Milk Quality In Dairy Cows Research Articles

Beta-Sitosterol Promotes Milk Protein and Fat Syntheses-Related Genes in Bovine Mammary Epithelial Cells.

Simple SummaryThe levels of milk fats and proteins are important indexes used to evaluate milk quality. Generally, feed additives are used to improve milk quality. This study aimed to investigate the effect of β-sitosterol on milk fat and protein gene expression in bovine mammary epithelial cells. β-sitosterol increased the β-casein levels in bovine mammary epithelial cells and promoted the expression of milk fat and protein synthesis-related genes, suggesting the use of β-sitosterol as a potential feed additive to improve milk quality in dairy cows.β-sitosterol, a phytosterol with multiple biological activities, has been used in the pharmaceutical industry. However, there are only a few reports on the use of β-sitosterol in improving milk synthesis in dairy cows. This study aimed to investigate the effects of β-sitosterol on milk fat and protein syntheses in bovine mammary epithelial cells (MAC-T) and its regulatory mechanism. MAC-T cells were treated with different concentrations (0.01, 0.1, 1, 5, 10, 20, 30, or 40 μM) of β-sitosterol, and the expression levels of milk protein and fat synthesis-related genes and proteins were analyzed. β-sitosterol at 0.1, 1, and 10 μM concentrations promoted the mRNA and protein expression of β-casein. β-sitosterol (0.1, 1, 10 μM) increased the mRNA and protein expression levels of signal transducer activator of transcription 5 (STAT5), mammalian target of rapamycin (mTOR), and ribosomal protein S6 kinase beta-1 (S6K1) of the JAK2/STAT5 and mTOR signaling pathways. It also stimulated the milk fat synthesis-related factors, including sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARγ), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), and stearyl CoA desaturase (SCD). β-sitosterol (0.1, 1, 10 μM) also significantly increased the expression of growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and hypoxia-inducible factor-1α (HIF-1α)-related genes. Notably, the compound inhibited the expression of the negative regulator, the suppressor of cytokine signaling 2 (SOCS2) at the two lower concentrations (0.1, 1 μM), but significantly promoted the expression at the highest concentration (30 μM). These results highlight the role of β-sitosterol at concentrations ranging from 0.1 to 10 μM in improving milk protein and fat syntheses, regulating milk quality. Therefore, β-sitosterol can be used as a potential feed additive to improve milk quality in dairy cows.

Milk microbiome: evaluation study on the differences among cows with a different health status classified by leukocyte pattern

Milk microbiome: evaluation study on the differences among cows with a different health status classified by leukocyte pattern

Factors affecting raw milk quality of dairy cows under practical conditions

Under the practical conditions, it is important to evaluate the factors affecting milk performance. Data from test day yield and milk components should be useful for such evaluation. The aim of the experiment was to study the effect of season, udder health (by somatic cell counts SCC), parity, stage of lactation on milk production, milk components, and SCC under the practical conditions. Also, the frequency of incidence of high SCC during the season was observed. The experiment was realized on one dairy farm in dairy practice. The experiment lasted from December 2015 to October 2017. We examined 481 Holstein dairy cows (6910 milk samples). Milk samples were collected once per month – performed by recording test day. Only cows with 9 – 11 test days were evaluated. The effect of season, parity, stage of lactation, and SCC influenced most of the studied traits. The milk yield was highest at 2nd lactation. In the following lactations, the milk yields were decreasing. The SCC significantly increased with advanced parity. The elevated SCC was found in the beginning and in the final part of lactation. SCC as a factor significantly reduced milk yield, lactose content but increased fat and protein content. In conclusion, under practical conditions, the management should use the data from test days and analyze them for a better understanding of the performance efficiency at the farm level and for implementing more sophisticated decision making in farming.

Effect of Sulfur and Urea Fortification of Fresh Cassava Root in Fermented Total Mixed Ration on the Improvement Milk Quality of Tropical Lactating Cows.

