of cow-calf contact (CCC) on for example early calf growth and udder health of suckled cows, but also negative effects such as increased separation distress and reduced weight gains after weaning. The aim of this study was to use information from European farms with prolonged cow-calf contact to identify innovative solutions to common challenges for CCC farms. Commercial dairy farms that kept calves with adult lactating cows for seven days or more after birth were invited to participate, and interviews were performed with 104 farmers from six countries. During interviews, information about farm management, calf rearing, farmers' perception of animal health on their farm, and farmers' drivers and barriers for implementing CCC were collected. We found that CCC was practised in a large variety of housing and management systems, and that calves could be reared together with their dam, with foster cows, or using a combination of the two. The contact period varied considerably (7-305 days) between farms and about 25% of the farms manually milk fed the calves during parts of the milk feeding period. Daily contact time varied between farms, from 30 minutes per day to permanent contact except at milking. Behaviours indicative of separation distress, most commonly vocalisation in cows and calves, were reported by 87% of the farmers. Strategies to alleviate separation distress, for example simultaneous gradual weaning and separation, were used on some farms. Building constraints were most often mentioned as a barrier for implementing CCC. Our findings suggest that CCC is practised in a variety of commonly used husbandry systems. Reported challenges were primarily related to weaning and separation, and to building constraints; these aspects should be areas of future research.

Yield and sensory properties of cheese made with milk from Holstein or Montbeliarde cows milked twice or once daily.

The aim of this study was to evaluate the milk properties and the yield and sensory properties of Cantal cheese made with milk from Holstein or Montbéliarde cows milked once or twice daily. Sixty-four grazing cows [32 Holstein (H) and 32 Montbéliarde (M) cows] in the declining phase of lactation (157 d in milk) were allocated to 1 of 2 equivalent groups milked once daily (ODM) or twice daily (TDM) for 7 wk. The full-fat raw milk collected during 24 h from the 4 groups of cows (M-TDM, M-ODM, H-TDM, and H-ODM) was pooled and processed into Cantal cheese 4 times during the last 4 wk of the experimental period. In all, 16 cheeses were made (2 milking frequencies x 2 breeds x 4 replicates) and analyzed after a ripening period of 15 and 28 wk. The results showed that for both breeds, the pooled milk content of fat, whey protein, casein, total protein, and phosphorus as well as rennet clotting time and curd firming time were significantly higher with ODM cows, whereas the casein-to-total protein ratio was lower, and lactose, urea, calcium, and free fatty acids contents of milk remained unchanged. The acidification and draining kinetics of the cheese as well as cheese yields and the chemical and rheological properties of the ripened cheese were not significantly modified by milking frequency. For both breeds, the cheeses derived from ODM cows had a slightly yellower coloration but the other sensory attributes, except for pepper odor, were not significantly affected by milking frequency, thereby demonstrating that ODM does not have an adverse effect on the sensory properties of Cantal cheese. Compared with that of Holstein cows, milk from Montbéliarde cows resulted in a higher cheese yield (+1.250 kg/100 kg of milk) and ripened cheeses with lower pH, dry matter, calcium, sodium chloride, and water-soluble nitrogen concentrations. These cheeses had also a less firm and more elastic texture, a more acidic taste, and a yogurt/whey aroma.

Physiological adaptations and ovarian cyclicity of Holstein and Montbéliarde cows under two low-input production systems.

The objective was to study milk production, body reserve mobilization, metabolic and hormonal profiles, and ovarian cyclicity of Holstein-Friesian (HOLS) and Montbéliarde (MONT) cows under two low-input dairy production systems with seasonal spring calving: an extensive (EXT; 12 HOLS and 12 MONT) based on permanent diversified grasslands and zero concentrate, and a semi-extensive (SEMI; 12 HOLS and 10 MONT) based on established temporary grasslands and up to 4 kg/day of concentrate. Individual measurements were performed between -4 and 12 weeks of lactation. Cows in EXT secreted less milk (22.1 v. 24.4 kg/day), protein (660 v. 755 g/day) and energy (67.7 v. 74.4 MJ/day), had greater plasma ß-hydroxybutyrate (BHBA) (0.97 v. 0.69 mM), lower glucose (59.0 v. 62.0 mg/dl) and IGF-1 (62 v. 71 ng/ml), lower milk fat concentration in fatty acids originating from de novo synthesis (e.g. ∑ 10:0 to 15:0) and greater concentration of those derived in part from mobilization of fat reserves (e.g. 18:0 and ∑>C16), and showed greater frequency of abnormal ovarian cycles compared with SEMI. Across production systems, HOLS produced more milk (24.7 v. 21.8 kg/day), protein (738 v. 674 g/day) and fat (939 v. 819 g/day), secreted more energy (75.1 v. 67.0 MJ/day), lost more body condition score (BCS) (1.41 v. 1.03) and reached a lower BCS nadir (1.12 v. 1.43), had greater plasma BHBA (0.91 v. 0.75 mM), lower insulin (15.9 v. 17.2 µIU/ml) and tended to have lower glucose (59.6 v. 61.4 mg/dl), had lower milk fat concentration in ∑ 10:0 to 15:0, tended to have higher ∑>C16 and tended to show more abnormal estrous cycles compared with MONT. Ultrasound measurements did not differentiate fat mobilization and were confounded by breed differences of skin thickness. The greater nutrient allowance in SEMI improved indicators of physiological status and ovarian function during early lactation compared with EXT, but did not attenuate body reserve mobilization because cows prioritized milk secretion. HOLS secreted more nutrients than MONT but lost more BCS, which negatively affected nutritional balance and tended to affect ovarian cyclicity during early lactation. Breed by system interactions were not observed except for a few variables.

