Production Of Milk Components Research Articles

Lactogenic treatment effects on milk synthesis genes and protein secretion in cultured bovine mammary epithelial cells

In a cellular agriculture context, the possibility of producing milk components using tissue derived bovine mammary epithelial cells (MEC) is an upcoming strategy being considered. As an essential step, development of an in-vitro model for optimizing lactogenic activity of cultured MEC is needed. MECs were isolated from bovine mammary tissue and cultured in a trans-well system. Treatment with differentiation media (DM) was performed for 7-days. Conditioned media containing the cell secretions (the “secretomes”) were collected, and the trans-epithelial-resistance (TEER), measured. On day 7 the cells were lysed, and expression of lactation associated genes were examined using qPCR. Proteomic analysis of the secretomes was performed using timsToF Pro LC-MS/MS. DM treated cells had significantly higher TEER for several days but a general decreasing trend started on day 4. Expressions of CSN1S1, CSN2, CSN3, ELF5 and PRLR were significantly increased after DM treatment. DM significantly altered the secretome's protein compositions. Numerous proteins involved in lactogenic activity of the MEC were identified. However, the DM did not significantly impact their peak intensities. These findings shed light on areas requiring additional refinement of the in-vitro model to enhance the production of milk components. These aspects primarily comprise the DM composition and experimental length.

The Role of Progesterone in Elf5 Activation and Milk Component Synthesis for Cell-Cultured Milk Production in MAC-T Cells.

Prolactin is essential for mammary gland development and lactation. Progesterone also induces ductal branching and alveolar formation via initial secretory differentiation within the mammary gland. Herein, we aimed to evaluate the role of progesterone as a prolactin substitute for the production of cell-cultured milk components in MAC-T cells. Cells were treated with various hormones such as prolactin (PRL), progesterone (P4), 17β-estradiol (E2), cortisol (COR), and insulin (INS) for 5 d. MAC-T cells cultured in a P4 differentiation media (2500 ng/mL of P4, 25 ng/mL of E2, 25 ng/mL of COR, and 25 ng/mL of INS) showed similar levels of E74-like factor 5 (Elf5) and milk component synthesis (α-casein, β-casein, α-lactalbumin, β-lactoglobulin, and triglycerides) compared to those cultured in a PRL differentiation media (5000 ng/mL of PRL, 500 ng/mL of CORT, and 50 ng/mL of INS). The levels of α-casein and triglycerides in the optimal P4 differentiation media were present at comparable levels to those in the PRL differentiation media. Our results demonstrated that P4 induces the activation of Elf5 and the synthesis of milk components in MAC-T cells, similar to PRL. Therefore, P4 may be used as an effective substitute of PRL for cell-cultured milk production in in vitro frameworks.

Bovine mammary epithelial cells can grow and express milk protein synthesis genes at reduced fetal bovine serum concentration.

Milk proteins produced by lactating cells isolated from bovine mammary tissue can offer a sustainable solution to the high protein demand of a global growing population. Serum is commonly added to culture systems to provide compounds necessary for optimal growth and function of the cells. However, in a cellular agricultural context, its usage is desired to be decreased. This study aims at examining the minimum level of fetal bovine serum (FBS) required for the growth and functionality of bovine mammary epithelial cells (MECs). The cells were isolated from dairy cows in early and mid-lactation and cultured in reduced concentrations of FBS (10%, 5%, 1.25%, and 0%). Real-time cell analysis showed a significant effect of lactation stage on growth rate and 5% FBS resulted in similar growth rate as 10% while 0% resulted in the lowest. The effect of reducing FBS on cell functionality was examined by studying the expressions of selected marker genes involved in milk protein and fat synthesis, following differentiation. The gene expressions were not affected by the level of FBS. A reduction of FBS in the culture system of MEC, at least down to 5%, does not assert any negative effect on the growth and expression levels of studied genes. As the first attempt in developing an in-vitro model for milk component production using MEC, our results demonstrate the potential of MEC to endure FBS-reduced conditions.

