Effect of amount and source of dietary nitrogen on milk fat depression in early lactation dairy cows

Twenty-four multiparous and 15 primiparous Holstein cows were fed a total mixed corn silage diet with one of three dietary treatments: 14% crude protein, 22% crude protein (all preformed), or 22% crude protein (preformed plus nonprotein N). Eight multiparous and 5 primiparous cows were randomly assigned to each treatment at calving. The diet contained 23% ADF during wk 1 to 4 postpartum and was lowered to 11% ADF for wk 5 to 12 postpartum. Treatment had no effect on the magnitude of depression in milk fat percentage or milk fat yield in multiparous cows. After fiber was lowered, changes in rumen acetate to propionate ratio, blood glucose, free fatty acids, and insulin were not influenced by treatment. Depression in milk fat percentage for primiparous cows was 19.7, 9.2, and 14.9% for low protein, high protein, and high protein with nonprotein N, respectively. When changed from high fiber to low fiber, the primiparous cows increased milk fat yield 9% for high preformed protein treatment but decreased fat yield for other treatments. Depression in acetate to propionate ratio and increase in blood glucose was least for the high preformed protein group.     

Effects of Body Condition and Protein on Milk Fat Depression in Early Lactation Dairy Cows

Twenty multiparous and 16 primiparous Holstein cows were fed either a high energy or low energy diet during the dry period to achieve different degrees of body condition. Three weeks postpartum, cows were randomly assigned to either a high protein (23% CP) or a low protein (14.5% CP) diet. The diet contained 21% ADF during wk 3 through 6 postpartum and lowered to 9% ADF during wk 7 through 14 postpartum to depress fat test. Cows fed the low energy prepartum diet had less fat depression when fed the high protein postpartum diet compared with the low protein diet. Milk fat depression was more severe for all cows fed the high energy prepartum diet. Depression in milk fat percentage for multiparous cows was 30.8, 10.2, 34.5, and 26.0% for high energy-high protein, low energy-high protein, high energy-low protein, and low energy-low protein groups, respectively. For primiparous cows, milk fat depression was 37.3, 24.1, 37.0, and 34.6%. After the fiber change, depression in acetate to propionate ratio was less for multiparous cows fed high protein than for those fed low protein. Prepartum energy did not influence acetate to propionate ratio depression that resulted from the fiber change.     

Effect of total and rumen undegradable protein on the performance of cows fed low fiber diets.

Twelve multiparous and 18 primiparous Holstein cows were fed a 17.3% CP, 21.0% ADF diet during wk 2 through 6 postpartum. Cows then were assigned from wk 7 through 14 to one of three low fiber (10.7% ADF) dietary treatments containing either 14.4 or 18.7% CP, the latter with or without a soybean meal enhanced with rumen undegradable protein. Treatments had no effect on milk yield or composition in multiparous cows, although milk fat percentage was not depressed in multiparous cows receiving the low fiber diets. The soybean meal diet enhanced with rumen undegradable protein increased yields of milk, 4% FCM, fat, protein, and DMI compared with the 14.4% CP diet in primiparous cows; it also increased yields of 4% FCM and fat versus the 18.7% CP, untreated diet in primiparous cows. Blood urea N concentrations were greater for high CP diets than for the low CP diet in both parity groups. Rumen acetate: propionate ratios were higher for both high CP diets than for the low CP diet in multiparous cows. Soybean meal enhanced with rumen undegradable protein improved yields of milk and its components in primiparous cows fed low fiber diets, even when high protein diets were fed.     

Effect of whole and expanded-expelled cottonseed on milk yield and blood gossypol

Thirty-two primiparous and 12 multiparous Holstein cows were randomly assigned at calving to treatments to determine the effects of type and amount of cottonseed product on plasma gossypol, milk production, and composition, and conjugated linoleic acid concentration in milk fat. Rations consisted of corn silage, corn grain, soybean meal, and cottonseed hulls, and contained on average 16.8% crude protein and 25.3% acid detergent fiber on a dry matter basis. On a dry matter basis, diets contained one of the following: 1) 14% whole cottonseed; 2) 14% expanded-expelled cottonseed; 3) 21% expanded-expelled cottonseed; or 4) 28% expanded-expelled cottonseed. Cows remained on treatment from 30 through 120 d in milk. Dry matter intakes were not significantly different, but intakes of crude protein, acid detergent fiber, and fat were higher for multiparous cows fed whole cottonseed. Multiparous cows fed whole cottonseed had higher yields of milk, fat-corrected milk, crude protein, fat and solids-not-fat than those fed any level of expanded-expelled cottonseed. Concentrations of milk fat, protein, and SNF were not affected by treatment. Although there were treatment differences in fat intake, there were no production differences in primiparous cows. Milk production efficiency (fat-corrected milk/dry matter intake) was not affected by treatment for either multiparous or primiparous cows. Cows fed 14% whole or 14% expanded-expelled cottonseed had similar levels of total plasma gossypol and plasma levels of the negative isomer of gossypol. Increasing the level of expanded-expelled cottonseed in the diet increased both total plasma gossypol and the negative isomer. In this experiment, multiparous but not primiparous cows fed whole cottonseed produced more milk than those fed expanded-expelled cottonseed at 14 to 28% of the diet dry matter, however, feed efficiencies were similar for all treatments.     

