Abstract
The study was conducted with an attempt i) to study the pre- and post-weaning growth, parasitic infestation
and health status of F₁ Brahman graded calves, ii) to assess the post-weaning feed conversion efficiency of Fi
Brahman graded cattle, iii) to evaluate the semen characteristics of F₁ Brahman graded bulls, iv) to evaluate
meat characteristics of F₁ Brahman graded bulls and v) to quantify the scale of genotype-environment
interaction (G x E) in F₁ Brahman graded cattle. The Local cows, kept in Central Cattle Breeding & Dairy Farm,
Savar, Dhaka under intensive management system (on-station) and farmers' house of 7 districts under semiintensive management system (on-farm), were inseminated by Brahman sire semen to produce F₁ Brahman
graded calves. A total of 149 male and 121 female F₁ Brahman graded calves were available at on-station and
210 male and 176 female F₁ Brahman graded calves were available at on-farm for birth weight and a variable
number of calves were available for body weight and daily gain at different ages, calving ease, health status,
body measurements and parasitic infestation over a period from 2010 to 2014. The effect of factors (sex, season
of birth, year of birth and sire of calves) associated with growth traits were analyzed by General Linear Model
procedure of SAS. Fecal samples of 230 calves were examined for parasitic infections. Twelve bull calves
(11.5±1.2 months) divided into three equal groups were fed on three isoprotein and isocaloric diets of varying
concentrate to roughage ratio (C:R) of 75:25, 65:35 and 55:45 to evaluate growth performance and cost/kg gain.
Twelve bulls (20.0±1.5 months) divided into three equal groups were fed on three diets A) 100%Concentrate; В)
50% Concentrate- 50%Urea-Molasses-Straw (UMS) and C) 100%UMS. Three animals from each group were
sacrificed at the end of the trial to evaluate carcass and meat traits. Five F₁ Brahman graded bulls were
ejaculated twice weekly (2x) and 5 bulls four times weekly (4x) for 16 weeks to determine the effect of
ejaculation frequency on semen characteristics and sperm output. Weekly sperm output for each of 10 bulls
ejaculated at 4x was determined for 4 weeks. Data on growth traits from on-station and on-farm were analyzed
to evaluate the effect of genotype by environment interaction in F₁ Brahman graded cattle. The mean birth
weight of calves was 21.2+0.23 and 21.0±0.24 kg, respectively at on-station and on-farm. The mean weight of
calves at 3, 6, 9, 12, 18 and 24 month of age was 60.1±0.77, 104.8±1.46, 143.0±2.06, 178.7±2.84, 239.6±4.68 and
274.0±6.29 kg, respectively at on-station and 52.7±0.84, 83.3±1.55, 112.0±2.25, 142.2±3.12, 211.6±5.66 and
232.6±10.70 kg, respectively at on-farm. From the age of 6 month and above, males were heavier than females
(p<0.05) at on-station, whereas males were heavier than females (p<0.01) in all ages at on-farm. The average
daily gain (ADG) of calves up to 3 month, 4-6, 7-9, 10-12, 13-18 and 19-24 month was 431±7.56, 496±11.1,
419±11.1, 396±14.3, 320±15.3 and 315±12.6 g, respectively at on-station and 354±7.59, 340±7.69, 328±:7.96,
326±8.16, 345±9.43 and 280±10.1 g, respectively at on-farm. Occurrence of assisted calving ranged 23-33%. Calf
diarrhea and skin diseases were predominant. Most of the morphological measurements linearly increased
with the advances of age. The body weight had highest correlation coefficient with the heart girth (r=0.96,
p<0.001). About 85% feacal samples were found positive for parasitic infestations, and mean egg per gram of
feces was 426.2±23.8. The main parasites identified were Balantidium coli (59.1%) and Paramphistomum spp.
(18.3%). The C:R ratio in diet did not affect feed conversion ratio (7.04, 6.94 and 6.76), ADG (981, 958 and 976g)
and feed cost/kg weight gain (Taka 153.8, 147.5 and 136.8). The ADG was 954, 873 and 205g, respectively in
diet A, B and C. Feeding concentrate up to 100% had no significant impacts on ADG or FCR (7.94 and 11.3).
Among carcass traits, hot dressing percentage (59.5% and 55.8% for diet A and B), kidney-pelvic-heart fat,
abdominal fat and back fat thickness were linearly increased (p<0.01) with the increase level of concentrate in
diets, while Longissimus muscle area did not vary among diets. Bulls ejaculated at 4x produced greater (p<0.01)
semen volume (11.4 ml) weekly than that (7.99 ml) of 2x bulls. Average weekly total progressive motile sperm
(TMPS) output for 4x bulls was 1.61 times higher compared to 2x bulls. Scrotal circumference was highly
correlated (p<0.01) with semen volume and TPMS. Significant interaction between sire and environment was
observed in most of the growth traits (p<0.001). Genetic correlations among growth traits between two
environments (on-station and on-farm) showed a decreasing tendency with the increase in age of animal (0.77
at 6 month to 0.57 at 24 month). The ADG of F₁ Brahman graded cattle was highest in 4 to 6 months of age and
decreased linearly with the increase of age in intensive system while ADG was almost similar in all ages in
semi-intensive system. Heart girth as a single predictor can well be used to predict live body weight
Brahman crossbred cattle. The diet consisting of C: R ratio of 55:45 may be used for growing crossbred calves in
feedlot and 50%Concentrate- 50 % (UMS) diet may be used for young bulls in feedlot. Ejaculation of F₁ Brahman
graded breeding bulls at 4x weekly yielded 1.6 times more motile sperm output per week than ejaculation at 2x
weekly. The effect of G × E is large on growth traits for F₁ Brahman graded cattle between two management
systems in Bangladesh.