Effects of grass silage and soybean meal supplementation on milk production and milk fatty acid profiles of grazing dairy cows

The effects of supplementation with grass silage and replacement of some corn in the concentrate with soybean meal (SBM) on milk production, and milk fatty acid (FA) profiles were evaluated in a replicated 4 × 4 Latin square study using 16 dairy cows grazing pasture composed of ryegrass, Kentucky bluegrass, and white clover. Each experimental period lasted for 3 wk. The 4 dietary treatments were PC, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn-based concentrate mixture (96% corn; C); PCSB, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn- and SBM-based concentrate mixture (78% corn and 18% SBM; CSB); SC, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of C concentrate; and SCSB, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of CSB concentrate. The concentrate mixtures were offered twice each day in the milking parlor and were consumed completely. Grass silage supplementation reduced dietary crude protein and concentration of total sugars, and dietary SBM inclusion increased dietary crude protein concentration and decreased dietary starch concentration. Milk yield and energy-corrected milk were increased by SBM supplementation of cows with access to grass silage. Milk protein concentration was lower in cows offered grass silage, regardless of whether SBM was fed. Dietary SBM inclusion tended to increase milk fat concentration. Plasma urea N was reduced by silage feeding and increased by SBM supplementation. Supplementation with grass silage overnight could represent a useful strategy for periods of lower pasture availability. Dietary inclusion of SBM in solely grazing cows had no effects on milk production and composition, exacerbated the inefficient capture of dietary N, and increased diet cost. Grass silage supplementation affected milk FA profiles, increasing both the FA derived from de novo synthesis and those derived from rumen microbial biomass, and decreasing the sum of C18 FA (mostly derived from diet or from mobilization of adipose tissue reserves). Milk fat concentrations of conjugated linoleic acid cis-9, trans-11, vaccenic acid (18:1 trans-11), and linolenic acid (18:3n-3) were unaffected by grass silage supplementation, suggesting that partial replacement of pasture by unwilted grass silage does not compromise the dietary quality of milk fat for humans.     

Variations in carotenoids, vitamins A and E, and color in cow's plasma and milk during late pregnancy and the first three months of lactation

The main aim of this work was to assess the effect of lactation period on the secretion of carotenoids in cow's milk. Our objective was to determine the variations in carotenoids in the plasma and milk of dairy cows from drying off to wk 12 of lactation, and to specify whether these variations depend on body stores of these micronutrients at calving. We also investigated the relationship between β-carotene (BC) and color in plasma and milk to evaluate the methods based on direct or indirect characterization of these micronutrients for traceability of feeding management. The experiment was carried out on 18 dairy cows, which were dried off 8 wk before their expected date of parturition. They were then divided into 2 homogeneous groups and fed diets contrasting in carotenoid content, high (grass silage) vs. low (corn silage), from wk -7 until parturition. From parturition through wk 12 of lactation, both groups received a grass silage-based diet. Variations in concentrations of carotenoids and the color index (CI) in plasma and milk were monitored from drying off to wk 12 of lactation. Other components of nutritional interest (i.e., vitamins A and E) were also measured. Lutein, all-trans BC and cis-13 BC were the carotenoids found in plasma and milk. Plasma concentrations of carotenoids, vitamin A, and vitamin E decreased throughout the dry period and in the first week of lactation, then increased through the first 3 mo of lactation, parallel to grass silage intake. For both groups, carotenoid and vitamin concentrations in milk drastically decreased during the first week of lactation, then did not vary significantly throughout the remainder to the experiment (wk 12). Plasma concentrations of carotenoids and vitamins were higher in the high-carotenoid group than in the low-carotenoid group during the dry period. Those differences were also observed in colostrum and disappeared in both plasma and milk during the first 10 d of the lactation period. This work allowed us to conclude that, unlike in plasma, variations in carotenoids, vitamin A, and vitamin E in milk were only slight in early lactation. In both plasma and milk, the concentrations were only transitorily affected by the nature of forage fed during the dry period, showing that they depended mainly on the dietary supply, even during the lipid mobilization period. The relationship between concentrations of BC and the CI was linear in plasma (R² = 0.51) and milk (R² = 0.37) and reached a plateau in the milk + colostrum data set (R² = 0.77). The changes in CI during the first 3 mo of lactation were not negligible compared with variations related to the nature of forage reported in previous studies. This implies that methods being developed for the traceability of feeding management of dairy cows based on direct or indirect characterization of these micronutrients in milk, plasma, or both will need to account for changes in relation to lactation stage, which requires further investigation.     