Effects of protein level and forage source on milk production and composition in early lactation dairy cows.

Twenty multiparous and 12 primiparous Holstein cows were assigned at calving to one of three grass hay-based diets containing either 14, 18, or 22% CP or an alfalfa hay-based diet containing 22% CP to examine the effect of protein level and forage source on milk yield and composition. The diets contained 23% ADF during wk 1 to 4 postpartum, which was lowered to 11% for wk 5 to 12 postpartum. Cows fed the 18 and 22% CP grass-based diets produced higher yields of milk, 4% FCM, fat, protein, and SNF than those fed the 14% CP diet during the high fiber period. In addition, cows fed the 22% CP grass-based diet had higher milk fat tests than those fed the 14% CP diet during the high fiber period, due primarily to an increase in short-chain fatty acid synthesis. Milk fat depression was more severe when cows were changed to low fiber diets while fed the 22% CP alfalfa-based diet than when fed the 22% CP grass-based diet. Depression in milk fat content was 15.0, 17.0, 15.6, and 27.0% for 14, 18, and 22% CP grass-based and 22% CP alfalfa-based diets, respectively. Cows receiving the 18 and 22% CP grass-based diets exhibited higher blood NEFA during the high fiber feeding period than those fed the 14% CP diet. After fiber was lowered, changes in rumen acetate:propionate ratios were unaffected by treatment. Lowering fiber level resulted in an increased milk CP percentage regardless of treatment. Grass hay appeared to be more effective than alfalfa hay in preventing depression in milk fat test upon the change to a low fiber diet.     

Influence of dietary protein and supplemental niacin on lactational performance of cows fed normal and low fiber diets.

Forty-seven cows (24 primiparous) were assigned to one of four normal (20.5%) ADF diets for wk 2 to 5 postpartum. Dietary treatments in a 2 x 2 factorial design were diets of 13.8 versus 18.8% CP and 0 versus 12 g/d of niacin per cow. During wk 6 to 13 postpartum, cows were fed low (11.8%) ADF diets while maintaining CP and niacin treatments. Low CP diets contained solvent-extracted soybean meal; rumen soybean meal with enhanced undegradable protein was used in high CP diets. High CP diets increased milk protein percentage in multiparous cows and yields of milk, 4% FCM, fat, protein, and SNF in primiparous cows during the normal fiber period. High dietary CP also increased yields of 4% FCM, fat, protein, and SNF in primiparous cows fed normal fiber diets. When switched to low fiber diets, primiparous cows fed high CP diets decreased more in 4% FCM and fat yields than those fed low CP. Primiparous cows fed niacin decreased more in 4% FCM than controls. High dietary CP increased DMI in primiparous cows fed normal fiber diets, but those fed low CP diets increased more in DMI when switched to low fiber diets. Supplemental niacin appeared to interact with dietary CP in multiparous cows, increasing blood glucose and decreasing blood beta-hydroxybutyrate and NEFA concentrations with the high CP, normal fiber diet. Increased dietary CP improved yields of milk and milk components in primiparous cows.     

Effects of lasalocid on performance of lactating dairy cows.

