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The goat nutrition standards are variable. The German standard for lactating goats is different from other international standards. For example the metabolizable energy (ME) requirement, according to German standard (DLG, 1997) is 8 MJ ME/kg of 4% fat corrected milk (FCM), whereas according to AFRC (1998), INRA (1988) and NRC (1981) the corresponding requirements are 4.5-5.2; 4.6-5.4 and 5.2 MJ ME/kg milk respectively.
Conflicting observations also exist about the influence of protected soya-meal as a source of rumen undegradable protein (UDP) on lactation performance of goats. The aim of the experiment was to determine the effect of high and low energy level of feeding with or without protected protein on the lactation performance of German Fawn goat.
Twenty four German Fawn goats either from l" (43.37±3.937 kg and 2 year old) or 3" 62.64±6.783 kg and 4-5 year old) parity were used for the trial. Feeding levels were 7.2 (I) and 5.2 (II) MJ ME/litre of milk of 3.5% fat in addition to that of the maintenance allowance.
At each feeding level, diet had either unprotected (U) or formaldehyde protected (P) soya-meal. Thus, four diets were IU, IP, IIU and IIP, having six animals in each.
The diets were composed of hay and pellet (10:4:1 of beet pulp : barley : soya-meal).
Effect of feeding level, protein protection,parity, health status and kid number on intake, milk yield, milk composition, growth rate of goats were recorded across the 21 weeks of study. High feeding level resulted increase (P<0.001) in estimated metabolizable energy (ME) and metabolizable protein (MP) availability. Dietary inclusion of protected soya-meal increased (P<0.001) the estimated MP but not the ME availability. Animals in 18t parity ate more (P<0.001) DM (111 vs. 102 g/kg W 0.75/d) than those in 3m parity.
Animals with twine kids (110 g/kg W°"75/d) had higher (P<0.001) DM intake than those with single kid (102 g/kg W°"75/d).
Fat (4%) corrected milk (FCM) yield was not effected by high (1924 g/d) or low (1927 g/d) feeding level but increased (P<0.001) with protected (2166 g/d) than with unprotected (1703 g/d) soya-meal. FCM yield for four dietary combinations were 1806, 2078, 1600 and 2254 g/d for diets IU, IP, IIU and HP espectively. For unit increase (g) in estimated MP availability relative to ME (MJ) intake, FCM yield increased 1418(±275.6) g daily (r2 = 0.58; P <0.001). Milk fat (3.14 vs. 3.54%; P<0.001) and protein (2.94 vs. 3.04% P<0.05) contents were lower at high than the low feeding level. Protected protein increased (P<0.001) the fat, laktose and net energy (NE) content of milk. Milk urea concentration of 175, 183, 192 and 204 mg/l for diets IU, IP, IIU and UP respectively indicated lower RDP content of these diets. The RDP contents were 6.97, 6.70, 7.30 and 6.83 g/MJ of ME for diets IU, IP, IIU and HP respectively. Live weight change over the experimental period were 41, 6, 17 and 19 g/d. Absence of any positive response of high feeding was probably due to inefficient rumen fermentation resulting from inadequate RDP supply.
Protected protein improves production performance apparently by increasing MP:ME ratio in the absorbed nutrient.