Quality Of Milk Fat Research Articles

Effect of supplementary glycerin on milk composition and heat stability in dairy goats.

ObjectiveThis experiment was studied the effects of various levels of crude glycerin (CG) in dairy goat diet on daily intake, milk yield, milk composition, some physical properties and some quality changes of goat milk after sterilization.MethodsTwelve 75% Saanen dairy goats (body weight = 49±3 kg; days in milk = 60±12 d) were randomly assigned in a completely randomized design to evaluate the effects of three experimental diets consisting of 0%, 5%, and 10% CG (dry matter basis) which were formulated to meet or exceed the nutrient requirements of goats. Experimental dairy goats were evaluated for feed and milk yield. Milk samples were analyzed for their composition, including fatty acids, casein profile, fat globule size, and color, and were sterilized to evaluate milk heat stability.ResultsThere were no significant differences between 0% and 5% CG treatments infeed. Increasing CG supplementation from 0% to 5% increased milk yield from 2.38±0.12 to 2.64±0.23 kg/goat/d. In addition, milk samples from 5% CG treatment had the highest total solids, fat content and lactose content, and largest fat globule size. Increasing CG to 10% resulted in a decrease in milk fat. After sterilizing at 116°C, F0 = 3 min, goat milk samples from 5% CG treatment had slightly higher sediment content and comparatively higher degree of browning.ConclusionConsidering milk yield, milk fat content and quality of sterilized milk, 5% CG supplementation in a total mixed ration has a potential for implementation in dairy goats.

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<0.05). Milk yield in RS (19.5 kg/d) was higher compared to R (17.6 kg/d, P<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<0.05). Experimental diet (RS) compared to control (R) had higher (P<0.05) content of unsaturated FA (31.64 % and 30.69 %, respectively). Content of polyunsaturated FA in RS (4.03 %) was significantly higher (P<0.05) than in R (3.66 %) mainly due to differences in C 18:2n6c, C 18:3n6 and C 18:3n3 FA (P<0.05). Proportion of short-, medium- and long-chain FA was similar in both groups (P>0.05). PI was higher (P<0.05) in RS than in R being 5.54 and 5.06, respectively.

Selected candidate genes affecting milk fatty acids

Cow´s milk consisted of relatively high quantity of saturated fatty acids (about 70%), which are considered less beneficial health. The content of more desirable fatty acids is about 25% (monounsaturated) and 5% (polyunsaturated). The aim of this research was to find ways how to increase the content of mono- and polyunsaturated fatty acids in milk fat. One of the ways how to alter the content of fatty acids is the monitoring of candidate genes and their polymorphism. Therefore, the manuscript deals with selected candidate genes, particularly DGAT1 , SCD1 and FASN , which are associated with fatty acid biosynthesis. The results suggest that observing of this issue could be helpful for improving the quality of milk fat.

Effects of automatic cluster removal and feeding during milking on milking efficiency, milk yield and milk fat quality.

In order to increase milking efficiency, the effects of two different cluster take-off levels (200 and 800 g/min) and feeding vs. not feeding during milking were tested in a Latin square design study including 32 cows. Milk yield, milking time, milk flow and milking interval were measured and milk samples were analysed for gross composition, sodium and potassium concentration, free fatty acid (FFA) content, milk fat globule (MFG) size, MFG membrane (MFGM) material and fatty acid composition. Residual milk was harvested to evaluate udder emptying. Increasing the take-off level from 200 to 800 g/min at the whole udder level decreased milking time and increased harvest flow. Udder emptying decreased slightly, but there were no effects on milk yield, FFA content or MFGM. There were interactive effects of take-off level and feeding during milking on content of fatty acids C4:0, C6:0, C16:0, C18:3(n-3) and C20:0. Feeding during milking increased milk yield per day and decreased milking interval. Sodium and potassium concentrations in milk were unaffected by treatments, indicating no loss of tight junction integrity. From these results, it is clear that feeding during milking should be used to increase milk yield and improve milking efficiency, regardless of take-off level used, and that the effect of feeding is more pronounced when a low take-off level is used. Feeding seemed to counteract the effects of the low take-off level on milking time and milking interval. Low take-off levels can therefore be used in combination with feeding.