Sixty lactating dairy cows (30 multiparous and 30 primiparous) were used in a completely randomized block design to determine the effect of lasalocid supplementation on dairy cow performance. Starting wk 2 prepartum and lasting through wk 17 of lactation, cows received one of three experimental diets. The experimental total mixed rations were control (CD), control + 10 mg/kg of lasalocid (CD + 10) and control + 20 mg/kg of lasalocid (CD + 20). The alfalfa-based control diet (40:60; forage:concentrate) was formulated to contain 18% crude protein, 35% nonstructural carbohydrates, 31% neutral detergent fiber, and 6.6% ether extract. Lasalocid supplementation linearly decreased dry matter intake (DMI) without affecting milk production or milk composition. Mean milk production and percentages of fat and protein were 30.0, 30.8, and 28.6; 3.56, 3.51, and 3.63; 3.06, 3.05, and 3.09; respectively for treatments CD, CD + 10, and CD + 20. Lasalocid supplementation decreased milk urea N (MUN) when compared to control cows, and increasing supplementation caused a significant linear decrease in MUN. For the primiparous cows, lasalocid supplementation decreased DMI and MUN while increasing body condition score and feed efficiency. Results from this study indicate that lactating dairy cows and, in particular, primiparous cows may benefit from lasalocid supplementation in terms of more efficient utilization of nutrients for milk production, reduced MUN levels, reduced body condition loss, and higher margin over feed cost.     

Supplementation of methionine and selection of highly digestible rumen undegradable protein to improve nitrogen efficiency for milk production

Metabolizable protein (MP) supply and amino acid balance were manipulated through selection of highly digestible rumen-undegradable protein (RUP) sources and methionine (Met) supplementation. Effects on production efficiency and N utilization of lactating dairy cows were determined. Thirty-two multiparous (647 kg) and 28 primiparous (550 kg) Holstein cows were assigned during the fourth week of lactation to one of four dietary treatments. Treatments were 1) 18.3% crude protein (CP) with low estimated intestinal digestibility of RUP (HiCP-LoDRUP), 2) 18.3% CP with high digestibility RUP (HiCP-HiDRUP), 3) 16.9% CP with high digestibility RUP (LoCP-HiDRUP), and 4) 17.0% CP with high digestibility RUP and supplemental Met (LoCP-HiDRUP + Met). Diets were balanced to have equal concentrations of net energy for lactation (NE(L)), acid detergent fiber (ADF), neutral detergent fiber (NDF), and ash. Milk yields (40.8, 46.2, 42.9, 46.6 kg/d), protein percentages (2.95, 2.98, 2.99, 3.09%), and fat percentages (3.42, 3.64, 3.66, 3.73%) are reported here for HiCP-LoDRUP, HiCP-HiDRUP, LoCP-HiDRUP, and LoCP-HiDRUP + Met, respectively. Milk urea N and BUN decreased when feeding a lower CP diet. Efficiency of use of N for milk protein production was higher when feeding higher digestibility RUP, especially with the LoCP-HiDRUP + Met diet. A digestibility study followed the production trial, with six cows per treatment group continuing on the same treatment for an additional week. The experimental periods were 5 d long, with 1 d of adjustment and 4 d of total collection of urine and feces. Dry matter intake, milk production, milk protein production, and N digestibility were not significantly different among treatments during the collection trial, whereas N intake and N absorbed increased with the higher CP diets. The quantity of N in feces did not change with diet, but quantity of N in urine decreased in the low CP diets. Milk N as a percentage of intake N and milk N as a percentage of N absorbed showed a trend toward increasing as CP concentration in the diet decreased. The supplementation of Met did not improve the efficiency of N utilization during the digestibility study, in contrast to what was estimated during the production trial. Supplementing the highly digestible RUP source with rumen available and rumen escape sources of Met resulted in maximal milk and protein production and maximum N efficiency by cows during the production trial, indicating that postruminal digestibility of RUP and amino acid balance can be more important than total RUP supplementation.     

Effect of low and high fill diets on dry matter intake, milk production, and reproductive performance during early lactation

Feedstuffs analyzed for rate and extent of ruminal neutral detergent fiber disappearance were used to formulate two diets that differed for predicted time required for ruminal clearance of neutral detergent fiber. Diets with slow and fast estimated disappearance rate of neutral detergent fiber were termed and high and low fill, respectively. For both diets, crude protein, acid detergent fiber, neutral detergent fiber, net energy of lactation, and soluble protein were similar. Twenty-eight lactating cows were limit fed the rations 2 wk prior to calving, then fed for ad libitum consumption until 8 wk after calving. Cows fed low fill produced more milk (30.3 vs. 26.3 kg) and milk protein (.97 vs. .78 kg) and had higher incidence of short estrous cycles and fewer acyclic cows by 8 wk postpartum than cows offered high fill. Dry matter intake, fat-corrected milk yield, daily fat production, and solids-not-fat did not differ between diets. Rumen fermentation measurements for pH and ammonia-nitrogen concentrations were also not different between diets. Cows fed low fill tended to have higher rates of solids and liquid turnover and lower total dry matter in the rumen compared with cows fed high fill. Low ruminal pH on both diets as well as other physiological mechanisms may have been responsible for failure of rates of neutral detergent fiber disappearance to affect intake of dry matter.     

