Short communication: Production performance and nutrient digestibility of lactating dairy cows fed diets with and without addition of a live-yeast supplement

The objective of this study was to evaluate the use of a live-yeast product when feeding relatively high-forage diets to high-producing cows in mid lactation. Eight primiparous [607 ± 43 kg of body weight (BW) and 130 ± 16 d in milk (DIM) at the beginning of the experiment] and 16 multiparous (706 ± 63 kg of BW and 137 ± 22 DIM at the beginning of the experiment) Holstein cows were blocked by parity and DIM, and randomly assigned to 1 of 2 diets (control vs. yeast) for a 12-wk period according to a randomized complete block design. The formulated diets contained 50.4% corn silage, 10.4% alfalfa hay, and 39.2% concentrate. The yeast diet was formulated to provide approximately 5.4 × 10¹¹ cfu/d of Saccharomyces cerevisiae (BeneSacc; Global Nutritech Biotechnology LLC, Richmond, VA). Total-tract nutrient digestibility was estimated using 240-h undigested neutral detergent fiber (NDF) as an internal marker. Supplementing live yeast to lactating dairy cows did not affect dry matter intake (25.0 kg/d), milk yield (38.6 kg/d), milk fat concentration (4.78%), milk fat yield (1.83 kg/d), milk protein concentration (3.09%), milk protein yield (1.18 kg/d), milk lactose concentration (4.79%), milk lactose yield (1.84 kg/d), BW gain (?0.05 kg/d), or body condition score gain (0.16 units). The digestibility of dry matter was greater for the control treatment than for the yeast treatment (69.3 and 67.1%, respectively), but the digestibilities of crude protein (61.5%), NDF (40.5%), and starch (98.6%) were not affected by treatment. In conclusion, supplementation of live yeast did not affect production performance or nutrient digestibility of high-producing cows in mid lactation. The reasons for the lack of effect are not clear, but an evaluation of interactions between yeast and rumen buffer supplementation is warranted.     

Effect of palmitic acid-enriched supplements containing stearic or oleic acid on nutrient digestibility and milk production of low- and high-producing dairy cows

We evaluated the effects of fatty acid (FA) supplement blends containing 60% palmitic acid (C16:0) and either 30% stearic acid (C18:0) or 30% oleic acid (cis-9 C18:1) on nutrient digestibility and milk production of low- and high-producing dairy cows. Twenty-four multiparous Holstein cows [118 ± 44 d in milk (DIM)] were divided into 2 blocks by milk production and then randomly assigned to treatment sequence in four 3 × 3 Latin squares within production level, balanced for carryover effects in three consecutive 21-d periods. Cows were blocked by milk yield and assigned to 1 of 2 groups (n = 12 per group): (a) low group (42.5 ± 3.54 kg/d; 147 ± 42 DIM) and (b) high group (55.8 ± 3.04 kg/d; 101 ± 34 DIM). Commercially available fat supplements were combined to provide treatments that consisted of the following: (1) control (CON; diet with no supplemental FA), (2) FA supplement blend containing 60% C16:0 and 30% C18:0 (PA+SA), and (3) FA supplement blend containing 60% C16:0 and 30% cis-9 C18:1 (PA+OA) The FA blends were fed at 1.5% of dry matter (DM) and replaced soyhulls from CON. Preplanned contrasts were (1) overall effect of FA treatments [CON vs. the average of the FA treatments (FAT); 1/2 (PA+SA + PA+OA)], and (2) effect of FA supplement (PA+SA vs. PA+OA). Regardless of production level, overall FAT reduced DMI compared with CON. Also, regardless of level of milk production, PA+OA increased total-tract FA digestibility compared with PA+SA. Treatment by production level interactions were observed for neutral detergent fiber (NDF) digestibility, total FA intake, and the yields of 3.5% fat-corrected milk (FCM), energy-corrected milk (ECM), and milk fat. In low-producing cows, FAT increased DM and NDF digestibility compared with CON. In high-producing cows PA+SA increased DM and NDF digestibility compared with PA+OA. In low-producing cows, PA+SA increased 3.5% FCM, ECM, and milk fat yield compared with PA+OA. However, in high-producing cows PA+OA tended to increase 3.5% FCM compared with PA+SA. In conclusion, low-producing cows responded better to a FA blend containing 60% C16:0 and 30% C18:0, whereas high-producing dairy cows responded more favorably to a FA blend containing 60% C16:0 and 30% cis-9 C18:1. However, further research is required to validate our observations that higher-yielding cows have improved production responses when supplemented with cis-9 C18:1 compared with C18:0.     

Effects of forage neutral detergent fiber and yeast culture on performance of cows during early lactation

Sixty Holstein cows were assigned to two treatments at 21 d before calving and were group-fed a prepartum diet with or without yeast culture. After parturition, cows were individually fed one of five treatments for 140 d: 1) 21% forage neutral detergent fiber (NDF) without yeast culture, 2) 21% forage NDF with yeast culture, 3) 17% forage NDF without yeast culture, 4) 17% forage NDF with yeast culture, and 5) 25% forage NDF with yeast culture for 30 d and then switched to diet 4 for 110 d. Cows fed yeast culture prepartum were also fed yeast culture postpartum (60 g/d). A quadratic increase to 25, 21, and 17% forage NDF occurred during the first 30 d in milk (DIM) for dry matter intake, milk yield, and milk protein yield. No differences were observed for yeast culture or interaction of yeast culture and forage NDF for the first 30 DIM. Feeding 17 versus 21% forage NDF increased milk protein percentage and tended to increase dry matter intake as a percentage of body weight from 31 to 140 DIM. During this period, yeast culture tended to increase milk fat percentage and appeared to have positive effects on dry matter intake, milk yield, and milk fat yield when supplemented to diets with 21% forage NDF but not with 17% forage NDF. Feeding 17% forage NDF may be too low for the first 30 DIM but may improve animal performance after 30 DIM compared to 21% forage NDF.     

