Studies on goat nutrition Part II. Digestible protein requirements for maintenance from balance studies

Abstract

With One Text-figure)In Part I of this series (Majumdar, 1960) the results of a study of the endogenous urinary nitrogen (EUN) and metabolic faecal nitrogen (MFN) excretions in goats were recorded. These determinations were undertaken with a view to assessing the minimum protein requirement for maintenance in that species. Using the EUN values as the basis of calculation the minimum protein requirement was determined to be 0-65 lb./lOOO lb. live weight (L.W.). Maynard (1951), while agreeing that the endogenous nitrogen provides the basic value for arriving at the maintenance needs for protein, states that the values based on EUN are in practice much lower than those determined from balance studies. He was further of the opinion that 'the balance method provides an exact measure of the actual requirements, in terms of a specific ration, by determining the minimum intake that will provide maximum retention'. In the present paper the results of such N-balance studies are presented. EXPERIMENTALSix adult healthy goats of the Jumna-pari breed were put on trial. These animals were used successively in four metabolism trials. They were fed rape cake as the sole concentrate and wheat bhoosa (chaffed wheat straw) as the sole roughage. Calcium as the carbonate and phosphorus as disodium hydrogen phosphate (Na 2 HPO 4 ) were fed, when necessary, to keep the animals in nutritional balance with respect to these minerals. The protein intake was varied to bring the retention of N from an initial negative level to a positive one. RESULTS AND DISCUSSIONIn Table 1 are recorded the results of three balance trials. In trial no. 1, while the calcium and phosphorus balances were positive, the N balance was negative. In trials nos. 1A and B, the balances of all three nutrients were positive. A preliminary metabolism trial was conducted, but since it showed negative balances for all three nutrients the data are not included here.It will be seen from Table 1 that when the average N intake was 0-32 g./kg. L.W. the animals were in negative balance, the average balance being -0-07 g./kg. L.W. When, however, the average N intake per kg. of L.w. was raised to 0-51 g. the animals all went into positive balance. Evidently, the N requirement per kg. in the adult goat lies between these two values of N intake.The balance data presented in Table 1 were then subjected to three different treatments, viz.(1) graphical, (2) statistical and (3) the percentage utilization technique, as described by Steggerda & Mitchell (1941) and by Outhouse et al. (1941). By this means N requirement was calculated.Graphical method. Table 2 records the N data presented in Table 1 calculated in mg. per kg. L.W. Reference to this table shows that, taking the positive balance data of trials nos. 1A and B on the one hand, and the negative balances of trial No. 1 on the other, there are five animals for which complete sets of positive and negative balance data were available. If, now, the intakes and balances for each animal are plotted graphically with the ordinate represen...

Nitrogen metabolism in indigenous Malawi goats

“…(1978), working with adult castrated native Japanese goats, estimated a daily loss of 0-24 g N/kg W 1 ' 5 , while Akinsoyinu, Mba & Olubayo (1976) obtained for West African Dwarf goats the low value of 0-04 g/kg W 076 . Majumdar (1960a) found with Jamnapari goats that EUN losses were 0-052 g/kg live weight, which can be converted to 0-13 g/kg W 0 " 76 , close to the value obtained from the present experiment (0-12 g/kg W 075 ) for animals of a rather lower mean live weight, and similar to the accepted values for sheep and cattle. The value for West African Dwarf goats is surprisingly low and must be treated with some caution until corroborative evidence is available, as it suggests that these animals have an exceptionally efficient metabolism with a minimal loss of nitrogen from the degradation and replacement of protein structures and.…”

“…The present experiment has estimated maintenance levels to be 0-314 g digestible N/kg W 07S , or 0-688 g dietary N/kg W 0 7 6 both by extrapolation methods, and 0-682 g dietary N/kgW°-76 by a factorial method, close to the values obtained by Itoh et al (1978), and Majumdar (1960a and b).…”

“…intake (Agricultural Research Council, 1965). Majumdar (1960a) determined MFN for goats, offering a ration containing 0-18% N with a reported true digestibility for N of 100%, obtaining faecal losses of 4-00 g N/kg D.M. intake.…”

“…The maintenance requirement for nitrogen was stated by Itoh et al (1978) to be 0-339 g digestible N/kg W 0 ' 75 , obtained when urinary N output was equal to digestible N intake in the equation UN = 0-2367 exp (1-214 ADN), where UN = urinary N output (g/kg W°' 7S ), and ADN = apparent digestible N intake (g/kg W 0 7 6 ). Majumdar (1960a), calculating maintenance levels from EUN values, estimated a requirement of 0-10 g digestible N/kg live weight, but also arrived at a figure of 0-18 g digestible N/kg live weight by a factorial method (Majumdar 19606). A factorial method has also been used by Akinsoyinu et al (1976), indicating a maintenance requirement of 0-09 g digestible N/kg W°™, rather lower than the value of 0-14g N/kg W 0 " 75 obtained in the same paper by a regression of N balance on N intake.…”

Nitrogen utilization of growing-finishing Barbados Blackbelly lambs

“…In the present trials the digestible nitrogen required for nitrogen equilibrium by 21 kg Barbados Blackbally sheep was calculated from nitrogen balance, factorially and from feeding trial data and found to vary from 4-26 to 6-94 g/day depending on the method of estimation. These values are much higher than those referred to above but agree more closely with those reported by Majundar (1960) for goats. It is difficult to explain the above differences.…”