Protected methionine supplementation with extruded blend of soybeans and soybean meal for dairy cows

Methionine may be the first amino acid limiting milk production in early lactation cows. To evaluate this further, 23 high producing Holstein cows (9 multiparous and 14 primiparous) were fed an extruded blend of soybeans and soybean meal (40:60) without or with 15 g of added DL-methionine as 50 g of ruminally protected methionine product during wk 4 to 16 postpartum. Cows were fed a 15.8% crude protein total mixed ration consisting of 30% (dry basis) corn silage, 15% alfalfa hay, and 55% concentrate mix. Covariant-adjusted yields of milk (35.3 and 33.9 kg/d) and solids-corrected milk (29.3 and 28.2 kg/d) were lower for cows fed ruminally protected methionine, whereas yields of 4% fat-corrected milk (28.2 and 27.4 kg/d) were similar. Percentages of fat (2.68 and 2.69) and solids-not-fat (8.82 and 8.83) were similar, and percentages of protein (2.86 and 2.90) were higher from cows fed supplemental methionine. Dry matter intakes (20.5 and 21.6 kg/d) were higher for cows fed ruminally protected methionine. Methionine concentrations in arterial and venous serum were elevated slightly by feeding supplemental methionine. Although methionine was still the first-limiting amino acid as calculated by two different methods, supplementation of this diet with ruminally protected methionine did not increase production of early lactation cows.     

Effects of a xylanase-rich enzyme on intake,milk production,and digestibility of dairy cows fed a diet containing a high proportion of bermudagrass silage

We previously reported that milk production in dairy cows was increased by adding a specific xylanase-rich exogenous fibrolytic enzyme (XYL) to a total mixed ration (TMR) containing 10% bermudagrass silage (BMD). Two follow-up experiments were conducted to examine whether adding XYL would increase the performance of dairy cows consuming a TMR containing a higher (20%) proportion of BMD (Experiment 1) and to evaluate the effects of XYL on in vitro fermentation and degradability of the corn silage, BMD, and TMR (Experiment 2). In Experiment 1, 40 lactating Holstein cows in early lactation (16 multiparous and 24 primiparous; 21 ± 3 d in milk; 589 ± 73 kg of body weight) were blocked by milk yield and parity and randomly assigned to the Control and XYL treatments. The TMR contained 20% BMD, 25% corn silage, 8% wet brewer's grain, and 47% concentrate mixture in the dry matter (DM). Cows were fed the XYL-treated or untreated experimental TMR twice per day for 10 wk after a 9-d covariate period. In Experiment 2, ruminal fluid was collected from 3 cannulated lactating Holstein cows fed a diet containing 20% bermudagrass haylage, 25% corn silage and 55% concentrate. In Experiment 1, compared with Control, application of XYL did not affect DM intake (24.0 vs. 23.7 kg/d), milk yield (35.1 vs. 36.2 kg/d), fat-corrected milk yield (36.1 vs. 36.9 kg/d), or yields of milk fat (1.29 vs. 1.31 kg/d) or protein (1.07 vs. 1.08 kg/d). However, intake of neutral detergent fiber (4.67 vs. 4.41 kg/d) tended to increase with XYL; consequently, milk protein concentration was increased by XYL (3.02 vs. 2.95%). Feed efficiency tended to be lower in cows fed XYL (1.57 vs. 1.52 kg of fat-corrected milk/kg of DM intake) compared with Control. In Experiment 2, XYL tended to increase the rate of gas production in the TMR, the molar proportion of propionate for corn silage, and that of valerate for the TMR. In addition, XYL increased in vitro DM, neutral detergent fiber, and acid detergent fiber degradability of BMD and corn silage. Application of XYL to a diet with a relatively high proportion of BMD tended to increase digestible neutral detergent fiber intake, increased milk protein concentration, and in vitro degradability of DM, neutral detergent fiber, and acid detergent fiber. However, XYL did not affect milk production and tended to decrease feed efficiency in early lactation cows.     

