REPRODUCTIVE PERFORMANCE OF DAIRY COWS IN RELATION TO GENOTYPE, AGE, PARITY, BODY WEIGHT AND BODY CONDITION SCORE AT RAJSHAHI DISTRICT OF BANGLADESH

Received 17 November, 2020 Revised 16 December, 2020 Accepted 28 December, 2020 Online 12 January, 2021 ------------------------


INTRODUCTION
Bangladesh is an agro-based country. Livestock, an integral part of agriculture, plays an important role to keep the rural economy of Bangladesh viable (Sarma and Ahmed, 2011). About 80% of Bangladesh is directly or indirectly involved in agriculture and livestock farming. The contribution of livestock in gross domestic product (GDP) is about 2.51 % in Bangladesh (DLS, 2016). The importance of livestock production has increased in Bangladesh as witnessed by the growth of the sub-sector over the last few decades and the contribution to employment in the country (FAO, 2005). Among the livestock, cattle are most available and versatile component providing a significant contribution to gross domestic, export products and raw materials for industries in relation to existing integrated agricultural farming system in Bangladesh. So, Livestock of Bangladesh is back bone of rural economy. The main goal of dairy farmers is one calf/cow per year. It plays an important role to promote human health and wealth by supplying animal protein in the form of milk and meat. The cattle population in Bangladesh is currently estimated 25.7 million cattle (http://en.banglapedia.org/ index.php? title=Livestock) and among them in Rajshahi district is approximately 5.35 lakh (personal contact with DLS, Rajshahi; 2015). The urban and peri-urban/rural dairy production system has tremendous potential for development and could play a significant role in minimizing the acute shortage of dairy products in urban centers of any country (Mureda and Zeleke, 2008). Reproduction, health and production i.e. calf and milk production are the principal factors affecting the profitability of a dairy herd. Productive performance is determined to a great extent by the milk yield at first lactation and the farm, followed by the age at first calving (Ilieva and Peeva, 2007). In recent years, the dairy industry agenda in many countries has been dominated by health-related problems (Vacek et al., 2007). One prerequisite for effective health management is the accurate knowledge of factors that affect the health status of a cow, such as age, parity, body weight or health history, and of the relationship between health problems and other economically important traits, such as calf, milk production, reproduction, and length of productive life.
The lifetime productivity of cows largely depends on their individual reproductive performance such as age at puberty, age at first calving and calving interval (Ensminger, 1969). The most important measures of reproductive performance of cows are age at first calving, length of calving interval, and length of cow productive life. The current level of reproductive performance in dairy herds is well below the optimum in most countries (Morton, 2003). Reproductive inefficiency in turn, however, affects dairy herd profitability by decreasing milk yield, the number of replacement heifers produced and by increasing culling rate. Healthy pregnant cows are seldom culled from a dairy management control of reproduction and profitability in dairy herd (Grohn and Rajwala, 2000;Santos, 2007). The differences in management (production) systems and environmental conditions under which cattle are maintained could greatly affect the occurrence of reproductive health problems. To ensure food security of our people we need to improve our livestock production first. Low birth rates and reproductive problems are main problems for growth of this sector. Even an apparently healthy animal may not necessarily be in a state of good reproductive health. Very little work has been done to identify the extent of productive and reproductive performance of dairy cows in Rajshahi district, especially situated in low land and hilly areas. Hence, in order to design relevant dairy development strategies and implement context specific interventions for future development of the dairying at study areas, performance evaluation of existing dairying is important. The scientific information regarding the aforementioned parameters helps as a starting point for further development endeavors in dairy enterprise in the nation. Therefore, the present study was undertaken and designed with the objectives of identification of reproductive performance of cows in relation to breed/genotype, age, parity, body weight and body condition available in selected areas of Rajshahi district of Bangladesh.

Study areas and population
The study areas were selected at the Rajshahi district of Bangladesh. A total of 500 cows selected and data were collected directly from the dairy farms owners/farmers/attendant by using questionnaires during the period from September 2013 to December 2014.

Method of data collection
The data were collected from the selected farms by the researcher every three (3) months interval in year. After collecting the questionnaire, preliminary sorting and checking, data were prepared for analysis.

Description of animals
Cross-bred cattle are mainly Holstein Friesian and Sahiwal. Approximately 20% animals are crossed in Bangladesh. Indigenous cattle are found everywhere of the country has no definite characteristics and constitute about 80% of indigenous cattle population of the country. Their coat color varies from red, grey, white, black or a mixture of them in different proportion.

