Rumen biohydrogenation-derived fatty acids in milk fat from grazing dairy cows supplemented with rapeseed, sunflower, or linseed oils

The effects of supplementation with rapeseed, sunflower, and linseed oils (0.5 kg/d; good sources of oleic, linoleic, and linolenic acids, respectively) on milk responses and milk fat fatty acid (FA) profile, with special emphasis on rumen-derived biohydrogenation intermediates (BI), were evaluated in a replicated 4 × 4 Latin square study using 16 grazing dairy cows. The dietary treatments were 1) control diet: 20-h access to grazing pasture supplemented with 5 kg/d of corn-based concentrate mixture (96% corn; CC); 2) RO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of rapeseed oil; 3) SO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of sunflower oil; and 4) LO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of linseed oil. Milk fatty acids were converted to methyl esters and analyzed by gas-liquid chromatography and silver-ion HPLC. Dietary treatments had no effect on milk production or on milk protein content and milk protein production. Supplementation with rapeseed and sunflower oils lowered milk fat content and milk fat production, but linseed oil had no effect. Inclusion of dietary vegetable oils promoted lower concentrations of short-chain (including 4:0) and medium-chain FA (including odd- and branched-chain FA) and 18:3n-3, and higher concentrations of C₁₈ FA (including stearic and oleic acids). The BI concentration was higher with the dietary inclusion of vegetable oils, although the magnitude of the concentration and its pattern differed between oils. The RO treatment resulted in moderate increases in BI, including trans 18:1 isomers and 18:2 trans-7,cis-9, but failed to increase 18:1 trans-11 and 18:2 cis-9,trans-11. Sunflower oil supplementation resulted in the highest concentrations of the 18:1 trans-10, 18:1 cis-12, and 18:2 trans-10,trans-12 isomers. Concentrations of 18:1 trans-11 and 18:2 cis-9,trans-11 were higher than with the control and RO treatments but were similar to the LO treatment. Concentration of BI in milk fat was maximal with LO, having the highest concentrations of some 18:1 isomers (i.e., trans-13/14, trans-15, cis-15, cis-16), most of the nonconjugated 18:2 isomers (i.e., trans-11,trans-15, trans-11,cis-15, cis-9,cis-15, and cis-12,cis-15), and conjugated 18:2 isomers (i.e., trans-11,cis-13, cis-12,trans-14, trans-11,trans-13, trans-12,trans-14, and trans-9,trans-11), and all conjugated 18:3 isomers. The LO treatment induced the highest amount and diversity of BI without decreasing milk fat concentration, as the RO and SO treatments had, suggesting that the BI associated with 18:3n-3 intake may not be the major contributors to inhibition of mammary milk fat synthesis.     

Effects of inflammatory conditions on liver activity in puerperium period and consequences for performance in dairy cows

The relationship between inflammation and general health conditions in dairy cows and the link between inflammation, liver function, and fertility are poorly understood. To clarify these relationships, 120 multiparous dairy cows were followed throughout an entire lactation. Blood samples were collected during the first month of lactation for a metabolic profile, and milk yield, disease occurrence, and fertility parameters were monitored during the entire lactation. Twenty-four cows were culled, and another 19 were excluded because they had serious problems after 30 d in milk (DIM) and before the first insemination. The remaining 77 cows were pregnant at the end of lactation and were retrospectively grouped into quartiles based on liver activity index (LAI), which is based on plasma negative acute phase proteins. Cows in the lower (LO) and intermediate lower (INLO) quartiles of LAI had more severe inflammations with high concentrations of haptoglobin (0.77 and 0.61 g/L) and globulin (42.5 and 39.0 g/L), respectively, during the first week of lactation compared with cows in the upper (UP) and intermediate upper (INUP) quartiles of LAI (haptoglobin: 0.28 and 0.45 g/L, and globulin: 34.2 and 36.9 g/L, respectively). At 7 DIM, the cows in LO and INLO had greater bilirubinemia (8.7 and 10.5 vs. 6.3 μM/L in UP) and lower blood urea (3.5 and 3.7 vs. 4.1 mM in UP). The INLO group exhibited more days open (139 vs. 93) and services per pregnancy (2.68 vs. 1.65), but lower milk yield (38.3 vs. 40.8 kg/d at 28 DIM) compared with UP. The LO group did not have a significantly lower fertility status, but presented the lowest milk yield (34.1 kg/d at 28 DIM). Our data suggest that cows with lower LAI scores had a more pronounced inflammatory status during the first month of lactation, an impairment of usual hepatic functions (e.g., bilirubin clearance), and a larger negative energy balance. The same cows had poorer performance (lower milk yield and fertility) than cows with higher LAI scores. Overall data suggest that any effort to avoid the acute phase response in the transition period would be useful for optimizing the productive and reproductive performance of high-yielding dairy cows.     