The feeding value of extruded corn grain in a corn silage-based ration for high-producing Holstein cows and heifers during mid lactation

The objective of this study was to investigate the feeding value of extruded corn in a corn silage-based ration for high-producing Holstein cows during mid lactation. Sixteen multiparous and 8 primiparous Holstein cows (106 ± 49.7 d in milk; 43.7 ± 5.27 kg of milk/d) were paired based on parity, days in milk, milk production, and body condition score and assigned to 1 of 2 dietary treatments in a randomized block design for 10 wk including a 2-wk adaptation period. Cows were fed a total mixed ration and milked 3 times per day. Diets contained 44% forage (3:1; corn silage:grass silage), 44.7% grain, and either extruded corn (EXC) or finely ground corn (FGC) at 11.3% of ration dry matter. No significant differences were detected in dry matter intake, milk protein yields, fat-corrected milk yields, or body condition score between cows fed FGC and cows fed EXC. Multiparous cows fed EXC produced more milk during wk 3 through 8 with a reduced milk fat content compared with multiparous cows fed FGC. Milk protein content was greater for primiparous cows fed EXC during wk 5 through 8 compared with primiparous cows fed the FGC ration. The major effect of feeding 2.7 kg/d of EXC compared with FGC was an increase in milk production and a reduction in milk fat content for multiparous cows, and an increase in milk protein content for primiparous cows.     

Effects of dietary crude protein concentration and degradability on milk production responses of early, mid, and late lactation diary cows

Three experiments were conducted to investigate the effect of crude protein (CP) concentration and ruminally undegraded protein (RUP) concentration on milk production and composition of dairy cows at three different stages of lactation. Experiments 1, 2, and 3 using 39, 40, and 39 Holstein cows were conducted for cows in early (wk 4 to 14 postpartum), mid (wk 19 to 29), and late (wk 34 to 44) lactation, respectively. Cows were assigned to one of four corn-based diets: high CP, medium RUP (control); low CP, low RUP; low CP, medium RUP; and low CP, high RUP. Percentages of CP in the high and low CP diets were, respectively, 17.4 and 15.2 for Experiment 1, 15.3 and 13.3 for Experiment 2, and 14.2 and 12.6 for Experiment 3. The RUP concentrations (percentages of CP) for low, medium, and high diets averaged 35.5, 41.4, and 46.5%, respectively. For Experiment 1, production of milk, 4% fat-corrected milk, milk fat, and milk protein was increased by the high protein diets versus the low protein diets. Production of milk and fat-corrected milk increased linearly as RUP in the diet increased. During Experiment 2, lactational responses were not affected by treatment. During Experiment 3, dry matter intake, body weight, and body weight change increased for cows fed the high protein diets versus those same measurements for cows fed the low protein diets. Milk fat and milk protein percentage decreased linearly as RUP in the diet increased. Because there was no effect of diet on milk production, decreasing CP in diets fed to cows in mid or late lactation can reduce the cost of the diet and waste N excreted from the cow.     

Prepartum dietary management of energy intake affects postpartum intake and lactation performance by primiparous and multiparous Holstein cows

An experiment was conducted to determine the effect of plane of energy intake prepartum on postpartum performance. Primiparous (n = 24) and multiparous (n = 23) Holsteins were randomly assigned by expected date of parturition to 1 of 3 prepartum energy intakes. A moderate energy diet [1.63 Mcal of net energy for lactation (NE_L)/kg; 15% crude protein (CP)] was fed for either ad libitum intake (OVR) or restricted intake (RES) to supply 150 or 80% of National Research Council (2001) energy requirement, respectively, for dry cows in late gestation. To limit energy intake to 100% of NRC requirement at ad libitum dry matter intake (DMI), chopped wheat straw was included as 31.8% of dry matter (DM) in a control diet (CON; 1.21 Mcal of NE_L/kg of DM; 14% CP). Multiparous and primiparous cows assigned to OVR gained body condition during the dry period [initial body condition score (BCS) = 3.3], but were not overconditioned by parturition (BCS = 3.5). Multiparous cows in the OVR group lost more BCS postpartum than multiparous RES or CON cows. Primiparous cows lost similar amounts of BCS among dietary treatment groups postpartum. Addition of chopped wheat straw to CON diets prevented a large decrease in DMI prepartum in both primiparous and multiparous cows. During the first 3 wk postpartum, DMI as a percentage of BW was lower for multiparous OVR cows than for multiparous RES cows. Prepartum diet effects did not carry over through the entire 8-wk lactation period. Because of greater mobilization of body stores, OVR cows had greater milk fat percentage and greater 3.5% fat-corrected milk yield during the first 3 wk postpartum. Multiparous cows assigned to OVR experienced a 55% decrease in energy balance and primiparous cows a 40% decrease in energy balance during the last 3 wk before parturition, compared with CON or RES cows that had little change. Multiparous cows fed OVR had a greater contribution of energy from body energy reserves to milk energy output than either CON or RES cows. Overfeeding energy prepartum resulted in large changes in periparturient energy balance. Even in the absence of overconditioning, a large change in DMI and energy balance prepartum influenced postpartum DMI and BCS loss, especially for multiparous cows. Chopped wheat straw was effective at controlling energy intake prepartum, although primiparous cows did not achieve predicted DMI. Even so, controlling or restricting energy intake in primiparous cows was not detrimental to lactational performance over the first 8 wk of lactation.     

