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

A Nutritional Investigation of Major Feed Types and Feed Rations Used in Medium-Scale Dairy Production Systems in Sri Lanka

In this paper, the nutritional quality, digestibility, and chemical composition of major feed types as well as the use of those feeds in rations by medium-scale dairy farmers in the Kurunegala district of Sri Lanka were studied. Nine dairy farms were visited fortnightly over a five-month period to identify the feeds that were commonly used. All farms operated under a stall-feeding system in which a manually mixed ration (MMR) was fed 2–3 times daily. Four forages were identified: Guinea grass ecotype A (Panicum maximum), called Guinea grass; Hybrid Napier CO-3 (Pennisetum purpureum × Pennisetum americanum), called CO-3 grass; Gliricidia (Gliricidia sepium); and maize stover (Zea mays L.), along with three other supplementary feeds (maize silage, barley distillers’ by-products, and commercially formulated cattle feed). These feeds were subjected to proximate analysis and in vitro digestibility analysis. The metabolisable energy (ME) of the forages ranged from 7.5–10.0 MJ/kg dry matter (DM), with the ME of Guinea grass and CO-3 grass (7.5 and 8.0 MJ/kg DM, respectively) being lower than that of Gliricidia (10.0 MJ/kg DM). The neutral detergent fibre (NDF) concentration of both Guinea grass and CO-3 grass (both 72% DM) was much higher than that of Gliricidia (47% DM). Crude protein (CP) was higher in Gliricidia (17.5% DM) than in either Guinea grass or CO-3 grass (8.0 and 8.8% DM, respectively). The ME of the supplementary feeds varied between 11.0 and 12.8 MJ/kg DM, while CP varied between 15.0 and 24.0% DM. The daily ME intake of cows was consistently 10% lower than their calculated daily energy requirement; for dry cows, the mean intake was 90 MJ/cow/day supplied vs. 101 MJ required, while for cows in early lactation the mean intake was 126 MJ/cow/day supplied vs. 140 MJ required. The average CP intake of lactating cows (13.5% DM) was inadequate (requirements: 16 to 17.5% DM), while the average CP intake of dry cows (11.8% DM) was satisfactory (requirements: 11 to 12% DM). The current study shows that the majority of the feed types used in these medium-scale dairy farms provide insufficient ME or CP to meet the nutritional requirements of either lactating or dry cows irrespective of the quantity of feed provided.

The Influence of Rotational Length, along with Pre- and Post-Grazing Measures on Nutritional Composition of Pasture during Winter and Spring on New Zealand Dairy Farms

The quality of ryegrass−clover pasture was investigated between August (winter: start of calving) and November (spring: end of breeding) on pasture-based dairy farms (>85% of total feed from pasture) that had short (n = 2, Farms A and B; winter ~30 days, spring ~20−25 days) or long (n = 2, Farms C and D; winter ~35 days, spring ~25−30 days) grazing rotations to determine whether quality was affected by grazing rotation length (RT). Weekly assessments of pasture growth and herbage quality were made using a standardised electronic rising plate meter, and near-infrared spectroscopy, respectively. Data were subjected to repeated measure mixed model analysis, in which herbage quality was the outcome variable. The highest pre-grazing dry matter (PGDM) and height, post-grazing dry matter (DM) and height, and number of live leaves per tiller (leaf regrowth stage, LS) were present in late spring. Neutral detergent fibre (NDF), acid detergent fibre (ADF), metabolisable energy (ME), and organic matter digestibility (OMD) were positively correlated to each other (r2 ≥ 0.8) whilst ADF and lipid, and ADF and OMD were negatively correlated (r2 ≥ −0.8; p < 0.01). Metabolisable energy content was negatively correlated with ADF and NDF (r2 = −0.7, −0.8, respectively), and was inversely related to PGDM. Metabolisable energy was higher (p < 0.05) in farms with shorter (overall mean: 11.2 MJ/kg DM) than longer (10.9 MJ/kg DM) RT. Crude protein was also inversely related to PGDM and was higher with shorter (23.2% DM) than longer (18.3% DM; p < 0.05) RT. Pre-grazing DM affected the amount of pasture that was grazed and, hence, the amount of DM remaining after grazing (post-grazing DM or residual), so that PGDM was correlated with post-grazing height and residual DM (r2 = 0.88 and 0.51, respectively; both p < 0.001). In conclusion, RT, LS, and PGDM during winter and spring influenced the herbage quality, therefore, better management of pastures may enhance the productivity of dairy cows.

Formulating diets for intestinal unavailable nitrogen using blood meal in high-producing dairy cattle

The high cost of protein feeds and growing concern for the environment have motivated dairy producers and nutritionists to focus their attention on reducing nitrogen (N) losses on dairy farms. It is well recognized that reducing the N content of cattle diets is the single most important factor to increase the efficiency of N use. However, effectively lowering the N content of diets requires the nutritionist to know the availability of N in feeds so as to not negatively affect milk production or overfeed N. To provide reliable data for nutritionists, a new assay to estimate unavailable N in the intestine (uN) was developed. To determine whether uN could be used as a replacement for acid detergent insoluble nitrogen (ADIN) in diet formulation, we conducted a replicated pen study to evaluate the effect of total-tract uN on the performance of high-producing dairy cattle. One hundred twenty-eight cattle that were 97 to 147 d in milk at the beginning of the experiment were allocated into 8 pens of 16 cows, and pens were randomly allocated to 2 dietary treatments. Cattle were fed 1 of 2 isonitrogenous and isocaloric diets that were also equal in neutral detergent fiber, deviating only in the inclusion of 2 different blood meals (BM) used in each diet. The uN contents of the 2 BM were 9% (low uN) and 34% (high uN) total N content as predicted by the assay, whereas when measured as ADIN, no difference in indigestibility was observed. The inclusion of BM was on an isonitrogenous basis, and the predicted difference in uN was 39 g/d or 5.8% of N intake, representing the formulated difference in available N between the 2 treatments. There was no effect of uN on dry matter or N intake, which averaged 27.3 kg/d and 668 g/d for both treatments, respectively. Milk yield and energy-corrected milk were 1.6 and 1.9 kg/d greater for cows fed the low uN diet compared with those fed the high uN diet. The lower uN diet was also associated with greater milk protein yield, greater milk fat yield, and greater milk urea N. The Cornell Net Carbohydrate and Protein System (version 6.5) was used to evaluate the application of the uN measurement by replacing ADIN in BM with the uN value in the inputs for the BM. All other cow and feed chemistry data were inputted as measured in the experiment. The predictions of metabolizable protein-allowable milk demonstrated that using the uN values in place of ADIN increased the accuracy of the prediction and enabled the model to predict the first-limiting nutrient provided all other feed, cattle, and management characteristics were also defined.

