Meta-analysis of nutritional effects on conjugated linoleic acid (CLA) in milk fat of dairy cows

A meta-analysis was carried out on 41 selected studies to obtain more reliable results about the influence of some nutritional factors on conjugated linoleic acid (CLA) in milk fat. Data were analysed with a linear mixed model, including the study as random variable, that highlighted a significant effect on milk CLA content of fat source and the physical form of the lipid supplement used in the diet. The content of fat in the diet and the forage/concentrate ratio seem do not have significant effects

Nutritional strategies to improve lactation persistency in dairy ewes

Milk production is largely dependent on the shape of the lactation curve. Relevant elements of the lactation pattern are the peak yield, which represents the maximum milk yield during the lactation, and the lactation persistency, which expresses the ability of animals to maintain a reasonably constant milk yield after the lactation peak. Thus, persistent animals are those that show flatter lactation curves. Several measurements of persistency have been proposed (Broster and Broster, 1984; Gengler, 1996): the rate of fall of milk yield per week or per month; combinations of parameters of mathematical functions used to model the lactation curve; the variation of test day yields throughout the whole lactation or part of it; the proportion of total milk yield achieved in a certain period (e.g. second half of lactation). However, none of the above mentioned measurements seems to be able to become the reference method (Grossman et al., 1999). For example, the definition of persistency as the rate of fall of milk yield per unit of time can be misleading if the absolute level of production is not considered. Usually curves with high peak yield show low persistency because the rate of milk yield declines faster in animals that have a fast milk yield increase after calving. Thus in this review, we will consider persistency in a broad sense, and we will analyze the nutritional and nonnutritional factors that affect and limit milk production in mid-late lactation in sheep

Effects of lactation stage, parity, beta-lactoglobulin genotype and milk SCC on whey protein composition in Sarda dairy ewes

In 90 Sarda dairy ewes the effects of lactation stage, parity, beta-lactoglobulin genotypes, and somatic cell count (SCC) on the milk content of total protein (TP), casein (CN), whey protein (WP) and its fractions alpha-lactalbumin (ALA), beta-lactoglobulin (BLG), serum albumin (SA), immunoglobulin (IG) and lactoferrin (LF) were analysed using a linear mixed model. Mean values of variables (g/l) were: TP (54.0), CN (43.0), WP (11.0), BLG (4.78), ALA (1.37), SA (0.61), IG (3.83) and LF (0.28). The lactation stage significantly affected all the variables analysed. TP, CN and WP concentrations tended to increase throughout lactation, with the increase of WP being more pronounced than the corresponding variation in CN. There was no definite trend in BLG content, whereas ALA concentration decreased as lactation progressed. The parity affected almost all variables studied. WP concentration differed significantly only between the second and fourth parity (10.45 vs 11.44 g/l). BLG and SA concentrations were significantly lower in the youngest ewes. The BLG genotype affected milk yield, but no effects were observed on the components of the milk. The SCC influenced almost all variables studied. The TP concentration was significantly higher in milk with SCC >1,000,000 (55.0 g/l) than in milk with lower SCC (53.4 g/l). This was mainly due to the increase of WP (12.52 and 10.24 g/l in milk with SCC above and below 1,000,000/ml respectively), especially in those WP fractions originating from blood

Season and altitude effects on milk fatty acid profile in Sarda dairy sheep flocks