Potentials to differentiate milk composition by different feeding strategies

To investigate the effect of the dietary intake of the cow on milk composition, bulk-tank milk was collected on 5 occasions from conventional (n = 15) and organic (n = 10) farms in Denmark and on 4 occasions from low-input nonorganic farms in the United Kingdom, along with management and production parameters. Production of milk based on feeding a high intake of cereals, pasture, and grass silage resulted in milk with a high concentration of α-linolenic acid (9.4 ± 0.2 mg/kg of fatty acids), polyunsaturated fatty acids (3.66 ± 0.07 mg/kg of fatty acids), and natural stereoisomer of α-tocopherol (RRR-α-tocopherol, 18.6 ± 0.5 mg/kg of milk fat). A milk production system using a high proportion of maize silage, by-products, and commercial concentrate mix was associated with milk with high concentrations of linoleic acid (LA; 19.7 ± 0.4 g/kg of fatty acids), monounsaturated fatty acids (27.5 ± 0.3 mg/kg of fatty acids), and a high ratio between LA and α-linolenic acid (4.7 ± 0.2). Comparing these 2 production systems with a very extensive nonorganic milk production system relying on pasture as almost the sole feed (95 ± 4% dry matter intake), it was found that the concentrations of conjugated LA (cis-9,trans-11; 17.5 ± 0.7 g/kg of fatty acids), trans-11-vaccenic acid (37 ± 2 g/kg of fatty acids), and monounsaturated fatty acids (30.4 ± 0.6 g/kg of fatty acids) were higher in the extensively produced milk together with the concentration of antioxidants; total α-tocopherol (32.0 ± 0.8 mg/kg of milk fat), RRR-α-tocopherol (30.2 ± 0.8 mg/kg of milk fat), and β-carotene (9.3 ± 0.5 mg/kg of milk fat) compared with the organic and conventional milk. Moreover, the concentration of LA (9.2 ± 0.7 g/kg of fatty acids) in milk from the extensive milk production system was found to approach the recommended unity ratio between n-6 and n-3, although extensive milk production also resulted in a lower daily milk yield.     

Comparative evaluation of alternative forages to grass silage in the diet of early lactation dairy cows

Fifty-six autumn-calving Holstein-Friesian cows, blocked on the basis of days in milk (27.6 ± 10.65 d), lactation number (3.1 ± 2.21), and preexperimental milk yield (28.4 ± 6.69 kg) were used to examine the effects of replacing 330 g/kg of dry matter (DM) of first-cut perennial ryegrass silage with either fermented whole-crop wheat (WCW), urea-treated processed WCW, or corn silage on subsequent feed intake, milk production, and efficiency of nitrogen utilization. The DM (g/kg), crude protein (CP, g/kg of DM) and in vitro DM digestibility (g/kg) of the forages were 204, 179, and 762 for grass silage; 389, 90, and 711 for fermented WCW; 795, 141, and 768 for urea-treated processed WCW; and 346, 93, and 783 for corn silage, respectively. Four forage treatments were evaluated as follows: 1) grass silage as the sole forage (GS); 2) a mixture of grass silage and fermented WCW silage, (F-WCW); 3) a mixture of grass silage and urea-treated processed WCW, (UP-WCW); and 4) a mixture of grass silage and corn silage (CS). In all cases, the alternative forages comprised 67% of the forage mix on a DM basis. Isonitrogenous diets were formulated by offering all cows 8 kg of concentrate as fed, formulated to different CP concentrations. Cows were offered these diets from 28 to 104 d in milk. Total DM intake and milk yield were greater on UP-WCW (20.0 and 30.2 kg/d) and CS (18.3 and 33.2 kg/d) than on GS (13.5 and 26.5 kg/d). Although DM intake was greater on F-WCW (17.1 kg/d) than on GS, milk yield was not significantly greater (+2.7 kg/d). Milk protein concentration was greater on F-WCW (30.5 g/kg), UP-WCW (31.3 g/kg), and CS (30.7 g/kg) than on GS (28.5 g/kg). However, there was no difference between treatments in milk fat or lactose concentrations. Body weight change was greater for cows offered GS (−0.27 kg/d) than for those offered UP-WCW (−0.01 kg/d) and CS (+0.05 kg/d) but not compared with those offered F-WCW (−0.06 kg/d). There was no effect of treatment on plasma glucose, nonesterified fatty acids, β-hydroxybutyrate, urea, or total protein at d 64 ± 17.4 and d 92 ± 17.4 postpartum. Efficiency of N utilization was greatest for CS with 0.36 of N intake being recovered in milk compared with 0.28, 0.32, and 0.26 for GS, F-WCW, and UP-WCW, respectively. There was no effect of treatment on milk urea N concentration or the urinary allantoin N to creatinine N ratio. The results of this experiment indicate that corn silage is a more suitable supplementary forage to grass silage than fermented or urea-treated processed WCW, with advantages realized in milk production and more efficient N utilization.     

Variations in carotenoids, vitamins A and E, and color in cow's plasma and milk following a shift from hay diet to diets containing increasing levels of carotenoids and vitamin E