Modifying milk and meat fat quality through feed changes

Feeding is the major factor affecting the quality of sheep products (milk and meat). The feeding strategies useful for increasing the levels of healthy fatty acids (FA), such as conjugated linoleic acid and omega-3 FA, in milk and meat in the human diet are reported. The addition of supplements rich in oils and the level and quality of forage seem to be valuable tools for influencing the fatty acid composition of milk and lamb meat. The use of alternative feed resources such as grape pomace, rich in phenolic compounds, in sheep and lamb diets and their effects on meat FA composition and oxidative stability are also discussed.

Perfil de ácidos graxos do leite de vacas Holandês x Gir em pastagem de capim-marandu suplementado com quantidades crescentes de grão de soja tostado

O experimento foi realizado na Embrapa Gado de Leite, em delineamento quadrado latino (QL) 4x4, com o objetivo de avaliar o perfil de ácidos graxos (AG) e os índices de qualidade nutricional da gordura do leite de vacas Holandês x Gir (n = 16) sob pastejo em Brachiaria brizantha cv. Marandu suplementada com concentrado (6kg/vaca/dia) contendo 0; 1,3; 2,6 e 3,9kg (base matéria natural) de grão de soja tostado (GST). Foram observados decréscimos lineares (P<0,0001) nas concentrações e nas secreções dos AG láurico, mirístico e palmítico e dos AG de cadeia ímpar linear e ramificada, bem como incrementos lineares (P<0,0001) nas concentrações e secreções dos AG α-linolênico, linoleico, oleico e esteárico na gordura do leite, com a inclusão do GST no concentrado. As concentrações e as secreções dos AG vacênico e rumênico apresentaram comportamento quadrático (P<0,001) em resposta à inclusão de quantidades crescentes de GST na dieta. As alterações observadas no perfil de AG do leite com o aumento da inclusão de GST no concentrado resultaram em reduções lineares (P<0,0001) nos índices de aterogenicidade e de trombogenicidade e em incrementos lineares (P<0,0001) nas relações entre AG hipo:hipercolesterolêmicos e entre AG ω-6:ω-3 da gordura do leite. Os resultados deste estudo mostraram que a inclusão de quantidades crescentes de GST na dieta de vacas Holandês x Gir pastejando capim-marandu apresenta potencial para a secreção de leite com gordura enriquecida com ácidos graxos benéficos à saúde humana.

Changes in lipid oxidation of reconstituted omega-3 plus milk powder treated by superheated steam

In this study the effect of superheated steam on the oxidative stability of reconstituted omega-3plus milk powder was studied. The changes in fatty acids, peroxide, acids, thiobarbutric acid reactive substances (TBARS), and p-anisidine values were measured to reconstitute omega-3 plus milk powder in relation to thermal treatment by using a superheated steam (SHS) with different temperatures and time periods. The temperature and time period ranged from 120-180 °C between 5-15 min. For applying the SHS treatment did not produce changes in SFA, MUFA and PUFA at 120-150 °C to 10-15 min as compared with the control. While, the proportion of PUFA and MUFA values were recorded differences on temperature 180 °C comparison with control. The result of POV showed no changes between the temperature 120-150 °C compared with control, but indicated significant differences at the temperature 180 °C with long time 15 min. Acids and p- anisdine values did not show any differences between temperature 120-180 °C for a short period of time 5 min compare with the control, but recorded significantly on long period of time 10-15 min compared with the control. The values of TBARS showed no significant differences in temperature 120-150 for 5 min compare with control. This study showed oxidative stability of milk fat supplied long chain unsaturated fatty acids treated by SHS on temperature range 120-150 at time 5-10 min with some affected by the high temperature 180 °C at 15 min can maintain the quality of fatty acid and milk fat.

