RESUMEN
Heifer rearing is one of the largest production expenses for dairy cattle operations, which is one reason milking operations outsource heifer rearing to custom developers. The cost of harvested feedstuffs is a major expense in heifer rearing. A possible way to lower feed costs is to graze dairy heifers, but little research exists on this topic in the mid-south United States. The objectives of this research were to determine the cost of feeding bred dairy heifers grazing native warm-season grasses (NWSG), with and without legumes, and compare the cost of grazing with the cost of rearing heifers using 3 traditional rations. The 3 rations were corn silage with soybean meal, corn silage with dry distillers grain, and a wet distillers grain-based ration. Bred Holstein heifers between 15- and 20-mo-old continuously grazed switchgrass (SG), SG with red clover (SG+RC), a big bluestem and Indiangrass mixture (BBIG), and BBIG with red clover (BBIG+RC) in Tennessee during the summer months. Total grazing days were calculated for each NWSG to determine the average cost/animal per grazing day. The average daily gain (ADG) was calculated for each NWSG to develop 3 harvested feed rations that would result in the same ADG over the same number of grazing day as each NWSG treatment. The average cost/animal per grazing day was lowest for SG ($0.48/animal/grazing d) and highest for BBIG+RC ($1.10/animal/grazing d). For both BBIG and SG, legumes increased the average cost/animal per grazing day because grazing days did not increase enough to account for the additional cost of the legumes. No difference was observed in ADG for heifers grazing BBIG (0.85 kg/d) and BBIG+RC (0.94 kg/d), and no difference was observed in ADG for heifers grazing SG (0.71 kg/d) and SG+RC (0.70 kg/d). However, the ADG for heifers grazing SG and SG+RC was lower than the ADG for heifers grazing either BBIG or BBIG+RC. The average cost/animal per grazing day was lower for all NWSG treatments than the average cost/animal per day for all comparable feed rations at a low, average, and high yardage fee. Results of this study suggest that SG was the most cost-effective NWSG alternative to harvested feeds for bred dairy heifer rearing.
Asunto(s)
Bovinos/fisiología , Industria Lechera/economía , Ensilaje/economía , Animales , Cruzamiento , Costos y Análisis de Costo , Fabaceae , Femenino , Panicum , Tennessee , Trifolium , Zea maysRESUMEN
The phosphorylation of the proteins of heterogeneous nuclear ribonucleoprotein particles has been investigated in HeLa cells. 32Pi labeling of intact cells indicated that, of the six major particle proteins, the most heavily phosphorylated was the C1-protein (Mr = 42,000). This protein, together with C2 (Mr = 44,000), is also phosphorylated by [gamma-32P]ATP in particle extracts and in particles that are purified by sedimentation or exclusion chromatography. The C-proteins, together with their particle-associated kinase, were partially purified from isolated particles following dissociation with micrococcal nuclease. Proteins C1 and C2 co-purify on phosphocellulose chromatography, and their peak overlaps with that of a casein kinase activity. Evidence suggesting that this kinase activity is responsible for C-protein phosphorylation includes 1) the phosphorylation of C-proteins in the fractions where they overlap with the kinase, 2) the phosphorylation of added C-protein by fractions of the casein kinase which lack detectable C-protein, and 3) the similarities in catalytic properties of the casein kinase- and C-protein-phosphorylating activities. The purified kinase activity is cyclic nucleotide and Ca2+ independent. It is stimulated by polyamines, inhibited by heparin, and utilizes either GTP or ATP with high affinity. Serine residues are the major phosphate acceptors. These properties indicate that the kinase is casein kinase II or a closely related enzyme. Moreover, purified casein kinase II from rabbit liver effectively phosphorylates C-protein. These results suggest that C-proteins may be natural substrates for nuclear casein kinase II.
Asunto(s)
Ribonucleoproteína Heterogénea-Nuclear Grupo C , Proteínas Quinasas/metabolismo , Ribonucleoproteínas/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Caseína Quinasas , Centrifugación por Gradiente de Densidad , Cromatografía DEAE-Celulosa , Guanosina Trifosfato/metabolismo , Células HeLa/metabolismo , Heparina/farmacología , Ribonucleoproteínas Nucleares Heterogéneas , Humanos , Hígado/enzimología , Fosforilación , Conejos , Serina/metabolismoRESUMEN
A simple and sensitive assay for S-adenosylmethionine (SAM) synthetase is described which depends on the quantitative separation of the product, [14CH3]S-adenosylmethionine, from the substrate, L-[14CH3]methionine, on a Bio-Rex 70 column. L-Methionine protects the enzyme during preparation of cell extracts by sonic treatment but causes repression of enzyme activity during growth of Candida utilis. The presence of 5 mM methionine in the growth medium repressed SAM synthetase specific activity threefold compared to the specific acitivity of the enzyme isolated from cells grown in unsupplemented medium. Conversely, the presence of methionine in the growth medium resulted in an 80-fold increase in the intracellular concentration of SAM as compared to the Sam accumulated intracellularly in unsupplemented cultures.