This experiment was conducted to determine the variations in carotenoid, vitamins A and E concentrations, and color in the plasma and milk of dairy cows following a shift from a hay diet to diets containing increasing levels of carotenoids and vitamin E. This study was performed on 32 multiparous Montbéliarde dairy cows in midlactation. After a 6-wk preexperimental period on a diet based on hay and concentrates, the cows were allocated to 4 homogeneous groups, and thereafter fed for 6 wk on isoenergetic experimental diets where the hay was replaced by an experimental feed rich in carotenoids and vitamin E, consisting in 75% grass silage and 25% alfalfa protein concentrate (PX Agro Super Desialis, Châlons en Champagne, France). The hay-to-experimental feed ratios were 100/0 in group 1, 67/33 in group 2, 33/67 in group 3, and 0/100 in group 4, providing 1.6, 3.6, 5.4, and 7.4 g/d of total carotenoids, respectively. Variations in carotenoid, vitamins A and E concentrations as well as variations in color index (CI) were monitored from d −7 through to d 42 on the experimental diets. Zeaxanthin, lutein, 13-cis-β-carotene, and all-trans-β-carotene accounted for an average 3, 10, 9, and 78%, respectively, of total carotenoids in plasma and 0, 17, 12, and 71%, respectively, of total carotenoids in milk. The switch from preexperimental to experimental diets only slightly affected zeaxanthin, lutein, and vitamin A concentrations in plasma and milk. A rapid increase in vitamin E and β-carotene (BC) was observed during the first week in both plasma and milk. For vitamin E, the time to reach a plateau was from 8 d (group 2) to 28 d (group 4) in plasma, and 5 d (groups 2-4) in milk. Plasma concentrations of BC had stabilized after 28 d in group 2 but were not stabilized after 42 d in groups 3 and 4, whereas milk concentrations of BC plateaued from d 21 in group 2 and d 28 in groups 3 and 4. At the end of the experimental period, BC and vitamin E concentrations in plasma and vitamin E concentrations in milk fat were linearly related to the proportion of experimental feed in the diet. In contrast, BC concentrations in milk fat did not differ between groups 2, 3, and 4, reflecting saturation at high levels of carotenoid intake (i.e., when plasma BC exceeded 5 μg/mL). These results suggested that under high-carotenoid diets, milk secretion of BC is not limited by the amount of plasma BC arriving to the mammary gland but by mechanisms involved in the BC transfer from plasma to milk. These mechanisms will need to be investigated. The BC concentrations were responsible for more than 80% of CI variations in plasma and 56% of CI variations in milk, where there was wide variability among individuals. Plasma CI appeared to be a more promising tool than milk CI as an indicator of the carotene content of the diets ingested by dairy cows.     

Effect of safflower oil, flaxseed oil, monensin, and vitamin E on concentration of conjugated linoleic acid in bovine milk fat

Conjugated linoleic acid (CLA) refers to a mixture of conjugated octadecadienoic acids of predominantly ruminant origin. The main isomer in bovine milk fat is the cis-9, trans-11 CLA. Interest in CLA increased after the discovery of its health-promoting properties, including potent anticarcinogenic activity. Two experiments were conducted to evaluate dietary strategies aimed at increasing the concentration of CLA in bovine milk fat. Both experiments were organized as a randomized complete block design with a repeated measures treatment structure. In Experiment 1, 28 Holstein cows received either a control diet or one of 3 treatments for a period of 2 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a dry matter (DM) basis, fed as a total mixed ration (TMR). The concentrate was partially replaced in the treatment groups with 24 ppm of monensin (MON), 6% of DM safflower oil (SAFF), or 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M). Average cis-9, trans-11 CLA levels in milk fat after 2 wk of feeding were 0.45, 0.52, 3.36, and 5.15% of total fatty acids for control, MON, SAFF, and SAFF/M, respectively. In Experiment 2, 62 Holstein cows received either a control diet or one of 5 treatment diets for a period of 9 wk. The control diet consisted of 60% forage (barley silage, alfalfa silage, and alfalfa hay) and 40% concentrate on a DM basis, fed as a TMR. The concentrate was partially replaced in the treatment groups with 6% of DM safflower oil (SAFF), 6% of DM safflower oil plus 150 IU of vitamin E/kg of DM (SAFF/E), 6% of DM safflower oil plus 24 ppm of monensin (SAFF/M), 6% of DM safflower oil plus 24 ppm of monensin plus 150 IU of vitamin E/kg of DM (SAFF/ME), or 6% of DM flaxseed oil plus 150 IU of vitamin E/kg of DM (FLAX/E). Average cis-9, trans-11 CLA levels during the treatment period were 0.68, 4.12, 3.48, 4.55, 4.75, and 2.80% of total fatty acids for control, SAFF, SAFF/E, SAFF/M, SAFF/ME, and FLAX/E, respectively. The combination of safflower oil with monensin was particularly effective at increasing milk fat CLA. The addition of vitamin E to the diet partially prevented the depression in milk fat associated with oilseed feeding, but had no significant effect on the concentration of CLA in milk.     

Variations in carotenoids, fat-soluble micronutrients, and color in cows' plasma and milk following changes in forage and feeding level

The main aim of this work was to assess factors affecting the secretion of carotenoids in cows’ milk. Our objectives were 1) to determine the kinetics of the decrease in carotenoids in plasma, milk, and adipose tissues following a switch from a high- to a low- carotenoid diet; and 2) to specify whether, during lipomobilization, the restitution of these compounds stored in the adipose tissues is sufficient to modify their secretion in milk. During the preexperimental period, 32 cows in midlactation were fed a grass silage-based diet, and were then assigned to 4 groups; 2 groups were maintained on the grass silage diet and 2 were switched to a late hay diet. For each forage diet, one group was fed according to net energy for lactation and nitrogen requirements, and the other was submitted to an energetic underfeeding, with similar forage and carotenoid intake between groups. Variations in concentration of carotenoids and color index (CI) of plasma and milk were monitored over 8 wk. Other components of nutritional interest; i.e., vitamin E (VE), vitamin A, and fatty acids, were also measured. The switch from grass silage to hay diet induced a rapid decrease in concentration of βl-carotene (BC) and VE and in the CI of plasma and milk during the first 2 wk. Pools of BC in adipose tissues also decreased by 40%. Concentrations of BC at the end of the experiment for silage and hay groups were 5.10 and 1.71 μg/mL in plasma and 0.17 and 0.07 μg/mL in milk, respectively. The energetic underfeeding did not affect BC concentration in plasma and induced a small increase in milk BC concentration, related to a decreased milk yield. In the silage group, the energetic underfeeding after 3 to 4 wk induced a decrease in CI and VE of plasma, but not of milk. The fatty acid profile in milk was modified by the change from grass silage to hay diet (C10 to C14 and linoleic acid increased; stearic and linolenic acid percentages decreased) and by underfeeding (oleic, vaccenic, and rumenic acid percentages increased). This study shows that BC and VE levels persist in midlactation cows’ plasma and milk for about 2 wk. The results could not confirm a release of BC by bovine adipose tissue, but the level of underfeeding was moderate in this trial. The concentration of BC explained 58 and 40% of variation in CI of plasma and milk, respectively. These CI appear to be valuable tools for diet traceability (i.e., silage vs. hay).     