Cellular characteristics and milk component productivity of primary bovine mammary cells for cell-cultured milk component production

Cellular characteristics and milk component productivity of primary bovine mammary cells for cell-cultured milk component production

69 The Bigger Picture of Phenomics: Whole-System Support for Systems Research, Models and Databases

Abstract Phenomics started with Mendel’s elegantly simple empirical studies. Soon after, Fisher discovered purines were rich in nuclei of all cells. A century later, we have the technology to compare the actual base pair sequence of DNA and RNA with the outward expressions of phenotypes. We have sire evaluation based on genomic and phenomic measure. But, being human, it is quite common to get immersed in exciting technology and tend to forget why we developed the technology in the first place. We only refer to ensuring a stable efficient food supply of plants and animals in the reports that we expect decision makers to read and give us more money. It is, however, truly wonderful that we now have the techniques to study the questions of the ages. But the future of phenomics is built on the foundations of the past. In 1974, A. E. Freeman and others convened a meeting under the mechanism of the newly formed Regional Research Project 2 on Defining the Inefficiency of Animal Production. From that workshop came the first modern multistate genetic study in dairy cattle with the objective to compare the phenotypes (milk component production, energy and nitrogen metabolism, hormones) of dairy animals that were born from bulls of High (+795 kg PTAM) and Low (167 kg PTAM) bulls. Please remember this study was designed in the mid 1970s and the first data collected in the early 1980s, decades before efficient methods of DNA and RNA composition were available. Studies conducted at Washington State University demonstrated marked genetic and environmental differences in adipose tissues of dairy animals. Enzymes involved with catabolic reactions were highly associated with High PTAM bulls while enzymes associated with anabolic reactions in adipose tissue were more closely related to increased energy intake regardless of genetic background. With mRNA chips, we were able, after almost 40 years, to directly relate variation in mRNA expression in the adipose tissue with the genetic background of the animals. This was the first such discovery in the field, and has led to more defined and expansive phenomics studies. In the year 2023, the use of genomics, phenomics, databases, large scale, cooperative studies and team science are specific recommendations, strategies and goals of the USDA, NIFA, The National Academies, and Land-Grant Universities. The AgBioData consortium is one example of international teams working together to expand the use of genetic and genomic databases, to prepare undergraduate and graduate level educational materials on FAIR databases and to encourage and support sustainable, robustly funded public and private partnerships in the use of integrated studies and large databases, including phenomics, with the sole purpose of expanding a robust, resilient, safe and plentiful food supply.

Association between white line disease and sole ulcers with certain milk components in Simmental cows

Lameness is one of the high influence production illnesses in intensive dairy production farming, it reduces milk yield and can also negatively affect the quality of milk. Many factors can affect the production of milk components. In addition race, nutrition, milk yield, various metabolic disorders, and lameness can have an effect on the synthesis of milk components. White line disease and sole ulcers are widespread hoof diseases of cows in tied-holding systems. Albeit the main cause of lameness, associations between claw disorders of cows and variation of milk components haven’t been widely studied in Simmental cows. The objective of our study was to investigate the effect of white line disease and sole ulcers on the production of milk components of Simmental dairy cows kept in the small households in Mačva locality, Serbia. Cows were selected with a history of lameness. A total of 3 groups of cows: affected by white line disease (n=12), sole ulcers (n=12), and healthy cows (n=12) in the early stage of lactation were selected for analysis of milk components. Milk components (milk protein, fat, and non-fat dry matter) were analyzed using Lactoscan S. Significance of differences in milk component characteristics between white line disease, sole ulcers, and healthy groups were tested using a Kruskal-Wallis multiple comparisons test. The contents of milk fat of cows affected by white line disease and cows affected by sole ulcers were significantly lower than those of non-lame cows: 3.80%, 3.69%, and 4.18%, respectively (both p<0.05). However, differences in the contents of milk protein and the contents of non-fat dry matter cows affected by white line disease, sole ulcers, and in health cows were not significantly different (p>0.05). Our results indicate that hoof diseases of cows namely whitee line disease and sole ulcers, significantly reduce the milk fat production in lame Simmental cows.

Using QTL to Identify Genes and Pathways Underlying the Regulation and Production of Milk Components in Cattle.

Milk is a complex liquid, and the concentrations of many of its components are under genetic control. Many genes and pathways are known to regulate milk composition, and the purpose of this review is to highlight how the discoveries of quantitative trait loci (QTL) for milk phenotypes can elucidate these pathways. The main body of this review focuses primarily on QTL discovered in cattle (Bos taurus) as a model species for the biology of lactation, and there are occasional references to sheep genetics. The following section describes a range of techniques that can be used to help identify the causative genes underlying QTL when the underlying mechanism involves the regulation of gene expression. As genotype and phenotype databases continue to grow and diversify, new QTL will continue to be discovered, and although proving the causality of underlying genes and variants remains difficult, these new data sets will further enhance our understanding of the biology of lactation.