Effects of calcium salts of palm fatty acids on nutrient digestibility and production responses of lactating dairy cows: A meta-analysis and meta-regression

Our primary objective was to perform a meta-analysis and meta-regression to evaluate the effects of diets supplemented with calcium salts of palm fatty acids (CSPF) compared with nonfat supplemented control diets (CON) on nutrient digestibility and production responses of lactating dairy cows. Our secondary objective was to perform a meta-analysis to evaluate whether experimental design affects production responses to supplemental CSPF. The data set was formed from 33 peer-reviewed publications with CSPF supplemented at ≤3% diet dry matter. We analyzed the interaction between experimental design (continuous vs. change-over) and treatments (CON vs. CSPF) to evaluate whether experimental design affects responses to CSPF (Meta.1). Regardless of experimental design, we evaluated the effects of CSPF compared with CON on nutrient digestibility and production responses of lactating dairy cows by meta-analysis (Meta.2) and meta-regression (Meta.3) approaches. In Meta.1, there was no interaction between treatments and experimental design for any variable. In Meta.2, compared with CON, CSPF reduced dry matter intake [DMI, 0.56 ± 0.21 kg/d (±SE)] and milk protein content (0.05 ± 0.02 g/100 g), increased neutral detergent fiber (NDF) digestibility (1.60 ± 0.57 percentage units), the yields of milk (1.53 ± 0.56 kg/d), milk fat (0.04 ± 0.02 kg/d), and 3.5% fat corrected milk (FCM, 1.28 ± 0.60 kg/d), and improved feed efficiency [energy corrected milk (ECM)/DMI, 0.08 kg/kg ± 0.03]. There was no effect of treatment for milk protein yield, milk fat content, body weight, body weight change, or body condition score. Compared with CON, CSPF reduced the yield of de novo milk fatty acids (FA) and increased the yields of mixed and preformed milk FA. In Meta.3, we observed that each 1-percentage-unit increase of CSPF in diet dry matter reduced DMI, increased NDF digestibility, tended to increase FA digestibility, increased the yields of milk, milk fat, and 3.5% FCM, reduced the content of milk protein, reduced the yield of de novo milk FA, and increased the yields of mixed and preformed milk FA. In conclusion, our results indicate no reason for the restrictive use of change-over designs in CSPF supplementation studies or meta-analysis. Feeding CSPF increased NDF digestibility, tended to increase FA digestibility, and increased the yields of milk, milk fat, and 3.5% FCM. Additionally, CSPF increased milk fat yield by increasing the yields of mixed and preformed milk FA.     

Effects of alfalfa hay of varying fiber fed at 35 or 50% of diet on lactation and nutrient utilization by dairy cows.

Five alfalfa hays (four from Arizona and one from California), varying in percentages of ADF (26, 28, 32, and 38%), were fed to 40 lactating Holstein cows averaging 90 DIM. Cows were in 10 groups of 4 cows each; groups were based on 14-d pretreatment milk yield. Each hay was included in TMR to provide 50 or 35% of DM. Diets were fed for ad libitum intake for 70 d. Feeding behavior of 2 cows per treatment was electronically monitored for 14 d. Total tract digestibilities of DM, ADF, and NDF were determined using Cr2O3, and ruminal in situ loss of DM, ADF, and NDF of hays was estimated using 4 cows fitted with ruminal fistulas. Dry matter intake, 3.5% FCM, changes in BW, rectal temperatures, and milk composition (except milk fat) were not affected by ADF in hays or concentrate percentage. However, milk yield decreased as ADF in hay increased, particularly at 50% concentrate. At 50% concentrate, milk yield of cows fed hays of 26 to 28% ADF averaged 30.7 kg/d, and the mean for cows fed 32 and 38% ADF hays was 27.6 kg/d. Milk fat percentages tended to be lower on higher concentrate. Eating time was longer as hay ADF increased and tended to decrease on high concentrate, but there were no significant effects of treatment on number or length of meals. In situ disappearance of DM, ADF, and NDF decreased as hay ADF increased, but total tract digestibilities of ADF and NDF were greater in hay of higher fiber content, particularly in cows fed 35% hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of diet fermentability and supplementation of 2-hydroxy-4-(methylthio)-butanoic acid and isoacids on milk fat depression: 1. Production,milk fatty acid profile,and nutrient digestibility