Fibrolytic enzyme supplements for dairy cows in early lactation.

Twenty multiparous lactating Holstein cows in early lactation were used to investigate effects of exogenous fibrolytic enzyme supplementation on dry matter intake, milk production, and digestibility. Cows were blocked according to parity, expected calving date, and milk yield in the previous lactation, and then randomly assigned after calving to two treatments: control or enzyme. The enzyme mixture, which contained mainly xylanase and cellulase activities (Pro-Mote, Biovance Technol. Inc., Omaha, NE), was added to the concentrate to supply 1.3 g/kg of total mixed ration (dry matter basis). The total mixed rations contained 24% corn silage, 15% alfalfa hay, and 61% barley concentrate (dry matter basis) and were offered for ad libitum intake. Enzyme addition did not affect dry matter intake. However, total digestibility of nutrients, determined using Cr2O3, was dramatically increased by enzyme treatment (dry matter, 61.7 vs. 69.1%; neutral detergent fiber, 42.5 vs. 51.0%; acid detergent fiber, 31.7 vs. 41.9%; crude protein, 61.7 vs. 69.8%). Consequently, milk yield tended to increase (35.9 vs. 39.5 kg/d). Percentage of milk fat was lower, and percentages of milk protein tended to be lower for cows fed a diet supplemented with enzymes, such that component yields were similar for cows fed either diet. Energy deficiency was numerically lower for cows fed a diet supplemented with enzymes than for cows fed the control diet (-3.62 vs. -3.33 Mcal/d). Supplementing dairy cow diets with a fibrolytic enzyme mixture has the potential to enhance milk yield and nutrient digestibility of cows in early lactation without changing feed intake.     

Effect of liquid flavor supplementation of the diet on dairy cows in the transition period

A 9-wk trial was conducted to study the performance of 24 Holstein cows during the transition period (3 wk prepartum to 6 wk postpartum). Cows were assigned to either a control or liquid-flavored (0.52 mL/kg of feed) total mixed ration in a randomized complete block design. The diets contained corn silage, alfalfa haylage, cottonseed, and a grain mix based on ground corn and soybean meal. Cows were fed to ensure 10% orts, and the diet provided (on a dry matter basis) 13% crude protein, 32% acid detergent fiber, 44% neutral detergent fiber, and 1.54 Mcal/kg of NEL prepartum and 17.5% crude protein, 30% acid detergent fiber, 40% neutral detergent fiber, and 1.57 Mcal/kg of NEL postpartum. An additional 2.3 kg of alfalfa hay was fed during the first 5 d postpartum. Weekly means of dry matter intake (DMI), milk yield, milk protein, milk fat, SNF, somatic cell counts, and body weight (BW) were analyzed using a repeated measures procedure. There was no effect of treatment on these variables, and least squares means were 16.9 and 15.7 kg/d for DMI, 38 and 35.3 kg/d for milk yield, 3.10 and 3.11% for milk protein, 3.69 and 3.74% for milk fat, 8.37 and 8.16% for SNF, 1.99 x 10(5) and 4.33 x 10(5) for somatic cell count, and 631 and 651 kg for BW for cows fed control and flavored diets, respectively. Individual cow daily DMI data were fitted to an exponential model describing pre- and postpartum feed consumption [DMI = a - b x e(-c x t), where DMI was measured in kg, a = asymptotic DMI, b = potential fractional increase in DMI, c = fractional rate of increase in DMI, and t = days prior to calving or days in milk]. Fractional rates of increase in DMI were similar: 0.139 and 0.123/d for control and flavored diets, respectively. Data for both groups were separately analyzed using multiple regression with 3.5% fat-corrected milk as the dependent variable and BW and DMI as independent variables. More BW was mobilized per unit increase in 3.5% fat-corrected milk in cows fed the control than in cows fed the flavored diet. Cows fed the control diet tended to be in more negative energy balance during early lactation than cows fed the flavored diet. It was concluded that feeding flavor improved energy balance of cows in early lactation and may reduce the risk of health or reproductive problems.     

