1,721,385 research outputs found
Designing milk fat to improve healthfulness and functional properties of dairy products: from feeding strategies to a genetic approach
No full textThe present review, in the first part, deals with the most effective feeding strategies applied to dairy ruminants in order to enhance the healthfulness of milk fat. The largest changes in milk fatty acid (FA) composition have been obtained either by changing the amounts and the nature of forages in the diets of ruminants, particularly pasture, or by adding plant or marine oils to the diet. Alpine and legume based pastures are associated with high levels of conjugated linoleic acid (CLA), omega-3 FA and with low levels of saturated FA, but further studies are needed with the aim to better explain the effect of some plant species on milk FA composition. Linseed, soybeans safflower and sunflower are the most effective sources of unsaturated plant lipids used to enhance CLA and unsaturated FA content in milk fat. Among animal sources, marine oil is more effective than plant oils for enhancing CLA, vaccenic acid (VA) and omega-3 FA in milk fat, especially when fish oil is fed in combination with oil supplements rich in linoleic acid. In the second part of the review the potential contribute of genetic improvement to modifying milk FA composition is discussed. Recent studies have suggested that the genetic improvement of the nutritional quality of milk based on FA profile may be possible. At this aim, genetic parameters of milk FA composition have been estimated in Dutch, US and Italian Holstein populations and in a Belgian multiple breed population of dairy cows. In dairy sheep and goat there is still a lack of knowledge about genetic parameters and correlations of milk FA. The develop of specific selection indexes aimed to improve the nutritional properties of milk could be supported by the new insight about potential candidate genes able to affect a significant quote of the milk FA variability. Increasing evidences indicate the Stearoyl-CoA Desaturase (SCD) and Diacylglycerol acyltransferase (DGAT-1) genes as possible sources of FA variation in milk. Evidences from quantitative and molecular studies suggest a potential future animal selection, but some question about the kind of selection mechanism and the economic incentive for the improvement should be preliminarily answered
Effect of heat stress on animal production and welfare: the case of dairy cow
No full textHeat stress affects directly and indirectly metabolic and, physiological acclimation which may reduce the synthesis of milk and makes dairy cows more susceptible to illness. In the present review, after a brief description of heat stress effects on the dairy cow metabolism, nutritional, management and genetic strategies able to tackle heat stress effects were evaluated. As regard the nutrition strategies, die main rule to prevent negative effect of heat stress is to increase the energy and protein density of the diet and to maintain a high efficiency of the rumen activity. In order to mitigate the heat stress two management strategies may be applied: 1) cooling the barn and, in general, the environment of the herd; 2) cooling directly the animals. Finally, recent studies showed that in dairy cattle the heat tolerance genetic component was not negligible, suggesting that heat tolerance selection should be included in the selection objectives
Effect of two types of tannins on the biohydrogenation steps of polyunsaturated fatty acids in the rumen: an in vitro study.
No full textStudy on the effect of two different type of tannins on the biohydrogenation of polyunsaturated fatty acids in the rumen by means of an in vitro fermentatio
Lipid supplementation in small ruminant nutrition and dairy products quality: implications for human nutrition
No full textThis review deals with: i) the effects of dietary lipid supplementation on milk fatty acid composition in small ruminants, taking into consideration also the different responses observed among ruminant species, and ii) the implications of milk fat modification on human health. In the last years, an increasing number of studies have focused on lipid supplementation in dairy goats and ewes. Some studies have focused on vegetable lipid sources (i.e. linseed, sunflower, rapeseed, soybean, olive), either as whole seed (raw and processed) or as oil (protected and unprotected), whereas few of them have dealt with the effects of marine oil in combination with vegetable fat on milk composition in small ruminants. Responses to lipid supplementation can vary significantly among ruminant species, as a consequence of differences in eating behaviour, rumination, buffering of rumen pH, rumen digestion kinetics and rumen passage rate. Recently, the metabolic mechanisms regulating milk fat synthesis have been studied across ruminant species, by using the milk fat depression model. At present, effective nutritional strategies based on dietary lipid supplementation of small ruminants are available, to obtain dairy products enriched in conjugated linoleic acid (CLA), vaccenic acid (VA) and alpha-linolenic acid (LNA) Specific clinical studies are needed to provide the scientific evidences that enriched dairy products may be beneficial to human health
Is a hydrolysable tannin extracted from chestnut wood efficacious against necrotic enteritis?
Full text linkA hydrolysable tannin extracted from chestnut
(SaviotaN®) was tested for efficacy in controlling
the proliferation of Clostridium perfringens in the
gut of broiler chickens challenged via oral gavage
first with coccidia (Eimeria tenella, Eimeria
acervulina, Eimeria maxima) at the age of 10
days, and then with Clostridium perfringens at
the age of 15 days. We randomly allocated 150
broiler chickens within 5 poultry isolators (30
birds each). Dietary treatments consisted of a
basal diet (C) composed of corn [575 g/kg on dry
matter (DM)] and soybean meal (100 g/kg DM),
barley bran (220 g/kg DM), corn gluten feed (30
g/kg DM), soybean oil (25 g/kg DM), vitamin
mineral premix (49.5 g/kg DM), and four other
diets obtained by adding chestnut tannin extract
(1.5, 3, 5, and 12 g/kg during week 1, 10.0 g/kg
during week 2, and 8.0 g/kg during the last two
weeks, respectively) to C. At the age of 20 days,
15 birds/group were euthanised and individually
examined for the level of gut infection by counting
Clostridium perfringens and macroscopic gut
lesions. Results demonstrated that chestnut tannin
gave significant results even at low concentration
levels in the feed (1.5 to 3.0 g/kg), but was
actually efficient in controlling necrotic enteritis
at levels ≥5.0 g/kg. The treatment (12.0 g/kg during
the first week and 8.0 g/kg during the last two
weeks of age) resulted very efficient in controlling
the proliferation of Clostridium perfringens
and in reducing the severity of gut damage compared
to the untreated infected group
Neutral Detergent Fibre (NDF) and Non Structural Carbohydrate (NSC) requirements in the nutrition of dairy ewes
No full textThe aim of this review was to contribute to the knowledge of neutral detergent fibre (NDF) and non structural carbohydrate
(NSC) requirements in the nutrition of dairy ewes. NDF and NSC requirements were evaluated by analysing a
dataset that involved 30 experimental trials carried out from 1985 to 2003. The dataset included chemical composition
of the experimental diets, individual milk yield, body weight, milk protein and fat content. These selected papers regard
10 different dairy ewe breeds (Valle del Belice, Bergamasca, Comisana, Delle Langhe, Massese, Sarda, Chios,
Manchega, Lacaune and Friesian) and lactating ewes in mid lactation, kept under non homogeneous environmental and
feeding conditions. Results substantially confirmed that which was recently reported in literature: NDF requirements are
higher in late lactation than during early lactation and they vary between 33-38% on DM, while NSC requirements are
higher during early lactation than in late lactation when the energy from NSC promotes an increase in fat deposits
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