Grouping of experimental animals
To achieve the goal, animals were grouped according to following considering factors: Breed/genotype: The cow was classified broadly in Indigenous or Local and Cross-bred. Selected cows were further group into their genetic composition. These were

Body condition score (BCS)
Effect of body condition on the reproductive performance and disorders were studied. Cows of different body condition were considered for the study and BCS were determined by Nicholson and Butterworth (1986) with some modified technique. The cows were divided in the following groups considering body conditions: Group I : Poor (n = 108) Group II : Medium (n = 120) and Group III : Good (n = 272) Where, Poor: Heads of vertebral process (HVP) were visible, the pad on tuber coxae and ischiatic tuberosity was thicker than that of the under conditioned animal. Medium: Flank and covering well balanced. The gap between thighs was filled up by fat apparently looks lat not round. Good: The gap between thighs was filled up by fat apparently looks fatty and well-muscled. Reproductive traits of cows studied: The following reproductive traits of dairy cows were studied in this study-Age at puberty: The age at which a heifer first shows the estrous signs and behaviors may be defined as age at puberty. It was measured in month (m). Age at first calving: It is defined as the age when a heifer first calving a newborn calf. It was measured in month (m). Post-partum heat period: It is considered as the interval between date of calving and the date of first insemination or first heat show after parturition. It was calculated in days (d). Calving interval: The number of days between two successful calving of the same cows or the period from one calving to the next was termed as calving interval. It was measured in days.

Data management and analysis
The data obtained from the questionnaire was entered into the Microsoft Excel 2007 and transferred to SPSS version, 17.0. Data were statistically analyzed to calculate the effect of reproductive and productive traits of dairy cows. Various standard statistical procedures ((percentages, mean and chi-square test etc.) had been adopted in this study. The mean and standard error of mean for the reproductive traits were calculated with help of a computer package programme (SPSS) version 17.0. Mean of different traits were then tested by using analysis of Variance (ANOVA) by Duncan Multiple Range Test (DMRT). Data were presented as Mean±SE. P<0.05 was considered as significant. Simple ANOVA was performed considering the age of dairy cows and to observe the significant differences among the mean values, Duncan's multiple range test (DMRT) was performed to observer significant differences of reproductive traits in different breed, genotype, age, parity, body weight etc. of dairy cows.

Effects of breeds/genotypes on reproductive performance of dairy cows
The effects of breeds on reproductive performance of dairy cows are summarized in Table 1 and Figure 1. in cross-bred cows. The higher value of service per conception (1.95 ± 0.05) was observed in crossbred cows and the lower value (1.84 ± 0.08) was observed in local breed cows. There was only significant effect (P<0.05) of breed on post-partum heat period of dairy cows, other reproductive traits were not significant.      The effects of age group on reproductive performance of dairy cows The effects of age group on reproductive performance of dairy cows are presented in Table 3 and Figure  4 and 5. The lower value of age at puberty and age at first calving (24.46 ± 0.53 m and 33.62 ± 0.56 m) were observed in 3 to <5 years of age and the higher (

The effects of parity on reproductive performance of dairy cows
To determine the variation of reproductive parameters of dairy cows due to parity effect are presented in Table 4 and Figure 6. The lower value of almost reproductive traits of age at puberty (25.

The effects of body weight on reproductive performance of dairy cows
The effects of body weight on reproductive performance of dairy cows are presented in Table 5 and

