Effect of dietary sulfur and selenium concentrations on selenium balance of lactating Holstein cows

The effects of dietary sulfate and selenium concentrations on selenium balance in dairy cows were investigated. Midlactation Holstein cows (n = 30) were fed diets containing either 0.1 or 0.3 mg of supplemental Se (from sodium selenate)/kg of dry matter and 0, 0.2, or 0.4% added S from a mix of calcium and magnesium sulfate in a factorial arrangement. The experiment lasted 112 d. Dry matter intake was linearly reduced with increasing S, but the effect was greater when 0.3 mg/kg of Se was fed (significant interaction). Treatment effects for yields of milk, milk fat, and milk protein were similar to those for dry matter intake. Increased dietary S linearly reduced plasma Se concentrations. Increasing dietary S linearly reduced apparent (42.7, 33.1, and 30.1%) and estimated true (50.5, 46.0, and 42.3%) Se digestibility. Excretion of Se via feces (1.6 vs. 2.8 mg/d) and urine (0.5 vs. 1.3 mg/d) was higher and output in milk (0.4 vs. 0.3 mg/d) was lower for cows fed 0.3 mg/kg of Se compared with 0.1 mg/kg, but no Se effect was found for estimated true Se digestibility. Dietary S from sulfate reduced Se balance especially when cows were fed diets with less than 0.3 mg of Se/kg of diet dry matter.     

Effects of source on bioavailability of selenium,antioxidant status,and performance in lactating dairy cows during oxidative stress-inducing conditions

In the current study, we used heat stress (HS) as an oxidative stress model to examine the effects of hydroxy-selenomethionine (HMSeBA), an organic selenium source, on selenium's bioavailability, antioxidant status, and performance when fed to dairy cows. Eight mid-lactation Holstein dairy cows (141 ± 27 d in milk, 35.3 ± 2.8 kg of milk/d, parity 2 or 3) were individually housed in environmental chambers and randomly assigned to 1 of 2 treatments: inorganic Se supplementation (sodium selenite; SS; 0.3 mg of Se/kg of dry matter; n = 4) or HMSeBA supplementation (0.3 mg of Se/kg of dry matter; n = 4). The trial was divided into 3 continuous periods: a covariate period (9 d), a thermal neutral (TN) period (28 d), and a HS period (9 d). During the covariate and TN periods, all cows were housed in TN conditions (20°C, 55% humidity). During HS, all cows were exposed to cyclical HS conditions (32–36°C, 40% humidity). All cows were fed SS during the covariate period, and dietary treatments were implemented during the TN and HS periods. During HS, cows fed HMSeBA had increased Se concentrations in serum and milk, and total Se milk-to-serum concentration ratio compared with SS controls. Superoxide dismutase activity did not differ between Se sources, but we noted a treatment by day interaction in glutathione peroxidase activity as HS progressively reduced it in SS controls, whereas it was maintained in HMSeBA cows. Supplementation with HMSeBA increased total antioxidant capacity and decreased malondialdehyde, hydrogen peroxide, and nitric oxide serum concentrations compared with SS-fed controls. We found no treatment effects on rectal temperature, respiratory rate, or dry matter intake. Supplementing HMSeBA tended to increase milk yield and decrease milk fat percentage. No other milk composition parameters differed between treatments. We observed no treatment effects detected on blood biochemistry, except for a lower alanine aminotransferase activity in HMSeBA-fed cows. These results demonstrate that HMSeBA supplementation decreases some parameters of HS-induced oxidative stress.     

