Abstract
Four experiments were conducted from January, 2000 to June, 2003 to examine the effect of urea molasses block (UMB) supplement on feed intake, milk yield, body weight (bwt.) changes of cows and calves, seasonal effects, reproductive performance and economic benefit on straw based diet cattle. Holstein crossbred -HC (local zebu x Holstein) cows were used to determine optimum level of UMB in experiment (expt.) 1 and 2 under organized farm and smallholder farm condition respectively. In expt. 3, seasonal variation on production and in expt. 4, genotypic variations on reproductive performance of HC and Sahiwal crossbred -SC (local zebu x Sahiwal) cows were investigated under smallholder farm condition. Feed supplied for all expts.were: adlibitum rice straw, limited green grass (av.1.17 kg/100 kg bwt.) in expt. 1, 2 & 4. In expt.3; straw and grass were supplied at the ratio of 4:1 in dry and 3:1 in rainy season. Concentrate was supplied on the basis of milk production (1 kg concentrate for 2 kg milk). Clean drinking water was supplied adlibitum. Cows were >2nd lactation, housed in stanchion barn, stall-feeding and used for dairy purpose.
In expt. 1, total 32 HC cows were given 4 levels of UMB containing 0 (To), 300 (T1), 500 (T2) and 700 (T3) g/d at BAU Dairy farm. Milk yield increased linearly with increasing intake of UMB. Weight gain of cows and weight gain of calves were highest at T2 level (25 g/d and 194 g/d respectively), but the difference between T2 and T3 (20 g/d and 166 g/d respectively) was insignificant (p>0.05). Reproductive intervals viz. calving to 1st progesterone (P4) rise, 1st estrus, conception and CI were also reduced (p>0.05). The T2 level was best among 4 treatments.
In expt. 2, UMB were given to 108 HC cows at the rate of 0 (To), 350 (T1), 500 (T2) and 650 (T3) g/d under smallholder farm condition. Feed intake, milk yield, bwt. gain of cows and growth rate calves increased linearly with the increasing levels of UMB. The difference of milk yield between T2 (5.95 kg/d) and T3 (5.99 kg/d) was insignificant (p>0.05). Milk fat increased linearly with the increasing levels of UMB, but it was same in T2 and T3 (47.1 g/kg). Reproductive intervals were decreased with the increasing levels of UMB and insignificant (p>0.05) difference between T2 and T3 for all parameters were found. Feeding of UMB at T2 level earn the highest profit in expt. 1 (Tk. 21.23/d) and expt. 2 (Tk.38.44/d).
Expt. 3 was conducted in 2 seasons, namely rainy (May to October) and dry (November to April) seasons. Sixty HC cows were assigned to a 2 x 2 factorial experiment in CRBD. UMB increases nutrients intake in both seasons. UMB increases milk yield by 1.54 and 0.73 kg/d, bodyweight gain of cows were 117 and 28 g/d, calves 60 and 41 g/d and earn Tk. 29.22/d and 12.24/d in dry season and rainy season respectively. Reproductive intervals were reduced in both seasons and shorter in dry season.
In expt. 4, Forty HC and 40 SC cows were assigned as expt. 3. Feed intake was increased in both genotypes. Supplementation resulted reduction of reproductive intervals viz. calving to 1st P4 rise, 1st estrus, conception and CI by 14, 21, 54, 54 in HC and 39, 46, 81 and 80 days in SC cows respectively. SC supplemented cows had shorter reproductive intervals comparable to HC cows. It may be concluded that (a) addition of 500 g/d UMB with straw based diet under organized and smallholder farm conditions is optimum. (b) UMB supplement is more effective during the scarcity of green fodder in dry season (c) SC cows showed better reproductive performance by UMB supplementation.