title: Dietary ractopamine supplementation during the first lactation affects milk composition, piglet growth and sow reproductive performance.
abstract: Excessive mobilization of body reserves during lactation delays the return to reproductive function in weaned primiparous sows. This study tested the hypothesis that supplementing the lactation diets of first-parity sows with ractopamine hydrochloride would reduce maternal weight loss and improve subsequent reproductive performance. Gestating gilts were allocated to one of two treatment groups (n=30 sows/treatment), with one group fed a standard lactation diet (2.5g/Mcal LYS: DE) throughout lactation (CTRL), whereas the treatment group received the standard lactation diet supplemented with 10mg/kg ractopamine hydrochloride (RAC) from d 1 to 13 of lactation and 20mg/kg RAC from d 14 of lactation until artificial insemination (AI). Weaning occurred on d 21 of lactation, with AI occurring at the first post-weaning estrus. Compared to CTRL, RAC supplementation decreased (P<0.05) liveweight loss between d 13 and 20 of lactation (4.3±0.90 versus 1.3±0.96kg), and tended to increase (P=0.06) the number of second litter piglets born alive (9.5±0.52 versus 8.1±0.74). Treatment (RAC versus CTRL) reduced milk protein levels on d 13 and 20 of lactation (P<0.05), and piglet weight gain between d 13 and 20 of lactation (260±0.01 versus 310±0.01g/day, P<0.01). In conclusion, it is evident that dietary RAC altered milk composition and stimulated conservation of maternal body reserves during the third week of lactation, resulting in a beneficial effect on subsequent reproductive performance.
authors.affiliation: School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy SA 5371, Australia. Electronic address: william.vanwettere@adelaide.edu.au.
authors.forename: W H E J
authors.initials: WH
authors.lastname: van Wettere
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4442, New Zealand.
authors.forename: S J
authors.initials: SJ
authors.lastname: Pain
authors.affiliation: Pig and Poultry Production Institute, SA 5371, Australia.
authors.forename: P E
authors.initials: PE
authors.lastname: Hughes
mesh_terms: D000284:Administration, Oral; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D004032:Diet / Q000662:veterinary; D005260:Female; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008892:Milk / Q000737:chemistry*; D010627:Phenethylamines / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects; D013552:Swine / Q000254:growth & development* / Q000502:physiology
chemical_list: D010627:Phenethylamines; C060897:ractopamine
keywords: Lactation; Piglet; Ractopamine; Reproduction; Sow