The aim of the present research was to determine the influence of sulfur and urea combined with fresh cassava root in fermented total mixed ration (FTMR) on digestibility, fermentation in the rumen, blood metabolite, milk yield, and milk quality in tropical lactating dairy cows. Four mid-lactation Thai Holstein–Friesian crossbred cows were studied. Pre-experiment milk yield was 12.7 ± 0.30 kg/day, and the body weight was 495 ± 40.0 kg. Animals were evaluated in a 2 × 2 factorial in a 4 × 4 Latin square design to receive diets followed by: factor A, which was a dose of sulfur inclusion at 1.0% and 2.0%, and factor B, which was level of urea inclusion at 1.25% and 2.5% DM in FTMR. The hydrogen cyanide (HCN) concentrations reduced 99.3% to 99.4% compared with fresh cassava root when FTMR was supplemented with 1.0% and 2.0% sulfur, respectively. Intake of crude protein was increased based on urea level addition (p < 0.05). Blood thiocyanate concentration was increased by 21.6% when sulfur was supplemented at 2.0% compared to 1.0% (p < 0.05). There was no difference in protozoal concentration, whereas bacterial populations at 4 h after feeding were significantly greater by 6.1% with the FTMR supplemented with 2.0% sulfur and 2.5% urea (p < 0.01). Allantoin concentrations, excretion, absorption, and microbial crude protein showed significant interactions between sulfur levels and urea levels in cows fed diets supplemented with 2.0% sulfur and 2.5% urea (p < 0.05). The molar ratios of the volatile fatty acid (VFA) profile were affected by dietary FTMR (p < 0.01). Furthermore, propionic acid increased by 4.6% when diets were supplemented by 2.5% sulfur (p < 0.01). Milk fat and total solids increased when feed was supplemented with 2.0% sulfur and 2.5% urea (p < 0.05). The diets supplemented with 2.0% sulfur levels resulted in greater concentrations of milk thiocyanate (p < 0.05). The somatic cell count was significantly reduced throughout the experiment with increasing sulfur supplementation (p < 0.05). Animals fed diets supplemented with 2.0% sulfur exhibited a decreased somatic cell count by 18.3% compared with those fed diets supplemented with 1.0% sulfur. Thus, inclusion of 2.0% sulfur with 2.5% urea in FTMR containing fresh cassava root improved digestibility, ruminal fermentation, microbial crude protein synthesis, and milk qualities in dairy cows.

Differential Somatic Cell Count as a Novel Indicator of Milk Quality in Dairy Cows.

Simple SummaryRecently, high-throughput instruments have been used to analyze milk differential somatic cell count, represented by the combined proportion of polymorphonuclear leukocytes and lymphocytes, providing indirect information on the udder inflammation status of dairy cows. No information is available about the relationship between differential somatic cell count and milk quality, so the aim of this study was to investigate the effect of differential somatic cell count on the composition of a large number of individual milk samples. Results showed that milk quality worsened when differential somatic cell count was high. In particular, it was evidenced lower milk fat, protein, casein contents and casein index, and augmented milk fatty acids could be found with an increasing differential somatic cell count level. These findings confirmed that differential somatic cell count could be a new informative tool for dairy farmers to monitor the quality of milk.Recent available instruments allow to record the number of differential somatic cell count (DSCC), representing the combined proportion of polymorphonuclear leukocytes and lymphocytes, on a large number of milk samples. Milk DSCC provides indirect information on the udder health status of dairy cows. However, literature is limited regarding the effect of DSCC on milk composition at the individual cow level, as well as its relation to the somatic cell score (SCS). Hence, the aims of this study were to (i) investigate the effect of different levels of DSCC on milk composition (fat, protein, casein, casein index, and lactose) and (ii) explore the combined effect of DSCC and SCS on these traits. Statistical models included the fixed effects of days in milk, parity, SCS, DSCC and the interaction between SCS × DSCC, and the random effects of herd, animal within parity, and repeated measurements within cow. Results evidenced a decrease of milk fat and an increase in milk fatty acids at increasing DSCC levels, while protein, casein and their proportion showed their lowest values at the highest DSCC. A positive association was found between DSCC and lactose. The interaction between SCS and DSCC was important for lactose and casein index, as they varied differently upon high and low SCS and according to DSCC levels.