Conjugated Linoleic Acid (Cla) Concentration and Fatty Acid Composition of Brazilian Fermented Dairy Products

Fermented dairy products have been widely studied due to their nutritional importance and functional properties. Milk fat has a complex composition; even though it is a rich source of saturated fatty acids, which have been associated with increased risk of cardiovascular diseases. In this context, this study was aimed to know the fatty acid profile, evaluating the milk fat quality of whole fermented dairy products with registration in the state or federal inspection and highlight their importance to consumers’ health. Samples of yogurt and fermented dairy beverages were collected to evaluate the fatty acids composition. The predominance of saturated fatty acids was observed: myristic, palmitic and stearic acids, also indicating the presence of unsaturated fatty acids: oleic, linoleic and vaccenic, besides the content (g/100 g of fatty acids) of conjugated linoleic acid ranging from 0.290 to 1.15 for yogurts and 0.546 to 0.640 for dairy beverages. Thus, the fatty acid profile of fermented dairy products has similar composition comparing the inspection registration type, besides being a source of fatty acids beneficial for health.

Desempenho produtivo e perfil de ácidos graxos do leite de vacas que receberam níveis crescentes de óleo de girassol em dietas à base de capim-elefante

Este experimento teve como objetivo principal avaliar as alterações no perfil de ácidos graxos do leite decorrentes do fornecimento de diferentes níveis de óleo de girassol (OG) para vacas leiteiras alimentadas com dietas completas à base de capim-elefante. Doze vacas da raça Holandesa receberam quatro níveis de OG na dieta (0; 1,3; 2,5 e 3,7% da MS) em delineamento quadrado latino 4 x 4. Não houve efeito (P>0,05) dos níveis de OG sobre o consumo de MS, a produção de leite ou os teores de sólidos do leite. Por outro lado, o perfil de ácidos graxos (AG) do leite foi amplamante modificado com a inclusão de OG na dieta, e observou-se redução (P<0,0001) dos teores dos AG de cadeia curta e média, elevação dos teores de ácido oleico (P<0,0001), dos isômeros de ácido linoleico conjugado, em especial do ácido rumênico (P<0,0001) e da relação entre os ácidos graxos hipo e hipercolesterolêmicos (P<0,0001). Apesar da maior ingestão diária de ácido linoleico (P<0,01) com o aumento do nível de OG na dieta, sua concentração na gordura do leite não foi alterada. Isso indica extensiva bio-hidrogenação ruminal deste AG no rúmen, o que é compatível com o aumento (P<0,0001) da concentração de ácido esteárico e dos AG C18:1 trans, especialmente do vacênico, na gordura do leite. Em geral, os resultados observados no presente estudo indicam que a inclusão de até 3,7% de OG em dietas completas de vacas leiteiras à base de capim-elefante promove melhoria da qualidade nutricional da gordura do leite, sem comprometimento do desempenho produtivo dos animais.

Effects of the heating process of soybean oil and seeds on fatty acid biohydrogenation in vitro

Heating fat is an efficient way to alter ruminal biohydrogenation (BH) and milk fat quality. Nevertheless, results are variable among studies and this could be due to various heating conditions differently affecting BH. The objectives of this study were to determine the effect of type and duration of heating of soybean oil or seeds on BH in vitro. Ruminal content cultures were incubated to first investigate the effects of roasting duration (no heating, and 0.5- and 6-h roasting) at 125°C and its interaction with fat source (soybean seeds vs. soybean oil), focusing on linoleic acid BH and its intermediates: conjugated linoleic acid (CLA) and trans-C18:1. Additionally, we compared the effects of seed extrusion with the 6 combinations of unheated and roasted oils and seeds. None of the treatments was efficient to protect linoleic acid from BH. Soybean oil resulted in higher trans-11 isomer production than seeds: 5.7 and 1.2 times higher for cis-9,trans-11 CLA and trans-11 C18:1, respectively. A 125°C, 0.5-h roasting increased trans-11 isomer production by 11% compared with no heating and 6-h roasted fat. Extrusion of seeds was more efficient to increase trans-11 C18:1 production than seed roasting, leading to values similar to oils. For other fatty acids, including cis-9,trans-11 CLA, extrusion resulted in similar balances to seeds (mainly 0.5-h-roasted seeds). Extruded oilseeds would be more efficient than roasted seeds to produce trans-11 C18:1; nevertheless, effects of conditions of extrusion need to be explored.