The objectives of this experiment were to determine the effects of increased diet fermentability and polyunsaturated fatty acids (FA) with or without supplemental 2-hydroxy-4-(methylthio)-butanoic acid (HMTBa), isoacids (IA; isobutyrate, 2-methylbutyrate, isovalerate, and valerate) or the combination of these on milk fat depression (MFD). Ten Holstein cows (194 ± 58 DIM, 691 ± 69 kg BW, 28 ± 5 kg milk yield) were used in a replicated 5 × 5 Latin square design. Treatments included a high-forage control diet (HF-C), a low-forage control diet (LF-C) causing MFD by increasing starch and decreasing neutral detergent fiber (NDF), the LF-C diet supplemented with HMTBa at 0.11% (28 g/d), the LF-C diet supplemented with IA at 0.24% of dietary dry matter (60 g/d), and the LF-C diet supplemented with HMTBa and IA. Preplanned contrasts were used to compare HF-C versus LF-C and to examine the main effects of HMTBa or IA and their interactions within the LF diets. Dry matter intake was greater for LF-C versus HF-C, but milk yield remained unchanged. The LF-C diet decreased milk fat yield (0.87 vs. 0.98 kg/d) but increased protein yield compared with HF-C. As a result, energy-corrected milk was lower (28.5 vs. 29.6 kg/d) for LF-C versus HF-C. Although the concentration of total de novo synthesized FA in milk fat was not affected, some short- and medium-chain FA were lower for LF-C versus HF-C, but the concentrations of C18 trans-10 isomers were not different. Total-tract NDF apparent digestibility was numerically lower (42.4 vs. 45.6%) for LF-C versus HF-C. As the main effects, the decrease in milk fat yield observed in LF-C was alleviated by supplementation of HMTBa through increasing milk yield without altering milk fat content and by IA through increasing milk fat content without altering milk yield so that HMTBa or IA, as the main effects, increased milk fat yield within the LF diets. However, interactions for milk fat yield and ECM were observed between HMTBa and IA, suggesting no additive effect when used in combination. Minimal changes were found on milk FA profile when HMTBa was provided. However, de novo synthesized FA increased for IA supplementation. We detected no main effect of HMTBa, IA, and interaction between those on total-tract NDF digestibility. In conclusion, the addition of HMTBa and IA to a low-forage and high-starch diet alleviated moderate MFD. Although the mechanism by which MFD was alleviated was different between HMTBa and IA, no additive effects of the combination were observed on milk fat yield and ECM.     

Effects of flunixin meglumine on pyrexia and bioenergetic variables in postparturient dairy cows

Study objectives were to determine whether a nonsteroidal antiinflammatory drug would reduce parturition-induced inflammation and fever and consequently improve appetite, bioenergetic parameters, and production variables in transitioning dairy cows. Multiparous cows (n = 26) were randomly assigned to 1 of 2 treatments beginning at parturition: 1) flunixin meglumine (FM; 2.2 mg/kg of BW; Banamine, 50 mg/mL, Schering-Plough Animal Health, Kenilworth, NJ), or 2) saline (control) at 2.0 mL/45.5 kg of BW. All treatments were administrated i.v. daily for the first 3 d in milk (DIM). Individual milk yield and dry matter intake (DMI) were recorded daily for the first 35 DIM. Rectal temperature was measured daily at 0700 and 1600 h for the first 7 DIM. Milk composition was determined on 2, 7, 14, 21, 28, and 35 DIM and blood plasma was collected on 1, 2, 3, 4, 7, 14, 21, 28, and 35 DIM. Body weight and body condition score were determined on −7, 1, 7, 14, 21, 28, and 35 DIM. Flunixin meglumine treatment slightly increased rectal temperature (38.99 vs. 38.76°C) during the first 7 DIM and reduced overall DMI (22.04 vs. 19.48 kg/d), but there were no treatment differences in overall milk yield (35.2 kg/d), 3.5% fat-corrected milk (37.6 kg/d), energy-corrected milk (37.7 kg/d), DMI (2.97% of BW), or overall energy balance (−2.32 Mcal/d). There were no treatment differences in milk fat (3.91%), protein (3.32%), or lactose (4.57%). Treatment had no effect on plasma glucose (66.5 mg/dL) or nonesterified fatty acids (553 μEq/L), but plasma urea nitrogen tended to be less in FM-treated cows (16.4 vs. 14.5 mg/dL). Daily FM administration to cows for the first 3 d after parturition slightly increased rectal temperatures by 0.23°C, reduced feed intake, and did not improve production or energetic variables during the first 35 DIM in transition dairy cows.     

Effects of peripartal yeast culture supplementation on lactation performance,blood biomarkers,rumen fermentation,and rumen bacteria species in dairy cows

Feeding yeast culture fermentation products has been associated with improved feed intake and milk yield in transition dairy cows. These improvements in performance have been further described in terms of rumen characteristics, metabolic profile, and immune response. The objective of this study was to evaluate the effects of a commercial yeast culture product (YC; Culture Classic HD, Phibro Animal Health) on performance, blood biomarkers, rumen fermentation, and rumen bacterial population in dairy cows from −30 to 50 d in milk (DIM). Forty Holstein dairy cows were enrolled in a randomized complete block design from −30 to 50 DIM and blocked according to expected calving day, parity, previous milk yield, and genetic merit. At −30 DIM, cows were assigned to either a basal diet plus 114 g/d of ground corn (control; n = 20) or a basal diet plus 100 g/d of ground corn and 14 g/d of YC (n = 20), fed as a top-dress. Cows received the same close-up diet from 30 d prepartum until calving [1.39 Mcal/kg of dry matter (DM) and 12.3% crude protein (CP)] and lactation diet from calving to 50 DIM (1.60 Mcal/kg of DM and 15.6% CP). Blood samples and rumen fluid were collected at various time points from −30 to 50 d relative to calving. Cows fed YC compared with control showed a trend for increased energy-corrected milk (+3.2 kg/d). Lower somatic cell counts were observed in YC cows than in control. We detected a treatment × time interaction in nonesterified fatty acids (NEFA) that could be attributed to a trend for greater NEFA in YC cows than control at 7 DIM, followed by lower NEFA in YC cows than control at 14 and 30 DIM. In the rumen, YC contributed to mild changes in rumen fermentation, mainly increasing postpartal valerate while decreasing prepartal isovalerate. This was accompanied by alterations in rumen microbiota, including a greater abundance of cellulolytic (Fibrobacter succinogenes) and lactate-utilizing bacteria (Megasphaera elsdenii). These results describe the potential benefits of supplementing yeast culture during the late pregnancy through early lactation, at least in terms of rumen environment and performance.     