Effect of selenium source on selenium status, neutrophil function, and response to intramammary endotoxin challenge of dairy cows

The effects of feeding dry and early lactation dairy cows diets with selenate or selenized yeast (Se-yeast) on concentrations of Se in serum, milk, and newborn calves, neutrophil function, and inflammatory response were determined. At 60 d before anticipated calving until approximately 30 d in milk (DIM), cows were fed diets that contained 0.3 mg of supplemental Se/kg of DM from sodium selenate or Se-yeast. Diets also contained 0.2% supplemental S (as sulfate) because it has been shown to reduce absorption of Se by dairy cows. The concentration of Se in serum at calving and 28 DIM was about 1.4 times greater for cows fed Se-yeast than for those fed selenate. Serum concentrations decreased 45 and 23% from dry-off to calving for cows fed selenate or Se-yeast, respectively. Selenium concentrations in serum from newborn calves were also about 1.4 times greater when the dams were fed Se-yeast. Concentrations of Se in colostrum and milk were about 1.8 times greater when cows were fed Se-yeast. Blood neutrophils were isolated from cows at 28 DIM and were used in an in vitro kill assay. Selenium treatment did not affect bacterial kill or the percentage of neutrophils that phagocytized bacteria. At approximately 28 DIM, one quarter from each cow was infused with a solution containing endotoxin. Peak body temperature (40.7°C) occurred 6 h postinfusion, and peak somatic cell count (6.5 log₁₀/mL) occurred at 12 h postinfusion. Neither measure was influenced by Se treatment.     

The effects of live yeast supplementation to dairy cows during the hot season on production, feed efficiency, and digestibility

The current study examined the effects of live yeast (LY) supplementation to dairy cows during the summer season on milk production, feed efficiency and ration digestibility. Forty-two dairy cows (14 primiparous and 28 multiparous) were fed either a control lactating diet or supplemented with 1 g of LY (Saccharomyces cerevisiae, Biosaf, Lesaffre) per 4 kg of dry matter consumed. The LY amounts were adjusted twice a week. Four rumen samples were taken from 30 cows in 2-h periods and ammonia concentrations were determined. Fecal grab samples from 30 cows were collected during 3 consecutive days, to determine the apparent digestibility of diets. The daily dry matter intake in the LY group was 2.5% greater compared with the control group (24.7 and 24.1 kg, respectively). The daily average milk yield of the LY group was greater by 1.5 kg (4.1%) compared with the control group (37.8 vs. 36.3 kg, respectively). There were no significant differences in the milk fat and protein percentages, but fat yield was greater in the LY group than in the control. The fat-corrected milk 4% was 2.0 kg (6.1%) greater in the LY group than in the control group (34.8 vs. 32.8 kg, respectively). The efficiency of using dry matter to produce 4% fat-corrected milk was 3.7% greater in the LY group compared with the control group. The ruminal ammonia concentrations after feeding were greater in the control group than in the LY group (151.9 vs. 126.1 mg/l, respectively). No differences were observed among groups in the total tract apparent digestibility of dry matter and other diet components. The pH values in the rumen that were determined in a companion trial using 4 fistulated cows tended to be higher in cows that were supplemented with LY than in the control (6.67 vs. 6.54, respectively). It may be concluded that LY supplementation to dairy cows during the hot season improved the rumen environment in a way that increased the dry matter intake and in consequence enhanced the productivity and efficiency.     

Effect of cobalt supplementation during late gestation and early lactation on milk and serum measures

Thirty-six multiparous cows were assigned to a study to determine the effects of dietary Co supplementation during late gestation and early lactation on concentrations of Co in serum and liver, vitamin B₁₂ concentrations in serum and milk, and milk yield. Nonlactating cows received diets containing 0.15, 0.89, or 1.71 mg/ kg of Co (dry matter basis) from 55 d before parturition, and lactating cows received diets containing 0.19, 0.57, or 0.93 mg/kg of Co (dry matter basis) from parturition through 120 d postpartum. Serum vitamin B₁₂ concentrations declined sharply in all cows between 55 and 20 d prepartum. Dietary Co supplementation tended to cause an increase in the concentration of vitamin B₁₂ in colostrum and milk. Cobalt intake did not affect concentrations of Co in liver or serum, but increased the Co concentration of milk (0.089, 0.120, and 0.130 μg of Co/mL) at 120 days in milk. There was no effect of Co supplementation on dry matter intake or yield of milk and milk components. In conclusion, serum concentrations of vitamin B₁₂ are reduced in the early dry period, and added dietary Co may increase ruminal synthesis of vitamin B₁₂ as indicated by a tendency for increased vitamin B₁₂ concentrations in colostrum and milk of cows supplemented with dietary Co.     

