410 Journal of Agriculture, Victoria. [10 July, 1916. 



Carbohydrate. 



The term carbohydrate is given to a large group of compounds 

 chemically related. They are composed of the elements carbon, hydrogen, 

 and oxygen, and to this class belong sugars, starches, gums, cellulose, 

 &c. In the animal body, carbohydrates are used for the production of 

 energy and heat, and any excess is converted into body fat. 



Unlike protein, any excess of carbohydrates over immediate require- 

 ments is not passed off unused, but is stored as a reserve in the form 

 of fat. 



Carbohydrates cannot replace protein, altliough protein may replace 

 carbohydrate, but only at s. high cost. 



In the analysis of cattle foods, tlie term carbohydrate is given to 

 the combined amounts of nitrogen free extract and crude fibre, and, 

 although the estimation is not purely carbohydrate, no appreciable error 

 is made by giving it an average carbohydrate value. 



Fat. 



Crude fat, or ether extract, although some of the members of this group 

 consist of the same elements C.H.O. as the carbohydrate, they differ 

 chemically. The ether extract sometimes includes, besides fat or 

 oils, wax, chlorophyll, which are Avithout feeding value, conse- 

 quently, the food value of the ether extract is dependent upon its 

 source. That obtained from oil cakes, grains, and their offals, give a 

 higher value than that obtained from hays or green fodders. The 

 digestible portion of the ether extract serves the same function as the 

 carbohydrate, but its capacity for heat production is much greater, pure 

 fat having two and a half times the value of carbohydrate. The crude 

 fat or ether extract of oil cakes, grain, bran, &c., possesses a capacity 

 for heat production two and two-fifths times greater than carbohydrate, 

 whereas the fat estimation of hays and green fodders is only about twice 

 the value of carbohydrate. 



Nutritive Ratio. 



The nutritive ratio, or N.R., of any food means the ratio of the 

 protein content to the carbohydrate and ether extract combined ; the 

 ether extract is reduced to its starch equivalent. The nutritive ratio 

 of any food, or combination of foods, is a most important factor m 

 determining its efficiency. 



Milking cows yielding up to 3J gallons daily are most economically 

 fed on a ratio with a N.R. of 1 to 6 or 7, which is the ratio of good 

 mixed pasture grass ; but for heavy milkers yielding 4 gallons and over, 

 the ratio may be effectively reduced to 1 to 5, which means that for eacli 

 part of digestible protein, there are 6, 7, or 5 parts of carbohydrate 

 respectively. 



In practice, the N.R. of any ration is valuable when purchased foods 

 are used, because it shows in what proportions the constituents should be 

 combined to produce the best return. Both money and feed may be 

 wasted by disregarding its value. When the N.R. is too wide, the food 

 is deficient in protein, and consequently not sufficient protein is ingested 

 to meet the needs of the animal, whilst at the same time the digestibilit 