Controlled trial of the effect of negative dietary cation-anion difference prepartum diets on milk production,reproductive performance,and culling of dairy cows

Our objective was to assess the effects of feeding negative dietary cation-anion difference (DCAD) prepartum diets on milk production, reproductive performance, and culling. Cows from 4 commercial farms in Ontario, Canada were enrolled in a pen-level controlled trial from November 2017 to April 2019. Close-up pens (1 per farm) with cows 3 wk before calving were randomly assigned to a negative DCAD (TRT; ?108 mEq/kg of dry matter; target urine pH 6.0–6.5) or a control diet (CON; +105 mEq/kg of dry matter with a placebo supplement). Each pen was fed TRT or CON for 3 mo (1 period), and then switched to the other treatment for the next period (4 periods per farm). Data from 15 experimental units (8 pen treatments in TRT and 7 in CON), with a total of 1,086 observational units (cows), were included. The effect of treatment on milk yield at the first 3 milk recording tests of lactation was assessed with linear regression models accounting for repeated measures. The risk of pregnancy at first artificial insemination and culling by 30, 60, and 305 d in milk (DIM) were analyzed with logistic regression models, and effects on time to first AI, pregnancy, and culling were assessed with Cox proportional hazards models. All models included treatment, parity, and their interactions, accounting for pen-level randomization and clustering of animals within farm with random effects, giving 10 degrees of freedom for treatment effects. Multiparous cows fed TRT produced more milk at the first (42.0 vs. 38.8 ± 1.2 kg/d) and second (44.2 vs. 41.7 ± 1.3 kg/d) milk tests. However, multiparous cows fed TRT tended to have 0.2 percentage units less milk fat content at these tests. Although multiparous cows fed TRT tended to have greater energy-corrected milk at the first test (least squares means ± standard error: TRT = 46.1 ± 0.9 vs. CON = 43.8 ± 1 kg/d), there were no differences observed in energy-corrected milk at the second or third tests. In primiparous cows, there was no effect of treatment on milk production. Multiparous cows fed TRT had greater pregnancy to first insemination (TRT = 42 ± 3 vs. CON = 32 ± 4%) and tended to have shorter time to pregnancy [hazard ratio (HR) = 1.20; 95% CI: 0.96–1.49]. In primiparous cows fed TRT, time to pregnancy was increased (HR = 0.76; 95% CI: 0.59–0.99). Culling by 30 DIM tended to be less in TRT (3.3 ± 1.1%) than CON (5.5 ± 1.8%). No effect of treatment on culling by 305 DIM was detected in primiparous cows, but in multiparous cows, the TRT diets decreased the odds of culling (21.3 ± 1.9 vs. 31.7 ± 2.8%) and daily risk of culling to 305 DIM (HR = 0.64; 95% CI: 0.46 to 0.89). Under commercial herd conditions, prepartum negative DCAD diets improved milk production and reproductive performance, and reduced culling risk in multiparous cows. In primiparous cows, TRT diets had no effect on milk yield or culling, but increased the time to pregnancy. Our results suggest that negative DCAD diets should be targeted to multiparous cows.     

Milk production and nutrient digestibility responses to triglyceride or fatty acid supplements enriched in palmitic acid