Evaluación del Residuo del Cultivo de Agaricus bisporus como Alimento de Vacas Lecheras en Lactancia Media

Se evaluó el potencial del residuo del cultivo de la seta Agaricus bisporus como materia prima para la alimentación de vacas lecheras en segundo tercio de lactancia. Para esto, se sustituyó 10% del concentrado comercial por el residuo (sin turba) y se evaluó su efecto en la producción, el balance nutricional de las vacas y el costo final del concentrado. El diseño experimental fue un cross-over o de intercambio con medidas repetidas en el tiempo. Cada periodo experimental tuvo una duración de 14 días. Se utilizaron dos grupos de animales, uno con 4 vacas Holstein y otro con 4 vacas cruzadas Holstein x BON. En promedio, las vacas tenían 117 ± 18,6 días en leche, 2,6 ± 0,9 partos, 529,5 ± 52,9 kg peso vivo y una producción de leche/día de 15,42 ± 2,6 L. El tratamiento experimental redujo los nutrientes digeribles totales de la dieta total en 2%. No hubo diferencias estadísticas en el balance nutricional de las vacas a causa del tratamiento experimental. Tampoco hubo diferencia estadística en cuanto a la producción de leche (14,4 L) y calidad composicional (% de grasa:3,86; % de proteína: 3,5; relación grasa: proteína: 1,11). El análisis de costos mostró que al incluirse en el concentrado un 10% del residuo de A. bisporus (Champiñosa) se obtenía una reducción en los costos de alimentación de $403 pesos colombianos/vaca/día.

Milk fat quality of Greek buffalo (Bubalus bubalis)

A study was conducted with 40 Greek buffalo cows (Bubalus bubalis) to evaluate the effect of lactation stage (3rd to 8th month after parturition; September 2009 to February 2010) on the quality of milk fat, relative to lipid, fatty acid and cholesterol contents. The lipid content steadily increased from 3rd to 8th month after parturition, while the lipid content and lactation stage and/or environmental temperature influenced the fatty acid profiles. During the 6th, 7th and 8th month after parturition (colder winter months), the fatty acids with lower melting point (unsaturated) were detected at higher concentrations in order to contribute in the reduction of melting point of total lipid. The fatty acids butyric (C4:0), vaccenic (C18:1ω-7 trans-11) and rumenic (C18:2 cis-9, trans-11) remained stable throughout the study. Cholesterol content was found at levels lower (70–90mgkg−1 buffalo milk) than in cow and goat milk samples reported in literature.

Production, composition and antioxidants in milk of dairy cows fed diets containing soybean oil and grape residue silage

Four primiparous Holstein cows averaging 504kg of body weight and 136 days in milk were used in a 4×4 Latin square design with four 21 days experimental periods to determine the effects of feeding four concentrations (0, 50, 75 and 100g/kg of dry matter (DM)) of grape residue silage on DM intake, total tract apparent digestibility (TTAD), milk production, milk composition, milk fatty acid profile and milk concentration of antioxidants when cows were fed a diet containing soybean oil. Intake of DM and nutrients was similar among diets, except for intake of ether extract (EE) which increased with the proportion of grape residue silage in the diet. The TTAD of DM, crude protein (CP), EE, acid detergent fiber and neutral detergent fiber decreased linearly with higher proportions of grape residue silage in the diet. Milk production and concentrations of CP, fat and lactose were similar among treatments, but increased levels of grape residue silage reduced milk urea N content. There was a little effect of diet on milk fatty acid composition, although there was a trend to increased proportion of polyunsaturated fatty acids in milk fat when feeding increased levels of grape residue silage. Concentrations of total polyphenols and flavonoids, and production of conjugated diene hydroperoxides in milk, were not altered by diets. Reducing power in milk was higher with increased dietary levels of grape residue silage. Results suggest that it is possible to improve milk fat quality by feeding cows with grape residue silage as shown by enhanced antioxidant activity, although it was clearly insufficient to overcome the negative effects on milk fat synthesis probably caused by the high levels of fat added to diets as soybean oil.