The effect of a commercial probiotic product on the milk quality of dairy cows

Probiotics intended to improve plant health and productivity of pastures grazed by dairy cow are becoming commercially available in Australia. Great Land (GL; Terragen Biotech Pty Ltd., Coolum Beach, QLD, Australia) is one such biologic soil conditioner and spray-on probiotic with a label claim of "acting to improve plant health and productivity." The objective of this study was to quantify the effect of GL on the milk quality of cows grazing pasture top-dressed with GL. Lactating dairy cows of mixed age and breed (primarily Holstein-Friesian), in their second lactation or greater, and at least 80 d in milk were enrolled and randomly allocated into 1 of 2 study groups: a treatment cow group (n = 98; cows grazed pasture that was top-dressed with GL according to the product label) and a control cow group (n = 114; cows grazed untreated pasture). As required, both groups were supplemented at the same rate with a mixed ration during the grazing period. Composite milk samples were collected weekly from each cow during the study and analyzed to determine milk components. Milk volumes were recorded at each milking using the herd management software of the study farm. Mean differences in the milk component variables were compared using mixed-effects linear regression models. After controlling for the effect of days in milk, cow lactation, and time since a cow entered the study, the treatment cows produced an average of 1.21 L/cow per day more milk (95% confidence interval: 0.34-2.08 L/cow per day) and more milk protein (0.03 kg/d; 95% confidence interval: 0.01-0.05 kg/d) than the control cows. Pasture cover and pasture consumption did not differ between the GL-treated and the untreated study paddocks grazed by the treatment or control cows. A limited amount of published data have examined the effect of probiotic pasture treatment on the milk quality of dairy cows. This study suggests that application of such products may be beneficial. The mechanisms associated with this type of outcome remain to be investigated.

Effect of substituting barley with glycerol as energy feed on feed intake, milk production and milk quality in dairy cows in mid or late lactation

The experiment reported in this research paper aimed to determine the level at which glycerol can substitute barley in grass-clover silage-based ration for dairy cows in mid or late lactation, without affecting milk production, milk composition, milk free fatty acid (FFA) profile, and milk sensory quality. Forty Holstein cows were used in a 4 × 4 Latin square experimental design. Crude glycerol substituted barley in the partially mixed ration (PMR) of the cows at inclusion levels of 0% (Gly0), 6% (Gly6), 12% (Gly12), and 18% (Gly18) of dietary dry matter (DM). Individual milk production, feed intake, and milking frequency were recorded daily, while milk composition and milk FA daily were analyzed weekly. Milk sensory analysis was performed on fresh and 7 d stored samples for the four diets. The PMR intake increased almost 1kg from Gly0 to Gly12, and decreased by approximately 1kg from Gly12 to Gly18. Concentrate intake at the automated milking unit tended to decrease by half a kg from Gly0 to Gly6. Milk yield decreased linearly with increasing proportions of glycerol in the diet while fat and protein contents in milk increased. This resulted in a quadratic effect of dietary glycerol level on ECM yield, with maximum yield with Gly6 and the lowest yield with Gly18. Protein and lactose yields decreased linearly with increasing proportions of glycerol in the diet. With increasing glycerol proportion in the diet, palmitic acid, oleic acid, linoleic acid, linolenic acid, and conjugated linoleic acid proportions in milk decreased linearly, while most of the short and medium chain FFA proportions in milk increased. To conclude, glycerol, as an energy feed, can substitute barley up to 18% of dietary DM for dairy cows in mid or late lactation without affecting milk quality. However, including more than 12% dietary glycerol might decrease ECM yield.