Short communication: Effects of feeding purple corn (Zea mays L.) silage on productivity and blood superoxide dismutase concentration in lactating cows

The objective of this study was to evaluate the effects of feeding purple corn (Zea mays L.) silage on productivity and blood superoxide dismutase concentration in lactating cows. We hypothesized that feeding purple corn silage (AX-152; Nagano Animal Industry Experiment Station, Nagano, Japan, and Takii and Co. Ltd., Tokyo, Japan), which is high in anthocyanin content, would increase milk production and blood concentration of superoxide dismutase. We assigned 16 Holstein cows (8 primiparous and 8 multiparous) in mid lactation to 1 of 2 treatments in a randomized block design, with efforts to balance parity, body weight, and days in milk between treatments. Experimental diets contained either purple corn silage [PCS; 31.2% dry matter (DM), 8.4% crude protein, 40.2% neutral detergent fiber, and 26.6% starch] or conventional corn silage (CONT; 30.5% dry matter, 8.7% crude protein, 42.1% neutral detergent fiber, and 26.5% starch) at approximately 32% of diet DM. Both PCS and CONT were ensiled for 5 mo before the study. Treatment diets were fed as total mixed rations ad libitum for 12 wk from February 1 to April 25, 2016. Cows fed the PCS had increased milk yield (31.7 vs. 29.2 kg/d) and blood superoxide dismutase concentrations (9,333 vs. 8,467 U/mL) compared with those fed CONT. However, anthocyanin concentration in the PCS decreased over the 12-wk experiment: 70 mg/kg of DM for the first 4 wk, 20 mg/kg of DM for the second 4 wk, and undetectable for the last 4 wk. We did not detect anthocyanins in the CONT group at any time point. Feeding PCS may increase antioxidant capacity and milk production in dairy cows, but anthocyanin in PCS may be degraded during storage.     

Production effects of extruded soybean meal replacing canola meal in the diet of lactating dairy cows

This study investigated the effects of extruded soybean meal (ESBM) in comparison with canola meal (CM) fed on an equivalent crude protein (CP) basis on lactational performance and ruminal fermentation of dairy cows. Following a 2-wk covariate period, 48 Holstein cows averaging (±SD): 146 ± 46 d in milk (DIM) and 43 ± 7 kg/d milk yield (MY) were assigned 1 of 2 treatment diets in a randomized complete block design experiment, which included a 2-wk period for dietary treatment adaptation before experimental data were collected. Following the adaptation period, samples and experimental data were collected for a total of 7 wk. Cows were blocked based on parity, DIM, and MY. Treatment diets contained 15.8% CM (containing 41.2% CP) or 13.2% ESBM (with 48.7% CP) of total mixed ration dry matter (DM), with similar inclusion of other feed ingredients. The CM diet was supplemented with canola oil, whereas the ESBM diet was supplemented with soybean hulls to achieve similar ether extract and neutral detergent fiber contents between the diets. Urea and rumen-protected Met and Lys were added to both diets to meet or exceed cow recommendations. Whole-ruminal digesta samples were collected from 10 (5 per treatment) ruminally cannulated cows. Eight cannulated cows were removed during the last week of the experiment to participate in another study. Treatment did not affect DM intake and MY or energy-corrected MY of the cows. Energy-corrected MY, apart from experimental wk 5, was similar between treatments. Apart from experimental wk 3 and 7, milk fat concentration and yield were greater for cows fed ESBM compared with CM. In multiparous cows only, milk true protein yield was greater for cows fed CM compared with ESBM. Ruminal concentration of total volatile fatty acids and the molar proportion of acetate were greater for ESBM, and propionate and valerate were greater in cows fed CM. Acetate to propionate ratio was greater for cows fed ESBM versus CM diet. Compared with the CM diet, the ESBM diet increased plasma concentrations of Ile, Leu, and Phe but not the sum of essential AA. Apparent total-tract digestibility of acid detergent fiber was greater in cows fed ESBM relative to CM. In this experiment, CM and ESBM included on an equal CP basis in the diet of dairy cows, resulted in similar DM intake, MY, and feed efficiency.     

