Effect of feeding undegradable protein with energy on nutrient utilization, milk yield and milk composition of crossbred goats

Twenty lactating cross-bred goats (Sannen × Beetal and Alpine × Beetal) were assigned to four treatments of five animals each in a 2 × 2 factorial design on the basis of body weight (31.5 ± 1.97), days of post-partum (21.5 ± 1.83) and average daily milk yield (1.3 kg ± 0.21). Two types of concentrate mixture (CM-I and CM-II) being isonitrogenous (20.6% CP) and isocaloric (73.2% TDN) nature were fed to treatments: 1 (LUP) & 2 (LUPM) and 3 (HUP) & 4 (HUPM), respectively. The two concentrate mixture was similar in composition with only difference in RDP:UDP ratio (CM-I, 72:28; CM-II, 58:42) due to replacement of untreated mustard cake (25%) as in CM-I, by formaldehyde treated mustard cake in CM-II, as undegradable protein. Molasses as energy source was additionally supplemented at the rate of 8% of concentrate mixture on DM basis to animals in LUPM and HUPM. The animals were fed concentrate and roughage (Berseem:wheat straw = 2:1) in 50:50 ratio. In a 120 days feeding trial a metabolism trial was conducted at the end of trial which revealed higher DM intake in molasses supplemented animals due to better palatability of concentrate mixture. Feeding higher UDP content in diet had no significant effect on DM intake. The CP and TDN intake in different groups was also not affected due to similar intake and digestibility of nutrients. The digestibility and nutritive value of all the four diets were similar except CP% which was decreased due to energy supplementation in animals of LUPM and HUPM. Energy supplementation irrespective of feeding undegradable protein decreased (P < 0.01) the urea concentration in milk. The average milk yield and 4% FCM yield were not influenced either by higher undegradable protein or additional energy supplementation. Milk composition was also not influenced by feeding undegradable protein regardless supplementation of molasses. However, lower concentration (mg/100 ml) of milk urea in higher undegradable protein and energy fed animals reflects better protein and energy utilization. It was concluded that increasing UDP level in diet from 28 to 42% in concentrate mixture through formaldehyde treatment of mustard cake is not beneficial in augmenting milk production and composition. Additional supplementation of molasses with or without undegradable protein had no added advantage in increasing milk production and improving milk composition.