Effect of substituting soybean meal and canola cake with dried distillers grains with solubles at 2 dietary crude protein levels on feed intake, milk production, and milk quality in dairy cows

Dried distillers grain with solubles (DDGS) is an alternative source of feed protein for dairy cows. Previous studies found that DDGS, based on grains other than corn, can substitute for soybean meal and canola cake as a dietary protein source without reducing milk production or quality. As societal concerns exist, and in many areas strict regulation, regarding nitrogen excretion from dairy cows, the dairy industry has focused on reducing dietary protein level and nitrogen excretion. In the present study, we investigated the use of DDGS as a protein source, at a marginally low dietary crude protein (CP) levels, in a grass-clover and corn silage-based ration. The experiment involved 24 Holstein cows and 2 protein sources (DDGS or soybean-canola mixture) fed at 2 levels of CP (14 or 16%) in a 4 × 4 Latin square design. The aim of this study was to evaluate the effect of both protein source and protein level on feed intake, milk yield, and milk quality. The results indicated that feed intake, milk yield, and protein in milk increased when the protein level in the ration was 16% CP compared with 14%. We found no effect of substituting the soybean-canola mixture with DDGS. Moreover, no sensory problems were observed when comparing fresh milk with stored milk, and milk taste was unaffected by DDGS. Milk from cows fed DDGS had a slightly higher content of linoleic acid and conjugated linoleic acid (CLA 9-11), and lower content of C11 to C17 fatty acids than cows fed diets with the soybean-canola mixture. Cows fed the diets with 16% CP produced milk with higher oleic acids and lower palmitic acid content than cows fed 14% CP diets. To conclude, DDGS can substitute for a soybean-canola mixture without affecting feed intake, milk yield and quality, or sensory quality. Under the conditions of this experiment, feeding 16% CP compared with 14% CP in the ration can increase feed intake and milk production.

Effect of substituting soybean meal and canola cake with grain-based dried distillers grains with solubles as a protein source on feed intake, milk production, and milk quality in dairy cows

The growth of the bioethanol industry is leading to an increase in the production of coproducts such as dried distillers grains with solubles (DDGS). Both corn-based DDGS and grain-based DDGS (gDDGS; defined as originating from grain sources such as barley, wheat, triticale, or a mix, excluding corn) appear to be relevant sources of feed and protein for dairy cows. To date, most of the studies investigating DDGS have been performed with corn-based DDGS. The objectives of this study were to determine the effects of the proportion of gDDGS in the diet on feed intake, milk production, and milk quality. The present experiment involved 48 Holstein cows in a replicated 3 × 3 Latin square design with 3 grass-based dietary treatments consisting of 4, 13.5, and 23% gDDGS on a dry matter (DM) basis (L, M, and H, respectively) as a replacement for a concentrate mix. The concentrate mix consisted of soybean meal, canola cake, and beet pulp. Dry matter intake and energy-corrected milk yield were not affected by the proportion of gDDGS in the diet. Daily milk yield decreased with the H diet compared with the L and M diets. The percentage of fat in milk was higher when cows were fed the H diet compared with the L and M diets, whereas milk fat yield was not affected by dietary treatment. The M diet had a higher percentage of protein in milk compared with the L and H diets. Milk protein yield was similar for the L and M diets; however, it decreased for the H diet. Milk taste was not affected by the proportion of gDDGS in the diet or when milk was stored for 7 d. Linoleic acid and conjugated linoleic acid cis-9,trans-11 in milk increased with increasing proportion of gDDGS. To conclude, gDDGS can replace soybean meal and canola cake as a protein source in the diet of dairy cows. Up to 13.5% of the diet may consist of gDDGS without negatively affecting milk production, milk quality, or milk taste. When gDDGS represents 23% of dietary DM, milk production is reduced by 1.6 kg/d, whereas energy-corrected milk production is numerically reduced by 1 kg.

