Md. Mostofa Kamal

Abundance and seasonal distribution of Penaeus monodon postlarvae in the Sundarbans mangrove, Bangladesh

We record the decline of Penaeus monodon postlarvae (PL) in five rivers of the worlds largest mangrove ecosystem, the Sundarbans, from 1992 to 1999. Shrimp aquaculture in the coastal belt of Bangladesh is dependent on the collection of P. monodon PL from the coastal rivers, and horizontal expansion of shrimp farming has resulted in a severe decline of this wild resource in the Sundarbans. Abundance of P. monodon PL was significantly (P<0.05) reduced in 1999 compared to the previous two-year studies (1992 and 1995) in the rivers. About 12–551 postlarvae of other shrimps, 5–152 finfish postlarvae and 26–1636 other macro-zooplankters are wasted during the collection of a single P. monodon PL. Water temperature and salinity of the river systems are correlated with P. monodon PL abundance. Besides P. monodon PL, inshore fishery of Hilsa ilisha, catfishes and Scylla serrata are also overexploited. The management practices and conservation of fishery resources of Sundarbans are reviewed in the context of its world heritage status.

Altered chromatin condensation of heat-stressed spermatozoa perturbs the dynamics of DNA methylation reprogramming in the paternal genome after in vitro fertilisation in cattle

Shortly after penetration of the oocyte, sperm DNA is actively demethylated, which is required for totipotent zygotic development. Aberrant DNA methylation is thought to be associated with altered chromatin condensation of spermatozoa. The objectives of this study were to investigate the dynamics of DNA methylation reprogramming in the paternal pronucleus and subsequent fertilisation potential of heat-stressed bull spermatozoa having altered chromatin condensation. Hence, bovine zygotes (n=1239) were collected at three different time points (12, 18 and 24h post insemination, hpi), and stained with an antibody against 5-methylcytosine. Fluorescence intensities of paternal and maternal pronuclei were measured by ImageJ. DNA methylation patterns in paternal pronuclei derived from heat-stressed spermatozoa did not differ between time points (P>0.05), whereas control zygotes clearly showed demethylation and de novo methylation at 18 and 24hpi, respectively. Moreover, heat-stressed spermatozoa showed a highly reduced (P<0.01) fertilisation rate compared with non-heat-stressed or normal control spermatozoa (53.7% vs 70.2% or 81.5%, respectively). Our data show that the normal pattern of active DNA demethylation followed by de novo methylation in the paternal pronucleus is perturbed when oocytes are fertilised with heat-stressed spermatozoa, which may be responsible for decreased fertilisation potential.

Age at calving in heifers and level of milk production during gestation in cows are associated with the birth size of Holstein calves

The objective of the present study was to evaluate environmental and dam factors associated with birth size of Holstein calves. Data of 1,594 births from dairy herds in Belgium and Germany were analyzed in a retrospective cross-sectional study. Immediately after birth, the birth weight of the calves was measured. On the next day, the heart girth (HG), withers height, and diagonal length of the dams and calves were measured. Parity, body condition score, gestation length (GL), and age at calving were recorded for all dams. For the cows, days open, lactation length, length of the dry period, and calving interval were also calculated. The magnitude and shape of the lactation that took place during gestation was quantified using the MilkBot model based on monthly milk weights. Using the same procedure, cumulative milk production from conception to drying off (MGEST) was calculated. After descriptive analyses, mixed models were used to identify factors that are significantly associated with the birth weight (most consistent measure of size at birth) of the calves born to both heifers and cows. Of the variables offered to the offspring birth weight model in heifers (n=540), calf sex, season of calving, GL, HG, withers height, diagonal length, and age at calving were significant. The mean birth weight of the calves born to heifers was estimated to be 41.3±1.01kg. In comparison to calves born to old (25.5 to 37.3mo; n=99) heifers, the birth weight was estimated to be 2.75, 3.29, and 2.35kg heavier when the calves were born to very young (20.3 to <22mo; n=98), young (22 to <23.5mo; n=145), and standard aged (23.5 to <25.5mo; n=198) heifers, respectively. Of the variables offered to the offspring birth weight model in cows (n=1,054), calf sex, season of calving, GL, parity, dry period, and MGEST were significant. The mean birth weight of the calves born to cows was estimated to be 44.1±0.99kg. For cows having an identical HG, the birth weight of the calves was estimated to be 0.97 and 1.11kg higher in cows with low (1,400 to <5,400kg) and high (6,500 to <7,200) MGEST, respectively, compared with cows with very high (7,200 to 11,600kg) MGEST. The decisive effects of age at calving in heifers and of high milk production levels during gestation in cows on the birth weight of their calves may provide a basis for developing managerial interventions to improve long-term health and productivity of the offspring.

Evidence for placental compensation in cattle.