Short-Term Adaptation of Dairy Cattle Production Parameters to Individualized Changes in Dietary Top Dress

Immediate and short-term changes in diet composition can support individualized, real-time interventions in precision dairy production systems, and might increase feed efficiency (FE) of dairy cattle in the short-term. The objective of this study was to determine immediate and short-term effects of changes in diet composition on production parameters of dairy cattle fed varying amounts of top dressed commodities. A 4 × 4 replicated Latin square design was used to evaluate responses of twenty-four Holstein cows fed either no top dress (Control) or increasing amounts of: corn grain (CG), soybean meal (SBM), or chopped mixed grass hay (GH) top dressed on a total mixed ration (TMR) over four, 9-day periods. Throughout each period, top dressed commodities were incrementally increased, providing 0% to 20% of calculated net energy of lactation (NEL) intake. Measured production responses were analyzed for each 9-d period using a mixed-effects model considering two different time ranges. Samples collected from d 3 and 4 and from d 7 and 8 of each period were averaged and used to reflect "immediate" vs. "short-term" responses, respectively. In the immediate response time frame, control fed cows had lower milk yield, milk fat yield, and milk true protein yield than CG and SBM supplemented animals but similar responses to GH supplemented animals. Milk fat and protein percentages were not affected by top dress type in the immediate term. In the short-term response time-frame, GH supplemented animals had lower DMI and milk fat yield than all other groups. Control and GH supplemented cows had lower milk yield than CG and SBM fed cows. In the immediate response time frame, FE of SBM supplemented cows was superior to other groups. In the short-term time frame, FE of GH and SBM groups was improved over the control group. Results suggest that lactating dairy cows show rapid performance responses to small (<20% NEL) changes in dietary composition, which may be leveraged within automated precision feeding systems to optimize efficiency of production. Before this potential can be realized, further research is needed to examine integration of such strategies into automatic feeding systems and downstream impacts on individual animal FE and farm profitability.

Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate-based diets

Worldwide milk production is predominantly founded on indoor, high-concentrate feeding systems, whereas pasture-based feeding systems are most common in New Zealand and Ireland but have received greater attention recently in countries utilizing conventional systems. Consumer interest in 'pasture-fed' dairy products has also increased, arising from environmental, ethical, and nutritional concerns. A substantial body of research exists describing the effect of different feeding strategies on the composition of milk, with several recent studies focusing on the comparison of pasture- and concentrate-based feeding regimes. Significant variation is typically observed in the gross composition of milk produced from different supplemental feeds, but various changes in the discrete composition of macromolecular components in milk have also been associated with dietary influence, particularly in relation to the fatty acid profile. Changes in milk composition have also been shown to have implications for milk and dairy product processability, functionality and sensory properties. Methods to determine the traceability of dairy products or verify marketing claims such as 'pasture-fed' have also been established, based on compositional variation due to diet. This review explores the effects of feed types on milk composition and quality, along with the ultimate effect of diet-induced changes on milk and dairy product functionality, with particular emphasis placed on pasture- and concentrate-based feeding systems.

Effect of increasing dietary protein with constant lysine:methionine ratio on production and omasal flow of nonammonia nitrogen in lactating dairy cows

Eight lactating cows were fed 4 diets in which dietary crude protein (CP) was increased in steps of approximately 2 percentage units from 11 to 17% of DM by replacing high-moisture corn with soybean meal supplemented with rumen-protected Met to maintain a Lys:Met ratio of 3:1 in metabolizable protein. Trial design was a replicated 4 × 4 Latin square; experimental periods lasted 28 d, with data and sample collection being performed during wk 3 and 4 of each period. Digesta samples were collected from the rumen as well as the omasum to measure metabolite concentrations and ruminal outflow of N fractions using infusion of ¹⁵N-enriched ammonia to quantify microbial nonammonia N (NAN) and nonmicrobial NAN. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc.). There were linear increases in the yields of milk and true protein and concentration of milk urea N, and a linear decrease in N efficiency, with increasing dietary CP. Apparent ruminal and total-tract N digestibility increased linearly with increasing dietary CP, but estimated true total-tract N digestibility was not affected. Apparent digestibility of the other macronutrients was not influenced by diet. Ruminal ammonia, total AA and peptides, and branched-chain VFA also increased linearly with dietary CP. The ¹⁵N enrichment of liquid- and particle-associated microbes linearly declined with increasing dietary CP due to decreasing ¹⁵N enrichment of the ammonia pool. Although no effect of dietary CP on nonmicrobial NAN flow was detected, total NAN flow increased linearly from 525 g/d at 11% CP to 637 g/d at 17% CP due to the linear increase in microbial NAN flow from 406 g/d at 11% CP to 482 g/d at 17% CP. Under the conditions of this study, when dietary CP was increased by adding soybean meal supplemented with rumen-protected Met, improved milk and protein yields were driven not by RUP supply but by increased ruminal outflow of microbial protein.

Growth performance, carcass characteristics, and meat quality of Mongolian lambs fed native grass or hay with or without concentrate on the Inner Mongolian Plateau

The aim of this study was to evaluate the effects of native grass on growth performance, carcass characteristics, and meat quality of Mongolian lambs fed Inner Mongolia native grass in three forms: grass, hay, and hay with concentrate (HC). Sixty Mongolian noncastrated male lambs, in good health and with the same age (6 mo) and similar body weights (mean, 28.63 ± 0.19 kg), were randomly divided into three treatments. There were four replicates in each treatment, with five lambs in one pen as a replicate. Compared with the HC group, the intake of the grass group was higher (P < 0.05) and that of the hay group was lower (P < 0.05). The hay group had a gain of −58.67 g d−1, compared with 42.33 g d−1 for the HC group and 80.00 g d−1 for the grass group. The carcass weight, net meat mass, loin muscle area, and fat thickness (a measure of fat tissue thickness) were greater in the grass and HC groups than in the hay group (P < 0.05). Compared with the hay group, the protein and calcium contents, marbling score, and water loss rate were greater in the grass and HC groups (P < 0.05), whereas the fat, phosphorus, cholesterol contents, and b* score were lower for the latter groups (P < 0.05). These results suggest that feeding of native grass hay with concentrate could improve the growth performance and meat quality of Mongolian lambs and achieve results similar to those observed in grass-fed lambs.