Effects of microbial inoculants on corn silage fermentation, microbial contents, aerobic stability, and milk production under field conditions

The present study aimed to investigate the effects of 2 corn silage inoculation strategies (homofermentative vs. heterofermentative inoculation) under field conditions and to monitor responses in silage variables over the feeding season from January to August. Thirty-nine commercial dairy farms participated in the study. Farms were randomly assigned to 1 of 3 treatments: control (nonactive carrier; Chr. Hansen A/S, Hørsholm, Denmark), Lactisil (inoculation with 1 × 10⁵Lactobacillus pentosus and 2.5 × 10⁴Pediococcus pentosaceus per gram of fresh matter; Chr. Hansen A/S), and Lalsil Fresh (inoculation with 3 × 10⁵Lactobacillus buchneri NCIMB 40788 per gram of fresh matter; Lallemand Animal Nutrition, Blagnac, France). Inoculation with Lactisil had no effects on fermentation variables and aerobic stability. On the contrary, inoculation with Lalsil Fresh doubled the aerobic stability: 37, 38, and 80 ± 8 h for control, Lactisil, and Lalsil Fresh, respectively. The effect of Lalsil Fresh on aerobic stability tended to differ between sampling times, indicating a reduced difference between treatments in samples collected in April. Lalsil Fresh inoculation increased silage pH and contents of acetic acid, propionic acid, propanol, propyl acetate, 2-butanol, propylene glycol, ammonia, and free AA. The contents and ratios of dl-lactic acid, l-lactic acid relative to dl-lactic acid, free glucose, and dl-lactic acid relative to acetic acid decreased with Lalsil Fresh inoculation. Lalsil Fresh inoculation increased the silage counts of total lactic acid bacteria and reduced yeast counts. The Fusarium toxins deoxynivalenol, nivalenol, and zearalenone were detected in all silages at all collections, but the contents were not affected by ensiling time or by inoculation treatment. The effect of inoculation treatments on milk production was assessed by collecting test-day results from the involved farms and comparing the actual milk production with predicted milk production within farm based on test-day results from 2007 and 2008. The average milk production of lactating cows at test days during the study (January to September 2009) was 30.7 ± 0.5 kg of energy-corrected milk/d. Milk production was 104.6 ± 0.7% of the predicted yield and did not differ among treatments. In conclusion, the present study showed that homofermentative inoculants might not compete efficiently or might not deviate sufficiently from the epiphytic flora on whole-crop corn to affect fermentation in standard qualities of corn silage. Heterofermentative inoculation increased aerobic stability and numerous fermentation variables. None of the treatments affected milk production, and more-stable corn silage seemed to have a similar production value as compared with less-stable homofermented silage. Heterofermented silage can be evaluated for its properties to limit aerobic silage deterioration in the feed chain.     

The scavenging capacity and synergistic effects of lycopene, vitamin E, vitamin C, and β-carotene mixtures on the DPPH free radical

The biological activity of lycopene can be enhanced by the presence of these other active antioxidants such as β-carotene, vitamin E, and vitamin C. Since many of these natural antioxidants are consumed together in foods, the potential for synergistic interactions is high in the human diet. The aim of this study was to determine what concentrations and combinations of antioxidants among lycopene, vitamin E, vitamin C, and β-carotene are capable of producing synergistic antioxidant effects, based on tomato-based food products. Solutions of the scavenging capacities of lycopene, vitamin E, vitamin C, and β-carotene, alone and in different combinations were measured using the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Three different levels of each antioxidant were used. A comparison of the scavenging capacity (antioxidant activity) of the combinations of antioxidants to the arithmetic sum of the scavenging capacities of the individual antioxidants was used to calculate the synergistic effects (SEs) between the antioxidants. The results showed that the mixture that had the highest SEs (P<0.01) was the solution combining lycopene (15 μmol/L), vitamin E (5.0 μmol/L), vitamin C (0.16 μmol/L), and β-carotene (10.83 μmol/L). The results suggest that the antioxidant property of this combination was substantially superior to the sum of the individual antioxidant effects, and these interactions can enhance the antioxidant effectiveness of natural antioxidants. The results could guide in the formulation and development of functional food products that have high antioxidant potential.     