Prenatal development is known to be extremely sensitive to maternal and environmental challenges. In this study, we hypothesize that body growth and lactation during gestation in cattle reduce nutrient availability for the pregnant uterus, with consequences for placental development. Fetal membranes of 16 growing heifers and 27 fully grown cows of the Belgian Blue (BB) breed were compared to determine the effect of body growth on placental development. Furthermore, the fetal membranes of 49 lactating Holstein Friesian (HF) cows and 27 HF heifers were compared to study the impact of dam lactation compared to dam body growth. After parturition, calf birth weight and body measurements of dam and calf were recorded, as well as weight of total fetal membranes, cotyledons and intercotyledonary membranes. All cotyledons were individually measured to calculate both the surface of each individual cotyledon and the total cotyledonary surface per placenta. Total cotyledonary surface was unaffected by breed or the breed×parity interaction. Besides a 0.3 kg lower cotyledonary weight (P=0.007), heifer placentas had a smaller total cotyledonary surface compared with placentas of cows (0.48±0.017 v. 0.54±0.014 m2, respectively, P<0.001). Within the BB breed, fetal membranes of heifers had a 1.5 kg lower total weight and 1.0 kg lower intercotyledonary membrane weight (P<0.005) compared with cows. A cotyledon number of only 91±5.4 was found in multiparous BB dams, while growing BB heifers had a higher cotyledon number (126±6.7, P<0.001), but a greater proportion of smaller cotyledons (<40 cm2). Within the HF breed, no parity effect on intercotyledonary membrane weight, cotyledon number and individual cotyledonary surface was found. Placental efficiency (calf weight/total cotyledonary surface) was similar in HF and BB heifers but significantly higher in multiparous BB compared with multiparous HF dams (106.0±20.45 v. 74.3±12.27 kg/m2, respectively, P<0.001). Furthermore, a seasonal effect on placental development was found, with winter and spring placentas having smaller cotyledons than summer and fall placentas (P<0.001). Main findings of the present study are that lactation and maternal growth during gestation entail a comparable nutrient diverting constraint, which might alter placental development. However, results suggest that the placenta is able to manage this situation through two potential compensation mechanisms. In early pregnancy the placenta might cope by establishing a higher number of cotyledons, while in late gestation a compensatory expansion of the cotyledonary surface is suggested to meet the nutrient demand of the fetus.

Comparative efficacy of the synchrony programmes in subestrus crossbred cows at smallholder farms in Bangladesh

The objective was to compare the reproductive efficacy of a Cosynch (GnRH-PGF2α− GnRH + TAI), PG programme (one shot PGF2α ) with artificial insemination (AI) on observed estrus and untreated control (AI on observed estrus) in subestrus (cycling but not detected in estrus by ≥60 days postpartum) crossbred cows at smallholder farms. Ultrasonographic examinations were performed at AI, 7 d after AI and 28 d and 42 d after AI to determine the largest follicle, the new corpus luteum (CL) and to diagnose conception and pregnancy, respectively. Of the 69 enrollments in the estrus detection groups, 78.9% in PG programme and 54.8% in control were detected in estrus during the following two weeks (χ2=4.57; P=0.04). Of the inseminated cows in all groups, 75.7% in Cosynch, 76.7% in PG programme and 82.4% in control were ovulated (χ2=0.31; P=0.86). The size of the largest follicle at AI had a positive correlation with the resultant CL at d 7 (r=0.84, P=0.001). The follicle in cows that subsequently became pregnant was larger (P=0.01) than that in the non-pregnant cows (15.8±2.03 vs. 14.6±2.31), and this was smaller (P=0.001) in cows that experienced late embryonic mortality (12.3±1.03) than that with successfully maintained pregnancy (15.8±2.03) or have not conceived (15.6±2.67). In cows with an expected synchronisation response, the largest follicle size did not differ (P=0.18) between cows that subsequently became pregnant or non-pregnant. The conception rates (Cosynch: 54.1%; PG programme: 63.3%; Control: 64.7%) were not different between the groups (χ2=0.83; P=0.37). The embryonic mortality was 12% in the cows during d 28 until d 42. The overall final pregnancy rate was 41.5% that did not differ (χ2=1.56; P=0.64) between the groups (Cosynch: 45.9%; PG programme: 44.7%; Control: 32.3%). Therefore, selective administration of PGF2α to subestrus cows would be economically advantageous because of a saving in hormone injection costs, and veterinary supervision can lead to an increase in the estrus detection efficiency of the herd personnel.

Investigation on the Gel Forming Ability of Some Under-utilized Marine Fish and Shell Fish Species of Bay of Bengal

Eighteen under-utilized marine fish and shell fish species were studied for their gel forming ability and surimi was prepared from all of the fish species. Difference in proximate composition and muscle pH of raw fish and the surimi products were also studied. Four species, namely, T. thalassinus. S. sihama, L. savala and C. macrolepidotus were found with extremely elastic gel forming ability (AA) and among others eight species were with moderately elastic gel (A). Two species, C. guttatum and M. cordyla were found with very poor gelling quality. Relation between muscle pH and water retention with the gelling quality of the fish has also studied.