Valine Treatment Enhances Antimicrobial Component Production in Mammary Epithelial Cells and the Milk of Lactating Goats Without Influencing the Tight Junction Barrier

The production of antimicrobial components and the formation of less-permeable tight junctions (TJs) are important in the defense system of lactating mammary glands and for safe dairy production. Valine is a branched-chain amino acid that is actively consumed in the mammary glands and promotes the production of major milk components like β-casein; additionally, branched-chain amino acids stimulate antimicrobial component production in the intestines. Therefore, we hypothesized that valine strengthens the mammary gland defense system without influencing milk production. We investigated the effects of valine in vitro using cultured mammary epithelial cells (MECs) and in vivo using the mammary glands of lactating Tokara goats. Valine treatment at 4 mM increased the secretion of S100A7 and lactoferrin as well as the intracellular concentration of β-defensin 1 and cathelicidin 7 in cultured MECs. In addition, an intravenous injection of valine increased S100A7 levels in the milk of Tokara goats without influencing milk yield and milk components (i.e., fat, protein, lactose, and solids). In contrast, valine treatment did not affect TJ barrier function either in vitro or in vivo. These findings indicate that valine enhances antimicrobial component production without influencing milk production and TJ barrier function in lactating mammary glands; thus, valine contributes to safe dairy production.

Differences in daily milk production during early pregnancy alter placental characteristics and neonatal metabolic amino acid levels in dairy cows.

We investigated the effects of differences in milk production during early pregnancy on placental characteristics at full term, calf birth weights, and their metabolic status. Thirty-four Holstein cows were categorized into three groups (Low, n = 9; Middle, n = 16; High, n = 9) based on the quartile of average daily 4% fat-corrected milk production during early pregnancy. The High group showed higher milk component production than the other groups (P < 0.05) during early and mid-pregnancy. Although most placental characteristics did not differ significantly among the groups, cows in the High group had larger individual cotyledons and fewer medium-sized cotyledons than those in the Low group (P < 0.05). Plasma amino acid concentrations of calves in the Low and High groups were significantly higher than those of calves in the Middle group, although calf birth weights were similar among the groups. Furthermore, cows in the Low group had longer dry periods than those in the High (P = 0.004) and Middle (P = 0.058) groups. This suggests that cows in the Low group may have provided more amino acids to the fetus because of low lactation and long dry periods. Conversely, cows in the High group required more energy for lactation during early pregnancy, which can reduce nutrient availability to the placenta and fetus; however, increasing individual cotyledonary sizes during late pregnancy may ensure that the same amounts of amino acids as those in cows in the Low group are supplied to the fetus, recovering the birth weights.

Deciphering the Key Regulatory Roles of KLF6 and Bta-miR-148a on Milk Fat Metabolism in Bovine Mammary Epithelial Cells.

MicroRNAs (miRNAs) are non-coding RNAs that regulate the expression of their target genes involved in many cellular functions at the post-transcriptional level. Previously, bta-miR-148a showed significantly high expression in bovine mammary epithelial cells (BMECs) of Chinese Holstein cows producing high milk fat compared to those with low milk fat content. Here, we investigated the role of bta-miR-148a through targeting Krüppel-like factor 6 (KLF6) and further analyzed the role of KLF6 in regulating fat metabolism through targeting PPARA, AMPK/mTOR/PPARG, and other fat marker genes in BMECs of Chinese Holstein. The bioinformatics analysis showed that the 3’ UTR of KLF6 mRNA possesses the binding sites for bta-miR-148a, which was further verified through dual-luciferase reporter assay. The BMECs were transfected with bta-miR-148a-mimic, inhibitor, and shNC, and the expression of KLF6 was found to be negatively regulated by bta-miR-148a. Moreover, the contents of triglyceride (TG), and cholesterol (CHO) in BMECs transfected with bta-miR-148a-mimic were significantly lower than the contents in BMECs transfected with bta-miR-148a-shNC. Meanwhile, the TG and CHO contents were significantly increased in BMECs transfected with bta-miR-148a-inhibitor than in BMECs transfected with bta-miR-148a-shNC. In addition, the TG and CHO contents were significantly decreased in BMECs upon the down-regulation of KLF6 through transfection with pb7sk-KLF6-siRNA1 compared to the control group. Contrarily, when KLF6 was overexpressed in BMECs through transfection with pBI-CMV3-KLF6, the TG and CHO contents were significantly increased compared to the control group. Whereas, the qPCR and Western blot evaluation of PPARA, AMPK/mTOR/PPARG, and other fat marker genes revealed that all of the genes were considerably down-regulated in the KLF6-KO-BMECs compared to the normal BMECs. Taking advantage of deploying new molecular markers and regulators for increasing the production of better-quality milk with tailored fat contents would be the hallmark in dairy sector. Hence, bta-miR-148a and KLF6 are potential candidates for increased milk synthesis and the production of valuable milk components in dairy cattle through marker-assisted selection in molecular breeding. Furthermore, this study hints at the extrapolation of a myriad of functions of other KLF family members in milk fat synthesis.

