Effects of dietary concentrate composition and linseed oil supplementation on the milk fatty acid profile of goats.

Milk fat composition can be modulated by the inclusion of lipid supplements in ruminant diets. An interaction between the lipid supplement and the forage to concentrate ratio or the type of forage in the rations may affect milk fat composition. However, little is known about the effects of the starch-to-non-forage NDF ratio in the concentrate and lipid supplementation of goat diets. The aim of this work was to determine the role of dietary carbohydrates in goats rations supplemented with linseed oil on animal performance and milk fatty acid (FA) profile. A total of 16 dairy goats were allocated to two simultaneous experiments (two treatments each), in a crossover design with four animals per treatment and two experimental periods of 25 days. In both experiments alfalfa hay was the sole forage and the forage to concentrate ratio (33:67) remained constant. The concentrate in experiment 1 consisted of barley, maize and soybean meal (concentrate rich in starch), whereas it included soybean hulls replacing 25% of barley and 25% maize in experiment 2 (concentrate rich in NDF). As a result, the starch-to-non-forage NDF ratio was 3.1 in experiment 1 and it decreased to 0.8 in experiment 2. Both concentrates were administered either alone or in combination with 30 g/day of linseed oil. Animal performance parameters were not affected by experimental treatments. In contrast, major changes were observed in milk FA profile due to lipid supplementation and the type of concentrate. Linseed oil significantly raised vaccenic and rumenic acids as well as α-linolenic acid and its biohydrogenation intermediates while decreased medium-chain saturated FA (12:0 to 16:0) in milk fat. Milk fat contents of odd and branched-chain FA and trans-10 18:1 responded differently to linseed oil supplementation according to the concentrate fed.

Near Infrared Spectroscopy (NIRS) for the determination of the milk fat fatty acid profile of goats.

Milk fatty acid (FA) composition is important for the goat dairy industry because of its influence on cheese properties and human health. The aim of the present work was to evaluate the feasibility of NIRS reflectance (oven-dried milk using the DESIR method) and transflectance (liquid milk) analysis to predict milk FA profile and groups of fats in milk samples from individual goats. NIRS analysis of milk samples allowed to estimate FA contents and their ratios and indexes in fat with high precision and accuracy. In general, transflectance analysis gave better or similar results than reflectance mode. Interestingly, NIRS analysis allowed direct prediction of the Atherogenicity and Thrombogenicity indexes, which are useful for the interpretation of the nutritional value of goat milk. Therefore, the calibrations obtained in the present work confirm the viability of NIRS as a fast, reliable and effective analytical method to provide nutritional information of milk samples.

Short communication: Feeding linseed oil to dairy goats with competent reticular groove reflex greatly increases n-3 fatty acids in milk fat.

A crossover experiment was designed to compare the effects of 2 ways of feeding linseed oil on milk fat fatty acid (FA) composition. Ten lactating goats, trained to keep competent their inborn reticular groove reflex, received a daily dose of linseed oil (38 g/d) either with their solid (concentrate) feed (CON) or emulsified in skim milk and bottle-fed (BOT). Two groups of 5 goats received alternative and successively each of the treatments in two 15-d periods. α-Linolenic acid in milk fat rose up to 13.7% in the BOT versus 1.34% in the CON treatment. The n-6 to n-3 FA ratio was significantly reduced in goats receiving bottle-fed linseed oil (1.49 vs. 0.49). Contents of rumen biohydrogenation intermediates of dietary unsaturated FA were high in milk fat of goats under the CON treatment but low in those in the BOT treatment. These results point to a clear rumen bypass of the bottle-fed linseed oil. This strategy allows obtaining milk fat naturally very rich in n-3 FA and very low in trans FA. Translating this approach into practical farm conditions could enable farmers to produce milk enriched in specific FA.

Selecting the best set of gas chromatography-derived fatty acids to discriminate between two finishing diets using linear discriminant analysis.

Linear discriminant analysis (LDA) was investigated as a method for identifying the type of finishing diet fed to bulls (n=169) based on gas chromatography fatty acid (FA) analysis. The bulls were fed ad libitum a high concentrate diet comprised of a cereal-soybean meal based concentrate plus straw offered separately (HC) or a total mixed ration made of cereal, soybean meal, maize silage and straw (TMR). Eleven variables (10 FA and one FA ratio) were selected as statistically significant predictors out of 41 variables tested. The Mahalanobis squared distance between the HC and TMR groups was 3.386 and F-test of the distance was highly significant (P>0.001). In cross-validated classification matrices, 18 cases were misclassified in the HC group and 16 cases were misclassified in the TMR group. As a result, 79.9% of original grouped cases were classified correctly. We concluded that it was possible to classify beef samples according to their finishing diets using LDA.

Time-dependent variations in milk fatty acid content of goats fed 3 different plant oils.