Effect of peroral supplementation with selenium and vitamin e during late pregnancy on udder health and milk quality in dairy cows

The aim of the experiment was to study selenium and vitamin E sources in the diet of dairy cows in late phase of pregnancy and their effects on udder health and milk quality during the first two weeks after calving. The experiment included 48 cows of Holstein breed divided into four equal groups (n = 12). The first experimental group (D1) was fed with addition of vitamin E in total dose of 1020 dl-a-tocopherol acetate Se/cow per day. The second group (D2) was added the selenium at a dose of 0.3 mg.kg-1 of DM in form of sodium selenite. The third group (D3) was supplemented with addition of vitamin E in combination with sodium selenite in total dose of 1020 dl-a-tocopherol acetate Se/cow per day and of 5.0 mg Se/cow per day, respectively. The control group (C) was without the addition of selenium and vitamin E. In group (D2) with addition of selenium at a dose of 0.3 mg.kg-1 of DM and vitamin E a dose of 50 mg dl-a-tocopherol acetate/kg of DM in diet, increased the plasmatic concentration of selenium and vitamin E and reduced the incidence of mastitis by 13.3% and number of somatic cells during peripartal period in comparison with other groups.

Effects of continuous low dose infusion of lipopolysaccharide on inflammatory responses, milk production and milk quality in dairy cows.

The objective of this study was to evaluate the effects of continuous low dose infusion of lipopolysaccharide (LPS) on inflammatory responses and milk production and quality in lactating dairy cows. Eight Holstein cows were assigned to two treatments in a cross-over experimental design. Cows were infused intravenously either with saline solution or with saline solution containing LPS from Escherichia coli O111:B4 at a dose of 0.01μg LPS/kg body weight for approximately 6hr each day during a seven-day trial. The clinical symptoms and milk production performance were observed. Milk samples were analysed for conventional components, fatty acids and amino acids. And jugular vein and mammary vein plasma samples were analysed for concentrations of cytokines and acute phase proteins. LPS infusion decreased feed intake and milk yield. An increase in body temperature was observed after LPS infusion. LPS infusion also increased plasma concentrations of interleukin-1β, serum amyloid A, LPS-binding protein, C-reactive protein and haptoglobin. LPS infusion decreased the contents of some fatty acids, such as C17:1, C18:0, C18:1n9 (trans) and C18:2n6 (trans), and most amino acids except for methionine, threonine, histidine, cysteine, tyrosine and proline in the milk. The results indicated that a continued low dose infusion of LPS can induce an inflammatory response, decrease milk production and reduce milk quality.

The Use of "Omics" in Lactation Research in Dairy Cows.

“Omics” is the application of genomics, transcriptomics, proteomics, and metabolomics in biological research. Over the years, tremendous amounts of biological information has been gathered regarding the changes in gene, mRNA and protein expressions as well as metabolites in different physiological conditions and regulations, which has greatly advanced our understanding of the regulation of many physiological and pathophysiological processes. The aim of this review is to comprehensively describe the advances in our knowledge regarding lactation mainly in dairy cows that were obtained from the “omics” studies. The “omics” technologies have continuously been preferred as the technical tools in lactation research aiming to develop new nutritional, genetic, and management strategies to improve milk production and milk quality in dairy cows.

Influence of selenium and vitamin e supplementation during pregnancy on udder health and milk quality in dairy cows at parturition

