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Ultrastructural and immunologic characteristics of mouse x cattle xenogeneic hybridomas originating from bovine leukemia virus-infected cattle.

Nine percent of xenogeneic hybridomas originating from a bovine leukemia virus (BLV)-infected cow secreted monoclonal IgM antibodies with multispecific reactivity. Similar reactivity was evident in some antibodies with an unusually long (> 50 amino acids) third complementarity-determining region of the heavy chain. Electron microscopy of hybridomas demonstrated the presence of c-type virus particles consistent with polymerase chain reaction detection of BLV env gene. Some hybridomas contained dilated rough endoplasmic reticulum and cisternae filled with moderately electron-dense granular substance compatible with plasma cells at presecretory stage. The number of chromosomes in xenogeneic hybridomas corresponded to the sum total of mouse and bovine chromosomes. None of the hybridomas showed polyploidy. The immunochemical and genetic analysis of stable bovine immunoglobulin-secreting xenogeneic hybridomas confirms that BLV infection causes polyclonal B cell activation regardless of antigen specificity. Presence of c-type particles in hybridomas suggests that T cell-derived cytokines are not required for sustained BLV expression.

Animals↗

Effects of alfalfa maturity on energy utilization by cattle and nutrient digestibility by cattle and sheep.

Two comparative slaughter experiments conducted with growing beef steers (300 kg to 480 kg BW) fed alfalfa cubes demonstrated that animal performance diminished as alfalfa matured. In each trial, ADG (empty BW basis) was 10 to 20% greater from pre-bloom than from early-bloom alfalfa. Net energy for maintenance (Mcal/kg) followed a pattern similar to that of ADG, but NEg (Mcal/kg) did not decrease (P greater than .05) as alfalfa maturity increased. Digestion trials with steers and wethers clearly indicated significant reductions in apparent digestibilities of DM, energy, and cell wall fractions as alfalfa matured. Steers fed at 110% of maintenance in digestion Trails 1, 2, and 3 consistently digested cubed alfalfa to a greater extent than wethers fed the same alfalfa ground and pelleted. Digestion coefficients (percentages) for ADF, cellulose, NDF, and crude fiber were 5 to 14% greater for steers fed cubes than for wethers fed pellets. Regression equations calculated from results of three digestion trials indicate that digestible DM % and DE (Mcal/kg) could be predicted from ADF %, but they were 4 to 5% lower for wethers fed pelleted alfalfa than for steers fed cubes.

Animal Feed↗

Phenotypic ranges and relationships among carcass and meat palatability traits for fourteen cattle breeds, and heritabilities and expected progeny differences for Warner-Bratzler shear force in three beef cattle breeds.

Carcass and Warner-Bratzler shear force (WBSF) data from strip loin steaks were obtained from 7,179 progeny of Angus, Brahman, Brangus, Charolais, Gelbvieh, Hereford, Limousin, Maine-Anjou, Red Angus, Salers, Shorthorn, Simbrah, Simmental, and South Devon sires. Trained sensory panel (TSP) evaluations were obtained on 2,320 steaks sampled from contemporary groups of progeny from one to five sires of each breed. Expected progeny differences for marbling and WBSF were developed for 103 Simmental sires from 1,295 progeny, 23 Shorthorn sires from 310 progeny, and 69 Hereford sires from 1,457 progeny. Pooled phenotypic residual correlations, including all progeny, showed that marbling was lowly correlated with WBSF (-0.21) and with TSP overall tenderness (0.18). The residual correlation between WBSF and TSP tenderness was -0.68, whereas residual correlations for progeny sired by the three Bos indicus breeds were only slightly different than for progeny sired by Bos taurus breeds. The phenotypic range of mean WBSF among sires across breeds was 6.27 kg, and the phenotypic range among breed means was 3.93 kg. Heritability estimates for fat thickness, marbling score, WBSF, and TSP tenderness, juiciness, and flavor were 0.19, 0.68, 0.40, 0.37, 0.46, and 0.07, respectively. Ranges in EPD for WBSF and marbling were -0.41 to +0.26 kg and +0.48 to -0.22, respectively, for Simmentals; -0.41 to +0.36 kg and 0.00 to -0.32, respectively, for Shorthorns; and -0.48 to +0.22 kg and +0.40 to -0.24, respectively, for Herefords. More than 20% of steaks were unacceptable in tenderness. Results of this study demonstrated that 1) selection for marbling would result in little improvement in meat tenderness; 2) heritability of marbling, tenderness, and juiciness are high; and 3) sufficient variation exists in WBSF EPD among widely used Simmental, Shorthorn, and Hereford sires to allow for genetic improvement in LM tenderness.

Adipose Tissue↗