title: Interactions of tallow and hay particle size on yield and composition of milk from lactating Holstein cows.
abstract: An 18-wk lactation study was conducted to determine whether the effects of tallow on the lactation performance of dairy cows were influenced by particle size of hay in the ration. A total mixed ration containing 50% concentrate, 25% corn silage, and 25% alfalfa hay (dry matter basis) was fed to Holstein cows. Four total mixed rations were developed based on differences in the percentage of tallow in the concentrate and particle size of alfalfa hay: 1) 0% tallow, long-cut hay; 2) 0% tallow, short-cut hay; 3) 5% tallow, long-cut hay; and 4) 5% tallow, short-cut hay. Ration had no effect on dry matter intake, body weight gain or change in body condition score. Tallow increased milk and milk protein yields but reduced milk protein concentration. However, the effects of tallow on milk and milk protein yields were the same, regardless of hay length in the ration. A tendency for an interaction of tallow and hay particle size was detected for fat-corrected milk (FCM) because tallow increased FCM more when hay was short. Ration had no effect on volatile fatty acids in ruminal samples collected via a stomach tube. In this study, the effects of tallow on milk yield and composition from Holstein cows were the same, regardless of hay particle size in the ration. The tendency for tallow to increase FCM more when hay was short suggests at least a limited role of forage particle size in the determination of how fat supplements in dairy rations affect lactation performance.
authors.affiliation: Department of Animal and Veterinary Sciences, Clemson University, SC 29634, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Jenkins
authors.forename: J A
authors.initials: JA
authors.lastname: Bertrand
authors.forename: W C
authors.initials: WC
authors.lastname: Bridges
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004043:Dietary Fiber / Q000378:metabolism; D004063:Digestion; D005223:Fats; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005260:Female; D007774:Lactation; D008055:Lipids / Q000032:analysis; D000455:Medicago sativa; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis; D010316:Particle Size; D012417:Rumen / Q000378:metabolism; D012820:Silage; D003313:Zea mays
chemical_list: D004043:Dietary Fiber; D005223:Fats; D005232:Fatty Acids, Volatile; D008055:Lipids; D008894:Milk Proteins; C013698:tallow