title: Identifying factors affecting age at first semen freezing and age at first semen use in Sahiwal bulls.
abstract: OBJECTIVE
  The objective of the study was to evaluate the effects of non-genetic factors on reproduction traits viz. age at first semen freezing and age at first semen use of breeding bulls in Sahiwal bulls by fitting least-squares analysis.
  
  
  METHODS
  The information on reproduction traits of 43 Sahiwal breeding bulls belonging to 8 sets of Sahiwal breeding program at Indian Council of Agricultural Research-National Dairy Research Institute (ICAR-NDRI), Karnal (Haryana), India during 27 years (1987-2013) were analyzed using fixed linear model. The information was collected from AI records, reproduction sheets, and bull AI register maintained at different sections of Institute viz. record room of Dairy Cattle Breeding Division (DCB), Cattle Yard, Artificial Breeding Research Centre, ICAR-NDRI, Karnal.
  
  
  RESULTS
  The average age at first semen freezing and age at first semen use of Sahiwal breeding bulls was estimated as 3.17±0.01 years and 5.35±0.01 years, with the coefficient of variation 18.93% and 20%, respectively. The overall least-squares mean for age at first semen freezing and age at first semen use was estimated as 3.14±0.09 years and 5.25±0.02 years, respectively, in Sahiwal breeding bulls. Period of freezing/use had significant effects on reproductive traits (p<0.01). Season had no significant effect on any of the traits considered in this study.
  
  
  CONCLUSIONS
  It can be concluded that management inputs such as nutrition, breeding, and optimum environment should be taken care of to optimize age at first semen freezing and age at first semen use for better utilization of superior germplasm.
authors.affiliation: Division of Animal Genetics, Indian Council of Agricultural Research, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India.
authors.forename: B C
authors.initials: BC
authors.lastname: Naha
authors.affiliation: Dairy Cattle Breeding Division, Indian Council of Agricultural Research, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Chakravarty
authors.affiliation: Dairy Cattle Breeding Division, Indian Council of Agricultural Research, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: M A
authors.initials: MA
authors.lastname: Mir
authors.affiliation: Dairy Cattle Breeding Division, Indian Council of Agricultural Research, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: V
authors.initials: V
authors.lastname: Jamuna
authors.affiliation: Dairy Cattle Breeding Division, Indian Council of Agricultural Research, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: A P
authors.initials: AP
authors.lastname: Singh
authors.affiliation: Dairy Cattle Breeding Division, Indian Council of Agricultural Research, National Dairy Research Institute, Karnal, Haryana, India.
authors.forename: D
authors.initials: D
authors.lastname: Maher
keywords: Sahiwal breeding bull; age at first semen freezing; age at first semen use; non-genetic factors