Study on persistency of lactation in Holstein Friesian cattle

This study was performed to analyses the persistency of lactation in Holstein Friesian cattle, by analyzing 168 lactation record from the period of 2006-2013 (8 years) at Government Dairy Farm Quetta, Baluchistan. The (PL) persistency of lactation was found lower in first lactation, while highest in 3 lactation in season winter and summer calves. The overall average (PL) was found 85.99±7.30% in winter calves and 83.79±7.27% in summer calves, whereas calving season effect was observed non-significant (p>0.05). The highest (PL) was found in Sire-D followed by SireB Sire_ A and Sire_ C. The overall average (PL) in Holstein Friesian cattle was found 84.74±7.94%. The Sire-wise effect of (PL) was found non-significant. The heritability estimates of (PL) was estimated low (0.094), while the correlation estimates was found higher among lactation length vs milk yield length (0.814), milk yield vs (PL) (0.883) and (PL) vs lactation length (0.747). It was concluded that results of current study for (PL) and Heritability of production traits were low to moderate for heritable traits, which can be improve through the proper environmental and manage mental conditions.


Introduction
Livestock is important and renewable natural resource that plays major role the agricultural economy of Pakistan.Agriculture sector of Pakistan shares 21% to the total (GDP), whereas share of livestock sector is 11.8% to the total values of (GDP).It seems that livestock department is sharing about 55.91% to the total agricultural values of Pakistan [1].The secretion of milk is a vital process of utilizing plant material and converting it into complete food.The milk serve as major source for our routine diet, which are important for nourishment and growth of human body.Baluchistan province has huge number of cattle about i.e. 8 million heads (GOP, 2013), but milk shortage still remain a serious problem due to low production of animals.In this way to fulfil the demand of milk in Baluchistan province high milk producing imported Holstein Frisian strain from Denmark for receiving high level production of milk at the Baluchistan.Lactation persistency is important trait of dairy animals that, is the capability of the cow to produce and maintain higher production of milk at higher level followed by its peak milk yield [2]. Heritability is key genetic parameter, which play major role in the selection of superior animals for future breeding plans.Heritability show the degree of proportion by which the individual genetic difference contributed to individual's own genetic individual differences, which can be observed in its (phenotype or physical individual differences) [2].

Material and methods
The 168 lactations milk record of Holstein Friesian cattle of Government Dairy Farm Quetta, Baluchistan, 6 lactations of each animal were recorded for analysed.Hand milking was used twice a day at the Farm.Animals having normal complete were added and incomplete recorded were discarded form the study.A cow having incomplete lactation record of any week that was estimated by averaging the previous available record, while animal having incomplete lactation record more than 8 week were discarded form the study described of [3].For observing effect of season in (PL) and season divided in 2, season, winter the cows, which has calved in month of October till March) and summer (for the cows calved from April to September) .To observe the effect geneitcal effect on (PL) in Holstein Friesian cattle, cows were divided in to four groups as Group-A sired by Bull No. 542-F, B sired by Bull No. 675-F, C sired by Bull No. 710-F and D sired by Bull No. Laurier-E.T.

Method for analysing of (PL) of Holstein Friesian
The (PL) was analyzed by using the formula as suggested formula given by Ludwick and Peterson (1943).

Method for estimation of (PL) of Holstein Friesian
Heritability estimates of (PL) was performed by the formula as suggested by Becker, (1985).

Results and discussion
Parity-wise all average values of (PL) are presented in Table 1.Average (PL) of Holstein Friesian cattle for winter and summer season calves were 298.91 ± 4.78 * and 297.11 ± 4.427 * respectively.The highest average (PL) was found at 3 lactation, whereas it was found lowest in 6th lactation of winter as well as summer calves.The number of researchers have been reported for (PL) in different breeds.The results of [3-6], are higher and lower than the current study, who reported the (PL) 82.6% in Jersey, 85.22% in Anatolian buffalo, 87.34% in Karan Fries, 87% in Nili-Ravi and 81.62% in Buffalypso breed.Mostly, exotic buffaloes and cows are higher yield animal and are higher persistent than Bos indicus cows.The findings of [7-9] are in agreement with the current study, they reported higher lactation length in 3 rd lactation, while lower in 1 st lactation length and milk yield was found little bit decreased in 3 rd

Table 3
Results