Effects of supplementation with a phytobiotics-rich herbal mixture on performance,udder health,and metabolic status of Holstein cows with various levels of milk somatic cell counts

This study evaluated the effects of dietary supplementation of a novel phytobiotics-rich herbal mixture (PRHM) on feed intake, performance, udder health, ruminal fermentation, and plasma metabolites in cows with moderate or high somatic cell counts (SCC) in the milk. Twenty-four Holstein dairy cows (117 ± 26 d in milk and 46.3 ± 4.7 kg of milk/d at the start of the experiment) were blocked by parity and days in milk and split into 2 groups, based on SCC in the milk; 12 cows were with moderate SCC (260,000 < SCC <500,000 cells/mL), whereas 12 other cows had high levels of SCC (>500,000 cells/mL) in the milk. Within each SCC group, cows were blocked by milk yield and parity, and were randomly assigned to 2 different feeding regimens. Half of the cows in each SCC group (n = 6) were supplemented with PRHM (185 g/cow per day, providing 12.4 g of phenolic compounds per day), and the other half (n = 6) were not supplemented in their diets. The experiment lasted 36 d, whereby the first 24 d were used for adaptation to the diets and the last 12 d for sampling. Data showed that supplementation of PRHM decreased somatic cell score in the milk, indicating improved udder health of cows with high initial SCC, but not in cows with moderate SCC. Also, cows supplemented with PRHM consumed more feed DM, produced greater amounts of milk, and showed an improvement of feed utilization efficiency. However, these cows also lost more back-fat thickness during the experiment. Supplementation of PRHM increased fat- and energy-corrected milk yields in cows with high initial SCC, but not in cows with moderate SCC. Supplementation of PRHM decreased milk fat content, whereas other milk components were not affected by PRHM feeding. The PRHM supplementation decreased the acetate-to-propionate ratio in the rumen fluid, but increased β-hydroxybutyrate and cholesterol concentration in the plasma, irrespective of the initial SCC level in the milk. Other plasma metabolites and liver enzymes were not affected by PRHM supplementation. Apparent nutrient digestibility did not differ among treatments. Overall, supplementation of PRHM seems to be an effective strategy to enhance performance and lower SCC, particularly in cows having high SCC levels in the milk. Further research is warranted to evaluate long-term effects of PRHM supplementation, especially with regard to metabolic health status and reproduction.     

Palmitic acid increased yields of milk and milk fat and nutrient digestibility across production level of lactating cows

The effects of palmitic acid supplementation on feed intake, digestibility, and metabolic and production responses were evaluated in dairy cows with a wide range of milk production (34.5 to 66.2 kg/d) in a crossover design experiment with a covariate period. Thirty-two multiparous Holstein cows (151 ± 66 d in milk) were randomly assigned to treatment sequence within level of milk production. Treatments were diets supplemented (2% of diet DM) with palmitic acid (PA; 99% C16:0) or control (SH; soyhulls). Treatment periods were 21 d, with the final 4 d used for data and sample collection. Immediately before the first treatment period, cows were fed the control diet for 21 d and baseline values were obtained for all variables (covariate period). Milk production measured during the covariate period (preliminary milk yield) was used as covariate. In general, no interactions were detected between treatment and preliminary milk yield for the response variables measured. The PA treatment increased milk fat percentage (3.40 vs. 3.29%) and yields of milk (46.0 vs. 44.9 kg/d), milk fat (1.53 vs. 1.45 kg/d), and 3.5% fat-corrected milk (44.6 vs. 42.9 kg/d), compared with SH. Concentrations and yields of protein and lactose were not affected by treatment. The PA treatment did not affect dry matter (DM) intake or body weight, tended to decrease body condition score (2.93 vs. 2.99), and increased feed efficiency (3.5% fat-corrected milk/DM intake; 1.60 vs. 1.54), compared with SH. The PA treatment increased total-tract digestibility of neutral detergent fiber (39.0 vs. 35.7%) and organic matter (67.9 vs. 66.2%), but decreased fatty acid (FA) digestibility (61.2 vs. 71.3%). As total FA intake increased, total FA digestibility decreased (R² = 0.51) and total FA absorbed increased (quadratic R² = 0.82). Fatty acid yield response, calculated as the additional FA yield secreted in milk per unit of additional FA intake, was 11.7% for total FA and 16.5% for C16:0 plus cis-9 C16:1 FA. The PA treatment increased plasma concentration of nonesterified FA (101 vs. 90.0 μEq/L) and cholecystokinin (19.7 vs. 17.6 pmol/L), and tended to increase plasma concentration of insulin (10.7 vs. 9.57 μIU/mL). Results show that palmitic acid fed at 2% of diet DM has the potential to increase yields of milk and milk fat, independent of production level without increasing body condition score or body weight. However, a small percentage of the supplemented FA was partitioned to milk.     