Development of a near Infrared Method for the Quantification of the Main Classes of Fatty Acids Obtained from Raw Milk by Solvent-Free Extraction

The determination of the fatty acid (FA) profile of milk fat, which is the most complex dietary fat, is more and more for both the definition of nutritional labelling and the study of the genetic variability in bovine milk fat quality. For these reasons, the development of infrared techniques for the rapid evaluation of FA profiles is gaining much wider interest. In this research, a method for the rapid determination of saturated, unsaturated, monounsaturated, polyunsaturated and trans FAs, expressed on 100g of total milk FAs, is reported. The FA profile was estimated from the transmission spectrum (optical pathlength of 6 mm) obtained from the fat extracted by hot centrifugation, without solvents. Authentic triglyceride standards were used in order to perform the spectral band assignments. The whole data set included 135 raw milk samples collected from cows fed either a total mixed ration or grazed on mountain pastures. Ninety five samples were selected for model development (calibration set); the prediction models were then validated by an independent validation set composed by 40 samples. The prediction model for the saturated FA content showed a correlation coefficient of determination ( r2) = 0.96, standard error of prediction ( SEP) = 0.97 (g 100 g−1 of total FAs), ratio of errors ( RER) = 22.8 and ratio of performance to deviation ( RPD) = 4.6. Monounsaturated, polyunsaturated and trans FAs provided r2 = 0.95, 0.90 and 0.97, RER = 20.4, 12.5 and 32.1 and RPD = 4.2, 2.8 and 5.2, respectively. The ability to predict the concentration of some saturated single FAs, also grouped according to their chain length, was also investigated. Satisfactory screening performances were found for C14, C16 and C18 FAs, as well as for the amount of the groups including medium (12–17 carbon atoms) and long (18–22 carbon atoms) FAs.

Interannual and geographical reproducibility of the nutritional quality of milk fat from commercial grazing flocks

The objective of the present work was to study the differences in the fatty acid (FA) composition of raw sheep milk fat under commercial milk production conditions throughout lactation, in two consecutive years. Particular attention was placed on the C18:2cis-9,trans-11 isomer, C18:1trans-11 acid, and unsaturated FA as the feeding regimen of 10 commercial flocks of latxa dairy sheep changed from indoor feeding to part-time grazing conditions (from early spring) as traditionally practiced in the Basque Country (Northern Spain). Farms located at an altitude of between 600 and 700m, in two different geographical areas with different rainfall were selected. Milk samples were collected monthly from late January (indoor feeding) until mid-, or end of, June (outdoor feeding), during two consecutive years. In spite of some interannual variability (most likely due to large differences in rainfall), the evolution of individual FA throughout lactation was comparable between years, indicating that it was reproducible under commercial milk production conditions. The average concentrations of C18:2cis-9,trans-11 isomer and C18:1trans-11 acid in milk from the commercial flocks increased about 200% during the transition period (end of March or early April until May), from indoor feeding (late January or early February until the end of March) to the outdoor period (early May to mid-June), remaining constant during the outdoor period (27·53±9·32μmol/g fat and 71·58±20·53μmol/g fat, respectively). Non-atherogenic FA comprised approximately 50% of all saturated FA at any time during lactation, whereas the milk atherogenicity index decreased significantly during the outdoor period. The Trolox-equivalent antioxidant capacity of the water-soluble milk fraction did not appear to be influenced by feeding management. The FA composition of cheeses made during the second year with milk from the indoor or outdoor periods reflected those of the corresponding milks. A principal components analysis clearly showed that differences in the milk FA composition were primarily due to outdoor grazing, with very little contribution from the geographical zone or the year.