Improving nutritional accuracy and economics through a multiple ration-grouping strategy

The objective of this study was to develop a model application to systematize nutritional grouping (NG) management in commercial dairy farms. The model has 4 sub-sections: (1) real-time data stream integration, (2) calculation of nutritional parameters, (3) grouping algorithm, and (4) output reports. A simulation study on a commercial Wisconsin dairy farm was used to evaluate our NG model. On this dairy farm, lactating cows (n = 2,374 ± 185) are regrouped weekly in 14 pens according to their parity and lactation stage, for which 9 diets are provided. Diets are seldom reformulated and nutritional requirements are not factored to allocate cows to pens. The same 14 pens were used to simulate the implementation of NG using our model, closely following the current farm criteria but also including predicted nutritional requirements (net energy for lactation and metabolizable protein; NE_L and MP) and milk yield in an attempt to generate more homogeneous groups of cows for improved diet accuracy. The goal of the simulation study was to implement a continuous weekly system for cows' pen allocation and diet formulation. The predicted MP and NE_L requirements from the NG were used to formulate the diets using commercial diet formulation software and the same feed ingredients, feed prices, and other criteria as the current farm diets. Diet MP and NE_L densities were adjusted to the nutritional group requirements. Results from the simulation study indicated that the NG model facilitates the implementation of an NG strategy and improves diet accuracy. The theoretical diet cost and predicted nitrogen supply with NG decreased for low-nutritional-requirement groups and increased for high-nutritional-requirement groups compared with current farm groups. The overall average N supply in diets for NG management was 15.14 g/cow per day less than the current farm grouping management. The average diet cost was $3,250/cow per year for current farm management and $3,219/cow per year for NG, which resulted in a theoretical $31/cow per year diet cost savings.

Effects of partial replacement of soybean meal with other protein sources in diets of lactating cows

The protein nutrition of dairy cows is of great importance because of its direct influence on milk production, reproductive efficiency, and feeding cost. Eight first-lactation Holstein cows were randomly assigned to two contemporary 4 × 4 Latin squares in a 2 × 2 factorial design to evaluate the effects of replacing soybean meal with yeast-derived microbial protein (YMP) as a protein source (0% or 1.5% of dry matter (DM)) and its combination with slow-release urea (SRU; 0% or 0.75% of DM) on DM intake and milk production and composition, as well as blood parameters and nitrogen balance. Each experimental period lasted 28 days, with 21 days of adaptation and 7 days of data collection. The diets were formulated to attend the nutritional recommendations of the National Research Council and consisted of 49% forage (47% corn silage and 2% Tifton hay) and 51% concentrate, with 16.8% CP and 1.6 Mcal net energy for lactation/kg DM. For diets without YMP, the inclusion of SRU decreased DM intake, milk production as well as N intake and balance, but did not affect efficiency of production, milk composition or most of blood parameters. On the contrary, for diets with YMP, DM intake and milk production were increased by inclusion of SRU, while minor effects were observed for milk efficiency and composition, blood parameters as well as N intake, excretion and balance. When diets with SRU were compared, the inclusion of YMP increased DM intake, 4% fat-corrected milk, and N intake and balance (P<0.05), with no differences in milk production (kg/day), milk energy, efficiency of milk production or most of the blood parameters. For diets without SRU, YMP inclusion decreased DM intake, milk production, milk energy, N intake, fecal N and N balance (P<0.05), with no effects on milk efficiency and composition, or most of blood parameters. In conclusion, the use of YMP, SRU or both as partial substitutes of soybean meal in the diet of lactating cows has no negative effects on productivity parameters.

Assessing bioavailability of ruminally protected methionine and lysine prototypes

Met and Lys are essential AA that can limit lactational performance in dairy cattle fed protein-sufficient diets. Thus, there is industry demand for ruminally protected (RP) sources of Met and Lys. One method of providing ruminal protection for Met and Lys is lipid encapsulation. The objective of this work was to assess 3 lipid-encapsulated Met prototypes (P1, P2, and P3) and 1 Lys prototype (P4) to determine ruminal protection, small intestine absorption (experiment 1), and animal production responses (experiment 2). Ruminal protection was estimated from 8-h in situ retention during ruminal incubation and intestinal absorption from plasma appearance after an abomasal bolus of the in situ retentate. Blood samples were collected over time to determine plasma Met and Lys concentration responses compared with unprotected Lys and Met infused abomasally. The prototypes were not exposed to the total diet or subjected to typical feed handling methods before evaluation. The bioavailability of P1, P2, and P3 Met prototypes was found to be 14, 21, and 18% of the initial AA material, respectively. The RP-Lys prototype had a bioavailability of 45%. To evaluate production responses, 20 Holstein cows were randomly assigned to 2 trials (n = 10 each) in a replicated Latin square design with 14-d periods. The base diet was predicted to be deficient in metabolizable Met (-14.8 g/d) and Lys (-16.1 g/d) per the Cornell Net Carbohydrate and Protein System (version 6.55). In the Met trial, the base diet was supplemented with RP-Lys to meet Lys requirements, and treatments were as follows: no added RP-Met (NCM), NCM plus Smartamine M (SM; Adisseo, Alpharetta, GA), and NCM plus P1, P2, or P3 at 148% of the Met content of SM. In the Lys trial, the base diet was supplemented with RP-Met to meet the Met requirement, and treatments were as follows: no added Lys (NCL), NCL plus AjiProL (AL; Ajinomoto Heartland Inc., Chicago, IL), and NCL plus P4 at 55, 78, or 102% of the reported absorbed Lys in AL. All products were top dressed on the diet without prior mixing or extended exposure to the rest of the diet. Milk protein concentration significantly increased when diets were supplemented with P2, P3, or SM (3.12, 3.12, and 3.11%, respectively) compared with NCM (3.02%). Only P1 (3.04%) was significantly lower than SM. Prototype P2 had the greatest numerical milk protein output response among the 3 RP-Met prototypes, suggesting that it may have had the greatest efficacy when supplemented into these rations. There was a numerical milk protein concentration response to AL and a linear increase in milk protein concentration for P4. The P4 and AL treatments resulted in comparable milk protein production regardless of P4 dose.

