By Dr.Mukesh Sharma
Dairy Consultant.
Now a days the dairy entrepreneurs of India are more concerned about the balance ration with the application of scientific line with latest technology.The dairy farmers are well aware of the importance of rumen protected protein and protected fat in milk production and reproduction. However, these two plays important role in post-partum only but the protected choline is very much important during peri-partum period. As choline do so many metabolic activities like lipid transport and utilization within the cells. High-producing dairy cows experience negative nutrient balance during late gestation and early lactation that induces excessive tissue mobilization, primarily of fat but also of protein, leading to subclinical and clinical ketosis and fatty liver . About 50 to 60% of transition cows experience moderate to severe fatty liver . This fatty liver condition is a classical deficiency symptom for choline in dairy animals and also in chicken. Hence, there will be choline deficiency in transition cows a period which extends between three weeks pre and post-calving . Choline is a vitamin-like compound whose metabolism interacts very closely with methionine and vitamin B12 metabolism .
WHAT IS CHOLIN———-
Choline [(CH3)3N+CH2CH2OH], also known as trimethyl ethanolamine, is an essential component of mammalian diets as it is required for normal function of cells. It was discovered by Andreas Strecker in 1862, but it remained unrecognized as an essential nutrient for humans until 1998, when dietary reference intakes were established. Choline was initially determined to be essential in the prevention of fatty liver in rats and dogs (Best and Huntsman, 1932). Choline is key compound for the synthesis of 2 important molecules, phosphatidylcholine and acetylcholine Phosphatidylcholine is the main phospholipid in ruminants and it is critical for lipid absorption and transport, cell membrane structure, cell signaling, and synthesis of lipoproteins.
The second compound synthesized from choline, acetylcholine, is a neurotransmitter in the central and peripheral nervous system and critical in the neuromuscular junctions for muscle contractions.
Because choline is a critical component for synthesis of phospholipids and neurotransmitters, it supports structural integrity and signaling roles in cell membranes, influences cholinergic neurotransmission and cognition, and it is a major source for methyl-groups via betaine for methylation pathways
By strict definition, choline is not a vitamin; however, it is an essential nutrient. Despite the fact that most animals synthesize choline, it must be consumed in the diet because de novo synthesis is inadequate to maintain health. Choline is mainly found as a component of specialized fat molecules known as phospholipids, the most common of which is called phosphatidylcholine or lecithin.
Choline is required for the synthesis of phospholipids which are essential components of all membranes and is an important source of labile methyl groups. Choline deficiency in nonruminants is not common except under the most severe circumstances because choline is widely distributed in plant and animal tissues. However, choline deficiency induced experimentally is manifested as fatty liver, hemorrhaging kidneys, elevated blood pressure, and impaired neurological function. In nonruminants, choline deficiency can be avoided by supplying dietary sources of other methyl donors, such as betaine, methionine, and folic acid, in conjunction with adequate vitamin B-12 .One of the earliest signs of choline deficiency in nonruminants is a reduction in lipoprotein assembly and secretion of triglycerides from liver to plasma. Addition of other methyl donors such as methionine serves to prevent the accumulation of liver lipid in rats, perhaps as substrates for choline synthesis. Currently, there is considerable interest in use of choline and related compounds to reduce fatty liver associated with the onset of calving in transition dairy cattle.
Role of Choline——————
In the body choline plays numerous functions, however, the six main functions of choline are: 1. Cellular integrity – as a component of cell plasma membrane it is essential for the maintenance of cellular integrity.
2. Cell signalling – the metabolic products of phosphatidyl choline like phosphatic acid, platelet activating factor, etc. responsible for wound healing and reproduction.
3. Osmoregulation – plays an important role in cell water metabolism through betaine, as it reduces the muscle drip loss.
4. Lipid transport and metabolism – Lecithin a component of bile, reduces the surface tension and improves fat assimilation.
5. Methyl donor – the oxidation product of choline – betaine is a potent methyl donor for synthesis of biomolecules like plasma membrane, RNA, DNA, carnitine, creatinine, etc.