Short communication: Effect of increasing levels of corn bran on milk yield and composition

Thirty-nine lactating Holstein cows (23 multiparous and 16 primiparous) were randomly assigned to 1 of 3 dietary treatments in a crossover design. Dietary treatments differed by the proportion of corn bran [10, 17.5, and 25% dry matter (DM); designated as low, medium, and high] replacing corn silage and alfalfa. The corn bran coproduct contained 8.2% moisture and 12.9% crude protein, 30.4% neutral detergent fiber (NDF), and 45.0% nonfiber carbohydrate, 9.9% ether extract, and 0.70% P (DM basis). The low treatment consisted of 15.8% NDF from forage (fNDF) and 33.1% total NDF; the medium treatment consisted of 12.9% fNDF and 32.5% total NDF; and the high diet contained 9.9% fNDF and 31.8% total NDF. Dry matter intake was not affected by treatment. The percent milk fat decreased by 0.26% with the inclusion of corn bran from 10 to 25% of the diet DM, but total milk fat yield was not affected. In comparison, corn bran increased yield of milk protein 0.12 kg/d when bran increased from 10 to 25% of the diet DM. Total milk yield tended to increase when bran increased from 10 to 25% of the diet DM, but no differences were observed on 3.5% fat-corrected milk. Lastly, feed conversion significantly improved with increasing inclusion: 1.39, 1.39, and 1.55 ± 0.05 kg of milk/kg of DMI for low, medium, and high, respectively. Observed effects were likely due to the increase in energy intake associated with increasing levels of corn bran.     

Concurrent and carryover effects of feeding blends of protein and amino acids in high-protein diets with different concentrations of forage fiber to fresh cows. 1. Production and blood metabolites

Because of low feed intake during the first weeks of lactation, dietary concentration of metabolizable protein (MP) must be elevated. We evaluated effects of providing additional rumen-undegradable protein (RUP) from a single source or a blend of protein and AA sources during the first 3 wk of lactation. We also evaluated whether replacing forage fiber (fNDF) or nonforage fiber with the blend affected responses. In a randomized block design, at approximately 2 wk prepartum, 40 primigravid (664 ± 44 kg of body weight) and 40 multigravid (797 ± 81 kg of body weight) Holsteins were blocked by calving date and fed a common diet (11.5% crude protein, CP). After calving to 25 d in milk (DIM), cows were fed 1 of 4 diets formulated to be (1) 20% deficient in metabolizable protein (MP) based on predicted milk production (17% CP, 24% fNDF), (2) adequate in MP using primarily RUP from soy to increase MP concentration (AMP; 20% CP, 24% fNDF), (3) adequate in MP using a blend of RUP and rumen-protected AA sources to increase MP concentration (Blend; 20% CP, 24% fNDF), or (4) similar to Blend but substituting fNDF with added RUP rather than nonforage neutral detergent fiber (Blend-fNDF; 20% CP, 19% fNDF). The blend was formulated to have a RUP supply with an AA profile similar to that of casein. A common diet (17% CP) was fed from 26 to 92 DIM, and milk production and composition were measured from 26 to 92 DIM, but individual dry matter intake (DMI) was measured only until 50 DIM. During the treatment period for both parities, AMP and Blend increased energy-corrected milk (ECM) yields compared with the diet deficient in MP based on predicted milk production (40.7 vs. 37.8 kg/d) and reduced concentrations of plasma 3-methyl-His (4.1 vs. 5.3 µmol/L) and growth hormone (9.0 vs. 11.9 ng/mL). Blend had greater DMI than AMP (17.4 vs. 16.1 kg/d), but ECM yields were similar. Blend had greater plasma Met (42.0 vs. 26.4 µmol/L) and altered metabolites associated with antioxidant production and methyl donation compared with AMP. Conversely, the concentration of total essential AA in plasma was less in Blend versus AMP (837 vs. 935 µmol/L). In multiparous cows, Blend-fNDF decreased DMI and ECM yield compared with Blend (19.2 vs. 20.1 kg/d of DMI, 45.3 vs. 51.1 kg/d of ECM), whereas primiparous cows showed the opposite response (15.3 vs. 14.6 kg/d of DMI, 32.9 vs. 31.4 kg/d of ECM). Greater DMI for multiparous cows fed Blend carried over from 26 to 50 DIM and was greater compared with AMP (23.1 vs. 21.2 kg /d) and Blend-fNDF (21.3 kg/d). Blend also increased ECM yield compared with AMP (49.2 vs. 43.5 kg/d) and Blend-fNDF (45.4 kg/d) from 26 to 92 DIM. Few carryover effects of fresh cow treatments on production were found in primiparous cows. Overall, feeding blends of RUP and AA may improve the balance of AA for fresh cows fed high MP diets and improve concurrent and longer-term milk production in multiparous cows. However, with high MP diets, multiparous fresh cows require greater concentrations of fNDF than primiparous cows.