Substitution rate and milk yield response to corn silage supplementation of late-lactation dairy cows grazing low-mass pastures at 2 daily allowances in autumn

Feed costs in dairy production systems may be decreased by extending the grazing season to periods such as autumn when grazing low-mass pastures is highly probable. The aim of this autumn study was to determine the effect of corn silage supplementation [0 vs. 8 kg of dry matter (DM) of a mixture 7:1 of corn silage and soybean meal] on pasture intake (PI), milk production, and grazing behavior of dairy cows grazing low-mass ryegrass pastures at 2 daily pasture allowances (PA; low PA = 18 vs. high PA = 30 kg of DM/cow above 2.5 cm). Twelve multiparous Holstein cows were used in a 4 × 4 Latin square design with 14-d periods. Pre-grazing pasture mass and pre-grazing plate meter pasture height averaged 1.8 t of DM/ha (above 2.5 cm) and 6.3 cm, respectively. The quality of the offered pasture (above 2.5 cm) was low because of dry conditions before and during the experiment (crude protein = 11.5% of DM; net energy for lactation = 5.15 MJ/kg of DM; organic matter digestibility = 61.9%). The interaction between PA and supplementation level was significant for PI but not for milk production. Supplementation decreased PI from 11.6 to 7.6 kg of DM/d at low PA and from 13.1 to 7.3 kg of DM/d at high PA. The substitution rate was, therefore, lower at low than at high PA (0.51 vs. 0.75). Pasture intake increased with increasing PA in unsupplemented treatments, and was not affected by PA in supplemented treatments. Milk production averaged 13.5 kg/d and was greater at high than at low PA (+1.4 kg/d) and in supplemented than unsupplemented treatments (+5.2 kg/d). Milk fat concentration averaged 4.39% and was similar between treatments. Milk protein concentration increased from 3.37 to 3.51% from unsupplemented to supplemented treatments, and did not vary according to PA. Grazing behavior parameters were only affected by supplementation. On average, daily grazing time decreased (539 vs. 436 min) and daily ruminating time increased (388 vs. 486 min) from 0 to 8 kg of supplement DM. The PI rate was 6 g of DM/min lower in supplemented than in unsupplemented treatments (17 vs. 23 g of DM/min). The high milk yield response to supplementation may be related to a cumulative effect of the low-mass pasture (low PI) and the low quality of the pasture, which strongly limited energy supply in unsupplemented cows.     

Administration of bovine somatotropin in early lactation: a meta-analysis of production responses by multiparous Holstein cows

A meta-analysis was conducted to assess production responses before 90 d in milk (DIM) when bovine somatotropin (bST) administration was initiated between 5 and 35 DIM. The database was developed from 13 studies of multiparous cows that were published between 1985 and 2006 and from an unpublished study that complied with the study selection criteria. The database included results from 842 cows and provided 50 treatment means for the effect of bST on 3.5% fat-corrected milk (FCM) in early lactation. Effects of bST were investigated using mixed model procedures that included fixed (intercept and slope) and random (intercept and slope) effects for independent variables. Yields of milk (38.6 ± 1.3 kg/d) and FCM (37.6 ± 1.6 kg/d) by control cows before 90 DIM were increased by 2.6 ± 0.8 and 3.2 ± 0.6 kg/d by bST administration. Fat content in milk from bST-treated cows was 0.31 ± 0.10 percentage units greater than that from control cows (3.46 ± 0.13%) but milk protein content (2.95 ± 0.03%) was not altered by bST. Milk fat (1.39 ± 0.10 kg/d) and protein (1.15 ± 0.04 kg/d) yields by controls were increased 0.16 ± 0.03 and 0.07 ± 0.03 kg/d by bST, respectively. Dry matter intake and body weight loss were not altered by bST before 90 DIM, but duration of negative energy balance was prolonged and overall energy balance during this interval reduced when cows were treated with bST. Results are consistent with the premise that bST-treated cows partition nutrients and energy toward milk synthesis for a longer duration and thus likely need a longer interval to replenish their body reserves than cows not treated with bST. Production responses to bST were not altered when cows consumed typical early-lactation diets supplemented with fat except that supplemental fat tended to decrease the magnitude of the effect of bST on milk fat content and decreased the effect of bST on fat and protein yield. Yield of FCM increased curvilinearly with the amount of bST administered. Results indicate that initiation of bST administration to cows before 35 DIM increased FCM yield but the response was at the low end of that typically observed when bST administration is initiated in wk 9 of lactation.     