Genes and Pathways Affecting Sheep Productivity Traits: Genetic Parameters, Genome-Wide Association Mapping, and Pathway Enrichment Analysis

Ewe productivity is a composite and maternal trait that is considered the most important economic trait in sheep meat production. The objective of this study was the application of alternative genome-wide association study (GWAS) approaches followed by gene set enrichment analysis (GSEA) on the ewes’ genome to identify genes affecting pregnancy outcomes and lamb growth after parturition in Iranian Baluchi sheep. Three maternal composite traits at birth and weaning were considered. The traits were progeny birth weight, litter mean weight at birth, total litter weight at birth, progeny weaning weight, litter mean weight at weaning, and total litter weight at weaning. GWASs were performed on original phenotypes as well as on estimated breeding values. The significant SNPs associated with composite traits at birth were located within or near genes RDX, FDX1, ARHGAP20, ZC3H12C, THBS1, and EPG5. Identified genes and pathways have functions related to pregnancy, such as autophagy in the placenta, progesterone production by the placenta, placental formation, calcium ion transport, and maternal immune response. For composite traits at weaning, genes (NR2C1, VEZT, HSD17B4, RSU1, CUBN, VIM, PRLR, and FTH1) and pathways affecting feed intake and food conservation, development of mammary glands cytoskeleton structure, and production of milk components like fatty acids, proteins, and vitamin B-12, were identified. The results show that calcium ion transport during pregnancy and feeding lambs by milk after parturition can have the greatest impact on weight gain as compared to other effects of maternal origin.

An in vitro method for assessment of amino acid bidirectional transport and intracellular metabolic fluxes in mammary epithelial cells

Understanding uptake of AA by mammary tissue as supply varies is critical for predicting milk component production. Our objective was to develop an in vitro method to quantify cellular uptake, efflux, and intracellular metabolism of individual AA that could be implemented for evaluating these factors when AA supply and profile are varied. Bovine primary mammary epithelial cells were grown to confluency and exposed to medium with an AA profile and concentration similar to lactating dairy cow plasma for 24 h. Cells were then preloaded in medium enriched with 15N-labeled AA for 24 h followed by removal of the 15N-labeled medium and incubation with medium enriched with 13C-labeled AA for 0, 15, 60, 300, 900, 1,800, and 3,600 s. Extracellular free AA and intracellular free and protein-bound AA were analyzed for concentrations and isotopic enrichment by gas chromatography-mass spectrometry. A dynamic, 12-pool model was constructed representing extracellular and intracellular free and protein-bound pools of an AA, and their respective 15N and 13C isotopes. Markov chain Monte Carlo simulation (n = 5,000) was conducted to evaluate prediction errors by deriving standard errors and posterior distributions for rate constants, fluxes, and pools. Cellular Ala influx and efflux were higher than Leu, reflecting Ala role in driving system L transport and the high capacity of sodium-dependent transport. The Ala and Leu turnover rates were 181 and 95, 580 and 857, and 74 and 157% per hour for extracellular, intracellular, and fast protein-bound pools, respectively. The intracellular and extracellular Ala to Leu ratios were quite different, meaning the blood AA profile is not the AA profile provided for protein translation. The high level of exchange and rapid turnover of pools provide a mechanism for matching the AA supplies to the precision necessary for translation. This also understates the importance of using experimental medium similar to what is observed in vivo given that some AA depend on other AA for influx (exchange driven). The average root mean squared prediction error across the isotope enrichments, pools, and concentrations was 9.7 and 14.1% for Ala and Leu, respectively, and collinearity among parameters was low, indicating adequate fit and identifiability. The described model provides insight on individual AA transport kinetics and a method for future evaluation of AA transport and intracellular metabolism when subjected to varying AA supplies.