PCR-SSCP analysis of leptin gene and its association with milk production traits in river buffalo (Bubalus bubalis)

Leptin gene has been found to be associated with various economic traits including milk production and fat quality in dairy animals. In the present study, we investigated genetic variations in intron 1 region of leptin gene in riverine buffaloes (Bubalus bubalis) using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequencing methods and associated them with milk traits. The study revealed three SSCP variants A, B and C among a total of 301 buffaloes from nine breeds. The frequency of variant C was found invariably high among all the breeds except in Marathwada buffalo. Variant A was found to be absent in Chilika, Nili-Ravi, Nagpuri and Pandharpuri breeds and also had the lowest frequencies in Mehsana, Jaffarabadi, Murrah and Toda breeds. Sequencing of SSCP variants revealed a total of five polymorphic sites, with three haplotypes. Statistical analysis revealed significantly high fat percentage at 150 days in SSCP variant B in Mehsana buffaloes. However, the associations of SSCP variants of leptin gene with total milk yield, 305 days milk yield and total fat yield were found to be non-significant. The present study is the first report on association analysis of leptin gene polymorphisms with milk production and milk quality traits in river buffalo.

Phytanic acid content and SRR/RRR diastereomer ratio in milk from organic and conventional farms at low and high level of fodder input

Milk quality has an important role in organic farming due to the obligation to a maximum use of pasturage for herbivores. Markers should be identified to confirm the authenticity of organic milk production. The concentration and SRR/RRR diastereomer ratio of phytanic acid were investigated as potential markers to discriminate different feeding strategies. In a two-factorial design, 80 farm milk samples were compared for their ‘origin’ and ‘level of intensification’, both during the grazing season and the indoor season. In all groups the concentration of phytanic acid in winter was about 50 % lower than in summer. A strong negative correlation was found between the sum amount of concentrates plus maize silage in the cow’s diet and the phytanic acid level. In winter, cows fed with hay had lower phytanic acid levels than cows fed grass silage. The differentiation of low-input and high-input systems was more consistent than the differentiation between biodynamic and conventional samples based on the combination of phytanic acid and SRR/RRR ratio. The SRR/RRR ratio was an indication for the factor ‘intensification’, whereas the concentration of phytanic acid reflected the factor ‘origin’. The SRR/RRR ratio is therefore a marker for the grazing policy in summer and the differentiation between hay versus grass plus maize silage in winter diets. Organic farming could lose its characteristic features reflected in several aspects of milk fat quality if grazing during summer is reduced and replaced by larger amounts of concentrate and maize silage.

Effects of breed on milk fatty acid profile in dairy ewes, with particular reference to <i>cis-9, trans-11</i> conjugated linoleic acid

The objective of this study was to determine and compare the fatty acid profile of milk fat, with particular reference to cis-9, trans-11 conjugated linoleic acid (CLA), in two indigenous Romanian sheep breeds (Spanca and Turcana), irrespective of the effects of diet and season. The ewes (n = 25 for each breed) received the same feed (total mixed rations) and were maintained under identical conditions. Four samples were collected from each individual ewe to determine fatty acids (FA), as methyl esters, using gas chromatography. The fatty acid groups, namely saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) acids were examined together with individual acids. Differences have been obtained between the two local breeds for the majority of FA. Fat in the milk of Turcana ewes has a healthier fatty acid profile than that of Spanca breed which has a lower concentration of SFA (60.9 vs. 73.3%) and higher concentrations of MUFA (31.0 vs. 21.0%) and PUFA (8.06 vs. 5.61%, respectively). Compared with the Spanca breed, fat in the milk of Turcana ewes had higher concentrations of trans -11 C18:1, C18:1 n9c, and cis-9 trans-11 CLA (2.67 vs. 1.01%, respectively). Δ 9 -desaturase activity is breed specific; vaccenic acid (trans-11 C18:1) desaturation and its conversion into cis-9, trans-11 CLA were more intense in the Turcana breed ewes. In conclusion, breed has a strong effect on the FA composition of ewe milk fat, and on cis-9, trans-11 CLA, in particular. The results obtained, support the sustainable use of animal genetic resources to improve the milk fat quality of ewes. Keywords : CLA, ewe’s milk, fatty acid profiles, Spanca, Turcana