Effects of addition of essential oils and monensin premix on digestion, ruminal fermentation, milk production, and milk composition in dairy cows

Four ruminally cannulated, lactating Holstein cows were used in a 4 × 4 Latin square design (28-d periods) with a 2 × 2 factorial arrangement of treatments to study the effects of dietary addition of essential oils (0 vs. 2 g/d; EO) and monensin (0 vs. 350 mg/d; MO) on digestion, ruminal fermentation characteristics, milk production, and milk composition. Intake of dry matter averaged 22.7 kg/d and was not significantly affected by dietary additives. Apparent digestibilities of dry matter, organic matter, neutral detergent fiber, and starch were similar among treatments. Apparent digestibility of acid detergent fiber was increased when diets were supplemented with EO (48.9 vs. 46.0%). Apparent digestibility of crude protein was higher for cows fed MO compared with those fed no MO (65.0 vs. 63.6%). Nitrogen retention was not changed by additive treatments and averaged 27.1 g/d across treatments. Ruminal pH was increased with the addition of EO (6.50 vs. 6.39). Ruminal ammonia nitrogen (NH₃-N) concentration was lower with MO-supplemented diets compared with diets without MO (12.7 vs. 14.3 mg/100 mL). No effect of EO and MO was observed on total volatile fatty acid concentrations and molar proportions of individual volatile fatty acids. Protozoa counts were not affected by EO and MO addition. Production of milk and 4% fat-corrected milk was similar among treatments (33.6 and 33.4 kg/d, respectively). Milk fat content was lower for cows fed MO than for cows fed diets without MO (3.8 vs. 4.1%). The reduced milk fat concentration in cows fed MO was associated with a higher level of trans-10 18:1, a potent inhibitor of milk fat synthesis. Milk urea nitrogen concentration was increased by MO supplementation, but this effect was not apparent when MO was fed in combination with EO (interaction EO × MO). Results from this study suggest that feeding EO (2 g/d) and MO (350 mg/d) to lactating dairy cows had limited effects on digestion, ruminal fermentation characteristics, milk production, and milk composition.     

Compared with stearic acid,palmitic acid increased the yield of milk fat and improved feed efficiency across production level of cows

The effects of dietary palmitic and stearic acids on feed intake, yields of milk and milk components, and feed efficiency of dairy cows were evaluated in an experiment with a crossover arrangement of treatments with a covariate period. Cows with a wide range of milk production (38 to 65 kg/d) were used to determine if response to fat supplementation varied according to production level. Thirty-two Holstein cows (143 ± 61 d in milk) were assigned randomly to a treatment sequence within level of milk production. Treatments were diets supplemented (2% of diet dry matter) with palmitic acid (PA; 97.9% C16:0) or stearic acid (SA; 97.4% C18:0). Treatment periods were 21 d and cows were fed a nonfat supplemented diet for 14 d immediately before the first treatment period. The final 4 d of each period were used for sample and data collection. Milk production measured during the covariate period (preliminary milk yield) was used as the covariate. No interactions were detected between treatment and preliminary milk yield for the production response variables measured. Compared with SA, the PA treatment increased milk fat concentration (3.66 vs. 3.55%) and yield (1.68 vs. 1.59 kg/d), and 3.5% fat-corrected milk yield (47.5 vs. 45.6 kg/d). Treatment did not affect dry matter intake, milk yield, milk protein yield, body weight, or body condition score. Milk protein concentration was lower for PA compared with SA treatment (3.24 vs. 3.29%). The PA treatment increased feed efficiency (3.5% fat-corrected milk yield/dry matter intake) compared with SA (1.48 vs. 1.40). The increase in milk fat yield by PA was entirely accounted for by a 24% increase in 16-carbon fatty acid output into milk. Yields of de novo (3.2%) and preformed fatty acids (2.9%) were only slightly decreased by PA relative to SA. The PA treatment increased plasma concentration of nonesterified fatty acids (96.3 vs. 88.2 μEq/L) and glucose (56.6 vs. 55.7 mg/dL) compared with SA, but insulin and β-hydroxybutyrate were not altered by the treatments. Results demonstrate that palmitic acid is more effective than stearic acid in improving milk fat concentration and yield as well as efficiency of feed conversion to milk. Responses were independent of production level and without changes in body condition score or body weight. Further studies are required to test the consistency of these responses across different types of diets.     

Milk production and composition of mid-lactation cows consuming perennial ryegrass-and chicory-based diets