Frequent moving of grazing dairy cows to new paddocks increases the variability of milk fatty acid composition.

The aim of this work was to investigate the variations of milk fatty acid (FA) composition because of changing paddocks in two different rotational grazing systems. A total of nine Holstein and nine Montbéliarde cows were divided into two equivalent groups according to milk yield, fat and protein contents and calving date, and were allocated to the following two grazing systems: a long duration (LD; 17 days) of paddock utilisation on a heterogeneous pasture and a medium duration (MD) of paddock utilisation (7 to 10 days) on a more intensively managed pasture. The MD cows were supplemented with 4 kg of concentrate/cow per day. Grazing selection was characterised through direct observations and simulated bites, collected at the beginning and at the end of the utilisation of two subsequent MD paddocks, and at the same dates for the LD system. Individual milks were sampled the first 3 days and the last 2 days of grazing on each MD paddock, and simultaneously also for the LD system. Changes in milk FA composition at the beginning of each paddock utilisation were highly affected by the herbage characteristics. Abrupt changes in MD milk FA composition were observed 1 day after the cows were moved to a new paddock. The MD cows grazed by layers from the bottom layers of the previous paddock to the top layers of the subsequent new paddock, resulting in bites with high organic matter digestibility (OMD) value and CP content and a low fibre content at the beginning of each paddock utilisation. These changes could induce significant day-to-day variations of the milk FA composition. The milk fat proportions of 16:0, saturated FA and branched-chain FA decreased, whereas proportions of de novo-synthesised FA, 18:0, c9-18:1 and 18:2n-6 increased at paddock change. During LD plot utilisation, the heterogeneity of the vegetation allowed the cows to select vegetative patches with higher proportion of leaves, CP content, OMD value and the lowest fibre content. These small changes in CP, NDF and ADF contents of LD herbage and in OMD values, from the beginning to the end of the experiment, could minimally modify the ruminal ecosystem, production of precursors of de novo-synthesised FA and ruminal biohydrogenation, and could induce only small day-to-day variations in the milk FA composition.

Towards an agroecological assessment of dairy systems: proposal for a set of criteria suited to mountain farming.

Ruminant production systems have been facing the sustainability challenge, namely, how to maintain or even increase production while reducing their environmental footprint, and improving social acceptability. One currently discussed option is to encourage farmers to follow agroecological principles, that is, to take advantage of ecological processes to reduce inputs and farm wastes, while preserving natural resources, and using this diversity to increase system resilience. However, these principles need to be made more practical. Here, we present the procedure undertaken for the collaborative construction of an agroecological diagnostic grid for dairy systems with a focus on the mountain farming relying on the use of semi-natural grasslands. This diagnosis will necessarily rely on a multicriteria evaluation as agroecology is based on a series of complementary principles. It requires defining a set of criteria, based on practices to be recommended, that should be complied with to ensure agroecological production. We present how such agroecological criteria were identified and organized to form the architecture of an evaluation model. As a basis for this work, we used five agroecological principles already proposed for animal production systems. A group of five experts of mountain production systems and of their multicriteria evaluation was selected, with a second round of consultation with five additional experts. They first split up each principle into three to four generic sub-principles. For each principle, they listed three to eight categories of state variables on which the fulfilment of the principle should have a positive impact (e.g. main health disorders for the integrated health management principle). State variables are specific for a given production, for example, dairy farms. Crossing principles with state variables enabled experts to build five matrices, with 75 cells relevant for dairy systems. In each cell, criteria are specific to the local context, for example, mountain dairy systems in this study. Finally, we discuss the opportunities offered by our methodology, and the steps remaining for the construction of the evaluation model.

Performance of dairy cows milked twice daily at contrasting intervals.