Yeast culture supplementation prevented milk fat depression by a short-term dietary challenge with fermentable starch

Effects of yeast culture on responses to a fermentable starch challenge were evaluated in an experiment with a crossover arrangement of treatments for yeast culture supplementation with 28-d periods and a fermentable starch challenge on the last 2 d of each 28-d period as a split plot within period. Eight ruminally cannulated, midlactation, multiparous Holstein cows (96 ± 14 d in milk) were randomly assigned to treatment sequence. Treatments were yeast culture or control (mix of dry ground corn and soybean meal), top-dressed at 56 g per head per day throughout each period. Diets containing dry ground corn grain were fed from d 1 through 26 of each period. On the last 2 d of each period, the dry ground corn was replaced by finely ground high-moisture corn grain on an equivalent dry matter basis to abruptly increase ruminal fermentability of dietary starch. Response variables were averaged for d 25 and 26 for the dry corn treatment and for d 27 and 28 for the high-moisture corn treatment each period. The fermentable starch challenge decreased dry matter intake by 1.9 kg/d and tended to increase milk yield compared with the dry corn diet. However, effects of the fermentable starch challenge on yield of milk fat varied for the yeast culture and control diets; yield of milk fat decreased from 1.42 to 1.30 kg/d for the control treatment but increased from 1.40 to 1.47 kg/d for the yeast culture treatment. Milk fat concentration tended to decrease from 3.34 to 3.03% during the dietary challenge compared with the base diet for the control treatment but was not affected (mean = 3.32%) by the dietary challenge for the yeast culture treatment. An interaction of treatments was also detected for fat-corrected milk, which increased from 41.0 to 43.0 kg/d for the yeast culture treatment but decreased from 41.6 to 39.8 kg/d for the control diet with the fermentable starch challenge. Frequency of ruminating bouts was decreased by yeast culture compared with control (12.8 vs. 15.7 bouts/d) but not the fermentable starch challenge. No treatment interactions were observed for any measure of ruminal pH, total or individual volatile fatty acid concentration in ruminal fluid, acetate:propionate ratio, or individual fatty acid isomers in milk fat. Yeast culture supplementation may help prevent depression in milk fat during transition to a diet with highly fermentable starch, but the mechanism responsible remains to be elucidated.     

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.     

Varying forage type, metabolizable protein concentration, and carbohydrate source affects manure excretion, manure ammonia, and nitrogen metabolism of dairy cows

Effects of forage source, concentration of metabolizable protein (MP), and type of carbohydrate on manure excretion by dairy cows and production of ammonia from that manure were evaluated using a central composite experimental design. All diets (dry basis) contained 50% forage that ranged from 25:75 to 75:25 alfalfa silage:corn silage. Diets contained 10.7% rumendegradable protein with variable concentrations of undegradable protein so that dietary MP ranged from 8.8 to 12%. Starch concentration ranged from 22 to 30% with a concomitant decrease in neutral detergent fiber. A total of 15 diets were fed to 36 Holstein cows grouped in 6 blocks. Each block was a replicated 3 × 3 Latin square resulting in 108 observations. Manure output (urine and feces) was measured using total collection, and fresh feces and urine were combined into slurries and incubated for 48 h to measure NH₃-N production. Feces, urine, and manure output averaged 50.5, 29.5, and 80.1 kg/d, respectively. Manure output increased with increasing dry matter intake (∼3.5 kg of manure/kg of dry matter intake), increased concentrations of alfalfa (mostly via changes in urine output), and decreased concentrations of starch (mostly via changes in fecal output). The amount of NH₃-N produced per gram of manure decreased with increasing alfalfa because excreted N shifted from urine to feces. Increasing MP increased NH₃-N produced per gram of manure mainly because of increased urinary N, but increased fecal N also contributed to the manure NH₃. Manure NH₃-N production per cow (accounts for effects on manure production and NH₃-N produced per unit of manure) was least and milk protein yields were maximal for diets with high alfalfa (75% of the forage), moderate MP (11% of diet dry matter), and high starch (30% of diet dry matter).     