The objective of our study was to evaluate the effects of feeding triglyceride and fatty acid (FA) supplements enriched in palmitic acid (PA; C16:0) on production and nutrient digestibility responses of mid-lactation dairy cows. Fifteen Holstein cows (137 ± 49 d in milk) were randomly assigned to a treatment sequence in a 3 × 3 Latin square design. Treatments consisted of a control diet (CON; no added PA) or 1.5% FA added as either a FA supplement (PA-FA) or a triglyceride supplement (PA-TG). The PA supplements replaced soyhulls, and diets were balanced for glycerol content. Periods were 21 d in length with sample and data collection occurring during the final 5 d. Compared with CON, PA treatments increased dry matter (66.5 vs. 63.9%) and neutral detergent fiber (NDF) apparent digestibility (42.0 vs. 38.2%). Although PA treatments tended to increase 18-carbon FA apparent digestibility (79.1 vs. 77.9%), PA treatments decreased 16-carbon (63.1 vs. 75.8%) and total FA (72.0 vs. 76.5%) apparent digestibilities compared with CON. The PA treatments increased milk fat content (3.60 vs. 3.41%), milk fat yield (1.70 vs. 1.60 kg/d), yield of 16-carbon milk FA (570 vs. 471 g/d), 3.5% fat-corrected milk (47.6 vs. 46.5 kg/d), and energy-corrected milk (47.4 vs. 46.6 kg/d) compared with CON. The PA treatments did not affect dry matter intake (28.5 vs. 29.2 kg/d), milk yield (47.0 vs. 47.4 kg/d), milk protein yield (1.42 vs. 1.45 kg/d), milk lactose yield (2.29 vs. 2.31 kg/d), yield of <16-carbon milk FA (360 vs. 370 g/d), yield of >16-carbon milk FA (642 vs. 630 g/d), body weight (720 vs. 723 kg), or body condition score (3.14 vs. 3.23). We did not observe differences in digestibilities of dry matter, NDF, and 18-carbon FA between PA-TG and PA-FA. In contrast, PA-FA increased 16-carbon (68.6 vs. 57.6%) and total FA apparent digestibility (73.8 vs. 70.1%) compared with PA-TG. This resulted in PA-FA supplementation increasing the apparent digestibility of the PA supplement by ～10 percentage points compared with PA-TG. Compared with PA-TG, PA-FA increased 16-carbon FA intake by 60 g/d, absorbed 16-carbon FA by 86 g/d, and absorbed total FA by 85 g/d. Compared with PA-TG, PA-FA increased dry matter intake (29.1 vs. 27.8 kg/d), yield of 16-carbon milk FA (596 vs. 545 g/d), and tended to increase milk yield (47.6 vs. 46.4 kg/d), milk fat yield (1.70 vs. 1.66 kg/d), and 3.5% fat-corrected milk (48.1 vs. 47.2 kg/d). In conclusion, the production response of dairy cows to PA tended to be greater for a FA supplement compared with a triglyceride supplement. Overall, PA increased NDF digestibility, milk fat yield, energy-corrected milk, and feed efficiency in mid-lactation dairy cows.     

Comparing steam-flaked and pelleted barley grain in a feed-first guided-flow automated milking system for Holstein cows

Provision of a palatable feed in automated milking systems (AMS) is considered an essential motivating factor to encourage voluntary visits to the milking stall. Although the quantity and composition of AMS concentrates have been previously investigated, the form of the concentrate has not been extensively evaluated. The objective of this study was to evaluate the effects of feeding pelleted (PB; 132.9 ± 56 DIM, 47.4 ± 9.51 kg/d milk yield) versus steam-flaked barley (SFB; 133.0 ± 63 DIM, 40.5 ± 8.23 kg/d milk yield) in an AMS on dry matter intake, AMS visits, milk and milk component yield, and partial mixed ration (PMR) feeding behavior. Twenty-nine Holstein cows of varying parities were enrolled in this study. Cows were housed in freestall housing with a feed-first guided-flow barn design; 7 cows were housed in a separate freestall pen to enable individual PMR intake and feeding behavior monitoring. This study was conducted as a 2-way crossover, with two 21-d periods in which each cow received the same basal PMR but was offered 2 kg/d (dry matter basis) of PB or SFB in the AMS. Cows receiving the SFB had fewer voluntary AMS visits (2.71 vs. 2.90 ± 0.051, no./d), tended to have a longer interval between milkings (541.7 vs. 505.8 ± 21.02 min), spent more time in the holding pen before entering the AMS (139.9 vs. 81.2 ± 11.68 min/d), and had lower total box time (19.7 vs. 21.4 ± 0.35 min/d) than cows fed PB. Despite changes in AMS attendance, there were no differences for average milk (44.0 kg/d), fat (1.62 kg/d), and protein (1.47 kg/d) yields or AMS concentrate intake (2.02 kg/d). These behavioral changes indicate that offering SFB as an alternative to PB may reduce motivation for cows to voluntarily enter the AMS.     

Effect of active dry yeast on lactation performance,methane production,and ruminal fermentation patterns in early-lactating Holstein cows

This study was conducted to examine the effect of active dry yeast (ADY) supplementation on lactation performance, ruminal fermentation patterns, and CH₄ emissions and to determine an optimal ADY dose. Sixty Holstein dairy cows in early lactation (52 ± 1.2 DIM) were used in a randomized complete design. Cows were blocked by parity (2.1 ± 0.2), milk production (35 ± 4.6 kg/d), and body weight (642 ± 53 kg) and assigned to 1 of 4 treatments. Cows were fed ADY at doses of 0, 10, 20, or 30 g/d per head for 91 d, with 84 d for adaptation and 7 d for sampling. Although dry matter intake was not affected by ADY supplementation, the yield of actual milk, 4% fat-corrected milk, milk fat yield, and feed efficiency increased quadratically with increasing ADY supplementation. Yields of milk protein and lactose increased linearly with increasing ADY doses, whereas milk urea nitrogen concentration and somatic cell count decreased quadratically. Ruminal pH and ammonia concentration were not affected by ADY supplementation, whereas ruminal concentration of total volatile fatty acid increased quadratically. Digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, nonfiber carbohydrate, and crude protein increased quadratically with increasing ADY supplementation. Supplementation of ADY did not affect blood concentration of total protein, triglyceride, aspartate aminotransferase, and alanine aminotransferase, whereas blood urea nitrogen, cholesterol, and nonesterified fatty acid concentrations decreased quadratically with increasing ADY supplementation. Methane production was not affected by ADY supplementation when expressed as grams per day or per kilogram of actual milk yield, dry matter intake, digested organic matter, and digested nonfiber carbohydrate, whereas a trend of linear and quadratic decrease of CH₄ production was observed when expressed as grams per kilogram of fat-corrected milk and digested neutral detergent fiber. In conclusion, feeding ADY to early-lactating cows improved lactation performance by increasing nutrient digestibility. The optimal ADY dose should be 20 g/d per head.     