Variation in animal performance explained by the rumen microbiome or by diet composition

The central aim of this meta-analysis was to determine whether the rumen microbiome can serve as an accurate predictor of performance in beef and dairy cattle compared with predictions based on diet composition. To support this comparison, a set of models was derived and compared. Models predicted milk yield (MY), average daily gain (ADG), dry matter intake (DMI), dairy feed efficiency (FE), and beef FE using different sets of independent variables: diet (D), microbial (M), and experimental (E). Diet variables included dry matter, organic matter, neutral detergent fiber, acid detergent fiber, crude protein, ether extract, nonfiber carbohydrate, starch, and forage percentages. Microbiome variables included relative abundance of 3 major rumen bacterial phyla, species richness, and species diversity. Experimental variables included publication year, breed type (dairy, beef, or Bos indicus), and rumen sampling fraction (fluid or solid). A second set of models used D and E variables as predictors for the microbiome. For both the production and microbiome model sets, predictor variable sets were used individually and in combination. Linear mixed-effects regression, weighted by 1/standard error of the mean, was used to derive models using data from 51 peer-reviewed publications. Models for the same response variable were compared on the basis of concordance correlation coefficient with study effects removed (uCCC), root-estimated variance associated with study and error, and corrected Akaike information criterion values, wherever appropriate. The MY model using D + M + E predictors outperformed all other MY models (uCCC = 0.71). ADG was most accurately predicted by D alone (uCCC = 0.92). Interestingly, M + E was more successful at predicting DMI than any model using D variables. Similarly, dairy FE was more accurately predicted by M + E than D, albeit only slightly (uCCC = 0.69 vs. 0.65). Beef FE could only be modeled using D variables. Overall, breed type proved a better predictor of relative abundances of most rumen bacterial phyla than D. Conversely, species richness and diversity indicators were unaffected by breed type, but could be predicted by D with moderate precision and accuracy (uCCC = 0.63 to 0.69). This analysis suggests that diet and the microbiome may exert independent effects on various aspects of performance. Further research is necessary to determine the reasons for these independent influences.

Review: Optimizing ruminant conversion of feed protein to human food protein

Ruminant livestock have the ability to produce high-quality human food from feedstuffs of little or no value for humans. Balanced essential amino acid composition of meat and milk from ruminants makes those protein sources valuable adjuncts to human diets. It is anticipated that there will be increasing demand for ruminant proteins in the future. Increasing productivity per animal dilutes out the nutritional and environmental costs of maintenance and rearing dairy animals up to production. A number of nutritional strategies improve production per animal such as ration balancing in smallholder operations and small grain supplements to ruminants fed high-forage diets. Greenhouse gas emission intensity is reduced by increased productivity per animal; recent research has developed at least one effective inhibitor of methane production in the rumen. There is widespread over-feeding of protein to dairy cattle; milk and component yields can be maintained, and sometimes even increased, at lower protein intake. Group feeding dairy cows according to production and feeding diets higher in rumen-undegraded protein can improve milk and protein yield. Supplementing rumen-protected essential amino acids will also improve N efficiency in some cases. Better N utilization reduces urinary N, which is the most environmentally unstable form of excretory N. Employing nutritional models to more accurately meet animal requirements improves nutrient efficiency. Although smallholder enterprises, which are concentrated in tropical and semi-tropical regions of developing countries, are subject to different economic pressures, nutritional biology is similar at all production levels. Rather than milk volume, nutritional strategies should maximize milk component yield, which is proportional to market value as well as food value when milk nutrients are consumed directly by farmers and their families. Moving away from Holsteins toward smaller breeds such as Jerseys, Holstein-Jersey crosses or locally adapted breeds (e.g. Vechur) would also reduce lactose production and improve metabolic, environmental and economic efficiencies. Forages containing condensed tannins or polyphenol oxidase enzymes have reduced rumen protein degradation; ruminants capture this protein more efficiently for meat and milk. Although these forages generally have lower yields and persistence, genetic modification would allow insertion of these traits into more widely cultivated forages. Ruminants will retain their niches because of their ability to produce valuable human food from low value feedstuffs. Employing these emerging strategies will allow improved productive efficiency of ruminants in both developing and developed countries.

Whole-tract digestibility and nitrogen-use efficiency of partial mixed rations with and without canola meal

Increasing the crude protein (CP) concentration of a ration fed to grazing dairy cows by adding canola meal can increase milk production. The present study investigated the effect of extra CP intake on nitrogen-use efficiency and the fate of the additional dietary nitrogen (N). Sixteen spring-calved rumen fistulated cows were housed in metabolism stalls for a 9-day period and offered one of the following four treatment diets: (1) 8 kg DM/cow.day of fresh perennial ryegrass (PRG) supplemented with 12 kg DM/cow.day of a partial mixed ration (PMR) comprising oaten hay, crushed maize and wheat grain (PMR 8); (2) 12 kg DM/cow.day of fresh-cut PRG and 12 kg DM/cow.day of PMR (PMR 12); (3) the same as for PMR 8 cows, except some wheat in the PMR was replaced with canola meal (PMR+C 8); and (4) the same as the PMR 12 cows, except some wheat in the PMR was replaced with canola meal (PMR+C 12). The PMR and the PMR+C diets were iso-energetic, but the canola meal provided extra CP. Crude protein intake was 14.4%, 14.8%, 16.8% and 17.4% DM for PMR 8, PMR 12, PMR+C 8 and PMR+C 12 respectively. The addition of canola meal increased DM intake (P < 0.05) from 20.4 to 21.6 kg/day and increased N intake (P < 0.001) from 478 to 590 g/day. Nitrogen digestibility increased (P < 0.05) from 67% to 71%, nitrogen-use efficiency decreased (P < 0.05) from 37% to 32% and urinary-N output increased (P < 0.01) from 118 to 160 g/day, indicating that the additional CP fed resulted in additional N surplus. Energy-corrected milk yield for the experimental period was 34 ± 3.1 kg/cow.day (mean ± s.d.); however, due to the low number of cows, the ability to rigorously assess the effects on milk production was limited.