Short communication: Effects of different selenium supplements on rumen fermentation and apparent nutrient and selenium digestibility of mid-lactation dairy cows

The aim of this study was to evaluate the dose-dependent effects of a hydroxy-analog of selenomethionine (HMSeBA) on rumen fermentation, apparent nutrient digestibility, and total selenium absorption in mid-lactation dairy cows, and to compare the effects with those of sodium selenite (SS). Fifty mid-lactation dairy cows with similar milk yields, days in milk, and parity were randomly assigned to 1 of 5 treatments according to a randomized complete block design. The cows were fed a basal diet containing 0.06 mg/kg dry matter (DM) of Se (control) or the same basal diet supplemented with SS, yielding 0.3 mg of Se/kg of DM (SS-0.3), or HMSeBA, yielding 0.1, 0.3, or 0.5 mg of Se/kg of DM (SO-0.1, SO-0.3, and SO-0.5, respectively), during the experimental period. The final content of Se in control, SS-0.3, SO-0.1, SO-0.3, and SO-0.5 was 0.06, 0.34, 0.15, 0.33, and 0.52 mg of Se/kg of DM. The experiment lasted for 10 wk, with a pretrial period of 2 wk. Supplementation with HMSeBA altered rumen fermentation by linearly increasing total volatile fatty acids and the molar proportions of propionate and butyrate but decreasing rumen pH, ammonia content, and the ratio of acetate to propionate. Compared with SS, HMSeBA enhanced the molar proportion of propionate in the rumen and the apparent digestibility of crude protein, neutral detergent fiber, acid detergent fiber, and selenium. We demonstrated that HMSeBA promoted rumen fermentation, apparent nutrient digestibility, and selenium absorption, implying that HMSeBA has a greater apparent absorption than SS.     

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 μg Se ml⁻¹, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 μg Se ml⁻¹ resulted in a selenium concentration of up to 2 μg Se g⁻¹ (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 μg Se g⁻¹ (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 μg Se g⁻¹ (dry mass), while the selenite-enriched leaves contained approximately 50 μg Se g⁻¹ (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and γ-glutamyl-selenomethyl-selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS.     

Effect of hydroxyselenomethionine on lactation performance,blood profiles,and transfer efficiency in early-lactating dairy cows

The current study investigated the effects of hydroxyselenomethionine (HMBSe), a novel organic selenium (Se) additive, on lactation performance, blood profiles, antioxidative status, and transfer efficiency of Se in early-lactation dairy cows. Sixty multiparous early-lactating dairy cows with similar days in milk (57 d; standard deviation = 9.9) and milk yield (36.5 kg/d; standard deviation = 1.42) were fed a basal diet containing 0.04 mg of Se/kg (dry matter basis). These cows were assigned to 1 of 4 groups following a randomized complete block design as follows: control (basal diet) or HMBSe addition (0.1, 0.3, or 0.5 mg of Se/kg of dry matter). The experiment lasted for 13 wk, with the first week as adaptation. The results showed that milk yields (raw, protein, and lactose) and feed efficiency were improved in a quadratic manner following increased dietary HMBSe addition, whereas energy-corrected milk, 4% fat-corrected milk, and total solid yields tended to be enhanced quadratically. In terms of whole-blood variables, red blood cell and white blood cell levels were increased quadratically, whereas hemoglobin concentration increased linearly with increased HMBSe addition. Plasma nonesterified fatty acid concentrations tended to increase linearly along with HMBSe addition. Plasma superoxide dismutase activity increased quadratically with increased HMBSe addition. The total antioxidant capacity in plasma tended to improve quadratically when cows were fed more HMBSe. Moreover, plasma malondialdehyde concentrations of dairy cows tended to decrease in a quadratic manner when dietary HMBSe increased. The Se concentrations in milk, plasma, and milk/plasma ratio increased linearly following increased HMBSe addition. In conclusion, HMBSe improved lactation performance, health status, and milk Se concentrations in early-lactating dairy cows.     