The effects of maternal supplementation of selenium and iodine via slow-release blouses in late pregnancy on milk production of goats and performance of their kids

Forty pregnant dairy goats were used in a 2 × 2 factorial arrangement of treatments to evaluate the effects of prepartum supplementation of selenium (Se) and iodine (I) as slow-release boluses. The boluses were administered four weeks prior to the expected kidding time to supply daily amounts of (1) 0 mg Se and 0 mg I, (2) 0 mg Se and 0.40 mg I, (3) 0.25 mg Se and 0 mg I and (4) 0.25 mg Se and 0.4 mg I. Milk production, milk fat percentage, daily production of milk components, milk selenium and iodine concentrations were greater in goats received 0.25 mg Se/day than no supplemental Se (p < .05). Milk production, daily production of milk compounds, milk iodine concentration, serum T3 and T4 concentrations in goats received 0.40 mg I/day were greater than goats received no supplemental I (p < .05). Bodyweight at weaning and average daily gain in kids whose mothers were received 0.25 mg Se/day were greater than zero Se (p < .05). Bodyweight at weaning and average daily gain in kids whose mothers were given 0.40 mg I/day were greater than zero I (p < .05). Serum Se and T3 concentration and whole blood glutathione peroxidase activity were significantly greater in goats and their kids received 0.25 mg Se/day than goats received no supplemental Se (p < .05). There was no Se level × I level interaction for all assessed parameters. Results showed that maternal supplementation of Se and I as a slow-release ruminal bolus in late pregnancy improved milk production of grazing goats and the performance of their kids. Highlights Intra-ruminal administration of slow-release boluses containing selenium and iodine improved milk production of grazing goats. Kids from goats receiving supplemental selenium and iodine via intra-ruminal boluses perform better. Intra-ruminal administration of slow-release boluses containing selenium in late pregnancy improved the antioxidant status of grazing goats and their kids.

Annual rhythms of milk synthesis in dairy herds in 4 regions of the United States and their relationships to environmental indicators

The annual rhythms of milk and milk component yields are not well described and are important to dairy management. Recent analysis of federal milk marketing orders in the United States observed that the amplitude and time at peak (acrophase) of the rhythms of milk fat and protein concentration differ among regions, but the rhythms of milk and milk component yields are not well described. Our objective was to determine the annual rhythms of milk and milk component production from 4 US regions at the herd level and examine potential environmental factors entraining these rhythms. Monthly Dairy Herd Improvement Association records of all available herds in Pennsylvania (PA), Minnesota (MN), Texas (TX), and Florida (FL) from the years 2003 to 2016 were obtained from Dairy Records Managements Systems. Milk yield, fat and protein yield, and fat and protein concentration were fit to the linear form of the cosine function with a 12-mo period using a linear mixed effects model. Additionally, the fit of models containing either the cosine function or environmental temperature were compared using an F-test. Milk yield and fat and protein yields and concentrations fit a cosine function in all 4 states, indicating an annual rhythm. The amplitude (peak to mean) of the rhythm of milk yield varied by state and was lower in PA (1.2 kg) and MN (1.2 kg) compared with TX (3.1 kg) and FL (3.3 kg). Fat and protein yields similarly showed greater amplitudes in the southern versus northern states. The amplitudes of the rhythms of fat and protein concentration were opposite by region, with greater amplitudes occurring in MN and PA than in TX and FL. The acrophases of milk yield and milk fat and protein yields and concentrations also varied by state, but all peaked between October and March. An annual rhythm fit the data better than changes in environmental temperature for all responses in all states, except for fat and protein concentrations in FL, which exhibited lower amplitude seasonal rhythms. The yearly pattern of milk yield closely followed the fixed yearly pattern of the day to day changes in day length, whereas the rhythms of milk fat and protein concentrations followed the yearly pattern of absolute day length. Results suggest that the region of the United States in which a herd is located affects their annual rhythms of production, with a greater yearly variation in milk, fat, and protein yields occurring in the southern United States. The consistency of annual rhythms across years and herds allowed development of regression equations to adjust expectations across the year to account for the annual rhythm.