The effect of feeding maize silage 1 h or 9 h before the herbage meal on dry matter intake, milk production, nitrogen partitioning and rumen function of lactating dairy cows

The study was conducted to evaluate the effect of the timing of feeding maize silage before a short herbage meal on dry matter (DM) intake, milk production, nitrogen (N) partitioning and rumen function of lactating dairy cows. Ten lactating, pregnant, Friesian × Jersey rumen-fistulated dairy cows aged 4–5 years were blocked in pairs by milksolids (MS; sum of protein and fat) production (1.73 ± 0.097 kg MS/cow.day; mean ± s.d.), bodyweight (519 ± 24.7 kg), days in milk (163 ± 12.5), and body condition score (3.9 ± 0.21). Cows within pairs were randomly allocated to one of two treatments: (1) five cows were offered one-third of their estimated total DM intake (5 kg/cow.day) as maize silage after the afternoon milking at 1500 hours, ~1 h before herbage was provided (1BH); (2) five cows were offered one-third of their estimated total DM intake as maize silage after morning milking at 0700 hours, ~9 h before herbage was provided (9BH). All cows were offered two-thirds of their total estimated DM intake (11 kg/cow.day) over a period of 4 h from 1600 hours to 2000 hours as freshly cut perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens) in an indoor system. Cows were adapted to diets for 9 days (Days 1–9), followed by 5 days of measurement (Days 10–14). Maize silage DM intake did not differ between treatments averaging 5.1 kg DM/cow.day. Herbage DM intake was greater (P = 0.02) for 9BH (11.2 kg DM/cow.day) than 1BH (10.4 kg DM/cow.day). Milk yield (P = 0.001) and MS production (P = 0.08) were greater for 9BH than 1BH (18.8 vs 15.4 kg/cow.day and 1.63 vs 1.48 kg MS/cow.day, respectively). There was no effect of time of supplementation on N partitioned to milk, faeces, or urine. The purine derivatives to creatinine ratio, as an indication of microbial protein production, was greater (P = 0.04) for 9BH than 1BH. Daily mean rumen pH and the concentration of total rumen volatile fatty acids, acetate, butyrate, and ammonia N were not affected by treatment. However, the peak concentration of ruminal ammonia N was 27% lower (P < 0.05) for 9BH than 1BH. The concentration of non-esterified fatty acid (P = 0.03) and beta-hydroxy butyric acid (P = 0.01) were greater for 1BH than 9BH (0.14 vs 0.09 and 0.81 vs 0.71 mmol/L, respectively). These results indicate that under herbage feed restriction, altering the time of supplementation relative to the herbage meal can increase herbage DM intake and subsequent milk production.

Short communication: Substituting dry distillers grains with solubles and rumen-protected amino acids for soybean meal in late-lactation cows' diets based on corn silage or ryegrass silage

Excess protein in dairy cattle diets increases production costs and contributes to environmental pollution. The objective of the present study was to evaluate the effect of feeding dry distillers grains with solubles (DDGS) supplemented with rumen-protected Lys and Met in place of solvent-extracted soybean meal on the performance of late-lactation cows. Two experiments were carried out, with each using 24 late-lactating dairy cows distributed among 4 pens. In trial 1, corn silage was the main forage source. Control (HP1) total mixed ration (TMR) contained 16.3% crude protein (CP) with soybean meal as the main protein source. Treatment TMR (LP1) had 13.7% CP when soybean meal was replaced with DDGS and rumen-protected Lys and Met. Forage in trial 2 was ryegrass silage; control TMR (HP2; 15.4% CP) contained soybean meal and rumen-protected Met, whereas treatment TMR (LP2; 13.8% CP) contained DDGS and rumen-protected Lys and Met. Trials were analyzed as crossover design using the MIXED procedure of SAS (SAS Institute Inc., Cary NC) with cow as sampling unit and pen as the experimental unit. Treatments were similar in dry matter intake (21.0 and 20.4 kg/cow per day for HP1 and LP1, respectively) and milk yield (20.7 and 20.5 kg/cow per day for HP1 and LP1, respectively) during trial 1. Milk composition was similar between treatments, averaging 4.22, 3.73, 4.54, and 9.15, respectively, for fat, protein, lactose, and solids nonfat. Milk urea nitrogen decreased from 17.2 mg/dL for HP1 to 9.93 mg/dL for LP1. In trial 2, no significant differences were observed for dry matter intake (21.4 and 20.9 kg/cow per day for HP2 and LP2, respectively), milk yield (28.1 and 26.6 kg/d for HP2 and LP2, respectively), fat yield (0.99 vs. 0.92 kg/d for HP2 and LP2, respectively), protein yield (0.94 vs. 0.86 kg/d for HP2 and LP2, respectively) and lactose yield (1.37 vs. 1.28 for HP2 and LP2, respectively). Milk urea nitrogen decreased from 9.88 mg/dL with HP2 to 6.39 mg/dL with the LP2 treatment. Milk N efficiency tended to be higher for LP treatments in trial 1, but not in trial 2. Low milk urea N suggested nitrogen losses to the environment may be lower when cows were fed diets based on DDGS in both trials. The studies indicated that DDGS with rumen-protected Lys and Met could substitute solvent-extracted soybean meal in low-protein corn silage- and ryegrass silage-based diets for late-lactation dairy cows averaging 20.6 or 27.4 kg of milk/d, respectively.

Replacing dietary soybean meal with canola meal improves production and efficiency of lactating dairy cows

Previous research suggested that crude protein (CP) from canola meal (CM) was used more efficiently than CP from solvent soybean meal (SBM) by lactating dairy cows. We tested whether dietary CP content influenced relative effectiveness of equal supplemental CP from either CM or SBM. Fifty lactating Holstein cows were blocked by parity and days in milk into 10 squares (2 squares with ruminal cannulas) in a replicated 5×5 Latin square trial. Five squares were fed: (1) low (14.5-14.8%) CP with SBM, (2) low CP with CM, (3) low CP with SBM plus CM, (4) high (16.4-16.7%) CP with SBM, and (5) high CP with CM; the other 5 squares were fed the same diets except with rumen-protected Met plus Lys (RPML) added as Mepron (Degussa Corp., Kennesaw, GA) and AminoShure-L (Balchem Corp., New Hampton, NY), which were assumed to provide 8g/d of absorbed dl-Met and 12g/d of absorbed l-Lys. Diets contained [dry matter (DM) basis] 40% corn silage, 26% alfalfa silage, 14 to 23% corn grain, 2.4% mineral-vitamin premixes, and 29 to 33% neutral detergent fiber. Periods were 3wk (total 15wk), and data from the last week of each period were analyzed using the Mixed procedures of SAS (SAS Institute Inc., Cary, NC). The only effects of RPML were increased DM intake and milk urea N (MUN) and urinary N excretion and trends for decreased milk lactose and solids-not-fat concentrations and milk-N:N intake; no significant RPML × protein source interactions were detected. Higher dietary CP increased milk fat yield and tended to increase milk yield but also elevated MUN, urine volume, urinary N excretion, ruminal concentrations of ammonia and branched-chain volatile fatty acids (VFA), lowered milk lactose concentration and milk-N:N intake, and had no effect on milk true protein yield. Feeding CM instead of SBM increased feed intake, yields of milk, energy-corrected milk, and true protein, and milk-N:N intake, tended to increase fat and lactose yields, and reduced MUN, urine volume, and urinary N excretion. At low CP, MUN was lower and intake tended to be greater on SBM plus CM versus SBM alone, but MUN and N excretion were not reduced to the same degree as on CM alone. Interactions of parity × protein source and parity × CP concentration indicated that primiparous cows were more responsive than multiparous cows to improved supply of metabolizable protein. Replacing SBM with CM reduced ruminal ammonia and branched-chain VFA concentrations, indicating lower ruminal degradation of CM protein. Replacing SBM with CM improved milk and protein yield and N-utilization in lactating cows fed both low- and high-CP diets.