Aerobic bacterial, coliform, Escherichia coli and Staphylococcus aureus counts of raw and processed milk from selected smallholder dairy farms of Zimbabwe

A cross sectional study was conducted to enumerate total viable bacteria (TBC), coliforms, Escherichia coli and Staphylococcus aureus in raw (n = 120) and processed (n = 20) milk from individual farms from three smallholder dairy schemes of Zimbabwe between October, 2009 and February, 2010. Data on management factors were collected using a structured questionnaire. A standard pour plate technique was used to enumerate total viable bacteria, while for coliforms, E. coli and S. aureus, counts were assessed by the spread plate technique. The association of total viable bacterial counts and management factors was assessed using univariable and a linear regression model. The log₁₀ TBC for raw milk differed significantly (P < 0.05) amongst the schemes with the lowest (5.6 ± 4.7 log₁₀ cfu/ml) and highest (6.7 ± 5.8 log₁₀ cfu/ml) recorded from Marirangwe and Nharira respectively. The mean log₁₀ of TBC of processed milk (6.6 ± 6.0 log₁₀ cfu/ml) were marginally higher than those of raw milk (6.4 ± 5.6 log₁₀ cfu/ml) but not significant (P > 0.05). The coliform, E. coli and S. aureus counts for raw milk significantly differed (P < 0.05) amongst the study areas. The variation in TBC, coliforms, E. coli and S. aureus counts amongst the schemes could be attributed to differences in milking hygiene where farms with more access to training and monitoring of microbiological quality of milk had lower counts. Linear regression analysis revealed dairy scheme, delivery time and season of milking as independently associated with increased TBC of raw milk. The high TBC of raw and processed milk generally indicated low levels of milking hygienic practices, and high level of post-processing contamination, respectively. The high TBC, coliform, E. coli and S. aureus counts of both raw and processed milk may present a public health hazard. Thus, educating the farmers on general hygienic practices, quickening the delivery of milk to collection centres, or availing cooling facilities on-farm will improve the microbiological quality and safety of milk.     

Effects of corn silage particle length and forage:concentrate ratio on milk fatty acid composition in dairy cows fed supplemental flaxseed

This study aimed to evaluate the effects of length of chop of corn silage and forage:concentrate ratio (F:C) on performance and milk fatty acid profiles in dairy cows supplemented with flaxseed. Our hypothesis was that decreasing forage particle length and F:C ratio would increase unsaturated fatty acid flow to the small intestine and subsequent transfer of these unsaturated fatty acids into milk. Eight Holstein cows (648.1 ± 71.5 kg body weight; 109.6 ± 43.6 days in milk) were used in a replicated 4 × 4 Latin square design with 21-d periods and a 2 × 2 factorial arrangement of dietary treatments. Dietary factors were: 1) F:C ratios (dry matter basis) of 55:45 and 45:55; and 2) corn silage particle lengths of 9.52 and 19.05 mm. All experimental cows received 1 kg of flaxseed to substitute for 1 kg of a rolled barley grain-based concentrate daily. Diets were fed twice daily as a total mixed ration. Corn silage particle length and F:C ratio had no effect on dry matter intake, milk yield, and milk composition; however, feeding short cut corn silage depressed milk protein yield. Significant particle size × F:C ratio interactions were observed for milk fat proportions of C_16:0, C_18:1cis-9, and C_18:2cis-9, trans-11 (a conjugated linoleic acid isomer). At short corn silage particle size, decreasing F:C ratio depressed milk fat proportion of C_16:0. Conversely, feeding short corn silage at high F:C ratio increased the proportion of C_18:1cis-9 and C_18:2cis-9, trans-11 in milk fat. The milk fat proportion of C_18:2trans-10, cis-12, a conjugated linoleic acid isomer that is associated with milk fat depression, was not affected by dietary treatment. Our results show that corn silage particle length and F:C ratio influence milk fatty acid profiles in dairy cows fed supplemental flaxseed as a source of polyunsaturated fatty acids.     

Minimizing the level of Bacillus cereus spores in farm tank milk

In a year-long survey on 24 Dutch farms, Bacillus cereus spore concentrations were measured in farm tank milk (FTM), feces, bedding material, mixed grass and corn silage, and soil from the pasture. The aim of this study was to determine, in practice, factors affecting the concentration of B. cereus spores in FTM throughout the year. In addition, the results of the survey were used in combination with a previously published modeling study to determine requirements for a strategy to control B. cereus spore concentrations in FTM below the MSL of 3 log₁₀ spores/L. The B. cereus spore concentration in FTM was 1.2 ± 0.05 log₁₀ spores/L and in none of samples was the concentration above the MSL. The spore concentration in soil (4.9 ± 0.04 log₁₀ spores/g) was more than 100-fold higher than the concentration in feces (2.2 ± 0.05 log₁₀ spores/g), bedding material (2.8 ± 0.07 log₁₀ spores/g), and mixed silage (2.4 ± 0.07 log₁₀ spores/g). The spore concentration in FTM increased between July and September compared with the rest of the year (0.5 ± 0.02 log₁₀ spores/L difference). In this period, comparable increases of the concentrations in feces (0.4 ± 0.03 log₁₀ spores/g), bedding material (0.5 ± 0.05 log₁₀ spores/g), and mixed silage (0.4 ± 0.05 log₁₀ spores/g) were found. The increased B. cereus spore concentration in FTM was not related to the grazing of cows. Significant correlations were found between the spore concentrations in FTM and feces (r = 0.51) and in feces and mixed silage (r = 0.43) when the cows grazed. The increased concentrations during summer could be explained by an increased growth of B. cereus due to the higher temperatures. We concluded that year-round B. cereus spores were predominantly transmitted from feeds, via feces, to FTM. Farmers should take measures that minimize the transmission of spores via this route by ensuring low initial contamination levels in the feeds (<3 log₁₀ spores/g) and by preventing growth of B. cereus in the farm environment. In addition, because of the extremely high B. cereus spore concentrations in soil, the contamination of teats with soil needs to be prevented.     