Expression of genes related to energy metabolism and the unfolded protein response in dairy cow mammary cells is affected differently during dietary supplementation with energy from protein and fat

Secretory capacity of bovine mammary glands is enabled by a high number of secretory cells and their ability to use a range of metabolites to produce milk components. We isolated RNA from milk fat to measure expression of genes involved in energy-yielding pathways and the unfolded protein response in mammary glands of lactating cows given supplemental energy from protein (PT) and fat (FT) tested in a 2 × 2 factorial arrangement. We hypothesized that PT and FT would affect expression of genes in the branched-chain AA catabolic pathway and tricarboxylic acid (TCA) cycle based on the different energy types (aminogenic versus lipogenic) used to synthesize milk components. We also hypothesized that the response of genes related to endoplasmic reticulum (ER) homeostasis via the unfolded protein response would reflect the increase in milk production stimulated by PT and FT. Fifty-six multiparous Holstein-Friesian dairy cows were fed a basal total mixed ration (34% grass silage, 33% corn silage, 5% grass hay, and 28% concentrate on a dry matter basis) for a 28-d control period. Experimental rations were then fed for 28 d, consisting of (1) low protein, low fat (LP/LF); (2) high protein, low fat (HP/LF); (3) low protein, high fat (LP/HF); or (4) high protein and high fat (HP/HF). To obtain the high-protein (HP) and high-fat (HF) diets, intake of the basal ration was restricted and supplemented isoenergetically (net energy basis) with 2.0 kg/d rumen-protected protein (soybean + rapeseed, 50:50 mixture on dry matter basis) and 0.68 kg/d hydrogenated palm fatty acids on a dry matter basis. RNA from milk fat samples collected on d 27 of each period underwent real-time quantitative PCR. Energy from protein increased expression of BCAT1 (branched-chain amino acid transferase 1) mRNA, but only at the LF level, and tended to decrease expression of mRNA encoding the main subunit of the branched-chain keto-acid dehydrogenase complex. mRNA expression of malic enzyme, a proposed channeling route for AA though the TCA cycle, was decreased by PT, but only at the LF level. Expression of genes associated with de novo fatty acid synthesis was not affected by PT or FT. Energy from fat had no independent effect on genes related to ER homeostasis. At the LF level, PT activated XBP1 (X-box binding protein 1) mRNA. At the HF level, PT increased mRNA expression of the gene encoding GADD34 (growth arrest and DNA damage-inducible 34). These findings support our hypothesis that mammary cells use aminogenic and lipogenic precursors differently for milk component production when dietary intervention alters AA and fatty acid supply. They also suggest that mammary cells respond to increased AA supply through mechanisms of ER homeostasis, dependent on the presence of FT.

Short communication: Associations of feeding behavior and milk production in dairy cows

Identification of the associations of cow feeding behavior with productivity is important for supporting recommendations of strategies that optimize milk yield and composition. The objective of this study was to identify associations between measures of feeding behavior and milk production using data collated from studies of the feeding behavior of lactating dairy cows. A database containing behavior and production data for 132 dairy cow-week observations (mean of 7 d of consecutive data per cow) was assembled from 5 studies. Cows averaged (mean ± standard deviation) 1.8 ± 0.9 lactations, 108.4 ± 42.7 d in milk, and 654.6 ± 71.4 kg of body weight during each observation week. Production data included dry matter intake (27.0 ± 3.1 kg/d), milk yield (43.0 ± 7.0 kg/d), milk fat content (3.60 ± 0.49%), and milk protein content (3.05 ± 0.25%). Behavioral data included feeding time (230.4 ± 35.5 min/d), feeding rate (0.13 ± 0.03 kg/min), meal frequency (9.0 ± 2.0 meals/d), meal size (3.2 ± 0.9 kg/meal), daily mealtime (279.6 ± 51.7 min/d), and rumination time (516.0 ± 90.7 min/d). Data were analyzed in multivariable mixed-effect regression models to identify which behavioral variables, when accounting for other cow-level factors (days in milk, parity, and body weight) and dietary characteristics (forage level, nutrient content, and particle distribution), were associated with measures of production. Dry matter intake was associated with feeding time (+0.02 kg/min) and tended to be associated with rumination time (+0.003 kg/min) and meal frequency (+0.2 kg/meal). Similarly, milk yield was associated with feeding time (+0.03 kg/min) and rumination time (+0.02 kg/min), and tended to be associated with meal frequency (+0.3 kg/meal). Milk fat yield was associated with meal frequency (+0.02 kg/meal). Overall, our results suggest that milk yield and component production may be improved in situations where cows are able to increase their time spent feeding, in more frequent meals, and time spent ruminating.

