ABSTRACT
During the transition period in dairy cows, drastic adaptations within and between key tissues and cell types occur in a coordinated manner to support late gestation, the synthesis of large quantities of milk and metabolic homoeostasis. The start of lactation coincides with an increase of triacylglycerols in the liver, which has been associated with several economically important diseases in dairy cows (i.e. hepatic lipidiosis, mastitis). The polyunsaturated fatty acids have been used to improve liver metabolism and immune function in the mammary gland. Therefore, the effects of dietary linseed supplementation on milk quality and liver, adipose and mammary gland metabolism of periparturient dairy cows were studied in 14 cows that were randomly assigned to control or linseed supplementation. Animals were treated from 3 weeks antepartum until 6 weeks post-partum. Linseed did not modify dry matter intake, but increased milk yield and lactose yield, and decreased milk fat concentration, which coincided with lower proportion of C16 and higher proportions of stearic acid, conjugated linoleic acid and α-linolenic acid in milk fat. Linseed supplementation did not significantly change the expression of key lipid metabolism genes in liver and adipose tissues, except of glucose transporter 2 (GLUT2) in liver, which was increased in cows supplemented with linseed, suggesting that more glucose was secreted and probably available for lactose synthesis compared with cows fed control diet. Large adaptations of transcription occurred in the mammary gland when dairy cows were supplemented with linseed. The main affected functional modules were related to energy metabolism, cell proliferation and remodelling, as well as the immune system response.
Subject(s)
Adipose Tissue/metabolism , Animal Feed/analysis , Cattle , Fatty Acids/pharmacology , Flax/chemistry , Liver/metabolism , Adipose Tissue/drug effects , Animal Nutritional Physiological Phenomena , Animals , Dairying , Diet/veterinary , Fatty Acids/administration & dosage , Fatty Acids/chemistry , Female , Gene Expression Regulation/drug effects , Liver/drug effects , Mammary Glands, Animal/drug effects , Mammary Glands, Animal/metabolism , Oligonucleotide Array Sequence Analysis , Peripartum Period , Pregnancy , RNA/genetics , Real-Time Polymerase Chain ReactionABSTRACT
Digestion coefficients of nutrients give information about the amount of nutrients available to the animal but not about the rate or site of absorption. Gradual digestion of starch may have an amino acid sparing effect and therefore enhance growth efficiency of broiler chickens. A growth trial was performed with 6,800 broiler chickens from 9 to 30 d of age to investigate interactions between starch digestion rate and amino acid level. Birds were fed either a pea-corn-based diet (slowly digestible starch) or a tapioca-corn-based diet (rapidly digestible starch). Both diets were formulated with five levels of digestible lysine, varying from 8.5 to 11.0 g/kg. The minimal levels of other amino acids varied accordingly. Starch source did not affect feed intake (2,213 g), but weight gain was consistently higher for birds on pea-corn diets than for those on tapioca-corn diets (1,426 vs. 1,400 g; P < 0.01). Feed conversion was better (P < 0.01) for birds on pea-corn diets (1.55) than for birds on tapioca-corn diets (1.58). The difference in feed conversion between birds on pea-corn and tapioca-corn diets was greater with lower amino acid levels (0.043) than with higher amino acid levels (0.019) in the diet (P = 0.11). This interaction was more pronounced during the first 9 d of the experiment (P < 0.05). It was concluded that feeding slowly digestible starch improved protein and energy utilization in broiler chickens.
Subject(s)
Amino Acids/administration & dosage , Chickens/metabolism , Diet , Digestion , Starch/metabolism , Animal Nutritional Physiological Phenomena , Animals , Dietary Proteins/administration & dosage , Dietary Proteins/metabolism , Eating , Energy Metabolism , Female , Kinetics , Lysine/administration & dosage , Male , Manihot , Pisum sativum , Time Factors , Weight Gain , Zea maysABSTRACT
Dietary starch is the major energy source for broiler chickens, and knowledge about its digestive behavior can be important. In a digestibility trial with 720 broiler chickens, site, rate and extent of starch digestion were measured for 12 feedstuffs. Starch digestion was determined using the slaughter technique, which involves removal of the small intestine from the recently killed chicken, with manual collection of the contents. Starch digestion coefficients were calculated from remaining starch in three segments of the small intestine and in excreta. Mean retention time in four segments of the small intestine was measured. This enabled calculations for starch digestion rate (k(d)). Ileal starch digestibility varied from 33% (potato starch) to 99% (tapioca). Retention time for digesta in the postduodenal small intestine varied from 136 min (barley diet) to 182 min (potato diet). On the basis of starch digestion rates, a distinction was made between slowly digestible starch (k(d) < 1 h(-1)), gradually digestible starch (k(d):1-2 h(-1)) and rapidly digestible starch (k(d) > 2 h(-1)). Starch from common beans was digested most slowly (k(d): 0.5 h(-1)), and starch from tapioca was digested most rapidly (k(d): 4.3 h(-1)). Starch digestion rates of potato starch and legume seeds were lower than those of cereal grains and tapioca. Degradation of starch entering the hind gut of the birds did not occur. Milling of corn affected rate, but not the extent of starch digestion. We concluded that site of starch digestion within the small intestine is not an accurate indicator for starch digestion rate.
Subject(s)
Animal Feed , Chickens/metabolism , Digestion , Intestine, Small/metabolism , Starch/metabolism , Absorption , Animals , Glucose/metabolism , Time FactorsABSTRACT
Current feed evaluation systems for poultry are based on digested components (fat, protein and nitrogen-free extracts). Digestible starch is the most important energy source in broiler chicken feeds and is part of the nitrogen-free extract fraction. Digestible starch may be predicted using an in vitro method that mimics digestive processes in the gastrointestinal tract of broiler chickens. An experiment was designed to use this method for predicting site, rate and extent of starch digestion in broiler chickens. In vitro starch digestion was studied in 12 experimental diets differing in starch sources. These diets were also used in a digestibility trial with broiler chickens. Correlations between in vitro and in vivo starch digestion were calculated. Starch digestion after 2 h incubation correlated well with in vivo starch digestion in the first half of the small intestine (r = 0.94). A 4-h incubation period resulted in a good correlation between in vitro starch digestion and ileal starch digestion (r = 0.96). In vitro starch digestion rate (h(-1)) correlated well with in vivo starch digestion rate (r = 0.87). In vitro starch digestion of individual starch sources was additive. It appeared that legume seeds and waxy corn contained two starch fractions, which were digested at different rates. We conclude that starch digestion rate in broiler chickens is well predicted by the in vitro method.