Temporal changes in plasma concentrations of hormones and metabolites in pasture-fed dairy cows during extended lactation

This experiment measured variations in plasma concentrations of metabolic hormones and metabolites in cows undergoing extended lactations of up to 670 d at 2 planes of nutrition. Thirty-seven Holstein-Friesian cows that calved in late winter were selected for varying milk yield and then managed for a lactation of 670 d by delaying breeding until approximately 450 d in milk (DIM). Cows grazed fresh pasture supplemented with pasture silage or hay and crushed wheat or triticale grain. Dietary intake was reduced by approximately 1.8 kg (dry matter) grain/cow per day for 19 of the cows from 300 DIM until the end of lactation to assess the effect of restricted energy intake on the persistency of milk production. Samples of blood were collected monthly from each cow to measure plasma concentrations of selected hormones and metabolites. Dietary restriction beyond 300 DIM reduced yields of milk, protein, and fat, but did not alter the proportion of cows reaching the 670-d lactation target. Dietary restriction had no effect on cow BW or plasma concentrations of any hormones or metabolites. Overall, blood plasma concentrations of insulin-like growth factor-I, leptin, and glucose were elevated from 301 to 600 DIM compared with 0 to 300 DIM, whereas concentrations of growth hormone and nonesterified fatty acids were lower after 300 DIM. Plasma concentrations of insulin and prolactin were unaffected by stage of lactation, but prolactin concentrations increased during summer. These changes were consistent with a decrease in milk yield and an increase in the partitioning of nutrients to body tissue gain, primarily adipose tissue, throughout the later stages of the extended lactation. Cows that continued milking beyond 600 DIM had increased plasma concentrations of growth hormone and decreased concentrations of glucose and leptin compared with cows that milked <600 DIM. These differences, coupled with reduced body weight gain, indicated an increased priority for nutrient partitioning to milk production at the expense of body tissue gain throughout the extended lactation period in cows with greater lactation persistency.     

Feeding forages with reduced particle size in a total mixed ration improves feed intake,total-tract digestibility,and performance of organic dairy cows

The optimal utilization of forages is crucial in cattle production, especially in organic dairy systems that encourage forage-based feeding with limited concentrate amounts. Reduction of the particle size of forages is known to improve feed intake and thus might be a viable option to help cows cope with less nutrient-dense feeds. The main aim of this study was to evaluate the effects of reducing forage particle size with a geometric mean of 52 mm (conventional particle size; CON) to 7 mm (reduced particle size; RED) in a high-forage diet (80% of dry matter) on dairy cows' sorting behavior, feed intake, chewing activity, and performance as well as on total-tract nutrient digestibility. Both diets (CON and RED) consisted of 43% grass hay, 37% clover-grass silage, and 20% concentrate and contained roughly 44% NDF, 15% CP, and 0.5% starch (dry matter basis). For CON, particle size was set by mixing all components for 20 min in a vertical feed mixer. The RED diet was treated the same, but before the mixer was filled, forages were chopped (theoretical length of cut = 0.5 cm) and the hay was hammer-milled (sieve size = 2 cm). Four primiparous and 16 multiparous mid-lactating dairy cows were assigned according to milk yield, body weight (BW), days in milk, and parity into 2 groups and fed 1 of the 2 diets for 34 d. The first 13 d were used for diet adaption, followed by data collection of nutrient intake, chewing activity, sorting behavior, milk production, and nutrient digestibility for the last 21 d of the experiment. Seven days before the start of the experiment, data on BW, dry matter intake (DMI), chewing activity, sorting behavior, and milk production were collected for use as covariates. Results showed that the RED diet improved DMI (+1.8 kg/d) and NDF intake (+0.46 kg/d) but decreased intake of physically effective NDF >8 (?3.25 kg/d). The RED-fed cows increased their intake of smaller particles (<19 mm), whereas CON-fed cows sorted for long particles (>19 mm). The RED cows reduced eating and ruminating time per kilogram of DMI by 4.8 and 1.9 min, respectively, suggesting lower mastication efforts. In addition, the RED diet significantly increased apparent total-tract digestibility of nutrients. As a consequence, RED cows' energy-corrected milk yield was higher (27.0 vs. 29.3 kg/d) without affecting milk solids, cow BW, or feed efficiency. In conclusion, the data support a reduction of forage particle size in high-forage diets as a measure to improve energy intake, performance, and hence forage utilization under these feeding conditions.     