Selenium and vitamin E ranks among very important antioxidant agents protecting the organism from the effect of reactive oxygen forms. The deficiency of both nutrients during pregnancy in cows often result in metabolic disorders and increased of cases of related diseases (mastitis, retained placenta and other reproductive disorders). The aim of the present work was to study the influence of different dose of parenteral administration selenium and vitamin E in dairy cows prior to parturition on selected metabolic parameters, udder health and milk quality. A total in herd of 270 Holstein cattle in east of Slovakia in a two-four lactation-gestation cycle the control group (C) and 2 experimental groups (D, D1) were selected. All groups were similarly housed, managed and fed with the diet containing from 36 to 42 mg vitamin E and 0.2 mg.kg-1 Se of DM through the study period. In group D a products containing vitamin E and selenium were administered IM four weeks prior to the expected date of parturition in total dose of 1000 mg of dl-α-tocopherol acetate and of 44 mg sodium selenite per cow, respectively. In group D1 the same products were administered twice, four and two weeks prior to parturition. Blood samples were 4 weeks prior to predicted calving date (the time of treatment), on parturition day and at 14th day after calving for assessment of plasma vitamin E and selenium concentrations. Blood samples of the calves were drawn from jugular vein at birth and first colostrum was also collected. The occurrence of the mastitis and retained placenta during the first 14th day after calving were evaluated in all groups. Higher plasmatic and colostral concentrations of selenium and vitamin E were found only in group with repeat application of Se and vitamin E (D1) collected on the day of parturition. At the 14th day of postpartal period a trend of lower occurrence of mastitis was observed in group D1 compared to D group, administered IM once and control group. Parenteral supplementation of selenium and vitamin E during pregnancy had no impact on their transmission into the milk and on the presence of bacterial agents in raw milk obtained from dairy cows diagnosed with mastitis.

Effects of a diet containing dried grape pomace on blood metabolites and milk composition of dairy cows.

The effect of a diet containing 15% grape pomace (GP) on the general health status and milk quality of dairy cows was assessed by plasma biochemistry and total polyphenol (TP) content, milk polyphenols, milk composition and milk protein fractions. Among the polyphenols measured by liquid chromatography-mass spectroscopy in GP, in feed containing GP (GP+) or not containing GP (GP-), gallic acid and epicatechin were present in the highest concentrations (67.58 and 19.23 µg mL-1 , respectively). Higher amounts of TP were also detected in the blood plasma of GP+ cows (114.06 and 83.93 mg GAE L-1 , respectively) but not in their milk (233.17 and 245.75 mg GAE L-1 , respectively). Also a significant increase was found for lactose and β-lactoglobulin, although there was no effect on α-lactalbumin, albumin, secretory components and caseins. Inclusion of 15% GP in the diets of dairy cows is beneficial for overall normal blood constituent metabolism and helps to maintain cow health. The milk of cows fed with a GP diet preserves the normal levels of fat, protein and caseins, and has increased levels of components that make this milk a versatile ingredient material for the food industry (e.g. model whey powders, stability of lactose-rich powders). © 2016 Society of Chemical Industry.

Assessment of dietary ratios of red clover and corn silages on milk production and milk quality in dairy cows.

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 3×3 Latin square changeover design experiment to test the effects of changing from corn (Zea mays) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, and whole-body N and P partitioning. Three dietary treatments with ad libitum access to 1 of 3 forage mixtures plus a standard allowance of 4kg/d dairy concentrates were offered. The 3 treatment forage mixtures were, on a dry matter (DM) basis: (1) R10: 90% corn silage and 10% red clover silage, (2) R50: 50% corn silage and 50% red clover silage, and (3) R90: 10% corn silage and 90% red clover silage. In each of 3 experimental periods, there were 21d for adaptation to diets, and 7d for measurements. Diet crude protein intakes increased, and starch intakes decreased, as the silage mixture changed from 90% corn to 90% red clover, although the highest forage DM intakes and milk yields were achieved on diet R50. Although milk fat yields were unaffected by diet, milk protein yields were highest with the R 0250 diet. Whole-body partitioning of N was measured in a subset of cows (n=9), and both the daily amount and proportion of N consumed that was excreted in feces and urine increased as the proportion of red clover silage in the diet increased. However, the apparent efficiency of utilization of feed N for milk protein production decreased from 0.33g/g for diet R10 to 0.25g/g for diet R90. The urinary excretion of purine derivatives (sum of allantoin and uric acid) tended to increase, suggesting greater flow of microbial protein from the rumen, as the proportion of red clover silage in the diet increased, and urinary creatinine excretion was affected by diet. Fecal shedding of E. coli was not affected by dietary treatment. In conclusion, even though microbial protein flow may have been greatest from the R 0450 diet, optimum feed intakes and milk yields were achieved on a diet that contained a 1:1 DM mixture of corn and red clover silages.

