title: Study of short lactation in Sahiwal cattle at organized farm.
abstract: OBJECTIVE
  The aim was to study the associated factors and extent of short lactations in Sahiwal cattle maintained under organized herd.
  
  
  METHODS
  The present study was conducted on Sahiwal cattle (n=530), utilizing 1724 lactation records with respect to lactation length (LL), spread over a period of 15 years (1997-2011), maintained at Livestock Research Center, National Dairy Research Institute, Karnal. Observations of LL were analyzed by descriptive statistical analysis in order to know the extent of short lactation of animals in the herd. Paternal Half sib method was used to estimate the genetic parameters, i.e., heritability, genetic, and phenotypic correlation. The influence of various non-genetic factors (season of calving, the period of calving, parity, type of calving, and season of drying) on LL was studied by least squares analysis of variance technique.
  
  
  RESULTS
  The least squares means for LL was found to be 215.83±3.08 days. Only 32.48% of total lactation records were fell in the range of 251-350 days of LL, while more than three-fourth (76%) of total observations were failed to reach the standard level of 305 milking days. LL class ranges from 251 to 300 days accommodated maximum number of observations (19.2%). The heritability estimate of LL was 0.22±0.07. Positive correlations were found between LL and service period, LL and 305 or less days milk yield, LL and calving interval; whereas dry period was negatively correlated with the LL. The least squares analysis had shown that LL was significantly (p<0.01) influenced by the period of calving, type of calving, and season of drying. Significantly higher LL (276.50±7.21 days) was found in animals calved in the first period than those calved in other periods. The cows dried during summer season had the shortest LL (188.48±7.68 days) as compared to other seasons.
  
  
  CONCLUSIONS
  Present findings regarding short lactations occurrence may be alarming for the indigenous herd, demanding comprehensive study with the larger data set. Since LL was influenced by various environmental factors suggesting better managerial tools, besides special attention on the milch animals going to dry during the summer season.
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: U S
authors.initials: US
authors.lastname: Narwaria
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: R K
authors.initials: RK
authors.lastname: Mehla
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: K K
authors.initials: KK
authors.lastname: Verma
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: S S
authors.initials: SS
authors.lastname: Lathwal
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: Rajnarayan
authors.initials: R
authors.lastname: Yadav
authors.affiliation: Livestock Production and Management Section, National Dairy Research Institute, Karnal, Haryana - 132 001, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Verma
keywords: Sahiwal cattle; correlation; non-genetic factors; short lactation