Effect of body condition change and health status during early lactation on performance and survival of Holstein cows

Body condition score (BCS) and disease records are commonly available in dairy operations. However, the effect of BCS changes (ΔBCS) considering specific health profiles has not been investigated extensively. The objective of this study was to assess the effects of different levels of ΔBCS on fertility, milk yield, and survival of Holstein cows diagnosed with reproductive disorders (REP; dystocia, twins, retained fetal membranes, metritis, and clinical endometritis), other health disorders (OTH; subclinical ketosis, left displaced abomasum, lameness, clinical mastitis, and respiratory disease), or with no disease events (HLT) within 40 days in milk (DIM). Data included lactation information from 11,733 cows calving between November 2012 and October 2014 in 16 herds across 4 geographical regions in the United States (Northeast, Midwest, Southwest, Southeast). Cows were evaluated for BCS at 5 ± 3 DIM (BCS5) and at 40 ± 3 DIM (BCS40) and the difference between BCS40 and BCS5 was classified as excessive loss of BCS (EL; ΔBCS ≤−0.75), moderate loss (ML; ΔBCS = −0.5 to −0.25), no change (NC; ΔBCS = 0), or gain of BCS (GN; ΔBCS ≥0.25). Multivariable logistic regression was used for assessing potential associations between the outcomes of interest and ΔBCS and health. The effect of the interaction term ΔBCS by health group was not statistically significant for any of the study outcomes. The odds of resumption of ovarian cyclicity (ROC), in GN, NC, and ML cows were 1.94 (95% CI: 1.57–2.40), 1.59 (1.28–1.97), and 1.27 (1.10–1.47) times greater than the odds of ROC in EL cows, respectively. The odds of pregnancy at 150 DIM (P150) in GN cows were 1.61 (1.20–2.17) times greater than the odds of P150 in EL cows. Cows with REP or OTH disorders had smaller odds of ROC compared with HLT cows [REP: OR = 0.65 (0.56–0.76) and OTH: OR = 0.79 (0.68–0.92)]. For pregnancy outcomes, REP cows had smaller odds of pregnancy at the first artificial insemination compared with HLT cows [0.70 (0.58–0.84)]. Similarly, REP cows had smaller odds of being diagnosed pregnant by 150 and 305 DIM compared with HLT cows [P150: 0.73 (0.59–0.87), P305: 0.58 (0.49–0.69)]. Overall, average daily milk within the first 90 DIM was greater in EL (39.5 ± 1.13 kg/d) and ML (38.9 ± 1.11 kg/d) cows than in NC (37.8 ± 1.12 kg/d) and GN (36.2 ± 1.12 kg/d) cows. On the other hand, average daily milk within the first 90 DIM was lower in REP (37.0 ± 1.11 kg/d) cows compared with OTH (38.7 ± 1.12 kg/d) and HLT cows (38.6 ± 1.11 kg/d). The magnitude of ΔBCS and the health status of early lactation cows should be considered when assessing subsequent cow performance and survival.     

Updating predictions of dry matter intake of lactating dairy cows

Our objective was to model dry matter intake (DMI) by Holstein dairy cows based on milk energy (MilkE), body weight (BW), change in BW (ΔBW), body condition score (BCS), height, days in milk (DIM), and parity (primiparous and multiparous). Our database included 31,631 weekly observations on 2,791 cows enrolled in 52 studies from 8 states of the United States, mostly in the Upper Midwest. The means ± standard deviations of these variables were 24 ± 5 kg of DMI, 30 ± 6 Mcal of MilkE/d, 624 ± 83 kg of BW, 0.24 ± 1.50 kg of ΔBW/d, 3.0 ± 0.5 BCS, 149 ± 6 cm height, and 102 ± 45 DIM. Data analysis was performed using a mixed-effects model containing location, study within location, diet within study, and location and cow within study as random effects, whereas the fixed effects included the linear effects of the covariates described previously and all possible 2-way interactions between parity and the other covariates. A nonlinear (NLIN) mixed model analysis was developed using a 2-step approach for computational tractability. In the first step, we used a linear (LIN) model component of the NLIN model to predict DMI using only data from mid-lactation dairy cows (76–175 DIM) without including information on DIM. In the second step, a nonlinear adjustment for DIM using all data from 0 to 368 DIM was estimated. Additionally, this NLIN model was compared with an LIN model containing a fourth-order polynomial for DIM using data throughout the entire lactation (0–368 DIM) to assess the utility of an NLIN model for the prediction of DMI. In summary, a total of 8 candidate models were evaluated as follows: 4 ways to express energy required for maintenance (BW, BW^0.75, BW adjusted for a BCS of 3, and BW^0.75 adjusted for a BCS of 3) × 2 modeling strategies (LIN vs. NLIN). The candidate models were compared using a 5-fold across-studies cross-validation approach repeated 20 times with the best-fitting model chosen as the proposed model. The metrics used for evaluation were the mean bias, slope bias, concordance correlation coefficient (CCC), and root mean squared error of prediction (RMSEP). The proposed prediction equation was DMI (kg/d) = [(3.7 + parity × 5.7) + 0.305 × MilkE (Mcal/d) + 0.022 × BW (kg) + (?0.689 + parity × ?1.87) × BCS] × [1 – (0.212 + parity × 0.136) × exp^{(?0.053 × DIM)}] (mean bias = 0.021 kg, slope bias = 0.059, CCC = 0.72, and RMSEP = 2.89 kg), where parity is equal to 1 if the animal is multiparous and 0 otherwise. Finally, the proposed model was compared against the Nutrient Requirements of Dairy Cattle (2001) prediction equation for DMI using an independent data set of 9,050 weekly observations on 1,804 Holstein cows. The proposed model had smaller mean bias and RMSEP and higher CCC than the Nutrient Requirements of Dairy Cattle equation to predict DMI and has potential to improve diet formulation for lactating dairy cows.     

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.     