Gas emissions from dairy cows fed typical diets of Midwest, South, and West regions of the United States

Gas emissions were determined for dairy cows fed three diets formulated to represent feed ingredients typical of the Midwest, South, or West regions of the United States. Dairy cows were housed and monitored in 12 environmentally controlled rooms (4 cows diet). Two experiments were performed, representing two lactation stages (initial days in milk were 115 ± 39 d in Stage 1 and 216 ± 48 d in Stage 2). The results demonstrated that the combination of different dietary ingredients resulted in different gas emissions while maintaining similar dry matter intake (DMI) and milk yield (MY). Diet effect on ammonia (NH) emissions was more prominent in Stage 1. During Stage 1, cows fed the Midwest diet had the highest daily NH emission, corresponding to the highest crude protein (CP) concentration among the three regions. The differences in NH emissions (39.0%) were much larger than the percent difference in CP concentrations between diets (6.8%). Differences in N intake, N excretion, or milk urea N alone may not serve as a strong indicator of the potential to reduce NH emissions. Lower emissions of methane (CH) per unit DMI or per unit MY were observed for cows offered the South diet during Stage 1 as compared with that from cows offered the Midwest or West diets. No diet effect was observed for hydrogen sulfide (HS) emission per unit S intake, nor for nitrous oxide (NO) emission. The measured NH and CH emissions were comparable, but the NO emissions were much higher than those reported for tie-stall dairy barns in the literature.

Effects of dietary supplementation of methionine and lysine on milk production and nitrogen utilization in dairy cows

The effect of the content of lysine and methionine in metabolizable protein (MP) on lactation performance and N utilization in Chinese Holstein cows was determined. A control diet (C) was formulated to be adequate in energy but slightly limiting in MP. The concentration of Met and Lys in MP was 1.87 and 5.93%, respectively. The treatments were as follows (% of Met or Lys in MP): L=diet C supplemented with L-lysine-HCl at 0.49% on a dry matter (DM) basis (Met, 1.87; Lys, 7.00); M=diet C supplemented with 2-hydroxy-4-(methylthio)-butanoic acid (HMB) at 0.15% (Met, 2.35; Lys, 5.93); ML=diet C supplemented with 0.49% L-lysine HCl and 0.15% HMB (Met, 2.39; Lys, 7.10). The diets were fed to 60 Chinese Holsteins in mid-lactation (average days in milk=120, and milk yield=32.0 kg/d) for 8 wk. Milk yield was increased by supplementation of either Lys (1.5 kg/d) or Met (2.0 kg/d), and supplementation of both Lys and Met further increased milk yield (3.8 kg/d). There was no significant difference in dry matter intake across treatment groups. Cows on treatments M (3.95%) and ML (3.90%) had higher milk fat content than those on C (3.60%) and L (3.67%), but there were no significant differences in milk protein and lactose contents or somatic cell count among treatments. Supplementation of Met or Lys significantly increased Met or Lys concentration in arterial plasma. Treatment ML had a higher conversion of intake N to milk N and lower urea N concentrations in serum, urine, and milk than did treatment C. Supplementing HMB and L-lysine-HCl to provide approximately 2.3% Met and 7.0% Lys of the MP in diets slightly limiting in MP increased milk production, milk protein yield, and N utilization efficiency.

Effects of partial substitution of concentrates with maize silage in organic dairy cow rations on performance and feed efficiency

BACKGROUND

The general goal of organic dairy farming is to minimize purchased concentrate use and focus on milk production from forages. The aim of the present paper is to examine the influence of a partial substitution of purchased concentrates with home-grown maize silage on feed intake, milk production and feed efficiency in rations for organic dairy cows. In the experimental treatment group (E), two-thirds of average herd concentrate intake was replaced with 2.7 kg maize silage on a dry matter (DM) basis.

RESULTS

In treatment E, total DM, energy and protein intake were significantly reduced compared to the control treatment group (C). Daily milk yield decreased in E by 11% and milk urea content was significantly lower. Calculated milk production from forage was significantly higher (91 versus 71%) in treatment E. Efficiency of dietary nitrogen (N) utilization (calculated as milk N as a percentage of N intake) was slightly improved in E and protein and energy balance (calculated as intake as a percentage of requirements) were closer to zero than in C.

CONCLUSION

The present study indicates a potential to reduce levels of concentrates and substitute them with maize silage in organic dairy cow rations at least in the second half of lactation. Copyright © 2007 Society of Chemical Industry.

Effect of Dietary Level of Rumen-Degraded Protein on Production and Nitrogen Metabolism in Lactating Dairy Cows

Twenty-eight (8 with ruminal cannulas) lactating Holstein cows were assigned to 4 x 4 Latin squares and fed diets with different levels of rumen-degraded protein (RDP) to study the effect of RDP on production and N metabolism. Diets contained [dry matter (DM) basis] 37% corn silage, 13% alfalfa silage, and 50% concentrate. The concentrate contained solvent and lignosulfonate-treated soybean meal and urea, and was adjusted to provide RDP at: 13.2, 12.3, 11.7, and 10.6% of DM in diets A to D, respectively. Intake of DM and yield of milk, fat-corrected milk, and fat were not affected by treatments. Dietary RDP had positive linear effects on milk true protein content and microbial non-ammonia N (NAN) flow at the omasal canal, and a quadratic effect on true protein yield, with maximal protein production at 12.3% RDP. However, dietary RDP had a positive linear effect on total N excretion, with urinary N accounting for most of the increase, and a negative linear effect on environmental N efficiency (kg of milk produced per kg of N excreted). Therefore, a compromise between profitability and environmental quality was achieved at a dietary RDP level of 11.7% of DM. Observed microbial NAN flow and RDP supply were higher and RUP flow was lower than those predicted by the NRC (2001) model. The NRC (2001) model overpredicted production responses to RUP compared with the results in this study. Replacing default NRC degradation rates for protein supplements with rates measured in vivo resulted in similar observed and predicted values, suggesting that in situ degradation rates used by the NRC are slower than apparent rates in this study.

