Abstract
Thirty-six fall-calving, pluriparous suckled Brahman cows were allotted randomly within sex of calf to receive: (d O= parturition) 2.6 kg corn and 0.60 kg soybean meal (SBM, n=ll), or 2.80 kg corn and 0.40 kg Menhaden fish meal (FM,n=ll) alone or in combination with 200 mg/hd/d of Lasalocid, (SBM+L,n=9 and FM+L,n=8) for 28 d. Cows had free access to rye-ryegrass pasture, Coastal bermudagrass hay, water and minerals. Blood samples were collected weekly fox 90 d after calving for progesterone (P4) to determine interval to corpus luteum (CL) formation. Cows were bled intensively via jugular cannulae on d 28 at 15-min intervals for 420 min, with an additional sample at 245 min, at 30-min intervals through 510 min, then hourly through 690 min to determine LH concentrations. Exogenous GNRH was infused at 240 and 330 min at 10 ng/kg BW and 100 jig/hd, respectively. Serum concentrations of glucose, urea nitrogen, cholesterol and 13,14-dihydro-15-keto-prostaglandin F2a (PGFM) were determined on d 7, 14, 21 and 28. Cow BW and body condition scores (BCS) and calf BW were recorded on d 1, 14 and 28. Protein source or ionophore did not affect (P>.10) LH peak amplitude, time to peak or area under the curve in response to either GNRH challenge. Serum concentration of glucose, urea nitrogen or cholesterol were not affected (P>.10) by treatment. Serum PGFM did not differ (P>.10) on d 14, 21 and 28. There was a tendency (P=.07) for an FM x L interaction on d 7 for PGFM (SBM, FM, SBM+L, FM+L; 2916︢1, 1115︢2, 635︢8 and 1016︢1 pg/ml, respectively) . Calf BW or ADG were not affected (P>.10) by protein source or ionophore. Cow ADG was higher (P=.02) for FM and FM+L relative to SBM and SBM+L cows (.77.︢14 vs .22.︢16 kg, respectively). Change in cow BCS for the 28-d feeding period and interval to functional CL did not differ (P>.10) among treatments. Bypass protein and/or ionophore supplementation failed to enhance postpartum pituitary responsiveness or interval to CL function in pluriparous suckled Brahman cows presumably due to the near optimal body condition of cows at parturition.
Carpena, Mario Luis (1994). Effect of bypass protein and lasalocid on reproductive function in the postpartum Brahman cow. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -C294.