Effects of feeding rumen-protected methionine pre- and postpartum in multiparous Holstein cows: Lactation performance and plasma amino acid concentrations

Objectives were to evaluate the effect of feeding rumen-protected methionine (RPM) in pre- and postpartum total mix ration (TMR) on lactation performance and plasma AA concentrations in dairy cows. A total of 470 multiparous Holstein cows [235 cows at University of Wisconsin (UW) and 235 cows at Cornell University (CU)] were enrolled approximately 4 wk before parturition, housed in close-up dry cow and replicated lactation pens. Pens were randomly assigned to treatment diets (pre- and postpartum, respectively): UW control (CON) diet = 2.30 and 2.09% of Met as percentage of metabolizable protein (MP) and RPM diet = 2.83 and 2.58% of Met as MP; CU CON = 2.22 and 2.19% of Met as percentage of MP, and CU RPM = 2.85 and 2.65% of Met as percentage of MP. Treatments were evaluated until 112 ± 3 d in milk (DIM). Milk yield was recorded daily. Milk samples were collected at wk 1 and 2 of lactation, and then every other week, and analyzed for milk composition. For lactation pens, dry matter intake (DMI) was recorded daily. Body weight and body condition score were determined from 4 ± 3 DIM and parturition until 39 ± 3 and 49 DIM, respectively. Plasma AA concentrations were evaluated within 3 h after feeding during the periparturient period [d ?7 (±4), 0, 7 (±1), 14 (±1), and 21 (±1); n = 225]. In addition, plasma AA concentrations were evaluated (every 3 h for 24 h) after feeding in cows at 76 ± 8 DIM (n = 16) and within 3 h after feeding in cows at 80 ± 3 DIM (n = 72). The RPM treatment had no effect on DMI (27.9 vs. 28.0 kg/d) or milk yield (48.7 vs. 49.2 kg/d) for RPM and CON, respectively. Cows fed the RPM treatment had increased milk protein concentration (3.07 vs. 2.95%) and yield (1.48 vs. 1.43 kg/d), and milk fat concentration (3.87 vs. 3.77%), although milk fat yield did not differ. Plasma Met concentrations tended to be greater for cows fed RPM at 7 d before parturition (25.9 vs. 22.9 µM), did not differ at parturition (22.0 vs. 20.4 µM), and were increased on d 7 (31.0 vs. 21.2 µM) and remained greater with consistent concentrations until d 21 postpartum (d 14: 30.5 vs. 19.0 µM; d 21: 31.0 vs. 17.8 µM). However, feeding RPM decreased Leu, Val, Asn, and Ser (d 7, 14, and 21) and Tyr (d 14). At a later stage in lactation, plasma Met was increased for RPM cows (34.4 vs. 16.7 µM) consistently throughout the day, with no changes in other AA. Substantial variation was detected for plasma Met concentration (range: RPM = 8.9–63.3 µM; CON = 7.8–28.8 µM) among cows [coefficient of variation (CV) > 28%] and within cow during the day (CV: 10.5–27.1%). In conclusion, feeding RPM increased plasma Met concentration and improved lactation performance via increased milk protein production.     

Effect of supplement crude protein concentration on milk production over the main grazing season and on nitrogen excretion in late-lactation grazing dairy cows

The objectives of this study are to evaluate the effects of (1) a potential interaction between supplement crude protein (CP) concentration and differing cow genotypes on milk production, (2) differing cow genotypes on milk production, and (3) decreasing the supplement CP concentration on milk production and N excretion during the main grazing season within a spring-calving herd. A 2 × 2 factorial arrangement experiment, with 2 feeding strategies [14%; n = 30 (lower CP; LCP) and 18%; n = 28 (higher CP; HCP) CP concentrate supplements] offered at varying levels according to pasture availability and days in milk (DIM) was conducted over the main grazing season from April 3 to September 3, 2019, at University College Dublin Lyons Farm. Cows were also grouped into 2 genotype groups: lower milk genotype; n = 30 [LM; milk kg predicted transmitting ability (PTA): 45 ± 68.6 (mean ± SD); fat kg PTA: 10 ± 4.9; and protein kg PTA: 7 ± 2.3] and higher milk genotype; n = 28 [HM; milk kg PTA: 203 ± 55.0; fat kg PTA: 13 ± 3.8; and protein kg PTA: 10 ± 2.4]. A total of 46 multiparous and 12 primiparous (total; 58) Holstein Friesian dairy cows were blocked on parity and balanced on DIM, body condition score, and Economic Breeding Index. Cows were offered a basal diet of grazed perennial ryegrass pasture. The N partitioning study took place from August 25 to 30, 2019 (187 ± 15.2 DIM). No interactions were observed for any milk production or milk composition parameter. No effect of supplement CP concentration was observed for any total accumulated milk production, daily milk production, or milk composition parameter measured. The HM cows had increased daily milk yield (+1.9 kg), fat and protein (+0.15 kg), and energy-corrected milk (+1.7 kg), compared with the LM cows. Furthermore, HM cows had decreased milk protein concentration (?0.1%) compared with LM cows. For the N partitioning study, cows offered LCP had increased pasture dry matter intake (PDMI; +0.9 kg/d), dietary N intake (+0.022 kg/d), feces N excretion (+0.016 kg/d), and decreased N partitioning to milk (?2%), and N utilization efficiency (?2.3%). In conclusion, offering cows LCP had no negative influence on milk production or milk composition over the main grazing season where high pasture quality was maintained. However, any potential negative effects of offering LCP on milk production may have been offset by the increased PDMI. Furthermore, offering cows LCP decreased N utilization efficiency due to the higher PDMI and feed N intake associated with cows on this treatment in our study.