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Key words: Pakistan, Nili-Ravi Buffalo, productive traits, reproductive traits.

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INTRODUCTION

                The livestock sector plays an important position in the economy of Pakistan. This sector has a 11.1 % share in national GDP and 58.9 % share in the agriculture GDP and showed increase of 3.8 % in gross value addition during year 2017-2018. The population of cattle is higher than buffalos in Pakistan (46.1 VS 38.8 million) but contribution of buffalo is more than cow (60.69 VS 36.11 %) towards total milk production of country (Anonymous 2018). Nili-Ravi is the most popular breed of buffaloes which constitutes about 76.7% of the total buffalo population in Pakistan (Garcia et al. 2016).
                Buffalo (Bubalus bubalis) is main dairy animal in Pakistan and second most important dairy species in the world. The performance traits of buffaloes are influenced by several factors. These factors are year and season of birth, year and season of calving and parity. The true genetic merit of the animals may be masked by these factors. The study of these factors affecting performance traits of Nili-Ravi buffaloes is therefore very important for genetic evaluations of animals, developing breeding and general management strategies/programs. Mostly buffaloes are owned by small landless farmers keeping 2-3 animals only. Buffalo population of Pakistan is an important national asset comprising the best dairy breeds of the world, i.e., Nili Ravi and Kundi (Akhtar et al. 2006). Pakistani buffaloes have the ability to produce more than 5000 liter of milk per lactation under well-organized breeding, feeding and health care plan (Bilal et al., 2006). There are many constraints being faced by the dairymen, which can be classified as genetic and environmental (Elemam and Nekheila 2012). Higher age at first calving and long calving interval are not beneficial to the dairy producers. Calving interval, age at maturity, services per conception and birth weight are most important traits to gauge the farm economy. A farm with 15 month calving interval, 1.33 services per conception could be inexpensively advantageous. So it is imperative to assess the different productive and reproductive performance parameters like age at maturity, age at first conception, age at first calving, number of services or A.I per conception, service period, calving interval, lactation length, milk yield and dry period.
                The traits of greater importance in buffalo are fertility, milk production, fat production and productive life span. All these traits are dependent upon the reproductive efficiency of buffaloes. Cady et al. (1983) evaluated performance of Nili-Ravi breed at two institutional herds and reported that herd, year and season of calving and parity affected (P≤0.01) productive and reproductive traits (milk yield, lactation length, days open, calving interval and services per conception). Naqvi (2000) included six military dairy farms to study the effect of parity and season of calving on service period in Nili-Ravi buffalo and reported reduction in length of service period with the increase in parity and significantly lower service period in spring and winter calvers as compared to summer and fall.
                The objective of this study was to assess the parameters of reproductive and productive efficiency like; age at maturity, age at first conception, age at first calving, calving interval, service period, number of services per conception, gestation length, lactation length, dry period, milk yield and breeding efficiency in Nili-Ravi buffaloes maintained at BRI, Pattoki.

