The crossbred dairy cattle (CDC) have been gaining popularity in the tropical countries for their increased milk yield within a short period of time because of heterogenic additive gene action. Hence, we aimed to investigate whether genotype, parity, season and their interactions had any effect on average daily milk yield (ADMY) of the CDC in a dairy farm at Chattogram district, Bangladesh, for a period of 3 years from January 2016 to December 2019. Total 16,425 retrospective lactation records of 150 multiparous Sahiwal × Friesian1 (Sahiwal = 50%, HF = 50%), Local × Friesian1 (Local = 50%, HF = 50%) and Local × Friesian2 (Local = 25%, HF = 75%) CDC from the first to the third parities (50 for each parity) were collected from the farm records. The generalized linear model and principal component analysis identified substantial impacts of genotype, parity, season and their interactions on ADMY of the CDC. The herd level least squared ADMY was 11.22 ± 0.04 kg/days on a 305‐days typical lactation period. The Sahiwal × Friesian1 CDC produced 7.2% and 5.5% more milk than the Local × Friesian1 and Local × Friesian2 respectively. The CDC produced maximum milk in the second parity, which was 7.8% and 0.34% more than the first and third parities. Similarly, the highest ADMY was recorded in the spring, which was 10.8%, 7.3% and 6.6% more than the fall, summer and winter respectively. It was concluded that the Sahiwal × Friesian1 crossbred produced maximum milk in the spring season at the second parity while other determinants remained constant. The changing patterns of milk yield in different genotype, parity and seasons provided scientific evidence for improving feeding strategy to optimize herd level milk yield of CDC in the commercial dairy farms under tropical perspective.

Blood samples from 12 normal cycling and 12 repeat breeding crossbred cows were collected aseptically on different phages of oestrous cycle to elucidate the possible relationship between the trace elements and hormone profile of ovary in normal cycling and repeat breeding cross bred cows. Different trace elements namely Fe, Cu, Zn and Mn were estimated using Atomic Absorption Spectrophometer (AAS) and serum oestradiol 17- and progesterone were estimated using coat-A-count ® RIA kit. Fe, Cu and Mn concentration was observed apparently high and Zn concentration was significantly (P<0.05) high in each phase of collection in normal cycling cows from repeat breeder except mid luteal phase. Oestradiol 17- concentration was significantly (P<0.01) high in normal cycling cows in oestrous and early luteal phase, while no significant variation was observed for progesterone concentration between the same phase of the two groups. A positive significant (P<0.01) correlation was observed between Fe-Zn and Cu-Zn (P<0.05) and oestradiol 17- (P<0.05) in normal cycling cows . In repeat breeding cows Fe and oestradiol 17- and Mn and progresterone was positively significant (P<0.01).

A 35-day trial was conducted to explore if different sources of dietary proteins at varying levels of metabolizable energy had any effect on the average daily feed intake (ADFI), average daily gain (ADG), feed efficiency (FE), carcass characteristics, cardio-pulmonary morphometry, gut morphology, profile of unsaturated fatty acid (UFA), saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA) and humoral immunity of the broiler birds. Total 288 Ross-308 day old male broiler birds were randomly distributed in four dietary treatment groups in a 2×2 factorial arrangement (Two different sources of proteins, i.e., plant and animal with two different levels of metabolizable energy, i.e., low and high). Each treatment had nine replicates containing eight birds per pen. Results indicated that, the supplementation of blended fish protein substantially increased (p<0.001) the final body weight and decreased (p<0.001) the ADFI at 1-14 d, 15-35 d and 1-35 d compared with plant protein. The ADG increased at 1-14 d (p<0.001), 15-35 d (p<0.05) and 1-35 d (p<0.05) and the FE improved (p<0.001) at 1-14 d, 15-35 d and 1-35 d. Similarly, the high energy diet significantly increased (p<0.001) the final body weight and decreased the ADFI at 1-14 d (p<0.001), 15-35 d (p<0.05) and 1-35 d (p<0.05) compared with low energy diet. The ADG increased (p<0.001) and the FE improved at 1-14 d, 15-35 d and 1-35 d. The animal protein increased the thigh weight (p<0.01), the neck weight (p<0.05) and the ratio (p<0.001) of ∑UFA:∑SFA and ∑PUFA:∑MUFA in the breast muscles of the broiler birds. The GLM identified no interaction effect (p>0.05) of energy and protein on the ADFI, ADG, FE, cardio-pulmonary morphometry and humoral immunity of the broiler birds against Newcastle and Infectious Bronchitis diseases. The RV:TV remained within standard range indicating no symptoms of cardiac dysfunctions. It was concluded that the fishmeal supplemented high energy diet improved weight gain, feed efficiency and meat quality of broiler by increasing ∑ω-3 and ∑ω-7 fatty acids as well as the ratio of ∑ω-3:∑ω-6, ∑UFA:∑SFA and ∑PUFA:∑MUFA in the breast muscles of the broiler birds.