Dry matter intakes (DMI), nutrient selection, and milk production responses of dairy cows grazing 3 herbage-based diets offered at 2 allowances were measured. The 2 allowances were 20 (low) and 30 (high) kg of dry matter (DM)/cow per day and these were applied to 3 herbage types: perennial ryegrass (PRG) and chicory (CHIC+) monocultures and a mixed sward of chicory and perennial ryegrass (MIX). The CHIC+ diet was supplemented with alfalfa hay (approximately 2 kg of DM/cow per day) to maintain dietary neutral detergent fiber (NDF) concentration and all diets were supplemented with energy-based pellets (6 kg of DM/cow per day). Holstein-Friesian dairy cows averaging 136 ± 30 d in milk were allocated to 4 replicates of the 6 treatments using stratified randomization procedures. Cows were adapted to their experimental diets over a 14-d period, with measurements of DMI, milk yield, and composition conducted over the following 10 d. Herbage DMI was lowest (12.8 vs. 14.0 kg of DM/d) for CHIC+ compared with the MIX and PRG, although total forage intake (grazed herbage plus hay) was similar (14.0 to 15.0 kg of DM/d) across the 3 treatments. Milk production, milk protein, and milk fat concentrations were not different between herbage types. Grazed herbage DMI increased with increasing herbage allowance and this was associated with increased milk protein concentration (3.23 to 3.34%) and total casein production (41.7 to 43.6 mg/g). Concentrations of polyunsaturated fatty acids in milk fat, particularly linoleic acid, were increased in milk from cows offered the CHIC+ or the MIX diets, indicating potential benefits of chicory herbage on milk fatty acid concentrations. Although feeding CHIC+ or MIX did not increase milk yield, these herbage types could be used as an alternative to perennial ryegrass pasture in spring.     

Direct-fed microbial supplementation on ruminal digestion, health, and performance of pre- and postpartum dairy cattle

Effects of supplementing direct-fed microbial agents (DFM) to dairy cows during the transition period were evaluated. Forty-four Holstein cows were fed close-up and lactating diets that did or did not contain 2 g of DFM/cow per d. Direct-fed microbial supplementation contained approximately 5 × 10⁹ cfu of yeast and 5 × 10⁹ cfu of bacteria (2 specific Enterococcus faecium strains) incorporated into a cornmeal carrier. Supplemented cows were fed the DFM 21 d prior to expected calving date through 10 wk postpartum. Cows supplemented with DFM had higher estimated ruminally available dry matter (DM) for both corn silage and haylage than did control cows. Supplemented cows consumed more DM during both the pre- and postpartum periods. In addition, those supplemented with DFM produced 2.3 kg more milk/cow per d than did nonsupplemented cows. There was no difference in 3.5% fat-corrected milk. Milk fat percentage was lower, but not depressed (4.76 vs. 4.44%) for cows receiving DFM. There were no differences in milk fat yield or milk protein percentage and yield. Cows consuming DFM had higher blood glucose postpartum, as well as lower β-hydroxybutyrate levels both prepartum and on d 1 postpartum. Plasma nonesterified fatty acid concentration was not statistically affected by DFM, but was numerically lower prepartum and higher postpartum for supplemented cows. This study demonstrated that targeted DFM supplementation enhanced ruminal digestion of forage DM. Early lactation cows receiving supplemental DFM produced more milk and consumed more DM during the pre- and postpartum periods. Cows consuming DFM, however, experienced a lower, but not depressed, fat percentage compared with nonsupplemented cows.     

Effect of alfalfa silage storage structure and roasting corn on production and ruminal metabolism of lactating dairy cows

The objective of this study was to determine if feeding roasted corn would improve production and nutrient utilization when supplemented to lactating cows fed 1 of 3 different alfalfa silages (AS). Forty-two lactating Holstein cows (6 fitted with ruminal cannulas) averaging 77 d in milk and 43 kg of milk/d pretrial were assigned to 2 cyclic changeover designs. Treatments were AS ensiled in bag, bunker, or O₂-limiting tower silos and supplemented with ground shelled corn (GSC) or roasted GSC (RGSC). Silages were prepared from second-cutting alfalfa, field-wilted an average of 24 h, and ensiled over 2 d. Production and N utilization were evaluated in 36 cows during four 28-d periods, and ruminal fermentation was evaluated with 6 cows during five 21-d periods. Experimental diets contained 40% AS, 15% corn silage, and 35% of either GSC or RGSC on a dry matter basis. No significant interactions between AS and corn sources were detected for any production trait. Although the chemical composition of the 3 AS was similar, feeding AS from the O₂-limited tower silo elicited positive production responses. Yields of 3.5% fat-corrected milk and fat were increased 1.7 kg/d and 150 g/d, and milk fat content was increased 0.3% when cows were fed diets based on AS from the O₂-limiting silo compared with the other 2 silages. The responses in milk fat were paralleled by an average increase in acid detergent fiber digestibility of 270 g/d for cows fed AS from the O₂-limiting tower silo. However, ruminal concentrations of lipogenic volatile fatty acids were unchanged with AS source. Cows fed RGSC consumed 0.6 kg/d more dry matter and yielded 30 g/d more protein and 50 g/d more lactose than cows fed GSC diets. There was no evidence of increased total tract digestibility of organic matter or starch, or reduced ruminal NH₃ concentration, when feeding RGSC. Free amino acids increased, and isovalerate decreased in rumen fluid from cows fed RGSC diets. However, responses in production with roasted corn were mainly due to increased dry matter intake, which increased the supply of energy and nutrients available for synthesis of milk and milk components.     