Diet plays a major role in modulating the fatty acid composition of ruminant milk. It is also well known that the intake of fresh forages has a positive influence on polyunsaturated fatty acid (PUFA), particularly CLA and omega- 3, compared with diets based on dry forage and concentrates. Altitude influences, directly, grass availability and botanical composition of the pasture, and, indirectly, the amount of concentrate supplemented to the diet. Therefore, the altitude where farms are located at may give indirect information about the type of feeding system trough analysis of milk fat. The objective of this survey was to investigate variations in the milk fatty acid profile, focusing on the content of vaccenic acid (VA), conjugated linoleic acid (CLA) and n-3 fatty acid (FA), of Sarda dairy ewes flocks located at different altitudes throughout Sardinia. Bulk milk samples were collected in spring (April) and in summer (July) from 36 flocks located at different altitudes: 3 flocks in the lowlands (Low), 3 flocks in the hills (Hill) and 3 in the highlands (High) in 4 provinces (Sassari, Nuoro, Oristano and Cagliari) of Sardinia (Italy). Milk fatty acid profile was analyzed by gas-chromatography. Data were analyzed with a linear model with altitude (A), season (S), province (P) and altitude x season as fixed factors. The interaction was never significant. The season influenced significantly almost all fatty acids analyzed. The proportion of short chain FA (C4-C10) decrease (10.0 vs 7.0 mg/100 mg FA; P<0.01) and that of medium chain FA increase (43.2 vs 45.5 mg/100 mg FA; P<0.10) from spring to summer. The long chain FA did not vary between spring and summer but the concentration of oleic acid (C18:1 cis9) increased significantly from spring to summer (22.3 vs 25.1 mg/100 mg FA; P<0.01). The proportion of n-3 FA was higher in spring than summer (1.2 vs 0.7 for n- 3 FA; P<0.01). The variation in n-3 FA in milk fat was mainly due to the variation in a-linolenic acid (ALA; 18:3n- 3) which decrease from 1.0 to 0.5 mg/100 mg FA from spring to summer. The same pattern was showed by vaccenic acid (VA; trans-11 18:1) that decrease from 1.6 vs 0.8 mg/100 mg FA. No variation in cis9, trans11 CLA has been observed between spring and summer (1.0 vs 0.8 mg/100 mg FA). A reduction of PUFA (5.64 vs 5.10; P<0.10), n3/n6 ratio (0.38 vs 0.21) and content of C20:5 n-3 (0.13 vs 0.07 mg/100 mg FA) from spring to summer has been observed. Unexpectedly, the milk FA profile was not affected by altitude, except for C18:1 c9, probably because of the low number of samples analyzed

Comparison of conjugated linoleic acid (CLA) content in milk of ewes and goats with the same dietary regimen

Milk fat is an important source of potential anticarcinogens named conjugated linoleic acid (CLA). The c9, t11-CLA is the major isomer and it is produced by ruminal hydrogenation of linoleic acid that leads first to vaccenic (11t-18:1) and finally to stearic acid (18:0). An alternative CLA pathway is related to the action of the mammary Δ9-desaturase enzyme on 11t-18:1. Diet is considered the main factor that influence the CLA concentration in milk fat. Differences in CLA content of sheep (Antongiovanni et al., 2002) and goats milk (Nudda et al., 2002) have been hypothesized, but results are difficult to compare due to different experimental condition in which the trials are carried out. The aim of this work is to compare the composition of milk fatty acids and CLA content in goats and sheep maintained in the same environmental condition and dietary regimen

Milk composition and feeding in the Italian dairy sheep

Milk production represents a relevant quota of the energy consumption of the dairy ewe. Studies on relationships among level of production, milk composition and metabolic aspects are the first fundamental step in the development of a feeding system aimed at satisfying nutritive requirements of the animals. This paper reviews the knowledge about the milk composition of main Italian dairy sheep breeds, the relationship among secretion kinetics of milk and protein and productive level of animals, the algorithms used for estimating fat (6.5%) and protein (5.8%) corrected milk yield, the evolution over time of milk production during lactation and the relationships between feeding and milk composition

Comparison of fatty acid profile in lamb meat and baby food based on lamb meat

The aim of this study was to compare the fatty acid (FA) profile of fresh lamb meat with those of baby foods based on lamb meat. For this purpose, samples of commercial homogenized (HO) and lyophilized (LIO) baby food based on lamb meat and fresh lamb meat (FM) were analyzed for their FA composition. All fatty acids, except for oleic acid and conjugated linoleic acid (CLA), differed among the three baby products tested. The sum of omega-6 FA and the ratio omega 6/omega 3 FA were lower in FM and LIO meat compared to HO samples. The content of total PUFA n-3 was the highest in FM, because of its highest content of C18:3 n3, EPA, DPA and DHA compared to LIO and HO baby food. The content of arachidonic acid was more than 6-fold higher in FM compared to LIO and HO. This study evidenced the possibility of enhancing the FA profile of commercial baby food based on lamb meat by using meat with healthier FA profile