Evaluation of nitrogen utilization and the effects of monensin in dairy cows fed brown midrib corn silage

Twenty midlactation Holstein cows (4 ruminally fistulated) averaging 101 ± 34 d in milk and weighing 674 ± 77 kg were used to compare rations with brown midrib corn silage (bm3) to rations with dual-purpose control silage (DP) on N utilization and milk production. The effect of monensin in these rations was also examined. Animals were assigned to one of five 4 × 4 Latin squares with treatments arranged in a 2 × 2 factorial. Cows were fed 1 of 4 treatments during each of the four 28-d periods. Treatments were 1) 0 mg/d monensin and bm3 corn silage, 2) 0 mg/d monensin and DP corn silage, 3) 300 mg/d monensin and bm3 corn silage, and 4) 300 mg/d monensin and DP corn silage. In vitro 30-h neutral detergent fiber (NDF) digestibility was greater for bm3 corn silage (61.0 vs. 49.1 ± 0.62). Dry matter intake (DMI) tended to be greater for cows consuming bm3 corn silage (21.3 vs. 20.2 kg/d). Neither hybrid nor monensin affected milk production, fat, or protein (37.7 kg, 3.60%, or 3.04%). Monensin tended to increase rumen pH (5.89 vs. 5.79 ± 0.07) compared with the control treatment. In addition, bm3 corn silage resulted in a significant decrease in rumen pH (5.72 vs. 5.98 ± 0.07). Supplementing monensin had no effect on molar proportions of acetate, propionate, or butyrate. In contrast, an increase was observed in branched-chain volatile fatty acids. No treatment interactions were observed for rumen pH or molar proportion of propionate but monensin decreased the molar proportion of acetate and increased the molar proportion of butyrate when cattle consumed bm3 silage. Dry matter, N, and acid detergent fiber digestibility were lower for the bm3 ration, whereas NDF digestibility was not different between treatments. There was no effect of hybrid on microbial protein synthesis (1,140 g/d) as estimated by urinary concentration of purine derivatives. Cows consuming bm3 excreted more fecal N than cows consuming DP (38.2 vs. 34.4% N intake); however, based on spot sampling, estimated urinary and manure N were not different between treatments (35.8 and 71.9% N intake). Monensin had no effect on DMI, digestibility of any nutrients, or N metabolism, and there were no hybrid by monensin interactions. Rations including bm3 corn silage tended to increase DMI but did not affect production. The reduction in the digestibility of some nutrients when cows consumed bm3 may have been caused by increased DMI and possible increased digestion in the lower gut. This increase in DMI appeared to also have negatively affected N digestibility but not NDF digestibility. This resulted in a greater amount of N excreted in feces but did not affect total mass of manure N.     

Plasma paraoxonase, health, inflammatory conditions, and liver function in transition dairy cows

Paraoxonase (PON) is a liver protein with hydrolase activity that is released into the blood stream. Paraoxonase may serve as an index of liver function because it is drastically reduced in chronic liver damage. Sixty-seven periparturient dairy cows were used to evaluate the relationship between plasma PON, health problems, inflammatory conditions, and liver function. Baseline plasma PON concentrations during the first 30 d in milk (DIM) were retrospectively used to group cows into quartiles. Metabolic profile, lipid metabolites (e.g., nonesterified fatty acids, β-hydroxybutyrate), inflammatory indices (haptoglobin, ceruloplasmin), low and high density lipoprotein cholesterol, vitamin A, vitamin E, reactive oxygen metabolites, total antioxidants, and PON in plasma were measured 2 wk before to 8 wk after calving. Weekly milk yield, body condition score, and all health problems were recorded. After parturition (7 DIM), cows in the lower PON group had the lowest plasma concentrations of negative acute phase proteins compared with the higher PON group for retinol binding protein (23.2 ± 2.86 vs. 36.0 ± 2.96 μg/dL of vitamin A), albumin (31.6 ± 0.73 vs. 33.9 ± 0.75 g/ L), total cholesterol (2.04 ± 0.30 vs. 2.45 ± 0.42 mmol/ L), and the highest concentrations of haptoglobin (0.67 vs. 0.24 ± 0.03 g/L; positive acute phase protein) and globulins (37.2 vs. 32.3 ± 1.4 g/L). Plasma bilirubin was highest in the cows (10.1 vs. 6.2 ± 0.6 μmol/L) in the lowest PON quartile. Plasma PON was negatively correlated with haptoglobin (r = −0.39) and bilirubin (r = −0.42) and positively correlated with retinol binding protein (r = 0.54), albumin (r = 0.38), and cholesterol (r = 0.55) fractions. A total of 82.3% of cows in the lower quartile and no cows in the upper quartile experienced serious inflammation. Lower quartile cows produced 28.1 ± 10.3 kg of milk/d; whereas upper quartile cows produced 38.3 ± 7.7 kg of milk/d during the first 30 DIM. A reduction in the ability of the liver to cope with the increased metabolic demand near parturition in dairy cows can be diagnosed using changes in baseline plasma PON.     