MATERIALS AND METHODS

                The parameters of reproductive and productive efficiency of Nili Ravi buffaloes kept at Buffalo Research Institute (BRI), Pattoki, District Kasur, Punjab Pakistan (31° 1' 30.0324'' N and 73° 50' 52.3608'' E.) during 2010-2018 were studied. Data relating to reproductive and productive performance of Nili Ravi buffaloes at BRI were collected from history sheets for year 2010 to 2018.
                During 2005-2006 Buffalo Research Institute, Pattoki District Kasur was established. At that time total of 400 Nili Ravi buffaloes were purchased from local breeders to be maintained at LES, Bhunikey. Nili Ravi buffaloes were kept in loose housing system with ad libitum supply of water. Buffaloes were also fed concentrate ration according to the body requirement based on production status along with green fodder and roughages. The buffalo herd was provided with adequate watering and bathing facilities throughout the year. All the buffaloes were inseminated with frozen thawed semen when they exhibited estrus. Teaser bulls were kept in the herd for detection of estrus in buffaloes. The activity of the teaser bull was observed by the experienced stockman.
                The information was recorded from history / pedigree sheets on following aspects.
                Identification number of buffalo, date of [birth, first insemination, successful service/ A.I, calving and drying], status of calving, total number of calving (lactation) and milk yield per lactation. These data were used to evaluate the factors affecting the following parameters pertaining to reproductive and productive efficiency of buffaloes like; Age at maturity, age at first conception, age at first calving, calving interval, service period, gestation length, service / A.I per conception, lactation length, dry period, 305-day milk yield and breeding efficiency.
                Incomplete lactation record of ≤ 181 days due to culling, abortion, premature birth or diseases, etc were excluded from the data after Chaudhry (1992). The records of the animals with calving interval ˂300 or ˃730 days, gestation length ˂285 or ˃335 days, age at maturity ˃1825 days, age at first conception ˃2190 days, age at first calving ˂900 or ˃2400 days were also excluded (Cady et al. 1983).
                To determine the effect of season on different parameters, the month of year were divided into five seasons as reported by Ali et al. (2011).

1. Spring____February, March and April
2. Dry Summer___May and June
3. Humid Summer___July, Aug and Sep
4. Autumn____October and November
5. Winter_____December and January

                The statistical model ANOVA employed using GLM procedures to analyze the productive and reproductive traits affected by different factors ie. year and season of birth/calving and parity. Significant treatment means were separated through SNK test.
Breeding Efficiency: Breeding efficiency is measure of capacity to reproduce by adult farm stock.  Breeding efficiency or reproductive efficiency of Nili Ravi buffaloes on the basis of calving interval of 400 days had been calculated through formula by Sharma et al. (1980).
    

	[900 + ( n – 1 ) 400 ] × 100
B.E (%) =	---------------------------------------
	AFC (Days) + CI (Days)

Where
n is the number of calvings or parturitions,
400 is the ideal calving interval in buffaloes.

Statistical Analysis: Descriptive statistics was employed in the form of averages and percentages along with appropriate graph type. For the comparison among different treatments ANOVA technique was employed using GLM procedures in SAS software (Version 9.1.). Significant treatment means were separated through SNK test.