The effect of sampling time on milk fatty acid (FA) composition after separately adding 3 plant oils to an oil-free control diet (67% cereal-soybean-based concentrate and 33% alfalfa hay) was studied in 12 Malagueña goats. Individual animals were randomly allocated to 1 of the 4 treatments: control, 48 g/d of added high oleic (OSO) or regular (RSO) sunflower oil, or linseed oil (LO). Individual milk samples were taken at 0 (covariate), 1, 12, 24, 72, 120, 192, 312, and 504 h after the beginning of the experiment. Milk FA contents (g/100g of total FA methyl esters) were analyzed in a completely randomized design with repeated measures using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Comparing results of 15 chosen FA (for example, medium-chain saturated FA trans-11 C18:1, cis-9,trans-11 C18:2, trans-10 C18:1, and C18:3n-3) indicated that throughout the duration of the experiment, feeding the control diet had little influence on the concentrations of most FA in milk. Most changes in milk FA composition due to oil supplementation had occurred within 192 h since the beginning of the experiment. However, the concentrations of 2 FA (trans-10 C18:1 in RSO and C18:3n-3 in LO treatments) continued to change until 504 h. By comparing FA values in milk fat from oil treatments with those of the control at the same sampling times, typical value differences for the 3 supplementary oils found at 504 h (21 d) were also observed at 312 h from the beginning of the experiment (13 d) and even earlier in some FA, such as medium-chain saturated FA at 120 h in RSO and LO and at 72 h in OSO, cis-9,trans-11 C18:2 and trans-10 C18:1 at 24h in RSO, trans-11 C18:1 at 12h in RSO and LO, and C18:3n-3 at 1h in LO. In the conditions assayed in these experiments, reliable results of milk FA changes were obtained at sampling times shorter than 21 d. Monitoring early changes in milk FA after the addition of plant oils to diets could help in the study of rumen and mammary metabolism of dietary FA.

Short communication: Linear discriminant analysis and type of oil added to dairy goat diets.

Gas chromatography fatty acid (FA) analysis of 112 milk fat samples from dairy goats fed a basal diet with no added oil or the same diet with 1 of 3 vegetable oils added [high oleic sunflower oil (HOSFO), regular sunflower oil (RSFO), or linseed oil (LO)] was used to identify the type of diet consumed through linear discriminant analysis. Twenty variables (19 FA and 1 FA ratio) were selected as valid predictors out of 84 variables tested. The Mahalanobis squared distance was minimal between HOSFO and RSFO groups and maximal between control and LO groups. Cross-validation showed that only one observation from RSFO group was misclassified into the HOSFO group. We concluded that linear discriminant analysis is a useful method to classify milk fat samples from dairy goats according to the particular vegetable oil (of the 3 oils tested here) added to the basal diet.

Effects of feeding increasing dietary levels of high oleic or regular sunflower or linseed oil on fatty acid profile of goat milk.

In this work, the effects of increasing amounts of 3 plant oils in diets on the fatty acid (FA) profile of goat milk were studied. The study consisted of 3 experiments, one per oil tested (linseed oil, LO; high oleic sunflower oil, HOSFO; and regular sunflower oil, RSFO). The 3 experiments were conducted successively on 12 Malagueña goats, which were assigned at random to 1 of 4 treatments: 0, 30, 48, and 66 (H) g of added oil/d. A basal diet made of alfalfa hay and pelleted concentrate (33:67) was used in all of the experiments. For each animal, milk samples collected after 15 d on treatments were analyzed for fat, protein, lactose, and FA composition, whereas individual milk yield was measured the last 3 d of each experiment. Oil supplementation affected neither dry matter intake nor milk production traits. Increasing the oil supplementation decreased the content of saturated FA (especially 16:0) in milk fat and increased mono- and polyunsaturated FA in a linear manner. Vaccenic acid content linearly increased with the oil supplementation by 370, 217, and 634% to 5.32, 2.66, and 5.09 g/100 g of total FA methyl esters with the H diet in LO, HOSFO, and RSFO experiments, respectively. Rumenic acid content linearly increased with LO and RSFO supplementation by 298 and 354% from 0.53 and 0.41 g/100 g of total FA methyl esters with the 0 g of added oil/d diet. The content of trans-10-18:1 was not affected by LO supplementation but showed an increasing linear trend with HOSFO supplementation and linearly increased with RSFO supplementation. The ratio of n-6 to n-3 polyunsaturated FA in milk fat was decreased by about 70% with the H diet in the LO experiment and it was increased by 54 and 82% with the H diet in the HOSFO and RSFO experiments. In conclusion, LO supplementation in this work seemed to be the most favorable alternative compared with HOSFO or RSFO supplementation.

Animal performance and milk fatty acid profile of dairy goats fed diets with different unsaturated plant oils.

The effect of supplementing a basal diet with 1 of 3 plant oils on productive efficiency and milk fatty acid composition was studied in dairy goats. Sixteen Malagueña goats were used in a 4×4 Latin square experiment with 21-d periods and 4 goats per treatment. The basal diet comprised 30% alfalfa hay and 70% pelleted concentrate. Experimental treatments were control (basal diet without added oil) and the basal diet supplemented with 48g/d of high oleic sunflower oil (HOSFO), regular sunflower oil (RSFO), or linseed oil (LO). Dry matter intake and body weight were not affected by treatments. Milk production was higher in HOSFO treatment and milk fat content was higher in RSFO and LO treatments, although no differences in milk energy production or milk renneting properties were found. The RSFO and LO treatments increased the proportion of vaccenic acid in milk fat more so than the HOSFO diet, and rumenic acid followed the same pattern. The content of trans10-18:1 remained low in all experimental diets (<0.7% of total fatty acid methyl esters) although HOSFO and RSFO diets increased it. The variations in the fatty acid profiles observed with the 4 diets, mainly the unsaturated fatty acid isomer contents, are extensively discussed. Compared with that in the control diet, the n-6:n-3 fatty acid ratio in milk fat substantially decreased with the LO, increased with RSFO, and did not change with HOSFO. The addition of moderate amounts of LO to the diets of dairy goats has favorable effects on milk fatty acid composition from the point of view of the human consumer, without negative effects on animal performance.