The value of different fat supplements as sources of digestible energy for lactating dairy cows

The effects of fat supplements that differed in fatty acid composition (chain length and degree of saturation) and chemical form (free fatty acids, Ca salts of fatty acids, and triacylglyceride) on digestible energy (DE) concentration of the diet and DE intake by lactating cows were measured. Holstein cows were fed a control diet [2.9% of dry matter (DM) as long-chain fatty acids] or 1 of 3 diets with 3% added fatty acids (that mainly replaced starch). The 3 fat supplements were (1) mostly saturated (C18:0) free fatty acids (SFA), (2) Ca-salts of fatty acids (CaFA), and (3) triacylglyceride high in C16:0 fatty acids (TAG). Cows fed CaFA (22.8 kg/d) consumed less DM than cows fed the control (23.6 kg/d) and TAG (23.8 kg/d) diets but similar to cows fed SFA (23.2 kg/d). Cows fed fat produced more fat-corrected milk than cows fed the control diet (38.2 vs. 41.1 kg/d), mostly because of increased milk fat percentage. No differences in yields of milk or milk components were observed among the fat-supplemented diets. Digestibility of DM, energy, carbohydrate fractions, and protein did not differ between diets. Digestibility of long-chain fatty acids was greatest for the CaFA diet (76.3%), intermediate for the control and SFA diets (70.3%), and least for the TAG diet (63.3%). Fat-supplemented diets had more DE (2.93 Mcal/kg) than the control diet (2.83 Mcal/kg), and DE intake by cows fed supplemented diets was 1.6 Mcal/d greater than by cows fed the control, but no differences were observed among the supplements. Because the inclusion rate of supplemental fats is typically low, large differences in fatty acid digestibility may not translate into altered DE intake because of small differences in DM intake or digestibility of other nutrients.     

The effect of marine algae in the ration of high-yielding dairy cows during transition on metabolic parameters in serum and follicular fluid around parturition

Sixteen Holstein cows were assigned to 2 groups to evaluate the caloric and metabolic effect of feeding marine algae (ALG) from 3 wk prepartum until 12 wk postpartum. Milk production characteristics and the profiles of hormones and metabolites in the serum were monitored from −7 to 46 d in milk (DIM) and in follicular fluid (FF) from 14 to 46 DIM. All cows received a corn- and grass silage-based partially mixed ration supplemented with concentrate and protein supplement. In the diet of the ALG group, 2 kg of the concentrate was replaced by a concentrate containing ALG (44 g/d of docosahexaenoic acid). Diets were isocaloric (net energy basis) and equal in intestinal digestible protein. The ALG diet increased milk yield (41.2 vs. 38.2 kg/d) and decreased milk fat yield (1.181 vs. 1.493 kg/d) and milk fat content (31.6 vs. 40.7 g/kg). Protein yield (1.336 vs. 1.301 kg/d) was not affected but a tendency toward decreased milk protein content (32.8 vs. 34.7 g/kg) was observed. Marine algae supplementation increased the β-hydroxybutyric acid (BHBA) concentration in FF of the ALG cows compared with that in the controls (0.992 vs. 0.718 mmol/L). The total protein concentration in FF was decreased in ALG (62.9 vs. 67.6 g/L). Plasma and serum metabolites did not significantly differ between treatments except for a tendency toward a lower concentration of urea in the serum of the control compared with ALG (4.69 vs. 5.13 mmol/L). Based on metabolizable energy calculations, a daily energy-sparing effect of 3.48 Mcal was obtained due to milk fat depression (MFD). The concomitant increase in milk yield suggests that at least part of this spared energy is used to stimulate milk production. Theoretically, 3.48 Mcal of ME could lead to an increase in milk yield of 7.43 kg/d, which is higher than the observed 3 kg/d. However, when evaluating nutrient requirements during MFD in early lactation, we calculated that increased milk production is caused by a propionate-saving effect of 2.71 mol in the udder when milk fat is depressed. Concurrent increased BHBA concentrations in FF in the ALG group cannot be attributed to a worsened energy status of the animals because all other indicators contradict any change in energy balance, indicating that BHBA might not be an appropriate metabolic parameter to estimate the energy balance in early lactating dairy cows during MFD.     

Short communication: Responses to supplemental Saccharomyces cerevisiae fermentation product and triticale grain in dairy cows grazing high-quality pasture in early lactation

Supplementing cows grazing highly digestible pasture with a Saccharomyces cerevisiae fermentation product (SCFP) was hypothesized to increase dry matter (DM) intake and milk production. Sixty multiparous dairy cows were fed 3 kg of crushed triticale DM/cow per day for 23 ± 4.4 d before calving. Half of the cows received SCFP (60 g/d; Diamond V Original XP; Diamond V Mills, Inc., Cedar Rapids, IA). Cows in both treatment groups were randomly allocated at calving to 1 of 2 amounts (3 or 6 kg of DM/d) of triticale feeding with or without 60 g of SCFP/day (n = 15/treatment) until 84 days in milk. The amount of pasture harvested (kg of DM/cow per day) and milk yield (kg/cow per day) were not affected by SCFP. Milk protein content and yield were greater in cows receiving 6 kg of crushed triticale DM/d. Plasma nonesterified fatty acids and β-hydroxybutyrate concentrations were not affected by SCFP supplementation, but were lower in cows fed 6 kg of crushed triticale DM/d than those fed 3 kg of DM/d. Supplementation with SCFP increased milk lactose content without affecting milk production under the conditions investigated.     