The effects of body condition score on reproductive performance of dairy cows
The effects of body condition score on reproductive performance of dairy cows are presented in Table 6    The reproductive performance of dairy cows in Rajshahi district of Bangladesh Infertility problems are usually overlooked by the farmers and reproductive health management is not ensured. These lead to delayed first calving, long calving interval and poor conception rate, imbalance feed management of dairy cows and calves, unavailability of pasture land, inadequate veterinary services, excessive cost of concentrate and unawareness of farmers in herd health management (Shamsuddin et al., 2001) are burning issues, which seriously affects the farm economy. The breeds of animal is genetically determined that affects production and reproduction. In this study, the higher value of all reproductive parameters was observed in local than cross-bred cows except service per conception. There was only significant effect (P<0.05) of breed on post-partum heat period of dairy cows. In local cows, the present value is lower than that of observed by Rahman and Kalita (2015) which were average age at puberty (31.45± 0.87) months, age at first calving (43.60±0.96) months, calving interval (533.63± 0.87) days, post-partum heat period (210.1±0.19) days and service per conception 2.47±0.11. Jabber and Green (1983) stated an extended age at first calving in Bangladesh similar to the present study which was 36 months. Tesfu Kasa (1996) observed post-partum intervals and days open were 110.4 ± 23.5 and 148.8 ± 61.8 days for Zebu and 97.5 ± 25.1 and 157.8 + 55.5 days for cross-bred cow which were lower than the present study. In comparison, Sarder et al. (1997) reported the reverse the present study that Holstein-Friesian cross requiring the longest time (149 days) to onset of post-partum estrus compared with the local ones (119 days). The author also reported the local cows required fewer S/C (1.4) than the cross-bred (1.8), Khan (1990) found the S/C of local and cross-bred cows was 1.3 and 1.4, respectively which were lower than the present study. The findings of present calving interval were lower than the findings of Halim (1992) Sultana (1995) observed that S/C of local (L)), similar to the present study but S/C of Local x Sahiwal and Local x Friesian were lower than the present study. Ghosh (1995) observed the S/C were 1.6 ± 0.2 and 1.7 ± 0.2, for F x L and SL x L, respectively which were also lower than the present findings. Shamsuddin et al. (2001) reported shorter days open in cross-bred Sahiwal cows than that in cross-bred Friesian and local cows which are almost similar to the present findings. Mondal (1998) 6 days, respectively, in Baghabari milk producing area that are higher than the present study. This difference of reproductive traits among the breeds could be due to effects of the differences in management practice, environmental conditions, little rainfall, malnutrition and inappropriate semen handling and insemination techniques (Arthur et al., 1989).
In the present study, we found age group had significant (P<0.05) effect on age at puberty, age at first calving and had no significant (P>0.05) effect on post-partum heat period, service per conception days open and calving interval. Rahman et al. (1995) found the highest age at puberty in heifers 47.3 ± 0.6 months, age at puberty, age at first calving, post-partum heat period and days open in cows were as 43 to 48 months, 56.3 ± 0.5 months, 360.1 ± 0.5 and 360.6 ± 0.4 days, respectively than the present study. This study was more or less similar to the result of Sarder (2001) where he observed age at puberty, age at first calving, service per conception in heifer, onset of post-partum estrous, service per conception in cows, days open and caving intervals were 27.9 months, 38.7 months, 1.68, 139 days, 1.6, 160 days and 438 days, respectively. Spalding et al. (1975) reported slight increase in the fertility of cows up to 3 to 4 years of age and a decline after 4 years of age. They found a marked decline in fertility in the cow over 7 years of age that are agree with the present study. Shamsuddin (1988) observed lower result of the present study of S/C in cows and heifers which were 1.69 and 1.86, respectively. Coleman et al. (1985) reported that reproductive performance had become poor with the advancement of age. Plasse et al. (1972) reported higher value of calving interval 496 days in old cows and 424 days in young cows than the present study. Environmental condition, nutrition, care and management, suckling and post calving infection on female reproductive tracts may also affect this trait. best performance with regard to onset of ovarian cyclicity recorded by (Pereira et al., 1995). In contrast, Darwash et al. (1996) found that the interval from calving to onset of ovarian activity become progressively longer as the number of parities increased. Body size is an important genetic factor in cattle production. Body condition scores are an excellent indicator of reproductive performance. It is an arbitrary scale for estimating the amount of body fat in cows (Wildman et al., 1982). BCS had a good reflection on the reproduction. Good BCS better reproductive performance. This study observed the potential effect of body weight and body condition score on reproduction. In the present study, >300 kg body weight had better reproductive performance compared to other body weight groups and good body condition cows showed the excellent performance than others groups of cows. Haider (2007) observed that cows having a BCS >3.25 were superior in early insemination (82.4±72 days), days open (105.8±72 days), calving interval (397±62.3 days) and S/C (2.1±2.3) than their counterparts. For conception within 115 days BCS 3.25 (55%) and BCS >3.25 (54%) shown better performance than BCS 1.5-<3 (49%), BCS 3 (52%). The author also revealed that the higher the body condition score, the better were the reproductive performance. The present study also in line with (Haider, 2007), Riberior et al. (1997) and (Wright et al., 1992). A local study by Shamsuddin et al. (2001) stated that body condition score 3.5 or more at AI had shorter interval between calving and conception than with cows having ≤2.5 body condition score that are agree with the present study. The higher reproductive performance of good BCS might be due to better hygienic managemental practice of the farm that reduces the incidence of mastitis and other diseases.

CONCLUSIONS
The current investigation showed a relatively lower productive and reproductive performance of dairy cows at compared with different parameters in Rajshahi district of Bangladesh. The situation demands for further study to determine causes, economic impact and appropriate control strategies under different management systems. This study also clearly indicates that lack of awareness about performance of dairy cow farmers and their importance in the economic viability of their farms. Hence more efforts should be extended towards training, increasing awareness of the animal owners/attendant available veterinary services about these problems and their proper management.