Epigenetic Regulation of miR-29s Affects the Lactation Activity of Dairy Cow Mammary Epithelial Cells.

Milk is important for human nutrition, and enhanced milk quality has become a major selection criterion for the genetic improvement of livestock. Epigenetic modifications have been shown to be involved in mammary gland development; but the mechanisms underlying their effects remain unknown. MicroRNAs are involved in the regulation of milk synthesis and in mammary gland development. Our study is the first to investigate the roles of miR-29s and epigenetic regulation in dairy cow mammary epithelial cells (DCMECs). Our results show that miR-29s regulate the DNA methylation level by inversely targeting both DNMT3A and DNMT3B in DCMECs. The inhibition of miR-29s caused global DNA hypermethylation and increased the methylation levels of the promoters of important lactation-related genes, including casein alpha s1 (CSN1S1), E74-like factor 5 (ElF5), peroxisome proliferator-activated receptor gamma (PPARγ), sterol regulatory element binding protein-1 (SREBP1), and glucose transporter 1 (GLUT1). The inhibition of miR-29s reduced the secretion of lactoprotein, triglycerides (TG) and lactose by DCMECs. Moreover, the treatment of DCMECs with 5-aza-2'-deoxycytidine (5-Aza-dC) decreased the methylation levels of the miR-29b promoter and increased the expression of miR-29b. The link between miR-29s and DNMT3A/3B enhances our understanding of the roles of miRNAs in mammary gland function, and our data will inform more experimentally oriented studies to identify new mechanisms of regulating lactation. We present new insights regarding the epigenetic regulation of lactation performance. Improved understanding of the molecular basis of lactation will aid in the development of strategies for optimizing milk quality in dairy cows and modifying the lactation performance of offspring.

Effect of high-concentrate diet on amino acid transporter expression and milk quality in Holstein dairy cows

In order to evaluate the effect of high-concentrate diet supplementation on milk protein content, six Holstein dairy cows were assigned into high-concentrate diet (HC) or low-concentrate diet (LC) groups (N = 3/group) for 50 days. With regard to milk protein, HC feeding significantly reduced the percentage of milk protein (P < 0.01), and milk protein yield also reduced. The milk somatic cell count numbers and N-acetyl-D-glucosaminidase activity was significantly higher (P < 0.01) in the HC group than in the LC group. A pre-column derivatization procedure of o-phthalaldehyde was used to analyze the milk amino acid profile, the contents of Asp, Gln, Ala, Ile, Leu, and Lys were significantly lower in milk (P < 0.05), but Arg and Phe were significantly higher (P < 0.05) in the HC group than in the LC group. The mRNA abundance for amino acid transporters SLC7A8, SLC7A10 (P < 0.05), SLC1A3 (P < 0.05), and SLC16A10 (P < 0.05) were decreased in the HC group. These data indicate that expression of amino acid transporters alters regulation of amino acid utilization and decreases milk quality in dairy cows.

Citrus pulp as a dietary source of antioxidants for lactating holstein cows fed highly polyunsaturated Fatty Acid diets.