Effects of dietary cation-anion difference on intake, milk yield, and blood components of the early lactation cow

Early lactation Holsteins cows (15 primiparous and 18 multiparous) were offered rations with dietary cation-anion difference, calculated as mEq (Na + K − Cl − S)/100 g of feed dry matter (DCAD:S), of 20, 35, or 50 mEq from d 0 (calving) to 42 d postpartum (August 20, 2000 to January 9, 2001) to determine the effects of increasing DCAD:S on dry matter intake (DMI), milk yield, and blood metabolites. For DCAD:S of 20, 35, and 50, DMI was 3.30, 3.38, 2.96 kg/100 kg of body weight (BW); milk yield was 25.5, 24.2, and 22.4 kg/d, respectively. No differences were observed for concentration or yield of milk fat or milk protein. Serum Ca, P, Mg, Na, K, Cl, cation-anion difference, insulin, and glucose did not differ with DCAD. Serum HCO₃⁻ was 26.07, 25.88, and 27.64 mEq/L for 20, 35, and 50 DCAD:S. Serum Ca, Mg, Na, and K concentrations were greater for primiparous cows (9.52 mg/dL, 2.35 mg/dL, 140.03 mEq/L, 4.66 mEq/L, respectively) than for multiparous cows (9.27 mg/dL, 2.12 mg/dL, 137.63 mEq/L, 4.46 mEq/ L, respectively). A DCAD:S between 23 and 33 mEq/ 100 g of dry matter (DM) appears to be adequate during cool weather for the milk yield that occurred in the present study based on DMI (kg/100 kg of BW), whereas DCAD:S of 50 mEq/100 g of DM may be excessive and could be too alkaline or unpalatable, resulting in decreased DMI (kg/100 kg of BW).     

Effects of feed delivery time on feed intake, milk production, and blood metabolites of dairy cows

The objective of the study was to determine the effects of feed delivery time and its interactions with dietary concentrate inclusion and parity on milk production and on 24-h averages and patterns of feed intake and blood metabolites. Four multiparous and 4 primiparous lactating Holstein cows were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Experimental periods included 14 d of adaptation and 7 d of sampling. A higher concentrate diet with a forage:concentrate ratio (dry matter basis) of 38:62 or a lower-concentrate diet with a forage:concentrate ratio of 51:49 was delivered at either 0900 or 2100 h. During sampling periods, daily feed intakes, as well as feed intakes during 3-h intervals relative to feed delivery, were determined. During 2 nonconsecutive days of the sampling period, jugular blood was sampled every 2 h. Average temperature and relative humidity in the experimental facility were 20.4°C and 68.1%, and the maximum daily air temperature did not exceed 25°C. This data does not suggest that cows were heat-stressed. Changing feed delivery time from 0900 to 2100 h increased the amount of feed consumed within 3 h after feeding from 27 to 37% of total daily intake but did not affect daily dry matter intake. The cows fed at 2100 h had lower blood glucose at 2 h after feeding but greater blood lactate and β-hydroxybutyrate acid at 2 and 4 h after feeding than cows fed at 0900 h. These effects of feed delivery time on the 24-h patterns in blood metabolites may be caused by the greater feed intake during the 3 h after feed delivery of the cows fed at 2100 h. Daily averages of glucose, urea, lactate, and β-hydroxybutyrate acid and nonesterified fatty acids in peripheral blood were not affected by time of feeding. The change in feed delivery time did not affect milk yield and milk protein but increased milk fat percentage from 2.5 to 2.9% and milk fat yield from 0.98 to 1.20 kg/d in multiparous cows, without affecting milk fat in primiparous cows. The interactions between diet and time of feeding on daily feed intake, milk production, and blood metabolites were not significant. The effects of the time of feed delivery on the 24-h patterns in blood metabolites suggest that this time may affect peripheral nutrient availability. Results of this study suggest beneficial effects of feeding at 2100 h instead of at 0900 h on milk fat production of lactating cows, but parity appears to mediate this effect.     