Effect of dry period length and dietary energy source on energy balance,milk yield,and milk composition of dairy cows

The objective of this study was to evaluate the effects of dry period length and dietary energy source in early lactation on milk production, feed intake, and energy balance (EB) of dairy cows. Holstein-Friesian dairy cows (60 primiparous and 108 multiparous) were randomly assigned to dry period lengths (0, 30, or 60 d) and early lactation ration (glucogenic or lipogenic), resulting in a 3 × 2 factorial design. Rations were isocaloric and equal in intestinal digestible protein. The experimental period lasted from 8 wk prepartum to 14 wk postpartum and cows were monitored for milk yield, milk composition, dry matter intake (DMI), energy balance, and milk fat composition. Prepartum average milk yield for 60 d precalving was 13.8 and 7.7 ± 0.5 kg/d for cows with a 0- and 30-d dry period, respectively. Prepartum DMI and energy intake were greater for cows without a dry period and 30-d dry period, compared with cows with a 60-d dry period. Prepartum EB was greater for cows with a 60-d dry period. Postpartum average milk yield until wk 14 was lower for cows without a dry period and a 30-d dry period, compared with cows with a 60-d dry period (32.7, 38.7, and 43.3 ± 0.7 kg/d for 0-, 30-, and 60-d dry period, respectively). Postpartum DMI did not differ among treatments. Postpartum EB was greater for cows without a dry period and a 30-d dry period, compared with cows with a 60-d dry period. Young cows (parity 2) showed a stronger effect of omission of the dry period, compared with a 60-d dry period, on additional milk precalving (young cows: 15.1 kg/d; older cows: 12.0 kg/d), reduction in milk yield postcalving (young cows: 28.6 vs. 34.8 kg/d; older cows: 41.8 vs. 44.1 kg/d), and improvement of the EB postcalving (young cows: 120 vs. −93 kJ/kg^0.75·d; older cows: −2 vs. −150 kJ/kg^0.75·d. Ration did not affect milk yield and DMI, but a glucogenic ration tended to reduce milk fat content and increased EB, compared with a more lipogenic ration. Reduced dry period length (0 and 30 d) increased the proportion of short- and medium-chain fatty acids in milk fat and omitting the dry period decreased the proportion of long-chain fatty acids in milk fat. In conclusion, shortening and omitting the dry period shifts milk yield from the postpartum to the prepartum period; this results in an improvement of the EB in early lactation. An increased energy status after a short dry period can be further improved by feeding a more glucogenic ration in early lactation.     

Selenium levels in cows fed pasture and concentrates or a total mixed ration and supplemented with selenized yeast to produce milk with supra-nutritional selenium concentrations

Seventy multiparous Holstein-Friesian cows were fed different amounts of pasture and concentrates, or a total mixed ration (TMR), for 42 d in mid-lactation to test the hypothesis that the concentration of Se in milk would depend on the amount of Se consumed, when the Se is primarily organic in nature, regardless of the diet of the cows. Of the 70 cows, 60 grazed irrigated perennial pasture at daily allowances of either 20 or 40 kg of dry matter (DM)/cow. These cows received 1 of 3 amounts of concentrates, either 1, 3, or 6 kg of DM/cow per day of pellets, and at each level of concentrate feeding, the pellets were formulated to provide 1 of 2 quantities of Se from Se yeast, either about 16 or 32 mg of Se/d. The other 10 cows were included in 2 additional treatments where a TMR diet was supplemented with 1 kg of DM/d of pellets formulated to include 1 of the 2 quantities of supplemental Se. Total Se intakes ranged from 14.5 to 35.9 mg/d, and of this, the Se-enriched pellets provided 93, 91, and 72% of the Se for cows allocated 20 and 40 kg of pasture DM/d or the TMR, respectively. No effects of the amount of Se consumed on any milk production variable, or on somatic cell count, body weight, and body condition score, for either the pasture-fed or TMR-fed cows were found. Milk Se concentrations responded quickly to the commencement of Se supplementation, reaching 89% of steady state levels at d 5. When milk Se concentrations were at steady state (d 12 to 40), each 1 mg of Se eaten increased the Se concentration of milk by 5.0 μg/kg (R² = 0.97), and this response did not seem to be affected by the diet of the cows or their milk production. The concentration of Se in whole blood was more variable than that in milk, and took much longer to respond to change in Se status, but it was not affected by diet at any time either. For the on-farm production of Se-enriched milk, it is important to be able to predict milk Se concentration from Se input. In our study, type of diet did not affect this relationship.     