Fatty acid profile of milk fat in goat supplemented with iodized salt

Iodine is an essential nutrient of the human and animal diet which is needed for the synthesis of the thyroid hormones. These hormones play an important role in the regulation of fat metabolism. In fact, increased thyroid hormone levels stimulate fat mobilization, leading to increased concentrations of plasma triglyceride (Nikkila and Kekki, 1972) and enhanced oxidation of fatty acids in many tissues. Recently, Bauman et al. (2006) showed the involvement of a protein called spot 14, highly responsive to thyroid hormones, in the regulation of the mammary synthesis of milk fat. However, the effects of Iodine supplementation on plasma and milk fatty acid profile in dairy animals has not been elucidated yet. The aim of this study was to evaluate if the fatty acid (FA) profile of milk changes in goats supplemented with Iodine. Thirty crossbreed dairy goats were divided into 3 groups were used and supplemented with 0 (group 0), 450 (group 1), or 900 (group 2) μg of KI/day per head. Each dose of KI (76.5% of Iodine) was orally administered in water every day for 8 weeks. Milk yield was recorded and milk samples were collected every two weeks. A total of 120 milk samples were analyzed by gas chromatography (GC). Milk yield was not influences by treatments. Milk fat content was the highest (P<0.01) in group 1 (4.65%) compared to group 0 (4.15%) and group 2 (4.17%). Iodine treatments did not influence milk fatty acid profile except for the content of some short-chain fatty acids. In particular, only the contents of C8:0 FA (2.22, 2.24 and 2.12 in groups 0, 1 and 2, respectively; P<0.01) and C10:0 (9.74, 9.49 and 9.02 in groups 0, 1 and 2, respectively; P<0.01) decreased due to supplementation with the highest dose of KI. In conclusion, in this study Iodine supplementation did not show substantial effects on goat’s milk FA profile, probably due to the low doses of KI used. Nevertheless, the observed decrease of some short-chain fatty acids, which are synthesized ex-novo by the mammary gland, in goats supplemented with the highest KI dose tested is compatible with a potential involvement of Iodine or thyroid hormones in the regulation of fat synthesis in the mammary gland

Infusion of casein hydrolizates into the mammary gland simulates the omission of one daily milking in goats

Suppression of one daily milking at weekends, even though socially desirable, may reduce milk yield. These losses have been attributed to a short-term mechanism: the filling of the cistern and ductal-alveolar system with milk which contains a peptide called feedback inhibitor of lactation (FIL) (Wilde and Peaker, 1990). The FIL probably reduces the synthesis and secretion of mammary cells by blocking the potassium channel of the apical membrane (Silanikove et al., 2000). Shamay et al. (2002) hypothesized that the FIL can be identified with the AA sequence 1-28, derived from the breakdown of β-casein by plasmin (PL). The aim of this work was to verify if the infusion of casein hydrolizates (CNH) into the mammary gland simulates the omission of one milking for two consecutive days

Effect of dietary oil supplementation on fatty acid profile of backfat and intramuscular fat in finishing pigs

Two groups of finishing gilts were fed, for 4 weeks, a commercial feed enriched (2%) with either rapeseed oil or sunflower oil. Pig growth was monitored bi-weekly and the fatty acid composition of backfat and Longissimus muscle was determined after slaughtering. Type of dietary oil affected significantly the fatty acid profile of pork fat, especially the C18:3n-3 concentration which was higher in pigs fed rapeseed oil than in those fed sunflower oil. The content of monounsaturated fatty acids (MUFA) of Longissimus muscle was significantly higher than that of backfat, due to the its higher concentration of C18:1cis9 and C16:1. Differently, the long-chain n-3 polyunsaturated fatty acids (PUFA) content was higher in backfat than in Longissimus muscle. These results confirm that it is possible to manipulate the fatty acid composition of the diet, in order to improve the health properties of the adipose tissues of pork meat