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.     

The effect of feeding dried distillers grains plus solubles on milk production and excretion of urinary purine derivatives

Two studies were performed to evaluate the effects of dried distillers grains with solubles (DDGS) on the lactational performance of dairy cows. The intent of experiment 1 was to evaluate the effects of feeding increasing concentrations of DDGS on the feed intake and production of Holstein dairy cows. Twenty multiparous Holstein cows averaging 76 ± 24 d in milk and 638 ± 68 kg of body weight were randomly assigned to one of five 4 × 4 Latin squares. During each of the 28-d periods, cows were offered 1 of 4 diets: 1) control, 0% DDGS, 2) 10% DDGS, 3) 20% DDGS, or 4) 30% DDGS. For the treatment diets, DDGS replaced a portion of both forages and concentrates. Dry matter intake increased linearly with increasing concentrations of DDGS (21.4, 22.4, 23.0, and 24.0 ± 0.98 kg/d). Similarly, milk production increased linearly (27.4, 28.5, 29.3, and 30.6 ± 1.44 kg/d). The intent of experiment 2 was to evaluate the effect of feeding DDGS on feed intake, milk production, and excretion of urinary purine derivatives (PD). Excretion of PD was used to estimate the effects on rumen microbial crude protein production. Twenty-one multiparous and 13 primiparous Holstein cows, averaging 178 ± 36 d in milk and 651 ± 65 kg of body weight were randomly assigned to 1 of 2 diets in a 3-period crossover design. Cows were offered 1 of 2 rations during each 21-d period. Dietary treatments were either a control (0% DDGS) or 30% dietary dry matter of DDGS. Dry matter intake increased when feeding DDGS (22.8 vs. 24.1 ± 0.74 kg/d for 0 and 30% DDGS, respectively) but milk production, percentages of milk fat and protein, and the ratio of PD to creatinine were not significantly different between the control and DDGS diets. Results of this study suggest a dairy ration may be formulated to contain as much as 30% of dietary dry matter as DDGS.     

Effects of decreasing metabolizable protein and rumen-undegradable protein on milk production and composition and blood metabolites of Holstein dairy cows in early lactation

This study was conducted to evaluate the effects of decreasing dietary protein and rumen-undegradable protein (RUP) on production performance, nitrogen retention, and nutrient digestibility in high-producing Holstein cows in early lactation. Twelve multiparous Holstein lactating cows (2 lactations; 50 ± 7 d in milk; 47 kg/d of milk production) were used in a Latin square design with 4 treatments and 3 replicates (cows). Treatments 1 to 4 consisted of diets containing 18, 17.2, 16.4, and 15.6% crude protein (CP), respectively, with the 18% CP diet considered the control group. Rumen-degradable protein levels were constant across the treatments (approximately 10.9% on a dry matter basis), whereas RUP was gradually decreased. All diets were calculated to supply a postruminal Lys:Met ratio of about 3:1. Dietary CP had no significant effects on milk production or milk composition. In fact, 16.4% dietary CP compared with 18% dietary CP led to higher milk production; however, this effect was not significant. Feed intake was higher for 16.4% CP than for 18% CP (25.7 vs. 24.3 kg/d). Control cows had greater CP and RUP intakes, which resulted in higher concentrations of plasma urea nitrogen and milk urea nitrogen; cows receiving 16.4 and 15.6% CP, respectively, exhibited lower concentrations of milk urea nitrogen (15.2 and 15.1 vs. 17.3 mg/dL). The control diet had a significant effect on predicted urinary N. Higher CP digestibility was recorded for 18% CP compared with the other diets. Decreasing CP and RUP to 15.6 and 4.6% of dietary dry matter, respectively, had no negative effects on milk production or composition when the amounts of Lys and Met and the Lys:Met ratio were balanced. Furthermore, decreasing CP and RUP to 16.4 and 5.4%, respectively, increased dry matter intake.     

