Search

The objective of this study was to determine the effect of stockpiled forage type and protein supplementation on VFA production, serum metabolites, and BW in yearling beef heifers. Over 2 yr, spring-born, Angus crossbred yearling beef heifers (n = 42; 305 ± 2.9 kg initial BW) were randomly assigned to 1 of 3 forage pasture types: 1) endophyteinfected tall fescue [TF; Schedonorus arundinaceus (Schreb.) Dumort], 2) a big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L.) combination (BI), or 3) switchgrass (SG; Panicum virgatum L.). Each pasture was then randomly assigned to receive either 1 of 2 isonitrogenous CP treatments: 1) 0.68 kg·heifer-1·d-1 of dried distiller's grains with solubles (DDGS; 28% CP and 88% TDN) or 2) 0.22 kg·heifer-1·d-1 of blood meal and fish meal (BF; 72.5% CP and 69.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Treatments were initiated in January and terminated in April in both years of the study. Body weights and blood samples were collected approximately every 28 d from initiation of grazing until the end of the trial. Heifer BW change from January to February and overall BW change were greater (P < 0.01) for TF heifers. However, BW change from March to April was not different (P = 0.84) among forage types. Supplement type did not influence (P ≥ 0.13) BW or BW change from January to February and from January to April; however, heifers fed DDGS had greater (P = 0.03) BW gain from March to April. Heifer BW change from February to March exhibited (P < 0.05) a forage type × supplement interaction, with BF-fed heifers gaining more BW on BI pastures than DDGSfed heifers. Serum glucose concentrations, ruminal acetate, and the acetate:propionate ratio were greater (P ≤ 0.04) for SG heifers. However, circulating serum NEFA and urea N (SUN) concentrations were not different (P ≥ 0.85) among forage types. Serum glucose and NEFA concentrations were not influenced (P ≥ 0.61) by supplement type. Circulating SUN concentrations were greater (P < 0.01) in BF-supplemented heifers. Ruminal acetate tended to be greater (P = 0.09) and butyrate concentrations were greater (P < 0.01) for BF-supplemented heifers. The acetate:propionate ratio was not influenced (P = 0.15) by supplement type. These results suggest that a compensatory gain period prior to breeding would be needed for these native warm-season species to be a viable opportunity for growing and developing replacement heifers in the southeastern United States. [ABSTRACT FROM AUTHOR]

The objective was to determine the effect of stockpiled forage type and protein supplementation on VFA production, serum metabolites, and heifer BW. Over 2 yr, spring-born, crossbred heifers (n = 45) were stratified by BW at weaning and randomly assigned to 1 of 3 forage treatments: 1) endophyte-infected tall fescue (TF; Festuca arundinacea), 2) big bluestem (Andropogon gerardi Vitman) and indiangrass (Sorghastrum nutans L.) combination (BI), or 3) switchgrass (SG; Panicum virgatum L.). Forage treatments were then randomly assigned to receive 1 of 2 supplement types: 1) 0.68 kg·heifer-1·d-1 of dried distiller's grains with solubles (DDGS; 28% CP, 74% RUP, and 88% TDN) or 2) 0.22 kg·heifer-1·d-1 of blood meal and fish meal (BF; 72.5% CP, 67.5% RUP, and 69.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Treatments were initiated every year in January and terminated in April at the onset of a 60-d breeding season. Body weights and serum samples were collected approximately every 28 d from initiation of grazing until breeding. Serum glucose concentrations were greater (P = 0.05) for heifers grazing SG. Circulating NEFA concentrations were greater (P = 0.04) in TF heifers. Serum urea N (SUN) was not influenced (P = 0.37) by forage type. Ruminal acetate concentration and acetate:propionate ratio were greater (P = 0.04) in heifers grazing SG pastures. Heifer BW change from January to February and overall BW change were greater (P < 0.01) for TF heifers. However, BW change from March to April was not different (P = 0.84) among forage types. Serum glucose and SUN concentrations exhibited (P < 0.05) supplement type × sampling time interactions. Ruminal acetate tended to be greater (P = 0.09) and butyrate concentrations were greater (P < 0.01) for BF-supplemented heifers. The acetate:propionate ratio was not influenced (P = 0.15) by supplement type. Supplement type did not influence (P > 0.13) BW or BW change from January to February and January to April; however, heifers fed DDGS gained (P = 0.03) more BW from March to April. Heifer BW change from February to March exhibited (P < 0.05) a forage type × supplement interaction with BF heifers gaining more BW on BI pastures than DDGS heifers. Overall, developing heifers on low-quality native forages initially delayed BW gain; however, heifers seemed to quickly adapt to the lower-quality forage, resulting in similar BW gains in March and April. [ABSTRACT FROM AUTHOR]