224 research outputs found
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
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
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
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
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
Grape seed and linseed, alone and in combination, enhance unsaturated fatty acids in the milk of Sarda dairy sheep
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) ÎĽg 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
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