Short communication: Effects of molasses supplementation on performance of lactating cows fed high-alfalfa silage diets

Twelve Holstein cows were used in a replicated Latin square experiment to determine the effect of adding dried molasses to high-alfalfa silage diets on dairy cow performance. Three isonitrogenous diets were formulated with a 68:32 forage:concentrate ratio, with alfalfa silage as the only forage source. Dietary treatments were a control diet with no added molasses and 3 and 6% dried molasses diets. Three lactating Holstein cows fitted with ruminal cannulas were used to determine the effects of dietary treatments on ruminal fermentation. Dietary treatments had no effect on dry matter (average 23.3 kg/d), crude protein (average 4.4 kg/d), or neutral detergent fiber (average 7.4 kg/d) intake. Milk yield, energy-corrected milk (average 35.4 kg/d), and 4% fat-corrected milk (average 33.8 kg/d) were not influenced by dietary treatments. Cows fed the control diet produced milk with less milk urea nitrogen concentration than those fed molasses-supplemented diets. Ruminal pH, NH₃-N concentration, and total volatile fatty acids were not different among dietary treatments. The molar proportion of acetate linearly increased, whereas the molar proportion of propionate linearly decreased as the level of dried molasses increased. It was concluded that addition of dried molasses to high-alfalfa silage diets at 6% of the diet (dry matter basis) increased milk urea nitrogen but had no effect on animal performance.     

Evaluation of catfish oil as a feedstuff for lactating Holstein cows

The objective of this study was to evaluate catfish oil (CFO) as a dietary ingredient for lactating Holstein cows. Twelve multiparous Holstein cows (6 fitted with a rumen cannula and 6 noncannulated cows), arranged in a 3 × 3 Latin square design replicated 4 times, were used to evaluate CFO as a dietary ingredient for lactating Holstein cows. Each period lasted 27 d with the last 13 d used for data collection. Dietary treatments were 0, 1.5, and 3% CFO (dry matter basis). Orally dosing with chromium oxide powder was used as an external inert marker for calculation of apparent dry matter and nutrient digestion coefficients. Ruminal fluid was collected hourly for 8 h after feeding to measure pH and volatile fatty acids. Intake of dry matter increased as intake of CFO increased (23.0, 24.4, and 25.4 kg/d). Production of milk was unchanged by the feeding of CFO (29.0, 29.0, and 29.4 kg/d). Concentrations of milk fat (3.57, 3.60, and 3.48%) and protein (3.21, 3.18, and 3.23%) were unchanged by feeding CFO. Concentrations of plasma glucose (57.8, 55.1, and 56.0 mg/100 mL), urea nitrogen (11.6, 11.0, and 12.0 mg/100 mL), and insulin (0.55, 0.53, and 0.57 ng/mL) were not affected by dietary treatments. Average ruminal fluid pH decreased (6.40, 6.20, and 6.15), as did the molar proportions of acetate (64.5, 64.2, and 63.4%), as dietary concentration of CFO increased. The molar proportions of propionate increased (19.4, 20.0, and 20.4%) as did that of butyrate (12.0, 12.4, and 12.5%) as intake of CFO increased. Ruminal protozoa numbers were unchanged by treatments. Apparent digestibility coefficients of dry matter, crude protein, neutral detergent fiber, and acid detergent fiber were increased by addition of CFO. In situ lag, rate, and extent of corn silage dry matter digestion were not affected by the inclusion of CFO. However, in situ digestion rate of neutral detergent fiber was increased (0.023, 0.024, and 0.029 h⁻¹) with increasing intake of CFO. In a second study involving 190 Holstein cows, those fed CFO at 1.8% of dietary dry matter produced 1.2 kg more milk/d than those not fed CFO, along with an increase in milk protein concentration. Catfish oil can be a viable lipid source for dairy cows when fed at up to 3% of the dietary dry matter.     