6. Neurotransmitter – as a component of acetyl choline, it involved in nerve impulse transmission.
Even though choline is considered as a B vitamin is endogenously synthesized by sequential methylation process. The dietary choline, betaine, methionine, folic acid, Vitamin B12 all contribute to the body choline content. In adult dairy animals, choline is extensively degraded in the rumen; dietary choline therefore contributes insignificantly to the choline body storage. The various protein (protected or unprotected) sources are rich sources of choline but due to rumen degradability (85-95%) the animal will depend on its endogenous choline synthesis for their metabolic needs. Hence, there is need for use of protected choline in the diet of dairy animals for better health and productivity.
Microencapsulation is used to protect a substance from degradation in the rumen. Commercially available microencapsulated products contains about 28–50% choline chloride, out of which about 85% its choline rumen undegradable. These products can be added directly to the compound feed or administered as a top dress.
Protected choline supplementation will reduces the fatty liver condition in transition cows because, higher fat content in the liver is associated with poor reproductive performance . Feeding of protected choline will improve the milk production in newly calved animals . Feeding protected choline increased the milk yield, milk fat percentage, milk protein content in animals fed with protected fat than feeding protected fat alone. Feeding choline in this form not only meeting the requirement of choline it also reduces the requirement of methionine and lysine as these two amino acids involved in the endogenous synthesis of choline. Hence, obtaining choline from individual supplement is more economically beneficial than through feed ingredients or endogenous synthesis.
When Should Rumen-Protected Choline Be Fed?————
In addition to its role as a methyl donor for choline synthesis, methionine may play a direct role in lipoprotein metabolism. The L-methionine added to milk fed to calves stimulates VLDL synthesis , and feeding the hydroxy analog form of methionine increases circulating lipoproteins and milk fat percentage in lactating dairy cattle. Furthermore, methionine and lysine infusions in lactating dairy cows reduced plasma ketones during the second week of lactation . Providing choline may act to spare methionine catabolism in transition cows. Dietary choline must be protected from rumen degradation to be effective. The supply of methionine from the diet, or rumen bacterial synthesis, folic acid status, vitamin B-12 status, and potential for fatty liver developments all play a role in determining the effectiveness of choline supplementation in the transition cow.
Effects of Rumen-Protected Choline in Transition Cows————–
Rumen-protected choline is beneficial for transition cows fed 10% rumen degradable protein (RDP) and 4.0% rumen undegradable protein (RUP) (% of dietary DM), but it decreased milk production in cows fed 10% RDP and 6.2% RUP during the prepartum period . Liver fatty acid oxidation is not altered by rumen-protected choline, although liver triglycerides may be reduced with rumen-protected choline in some instances . The latter suggests an increase in triglyceride export to reduce fatty liver in transition cows fed rumen-protected choline.
Rumen-protected choline holds promise for modulating metabolism in transition cows to reduce incidence and severity of fatty liver at calving . The milk production response to rumen-protected choline is 5 to 7 lb day during the first 56 to 60 days of lactation. The frequency of a significant positive milk production response to rumen-protected choline is observed in 50% of the studies conducted. Metabolic responses to rumen-protected choline have been equivocal. A predictable response to rumen-protected choline feeding may depend on the basal diet, supply of other B vitamins and related factors, and other management factors, including the body condition score of cows entering the transition period.
Impact of choline on digestibility—
Choline supplements increase to produce volatile fatty acid (VFA) acetate and rumen pH tends to increase digestibility coefficient of nutrients in rumen.
Impact of choline on milk yield——-
In an animal production system, the quantity and quality of milk production are the most important traits. Supplementation of RPC increases the milk production for the following reasons, viz., higher digestibility and increased total VFA concentration, decreased NH3 -N, and prevention of metabolic disorders such as ketosis and fatty liver syndrome.
During the transition period, RPC supplemented cows change plasma NEFA concentration, increase hepatic fat export, and this may effect decrease the risk for metabolic disorders and increase milk and milk composition.
Choline increase productive performance and prevents the metabolic disorders with better nutrient digestibility, increases milk yield and milk fat percentage. It also increases reproductive efficiency in dairy cows. Choline especially during transition cows @ 10 to 20 g per animal per day as protected form will be helpful for better health and performance.
Reference: On request.
