The apparent digestibility of crude protein by the ruminant: II. The general equation and some of its implications

Abstract

The general equation, y = 70 log x − 15, connecting y, the digestibility coefficient, to x, the percentage of crude protein in the dry matter of the feed of ruminants, which was proposed in an earlier paper, has been shown to fit all the directly determined world data for cattle, sheep and goats which have been published by Schneider (1947). It is applicable to rations composed of both single and mixed feeds for it is the total percentage of crude protein in the ration which determines its digestibility.The equation is of general application, irrespective of climate or feed, and for the first time a link is provided between the large bulk of data from temperate regions and those hitherto neglected and apparently aberrant data from the tropics and subtropics.The equation adequately explains a large part of the variability of results obtained by the ‘by difference’ method. In particular, attention is drawn to its value in explaining ‘associative effects’ in mixed feeds.It would seem to have several practical applications; one being the ready determination of the average digestibility of crude protein in rapidly growing grasses and herbages at different stages of development; another being the evaluation of average crude protein digestibility of single or compound feeds in those parts of the world where adequate facilities for digestibility studies are not available. It can also be used in computing maintenance and production rations for meat and milk.

Licuri oil supplements for lactating cows on pasture

“…Assurance levels (per kilogram of product): calcium, 200.00 g; phosphorus, 60.00 g; magnesium, 20.00 g; sulfur, 20.00 g; sodium, 70.00 g; potassium, 35.00 g; copper, 700.00 mg; iodine, 40.00 mg; cobalt, 15.00 mg; iron, 700.00 mg; manganese, 1600.00 mg; zinc, 2500.00 mg; selenium, 19.00 mg; chromium, 10.00 mg; fluorine (max), 600.00 mg; vitamin A, 200 000.00 international units (IU); vitamin E, 1500.00 IU; vitamin D3, 50 000.00 IU. The DM and nutrient digestibility coefficients were calculated according to the equation by French et al (1957): digestibility coefficient 0(kg nutrient intake(kg nutrient excreted)= (kg nutrient intake))100:…”

The natural regulation of buffalo populations in East Africa: The food supply as a regulating factor, and competition*

“…As a result, by the end of the dry season, a random sample of animals of all ages and sexes showed that their diet contained only 2.18% crude protein. French, Glover & Duthie (1957) and Glover & Duthie (1958) have shown that the digestibility of crude protein is remarkably similar for ruminants in general and even for non-ruminants. Furthermore, from digestibility trials, P. Arman (personal communication) found that buffalo were very similar to cattle.…”

“…Bredon,Harker & Marshall (1 963) found that the degree of digestibility of dry grass-the digestibility coefficient (DC)-was related to the % crude protein (CP) in the diet of cattle by DC = 100.89 log CP -44.45 and this gives zero digestibility at 2.76% crude protein. But protein and energy assimilation remain low even above this level due to the inhibition of the rumen micro-organisms untiI a higher quality at intake is attained: the minimum level of crude protein for maintenance in tropical cattle has been estimated to lie between 4% and 8% with most measurements approaching 5% (French, 1957;Plowes, 1957;French et al, 1957;Bredon & Wilson, 1963;Agricultural Research Council, 1965;Milford & Minson, 1966). The value of 5% crude protein has been used in Fig. I to indicate the minimum maintenance level.…”

“…These particles must reach a small enough size before continuing through the gut. The lower the protein value of the food, the higher the fibre content (Glover, Duthie & French, 1957) and the longer is the time needed to reduce the food by mastication to the risht size. This was confirmed by empirical observations of cattle (Hancock.…”