The effects of feeding pelleted citrus pulp (PCP) as a natural antioxidant source on the performance and milk quality of dairy cows fed highly polyunsaturated fatty acid (FA) diets were evaluated. Four lactating Holstein cows were assigned to a 4×4 Latin-square. Treatments, on a dry matter (DM) basis, were i) control diet; ii) 3% soybean oil; iii) 3% soybean oil and 9% PCP and; iv) 3% soybean oil and 18% PCP. When cows fed on citrus pulp, the DM intake tended to decrease. The total tract apparent digestibility of DM and ether extract decreased when cows fed on the control diet compared to other diets. Cows fed PCP had higher polyphenols and flavonoids content and higher total ferric reducing antioxidant power (FRAP) in milk compared to those fed no pelleted citrus pulp. Cows fed 18% PCP showed higher monounsaturated FA and lower saturated FA in milk fat compared with cows fed the other diets. The lowest n-6 FA proportion was in milk fat from cows fed control. The present study suggests that pelleted citrus pulp added to 9% to 18% DM increases total polyphenols and flavonoids concentration, and the FRAP in milk.

Rumen Fermentation and Milk Quality of Dairy Cows Fed Complete Feed Silages

This study was conducted to evaluate the rumen fermentation and milk quality of Friesian Holstein (FH) cows given complete feed silages during lactation. Twelve FH cows in 5 th mo lactation were offered four dietary treatments in a completely randomized design with three replications. The treatments were, control diet (NS) containing 50% concentrate, 45% elephant grass and 5% sun flower meal; grass complete feed silage (GS) containing 50% concentrate, 45% elephant grass and 5% sunflower meal; rice straw complete feed silage (RSS) containing 50% concentrate, 30% elephant grass, 15% rice straw and 5% sunflower and palm oil frond complete feed silage (PKS) containing 50% concentrate, 30% elephant grass, 15% palm oil frond, and 5% sunflower meal. Ensilage was done with addition of Lactobacillus plantarum 1A-2 and cellulase enzyme. Analysis of variance and Duncan test were applied to compare the different among the means of treatments. Complete feed silages had range of pH between 3.89-4.44, temperature of 28.0-29.67 o C and lactic acid bacteria of 0.54-1.50 x 10 8 cfu/g. Crude protein intake of RSS was the highest among treatments. Acetate concentration in rumen liquor was more than 70%. Milk yield and protein were not different among treatments. GS gave the highest milk fat (5.66%). The conclusion was that both complete feed silages, using rice straw or palm oil frond can be used as alternative rations for lactating dairy cows. Key words: complete feed, silage, Friesian Holstein, palm oil frond, rice straw

Effect of Meteorological Condition and Temperature Humidity Index (THI) on Milk Quality of Holstein Cow

Increasing in ambient temperature by global warming is likely to reduce milk yields and negatively affect milk quality in dairy cows. The projected increase in temperature would impact on dairy industry since production costs would increase with reductions in milk production. In Korea, dairy farmers are paid according to the composition of the raw milk components (milk fat concentrations, somatic cell counts and bacteria cell counts). In this study, to assess changes of milk quality caused by ambient temperature and relative humidity in the southern part of Korea (Gyeongbuk province), the temperature-humidity index (THI) was calculated on the base of the equation suggested by Schoen's model. Correlation and regression analysis were performed to determine the effects of the temperature, relative humidity and THI on milk quality. Increased Corresponding author: Jin Wook Kim Tel : +82-55-772-1885 Fax : +82-55-772-1889 E-mail : jinkim@gnu.ac.kr 156 ... Journal of Agriculture & Life Science 47(6) temperature and THI significantly reduced milk fat concentrations from 4.0-4.1% during the winter to 3.6-3.7% during the summer. Occurrence ratio of the 1st grade somatic cell counts (1 SCC) was lower during April to September compared to that of annual average. The THI was negatively correlated to milk fat concentrations (r=-0.8914) and 1 SCC (r=-0.6067) in the overall Gyeongbuk region. There were significant effects of the temperature and THI on milk fat concentrations and 1 SCC. Whereas occurrence ratio of 1A bacteria cell counts (1 BC) had no correlation with the temperature, relative humidity and THI. To make predictions for milk fat concentrations and 1 SCC, the regression model was developed to fit data. Overall, these results suggest that the THI is a useful and easy way to assess the risks of heat stress and is a candidate parameter to predict milk quality.