RESULTS

Effect of year of birth/calving: In this study, the data analysis of Nili Ravi buffaloes revealed that age at maturity, age at first conception, age at first calving, calving interval, service period,  gestation length, number of service per conception, milk yield, lactation length and dry period (mean ± SE) averaged 1029.59 ± 20.60, 1056.46 ± 20.41, 1417.06 ± 21.66, 490.85 ± 3.82, 227.16 ± 4.98, 312.27 ± 8.03 days, 1.60 ± 0.29 numbers, 1917.07 ± 15.16 liters, 266.94 ± 1.49 and 279.47 ± 5.19 days,  respectively (Table 1). Year of birth have significant (P ≤ 0.05) effect on age at maturity, age at first conception and age at first calving among the buffaloes born during different years (Table 2).
                Year of calving have significant (P ≤ 0.05) effect on calving interval, service period and 305-day milk yield among the buffaloes calving during different years (Table 5). Gestation length, lactation length and dry period were not affected by years (Table 5).
Effect of season of birth/calving:  Season of birth have significant (P ≤ 0.05) effect on age at maturity, age at first conception and age at first calving. The maximum (1216.10 ± 56.02 days) age at maturity was found in buffalo heifers born during winter and the minimum (942.74 ± 31.02 days) was found in autumn born heifers (Table 3). Age at first conception maximum (1221.43 ± 60.57 days) and the minimum (950.07 ± 33.03 days) was found in buffalo heifers born during winter and autumn, respectively (Table 3). Age at first calving maximum (1568.45 ± 64.31 days) was found in buffaloes born during winter season and minimum (1269.58 ± 40.67 days) was found in autumn born heifers (Table 3). Autumn born calvers have plenty of good quality fodder available during their early days of age (3-6 months) which may have helped them to growth rate in later period even in low quality fodder.
                Season of calving have significant (P ≤ 0.05) effect on calving interval, service period, number of services per conception, 305-day milk yield, lactation length and dry period. The average calving interval for winter calvers was the longest (532.43 ± 11.23 days). The shortest (450.94 ± 14.39 days) calving interval was found in Nili Ravi buffaloes calving during humid summer (Table 6). The possible reason may be seasonality of calving in buffaloes as winter calvers wait longer to rebreed as compared to summer calvers. Better management and feeding during winter season can reduce the calving interval. The average service period for spring calvers was the longest (249.95 ± 22.06 days). The shortest (450.94 ± 14.39 days) service period was found in Nili Ravi buffaloes calving during humid summer. The maximum (1.86 ± 0.12) and the minimum (1.41 ± 0.06) services per conception were found in buffaloes calving during dry summer and autumn, respectively (Table 6).
                The season affected 305-day milk yield, the maximum (2352.56 ± 45.67 liters) was found in spring calvers and the minimum (2159.32 ± 19.44 liters) in summer calvers (Table 6). Poor milk yield in summer calvers than spring calvers may be due to high temperature and low availability of fodder. Season of calving influenced lactation length, the maximum (277.77 ± 3.90 days) lactation length was found in autumn calvers and minimum (254.63 ± 6.72 days) in dry summer calvers (Table 6). Lower lactation length is mainly due to insufficiency of fodder in summer season. Season of calving influenced dry period, the maximum (317.06 ± 19.88 days) dry period was found in spring calvers and minimum (234.62 ± 13.20 days) in autumn calvers, (Table 6). The shorter dry period in autumn may be attributed to longer lactation length of buffaloes. The gestation length is less studied trait in buffaloes. Season did not affect it (Table 6).
Effect of Parity: The effect of parity/lactation number on calving interval, service period, number of services per conception, 305-day milk yield and dry period was found to be significant (P ≤ 0.05). The highest (537.52 ± 8.02 days) and the lowest (434.44 ± 36.67 days) calving interval was observed in 1st lactation and 8th lactation, respectively (Table 4) showing gradual decrease from first to later parities. The calving interval has two components i.e. lactation length and dry period. The increased calving interval may be due to high dry period. The lactation length was not affected by parity in this study so dry period decreased along with parity which reduces the calving interval in later ages. The service period, highest (297.84 ± 9.59 days) and the lowest (157.51 ± 28.16 days) was observed in 1st lactation and 7th lactation, respectively (Table 4) showing gradual decrease from first to later parities. First calvers suffer more from stress due to growing, producing and insufficient energy available to them, so there may be difficulty for early conception in first calvers. The service period and gestation length are two component of calving interval. Only service period can be altered to reduce the calving interval. The parity affected number of services per conception. The services per conception were more in earlier parities as compared to the later parities (Table 4).
                Significant effect of parity on 305-day milk yield was observed, the highest (2243.79 ± 34.25 liters) and the lowest (2005.44 ± 101.30 liters) milk yield was observed in 2nd lactation and 8th lactation, respectively (Table 4). Parity affected dry period, the highest (349.90 ± 14.51 days) dry period was found in first calvers, it decreased with increased in parity and reached to the lowest (203.54 ± 33.21 days) in 7th lactation (Table 4). The longer dry period was due to poor lactation yield in first parity buffaloes.
                The effect of parity on gestation length and lactation length found to be non-significant (P > 0.05). The gestation length was not affected by parity (Table 4). Parity did not affect lactation length, the lactation length was highest (277.17 ± 4.88 days) in second calvers, it decreased with increased in parity and reached to the lowest (243.33 ± 13.91 days) in 8th lactation (Table 4).
Breeding Efficiency: The data analysis of 250 Nili Ravi buffaloes revealed that the breeding efficiency is 86.45 % (Table 7).