Suitability of bronopol preservative treated milk for fatty acid determination

This work aimed to test if milk preserved with bronopol can be reliably used for fatty acid determination. Dairy production and milk quality are often monitored regularly to assess performance and contribute to selection indices. With evidence that fat composition can be influenced by selective breeding, there might be an interest in using samples collected in routine testing to evaluate individual cow fatty acid profiles, contributing to breeding indices. However, most recording services use a preservative such as bronopol and there is no published record if this influences subsequent fatty acid analysis. This study used milk from an oil seed supplementation trial, generating a wide range of milk fatty acid profiles, to test if the concentration of 31 individual fatty acids determined by GC were influenced by bronopol. Provided preserved samples are subsequently frozen, milk treated with bronopol can reliably be used to evaluate fatty acid composition in most cases; however bronopol might influence a few long-chain fatty acids present in relatively low concentrations. This is one small step towards simplifying milk compositional analysis but it could ultimately streamline the inclusion of milk fat quality into breeding indices, either with a view to 'healthier' milk or potentially reducing methane output and the environmental impact of dairy production.

Flowering catch crops used as forage plants for dairy cows: Influence on fatty acids and tocopherols in milk

The effect of several flowering dicotyledonous catch crop plants (dicots) on milk fat quality in cows was investigated to test the hypothesis that their phenolic compounds may inhibit ruminal biohydrogenation and thus enhance the transfer to milk of intact, plant-derived polyunsaturated fatty acids. Berseem clover (Trifolium alexandrinum), buckwheat (Fagopyrum esculentum), and phacelia (Phacelia tanacetifolia) were sown in mixture with ryegrass (Lolium multiflorum; intended biomass proportion of 0.2) on 1ha. For comparison, nonflowering chicory (Cichorium intybus, also sown in mixture with ryegrass) and pure ryegrass were cultivated. Realized biomass proportions (wet weight) were 91% for berseem clover, 69% for buckwheat, 54% for phacelia, and 51% for chicory. At the start of flowering (or from d 47 after sowing onward), cultures were harvested daily and fed for 20 d ad libitum to groups of 6 midlactation cows each. Additionally, 1kg each of energy and protein concentrate and pure ryegrass hay were fed. Individual intake and milk yield of the cows were measured daily. Milk samples were obtained twice daily 5 d before and from 11 to 20 d after the start of treatment feeding. Feed samples were drawn twice a week from the fresh feeds. Apart from standard traits, feeds and milk were analyzed for fatty acids, tocopherols, and phenolic fractions. Only a few substantial treatment effects on intake and performance were observed. All diets based on dicots increased α-linolenic acid (ALA) concentrations in milk fat compared with the ryegrass diet even though the corresponding swards were not generally richer in ALA. The highest ALA concentration in milk fat (1.3 g/100g of fatty acids) occurred with the berseem clover diet. Transfer rate of ALA from feed to milk was highest with the buckwheat diet (0.09) and lowest with ryegrass (0.05). This was congruent with the differences in total extractable phenols, being high in the buckwheat sward (2.6% of dry matter) and low in the ryegrass sward (1.2% of dry matter). Intermediates of ALA biohydrogenation were lowest in the milk fat of the buckwheat group, indicating an inhibitory effect of this treatment, which provided the highest dietary levels of phenols. The α-tocopherol concentration in milk was higher with the buckwheat diet than with berseem clover and phacelia diets. The study provides evidence that the ALA concentration in milk fat could be enhanced by feeding flowering dicots; however, this was due to different modes of action.