Effects of supplemental protein type on productivity of primiparous beef cows

Effects of supplemental degradable (DIP) and undegradable (UIP) intake prot ein on forage intake, BW change, body condition score (BCS), postpartum int erval to first estrus, conception rate, milk production and composition, se rum metabolites and metabolic hormones, and calf gain were determined using 36 primiparous Gelbvieh x Angus rotationally crossed beef cows. On d 3 pos tpartum, cows (average initial BW = 495 +/- 10 kg and BCS = 5.5 +/- 0.1) we re randomly assigned to one of three dietary supplements (12 cows/treatment ). Date of parturition was evenly distributed across treatment (average spa n of calving date among treatments = 2.4 +/- 2.5 d). Individually fed (d 3 through 120 postpartum) dietary supplements were 0.82 kg of corn and 0.23 k g of soybean meal per day (DIP), the DIP + 0.12 kg of blood meal and 0.13 k g of corn gluten meal per day (DIP + UIP), and 0.82 kg of corn, 0.07 kg of blood meal, and 0.08 kg of corn gluten meal per day in an isonitrogenous re placement of soybean meal (UIP IsoN). Cows had ad libitum access to native grass hay (8.5% CP) and trace-mineralized salt. Total OM intake was greater (P = 0.06) for DIP + UIP than UIP IsoN cows. At 30 d postpartum, DIP + UIP cows produced more milk than UIP IsoN, with DIP being intermediate; howeve r, at 60 d postpartum, DIP + UIP and DIP cows were not different, but both had greater milk production than UIP IsoN (treatment x day interaction; P = 0.08), A treatment x day interaction (P = 0.06) for BCS resulted from DIP + UIP cows having the greatest BCS at 60, 90, and 120 d d postpartum and DI P having greater BCS than UIP IsoN cows only on d 60 postpartum. Serum insu lin concentrations were highest (treatment x day interaction; P = 0.09) for DIP + UIP cows at 30 d postpartum but did not differ among treatment there after. Serum insulin-like growth factor-binding protein (IGFBP)-2 (34 kDa) and -3 (40 and 44 kDa) were greatest (P < 0.0003) for DIP cows. Serum urea- N concentrations were greater (P < 0.01) in DIP + UIP cows than in either D IP or UIP IsoN cows. However, postpartum interval to first estrus, concepti on rate, and calf weaning weights were unaffected (P = 0.35, 0.42, and 0.64 , respectively) by treatment. Although UIP in addition to or in replacement of DIP affected milk production and blood metabolites, the productivity of these primiparous beef cows was not altered. Thus, the type of supplementa l protein does not seem to influence productivity of primiparous beef cows in production systems with conditions similar to our experimental condition s.