title: Effects of lasalocid and intermittent feeding of chlortetracycline on the growth of prepubertal dairy heifers.
abstract: Forty Holstein heifers entered the 12-wk study at approximately 12 wk of age. At enrollment, heifers were blocked by birth date and assigned to 1 of 4 treatments: (1) carrier (30 g; control); (2) lasalocid + carrier (1 mg/kg of body weight; L); (3) chlortetracycline + carrier (22 mg/kg of body weight; CTC); (4) L + CTC + carrier (CTCL). Heifers on CTC and CTCL were provided treatment Monday through Friday and carrier only on Saturday and Sunday. These heifers were provided their respective treatment during wk 1 to 4, 6, and 10; wk 5, 7 to 9, and 11 to 12 heifers were provided the nonmedicated carrier. Heifers were individually fed a total mixed ration with treatments top-dressed at 1200 h daily. Dry matter intake was monitored for each heifer and feed provided was adjusted according to individual intakes. Skeletal measurements were taken weekly and blood samples were obtained every Monday, Wednesday, and Friday. Blood samples were analyzed for thyroxine concentration via radial immunoassay. Heifers supplemented with L had lower average daily gain , overall body weight gain, and trends for lower daily body length gain and overall girth gain compared with CTC heifers, but similar to control and CTCL heifers. Heifers fed L had lower hip height gain and overall hip height gain compared with CTCL heifers, but similar to control and CTC heifers. Heifers fed L had lower overall withers height gain compared with control heifers, but similar to CTC and CTCL heifers. No treatment effect on thyroxine concentrations was observed. These data indicate that L did not increase growth. Results from this experiment indicate that supplementing heifers with L was not beneficial and no benefits to supplementing heifers with CTC or the combination of CTC and L were evident compared with control heifers. Heifers in this study experienced minimal health problems and were regarded to be under low stress levels. Supplementing CTC and L may be beneficial to growing heifers under conditions where disease exposure and stressors are greater.
authors.affiliation: Department of Biological Sciences, University of New Hampshire, Durham, NH 03824, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Cabral
authors.forename: P S
authors.initials: PS
authors.lastname: Erickson
authors.forename: N E
authors.initials: NE
authors.lastname: Guindon
authors.forename: E J
authors.initials: EJ
authors.lastname: Kent
authors.forename: C E
authors.initials: CE
authors.lastname: Chapman
authors.forename: K M
authors.initials: KM
authors.lastname: Aragona
authors.forename: M D
authors.initials: MD
authors.lastname: Cabral
authors.forename: E C
authors.initials: EC
authors.lastname: Massa
authors.forename: N T
authors.initials: NT
authors.lastname: Antaya
authors.forename: C C
authors.initials: CC
authors.lastname: Muir
authors.forename: B
authors.initials: B
authors.lastname: O'Donnell
authors.forename: M E
authors.initials: ME
authors.lastname: Branine
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000981:Antiprotozoal Agents / Q000008:administration & dosage*; D001846:Bone Development / Q000187:drug effects; D002417:Cattle / Q000254:growth & development*; D002751:Chlortetracycline / Q000008:administration & dosage*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004359:Drug Therapy, Combination; D005260:Female; D007832:Lasalocid / Q000008:administration & dosage*; D013974:Thyroxine / Q000097:blood; D015430:Weight Gain / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D013974:Thyroxine; D007832:Lasalocid; D002751:Chlortetracycline