Effect of dietary N-carbamoylglutamate on milk production and nitrogen utilization in high-yielding dairy cows

The objective of the current study was to investigate the effect of N-carbamoylglutamate (NCG) supplementation on milk production and nitrogen (N) utilization in Chinese Holstein dairy cows. Sixty multiparous cows (78 ± 17.3 d in milk, 635 ± 61.00 kg of body weight, and 41.9 ± 7.9 kg/d milk yield; mean ± SD) were blocked by parity, days in milk, and milk yield and randomly allocated to 1 of 4 groups, each of which was fed a dietary treatment containing 0 (control), 10, 20, or 30 g of NCG/d. Milk yield was recorded weekly. Dry matter intake, milk composition, plasma variables, and urea N contents in plasma, urine, and milk were determined every other week. Blood samples were collected from the coccygeal vein. Rumen microbial protein synthesis was estimated based on the purine derivatives in the urine. Dry matter intake was found to be similar between the treatments. Addition of 20 g of NCG/d tended to increase milk yield (40.2 vs. 38.1 kg/d) and increased the content (2.83 vs. 2.74%) and yield (1.12 vs. 1.02 kg/d) of milk protein compared with the control. The yield and content of milk fat were similar between the treatments, whereas the contents of lactose and total solids increased linearly with an increase in NCG. Dietary supplementation of NCG linearly increased the plasma nitric oxide level and decreased the plasma ammonia N level. Compared with the control, the plasma Arg concentration in cows fed 10, 20, and 30 g of NCG/d was increased by 1.1, 10.4, and 16.0%, respectively. The urea N concentrations in the milk, plasma, and urine decreased with the addition of NCG, although the lowest urea N concentrations were observed with the addition of 20 g of NCG/d. The conversion of dietary crude protein to milk protein exhibited quadratic trends of improvement by NCG supplementation, with a peak at 20 g of NCG/d. The rumen microbial protein synthesis was not altered by NCG supplementation, but the metabolizable protein tended to show a quadratic increase in cows fed 20 g of NCG/d. In conclusion, supplementation of 20 g of NVG/d may alter the plasma metabolites, optimize the AA profile, increase the metabolizable protein utilization, and thereby improve the lactation performance and N utilization of high-yielding dairy cows.     

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.     

Effect of grains differing in expected ruminal fermentability on the productivity of lactating dairy cows

The objective of the study was to evaluate the effect of barley and corn grains differing in expected fermentability in the rumen on dry matter intake (DMI) and productivity of lactating dairy cows. Twenty-two multiparous and 9 primiparous lactating Holstein cows (94 ± 29 d in milk; mean ± SD) were used in a 3 × 3 Latin square design with 21-d periods. Experimental diets contained approximately 40% of dietary dry matter as steam-rolled barley, using a lot of cultivar Dillon or cultivar Xena, or a corn mixture (CM) containing 87.5% dry ground corn, 11.4% beet pulp, and 1.1% urea (dry matter basis). Starch concentration of the grain sources was 50.0, 58.7, and 60.4% and in vitro 6-h starch digestibility was 73.5, 78.0, and 71.0%, respectively, for Dillon, Xena, and CM. All diets were formulated to contain 19.4% crude protein and 25.3% forage neutral detergent fiber. Dry matter intake (23.6 vs. 21.6 kg/d) and yields of milk (40.4 vs. 37.4 kg/d), milk protein (1.20 vs. 1.12 kg/d), and milk lactose (1.85 vs. 1.74 kg/d) were higher for cows fed CM than for cows fed barley. Although DMI was similar for cows fed Xena and Dillon (21.9 vs. 21.4 kg/d), cows fed Xena had higher yields of milk (38.5 vs. 36.2 kg/d), milk protein (1.18 vs. 1.07 kg/d), and milk lactose (1.80 vs. 1.69 kg/d) than cows fed Dillon. However, milk fat concentration tended to be higher (3.47 vs. 3.23%) for cows fed Dillon than Xena. Plasma glucose and nonesterified fatty acid concentrations were not affected by treatment, but plasma insulin concentration was higher for cows fed Xena compared with those fed Dillon (8.50 vs. 5.91 μIU/mL). Greater milk production for cows fed CM can be attributed to greater DMI. Feeding barley that was lower in starch concentration and ruminal starch fermentability (Dillon) did not increase DMI compared with feeding barley that was higher in starch concentration and ruminal starch fermentability (Xena). Reducing ruminal starch degradation of barley grain may not improve the productivity of lactating dairy cows.     

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.