Milk Production and Nitrogen Excretion of Dairy Cows Fed Different Amounts of Protein and Varying Proportions of Alfalfa and Corn Silage

Four trials were conducted to determine the effect of dietary protein amount on lactation performance and N utilization. Each trial used one of the following alfalfa-to-corn-silage ratios for the forage part of the diet: 100:0, 75:25, 50:50, and 25:75. All trials utilized 16 mid-lactation Holstein cows (days in milk averages ranging from 80 to 140 among trials) in a replicated 4 x 4 Latin square design with 3-wk periods, including 2 wk for adaptation and 1 wk for data collection. Diets consisted of 50% forage and 50% concentrate (dry matter basis) and were formulated to contain 15.00, 16.25, 17.50, or 18.75% protein in each trial. The analyzed protein content of the diets was 15.7, 16.9, 18.0, and 19.2% when averaged across trials. Milk yield was similar among dietary protein levels in each trial, ranging from 35.2 to 36.1 kg/d when data were combined across trials. Changes in milk fat and protein due to the protein content of the diet were small and inconsistent. Both milk urea nitrogen and blood urea nitrogen concentrations increased linearly as the protein content of the diet was increased, ranging from 9.9 to 13.1 and from 9.9 to 13.8 mg/dL, respectively, across trials. As dietary protein was increased from the lowest to the highest concentrations when data were combined and analyzed, mean fecal N concentration increased from 2.8 to 3.0%, and urinary N from 5.8 to 7.3 g/L. At the same time, mean total N excretion increased from 484 to 571 g/d, and conversion of intake N to milk N decreased from 0.27 to 0.22, resulting in an average change of 18%. Of the N excreted, urinary N accounted for an increasing proportion, ranging from 41 to 48%, as dietary protein was increased. Overall, based on N utilization as well as milk production, 17% protein in diets utilizing various proportions of alfalfa and corn silage as the forage source appeared sufficient for cows producing 38 kg/d of milk in this study.

Varying protein and starch in the diet of dairy cows. II. Effects on performance and nitrogen utilization for milk production

The main objective of this experiment was to examine the effects of the percentage and source of crude protein (CP) and the amount of starch in the diet of dairy cows on the lactational performance and use of N for milk production. Sixty multiparous Holstein cows were used in a 210-d lactational trial with a completely randomized design with a 2 x 3 factorial arrangement of treatments. Two sources of CP [solvent-extracted soybean meal (SBM) and a mixture of SBM and a blend of animal-marine protein supplements plus ruminally protected Met (AMB)] and 3 levels of dietary CP (means = 14.8, 16.8, and 18.7%) were combined into 6 treatments. On a dry matter (DM) basis, diets contained 25.0% corn silage, 20.0% alfalfa silage, 10.0% cottonseed, 26.7 to 37.0% corn grain, and 4.8 to 13.5% protein supplement, plus minerals and vitamins. Across the 210 d of lactation, the productive response of dairy cows to the source of supplemental CP depended on the concentration of CP in the diet. At 18.7% CP, cows fed SBM consumed more DM and produced more milk, 3.5% fat-corrected milk, fat, and true protein, but had lower efficiency of feed use and body condition score than cows fed AMB. At 16.8% CP, cows fed AMB produced more 3.5% fat-corrected milk, fat, and true protein than cows fed SBM. At 14.8% CP, cows fed SBM consumed more DM but produced less true protein and had lower feed efficiency than cows fed AMB. Across CP sources, cows fed 14.8% CP produced less fat-corrected milk and true protein than cows fed 16.8 and 18.7% CP. Across CP percentages, cows fed AMB produced more fat-corrected milk per kilogram of DM consumed than cows fed SBM. Despite these interactions, improvements in the gross efficiency of N use for milk production were achieved through reductions in the intake of N independently of the source of CP. Data suggest that the intake of N by high-producing dairy cows that consume sufficient energy and other nutrients to meet their requirements can be decreased to about 600 to 650 g daily if the source of RDP and RUP are properly matched with the source and amount of carbohydrate in the diet.

Impacts of the source and amount of crude protein on the intestinal supply of nitrogen fractions and performance of dairy cows

The objective of this article was to review and summarize the significance of the amount and source of dietary crude protein supplements on the supply of nitrogen fractions passing to the small intestine and the performance of lactating dairy cows. A meta-analysis was used to evaluate 2 data sets, one for nitrogen flow to the small intestine and one for performance of cows. The response of dairy cows to rumen-undegradable protein supplements is variable. A portion of this variable response from research trials is explained by the source of crude protein in the control diet, the proportion and source of rumen-undegradable protein in the experimental diet, the effect of rumen-undegradable protein on microbial protein outflow from the rumen, the degradability and amino acid content of the rumen-undegradable protein, and the crude protein percentage of the diet. Compared with soybean meal, the mean milk production responses to feeding rumen-undegradable protein supplements ranged from -2.5 to +2.75%. Because of the large variation and small magnitude of response when rumen-undegradable protein supplements are fed compared with soybean meal, efficiency of nitrogen utilization and the cost to benefit ratio for these crude protein supplements may determine the source and amount of crude protein to feed to dairy cows in the future.