Performance of dairy cows fed silage and grain produced from second-generation insect-protected (Bacillus thuringiensis) corn (MON 89034), compared with parental line corn or reference corn

Corn grain and corn silage are major feed components in lactating dairy cow rations. Bacillus thuringiensis (B.t.) is a naturally occurring soil bacterium that produces a protein that is toxic to lepidopteran insects that may damage plant tissues and reduce corn quality and yields. During each of the four 28-d periods, cows were offered 1 of 4 rations in which the corn grain and silage originated from different corn hybrids: a nontransgenic corn control (from hybrid DKC63-78; Monsanto Co., St. Louis, MO), a B.t. test substance corn (MON 89034 in hybrid DKC63-78; Monsanto Co.), and 2 commercial nontransgenic reference (Ref) hybrids: DKC61-42 (Ref 1) and DKC62-30 (Ref 2; Monsanto Co.). Sixteen multiparous Holstein cows averaging 110 ± 21 d in milk and weighing 684 ± 62.3 kg were blocked by days in milk and milk yield and randomly assigned to one of four 4 × 4 Latin squares. Diets were formulated to contain 36.4% corn silage and 16.3% corn grain. Dry matter intake was greater for cows consuming B.t. corn (26.6 ± 0.59 kg/d) compared with the control, Ref 1, and Ref 2 corn diets (25.4, 25.0, and 25.6 ± 0.59 kg/d, respectively). Milk yield, fat yield, and percentage of fat (36.8 ± 0.98 kg/d, 1.22 ± 0.05 kg/d, and 3.3 ± 0.10%), milk protein yield and percentage of protein (1.11 ± 0.03 kg/d and 3.01 ± 0.05%), milk urea nitrogen concentration (14.01 ± 0.49 mg/dL), and 3.5% fat-corrected milk yield (35.7 ± 1.07 kg/d) were not different across treatments. The results from this study show that lactating dairy cows that consume B.t. corn (MON 89034) do not differ from lactating dairy cows that consume nontransgenic corn in milk yield, 3.5% fat-corrected milk per unit of dry matter intake, or milk components.     

Fatty acid intake and milk fatty acid composition of Holstein dairy cows under different grazing strategies: Herbage mass and daily herbage allowance

The objective of this study was to investigate the effect of level of 1) pregrazing herbage mass (HM) and 2) level of daily herbage allowance (DHA) on the performance and fatty acid (FA) composition of milk from grazing dairy cows. Sixty-eight Holstein-Friesian dairy cows were allocated to either a high or low pregrazing HM (1,700 vs. 2,400 kg of DM/ha; >40 mm), and within HM treatment, cows were further allocated to either a high or low DHA (16 vs. 20 kg of DM/d per cow; >40 mm) in a 2 × 2 factorial design. Pregrazing HM did not affect dry matter intake (17.5 ± 0.75 kg/d), milk production (22.1 ± 0.99 kg/d), milk composition (milk fat, 3.88 ± 0.114%; milk protein, 3.28 ± 0.051%), body weight (525 ± 16 kg), or body condition score (2.65 ± 0.064). Increasing DHA increased dry matter intake (+1.5 kg/d) but did not affect any other variable measured. Cows grazing the low HM or high DHA had a higher daily intake of total FA (+0.12 and +0.09 kg/d, respectively, for the low HM and high DHA), α-linolenic acid (LNA; +0.08 and +0.05 kg/d, respectively, for the low HM and high DHA), and linoleic acid (+0.01 for both the low HM and high DHA) compared with either the high HM or low DHA. Milk conjugated linoleic acid (cis-9, trans-11 isomer) was not affected by treatment (13.0 ± 0.77 g/kg of total FA); however, large variation was recorded between individual animals (range from 5.9 to 20.6 g/kg of total FA). Milk concentrations of LNA were higher for animals offered the low HM (5.3 g/kg of total FA), but across treatments, milk concentrations of LNA were low (4.9 ± 0.33 g/kg of total FA). The present study indicates that changes in HM and DHA do not have a great effect on the milk FA composition of grazing dairy cows. Further enhancement of the beneficial FA content in milk purely from changes in grazing strategy may be difficult when pasture quality is already high.     

Evaluation of hippuric acid content in goat milk as a marker of feeding regimen

Organic producers, traders, and consumers must address 2 issues related to milk: authentication of the production system and nutritional differentiation. The presence of hippuric acid (HA) in goat milk samples has been proposed as a possible marker to differentiate the feeding regimen of goats. The objective of this work is to check the hypothesis that HA could be a marker for the type of feeding regimen of goats by studying the influence of production system (conventional or organic) and feeding regimen (with or without grazing fodder). With this purpose, commercial cow and goat milk samples (n = 27) and raw goat milk samples (n = 185; collected from different breeds, localizations, and dates) were analyzed. Samples were grouped according to breed, feeding regimen, production system, and origin to compare HA content by ANOVA and honestly significant difference Tukey test at a confidence level of ≥95%. Hippuric acid content was obtained by analyzing milk samples with capillary electrophoresis. This method was validated by analyzing part of the samples with HPLC as a reference technique. Sixty-nine raw goat milk samples (of the total 158 samples analyzed in this work) were quantified by capillary electrophoresis. In these samples, the lowest average content for HA was 7 ± 3 mg/L. This value corresponds to a group of conventional raw milk samples from goats fed with compound feed. The highest value of this group was 28 ± 10 mg/L, corresponding to goats fed compound feed plus grass. Conversely, for organic raw goat milk samples, the highest concentration was 67 ± 14 mg/L, which corresponds to goats fed grass. By contrast, the lowest value of this organic group was 26 ± 10 mg/L, which belongs to goats fed organic compounds. Notice that the highest HA average content was found in samples from grazing animals corresponding to the organic group. This result suggests that HA is a good marker to determine the type of goats feeding regimen; a high content of HA represents a diet based mainly or exclusively on eating green grass (grazing), independently of the production system. Hence, this marker would not be useful for the actual organic policies to distinguish organic milk under the current regulations, because organic dairy ruminants can be fed organic compound feed and conserved fodder without grazing at all.     