Lactation response to soybean meal and rumen-protected methionine supplementation of corn silage-based diets

Corn silage, an important forage fed to dairy cows in the United States, is energy rich but protein poor. The objectives of this experiment were to investigate the effects on production of milk and milk components of feeding corn silage-based diets with 4 levels of dietary crude protein (CP) plus rumen-protected methionine (RPM). Thirty-six cows were blocked by days in milk into 9 squares and randomly assigned to 9 balanced 4 × 4 Latin squares with four 4-wk periods. All diets were formulated to contain, as a percent of dry matter (DM), 50% corn silage, 10% alfalfa silage, 4% soyhulls, 2.4% mineral-vitamin supplement, and 30% neutral detergent fiber. Supplemental RPM (Mepron, Evonik Corp., Kennesaw, GA) was added to all diets to maintain a Lys:Met ratio of 3.1 in digested AA. Ground high-moisture corn was reduced and soybean meal (SBM) plus RPM increased to give diets containing, on average, 11% CP (28% corn, 31% starch, 6% SBM, 4 g of RPM/d), 13% CP (23% corn, 29% starch, 10% SBM, 8 g of RPM/d), 15% CP (19% corn, 26% starch, 15% SBM, 10 g of RPM/d), and 17% CP (14% corn, 24% starch, 19% SBM, 12 g of RPM/d). Data from the last 14 d of each period were analyzed using the mixed procedures in SAS (SAS Institute Inc., Cary, NC). With the exception of milk fat and milk lactose content, we found no significant effects of diet on all production traits. We did note linear responses to dietary CP concentration for intake, production of milk and milk components, and MUN. Cows fed the 11% CP diet had reduced DM intake, lost weight, and yielded less milk and milk components. Mean separation indicated that only true protein yield was lower on 13% CP than on 17% dietary CP, but not different between 15 and 17% CP. This indicated no improvement in production of milk and milk components above 15% CP. Quadratic trends for yield of milk, energy-corrected milk, and true protein suggested that a dietary CP concentration greater than 15% may be necessary to maximize production or, alternately, that a plateau was reached and no further CP was required. Although diet influenced apparent digestibility of DM, organic matter, and neutral detergent fiber, digestibility did not increase linearly with dietary CP. However, we observed linear and quadratic effects of dietary CP on acid detergent fiber digestibility. As expected, we found a linear effect of dietary CP on apparent N digestibility and on fecal and urinary N excretion, but no effect of diet on estimated true N digestibility. Ruminal concentrations of ammonia, total AA, peptides, and branched-chain volatile fatty acids also increased linearly with dietary CP. Quadratic responses indicated that 14.0 to 14.8% CP was necessary to optimize digestion and energy utilization. Overall results indicated that, when RPM was added to increase Lys:Met to 3.1, 15% CP was adequate for lactating dairy cows fed corn silage diets supplemented with SBM and secreting about 40 kg of milk/d; N excretion was lower than at 17% CP but with no reduction in yield of milk and milk components.

Thinking outside the box: Innovative solutions for dairy goat management

For the geneticist or breeder, the individual animal is like a potential masterpiece resulting from years of attention to physical details and planned matings. The importance of culturing and nourishing this individual to not only reach its potential but to pass its selected genetics on to progeny is paramount. Thus, all the investment in genetic improvement is now at the mercy of management. Once the goats are in the herd on the farm and the responsibility of the farmer or farm manager, the expression and proliferation of the genotype will be strongly influenced by environmental factors. If maximum milk production per lactation were the real and only goal that could promise farm business and land sustainability, genetic selection would be easy. However, the real goal on farms is to have healthy goats that produce efficiently and are adapted to their environment. This places the development of the goat breeding program in the hands of farmers. To aid farmers in moving beyond the use of total milk production per goat as the feedback mechanism to farm sustainability, the integration of more appropriate progress indicators could include longevity (which, in humans, is estimated at 20% genetic and 80% environmental), the amount of milk or milk component production per body weight of goat, and the degree of involuntary culling.