The time constraints of the classic twice-daily milking routine are less easily endured by individual dairy farmers, because of their impact on quality of life. Our aim was to evaluate milk production responses by dairy cows milked twice daily at contrasting intervals. In experiments 1 (20 cows) and 2 (28 cows), four milking regimes were compared during a 3-week period beginning after the peak of lactation. Three groups of five cows were milked twice daily (TDM) with milking intervals of 11 : 13, 7 : 17 and 3 : 21 h in experiment 1, and three groups of seven cows at 11 : 13, 5 : 19 and 2.5 : 21.5 h in experiment 2. One group (five and seven cows respectively) was milked once daily (ODM) in each experiment. In experiment 3 (three groups, 12 cows per group), one group was milked at 10 : 14 h and one at 5 : 19 h, and the third group once daily. Milking treatments began during the second week of lactation and continued for an average of 23 weeks. In experiments 1 and 2, daily milk yields were reduced by 4.1%, 11.5% and 28%, for the 5 : 19, 3 : 21 and ODM milking treatments compared with the 11 : 13 h interval. In experiment 3, the decrease in daily milk yields for 5 : 19 h and ODM was 10% and 40% compared with the 10 : 14 h time interval. In the average daily milk, fat and protein contents and somatic cell counts were not different between the TDM groups, and the ODM group had (or tended to have) a higher fat and protein content. For a given milking, milk fat content decreased from about 60 to 32 g/kg as the preceding milking interval increased from 2.5 to 3 h up to 12 h. It then levelled out and even increased, mainly after 18 to 20 h. Somatic cell count showed a similar trend, and protein content did not change steadily. Dry matter intake, body weight and body condition score were not affected by contrasting milking intervals. After resumption of TDM with conventional intervals, productions of milk, fat and protein no longer differed between the TDM groups. Milk yield of previously ODM cows remained lower by 2 kg/day (P = 0.15) in experiments 1 and 2, and by 7 kg/day (P < 0.05) in experiment 3. These results suggest that TDM at contrasting intervals up to 5 : 19 h is feasible as it decreases milk yield only moderately, especially if implemented from peak of lactation.

The motivation of cows to walk as thwarted by tethering.

Cows are often housed in tie-sheds for some part of the year (from 20 to 80% of adult cows in European countries). By contrast, regulations aiming at improving animal welfare generally provide for more opportunity to express behavior and so limit tethering (the European directive for sows). To inform current debate on whether cows should be tethered from an animal welfare point of view, 2 experiments were conducted to determine whether cows were motivated to walk (if their walking motivation was thwarted by tethering) and whether this frustration resulted in acute or chronic stress. In Exp. 1, fifteen cows were housed in tie-stalls for 1, 3, 9, or 27 d or loose-housed in a pen equipped with free-stalls for 27 d according to a Latin square design. On d 28, cows were observed in an 80-m(2) arena where they could walk or run for 10 min. In Exp. 2, fifteen cows were either loose-housed or tie-housed with or without 1 h of daily access to an exercise area according to a Latin square design (treatment duration of 27 d). On d 28, cows were observed in the test arena for 10 min as in Exp. 1. In addition, in Exp. 2, milk was sampled twice weekly for cortisol concentrations and cows underwent a chronic stress test (challenge with ACTH, followed by blood samples for cortisol concentrations). When they were tied with no access to exercise, cows displayed a greater locomotor activity in the test arena (time spent walking x 1.4 in Exp. 1, P < 0.05; time spent trotting x 5 in Exp. 2, P < 0.05), whatever the duration of tie-housing. Regular exercise caused locomotor activity in the arena test to revert to levels observed when cows were loose-housed. Basal cortisol concentrations in milk decreased with time whatever the housing condition (P < 0.001). This decrease was more marked when cows were tied than when they were loose-housed (P < 0.05). Cortisol responses to ACTH were similar between treatments. Adult cows are motivated to walk, and tethering thwarts this motivation. However, the frustration produced by tethering does not result in either acute or chronic physiological stress responses. We recommend that cows housed in tie-sheds be given regular access to an exercise area.

Once-a-day milking of Holstein and Montbéliarde cows for 7 weeks in mid-lactation.

This study aimed at comparing the effects of once-a-day (OAD) milking during the descending phase of lactation between cows from the two most common breeds in France (Holstein and Montbéliarde). This study was carried on during two successive summers on a total of 50 Holstein and 38 Montbéliarde cows. During 7 weeks, half of the cows from each breed was milked OAD while the other half was milked twice a day (TAD). The animals were also followed for the next 3 or 5 weeks when they were all milked TAD, to check for any residual effect of OAD milking. The behaviour of OAD cows was observed around milking time. The incidence of diseases, the main performance variables (milk production, milk flow rate, live weight and body condition score), the detailed composition of milk (fat, protein, lactose, somatic cells, minerals, pH, free fatty acid (FFA), nitrogen fractions and enzymes) and some technological variables (clotting time and curd firmness) were measured on all cows.Some signs of disturbance were observed in the OAD cows at the time when milking was omitted: some cows mooed, some went close to the exit of the paddock, some leaked milk prior to milking. However, these signs disappeared after 2 days. After the experimental period, the live weight and the body condition score of TAD and OAD cows did not differ significantly. OAD cows produced 4.5 kg/day less than TAD (P < 0.001), this being more marked in Holstein (5.7 kg/day, P < 0.001) than Montbéliarde (3.3 kg/day, P < 0.001) cows. The milk contents of fat, whey protein, casein, total protein and phosphorus, and its plasminogen activity, were higher with OAD cows while lactose and FFA contents, and lipoprotein lipase activity were lower, with no interaction observed with breed. During the subsequent 3 weeks, when all cows were again milked TAD, OAD cows still produced 1.7 kg/day less milk (P < 0.01) with slightly higher fat and protein content.OAD milking for 7 weeks during the descending phase of lactation decreased milk production but increased milk content of most components, with a low residual effect. Montbéliarde cows were less affected by OAD milking than Holstein cows.