Characterisation,extraction efficiency,stability and antioxidant activity of phytonutrients in Angelica keiskei

Phytonutrients in Angelica keiskei, a dark green leafy vegetable, were characterised and their extraction efficiency by different compositions of water/ethanol as well as stability at different temperatures was determined. A range in the content of lutein (205–265 mg/kg dry wt), trans-β-carotene (103–130 mg/kg dry wt), and total phenols (8.6–9.7 g/kg) was observed amongst Angelica keiskei grown in three different conditions. LC-ESI-MS/MS analysis identified chlorogenic acid, chalcones and the glucosides of luteolin and quercetin as the major phenolic compounds in Angelica keiskei. Only 46% of lutein was extracted by 70% of ethanol and no carotenoid was detected in 40% ethanol and 100% water extracts of Angelica keiskei. Major phytonutrients in Angelica keiskei were stable at −80 °C up to 12 months whilst β-carotene was significantly degraded at room temperature and 4 °C within 2 months and lutein at room temperature within 12 months.     

Assessment of dietary ratios of red clover and grass silages on milk production and milk quality in dairy cows

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 4 × 4 Latin square changeover design experiment to test the effects of changing from ryegrass (Lolium perenne) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, milk organoleptic qualities, and whole-body nitrogen partitioning. Four dietary treatments, comprising ad libitum access to 1 of 4 forage mixtures plus a standard allowance of 4 kg/d dairy concentrates, were offered. The 4 forage mixtures were, on a dry matter (DM) basis: 1) 100% grass silage, 2) 66% grass silage: 34% red clover silage, 3) 34% grass silage: 66% red clover silage, and 4) 100% red clover silage. In each of 4 experimental periods, there were 21 d for adaptation to diets and 7 d for measurements. There was an increase in both DM intakes and milk yields as the proportion of red clover in the diet increased. However, the increase in milk yield was not as great as the increase in DM intake, so that the efficiency of milk production, in terms of yield (kg) of milk per kg of DM intake, decreased. The concentrations of protein, milk fat, and the shorter chain saturated fatty acids decreased, whereas C18 polyunsaturated fatty acids (PUFA) and long-chain PUFA (C20+) increased as the proportion of red clover in the diet increased. There was little effect of dietary treatment on the organoleptic qualities of milk as assessed by taste panel analysis. There were no effects on the aroma of milk, on aftertaste, or overall liking of the milk. Milk was thicker and creamier in color when cows were fed grass silage compared with red clover silage. The flavor of milk was largely unaffected by dietary treatment. In conclusion, increasing the proportion of red clover in the diet of dairy cows increased feed intakes and milk yields, decreased the concentration of fat and protein in milk, increased PUFA for healthiness, and had little effect on milk organoleptic characteristics.     

Effect of pregrazing herbage mass on methane production, dry matter intake, and milk production of grazing dairy cows during the mid-season period

Increasing milk production from pasture while increasing grass dry matter intake (GDMI) and lowering methane (CH₄) emissions are key objectives of low-cost dairy production systems. It was hypothesized that offering swards of low herbage mass with increased digestibility leads to increased milk output. A grazing experiment was undertaken to investigate the effects of varying levels of HM on CH₄ emissions, GDMI and milk production of grazing dairy cows during the mid-season grazing period (June to July). Prior to the experiment, 46 Holstein-Friesian dairy cows (46 d in milk) were randomly assigned to 1 of 2 treatments (n = 23) in a randomized block design. The 2 treatments consisted of 2 target pregrazing HM: 1,000 kg of dry matter (DM)/ha (low herbage mass, LHM) or 2,200 kg of DM/ha (high herbage mass, HHM). The experimental period lasted 2 mo from June 1 until July 31. Within the experimental period, there were 2 measurement periods, measurement 1 (M1) and measurement 2 (M2), where CH₄ emissions, GDMI, and milk production were measured. Mean herbage mass throughout the measurement periods was 1,075 kg of DM/ha and 1,993 kg of DM/ha for the LHM and HHM treatments, respectively. Grass quality in terms of organic matter digestibility was significantly higher for the LHM treatment in M2 (+12 g/kg of DM). In M1, the effect of herbage mass on grass quality was approaching significance in favor of the LHM treatment. Herbage mass did not significantly affect milk production during the measurement periods. Cows grazing the LHM swards had increased GDMI in M1 (+1.5 kg of DM) compared with cows grazing the HHM swards; no difference in GDMI was observed in M2. Grazing HHM swards increased CH₄ production per cow per day (+42 g), per kilogram of milk yield (+3.5 g/kg of milk), per kilogram of milk solids (+47 g/kg of milk solids), and per kilogram of GDMI (+3.1 g/kg of GDMI) in M2. Cows grazing the HHM swards lost a greater proportion of their gross energy intake as CH₄ during both measurement periods (+0.9% and +1% for M1 and M2, respectively). It was concluded that grazing LHM swards would increase grass quality with a concurrent reduction in CH₄ emissions.