Effect of Two Levels of Crude Protein and Methionine Supplementation on Performance of Dairy Cows

Sixteen Holstein cows in midlactation were randomly assigned to treatments in a replicated 4 x 4 Latin square. Two levels of CP (16.1 vs. 18.8%) with or without supplemental methionine (0.07 g/100 g of DM) were tested in a 2 x 2 factorial arrangement of treatments. Dry matter intake, milk production, milk composition, and N excretion were determined. No interactions between CP level and methionine supplementation were observed. Milk production and dry matter intake were not different among treatments. Milk protein concentration increased from 3.17 to 3.26% with the addition of methionine and decreased from 3.24 to 3.17% with increased CP. No differences were observed among treatments in milk protein yield. Milk fat concentration was low across all diets, but was increased from 2.33% with 16.1% CP diets to 2.68% with 18.8% CP diets. No significant treatment effects were observed for SNF, lactose concentration in milk, or casein N as a fraction of skim milk N. Increased dietary CP increased milk urea N by 3.9 mg/dl. Methionine supplementation did not affect N excretion in urine or feces. The higher protein diets increased estimated urine volume by 2.9 L/d and increased N concentration by 1.7 percentage units in both urine and feces. Feeding higher protein increased milk urea and urine N excretion as expressed as a percentage of total N excreted (44 vs. 38% for 18.8 and 16.1% CP, respectively). Overall, feeding 16.1% CP produced milk and milk protein yields similar to feeding 18.8% CP, but reduced the N losses in urine and milk urea.

Nitrogen supplementation of corn silages. 1. Effects on feed intake and milk production of dairy cows

Feed intake and milk production responses to N supplementation of corn silage-based diets were measured in three 3 x 3 Latin square experiments. In each experiment, 9 Holstein cows received total mixed rations (TMR), based on corn silage. In Exp. 1, midlactation cows were used to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; MJ), providing a large deficiency (RL), a slight deficiency (RM), and a slight excess (RH) in relation to the target level of 11 g of ERDP/MJ of FME, respectively, for lactating cows. Diets were formulated to be isoenergetic, and to satisfy the metabolizable protein requirements. In Exp. 2, early-lactation cows were used to evaluate effects of different proportions of quickly and slowly rumen-degradable protein (RDP), achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in the rumen. Midlactation cows received a diet containing, on a dry matter (DM) basis, 45% corn silage, 5% ryegrass hay, 35% energy-rich concentrate, and 15% protein-rich concentrate (crude protein: 38% of DM; urea: 2% of DM). The protein-rich concentrate was fed either once (D1) or twice (D2) per day before the meal, or included in the TMR (DU). Treatment RL led to lower DM intake and milk yield, but higher milk production efficiency; there were no significant differences between treatments RM and RH. There were no significant treatment effects on DM intake, milk yield, or milk composition in Exp. 2. Manipulating rumen synchrony by altering the timing of feeding affected milk yields, with D1 cows producing significantly less than D2 and DU cows, which were similar. The amount of ERDP in the diet should be matched to the amount of fermentable energy available to maximize intake, milk yields, and the conversion of feed N into milk protein. However, this study showed only small benefits to altering the diurnal pattern of supply of RDP and FME, and only with extreme feeding strategies that would not be used in practice. Urine volume increased in response to increased or unbalanced protein supply. Analysis of the allantoin:creatinine ratio in spot samples of urine was not useful in identifying predicted differences in microbial protein yield from the rumen.

Lactation response and nitrogen, calcium, and phosphorus utilization of dairy goats differing by the genotype for alpha S1-casein in milk, and fed diets varying in crude protein concentration

Twenty-four dairy goats were used in a preliminary trial to evaluate the effect of the genotype for alpha S1-casein (alpha S1-CN) in milk [homozygous variant A/A (n = 12) or F/F (n = 12)] on milk yield and composition for 2 wk from kidding. After this period, the main trial aimed at determining the effects of the genotype for alpha S1-CN in milk, the dietary crude protein concentration on milk yield and composition, and utilization of N, Ca and P. The goats within each genotype were allocated to a 3 x 3 Latin square for 14 wk with three crude protein concentrations in the total mixed ration (13.2, 16.8, and 19.8% of dry matter) and three periods (wk 3 to 6, wk 8 to 11, and wk 13 to 16 postpartum) as factors. Balances of N, Ca, and P were determined in the last week of each period. Two wk after kidding, the alpha S1-CN A/A goats had higher percentage and yield of protein and lower body weight than the alpha S1-CN F/F goats. During the main trial, yields of protein and fat, as well as percentages of fat and protein in milk were higher for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats, independent of dietary CP concentration and period. Efficiency of N digestion for milk N was higher for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats. Urinary N as a percentage of digested N, and total N excretion expressed relative to milk N were lower for the alpha S1-CN A/A goats than for the alpha S1-CN F/F goats. Neither the apparent absorption of calcium or phosphorus was affected by the genotype for alpha S1-CN. Goats fed the low crude protein diet had lower milk yield and lower yields of fat and protein than those fed the other diets. Increasing dietary crude protein concentration increased urinary N, milk N, and N excretion relative to milk N; it also decreased the efficiency of digested N for milk N. In conclusion, selection of goats with a genetically higher yield of casein and fed with diets formulated to reduce N excretion improves the cheese-making properties of goat milk and reduces concerns about N wastes in the environment.

Effects of inclusion of a blended protein product in 35 dairy herds in five regions of the country

We assessed the change in milk production in 35 dairy herds located in eight states when a blended animal-marine protein product was included in diets at 2 (22 herds) to 4% (13 herds) of dry matter. Average 305-d production across herds was 8844.1 kg (SEM = 153.7 kg) of milk, with a range of 6876.9 to 11,293.2 kg. The mean days in milk for all herds at initiation of the trial was 118.8 d (SEM = 3.7, herd mean range of 68.8 to 160.0 d), and the average daily milk production was 32.6 kg (SEM = 0.6 kg, range 24.2 to 39.6 kg). The animal-marine protein blend was included in herd rations for 30 d, beginning immediately after a DHI herd test month and ending immediately after the next DHI sample test. Cow milk records were collected for 1 to 2 mo before the protein blend was included and for 2 to 3 mo after the protein was removed. Sample days were assigned a dummy variable to indicate months off or on the animal-marine protein blend. A total of 33,190 milk records from 7135 cows were analyzed. The numbers within herd ranged from 35 to 2012 cows. Of the 35 herds, 19 were classed as having increased milk yield, 12 herds as having no change, and 4 herds as having decreased milk yield when the animal-marine protein blend was included in the diet. The population mean for change in milk yield with the inclusion of the animal-marine protein blend was 1.24 kg/d of milk (SEM = 0.05 kg). There was no significant effect of parity on mean response. Milk protein content was not influenced by animal-marine protein blend inclusion. Fat content was lower for the month on which the animal-marine protein blend was fed (3.51%) compared with the month prior (3.63%) and the month after (3.70%), respectively (SEM = 0.032). Stage of lactation influenced the method for calculating the production response and the actual response to the animal-marine protein blend.