Milk yield, milk composition, fatty acid profile and indices of milk fat quality as affected by feeding with extruded full-fat soybean

The aim of the study was to evaluate the effect of extruded full-fat soybean in diets of dairy cows on nutrient intake, milk yield, content and daily production of milk components, fatty acid (FA) profile and indices of milk fat quality. Four lactating Holstein cows were divided into control group fed a diet containing extruded rapeseed cake (R) and the experimental group fed a diet in which a part of extruded rapeseed cake was substituted by extruded full-fat soybean (RS). Dry matter intake (DMI), milk yield and milk composition were recorded. Milk FA profile was determined with subsequent calculation of atherogenicity index (AI), peroxidisability index (PI), desaturation indeks (DI) and spreadability index (SI) characterising quality of milk fat. Cows fed diet containing RS had higher DMI (17.8 kg/d) than cows fed diet containing R (16.8 kg/d, P&lt;0.05). Milk yield in RS (19.5 kg/d) was higher compared to R (17.6 kg/d, P&lt;0.05). Content of protein and casein was lower in RS than in R while content of lactose and urea was higher in RS than in R (P&lt;0.05). Experimental diet (RS) compared to control (R) had higher (P&lt;0.05) content of unsaturated FA (31.64 % and 30.69 %, respectively). Content of polyunsaturated FA in RS (4.03 %) was significantly higher (P&lt;0.05) than in R (3.66 %) mainly due to differences in C 18:2n6c, C 18:3n6 and C 18:3n3 FA (P&lt;0.05). Proportion of short-, medium- and long-chain FA was similar in both groups (P&gt;0.05). PI was higher (P&lt;0.05) in RS than in R being 5.54 and 5.06, respectively.

Analysis of pasture supplementation strategies by means of a mechanistic model of ruminal digestion and metabolism in the dairy cow

Effective pasture supplementation is critical to the efficiency of resource management in milk production. We understand a great deal about ruminal and metabolic processes in dairy cattle that control efficiency but we need to improve our ability to predict effects of practical feeding strategies based on the basic biological processes of the cow. Therefore, a large-scale pasture supplementation study was used to explore the details of both practical management and the underlying biological principles and processes involved. This included a multiple lactation study coupled with shorter-term experiments that tested the type and rate of supplementation. Basal supplementation strategies were (1) pasture allowance [14 kg of dry matter (DM)/d per cow] supplemented with milled barley grain fed twice daily in the milking parlor and pasture silage provided in the paddock; the ratio of grain:forage fed as supplement was 0.75:0.25 (control; DM basis); (2) the same pasture allowance plus the same amounts of milled barley grain and pasture silage, but the supplements were mixed and chopped before being fed immediately after each milking; and (3) the same pasture allowance and offered a partial mixed ration comprising barley (25%) and corn grain (30% of DM), corn silage (20% of DM), and alfalfa hay (25% of DM) after each milking. In late lactation (227 d in milk), a short-term experiment was done feeding the same pasture allowances but with the 3 supplements offered at 6, 8, 10, and 12 kg of DM/d for an 11-d measurement period following adaptation to the diet to each of the 3 long-term supplementation groups. Production responses were recorded and ruminal volatile fatty acids (VFA) and pH were measured in a subset of animals. Model descriptions of yields of milk and milk constituents as well as mean concentrations of ruminal fluid VFA and ruminal fluid pH were compared with measured values resulting when dairy cows were fed 12 different pasture-based diets with different levels and types of dietary supplement. Inputs into the model were measured dry matter intake and feed composition on the 12 combined treatments as well as initial body weight and composition. The model described milk and milk component production within 1 standard deviation of the treatment means (less than 5% of the mean as measured in the root mean square error). The simulated proportions of ruminal acetate, propionate, and butyrate were consistent with observed effects of supplemental treatments and rate of supplementation; however, the error analysis showed room for improvement. The model described, to a general extent, the changes in ruminal pH; however, this investigation showed that the equations that describe ruminal pH need to be improved or modified. These results show that the fundamental knowledge of ruminal and organ metabolism in this mechanistic model is sufficient to describe the qualitative responses to complicated dietary strategies, but our quantitative understanding of the parameters involved such as degradation and absorption kinetics and ruminal pH still demands more specific research.