Transfer of dietary selenium to milk.

Twenty-five lactating cows were used in groups of five to study the amounts of dietary selenium transferred to milk. Amounts of dietary selenium varied from deficient to five times the adequate concentration and ranged between 41 ppb and 828 ppb. Sodium selenite and brewers grains, a rich naturally occurring source of selenium, supplied supplemental selenium. Selenium in milk and plasma were related to the amount consumed, but the response was nonlinear since 4.8% of the added selenium was transferred to milk with a deficient diet but only .9% of the amount of added selenium was in milk of cows consuming diets adequate in selenium. Nineteen percent of the selenium furnished in brewers grains appeared in the milk when the ration was deficient in selenium. The small amounts of selenite selenium transferred from the diet to milk were too little (5.5 micrograms/kg) to be a potential hazard to human health when a diet containing .1 to .2 ppm of selenium was fed to dairy cows, an amount sufficient to meet the cow's dietary needs.     

Replacing corn silage with different forage millet silage cultivars: Effects on milk yield,nutrient digestion,and ruminal fermentation of lactating dairy cows

This study investigated the effects of dietary replacement of corn silage (CS) with 2 cultivars of forage millet silages [i.e., regular millet (RM) and sweet millet (SM)] on milk production, apparent total-tract digestibility, and ruminal fermentation characteristics of dairy cows. Fifteen lactating Holstein cows were used in a replicated 3 × 3 Latin square experiment and fed (ad libitum) a high-forage total mixed ration (68:32 forage:concentrate ratio). Dietary treatments included CS (control), RM, and SM diets. Experimental silages constituted 37% of each diet DM. Three ruminally fistulated cows were used to determine the effect of dietary treatments on ruminal fermentation and total-tract nutrient utilization. Relative to CS, RM and SM silages contained 36% more crude protein, 66% more neutral detergent fiber (NDF), and 88% more acid detergent fiber. Cows fed CS consumed more dry matter (DM; 24.4 vs. 22.7 kg/d) and starch (5.7 vs. 3.7 kg/d), but less NDF (7.9 vs. 8.7 kg/d) than cows fed RM or SM. However, DM, starch and NDF intakes were not different between forage millet silage types. Feeding RM relative to CS reduced milk yield (32.7 vs. 35.2 kg/d), energy-corrected milk (35.8 vs. 38.0 kg/d) and SCM (32.7 vs. 35.3 kg/d). However, cows fed SM had similar milk, energy-corrected milk, and solids-corrected milk yields than cows fed CS or RM. Milk efficiency was not affected by dietary treatments. Milk protein concentration was greatest for cows fed CS, intermediate for cows fed SM, and lowest for cows fed RM. Milk concentration of solids-not-fat was lesser, whereas milk urea nitrogen was greater for cows fed RM than for those fed CS. However, millet silage type had no effect on milk solids-not-fat and milk urea nitrogen levels. Concentrations of milk fat, lactose and total solids were not affected by silage type. Ruminal pH and ruminal NH₃-N were greater for cows fed RM and SM than for cows fed CS. Total-tract digestibility of DM (average = 67.9%), NDF (average = 53.9%), crude protein (average = 63.3%), and gross energy (average = 67.9%) were not influenced by dietary treatments. It was concluded that cows fed CS performed better than those fed RM or SM likely due to the higher starch and lower NDF intakes. However, no major differences were noted between the 2 forage millet silage cultivars.